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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.)

»: An osteochondral fracture (OCF) of the patella or the femur is a frequent sequela after an episode of acute patellofemoral instability., »: Patients commonly present with anterior knee pain after direct trauma to the patella or a noncontact twisting injury., »: Radiographs and magnetic resonance imaging (MRI) are the most common imaging modalities that are used to diagnose OCFs., »: Arthroscopy may be indicated in cases of displaced OCFs, and the decision regarding osteochondral fragment fixation or loose body removal depends on fragment size, location, and extent of injury., »: Most of the current literature suggests worse outcomes for patients with OCFs who undergo nonoperative treatment, no significant differences in outcomes for patients sustaining an acute patellar dislocation with or without an OCF, and inconclusive results concerning outcomes for patients treated with loose body removal compared with fixation., »: Current outcome data are limited by studies with low levels of evidence; therefore, well-designed randomized controlled trials are needed., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSREV/A825)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Objective: The study was performed to evaluate cartilage within the knee following a first-time patellar dislocation, using elevated MRI-based T1ρ relaxation times as an indicator of low proteoglycan concentration. The hypothesis is that MRI-based T1ρ relaxation times for patellofemoral and tibiofemoral cartilage are significantly longer for knees being treated for patellar dislocation than for healthy control knees., Design: Twenty-one subjects being treated for a first-time, unilateral dislocation of the patella and 16 healthy controls participated in MRI-based T1ρ relaxation time mapping. Mean relaxation times were quantified for patellofemoral and tibiofemoral regions for injured knees, the contralateral knees, and healthy controls. T1ρ values for each region were compared between the 3 groups with generalized estimating equations. Linear regressions were also performed to correlate T1ρ relaxation times with time from injury., Results: The knees with a disloction had longer T1ρ relaxation times than the contralateral knees and control group at the medial patella and longer relaxation times than the control group at the lateral tibia ( P < 0.05). T1ρ relaxation times at the medial patella also decreased with time from injury (r 2 = 0.21, P = 0.037)., Conclusions: Compositional changes to cartilage on the medial patella are related to traumatic impact during a dislocation. Potential exists for cartilage properties at the medial patella to improve with time. Cartilage degradation at the lateral tibia is not directly related to traumatic impact. The current baseline data are a starting point to characterize the pathway from a first-time dislocation to progressive cartilage degradation and osteoarthritis.

Purpose: Identifying anatomical risk factors on recurrent dislocation after medial reefing is important for deciding surgical treatment. The present study aimed to retrospectively analyze the preoperative magnetic resonance imaging (MRI)-based parameters of patients treated with medial reefing and whether these parameters lead to a higher risk of recurrent dislocation., Methods: Fifty-five patients (18.6 ± 6.6 years) who underwent medial reefing after primary traumatic patellar dislocation (84% with medial patellofemoral ligament [MPFL] rupture) were included. Patients were followed up for at least 24 months postoperatively (3.8 ± 1.2 years) to assess the incidence of recurrent patellar dislocation. In patients without recurrent dislocation, the Kujala and subjective IKDC scores were assessed. Moreover, the tibial tubercle-trochlear groove (TT-TG), sulcus angle, patellar tilt, patellar shift, and lateral trochlea index (LTI) were measured. The patellar height was measured using the Caton-Dechamps (CDI), Blackburne-Peel (BPI), and Insall-Salvati index (ISI). The cohort was subclassified into two groups with and without recurrent dislocation. Differences between groups were analyzed with respect to the MRI parameters., Results: Forty percent had a pathological sulcus angle of > 145°, 7.2% had an LTI of < 11°, 47.3% had a patellar tilt of > 20°, and 36.4% had a TT-TG of ≥ 16 mm. Increased patellar height was observed in 34.5, 65.5, and 34.5% of the patients as per CDI, BPI, and ISI, respectively. Nineteen (34.5%) patients suffered from recurrent dislocation. Compared with patients without recurrent dislocation, those with recurrent dislocation had a significantly lower LTI (p = 0.0467). All other parameters were not significantly different between the groups. Risk factor analysis showed higher odds ratios (OR > 2), although not statistically significant, for MPFL rupture (OR 2.05 [95% confidence interval 0.38-11.03], LTI (6.6 [0.6-68.1]), TT-TG (2.9 [0.9-9.2]), and patellar height according to ISI (2.3 [0.7-7.5]) and CDI (2.3 [0.7-7.5])). Patients without recurrent dislocation had a Kujala score of 93.7 ± 12.1 (42-100) points and an IKDC score of 90.6 ± 11.7 (55.2-100) points., Conclusion: Anatomical, MRI-based parameters should be considered before indicating medial reefing. A ruptured MPFL, an LTI < 11°, a TT-TG ≥ 16 mm, a patellar tilt > 20 mm, and an increased patellar height according to ISI and CDI were found to be associated, although not significantly, with a higher risk (OR > 2) of recurrent patellar dislocation after medial reefing. Thorough preoperative analysis is crucial to reduce the risk of recurrent dislocation in young patient cohorts., Level of Evidence: Level IV., (© 2021. The Author(s).)

Aim: To investigate a possible relationship between both the volume and morphology of the patella and the volume of the trochlea in trochlear dysplasia (TD)., Materials and Methods: Eighteen patients with TD and 18 controls were evaluated retrospectively in two groups using computed tomography (CT). Patellar morphology was evaluated with the standard measurement methods described in the literature. Additionally trochlear sulcus volume (TV) and patellar volume (PV) were measured quantitatively using the three-dimensional volume-rendering method. The relationship between patella dimensions and volume and trochlea volume was evaluated., Results: The length of the medial patellar facet (lMP), patellar width (PW), TV and PV were significantly lower in the patient group. When compared according to Dejour types, PW was statistically significantly lower than the control group in those with high-grade and those with low-grade dysplasia. A positive correlation was found between the TV and PV in both groups (patient group: r=0.583 p=0.011; control group: r=0.485 p=0.042). CONCLUSİONS: PV and the TV are related. Therefore, PV can be used as a determining parameter in the evaluation of TD. This technique can also be used for prosthesis construction and more accurate surgical planning., (Copyright © 2022 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

The patella-patellar tendon angle (PPTA) assessing the sagittal patellar tilt was reported to be related with anterior knee pain. Herein, clinical effect of PPTA in patients with medial patellar plica (MPP) syndrome, chondromalacia patella, and infrapatellar fat pad (IPFP) syndrome, the most common causes of anterior knee pain, was evaluated. In this retrospective study, 156 patients with anterior knee pain who underwent magnetic resonance imaging (MRI) and arthroscopic surgery that confirmed isolated MPP syndrome, chondromalacia patella, or IPFP syndrome from June 2011 to January 2021 were included in the study group and 118 patients without knee pathology on MRI during the same period were included in the control group. The PPTA was measured on knee MRI and compared between the two groups. A receiver operating characteristic (ROC) analysis was used to evaluate the value of PPTA for predicting the risk of patellofemoral joint disorder. The mean PPTA was significantly smaller in study group (138.1 ± 4.2°) than control group (142.1 ± 4.3°) (p < 0.001). However, there was no significant difference in PPTA among the patients with MPP syndrome, chondromalacia patella, and IPFP syndrome. Furthermore, the ROC analysis revealed that the area under curve, sensitivity, and specificity for predicting the risk of patellofemoral joint disorders were 0.696, 70.3% and 57.6%, respectively, at a PPTA cutoff of 138.3°. Therefore, the smaller PPTA may be associated with MPP syndrome, chondromalacia patella, and IPFP syndrome. Furthermore, PPTA could be a predictive factor for the risk of patellofemoral joint disease in patients with anterior knee pain., Competing Interests: No. The authors have declared that no competing interests exist.

