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Purpose Patellofemoral instability is a common cause of knee pain and dysfunction in paediatric and adolescent patients. The purpose of the study was to evaluate the frequency of patellar dislocations seen in emergency departments (EDs) and the rates of surgical procedures for patellar instability at paediatric hospitals in the United States between 2004 and 2014. Methods The Pediatric Health Information System database was queried for all paediatric patients who underwent surgery for patellar instability or were seen in the ED for acute patellar dislocation between 2004 and 2014. This was compared with the annual numbers of overall orthopaedic surgical procedures. Results Between 2004 and 2014, there were 3481 patellar instability procedures and 447 285 overall orthopaedic surgical procedures performed at the included institutions, suggesting a rate of 7.8 per 1000 orthopaedic surgeries. An additional 5244 patellar dislocations treated in EDs were identified. Between 2004 and 2014, the number of patellar instability procedures increased 2.1-fold (95% confidence interval (CI) 1.4 to 3.0), while orthopaedic surgical procedures increased 1.7-fold (95% CI 1.3 to 2.0), suggesting a 1.2-fold relative increase in patellar instability procedures, compared with total paediatric orthopaedic surgeries. Conclusion This study shows a significant rise in the rate of acute patellar instability treatment events in paediatric and adolescent patients across the country. Surgery for patellar instability also increased over the study period, though only slightly more than the rate of all paediatric orthopaedic surgical procedures. This may suggest that increasing youth sports participation may be leading to a spectrum of increasing injuries and associated surgeries in children. Level of Evidence IV

Recurrent patellar dislocation in combination with cartilage injures are difficult injuries to treat with confounding pathways of treatment. The aim of this study was to compare the clinical and functional outcomes of patients operated for patellofemoral instability with and without cartilage defects.Eighty-two patients (mean age 28.8 years) with recurrent patellar dislocations, who underwent soft-tissue or bony procedures, were divided into two matched groups (age, sex, follow up and type of procedure) of 41 each, based on the presence or absence of cartilage defects in patella. Chondroplasty, microfracture, osteochondral fixation or autologous matrix-induced chondrogenesis (AMIC)-type procedures were performed depending on the nature of cartilage injury. Lysholm, Kujala, Tegner and Subjective Knee scores of both groups were compared and analysed. Complications and return to surgery were noted.With a mean follow up of 8 years, there was a significant improvement observed in all the mean postoperative patient-reported outcome measures of both groups, as compared with the preoperative scores (P 0.05). Comparing the two groups, postoperative Lysholm, Kujala and Subjective knee scores were significantly higher in patients operated without cartilage defects (P 0.05). Three patients operated for patellofemoral instability with cartilage defects underwent patellofemoral replacement subsequently. The odds ratio for developing complications was 2.53 for patients operated with cartilage defects.Although there is a significant improvement in the long-term outcome scores of patients operated for recurrent patellar dislocation with cartilage defects, the results are significantly inferior compared with those without cartilage defects, along with a higher risk of developing complications and returning to surgery.

Most patellar dislocations are associated with disruption of the proximal medial patellar restraints (PMPRs). The PMPRs comprise the medial patellofemoral ligament (MPFL) and medial quadriceps tendon-femoral ligament (MQTFL). Although isolated MPFL reconstruction is the most frequently performed procedure for the surgical management of recurrent dislocation, recent studies have shown that the MQTFL has a synergistic role with the MPFL in resisting lateral patellar displacement close to full extension. It has therefore been suggested that surgical techniques that gain the benefits of both proximal and distal PMPR biomechanical behavior may be best. This article describes an established technique for combined MPFL and MQTFL reconstruction using semitendinosus autograft.

