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The Caton-Deschamps Index (CDI) is a measurement used to evaluate patella alta based on true lateral radiographs; however, no prior study has investigated how altering the degree of radiograph aberrancy affects CDI measurement. The primary and secondary purpose of this study was to evaluate effects of rotational radiographic changes on patella height measurements and compare these findings to MRI measurements, respectively. Five cadaver knees ( n  = 5) were utilized in this study. True lateral radiographs were obtained for each specimen by using a fluoroscopic C-arm machine. The C-arm was then altered in two planes (axial and coronal) in both the clockwise and counterclockwise direction and radiographs were taken at 5, 10, and 15 degrees of error from the true lateral position. A CDI measurement of each specimen was performed based on sagittal magnetic resonance imaging (MRI) slices and compared with radiographic CDI measurements. Three orthopedic surgeons measured the CDI for each radiograph and MRI performed. Interrater reliability and changes in CDI were analyzed. Clinically significant difference in CDI was set to 0.1. Mean intraclass correlation coefficient was high (≥0.7) at true lateral and at all varying degrees of error. When performing a pairwise comparison of mean CDI from the true lateral position to increasing degrees of error, statistically significant differences were observed in the axial plane. The largest change in CDI measurements was seen with rotational malposition in the axial plane and counterclockwise direction. No statistically significant differences in mean CDI were observed in the coronal plane. The change in CDI from the true lateral position reached an absolute maximum of at least 0.1 in all four scenarios at each tested degree of error. This study found that aberrant radiographic rotation in the axial plane resulted in a significantly different mean CDI measurement when compared with true lateral radiographs. All degrees of error in both directions and in both planes could have a clinically significant effect on CDI (≥0.1). Our findings confirm the importance of a perfect true lateral radiograph when measuring patella height., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: Patella-shaped disorder has been considered as a predisposing factor for patella instability. But the influence of early patella reduction for patellar development remains unclear. This study aimed to evaluate whether early operation in patella instability could improve patella morphology in growing rabbits., Methods: Fifty rabbits (1-month-old) were included in the study. The control group underwent no surgical procedures. The two experimental groups (reduction group and non-reduced group), underwent medial soft tissue restraint release surgery. The reduction group, rabbits underwent the medial soft tissue sutura surgery in order to stabilize the patella 2 months after release surgery. The non-reduced group, rabbits did not undergo suture surgery. Computed Tomography (CT) scans analysis in two experimental endpoints (2, 5 months after release surgery) were selected to evaluate the transverse diameter, thickness, Wiberg index and Wiberg angle. Gross observation was conducted to assess morphological changes of the patella., Results: CT scans showed significant difference in the mean transverse diameter, Wiberg angle between the two experimental groups and the control group 2 months after release surgery. 5 months after release surgery, the indices of patella were found no statistically difference in the reduction group versus the control group. However, the transverse diameter, Wiberg angle in the non-reduced group were significantly differences than that in the reduction group (P < 0.05). Gross observation showed a flattened articular surface of the patella in the non-reduced group., Conclusions: The results indicated that patella instability may lead to patella-shaped disorder, showing a flattened morphology. Early patella reduction can improve the patella morphology in growing rabbits., (© 2023. The Author(s).)

Mediolateral patella displacement is of interest for diagnostics and clinically relevant research questions. Apart from manual testing, no standardized method is currently available. Proper quantification of patella mobility is necessary to better understand pathologies at the patellofemoral joint. Patella mobility was assessed in 25 healthy individuals using a Patellostabilometer, a new prototype instrument for quantification of the mediolateral patella displacement. The participants underwent measurements of the mediolateral displacement three times using the Patellostabilometer. A maximal force of 10 N was applied for patella movement. Additionally, leg length and circumference of the knee, upper- and lower-leg were measured. Lateral patella displacement of 18.27 ± 3.76 mm (range 15.85-20.64 mm, interquartile range (IQR) of 4.79) was measured. The medial patella displacement showed 24.47 ± 6.59 mm (range 19.29-29.76 mm, IQR of 10.47). The test-retest measurement error was 2.32 ± 1.76 mm (IQR of 2.38 mm), with five outliers. There was greater test-retest variability between the measurements of the medial displacement compared to the lateral one. The test-retest variability reached 7% of the patella displacement. Other parameters provided no significant correlations. Based on the natural patellofemoral mobility, a precise and clinically relevant quantification of patella mobility is allowed.

Pediatric tibial tubercle fractures are uncommon injuries that most often occur in adolescent men. Patients will typically present with anterior knee pain with or without patella alta. This case report describes a tibial tubercle fracture in a 13-year-old man misidentified as an inferior pole patella sleeve fracture on physical examination and preoperative radiographs. The tubercle reduction was secured with cannulated screws while injury to the patellar tendon periosteal sleeve was repaired with suture anchors. This case highlights the utility of advanced imaging when the etiology of extensor mechanism disruption is unclear. Furthermore, it is imperative to set expectations with parents and guardians that the full extent of the injury may only be confirmed under direct visualization in the operating room because of the complexity of such injuries., (Copyright © 2023 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons.)

Background: There is currently a lack of evidence to identify the optimal patellar implant design in total knee arthroplasty (TKA). The aim of this study was to assess clinical, intraoperative, radiographic, and scintigraphic differences between inlay (IN), onlay round (OR), and onlay oval (OO) patellar implants., Methods: A parallel-group, double-blinded, randomized trial compared IN, OR, and OO patellar implants using the same posterior-stabilized TKA prosthesis for each. Patient outcomes were prospectively followed for a minimum of 2 years, with survivorship outcomes followed for a mean of 5 years. The primary outcome was the between-group differences in the mean Kujala score change from preoperatively to 2 years postoperatively. The secondary outcomes included differences in other knee-specific and general health outcomes, intraoperative characteristics, radiographic parameters, patellar vascularity, and implant survivorship., Results: A total of 121 participants (40 in the IN group, 41 in OR group, 40 in the OO group) were allocated to 1 of 3 implant designs. At 2 years postoperatively, there were no significant differences in Kujala score changes between groups (p = 0.7; Kruskal-Wallis test). Compared with the IN group, the OR group showed greater improvements in Knee injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living and in KOOS Quality of Life compared with the OO group. However, the OO design exhibited better bone coverage and lower lateral facetectomy rates compared with the IN and OR designs. The IN group had more lateral contact compared with the OO group (p = 0.02; Fisher exact test), but the overall value for lateral contact was not significant (p = 0.09; chi-square test). There were no differences in postoperative scintigraphic vascularity (p = 0.8; chi-square test). There was 1 revision for infection at 3 years postoperatively in the OO group, and no revision in the other groups., Conclusions: Patellar design did not influence patellofemoral outcomes or survivorship. However, OR implants showed improvements in some secondary patient-reported outcome measures, and OO implants exhibited superior bone coverage and improvements in several intraoperative, radiographic, and scintigraphic outcomes. These findings, combined with superior long-term implant survivorship from previous studies, add support for the use of onlay designs in TKA., Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/H318)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Objective: The aim of this radiological study was to compare several relevant modified and newly applied patella height indices (PHI) in navigated primary total knee arthroplasty (TKA) to determine intra- and interobserver reliability in order to give a recommendation for clinical application in measuring patella height (PH) in primary TKA., Materials and Methods: A retrospective data analysis assessing different PHI (modified Insall-Salvati index (mISI), Caton-Deschamps index (mCDI), Blackburne-Peel index (mBPI), Plateau-Patella Angle (mPPA); Miura-Kawaramura index (MKI), Knee-Triangular index (KTI)) on lateral knee radiographs was performed by two blinded observers using the same software three months pre- and postoperatively. Concordance correlation coefficient and Pearson's correlation respectively were determined for intra- and interobserver rating as well as a categorization according to Landis and Koch and Cohen., Results: A total of 337/291 patients of a 5-year period could be analyzed pre-/postoperatively. Excellent postoperative interrater results according to the categorization of Landis and Koch were achieved for the mBPI (Pearson 0.98) > mPPA (0.90) > KTI (0.86), good results for the MKI (0.79) and the mCDI (0.69), and moderate results for the mISI (0.52) with a predominantly strong Cohen correlation in almost all cases. Preoperatively, the mBPI and the KTI were the best interrated PHI. No PH changes could be found postoperatively for the mISI, KTI, MKI, and mPPA., Conclusion: The mBPI, the mPPA, and the KTI can be recommended for PH assessment in TKA. The mPPA might be the easiest one to use in a daily clinical set-up., (© 2022. The Author(s).)