Background: Great difficulty and more failures were the descriptions of the treatment of congenital patella dislocation in pediatric patients. This study aims to evaluate the outcomes of patients with congenital patellar dislocations treated with the modified Langenskiöld procedure., Methods: The medical records of 16 knees in 11 patients with a diagnosis of congenital patella dislocation were collected from September 2016 to March 2019. They were treated with the modified Langenskiöld procedure. The mean follow-up period was 37.8 months. The outcome measures were the Lysholm score, Kujala score, patellar stability, and knee range of motion., Results: Eleven patients, namely, eight girls and three boys, with 16 knees were enrolled. The mean age at the time of operation was 3.1 years. The post-operative mean Lysholm score was 94.8 (SD 5.1; 87-100), whereas the Kujala score was 95 (SD 5.9; 86-100). There were no recurrent dislocations, and all patients had full extension postoperatively., Conclusion: The modified Langenskiöld procedure is a promising solution for the treatment of congenital patella dislocations., Level of Evidence: Level IV; Case Series; Treatment Study., (© 2022. The Author(s).)

Acute patella dislocations account for approximately 2%-3% of knee injuries and are therefore a relatively common presentation in the accident and emergency department. The majority of patella dislocations can be reduced with simple manoeuvres or even spontaneously and can be managed conservatively by bracing and rehabilitation. The aim of this study is to identify and review the main causes of the unique and unexpected event of irreducible patella dislocation and their characteristic presentations. Irreducible patella dislocations can happen but are very rare. Currently, a limited number of case reports are available, prompting for a need for research on this topic. This case study can shed light on the possible pathogenesis and pathognomonic features of irreducible patella dislocations and provide insight on the available therapeutic approaches., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Abstract: The technique of transosseous tunnels is widely used in lower pole patella fracture (LPP). Though the extensor mechanism can be restored, distal avulsion fragments are usually unstable. The subsequent fracture gap and nonunion impair the extensor mechanism in turn. Cerclage is a promising method for treating the condition. The aim of this prospective cohort study is to determine if cerclage around the patella combined with the technique of transosseous tunnels stabilizes the avulsion fragments and brings out improved outcomes on LPP.Twenty two patients with LPP were treated with the hybrid technique. The patients were followed up and evaluated clinically and radiographically. The functional outcome was assessed by the average range of knee movement and Lysholm knee rating system at 6 months after surgery, as well as the final follow-up. Radiologically, Insall-Salvati ratio and the time from surgery to bone union were assessed.Postoperatively, with a mean followed-up of 12 months. All of the patients regained stability of the knee with an average range of movements of 131.8 degrees at 6 months after operation and 138.2 degrees at the final follow-up. On the Lysholm knee rating system, all cases were classified as excellent. The average score was 93.2 at 6 months after operation and 95.9 at the final follow-up. In radiological assessment, no fracture gap or nonunion occurred. The average Insall-Salvati ratio (I-S ratio) was 1.03.The hybrid technique offers further stabilization for the avulsion fragments and strengthens attachment of the patellar tendon, which brings forward time of rehabilitation and achieves good clinical outcomes., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: The lateral patellofemoral complex (LPFC) is an important stabilizer of the patella composed of the lateral retinacular structures including the lateral patellofemoral ligament (LPFL), the lateral patellomeniscal ligament (LPML), and the lateral patellotibial ligament (LPTL). While the isolated anatomy of the LPFL has been previously described, no previous study has investigated the entirety of the LPFC structure, length changes, and radiographic landmarks. An understanding of LPFC anatomy is important in the setting of LPFL injury or previous lateral release resulting in iatrogenic medial instability requiring LPFC reconstruction., Purpose: To both qualitatively and quantitatively describe the anatomy and length changes of the LPFC on gross anatomic dissections and standard radiographic views., Study Design: Descriptive laboratory study., Methods: Ten nonpaired cadaveric specimens were utilized in this study. Specimens were dissected to identify distinct attachments of the LPFL, LPML, and LPTL. Ligament lengths, footprints, and centers of each attachment were described with respect to osseous landmarks using a 3-dimensional coordinate measuring device. Ligament length changes were also assessed from 0° to 90° of flexion. Radiopaque markers were subsequently utilized to describe attachments on standard anteroposterior and lateral radiographic views., Results: The individual elements of the LPFC were identified in all specimens. The LPFL patellar attachment had an average total length of 22.5 mm (range, 18.3-27.5 mm), involving a mean of 59% (range, 50%-75%) of the sagittal patella. Based on the average patellar size, a mean of 63% of the LPFL attached to the patella, and the remainder (11.1 ± 1.4 mm) inserted into the patellar tendon. The femoral attachment of the LPFL had a mean maximum length of 24.4 ± 4.3 mm. The center of the LPFL femoral attachment was a mean distance of 13.5 ± 3.2 mm anterior and distal to the lateral epicondyle. The LPFL demonstrated significant shortening, especially in the first 45° of flexion (7.5 ± 5.1 mm). In contrast, the LPTL (5.5 ± 3.0 mm) and LPML (10.0 ± 3.3 mm) demonstrated significant shortening from 45° to 90°. On lateral radiographs, the center of the femoral attachment of the LPFL was a mean total distance of 19.2 ± 7.2 mm from the lateral epicondyle., Conclusion: The most important findings of this study were the correlative anatomy of 3 distinct lateral patellar ligaments (LPFL, LPML, and LPTL) and their anisometry through flexion. All 3 components demonstrated significant shortening during flexion. The quantitative and radiographic measurements detailed the LPFL osseous attachment on the patella; soft tissue attachment on the patellar tendon; and finally, the osseous insertion on the femur distal and anterior to the lateral epicondyle. Similarly, the authors documented the meniscal insertion of the LPML and defined a patellar insertion of the LPTL and LPML as a single attachment. These data allow for reproducible landmarks to aid in the understanding and reconstruction of the lateral patellar restraints., Clinical Relevance: The data produced from this investigation provide a comprehensive description of these 3 lateral patellar stabilizers (LPFL, LPML, LPTL). These data can be used intraoperatively to facilitate anatomic reconstructions of the lateral patellar stabilizers.