Introduction: Trochlear dysplasia is a known risk factor for patellar dislocations yet normal trochlea development is not well described. This study will define the articular cartilage and subchondral trochlear morphology development in pediatric patients using MRI evaluation. Methods: Retrospective knee MRI review including patients aged 3-16 years with non-patellofemoral related diagnoses. ICD-9/ICD-10 codes identified eligible study patients. Measurements of the trochlea were made based on previously established methods using the axial MRI image just distal to the physis at the deepest portion of the trochlear groove. Three linear (Lateral Trochlear Height (LTH), Medial Trochlear Height (MTH), Central Trochlear Height (CTH)) and three angular (Sulcus Angle (SA), Lateral Trochlear Slope (LTS), Medial Trochlear Slope (MTS)) were made at the Articular Cartilage (AC) and Subchondral Bone (SCB) (Figure 1). Twelve measurements were made independently by two study authors. Interrater reliability was assessed. Trochlea measurements were summarized across age quartiles: 1st (age 5.1 - 8.3y), 2nd (8.3 - 11.5y), 3rd (11.5 - 14.3y), 4th (14.3 - 16.9y). Associations between age and trochlea measures were assessed using linear regression with Huber-White adjusted standard errors. Results: 246 knee MRIs from 230 patients were included in this study. 113 patients (51%) were female while 117 (49%) were male. 116 MRIs (47%) were of the Left knee and 130 (53%) were Right knee. Average patient age was 11.4±3.4 years. Interrater agreement was high (ICC values >0.7). Mean values for measurements are presented by age quartiles (Table 1). LTH, MTH, and CTH showed linear increase with age (range 2 to 2.6 mm per year, p0.05) however LTS and MTS measured at SCB showed significant increases with age (0.6 and 0.9 degrees per year, p0.05) however for MTH, LTH, and CTH, males were found to have a significantly greater growth rate (p

‘Numerous operations have been described for correction of recurrent dislocation of the patella. The number in itself predicates that the problem has not been solved'. This classic discusses the original publication ‘Diagnosis and treatment of recurrent dislocations of the patella' from Trillat A, Dejour H, Couette A. Published in 1964 at the Revue de Chirurgie Orthopedique et Reparatrice de L'appareil Moteur, where the authors described a surgical procedure modifying Elmslie's original surgery for patients with objective patellar dislocations and also for patients with anterior knee pain who had the sign of the ‘baionnette'. Medialisation of the anterior tibial tubercle (ATT) has been known worldwide as the Elmslie-Trillat procedure, but the history of procedure has its roots going back to 1888. The history of the publications of the Elmslie-Trillat technique is really something special. Cesar Roux published in 1888 the original technique that is similar to Elmislie's procedure. In 1944 in London, Trillat met Selddon and became aware about Elmslie's procedure for the ATT medialisation. Back to France, Trillat published and named it as the Elmslie's technique. Later, after the ‘Journees du Genou', the technique was disseminated as ‘The Elmslie-Trillat' procedure. Nowadays, isolated ATT medialisation, the ‘true' Elmslie-Trillat operation, is still occasionally performed. Too few surgeons use these elegant operations largely because the details of the techniques are not taught routinely. This classic section has the objective to encourage young surgeons to learn tibial tubercle transfer operations and the benefits they bring to patients when performed for proper indications.

Purpose: To provide a direct comparison between medial patellofemoral ligament (MPFL) reconstruction and the other medial patellofemoral soft-tissue surgeries in the restoration of the medial patellar restraint after lateral patellar dislocations in the absence of untreated predisposing factors such as high grade trochlear dysplasia, knee malalignment, patella alta or high tibial tubercle-trochlear groove distance. Methods: PubMed, Cochrane-library, Web of Science, and gray literature databases were searched to find all the relevant records. Study selection, data extraction, and risk of bias assessment were performed following the Cochrane and Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Different techniques to treat lateral patellar dislocation in the absence of untreated predisposing factors were compared in terms of redislocation and complication rates, Kujala, Lysholm, International Knee Documentation Committee, and Tegner scores at the short-term (3 years) and long-term (>3 years) follow-up through meta-analyses. Results: Six studies involving 319 knees were included in the meta-analysis. The analyses of redislocation (0.7% vs 2.9%) and minor complication rates (12% vs 9%) showed no significant differences between MPFL reconstruction and other medial soft-tissue surgeries. Significant differences favoring MPFL reconstruction were documented in Kujala and Lysholm scores at short-term (8.6, P