The positional relationship between patellar and femoral articular surfaces may vary according to the degree of posterior rotation of the tibial condyle, which may influence the patellar configuration. We hypothesized that the configuration of the patella has a rhomboid transformation similar to that of the tibial condyle. This cohort study included 313 patients with knee pain who underwent lateral-view knee digital radiography. The length of the long axis, short axis of the patella, and patellar tendon length of the patellofemoral joint were measured. The patella axis ratio (length of long/short axis) as patellar configuration and Insall-Salvati ratio were calculated. Correlations between the configuration of the tibial condyle and the three length parameters and the Insall-Salvati ratio were assessed. Posterior rotation and the rhomboid transformation of the tibial condyle were positively correlated with the length of the long axis of the patella and negatively correlated with the Insall-Salvati ratio. The more the tibial articular surface shifted posteriorly due to posterior rotation and rhomboid transformation of the tibial condyle, the longer the long axis of the patella was, and the smaller the Insall-Salvati ratio was. The long axis of the patella became longer due to rhomboid transformation, similar to the tibial condyle., (© 2022. The Author(s).)

Rationale: Osteochondral fracture (OCF) in weight-bearing area of lateral femoral condyle (LFC) is a rare combined injury caused by patellar dislocation., Patient Concerns: A 15-year-old female student accidentally sprained her right knee while participating in sports activities. The patient felt pain in his right knee and limited movement. After hospitalization, the patients underwent computed tomography scan and magnetic resonance examination., Diagnosis: According to the imaging results, patellar dislocation combined with OCF of LFC was considered in diagnosis., Interventions: Through the lateral parapatellar approach, we reduced the osteochondral mass and bundled it with absorbable sutures of anchors., Outcomes: The functional and radiographic outcome were satisfactory at 18 months after operation., Lessons: Anchor absorbable suture bridge fixation for this kind of OCF is not only effective, but also economical., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: There are certain risk factors responsible for patella instability that should be identified before choosing the most appropriate treatment., Methods: We evaluated 83 skeletally immature patients who, after two or more patellar dislocation episodes, underwent surgical treatment to address the condition of patellar instability. Each patient was evaluated for patellar instability risk factors using the Balcarek patellar instability severity score. Evaluation of patellar instability included knee MRI to systematically identify anatomical risk factors. The preoperative and postoperative clinical evaluation included the modified Cincinnati score and the Kujala score. The Roux-Goldthwait technique combined with lateral retinaculum release and the advancement of the vastus medialis oblique (VMO) was performed on all knees., Results: The mean patient age at the time of surgery was 12.2 ± 1.59 years (range 8-14 years). The average follow-up was 4.72 ± 1.37 (range 3-8) years. Trochlear dysplasia (decreased trochlear depth), the most common anatomical risk factor, was identified in 71 knees (83.5%). The modified Cincinnati score increased from 58.46 ± 8.75 (range 49-76) points to 94.07 ± 2.88 (range 88-98) postoperatively. The mean Kujala scores increased from 58.51 ± 8.94 (range 49-76) points to 93.66 ± 2.65 (range 87-98) postoperatively. The two-tailed P value was less than 0.0001. The patients were followed until their skeletal maturation, without reporting any incidents of patella dislocation, except one., Conclusion: The Roux-Goldthwait technique combined with lateral retinaculum release, and the advancement of VMO, can restore patellar tracking and can decrease the probability of another dislocation. It was an effective treatment in skeletally immature patients who had two or more episodes of patellar dislocation., Level of Evidence: IV., (© 2021. Istituto Ortopedico Rizzoli.)

Patella fractures are rare injuries, accounting for 0.5 - 1.5% of all fractures, but they can lead to severe functional limitations if they do not heal properly. In addition to a prompt diagnosis, surgical treatment is usually necessary for multi-fragment fractures. The goals of every treatment are a biomechanically stable joint as well as a congruent restoration of the retropatellar joint surface. These results often remain a challenge, especially in multiple fragment fractures. The surgical treatment strategies have steadily evolved from tension band and screw osteosyntheses in combination with wire cerclages. Currently, angular stable plate systems are increasingly being used. This article gives an overview of the fracture anatomy, the classification and diagnosis of patella fractures and the currently used surgical treatment options., Competing Interests: Erklärung zu finanziellen Interessen Forschungsförderung erhalten: nein; Honorar/geldwerten Vorteil für Referententätigkeit erhalten: nein; Bezahlter Berater/interner Schulungsreferent/Gehaltsempfänger: nein; Patent/Geschäftsanteile/Aktien (Autor/Partner, Ehepartner, Kinder) an im Bereich der Medizin aktiven Firma: nein; Patent/Geschäftsanteile/Aktien (Autor/Partner, Ehepartner, Kinder) an zu Sponsoren dieser Fortbildung bzw. durch die Fortbildung in ihren Geschäftsinteressen berührten Firma: nein. Erklärung zu nichtfinanziellen Interessen Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)

Background: The relationships between the morphometric structure of the patellofemoral joint, patella type and chondromalacia patella are still a matter of debate., Objective: To identify the prevalence of chondromalacia patella by determining the patella type and making patellofemoral morphometric measurements., Design and Setting: Retrospective cohort study in an orthopedics and traumatology clinic in Turkey, conducted between June 2017 and November 2019., Methods: This study involved 562 knees of 522 patients with anterior knee pain (246 males and 316 females; mean age 46.59 years). The patients were grouped according to presence of chondromalacia patella (group I) or absence of chondromalacia patella (group II). The patella type, lateral trochlear inclination, medial trochlear inclination, trochlear angle, sulcus angle, patellar tilt and Insall-Salvati index were assessed. Group comparisons were made using chi-square tests or Student t tests. The r value was used to determine the magnitude of relationships between pairs of variables., Results: Among the 562 knees evaluated, 265 (50.71%) presented type I patella, 195 (36.7%) type II, 100 (12.3%) type III and 2 (0.3%) type IV. Group I consisted of 448 knees and group II consisted of 114 knees. Significant differences were found between the groups in terms of age, gender, patella type and lateral inclination angles (P &lt; 0.05)., Conclusion: Detecting the patella type and making lateral inclination measurements in patients with anterior knee pain are of great importance for diagnosing suspected chondromalacia patella, particularly in the early degenerative period.

The degree of cartilage degeneration assessed intraoperatively may not be sufficient as a criterion for patellar resurfacing in total knee arthroplasty (TKA). However, single-photon emission tomography/computed tomography (SPECT/CT) is useful for detecting osteoarthritic involvement deeper in the subchondral bone. The purpose of the study was to determine whether SPECT/CT reflected the cartilage lesion underneath the patella in patients with end-stage osteoarthritis (OA) and whether clinical outcomes after TKA without patellar resurfacing differed according to the severity of patellofemoral (PF) OA determined by visual assessment and SPECT/CT findings. This study included 206 knees which underwent TKA. The degree of cartilage degeneration was graded intraoperatively according to the International Cartilage Repair Society grading system. Subjects were classified into low and high uptake groups according to the degree of bone tracer uptake (BTU) on SPECT/CT in the PF joint. The Feller's patella score and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were assessed preoperatively and postoperative 1 and 2 years. The increased BTU in the PF joint was associated with more severe degenerative cartilage changes underneath the patella ( p  < 0.001). The risk for the presence of denudated cartilage was greater in the high uptake group (odds ratio = 5.89). There was no association between clinical outcomes and visual grading of patellar cartilage degeneration or the degree of BTU on SPECT/CT. The visual assessment of the degree of cartilage degeneration underneath the patella and preoperative SPECT/CT evaluation of the PF joint were not predictive of clinical outcome after TKA with unresurfaced patella., Competing Interests: None declared., (Thieme. All rights reserved.)