Background: The Insall-Salvati ratio is a technique for determining patellar height that relies on bony landmarks. Magnetic resonance imaging (MRI) and plain radiography are used interchangeably to assess the Insall-Salvati ratio in the pediatric population despite the lack of validity in the literature., Objective: The purpose of this study was to investigate if the Insall-Salvati ratio and patella alta as determined on MRI are comparable to those determined on radiography in pediatric patients., Materials and Methods: We conducted a retrospective review of 49 pediatric patients (age range: 7.5-17.0 years) with unfused growth plates who underwent both knee MRI and lateral knee radiography. Measurements for calculating the Insall-Salvati ratio (the ratio of patella tendon length to patella length) were obtained by three observers. Data were analyzed using paired t-tests and Pearson's correlation. A reliability assessment and inter-method agreements were performed. Patella alta was defined as an Insall-Salvati ratio > 1.2. Additional cutoffs of Insall-Salvati ratios > 1.3 and > 1.4 were also analyzed., Results: There was no statistically significant difference between Insall-Salvati ratio as determined on MRI (mean: 1.20) and radiographs (mean: 1.25; P > 0.05). There was a strong correlation between Insall-Salvati ratio as determined on MRI and radiographs (Pearson's r = 0.6) with moderate consistency (Cronbach's alpha = 0.78). There was a good level of agreement between the diagnosis of patella alta on MRI and radiographs when defined as an Insall-Salvati ratio greater than 1.2 and 1.3 (Cohen's kappa = 0.61)., Conclusion: The results demonstrate a strong association between Insall-Salvati ratio and patella alta derived from MRI and radiographs in children ages 7.5 years and older., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: The purpose of this study was to: (1) test the hypothesis that HTO improves articular cartilage composition in the medial compartment without adversely affecting the lateral compartment and patella, and; (2) explore associations between knee alignment and cartilage composition after surgery., Methods: 3T MRI and standing radiographs were obtained from 34 patients before and 1-year after HTO. Articular cartilage was segmented from T2 maps. Mechanical axis angle (MAA), posterior tibial slope, and patellar height were measured from radiographs. Changes in T2 and radiographic measures were assessed using paired t tests, and associations were assessed using Pearson correlation coefficients., Results: The mean (SD) MAA before and after HTO was - 6.5° (2.4) and 0.6° (3.0), respectively. There was statistically significant shortening [mean (95%CI)] of T2 in the medial femur [- 2.8 ms (- 4.2; - 1.3), p < 0.001] and medial tibia [- 2.2 ms (- 3.3; - 1.0), p < 0.001], without changes in the lateral femur [- 0.5 ms (- 1.6; 0.6), p = 0.3], lateral tibia [0.2 ms (- 0.8; 1.1), p = NS], or patella [0.5 ms (- 1.0; 2.1), p = NS). Associations between radiographic measures and T2 were low. 23% of the increase in lateral femur T2 was explained by postoperative posterior tibial slope (r = 0.48)., Conclusion: Performing medial opening wedge HTO without overcorrection improves articular cartilage composition in the medial compartment of the knee without compromising the lateral compartment or the patella. Although further research is required, these results suggest HTO is a disease structure-modifying treatment for knee OA., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Background: Inferior pole patellar sleeve fractures (PSFs) are rare injuries that occur in skeletally immature patients that may be missed or falsely diagnosed as an inferior pole fracture (IPF) or Sinding-Larsen-Johansson syndrome (SLJS)., Purpose: The objective of this study was to evaluate and compare clinical and radiographic features of patients with PSF, IPF, and SLJS., Study Design: Cross-sectional study; Level of evidence, 3., Methods: Retrospective review of skeletally immature patients diagnosed with PSF, IPF, and SLJS between 2011 and 2019 at a single urban academic center was performed. Chart and radiographic review was completed. Between-group differences were assessed using analysis of variance, Kruskal-Wallis test, and Fisher exact test, as appropriate to variable distributions., Results: In total, 125 patients (82% male) were included, with a mean (SD) age of 10.7 (2) years (16 PSF, 51 IPF, 58 SLJS). There were no significant differences in patient characteristics between the 3 groups. One hundred percent of the patients with PSF ( P < .001) and IPF ( P < .001) had acute trauma, compared with 24% of patients with SLJS. Fewer patients with PSF had an intact straight leg raise (38%) compared with those with IPF (94%; P < .001) and SLJS (98%; P < .001). Fewer patients with SLJS had knee swelling (41%) compared with those with PSF (93%; P < .001) and IPF (94%; P < .001). More patients with PSF had knee effusion (81%) compared with those with IPF (37%; P = 0.011) and SLJS (3%; P < .001). More patients with SLJS were able to bear weight (88%) compared with those with IPF (12%; P < .001) and PSF (0; P < .001). Radiographically, compared with those with IPF and SLJS, patients with PSFs had increased mean prepatellar swelling (6.1 [ P < .001] and 6.5 [ P < .001] vs 12.9 mm), intra-articular effusion (6.1 [ P = .014] and 4.9 [ P = .001] vs 9.2 mm), maximum fragment size (26 [ P = .004] and 17.7 [ P < .001] vs 45.3 mm), and maximum fragment displacement (1.24 [ P = .002] and 1.45 [ P = .003] vs 13.30 mm), respectively. Compared with those with SLJS (1.10), patients with PSF (1.92; P < .001) and IPF (1.22; P < .001) had patella alta with higher mean Insall-Salvati ratios >1.2., Conclusion: Differences in clinical features such as ability to straight leg raise, knee swelling, knee effusion, ability to bear weight, and radiographic features, such as prepatellar swelling, intra-articular effusion, fragment displacement/size/shape/location, and patellar height, can all be helpful in recognizing rare pediatric inferior patellar pathology, thus increasing efficiency in indicating for higher-level imaging to reach a prompt diagnosis and provide appropriate treatment.

Obesity is a primary risk factor for osteoarthritis. While previous work has addressed relationships between in vivo cartilage mechanics, composition, and obesity in the tibiofemoral joint, there is limited information on these relationships in the patellofemoral joint. The purpose of this study was to compare the patellofemoral cartilage mechanical response to walking in participants with normal and obese body mass indices (BMIs). Additionally, patellar cartilage T1rho relaxation times were measured before exercise to characterize the biochemical composition of the tissue. Fifteen participants (eight with normal BMI and seven with obese BMI) underwent baseline magnetic resonance imaging (MRI) of their right knee. They then walked on a treadmill for 20 min at a speed normalized to their leg length before a second MRI scan. Subsequently, three-dimensional models of the bones and articular surfaces of the patellofemoral joint were created via manual segmentation of the pre- and post-exercise MR images to compute cartilage thickness and strain. Strain was defined as the change in patellofemoral cartilage thickness normalized to the baseline thickness. Results showed that participants with an obese BMI exhibited significantly increased patellofemoral cartilage strain compared to those with a normal BMI (5.4 ± 4% vs. 1.7 ± 3%, respectively; p = 0.003). Furthermore, patellar cartilage T1rho values were significantly higher in participants with obese versus normal BMIs (95 ms vs. 83 ms, respectively; p = 0.049), indicative of decreased proteoglycan content in those with an obese BMI. In summary, the altered patellofemoral cartilage strain and composition observed in those with an obese BMI may be indicative of cartilage degeneration., (Copyright © 2022. Published by Elsevier Ltd.)

We aimed to investigate the progression of patella alta (PA) in patients with cerebral palsy (CP) using the Koshino-Sugimoto (KS) index and assess associated risk factors. Participants in our retrospective study met the following inclusion criteria: patients with CP who visited our institute from May 2003 to December 2019, were ≤18 years of age, were followed up for >2 years and had at least two lateral knee radiographs. KS indices of both knee radiographs were measured for each patient. A linear mixed model was implemented. Our participants included 222 CP patients. KS index values were measured via 652 knee radiographs. Reference values of the KS index for those between 4 and 18 years of age were determined according to Gross Motor Function Classification System (GMFCS) levels. In all GMFCS levels, the KS index decreased with patients' ages (P < 0.0001). In groups where the KS index increased, GMFCS levels IV (P = 0.0045) and V (P = 0.0040) were statistically significant. Change in the KS index values indicates that PA improves as patients age within all GMFCS levels. However, in patients with GMFCS levels of IV and V, progressive PA is expected., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