Background: Patellar dislocations are common among youth athletes. A detailed understanding of patellofemoral anatomy is critical to determine patient prognosis and guide treatment and decision making. Recent literature suggests that measures of patella position relative to the trochlear groove may help identify individuals at risk of repetitive dislocations. While these measures were described using MRI, it is plausible that ultrasound imaging can be utilized to provide similar information in a more cost-effective and time-efficient manner. Purpose: To determine intra and inter-rater reliability of two newly described ultrasound-based measures of patella positioning within two novice examiners. Methods: Subjects were seated with the limb supported in full knee extension and neutral rotation. (Figure 1a) The examiners independently gathered all images and were blinded to each other’s measures for the duration of the study. The transducer was positioned transversely, on the anterior aspect of the knee such that the lateral trochlear ridge, center of trochlear groove, and proximal portion of the patellar tendon were all visible in cross-section. (Figure 1b) Two linear measures were obtained, representing the distance from midpoint of the patellar tendon to a) the center of trochlear groove (MPT-CTG) and b) the lateral trochlear ridge (MPT-LTR). Reliability was assessed using intraclass correlation coefficients (ICC). The average of two measures were used for data analysis. There was a minimum of 1 week between assessments for those subjects with repeated testing. Results: A total of 11 subjects (mean age 15.3) without history of knee pathology were included. There were no significant differences (p>0.05) in either measurement between limbs with MPT-CTG and MPT-LTR values (mean±sd) as follows: MPT-CTG right 8.4mm ± 3.0, left 8.4mm ± 3.3; MPT-LTR right 12.2mm ± 2.7, left 11.6mm ± 2.3. For reliability analysis, each knee served as a discrete variable, yielding a total of 22 data points for evaluation. Inter-rater reliability (n=22) was moderate to good for both measures, with ICC values of 0.724 and 0.814 for MPT-CTG and MPT-LTR, respectively. Intra-rater reliability (n=10) was good to excellent with ICC values of 0.913 and 0.794 for MPT-CTG and MPT-LTR, respectively. (Table 1) Conclusions: This new measure of patella positioning demonstrated moderate to excellent reliability and may be a practical, cost-effective alternative to MRI. While it is encouraging that the subjects in this sample demonstrated no side-to-side differences in either measure, future research should focus on establishing criterion validity and reliability amongst individuals with patellar instability. [Figure: see text][Table: see text]

Case A 53-year-old woman presented with a locked knee after an atraumatic hyperextension episode. Imaging showed an anterior tilt of the patella hinging over the superior trochlear margin, consistent with a superior patellar dislocation. The patella spontaneously reduced on an intra-articular injection with 15 mL of lidocaine in normal saline, after which she was able to actively range her knee. Conclusion Superior patellar dislocations are rare and usually result from a sudden forced contraction of the quadriceps, trapping the patella over superior trochlear osteophytes. Reduction is possible through an intra-articular local anesthetic injection, without manipulation of the patella.

Due to his multifactorial aetiology, treating patellofemoral instability can be a challenge for the orthopaedic surgeon. The incidence of patellofemoral instability shows a peak during adolescence, especially from 11 to 14 years old. Several clinical studies focusing on recurrent patellar dislocations in skeletally immature patients have been published, reporting inconsistent or controversial results. Currently, there is a lack of consensus regarding the surgical management of these patients. The purpose of this study is to update current evidence and systematically review indications, treatments, and outcomes of surgical management for recurrent patellar dislocations in skeletally immature patients. A comprehensive review of the literature was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis, the PRISMA Statement. The following electronic databases were accessed in February 2019: PubMed, Scopus, Google Scholar, CINAHL, EMBASE. All the articles treating surgical management for recurrent patellar dislocations in skeletally immature patients were considered for inclusion. For the methodological quality assessment, we referred to the Coleman Methodology Score (CMS). For the statistical analysis, we referred to the unpaired t-test to establish whether the results are statistically significant. The overall CMS resulted in 52.78 points, attesting a satisfactory methodological quality assessment to this systematic review. A total of 21 articles including 623 patients (577 knees) were evaluated. The overall mean age was 13.02 years. The mean follow-up was 46.61 months. The mean Kujala score improved from 58.94 ± 10.38 to 87.07 ± 7.68 points. The Lysholm score reported a pre- and post-operative mean values of 49.54 ± 14.20 and 88.32 ± 8.80, respectively. The mean Tegner Activity Scale scored 4.28 ± 1.22 at baseline, improving to 5.26 ± 0.83 post-operatively. A total of 4.19% of patients incurred into a major complication, while 9.6% sustained a minor one. We observed a total of 89 re-dislocations above 692 treated knees (12%). The main findings of this study are that surgical procedures for skeletally immature patients affected by recurrent patellar dislocations are feasible and effective. Complications and re-dislocations occurred infrequently. It is of fundamental importance to treat precociously these patients in order to reduce the risk of further recurrences, to increase the level of sporting activity and improving the quality of life.