Introduction: Several surgical techniques have been proposed for the treatment of patellar fractures. The aim of this study is to compare the clinical efficacy and complication rates of treatment using suture tape circumferential cerclage (STCC) and metallic wire circumferential cerclage (MWCC) for the surgical treatment of displaced transverse patellar fractures (TPFs)., Hypothesis: The hypothesis is that the use of the suture tape would be associated with a significantly lower rate of re-operation than metallic cerclage but no differences in other clinical outcomes., Patients and Methods: A retrospective comparative analysis of the clinical outcomes of consecutive patients undergoing fixation of TPFs with either MWCC or STCC between January 2017 and December 2018 was undertaken. All patients underwent evaluation with standardised radiographs at one, three, and six months after surgery to determine rates of union, non-union, loss of fixation and malunion. All patients underwent a final clinical evaluation at 18 months postoperatively to evaluate clinical scores and complications., Results: A total of 26 patients were included in the study. Thirteen patients underwent STCC and 13 underwent MWCC. There were no complications in the STCC group. In the MWCC group, one patient underwent hardware removal at 2 months postoperatively due to painful prominence. There was no significant difference in re-operation rates between the STCC and MWCC groups (p=1). There were no cases of non-union, malunion or loss of fixation throughout the series. At the final clinical follow-up of 18months, there were no significant differences in KSS, KOOS or Böstman scores between the groups., Conclusion: No significant differences were identified when comparing the clinical outcomes of fixation of AO/OTA 34C1/2 fractures with suture tape or metallic cerclage fixation concerning re-operation rates, union rates, loss of fixation and functional outcome measures. These results cannot be extrapolated to more complex injury patterns or surgical techniques in which prominence of implanted material is more likely., Level of Evidence: III., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Purpose: To investigate the change of the cross-sectional area (CSA) of vastus medialis oblique (VMO) in patients with recurrent patellar dislocation (RPD) treated by tibial tubercle transfer combined with medial patellofemoral ligament (MPFL) reconstruction by imaging methods, and to guide clinical treatment and rehabilitation., Methods: From October 2015 to March 2022, 23 patients with RPD who underwent tibial tubercle transfer combined with MPFL reconstruction were retrospectively enrolled. All patients were assessed by CT in the supine position with the knee fully extended and the quadriceps relaxed. The CSA of VMO and the ratio of CSA of VMO to body weight (CSA/BW) were measured at the upper pole of the patella, 5 mm above the upper pole of the patella and 5 mm below the upper pole of patella. The differences of measured parameters were compared before surgery and at follow-up, including CSA of VMO and CSA/BW. Test level α = 0.05., Results: The tibial tubercle-trochlear groove (TT-TG) distance was significantly reduced at follow-up compared with that before surgery (27.91 ± 1.95 mm vs 12.33 ± 1.07 mm, P < 0.001). The CSA of VMO was significantly increased at follow-up compared with that before surgery at 5 mm below the upper pole of the patella (473.06 ± 106.32 mm 2 vs 562.97 ± 157.90 mm 2 , P < 0.001), at the upper pole of the patella (641.23 ± 188.45 mm 2 vs 700.23 ± 177.55 mm 2 , P = 0.029), and at 5 mm above the upper pole of the patella (788.25 ± 238.62 mm 2 vs 849.79 ± 180.84 mm 2 , P = 0.018). The CSA/BW was significantly increased at follow-up compared with that before surgery at 5 mm below the upper pole of the patella (7.83 ± 2.52 mm 2 /kg vs 9.22 ± 3.54 mm 2 /kg, P < 0.001), at the upper pole of the patella (10.48 ± 3.62 mm 2 /kg vs 11.42 ± 4.14 mm 2 /kg, P = 0.020), and at 5 mm above the upper pole of the patella (12.86 ± 4.65 mm 2 /kg vs 13.68 ± 3.86 mm 2 /kg, P = 0.017)., Conclusion: After tibial tubercle transfer combined with MPFL reconstruction, CSA of VMO increased in patients with RPD, which will help to enhance patellar stability and reduce recurrence., (© 2022. The Author(s).)

Purpose: Patellar instability is a frequent clinical situation in adolescents and young adults. One of the most important risk factors of this condition is trochlea dysplasia. Few studies have analyzed the role of patellar dysplasia. The objective of this paper was to assess the correlation between trochlear and patellar dysplasia. The hypothesis is that patellar dysplasia increased in parallel with femoral trochlear dysplasia., Methods: The study included patients operated on at least one knee for patellar instability between 2008 and 2020. For these patients, symptomatic knees (operated or not) were included if they had lateral and patellofemoral skyline radiographs. Two blinded observers categorized each trochlear and patellar dysplasia according to the Dejour and Wiberg classifications. Patellar height was also measured by applying the Caton-Deschamps index., Results: A total of 100 patients were selected, involving 149 symptomatic knees. A significant correlation between trochlear and patellar dysplasia types was found (0.82; p < 0.0001). Dejour types B and C of trochlear dysplasia were significantly more often associated with patellar dysplasia than Dejour type A (p = 0.033 and p = 0.019, respectively). Moreover, severe Wiberg 3 patellar dysplasia was significantly associated with type D Dejour trochlear dysplasia than with the sum of all other Dejour types taken together (p < 0.0001)., Conclusion: This study confirms a linear correlation between the severity of patellar and trochlear dysplasia. Further studies are needed to evaluate the place of patellar dysplasia in the therapeutic strategy., Level of Evidence: Level IV., (© 2022. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Introduction: Semi-extended tibial nailing techniques include the extra-articular technique (EAT) and the patellar eversion technique (PET). These approaches differ regarding the exposure of the patellar retinaculum and the size of the surgical field. This study compared the postoperative alignment and intramedullary nailing entry points between the EAT and PET for tibial fractures., Patients and Methods: A total of 54 patients (aged ≥18 years) who had undergone intramedullary nailing by the EAT (n = 29) or PET (n = 25) for a tibial shaft fracture were evaluated. The intramedullary nailing entry point and postoperative alignment were measured, and the 1-year postoperative follow-up results were compared., Results: For the EAT and PET, the intramedullary nailing entry point was located at a mean distance of 4.04 mm medial to the optimal entry point and 0.27 mm lateral to the optimal entry point, respectively. The mean angular deformation observed in anteroposterior radiographs following surgery using the EAT and PET were 2.49° and 0.32° valgus, respectively., Conclusion: The intramedullary nailing entry point affected postoperative alignment. Intramedullary nailing may result in malalignment while performing the EAT due to the interference of the patella at the time of nailing., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Purpose: To evaluate the inter-observer and inter-method reliability for patellar height measurements between conventional radiographs (CR) and magnetic resonance imaging (MRI) using one or two slices., Methods: This was a reliability study, with 60 patients divided in two groups: 30 patients with patellar instability (patella group) and 30 patients with anterior cruciate ligament or meniscus injury (control group). CR and MRI were evaluated by two independent observers. Insall-Salvati index (IS) and Caton-Deschamps index (CD) were measured using three different methods: CR, one-slice MRI or two-slice MRI. Intra-class correlation coefficients (ICC) were calculated for inter-observer reliability and inter-method reliability. Bland-Altman agreement was also calculated., Results: The inter-observer reliability was very good for the IS with ICCs of 0.93, 0.84 and 0.82, for the CR, one-slice MRI and two-slice MRI, respectively. Similarly, for the CD the ICCs were good, 0.76, 0.80 and 0.75 for the CR, one-slice MRI and two-slice MRI, respectively. No differences were found between the patella and the control group. The inter-method analysis results were: ICCs for IS (0.83, 0.86, 0.93) and CD (0.72, 0.82, 0.83), for the comparisons of CR/one-slice MR, CR/two-slice MRI and one-slice MRI/two-slice MRI, respectively. The Bland-Altman mean differences showed an 8% and a 7% increase on IS values with one-slice MRI and two-slice MRI compared to CR results, while the increase was of 9% and 1% in CD for the respective comparisons with CR., Conclusion: MRI can overestimate patellar height compared to CR, as much as an 8% increase in Insall-Salvati values when using one- or two-slice MRI measurements, and up to a 9% increase in Caton-Deschamps value when using the one-slice MRI method. It is recommended to use the CR as the preferred method when measuring patellar height., Level of Evidence: III., (© 2022. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Purpose: After intramedullary nailing of tibial shaft fractures using an infrapatellar/transtendinous approach, several patients suffer anterior knee pain. We suspect that the approach is associated with soft tissue scars and the development of a postoperative patella baja. The goal of the study is to investigate whether the development of patella baja is associated with worse subjective outcomes., Methods: We retrospectively analyzed all patients in our orthopedic trauma department between 2011 and 2020 who underwent tibial fracture fixation via intramedullary nailing via an infrapatellar/transtendinous approach. Pre- and postoperative lateral knee x-rays were evaluated by measurement of the Insall-Salvati Index, and nail tip position. All patients were asked to answer the self-assessment Kujala questionnaire and Lysholm questionnaire., Results: We included 78 patients (age: 44 ± 18 years) with a minimum follow-up of 12 months. Mean follow up was 59 ± 25 months. We included 50 male and 28 female patients. Patella baja detected by Insall-Salvati Index could be observed in 8 (10.3%) patients. Patients with patella baja showed significant worse function measured by the Kujala score 54 ± 18 vs. 80 ± 14 (p < 0.01). Likewise, Lysholm score did show significant differences between both groups (60 ± 24 vs. 86 ± 11; p < 0.01). Nail tip position was not associated with worse subjective function., Conclusions: Patella baja in patients after tibial intramedullary nailing via an infrapatellar/transtendinous approach, is associated with worse subjective function and increased pain., (© 2021. The Author(s).)