The aim of this study was to evaluate the transposition distance in in vitro canine medial patellar luxation (MPL) models of different severity grades using a single radiograph of the stifle joint. Each MPL grade model was generated with manipulation and evaluated by palpating the stability of the patella. An anterior-posterior radiograph of the entire hind limb with extended hip and stifle joints, including the iliopubic eminence, was used for all measurements. The quadriceps angles and the percentage of the transposition distance to the maximum width of the proximal tibia were measured. Our results demonstrated that when the tibial tuberosity transposition procedure is performed in a clinical setting, the required distance to correct the abnormal direction of the extensor mechanism in the canine stifle joint was greater in severe grade MPL than in mild grade MPL., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Bipartite patella is an abnormality where patella is incorrectly ossified resulting in fibrocartilaginous synchondrosis. In most cases bipartite patella is asymptomatic and incidental finding but can also be painful especially in adolescents. The aim of our analysis was to determine the preferable treatment for pediatric bipartite patella. We conducted a systematic review based on PubMed and Embase searches. All original articles with reference to treatment in the population of ≤ 20 years of age, were included. Case reports, and articles without individualized data were excluded. In total, the individual data of 126 knees in 116 patients was analyzed. In 77.8% (98/126) of the analyzed knees the result was excellent, and the majority of the knees, 89.7% (105/126) received surgical intervention, and seven different techniques were used. None of operative methods were superior to others. Excellent treatment outcomes were achieved more often in younger patients (p=0.004), and the median duration of symptoms in operatively treated patients was shorter (p=0.018). If operative treatment is used after unsuccessful conservative treatment, it should be considered early in adolescence and also within a relatively short period after the onset of symptoms. The best operative method could not be found. More research and RCTs are needed concerning the conservative methods and different operative techniques.

Objectives: This study evaluates the correlation between the bone end and soft tissue end of the quadriceps tendon-patellar bone autograft (QPA) size and pre-operative MRI measurements of the quadriceps tendon along sections to be included in the graft harvest in adolescents. We also assessed association between graft diameter and anthropometric measures (height, weight, and BMI), age, and sex., Methods: Patients (10-18 years) who underwent QPA ACL reconstruction and had a pre-operative MRI were considered for inclusion. Age, height, and weight, tibial and femoral side graft diameter, and patellar bone block dimensions were collected. Using a pre-operative 2D sagittal plane MRI, we measured the quadriceps at 10-mm increments above the patella, up to 40 mm. We assessed correlation between the bone-end graft diameter and the AP measure at 10 mm above the patella, and correlation between the soft-tissue end graft diameter and the most proximal AP measure., Results: A total of 103 patients were included. A significant correlation between the soft-tissue side graft diameter and most proximal AP measurement was observed (r s  = 0.51; p < 0.001). However, measurements significantly underestimated the soft-tissue end graft diameter (9.6 ± 0.8 vs. 7.4 ± 1.1; p < 0.001). There was no correlation between the bone-end graft diameter and AP measurement 10 mm above the patella. Anthropometric measures were not associated with graft size. Skeletal maturity was associated with smaller graft size (p = 0.08)., Conclusion: Soft-tissue end graft diameter is associated with the AP measure of the quadriceps at 20-40 mm above the superior pole of the patella., (© 2021. ISS.)

Case: We report a very rare case of simultaneous ipsilateral floating hip and floating knee (SIFHFK) injury with the neck of the femur and patella fracture and hip dislocation associated with sciatic nerve injury in a 45-year-old man after a road traffic accident. We adopted a staged approach for surgical fixation of the fractures after stabilization. At the latest 2 years follow-up, the patient was asymptomatic with satisfactory clinical outcome., Conclusion: SIFHFK injuries present a challenging and emergent clinical scenario and require extensive clinical experience, careful planning, and multidisciplinary teamwork because of the paucity of specific treatment protocols for the treatment of this complex injury., 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/B805)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Objective: The patellar inferior pole fracture is typically comminuted. Hence, achieving firm fixation and early activity is highly challenging. In this article, we employed the method of wire cerclage through a generated bone hole to reduce the fracture. Our objective was to compare the clinical efficacy of patellar concentrator alone with a combination of cerclage and patellar concentrator in the treatment of patellar inferior pole fracture., Methods: We conducted a retrospective review of patients with patellar inferior pole fractures, who underwent patellar concentrator fixation only (the control group) or cerclage combined with patellar concentrator fixation (the experimental group), performed by a single surgeon, between July 2015 and October 2019. Our analysis included surgical indexes like7 aspects (fracture gap after operation, operation time, intra-operative blood loss, intra-operative number of C-arm fluoroscopies conducted, Insall-Salvati ratio calculated immediately after operation, initial range of motion on the 7th day after operation, and fracture healing time), as well as the Bostman score and complications recorded on 1-, 3-, 6-, and 12-month follow up post operation., Results: A total of 94 patients with patellar inferior pole fracture and a minimum 1-year follow up were recruited. Following operation, the control group had 33 (71.74%) patients with a fracture gap of 0-2 mm and 13 (28.26%) patients with a fracture gap greater than 2 mm (P = 0.002). Conversely, the experimental group had 46 (95.83%) patients with a fracture gap of 0-2 mm and 2 (4.17%) patients with a fracture gap greater than 2 mm (P = 0.002). Compared to the control group, the experimental group did not experience enhanced operation time or intra-operative blood loss (P = 0.811, P = 0.823). The Insall-Salvati ratio and initial range of motion in the experimental group were larger than the control group (P = 0.037, P = 0.000). Alternately, the number of intra-operative C-arm fluoroscopies conducted and fracture healing time of the experimental group were considerably less than the control group (P = 0.003, P = 0.000). Moreover, at 1-, 3-, 6-, and 12-month follow ups after operation, the Bostman scores of the experimental group were remarkably higher than the control group (P < 0.05). At 12 months post operation, 23 cases (50%) were classified as excellent, 22 cases (47.83%) were good, and 1 case (2.17%) was poor in the control group (P = 0.005). In the meantime, in the experimental group, 38 cases (79.17%) were deemed as excellent and 10 cases (20.83%) were good (P = 0.005). Lastly, complications were detected in 3 cases (6.52%; 1 case of internal fixation loss, 2 cases of hematoma) within the control group, and in 1 case(2.08%; marginal wound necrosis) within the experimental group. There was no wound infection, implant discomfort, or broken fixation in either group., Conclusion: Managing the patellar inferior pole fracture with wire cerclage through a generated bone hole is both simple and effective. Moreover, an additional step of patellar concentrator fixation facilitates early functional exercise, with satisfactory clinical outcome., (© 2022. The Author(s).)

Purpose: Patellar tracking problems represent 2-10% of complications of total knee arthroplasties (TKA) in valgus knees. However, there are no studies assessing patellar tracking according to the severity of the valgus deformity. The hypothesis was that lateral approach TKA in severe valgus deformity provides equivalent patellar tracking to that in knees with mild valgus deformity., Methods: Between 1988 and 2016, 77 TKAs were performed via a lateral approach on a severe valgus deformity (HKA > 195°). Forty-three TKAs performed without tibial tubercle osteotomy and with complete radiological data were included in this study. These were compared with 86 matched TKAs performed via a lateral approach with a mild valgus deformity (HKA between 181° and 190°). Patellar tilt and patellar position were assessed by axial view radiographs at the last follow-up. Complications and clinical outcomes were also evaluated., Results: The follow-up was mean 52 ± 21 months in the severe valgus group. No significant differences were found between the severe valgus deformity group and the mild valgus deformity groups in patellar tilt (1.6° ± 6.6° versus 1.9° ± 3.2°, respectively) or patellar subluxation. There were complications in 12% (n = 5) and 11% (n = 9) of the severe valgus group and the mild valgus group respectively, without significant difference. There was no significant difference in extensor mechanism complication rate (2.3% versus 4.7%, respectively)., Conclusion: Lateral parapatellar approach, without tibial tubercle osteotomy, for TKA in severe valgus deformity results in good patellar tracking. With this approach, the extensor mechanism complication rate in severe valgus deformity was not higher than for mild valgus deformity., Level of Evidence: III., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Introduction: Patellar fractures constitute almost 1% of total skeletal injuries. Existing common operative methods include the use of different types of Tension band wiring techniques like cannulated screws and K-wires. The Patellar plating construct is a relatively newer operative method for patellar fracture fixation with promising outcomes with fewer complications., Method: We conducted a pilot prospective study at our Apex Trauma center in twenty patients aged 18-65years with displaced patellar fractures, AO type A2, A3, B2, B3, C1, C2, C3. Fractures were fixed with low profile patellar plates (1.8 mm). Radiological and functional follow-up was done using X-rays, CT scans and BKS scoring (Bostman-Knee-Scale), Knee Society Score(KSS), and Tegner Lysholm knee scores respectively for two years., Result: Mean functional outcome scores at 6 weeks, 3 months, 6 months and 2 years was 25.5, 28.3, 29.05 and 29.9 for BKS; 64.62, 84.12, 90.6, and 97.5 for KSS; 73.75, 89.7,94.8, and 99.3 for Tegner Lysholm knee score respectively. Radiological union, confirmed by CT scan, was observed in all patients at 3 months. Two patients had superficial surgical site infection (SSI) at 2 weeks. Implant impingement was also found in 2 patients at 3 months. None of the patients had a failure of fixation at the end of the study., Conclusion: Patients with low profile patellar plate constructs have favorable clinical and radiological outcomes with minimal non-specific complications., Competing Interests: Declaration of Competing Interest No conflict of interests, Non sponsored., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Purpose of Review: The incidence of patellar instability in pediatric patients ranges is 50-100 in 100,000 patients per year. Risk of recurrent dislocations however has been cited from 8.6% to 88% depending on individual patient factors. This manuscript highlights the demographical, historical, and anatomic factors associated with recurrent patellar instability following a first-time patella dislocation in the pediatric population., Recent Findings: In recent years, various studies have focused on identifying risk factors for recurrent patellar instability following a primary patellar dislocation. A mix of patient factors, including age of first dislocation, patella alta, elevated tibial tubercle to trochlear groove and trochlear dysplasia have all been noted in the literature, which have helped to develop various scoring tools to predict recurrent dislocation following nonoperative treatment., Summary: Risk of recurrent patellar instability in patients who have previously suffered a patellar dislocation can be due to many factors. These risk factors should be used and applied to a variety of risk scores in order to provide physicians and healthcare providers with a tool to counsel patients and families on their patellar redislocation risk and help guide further management., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Objective: The study aim was to evaluate the clinical outcomes, functional outcomes, and postoperative complications of anchor and Krackow-"8" suture fixation (AS) and K-wire fixation in patients with distal pole patellar fractures., Methods: Twenty-eight patients with distal pole patella fractures between January 2011 and December 2014 were reviewed retrospectively. The anchor and Krackow-"8" suture fixation (AS group) was applied in 10 patients and 18 patients underwent K-wire fixation (K-wire group). The average age of patients was 46.000 ± 19.476 years in the AS group and 47.556 ± 15.704 years in the K-wire group, with comparable demographic characteristics. All patients underwent regular follow-up the operative data and postoperative functional and clinical outcomes were recorded. Complications were recorded by clinical and radiographic assessment. Bostman patellar fracture functional score was used to evaluate knee function after patellar fracture., Results: A total of 28 eligible patients were included in this study. The mean follow-up was similar for the AS and the K-wire groups (P > 0.05). The incision length of AS group was significantly smaller than that of K-wire group (P < 0.05). The incision length of AS group was significantly smaller than that of K-wire group (P < 0.05). The final follow-up on the range of motion of the knee: the average extension lag was similar in two groups (P > 0.05); flexion and flexion-extension angle was slightly better in the AS group than in the K-wire group. The Bostman patella fracture functional score of AS group were better than K-wire group at 3 and 6 months after operation. Four kinds of postoperative complications in two groups, one patient (10%) in the AS group and two patients (11.1%) in the K-wire group had infections. Two (11.1%) cases of nonunion in group K and three patients (16.7%) required re-operation: one due to infection and two due to early implant failure. In the AS group, all distal pole fractures of the patella showed bony union, without loosening, falling, pulling out and nonunion of the fractures 6 months after operation., Conclusions: Anchor and Krackow-"8" suture fixation is an easily executed surgical procedure that can significantly reduce incision length and achieve better surgical outcomes than traditional procedures with regard to postoperative complications, knee function and without requiring a second operation. This technique is an effective operation method for the treatment of inferior patellar pole fractures., (© 2021 The Authors. Orthopaedic Surgery published by Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.)

Objective: To explore the effect of age stratification on patellar height after single-plane high tibial osteotomy of the distal tibial tuberosity (DTT-HTO)., Methods: A retrospective analysis was performed on 110 knee joints undergoing DTT-HTO. Patients were divided into three groups according to age: under 60 years old, 28 cases; 60 to 70 years old, 61 cases; and over 70 years old, 21 cases. All patients were followed up for no less than 12 months, and at each follow-up, short-leg radiographs and whole-leg radiographs were taken. The values of the Caton-Deschamps index (CDI) and Blackburne-Peel index (BPI) of single-short-leg radiographs and the femoral-tibial angle (FTA) and weight-bearing line ratio (WBLR) of whole-leg radiographs were measured before and at the last follow-up. The Lysholm score before and at the last follow-up and the visual analogue scale (VAS) score before and 3 days after surgery and at the last follow-up were calculated. The frequency of classification of the normal-height patella, patella alta, and patella baja before and after surgery was recorded., Results: There were no significant differences in CDI and BPI preoperatively or postoperatively among the three groups ( P > 0.05), and there were no statistically significant differences in FTA and WBLR. There were no significant differences in CDI, BPI, FTA, or WBLR between the three groups before and after the operation ( P > 0.05). The Lysholm score increased from 48.84 ± 10.10 before surgery to 91.96 ± 3.082 after surgery ( P < 0.05); the VAS score decreased from 8.23 ± 0.99 before surgery to 1.93 ± 0.953 at 3 days after surgery and 1.07 ± 0.53 at the last follow-up ( P < 0.01). No significant difference was observed in the incidence of each patellar height classification between the three groups preoperatively and postoperatively., Conclusion: Patellar height is not influenced by DTT-HTO. The age of patients is not a limiting factor for the selection of this surgical procedure. Without affecting the height of the patella, DTT-HTO can effectively reduce pain in the knee joint, restore the function of the knee joint, and delay the progression of patellar arthritis., Competing Interests: The authors declare no conflict of interest., (Copyright © 2022 Tiansong Ding et al.)

Background: As several studies have detected correlations between patellar and femoral trochlear development, this raises the question of whether patellar shape is associated with trochlear developmental outcomes., Methods: Patellar shape and femoral trochlear morphology were retrospectively analyzed in 183 subjects, of whom 61 each were classified as having Wiberg type I, II, and III patellae (groups A, B, and C, respectively). The sulcus angle (SA), lateral trochlea inclination angle (LTA), medial trochlear inclination angle (MTA), lateral facet length (LFL), medial facet length (MFL), lateral trochlear height (LTH), medial trochlear height (MTH), trochlea sulcus height (TH), and lateral-medial trochlear facet distance (TD) were analyzed as a means of evaluating trochlear morphology. Trochlear depth, trochlear condyle asymmetry, and trochlear facet asymmetry were additionally calculated, and differences in trochlear morphology and correlations between trochlear morphology and patellar shape were evaluated., Results: The femoral trochlear parameters of patients in group A differed significantly from those of patients in groups B and C. No significant differences between groups B and C were evident. Patellar shape was positively correlated with LTA, MTA, MFL, trochlear condyle asymmetry, and trochlear facet asymmetry, and was negatively correlated with SA., Conclusions: These data indicated that patellar shape and trochlear morphology are related to one another,which suggest normalized patella morphology surgery and trochlear surgery are better choices for patients with patella instability., Trial Registration: Retrospectively registered., (© 2022. The Author(s).)