Purpose: To investigate clinical and magnetic resonance (MR) imaging results of patients undergoing patella stabilization with either open flake refixation (oFR) or autologous chondrocyte implantation (ACI) and concomitant soft tissue patella stabilization after sustaining primary, acute patella dislocation with confirmed chondral and/or osteochondral flake fractures. It was hypothesized that refixation will lead to better results than ACI at mid-term follow-up., Methods: A retrospective chart review was conducted to identify all patients undergoing oFR or ACI after sustaining (osteo-)chondral flake fractures and concomitant soft tissue patella stabilization following primary, acute patella dislocation between 01/2012 and 09/2018 at the author's institution. Patients were excluded if they were aged < 14 years or > 30 and had previous knee surgeries at the index knee. Clinical outcomes were assessed using the Tegner activity score, Kujala score, subjective IKDC score, and the KOOS score at a minimum follow-up of 24 months postoperatively. MR images were assessed using the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) 2.0 knee score. Thirty patients were included in the study, with 16 patients assorted to the oFR group and 14 patients to the ACI group (Follow-up 81%)., Results: Demographic data did not show significant group differences (oFR: 6 females, 10 males; age 26.9 ± 5.6 years, FU: 57 months (27-97 months); ACI: 9 females, 5 males; age 25.5 ± 4.9 years, FU: 51 months (29-91 months); n.s.). Defect location was similar in both groups (oFR: 12 × patella/4 × lateral femoral condyle; ACI: 12/2; n.s.). Both groups showed excellent clinical outcomes, with no statistically significant difference between both the groups (oFR group vs. ACI group: Tegner: 5.1 ± 1.8 vs. 5.1 ± 1.4; Kujala: 86.1 ± 12.6 vs. 84.9 ± 9.1; IKDC: 83.8 ± 15.0 vs. 83.6 ± 11.3; KOOS: 83.3 ± 14.0 vs. 83.6 ± 12.0; n.s.). One patient in each group suffered a patella re-dislocation and needed revision surgery. The MOCART 2.0 score showed good results for the oFR group (68.2 ± 11.1) and the ACI group (61.1 ± 16.9) while no significant differences were noted between both the groups. The inter-rater reliability was excellent (0.847)., Conclusion: Open refixation of (osteo-)chondral fragments in patients after sustaining acute patella dislocation with (osteo)-chondral flake fractures led to good clinical and radiological results at a minimum follow of 24 months, showing that it is a good surgical option in the treatment algorithm. However, if open refixation is not possible, ACI may be an excellent fallback option in these younger patients with equally good clinical and radiological outcomes, but requiring a second minimally invasive surgery., Level of Evidence: III., (© 2022. The Author(s).)

Background: The aim of this study is to determine whether distalization of the tibial tubercle is necessary for patients with recurrent patellar dislocation accompanied by patella alta and increased TT-TG., Methods: In this retrospective study, all 70 patients (70 knees) with recurrent patellar dislocation accompanied by TT-TG distance ≥20 mm and patella alta (CD-I ≥ 1.4) were surgically treated using MPFLR combined with medialization of the tibial tubercle or medialization and distalization of the tibial tubercle in the Third Hospital of Hebei Medical University between 2017 and 2019. 33 patients(33 knees) received MPFLR combined with medialization of the tibial tubercle (MPFLR + TTm group), 37 patients(37 knees) received MPFLR combined with medialization and distalization of the tibial tubercle (MPFLR + TTm-d group). Evaluation indicators included knee injury and osteoarthritis prognostic score (KOOS) and Kujala score evaluation, congruence angle (CA), patellar tilt angle (PTA), TT-TG distance, Blackburne-Peel index (BP-I), Caton-Deschamps index (CD-I)., Results: A total of 70 knees (70 patients) with a mean follow-up time of 32 ± 6 months were evaluated in the present study. The postoperative, the PTA, CA, CD-I, BP-I, and TT-TG distance significantly improved in the two groups (P < 0.05), and there was no statistical difference between the two groups (>0.05). The KOOS and Kujala scores of the two groups at the last follow-up were significantly higher than the preoperative scores (P < 0.05), and there was no statistical difference between the two groups (P>0.05). No complications were noted in either group., Conclusion: For patients with recurrent patellar dislocation accompanied by increased TT-TG distance and patella alta, distalization is not needed and medialization is sufficient even in the presence of patella alta., (© 2022. The Author(s).)

Background: The three-dimensional (3D) transfer of tibial tuberosity has been reported to improve patellofemoral congruity and showed good clinical outcomes during the short follow-up, however, little is known about whether the patellar position and clinical outcomes are preserved at longer follow-ups and the risk factors for poor clinical outcomes., Hypothesis: We hypothesized that patellar position and clinical outcomes would be preserved and the predisposing factors were associated with poor clinical outcomes after the 3D transfer of tibial tuberosity., Patients and Methods: Thirty-nine patients, with a mean age of 27.9 (15-52) years, who underwent the 3D transfer of the tibial tuberosity were enrolled. Patellar position was evaluated using the Caton-Deschamps index and patellar tilt. Clinical outcomes were evaluated with Lysholm and Kujala scores pre- and postoperatively. Age, body mass index (BMI), radiographic measurements, and range of motion (ROM) were compared between the poor group (defined as <80 points on Kujala score) and the good group (≥80 points). The mean follow-up period was 54.1 (36-100) months., Results: Patellar position decreased from 1.32 (1.21-1.53) preoperatively to 0.99 (0.84-1.07) at the final follow-up, according to the Caton-Deschamps index (p < 0.01). The mean patellar tilt decreased from 26.0° (21-40°) to 15.1° (5-28°) (p < 0.01). Kujala and Lysholm scales improved from 59.1 to 54.2 to 90.1 and 91.8 at final follow-up, respectively (p < 0.01). Increased BMI, lower femorotibial angle, limited ROM, and poor preoperative clinical outcomes were the predicting factors for poor postoperative clinical outcomes (p < 0.05)., Conclusion: The 3D transfer for patellar instability with patella alta preserved the patellar position and clinical outcomes for at least 3 years. Predisposing factors that may potentially affect postoperative clinical outcomes of the 3D transfer of tibial tuberosity include an increased BMI, valgus knee, limited ROM, and poor preoperative clinical outcomes., Competing Interests: Declaration of competing interest None., (Copyright © 2021. Published by Elsevier B.V.)

This case report describes the successful fixation of a periprosthetic patellar fracture in an 89-year-old female patient after total knee arthroplasty (TKA) and cemented retropatellar component. Fixation was performed by use of a fixed-angle plate combined with cerclage, under preservation of the firmly fixed retropatellar prosthetic component. No complications were observed postoperatively. Radiologic controls confirmed bone healing. A range of movement of the knee joint of 0/5/110° was achieved by the last clinical examination 5 years postoperatively. The patient was free of pain and had an age-appropriate mobility. The use of fixed-angle plates in the treatment of type II periprosthetic patellar fractures according to Ortiguera and Berry can provide stable fixation while preserving the retropatellar prosthetic component. Additional augmentation by cerclage, tapes or traction screws is recommended in cases of poor bone stock or severe osteoporosis., (© 2021. Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Objective: To compare the functional and alignment outcomes of intramedullary nail fixation using suprapatellar and infrapatellar approaches in treating distal tibial fractures., Methods: In this retrospective study, 132 patients with distal tibial fractures (87 men, 45 women) ranging in age from 20 to 66 years were treated with intramedullary nails using the suprapatellar (69 patients) or infrapatellar (63 patients) approach. The radiographic alignment outcomes and ankle function were compared between the two groups. Multivariate logistic regression analyses were performed to determine which variety influenced ankle functional scores and whether the suprapatellar approach intervention demonstrated a protective effect., Results: The mean follow-up time was 14.22 ± 2.31 months. The mean sagittal section angle of the fracture in the suprapatellar and infrapatellar approach groups was 3.20° ± 1.20° and 5.31° ± 1.23°, respectively (P < 0.001). The mean coronal section angle was 3.51° ± 0.89° and 5.42° ± 1.05°, respectively (P < 0.001). Three patients (4.3%) in the suprapatellar approach group and 15 patients (23.8%) in the infrapatellar approach group had poor fracture reduction (P < 0.001). The mean hind foot functional score and ankle pain score were 95.91 ± 4.70 and 35.91 ± 4.70 points, respectively, in the suprapatellar approach group and 85.20 ± 5.61 and 25.20 ± 5.61 points, respectively, in the infrapatellar approach group (P < 0.001 for both). In the comparison of ankle function, the multivariate logistic regression analyses demonstrated that the odds ratio in the suprapatellar approach group was about 7 times that in the infrapatellar approach group (odds ratio, 7.574; 95% confidence interval, 2.148-28.740; P = 0.002). Of the variants measured, the statistically significant risk factors for poor ankle function were AO type A3 (P = 0.016) and diabetes mellitus (P = 0.006). Sex and the operation interval were not statistically significant risk factors for poor ankle function., Conclusion: Intramedullary nailing using the suprapatellar approach facilitates simple fracture reduction, excellent postoperative fracture alignment, and few complications, giving it obvious advantages over the conventional infrapatellar approach. Additionally, the suprapatellar approach is a prognostic factor associated with postoperative ankle joint function., (© 2022 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Introduction: Stress fracture of the patella is an overuse disorder that occurs in the lower extremity. Surgery may be considered if conservative treatment does not work or if a quicker and more reliable return to sports is expected. Surgery is usually performed under fluoroscopic guidance based on the premise that the proper placement of the internal fixation material can be determined on radiographic images., Patient Concerns: A 16-year-old female basketball player gradually became aware of pain in the anterior aspect of her right knee during basketball, without any particular history of trauma. A computed tomography scan revealed a small bone fragment on the lateral side of the distal end of the patella., Diagnosis: Stress fracture of the patella., Interventions: Since it was difficult to determine the exact location of the bone fragment on radiographs, the surgery was performed under ultrasound guidance rather than fluoroscopy. While checking the bone fragment with ultrasound images, insertion of the guide pin, drilling, and screw fixation were performed under ultrasound guidance., Outcomes: Postoperative computed tomography showed accurate screw insertion into the bone fragment. Two months after surgery, bony fusion was confirmed, and the patient returned to her preinjury level of basketball., Conclusion: Ultrasound-guided screw fixation was useful in this case in which internal fixation of fractures is difficult under fluoroscopic guidance., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Patellofemoral instability is one of the most common pathologies of the knee joint. The planning and implementation of patella-stabilizing operations are very variable. With regard to the operative measures, the preoperative planning is of decisive importance, especially with regard to the complexity of underlying pathologies., Objectives: The aim of this study was to depict the current healthcare reality in relation to planning and implementation of patella stabilizing operations in Germany. Furthermore, it was to be ascertained whether automated analysis options would facilitate the planning and implementation of surgical procedures (in primary and revision cases)., Materials and Methods: An online survey with 16 questions was collected by email among all active members of the German Society of Orthopedic and Trauma Surgery. 7974 members were surveyed; 393 responses could then be analyzed., Results: MPFL-reconstruction (89.8%) is the most frequently performed procedure, followed by tibial tubercle transfers (64.9%), osteotomies (51.2%), and trochleoplasty (19.9%). The choice of surgical approach is mainly based on a combination of clinical and radiological findings (90.3%). MRI imaging (81.2%), standard X‑ray images (77.4%), and full leg images (76.6%) are mainly used for operative treatment decisions. 59.3% of the respondents would appreciate better preoperative planning and 59.0% would implement more radiologically detectable parameters in their individual preoperative planning if these were automatically available., Conclusions: The findings of this survey among members of the DGOU identify the MPFL-reconstruction as the central operative approach in the treatment of patellofemoral instabilities, whereas MRI imaging is the diagnostic tool of choice. Future establishment of automated software-based analysis methods could allow a large number of surgeons to expand the radiological parameters taken into account when planning patella-stabilizing operations., (© 2022. The Author(s).)