A simulated fracture model was used to determine the ability of the medial and lateral patellar facet views in detecting magnitudes of articular displacement. Transverse patellar fractures were simulated in ten patients. Medial and lateral translation of the distal fragment were evaluated in 1 mm increments and rotational malalignment along the longitudinal axis of the patella was evaluated in 5 mm increments. In comparison to the true lateral view, the utilization of the medial and lateral patellar facet views considerably improves detection of occult articular surface malreduction.

Patellofemoral pain is one of the most common symptoms of patients presenting to sports medicine clinics. Obtaining a pertinent history and performing a thorough examination is crucial to identifying the subset of patients with instability who are most likely to benefit from surgical stabilization. A comprehensive radiographic work-up that includes standard radiographs and advanced imaging helps elucidate the diagnosis and provides crucial information for preoperative planning. This article reviews the evaluation, physical examination, and interpretation of radiographic imaging of patients with patellofemoral pain as an introduction to subsequent articles in this issue discussing surgical interventions., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: To confirm whether a novel sagittal patellar angle linear equation used for evaluating patellar height by calculating expected sagittal patellar angle (SPA) at any degree of knee flexion angle is suitable for patients older than 17 years and its reliability compared with other commonly used methods., Methods: From September 2016 to September 2019, a total number of 202 consecutive outpatients' knee lateral X-ray radiographs were retrospectively measured and evaluated using a recently proposed linear equation Y = 1.94 + 0.74 × knee flexion(KF) angle. Patients were divided by ages into ayounger group, whose ages were between 17-49 years, and an older group, whose ages were older than 49 years, which has not been validated in the original study. Parameters such as KF, SPA, patella and patella tendon length and so on were measured on computer with picture archiving and communication system by two independent observers at an interval of 1 month. Insall-Salvati (IS) index, Caton-Deschamps (CD) index and Y value, correlation coefficients were calculated and compared using SPSS 22.0 software., Results: In the younger group, 143 patients (165 knees) were included, ages were 17-49 (31.62 ± 11.38) years, males/females were 70 (48.95%)/73 (51.05%), left knees/right knees were 83 (50.30%)/82 (49.70%), mean value of Y was 31.50° ± 10.07°, and SPA was 34.38° ± 12.38°, mean value of IS was 1.06 ± 0.17, mean value of CD was 1.04 ± 0.18. While in older group, 59 patients (78 knees) were included, ages were 50-60 (mean 54.61 ± 2.99) years, there were 32 males (54.24%) and 27 females (45.76%), 42 knees were left (53.85%) and 36 knees were right (46.15%), mean values of Y and SPA were 25.90° ± 11.55° and 29.36° ± 14.22°, mean IS index in older group was 1.06 ± 0.18, mean CD index was 1.00 ± 0.16. Intra- and inter-observer reliabilities of Y in younger and older groups were 0.999, 0.999, 1.000 and 0.999, meaning high reliability and reproducibility, but low Pearson's correlation coefficients with IS and CD index were showed as -0.213 and - 0.216 in younger group and - 0.113 and - 0.316 in older group., Conclusions: In patients older than 17 years, the linear equation Y = 1.94 + 0.74 × KF is a reliable and practical method to evaluate SPA regardless of age and knee flexion angle, but has weak correlation coefficients with the IS and CD index., (© 2021 The Authors. Orthopaedic Surgery published by Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.)

Objective: To assess the ability of texture features for detecting radiographic patellofemoral osteoarthritis (PFOA) from knee lateral view radiographs., Design: We used lateral view knee radiographs from The Multicenter Osteoarthritis Study (MOST) public use datasets (n  = 5507 knees). Patellar region-of-interest (ROI) was automatically detected using landmark detection tool (BoneFinder), and subsequently, these anatomical landmarks were used to extract three different texture ROIs. Hand-crafted features, based on Local Binary Patterns (LBP), were then extracted to describe the patellar texture. First, a machine learning model (Gradient Boosting Machine) was trained to detect radiographic PFOA from the LBP features. Furthermore, we used end-to-end trained deep convolutional neural networks (CNNs) directly on the texture patches for detecting the PFOA. The proposed classification models were eventually compared with more conventional reference models that use clinical assessments and participant characteristics such as age, sex, body mass index (BMI), the total Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and tibiofemoral Kellgren-Lawrence (KL) grade. Atlas-guided visual assessment of PFOA status by expert readers provided in the MOST public use datasets was used as a classification outcome for the models. Performance of prediction models was assessed using the area under the receiver operating characteristic curve (ROC AUC), the area under the precision-recall (PR) curve -average precision (AP)-, and Brier score in the stratified 5-fold cross validation setting., Results: Of the 5507 knees, 953 (17.3%) had PFOA. AUC and AP for the strongest reference model including age, sex, BMI, WOMAC score, and tibiofemoral KL grade to predict PFOA were 0.817 and 0.487, respectively. Textural ROI classification using CNN significantly improved the prediction performance (ROC AUC = 0.889, AP = 0.714)., Conclusion: We present the first study that analyses patellar bone texture for diagnosing PFOA. Our results demonstrates the potential of using texture features of patella to predict PFOA., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Patella alta is described as abnormally high-riding patella in relation to the femur, the trochlear groove, or the tibia with decreased bony stability. Patella alta represents an important predisposing factor for patellofemoral instability. Different measurement methods are used to define patella alta. Despite the clinical importance of patella alta, there is only limited consensus on cutoff values, indications for treatment, and ideal correction. In addition, the impact of patella alta on other risk factors for lateral patellar instability is significant. This must be considered when assessing clinical complaints and choosing the best individual treatment. Combined surgical interventions may be necessary., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: To improve postoperative outcomes in patients with closed patellar fractures using a new method of surgical treatment., Material and Methods: The authors proposed a new method of patellar osteosynthesis. Technique of osteosynthesis is described, and surgical scheme is presented. Treatment outcomes were analyzed in 68 patients with closed patellar fractures. The control group consisted of 34 patients who underwent Weber osteosynthesis. The authors assessed clinical and radiological data. Moreover, clinical example of a patient with traumatic closed patellar fracture and illustrations of surgical treatment are presented., Results: Clinical data indicate the advantage of treatment in the main group.