Objective: The exact mechanism of patellofemoral instability has not been clearly clarified. The current study aims to explore the correlation between the tibial tuberosity-trochlear groove (TT-TG) distance and other patellar stability parameters., Methods: A total of 60 individuals aged 18 to 40 years who underwent knee computed tomography (CT) examination between September 2014 and December 2017 were retrospectively recruited. Five reference sites were selected on the femoral trochlear articular surface in every CT image. The TT-TG distance and the trochlear groove angles (TGA) at the five reference sites were measured. The patellar ligament length (PLL), patellar length (PL), medial patellar retinaculum length (MPRL) and lateral patellar retinaculum length (LPRL) were quantitatively analyzed. The TT-TG distances on different knee sides or in different sexes were compared. The relationships between the TT-TG distance and TGA, PLL/PL, MPRL, and LPRL were analyzed by Spearman's method. Comparison analysis among patellar stability parameters was analyzed using ANOVA or two-tailed Student's t test., Results: Variance analysis revealed no significant differences in the TT-TG distances among the five positions of the femoral trochlea (F = 0.67, P = 0.62) but significant differences among the five femoral TGAs at the five reference sites (F = 380.37, P < 0.01). Notably, an increasing tendency of the TT-TG distance was observed in the sexes (male, range 16.61-19.68 mm; female, range 14.37-17.38 mm) and knee sides (left knee, range 14.37-18.43 mm; right knee, range 15.80-19.68 mm). The TGA at site 1 of the femoral trochlear cartilage was the largest, with an angle of 151.97° ± 10.4°, and then gradually decreased to the smallest when the cartilage disappeared at site 5, with an angle of 92.05° ± 10.01°. Interestingly, there was a positive relationship between the TT-TG distance at site 1 and TGA in the right knees of males (r = 0.490, P = 0.033) as well as LPRL in the left knees of males (r = -0.420; P = 0.046). There were no correlations between the TT-TG distance and the other patellar stability parameters, including TGA, PLL/PL, MPRL, and LPRL., Conclusion: Among young and middle-aged populations, patella surgeries should be carefully determined based on the comprehensive consideration of these patellar stability parameters rather than the TT-TG distance alone. Differences in sex and knee side should also be considered., (© 2022 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Summary: A 46-year-old man presents with left knee bucking 3 months after open reduction and internal fixation of a left knee inferior pole patella fracture. Radiograph and magnetic resonance imaging evaluation reveal displacement and comminution of the inferior pole of the patella confirming failure of the repair. The purpose of this video is to demonstrate the surgical management of failed inferior pole patella fractures using suture anchors for repair of the patella tendon and augmentation with ipsilateral autologous hamstring grafts., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Objective: To investigate the changes in patellar morphology following soft tissue surgical correction of recurrent patellar dislocation in children with low-grade trochlear dysplasia., Methods: The prospective cohort study was performed between November 2007 and December 2012. Finally, 25 cases, with the mean age of 8.4 years (range from 7 to 10 years), were admitted to the study. All patients were diagnosed as bilateral recurrent patellar dislocation associated with femoral trochlear dysplasia. The knee that suffered injury or was dislocated was treated with medial patellar retinacular plasty (surgery group). The contralateral knee, which served as a control, was treated conservatively (conservative group). Axial CT scans were undertaken in all patients to assess the patellar morphological characteristics., Results: The mean follow-up time was 60.8 months (range 48 to 75 months). Preoperatively, there were no statistically significant differences between the patellar morphology in the two groups (P > 0.05). Many radiological parameters of patellar morphology were significantly different between the two groups at the final follow-up, including well-known parameters, such as the mean patellar width (surgery group, 40.58 mm [SD 1.26]; conservative group, 36.41 mm [SD 1.17]; P < 0.05), the mean patellar thickness (surgery group, 11.59 mm [SD 0.74]; conservative group, 9.38 mm [SD 0.56]; P < 0.05) and the mean Wiberg index (surgery group, 0.54 [SD 0.06]; conservative group, 0.72 [SD 0.08]; P < 0.05). There are also little-known parameters, such as the ratio of length of lateral patella to medial patella (surgery group, 1.26 [SD 0.17]; conservative group, 1.69 [SD 0.21]; P < 0.05), which was a measurement of facet asymmetry. However, the Wiberg angle was not significantly different between the two groups (surgery group, 128.63° [SD 9.05]; conservative group, 125.47° [SD 13.96°]; P > 0.05) at the final follow-up. No complications were found., Conclusions: The patellar morphology can be significantly improved by early soft tissue surgical correction in children with patellar instability associated with low-grade femoral trochlear dysplasia., (© 2022 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Objective: To measure the position of patellar high point and the shape of the osteotomy surface, and to analyze their relationship, distribution, and gender differences., Methods: A total of 127 patients who needed anterior cruciate ligament reconstruction or meniscus repair due to trauma between September 2020 and September 2021 were selected as the research subjects. There were 71 males and 56 females, with an average age of 30.5 years (range, 19-43 years). There were significant differences in height and body weight between male and female patients ( P <0.05), but no significant difference in age and body mass index ( P >0.05). The three-dimensional model of the patella was reconstructed in Mimics software based on the CT images of the knee joint, and then imported into Geomagic Studio software for virtual osteotomy of the patella. The horizontal axis and vertical axis of the osteotomy surface represented the total width (W) and total height (H) of the osteotomy surface, respectively. Then the osteotomy surface was divided into four quadrants with the two axes: inner proximal, inner distal, outer proximal, and outer distal, and the inner width (W1), proximal height (H1), outer width (W2), and distal height (H2) were measured. The midpoint of the patellar ridge was selected as the patellar high point, and the point projected onto the osteotomy surface was defined as the optimal point for patellar prosthesis positioning (OPPP). The distances of OPPP on the horizontal axis (L1) and vertical axis (L2) relative to the center of the osteotomy surface were measured and L1/W1 and L2/H1 were also calculated; the quadrant distribution of OPPP was recorded. The patients were grouped according to gender, and the morphological parameters of the osteotomy surface (W, W1, W2, H, H1, H2) and the parameters related to the position of the OPPP (L1, L2, L1/W1, L2/H1) were analyzed between groups., Results: The width and height of each osteotomy surface of the patella in males were significantly larger than those in females ( P <0.05). As for the relationship between OPPP and osteotomy surface, the L1 of both male and female patients was 1-7 mm, and there was no significant difference in the distribution between the two groups ( χ 2 =8.068, P =0.149); L1/W1 in both male and female patients was mainly 1/10-3/10. The L2 of male patients was 0-5 mm, and that of female patients was -1-4 mm; the difference in distribution between the two groups was significant ( χ 2 =15.500, P =0.006); L2/H1 in both male and female patients was mainly 0-1/5. The OPPP of male patients was mainly distributed in the inner proximal (98.59%) and outer proximal (1.41%) quadrants, while the female patients were distributed in the inner proximal (91.07%), inner distal (7.14%), and outer proximal (1.79%) quadrants. There was significant difference in the OPPP quadrant distribution between the two groups ( χ 2 =5.186, P =0.036)., Conclusion: The OPPP points are widely distributed but mainly concentrated on around 1/5 of the medial patella surface and around 1/10 of the superior patella surface. A small portion of females' OPPP were inferior while all males' OPPP were superior to the center of the patella.