Purpose: The purpose of our study was to evaluate clinical outcomes and return to sports after medial unicompartmental knee arthroplasty (UKA) in middle-aged active patients with concomitant patella-femoral joint (PFJ) osteoarthritis at time of surgery., Methods: One-hundred and fifty-one patients who underwent medial fixed-bearing cemented UKA, between 2012 and 2015, for medial unicompartmental osteoarthritis of the knee, were retrospectively reviewed with a minimum 5-year follow-up. The mean age at surgery was 54.3 years (range 47 to 60 years). Radiological evaluation of patella-femoral joint (PFJ) osteoarthritis was performed according to Sperner classification to select a control-group (< grade III) and case-group (≥ grade III). The visual analog scale (VAS) for pain and Knee Society score (KSS) was used to evaluate preoperative and final outcomes. Physical activity level before and after the surgery was assessed by the use of UCLA score., Results: One-hundred and thirty-seven patients (89 males and 48 females) were available at last follow-up. The mean follow-up was 6.2 years (range 5.2 to 7.5 years). At last follow-up improvements of VAS and KSS scores revealed not significant correlation with PFJ osteoarthritis. The majority of patients (87.7%) returned to their sports activity after UKA surgery., Conclusions: Improved quality of life and sports activity level resulted in middle-aged, active patients after UKAs. PFJ osteoarthritis showed no significant correlation with poorer outcomes at 5-year follow-up., Level of Evidence: III, multicenter retrospective cohort study., (© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background: The focus of patella maltracking after total knee arthroplasty (TKA) has traditionally been on patella polyethylene damage and failure mechanisms rather than functional outcomes. The purpose of this study was to evaluate the effect of patellar tilt on patient reported outcomes (PROMS) after primary TKA performed with patellar resurfacing., Methods: A retrospective review using a single implant design was performed. Patella tilt was radiographically measured according to a standardized protocol. PROMS related to pain, function, and satisfaction were evaluated preoperatively and at minimum 1-year follow-up., Results: A total of 468 TKAs were included for analysis. Mean age and BMI were 64 years and 35 kg/m 2 ; respectively while 63% of patients were female. The median follow-up period was 12.7 months. Overall, patellar tilt was corrected from a median of 5.0 degrees preoperatively to a median of 3.0 degrees postoperatively. Preoperative, postoperative, and the change in patellar tilt had no significant effects on PROMS at minimum 1-year follow-up (p ≥ 0.092). Satisfaction in knee function while getting out of bed was higher for patients with approximately the same patellar tilt before and after TKA compared to patients with an increase in lateral patellar tilt (95% vs 80%, p = 0.025)., Conclusions: The range of patellar tilt studied in this cohort had little to no effect on PROMS. However, suboptimal patellar tracking may potentiate edge loading of the polyethylene and contribute to implant damage in the long-term. These results are helpful to focus efforts on the tibiofemoral articulation as the predominant determinant of patient outcomes., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: All potential interests are listed below and outside the current scope of work: DJO Surgical, Osteoremedies (royalties); DJO, Osteoremedies, Kinamed, KCI/3M (paid consultant); Emovi (stock or stock options); DJO (research support); Journal of Arthroplasty, Orthopedics Today (editorial board); ICJR, Knee Society, Hip Society, AAHKS (board member/committee appointments)., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Objective: To evaluate the efficacy of suture anchor combined with double-pulley technique for subpatellar comminuted fractures compared with wire vertical suture and Krachow in the treatment of subpatellar fractures., Methods: Retrospectively selected 48 patients with subpatellar pole comminuted fracture admitted in our hospital from February 2013 to July 2019, 25 patients with double-pulley technique (group A), and 23 patients with vertical wire suture with Krachow suture. Patient age, gender, AT/OTA typing, injury mechanism, follow-up time, surgical time, bleeding volume, mean fracture healing time, and postoperative complications were recorded. The Insall-Salvati index immediately and 6 weeks after surgery. Bostman scores and knee activity were recorded at each follow-up, and month 12 was taken as the final result., Results: Time of surgery in group A (46.52 min) was significantly shorter than in group B (76.30 min). Intraoperative bleeding in group 15.1 ml, B, group 15.9 ml. Both incisions healed in stage I, averaging clinical healing of patella fracture within 10 weeks. There was no significant difference in mean Bostman score and knee activity at month 12 (group A: 28.4, 124.8°; group B: 28.1, 125.7°). There was no significant statistical difference in the Insall-Salvati index immediately or 6 weeks between the two groups. Group B patients had two wire fractures, fracture healing and the wire removed one year after surgery, and the remaining patients had no complications such as internal fixation loosening, fracture, delayed healing, or nonhealing of fracture., Conclusion: Compared with the treatment of subpatellar fracture with wire vertical suture and Krachow method, suture anchor with double-pulley technique has short operation time, reliable fixation, and less complications. Patients can have early functional exercise and good knee function recovery without secondary surgery. It can be considered as an alternative therapy for this fracture and deserves clinical adoption and promotion., Competing Interests: The authors have no relevant financial or nonfinancial interests to disclose., (Copyright © 2021 Hang Yu et al.)

Multipartite (or bipartite) patella is a developmental anomaly that occurs in 2%-6% of individuals. In 50%, the variant is bilateral. Multipartite patella is usually an asymptomatic condition. Quadriceps tendon rupture is also a rare entity occurring mostly in men aged >40 years and usually results from an acute eccentric quadriceps contracture. The authors present a case of a patient with bilateral multipartite patellae that sustained bilateral multipartite avulsions as well as an associated unilateral quadriceps tendon rupture. This constellation of injuries has never been reported in the literature. The patient was treated with excision of the multipartite patella fragments and quadriceps tendon repair on the side with the extensor mechanism disruption. He was treated non-operatively for the contralateral lower extremity multipartite patella avulsion. This report, along with a thorough review of the literature, serves to demonstrate the clinical and radiographic characteristics of this unusual injury., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Osteochondral fractures of the knee occur frequently after acute patellar subluxation or dislocation. They can be challenging to manage because of the difficulty in diagnosing and treating these injuries in a timely fashion, in addition to choosing the optimum fixation method. This review presents the background, considerations for patient evaluation, and the best treatment options available for osteochondral fractures., (Copyright © 2021 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons.)

Purpose: The purpose of this study was to evaluate the long-term clinical and radiographic outcomes of partial patellectomy (PP) in patients with patella comminuted distal pole fractures., Methods: Seventeen patients who were diagnosed with patella comminuted distal pole fractures and underwent PP procedures were retrospectively included between January 1995 and January 2005. We collected patient demographics and data on the mechanism of injury, time to surgery, fracture type, follow-up time, and post-operative complications (infection, patellofemoral arthritis, and stiffness). At the final follow-up, functional outcome was evaluated by the range of motion (ROM) and the Bostman Scoring System. Quadriceps strength was evaluated by using an isokinetic dynamometer to measure peak torque, and patellar height was evaluated by the Insall-Salvati (IS) ratio in lateral knee radiographs. The average follow-up period was 14.6 years (range, 11-19 years)., Results: We analyzed 17 patients (AO/OTA 34-A1), with an average age of 59.8 years (range, 43-76 years). According to the Bostman grading scales, final functional outcomes were excellent in 11 (64.7%) and good in six (35.3%) patients. All patients had full knee extension, and the average ROM was 125.1° (range, 121.4-129.3°). The average peak torque of the injured knee was 103.2 ± 9.7 Nm, and that of the uninjured opposite side was 108.3 ± 7.6 Nm, with no significant difference (p > 0.05). Furthermore, no postoperative complications, such as infection, posttraumatic osteoarthritis, or stiffness, were observed. Compared to the uninjured knee, the IS ratio of the injured knee was 0.76 ± 0.13, indicating that the patellar height was decreased, which meant patella baja., Conclusions: The PP procedure for patella comminuted distal pole fractures is a safe, simple, and reliable technique that can provide good long-term clinical outcomes even with decreased patellar height and could be a satisfactory alternative treatment option when anatomical reduction is difficult., (© 2021. SICOT aisbl.)