Objectives: To identify risk factors of acute articular cartilage lesions of the patella and lateral femoral condyle in acute first-time lateral patellar dislocation (LPD)., Methods: Magnetic resonance images were prospectively analyzed in 115 patients in an acute first-time LPD. Factors included gender, skeletal maturity, trochlear dysplasia, patellar height, and tibial tuberosity-trochlear groove (TT-TG) distance. Binary logistic regression analysis was carried out to identify the independent risk factors for the incidence of acute articular cartilage lesions of the patella and lateral femoral condyle in acute first-time LPD., Results: The incidence of acute articular cartilage lesion of the patella and lateral femoral condyle were 46.1% and 27% in acute first-time LPD, respectively. Univariate analysis revealed significantly higher incidence rate of acute articular cartilage lesion of the patella in male (P = 0.027), skeletally mature (P = 0.035), normal TT-TG distance (P = 0.043) and normal femoral trochlea (P = 0.031). Risk factors for the incidence of acute articular cartilage lesion of the patella were skeletally mature (odds ratio (OR): 2.324), normal TT-TG distance (OR: 2.824) and normal femoral trochlea (OR: 3.835). Univariate analysis revealed significantly higher incidence rate of acute articular cartilage lesion of the lateral femoral condyle in skeletally mature (P = 0.027) and normal femoral trochlea (P = 0.031). Risk factor for the incidence of acute articular cartilage lesion of the lateral femoral condyle was normal femoral trochlea (OR: 3.347)., Conclusions: For patients in acute first-time LPD, compared with other parameters, the normal femoral trochlea, normal TT-TG distance and skeletally mature are independent risk factors for the incidence of acute articular cartilage lesion of the patella, and the normal femoral trochlea is an independent risk factor for the incidence of acute articular cartilage lesion of the lateral femoral condyle., Competing Interests: Declaration of Competing Interest The authors declared no conflict of interest. No external funding was received in the study., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: Several anatomic risk factors have been identified in the pathogenesis of patellofemoral instability. The literature is sparce regarding how these anatomic risk factors change during skeletal growth and development., Hypothesis: The anatomic risk factors associated with patellar instability change significantly during skeletal growth and maturation with different patterns in male versus female patients., Study Design: Cross-sectional study; Level of evidence, 3., Methods: Magnetic resonance imaging data from 240 unique, asymptomatic knees (7-18 years of age; 50% female) were used to measure patellar height (Caton-Deschamps index), lateral patellar tilt angle, trochlear height, trochlear groove depth, trochlear sulcus angle, and tibial tubercle-trochlear groove (TT-TG) distance. Linear regression was used to test the associations between age and anatomic findings. Two-way analysis of variance with Holm-Šídák post hoc test was used to compare anatomic characteristics between sexes in 3 age groups: prepubertal school-aged children (7-10 years old), early adolescents (11-14 years old), and late adolescents (15-18 years old)., Results: Patellar height (female sex), lateral patellar tilt angle (male sex), and trochlear sulcus angle (both sexes) decreased with age ( P < .001). Trochlear height, depth, and TT-TG distance increased with age in both male and female participants ( P < .02). Male participants had a larger sulcus angle (by 5.3°± 1.6° at age 11-14 years) and greater trochlear height (by >5 mm across medial, central, and lateral regions at age 15-18 years) than age-matched female participants ( P < .01). We found no other sex-related differences in quantified anatomic features ( P > .1)., Conclusion: The findings partially support our hypothesis indicating significant age-related changes in all quantified features, which were not different between male and female participants except for trochlear sulcus angle in early adolescence and trochlear height in late adolescence. In general, the majority of anatomic risk factors for patellar instability change with maturity in a direction that assists in reducing the risk of patellar instability and/or dislocation. The only outlier is the TT-TG distance, which increased by age, and in our oldest cohort of patients, the mean fell below the normal adult range. The current observations highlight the importance of age in the interpretation of risk for injury as well as the need for further studies to identify intrinsic and extrinsic factors that may result in abnormal development of these anatomic features during skeletal growth and maturation.

Purpose: Patellar dislocation is associated with a range of anatomical abnormalities affecting the trochlea, extensor mechanism and the tibia. The relationship between patellofemoral instability and rotational abnormalities of the posterior condyles, trochlear groove and proximal tibia has not been adequately determined. This study aimed to identify the frequency and severity of anatomical risk factors to determine their relative contribution to patellofemoral instability., Methods: A retrospective morphological study was undertaken comparing multiple anatomical measurements with magnetic resonance imaging of 50 patients with patellofemoral instability to an age- and gender-matched Control group (n = 50). Several techniques were assessed measuring both femoral and tibial axial asymmetry. A new measurement, tibial rotational asymmetry, comparing a line between the midpoints of the collateral ligaments to the axis between the patellar tendon and posterior cruciate ligament, was assessed for its association with patellofemoral instability., Results: Compared to the controls, the patellofemoral instability group demonstrated a significant difference in tibial rotational asymmetry, with a mean of 2.9° (SD 3.2°) externally rotated vs - 1.6° (SD 2.2°) in the control group. Significant differences were also demonstrated regarding the sulcus angle, tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, patellar size and the Insall-Salvati ratio. There were no differences between groups regarding the lengths of the posterior condyles, the heights of the trochlear ridges or lateralisation of the trochlear groove. Further analysis of the patellofemoral instability group revealed a subgroup of males with normal anatomy (7/50) and a subgroup of females with isolated patella alta (7/50)., Conclusion: Patellofemoral instability is associated with tibial rotational asymmetry due to lateralisation of the tibial tubercle. It is also associated with patella alta and reduced trochlear groove depth. The femoral axial shape is otherwise unchanged., Level of Evidence: III., (© 2021. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Bipartite patella affects about 2% of people. Most cases are asymptomatic; however, some develop anterior knee pain during sports. When conservative treatment fails, surgery can be considered. This study reports the outcomes of fragment excision with or without lateral release in teenage athletes with symptomatic bipartite patella. The study was approved by the College of Medicine Institutional Review Board. A retrospective review was performed. Patients were excluded if age >18 or had prior knee surgery. Data collected included age, gender, BMI, sports played, Saupe classification, conservative and surgical treatment, advanced imaging used, duration of follow-up, Lysholm Score and postoperative complications. Five teenage patients were studied. The average age was 15.6 years and BMI was 23. Sports played included basketball, football, track-and-field and soccer. All patients complained of anterior knee pain exacerbated by sports. All patients failed >6 months of conservative treatment. Saupe classification included four type III (superolateral) and one type II (lateral). Two patients had an MRI. Surgical treatment included two open excisions and three arthroscopic-assisted open excisions with lateral releases. The average Lysholm Score was 97. Postoperatively, all patients returned to presurgery sporting activity at an average of 9.8 weeks (range, 6-13 weeks). A 16-year-old male treated by open excision developed a postoperative wound infection. He was successfully treated with irrigation & debridement and antibiotics and returned to sports at 6 weeks. Symptomatic bipartite patella is an uncommon cause of anterior knee pain in adolescent athletes. When pain persists despite conservative care, fragment excision with or without lateral release resulted in excellent pain relief and return to full sporting activity in all cases., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: Patella alta is an established risk factor for recurrent lateral patella dislocations. Medial patellofemoral ligament (MPFL) reconstruction has been shown to reduce patella height. Our hypothesis is that isolated MPFL reconstruction corrects patella alta, thereby reducing the risk of recurrent patella dislocation., Methods: A prospective cohort study of 33 knees which underwent MPFL reconstruction for recurrent patella dislocation. The pre-operative and post-operative patella height and Kujala knee outcome scores, as well as tibial tuberosity-trochlear groove (TT-TG) distance, and the grade of trochlear dysplasia were recorded., Results: The mean age was 21.5 years (16-34 years). There was significant reduction in patella height in all patients (p < 0.001), a 67% normalisation of patella alta (CD ≥ 1.2) (p < 0.004), and improvement in the Kujala scores 57.1 (pre-operatively) to 94.8 (post-operatively, p < 0.0001). The recurrent dislocation rate was 3%., Conclusion: MPFL reconstruction alone results in correction in patella alta and improvement in clinical outcomes., (© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Patella alta is a common and significant abnormality responsible for many patellofemoral joint-related conditions. Many methods of patella height measurements are described; however, patellotrochear index (PTI) is the most logical method as it measures the direct relation between patella and trochlea. The aim of this study is to investigate PTI in normal healthy asymptomatic volunteers to understand the patellofemoral relation in normal knees. Twenty-five healthy volunteers underwent magnetic resonance imaging (MRI) scans of both knees. Two observers independently measured PTI on two different occasions at 6-week interval. Statistical analysis was performed to identify intra- and interobserver correlation between two observers and the mean value of PTI. Agreement analysis was performed according to Bland and Altman. Comparisons of means were made using paired t -tests. The mean age of 25 healthy volunteers was 21.28 years (19-23) with a male:female ratio of 14:11. The overall mean PTI value of all observations was 36.8% and pooled standard deviation (SD) 11.5%. Intraclass correlation (ICC) testing showed "good" interobserver ICC between two observers for PTI for both first (0.80) and second (0.84) set of measurements. There was "excellent" intraobserver correlation for two sets of measurements of PTI made by each first (0.96) and second (0.91) observer. Intraobserver repeatability for PTI was ± 0.07 and ± 0.1, respectively, for the first and second observer. Interobserver repeatability for PTI was ± 0.159 and ± 0.133, respectively, for the first and second set of measurements. Analysis of individual measurements of patella and trochlear articular cartilage revealed that the largest repeatability values were for trochlea measurements. The study reports that the average PTI in asymptomatic healthy knee utilizing current clinical MRI scanning conditions is 36.8%. This provides surgeons with a gold standard normal PTI value, which can serve as a target value in clinical diagnosis as well as surgical correction of patella height. There is good to excellent intra- and interobserver correlation with limited variability in assessing patella height using PTI on MRI scan., Competing Interests: None declared., (Thieme. All rights reserved.)

Rationale: Evaluation of clinical and radiologic abnormalities in patients with postaxial hypoplasia of the lower extremity (PHLE) for treatment decisions represents a major challenge, which is more complicated when PHLE is associated with congenital dislocation of the patella., Patient Concerns: : Herein, we present the case of an 8-year-old female patient with evident length inequality in her left lower extremity and inability to walk., Diagnoses: Radiological evaluation revealed PHLE with fibular hemimelia, proximal femoral focal deficiency, tarsal coalition, and congenital patellar dislocation of the patella. The right lower extremity was also affected by fibular hemimelia., Interventions and Outcomes: Surgical management included the Roux-Goldthwait technique for patellofemoral joint realignment, a medial knee stapled with Blount technique, and femur enlargement using the Wagner technique. The results from surgical intervention included a left femoral elongation of 6.7 cm featuring callus with angulation, displacement, and a discrepancy of 5 cm between femurs with a flexor contraction in the knee of -15° and a centralized knee., Lesson: PHLE accompanied by congenital dislocation of the patella has not been extensively described in the literature; therefore, there is no established management. Starting reconstruction at an early age, together with an adequate classification of the deformity, are essential factors when opting for limb reconstruction., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Displaced patella fracture is commonly treated with open reduction and internal fixation (ORIF). Wound complications after surgery often lead to prolonged hospitalization and dissatisfaction of patients. Periarticular adiposity and swelling may be associated with wound complications. The purpose of this study is to determine the relationship between periarticular soft tissue thickness and wound complications after ORIF of patella fractures., Methods: We retrospectively studied 237 patients undergoing ORIF for patella fractures from June 2017 to February 2021 at our institution. We established periarticular soft tissue thickness ratio (PSTTR) to evaluate soft tissue status on lateral knee X-ray radiographs. Univariate analysis was performed to identify the association between PSTTR and postoperative wound complication. A receiver-operating characteristic (ROC) curve analysis was performed to evaluate the predictive value of PSTTR., Results: The incidence of postoperative wound complication was 10.5%. Minor wound complication occurred in 24 patients, and major wound complication occurred in one patient. The average femoral PSTTR (fPSTTR) was 0.94 ± 0.17 and the average tibial PSTTR (tPSTTR) was 0.66 ± 0.16. fPSTTR proved to be associated with postoperative wound complication. In the ROC analysis of fPSTTR predicting postoperative wound complication, the area under curve (AUC) was 0.676, which indicated a moderate predictive value., Conclusions: PSTTR was a feasible method to assess periarticular soft tissue. The increased fPSTTR was associated with wound complications after ORIF of patella fractures., (© 2022. The Author(s).)

Case: A 55-year-old man with Down syndrome (DS) suffered from chronic irreducible right patellar dislocation. Imaging studies showed an attenuated appearance of the medial patellar retinaculum, and the tibial tubercle to trochlear groove distance measured 1.6 cm. Right medial patellofemoral ligament reconstruction (MPFLR) and lateral lengthening (LL) with proximalization of the tibial tubercle (PTT) were performed with good surgical outcomes., Conclusion: The combination of MPFLR, LL, and PTT is a viable option for treating a skeletally mature DS patient with patellofemoral instability causing recurrent patellar dislocation., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/B842)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Introduction: Many patella height indices exist in the literature. There is no single universally accepted radiological assessment for measuring patella height. The aims of this study were to determine which of the commonly used indices can most reliably measure patella height and compare the findings on both plain X-ray and magnetic resonance imaging (MRI) of the knee., Methods: This case-controlled study compared patients with recurrent patella instability (patella group) to a control group. Two observers measured six validated patella height indices on X-ray and MRI of both groups at two separate time periods. Between-group and within-group statistical analysis was undertaken of the data. The inter- and intra-observer reliability was assessed using the intraclass correlation coefficient (ICC) and the kappa measure of agreement (k)., Results: Forty-four patients comprised the patella group and 50 patients the control group. There was a significant difference of most indices between the two groups (p < 0.05). There was a significant difference of most indices between the two imaging modalities (p < 0.05). The Insall-Salvati ratio had the greatest inter-observer reliability for both X-ray and MRI (ICC = 0.79 to 0.97; p < 0.001) (k = 0.50 to 1.00; p < 0.001)., Conclusion: Patella height indices significantly differ when measured on X-ray as compared to MRI. This may infer that a different set of normative values are required for each radiological modality, which we have proposed in this study. Overall, the Insall-Salvati ratio performed best and shows a high degree of intra- and inter-observer reliability on both X-ray and MRI., (© 2021. ISS.)

Purpose: The treatment of comminuted patellar fractures remains a challenge for orthopedic surgeons. The aim of this study was to assess the clinical, functional, and radiological outcome after treatment of comminuted patellar fractures using an anatomically contoured plating system., Methods: Between January 2015 and December 2019 (5 years), 29 patients with complex C3 fractures according to AO classification (18 female, 11 male; mean age: 53 years) were treated using an anatomically contoured plating system (patella SuturePlate™, Arthrex®, Naples, USA). Indication for surgery was based on instability and/or initial fragment dislocation (> 2 mm). After a minimum follow-up of 12 months, patients were examined using a standardized clinical examination and functional outcome was assessed using specific knee scores (Lysholm, WOMAC, IKDC, Kujala, and Tegner score). In addition, complications were recorded and all available radiographs were evaluated regarding osteoarthritis and reduction quality., Results: All patients returned for follow-up investigation after an average of 19 months (range: 12-48 months). A mean range of motion (ROM) of 131° (range: 100-150) was recorded. Overall good functional outcome parameters could be reported, with a mean Lysholm score of 84.7 (range: 100-45), a WOMAC of 5.1 (range: 0-19.2), a Kujala scale of 85.5 (range: 100-48), an IKDC of 76.6 (range: 100-44.8), and a Tegner score of 4.3 (range: 10-3) with a difference of 0.62 to pre-operative. Patient satisfaction was rated 8.4 (range: 4-10) using a VAS. No loss of reduction, mechanical failure, or implant complications were detected. Radiological follow-up showed no evidence of relevant post-traumatic retropatellar osteoarthritis. In 7 cases, implants were removed due to subjective mechanical irritation., Conclusion: Anatomically contoured patellar plates allow secure fixation of the fracture fragments even in comminuted cases. Especially when tension-band wiring is prone to early failure, locking plate fixation represents a viable option leading to good functional results and low complication rates., (© 2022. The Author(s) under exclusive licence to SICOT aisbl.)

Background: Patella alta is a known risk factor for patellar instability and, in the setting of recurrent patellar instability with significant patella alta, correction of patellar height with a tibial tubercle osteotomy (TTO) may help decrease the failure of soft tissue-based stabilization., Purpose: To perform a systematic review and meta-analysis of radiographic and clinical outcomes after TTO for patella alta., Study Design: Systematic review and meta-analysis; Level of evidence, 4., Methods: PubMed, OVID/Medline, and Cochrane databases were queried in June 2020 for studies reporting outcomes of TTO for patella alta. Data pertaining to study characteristics and design, radiographic and clinical outcome values, and incidence of complications and reoperations were extracted. DerSimonian-Laird continuous and binary random-effects models were constructed to (1) perform subgroup-based analysis of mean changes in radiographic indices after TTO and (2) quantify the pooled incidence of complications and reoperations., Results: Eight studies including 340 patients (420 knees) with a mean age of 24.7 ± 8.4 years were included. The mean follow-up was 53.1 months (range, 3-120 months), with 1 study reporting a mean follow-up of less than 2 years. The pooled mean anterior transfer was 5.6 mm; the mean medial transfer was 8.7 ± 1.3 mm; and the pooled mean distalization of the tibial tubercle was 12.2 ± 4.5 mm. Continuous random-effects meta-analysis determined that significant reductions in the mean Insall-Salvati ratio (1.40 vs 0.98, P < .001), Caton-Deschamps index (1.26 vs 0.97, P < .001), and tibial tubercle to trochlear groove ratio (18.27 vs 10.69, P < .001) were observed after TTO. The overall incidence of complications was 7.6% (95% CI, 4.8%-10.5%), while the overall incidence of reoperations was 14.3% (95% CI 6.2%-22.4%)., Conclusion: TTO for patellar instability in the setting of patella alta results in a significant decrease in patellar height with varying degrees of medialization depending on the utilized technique. A mean postoperative complication rate of 7.6% was reported with a reoperation incidence of 14.3%, related primarily to hardware removal.