Objective: To assess the clinical and radiological results of patellofemoral osteochondral lesions treated with microfractures associated with a chitosan scaffold., Design: A retrospective observational analytical study was performed. Fifteen patients with full-thickness patellofemoral osteochondral lesions were included. Quantity and quality of the reparation cartilage was assessed with the MOCART 2.0 score on a postoperative magnetic resonance imaging (MRI), and clinical outcomes were evaluated with pre- and postoperative Kujala score tests. Shapiro-Wilk test for normality was applied as well as Wilcoxon's signed rank test and Kruskal-Wallis H test for clinical scores within subjects and patella versus trochlea subgroups comparisons. Analysis of variance test was used for imaging subgroups comparison, with P < 0.05 defined as statistical significance., Results: Mean follow-up was 33.36 months (range 24-60 months). Postoperative Kujala scores improved an average of 19 points compared with the preoperative state (SE = 17.6; P < 0.001). No statistical difference was found through the clinical location assessment ( P = 0.756), as well as the cartilage imaging assessment ( P = 0.756). The mean MOCART 2.0 scale was 67.67 (range 50-85)., Conclusions: Treating full-thickness patellofemoral osteochondral lesions with microfractures associated with a chitosan scaffold proved to be effective regarding defect filling and symptomatic improvement.

Objectives: Chondral fractures are focal cartilage lesions without osseous attachment, most commonly seen in adolescent knees. They have limited capacity for intrinsic healing and traditional treatment has been removal of loose fragments. However, case reports of successful healing after fixation indicate that repair of the joint surface is possible. We wanted to evaluate the outcome in a cohort of patients who underwent fixation of acute chondral fractures in the knee., Design: Patients treated with fixation of a chondral fracture in the knee at our institution were invited to participate in a follow-up study. The mechanism of injury, fragment properties and complications were registered. Patients completed KOOS (Knee Injury and Osteoarthritis Outcome Score) and Lysholm questionnaires and performed a validated single leg hop test. Magnetic resonance imaging (MRI) was used to assess healing of the defect and the quality of the cartilage., Results: Ten patients with a median age at surgery of 15 years (12-17 years) and median follow-up of 5 years (2-9 years) were assessed. The lesions were located on the patella ( n = 7), the trochlea ( n = 2), and the lateral femoral condyle ( n = 1). Median lesion size was 250 mm 2 (1.9-6.0 cm 2 ) All patients were treated within 2 months of injury (4-58 days). All patients returned to preinjury level of sports and MRI showed retained fragments that integrated well with surrounding cartilage at follow-up. Mean Lysholm score at follow-up was 90 (73-100)., Conclusion: Fixation of traumatic chondral-only fragments using bioabsorbable implants may result in successful healing in adolescent patients and should be considered a treatment option in acute injuries.

Objective: In order to appreciate the roles articular cartilage of sesamoid bones and sesamoid fibrocartilage play in anatomy and pathology, the articular cartilage of the patella ( n = 4) and suprapatella ( n = 4) (a sesamoid fibrocartilage) of 12 to 14 weeks old New Zealand rabbits were studied qualitatively and quantitatively., Design/method: The intact knee joints and block specimens from the joints were imaged using microscopic magnetic resonance imaging (µMRI) at a 97.6-µm pixel resolution for the former and 19.5-µm resolution for the latter. Histological sections were made out of the µMRI-imaged specimens, which were imaged using polarized light microscopy (PLM) at 0.25-, 1-, and 4-µm pixel resolutions., Results: The patella cartilage varied in thickness across the medial to lateral ends of the sesamoid bone with the central medial aspect slightly thicker than the lateral aspect. The suprapatella fibrocartilage decreased proximally away from the knee joint. Quantitative results of patellar cartilage showed strong dependence of fiber orientation with the tissue depth. Three histological zones can be clearly observed, which are similar to articular cartilage from other large animals. The sesamoid fibrocartilage has one thin surface layer (10 µm thick) of parallel-arranged structured fibers followed immediately by the majority of random fibers in bulk tissue. T2 relaxation time anisotropy was observed in the patellar cartilage but not in the bulk fibrocartilage., Conclusion: Given the different functions of these 2 different types of cartilages in joint motion, these quantitative results will be beneficial to future studies of joint diseases using rabbits as the animal model.

Background: Trochlear dysplasia (TD) is a key predisposing risk factor for patellar instability (PI) and lateral patellar dislocation (LPD) injuries. It is useful to understand the reliability of radiographic findings of TD and the accuracy of knee radiographs in diagnosing patients with recent LPD., Purpose: The purposes of our study are to evaluate the inter-rater reliability of specific radiographic signs of PI and staging of TD between radiologists and orthopedic surgeons, and to identify which findings are associated with recent LPD., Methods: This retrospective study comprised 336 patients aged 8 to 18 who obtained knee radiographs over a 3-year period. Two radiologists and two orthopedic surgeons, blinded to patient history, examined radiographs for indicators of PI. Using data from 19 confirmed LPD cases and 317 controls, inter-observer agreement (kappa, Pearson's correlation coefficient) was assessed, as was the odds ratio for likelihood of LPD., Results: There was nearly perfect agreement between radiologists for patella-tendon ratios (Pearson's correlation coefficient 0.8377, P < 0.0001) and discrimination between normal knees and high-grade TD (kappa 0.9213, P < 0.0001). There is fair agreement between radiologists and surgeons distinguishing between normal knees and high-grade TD (kappa 0.5843, P < 0.0001). Lateral knee radiographs interpreted as high-grade TD were highly predictive of LPD (odds ratio 7.58-54.8) among all readers., Conclusions: There is high agreement between radiologists when evaluating lateral knee radiographs for signs of TD, validating the results of prior literature. Radiographic findings TD, patella alta, and effusion are variable predictors of recent LPD, greatest among patients with TD., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

Purpose: Despite the comprehensive literature on the anatomical risk factors for patellar dislocation, knowledge on the risk factors for subsequent osteochondral fracture (OCF) remains limited., Methods: Magnetic resonance imaging was used to compare measures of patellofemoral anatomy in patients with OCF after patellar dislocation and propensity score matched patients without OCF. For differing measures, limit values showing a 50% probability for the occurrence of OCF were calculated using predictive logistic regression modelling. Proportions of abnormal measures in the groups were compared using Chi-square test. The association of anatomical measures with OCF location was examined by comparing subgroup mean values in the different OCF locations., Results: Propensity score matching provided a total of 111 matched pairs of patients with OCF and patients without OCF. The patients with and without OCF differed in patellotrochlear index (PTI; 0.54 [95% CI 0.52-0.57] vs. 0.47 [95% CI 0.45-0.49]; p < 0.001), tibial tubercle-posterior cruciate ligament distance (TT-PCL; 21.6 mm [95% CI 21.0-22.3 mm] vs. 20.5 mm [95% CI 20.0-21.1 mm]; p = 0.013), trochlear depth (2.5 mm [95% CI 2.3-2.7 mm] vs. 3.0 mm [95% CI 2.8-3.2 mm]; p < 0.001) trochlear facet asymmetry ratio (0.54 [95% CI 0.51-0.57] vs. 0.43 [95% CI 0.42-0.45]; p < 0.001) and trochlear condyle asymmetry ratio (1.04 [95% CI 1.03-1.04] vs. 1.05 [95% CI 1.04-1.05]; 0.013. Thresholds for increased OCF risk were > 0.51 for PTI  > 21.1 mm for TT-PCL < 2.8 mm for trochlear depth > 0.48 for trochlear facet asymmetry ratio and < 1.04 for trochlear condyle asymmetry ratio., Conclusion: In patients with OCF after patellar dislocation, trochlear configuration and patella vertical location were closer to normal anatomy, whereas patella lateralization was more severe when compared to patients without OCF. These anatomical factors contribute to the risk of OCF during patellar dislocation., Level of Evidence: III., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)