Vertical stress fractures of the patella are rare, with only a handful of bilateral cases reported. Stress fractures in the athletic community are often due to repetitive strain and submaximal loading, with minimal recovery time. An Olympic marathon runner in her 30s presented with right anterolateral knee pain. MRI revealed an acutely displaced vertical fracture of the lateral patella. After failure of non-operative treatment, she underwent surgical excision of the fracture fragment and lateral patellofemoral retinacular repair. Despite return to light training pain-free 3 weeks after surgery, she presented 2 months later with a contralateral vertical patella stress fracture. On this occasion, early operative treatment was performed with early return to training and resolution of symptoms.This is the first reported case of bilateral vertical patellar stress fractures in an athlete treated with excision of the fracture fragment. This is an excellent option for elite athletes who require a quick postoperative recovery, complete resolution of symptoms and early return to preinjury level of sport., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

We present a rare, previously undescribed case of a superior patella sleeve fracture in a skeletally immature adolescent male, just 1 month following surgery for an ipsilateral traumatic inferior pole patella fracture. This was initially missed resulting in a delay to surgery. We recommend a high index of suspicion is key in these patients who re-present following subsequent trauma and alternative X-ray views such as a flexed lateral can be extremely beneficial.

Objective: An inferior pole fracture of the patella requires surgical treatment to restore the knee extension mechanism of the knee joint. Different from other types of patellar fractures, inferior pole fractures are usually comminuted, and other traditional fixation methods, such as tension band wiring, may not meet the fixation needs. We propose fixing inferior pole fractures of the patella with a custom-made anchor-like plate combined with cerclage and report the surgical outcomes., Material and Methods: This is a retrospective clinical study. From June 2018 to August 2020, 21 patients with inferior patella fracture treated at Hong Hui Hospital Affiliated to Xi'an Jiaotong University received a custom-made anchor-like plate combined with cerclage. Complications of the surgical fixation methods and final knee function were used as the main outcome measures., Results: All fractures achieved good union, and the union time ranged from 8 to 12 weeks. No patients had serious complications, such as internal fixation failure or infection. The average duration of surgery of patients was 75.05 7.26 min, and the intraoperative blood loss was 60.099.49 ml. At the last follow-up, the range of motion of the knee was 120°-140°, with an average of 131.436.92°, the Bostman score was 27-30, and the Lysholm score ranged from 82 to 95. All patients showed good knee function one year after the operation., Conclusion: We used a modified T-shaped plate combined with cerclage technology to fix inferior fractures pole of the patella, providing reliable fixation, allowing early functional exercise of the knee joint, and providing patients with good knee joint function after surgery., (© 2022. The Author(s).)

The influence of joint degeneration on the biomechanical properties of calcified cartilage and subchondral bone plate at the osteochondral junction is relatively unknown. Common experimental difficulties include accessibility to and visualization of the osteochondral junction, application of mechanical testing at the appropriate length scale, and availability of tissue that provides a consistent range of degenerative changes. This study addresses these challenges. A well-established bovine patella model of early joint degeneration was employed, in which micromechanical testing of fully hydrated osteochondral sections was carried out in conjunction with high-resolution imaging using differential interference contrast (DIC) optical light microscopy. A total of forty-two bovine patellae with different grades of tissue health ranging from healthy to mild, moderate, and severe cartilage degeneration, were selected. From the distal-lateral region of each patella, two adjacent osteochondral sections were obtained for the mechanical testing and the DIC imaging, respectively. Mechanical testing was carried out using a robotic micro-force acquisition system, applying compression tests over an array (area: 200 μm × 1000 μm, step size: 50 μm) across the osteochondral junction to obtain a stiffness map. Morphometric analysis was performed for the DIC images of fully hydrated cryo-sections. The levels of cartilage degeneration, DIC images, and the stiffness maps were used to associate the mechanical properties onto the specific tissue regions of cartilage, calcified cartilage, and subchondral bone plate. The results showed that there were up to 20% and 24% decreases (p < 0.05) in the stiffness of calcified cartilage and subchondral bone plate, respectively, in the severely degenerated group compared to the healthy group. Furthermore, there were increases (p < 0.05) in the number of tidemarks, bone spicules at the cement line, and the mean thickness of the subchondral bone plate with increasing levels of degeneration. The decreasing stiffness in the subchondral bone plate coupled with the presence of bone spicules may be indicative of a subchondral remodeling process involving new bone formation. Moreover, the mean thickness of the subchondral bone plate was found to be the strongest indicator of mechanical and associated structural changes in the osteochondral joint tissues., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Introduction: The current technique of angulating for a skyline knee projection relies heavily on the radiographer's estimation of the patella tilt, rendering it subjective and prone to errors. This study therefore aims to (i) examine the correlation between angle ABC measured on the lateral X-ray image and skyline angulation (measured in degrees) and (ii) determine the inter-rater reliability of angle ABC measurements., Methods: 145 sets of lateral and skyline X-ray images from patients aged 40-70 years old were retrospectively analysed. Angle ABC was measured using prominent landmarks such as the trochlear sulcus, tibial tuberosity and the anterior border of the patella on the lateral knee radiograph. It was then retrospectively compared with the skyline tube angulations to identify any correlation between the two. An inter-rater reliability test was also conducted using the intraclass correlation coefficient (ICC) to determine the reproducibility of the measurement method., Results: A weak correlation was found between angle ABC and skyline angulation (r = 0.1, p = 0.25). The proposed method of measurement shows good inter-rater reliability (ICC = 0.81, 95% CI: 0.77 to 0.84)., Conclusion: There is insufficient evidence to indicate a correlation between angle ABC and skyline angulation. However, angle ABC can be reliably measured, implying the replicability of the measurement method for other purposes., Implications for Practice: The proposed measurement method of angle ABC on the lateral view could have future applications in other areas such as in the measurement of patellofemoral alignment and trochlear morphology., Competing Interests: Conflict of interest statement None., (Copyright © 2021 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.)

Purpose: To provide normal values for physiological patellofemoral tracking in a representative group of healthy individuals, as well as sex differences, using real-time 3T-magnetic resonance imaging (MRI) and to test for the reliability of the presented technique., Methods: One hundred knees of healthy individuals with no history of patellofemoral symptoms were scanned with dynamic MRI sequences, during repetitive cycles of flexion (40°) and full extension. Within a 30-seconds time-frame, three simultaneous, transverse slices were acquired. Dynamic mediolateral patellar translation (dMPT) and dynamic patellar tilt (dPT) were measured on two occasions by two independent examiners. Common radiological parameters were measured using static MRI, and correlations were calculated., Results: 100 knees (53 right, 47 left; age: 26.7 ± 4.4 years; BMI: 22.5 ± 3.1) of 57 individuals (27 females, 30 males) were included. Mean height was 170.1 ± 7.7 cm in women and 181.8 ± 6.4 cm in men. Average patella diameter was 37.9 ± 2.7 (95% CI 37.1-38.7) mm in women and 42.4 ± 3.2 (95% CI 41.5-43.3) mm in men. In females, the patellar diameters and intercondylar distances were significantly smaller than in males (P < .001). Radiological parameters for patellar maltracking were within the normal range. During the range of motion, mean dMPT was 1.7 ± 2.4 (95% CI .9-2.5) mm in females and 1.8 ± 2.7 (95% CI 1.1-2.6) mm in males (P = .766). Mean dPT was 1.3 ± 2.9° (95% CI .4-2.1°) in females and -0.2 ± 3.8° (95% CI -1.2-.9°) in males (P = .036). Neither dMPT nor dPT was correlated with height, BMI, or patellar diameter. Intercondylar distance correlated weakly with dPT (r = -.241; P = .041). Intra- and interrater reliability were excellent for dMPT and dPT., Conclusion: Dynamic mediolateral patellar translation is a size- and sex-independent parameter for proximal patellar tracking. In healthy individuals without patellofemoral abnormalities normal dMPT proximal to the trochlea groove was 1.7 ± 2.5 (1.2-2.2) mm, independent of size or sex. Normal dPT showed a dependency on sex and was 1.3 ± 2.9 (.4-2.1)° in women and -0.2 ± 3.8 (-1.2-0.9)° in men., Level of Evidence: Level II, diagnostic study., (Copyright © 2021 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)