Purpose: Medial patellofemoral ligament (MPFL) surgery combined with trochleoplasty (TP), is often performed to restore the normal patellofemoral biomechanics avoiding recurrent lateral patellar dislocation (LPD) in patients with trochlear dysplasia (TD). However, it is still unclear whether combining TP and MPFL surgery would be more beneficial than performing MPFL surgery on its own. This meta-analysis quantitatively synthesizes and compares published data on the outcomes of recurrent LPD treatment using MPFL surgery without or with TP in patients affected by TD. Methods: A systematic literature search about the treatment of recurrent LPD in the presence of TD was conducted. The primary outcome was redislocation rate, analyzed for different types of TD. Kujala, and IKDC scores, as well as complication rate, were also analyzed through a separate meta-analysis. Results: No statistically significant difference was found in the overall redislocation rate of MPFL surgery without and with TP. There was, however, a statistically significant difference (p < 0.001) in redislocation rate after MPFL surgery without TP between patients with type A or B TD (2.7%) and in patients with type C or D TD (18.6%). In the analysis for every single type of TD, the following results were obtained: redislocation rate of 1.8% in type A, 3.2% in type B, 11.9% in type C, and 7.4% in type D. A statistically significant difference in the complication rate, favouring MPFL surgery without TP, was documented. Both surgical approaches provided a significant improvement with no difference in Kujala and IKDC scores. These results were confirmed when data were analyzed including only patients with type B, C, or D TD, or without additional bone remodelling procedures. Conclusion: Isolated MPFL is as effective as combined TP and MPFL surgery in preventing redislocation and improving clinical and functional outcomes in patients with recurrent LPD and knees affected by moderate TD. However, in case of severe TD, the redislocation rate is lower when TP is performed in combination with MPFL surgery, although with comparable clinical outcomes and a higher risk of post-operative range of motion (ROM) limitation. Level of evidence: Systematic review and meta-analysis, Level IV.

With an incidence of 5.8 per 100,000 per year, patellar dislocations are commonly seen in the emergency department. Surprisingly, there are only a few studies available that focus on the results of the different non-surgical treatment options after first-time patellar dislocation. The aim of this review is to provide an overview of the most recent and relevant studies on the rationales and results of the non-surgical treatment for first-time patellar dislocation. Patellar instability mainly affects young and active patients, with a peak incidence of 29 per 100 000 per year in adolescents. The medial patellofemoral ligament, a main passive restraint for lateral translation of the patella, is torn in lateral patellofemoral dislocations. Treatment of first-time patellar dislocation can be either conservative or surgical. There are two options in conservative management of first-time patellar dislocation: immobilization using a cylinder cast or removable splint, or, second, functional mobilization after applying a brace or patellar tape. The current available literature of conservative treatment after a first-time patellar dislocation is little and of low quality of evidence. Conclusions should be drawn with care, new research focussing on non-surgical treatment is therefore strongly needed. Cite this article: EFORT Open Rev 2019;4:110-114. DOI: 10.1302/2058-5241.4.180016

The medial patellofemoral ligament (MPFL) is the main restraining force in the first 20 degrees of flexion against lateral patellar displacement and is disrupted after patellar subluxation or dislocation. MPFL reconstruction is frequently performed when conservative management fails and the patient has recurrent patellar dislocations. However, a variety of complications have been reported in the literature with this procedure. Internal bracing with suture tape augmentation encourages healing and allows early mobilization. This article describes, with video illustration, MPFL repair with suture tape augmentation.

The acute primary (first-time) lateral patellar dislocation is associated with a high rate of functional disability. There is no consensus as to the choice of surgical or non-surgical treatment for these patients. The aim of this study is to compare the clinical results between the surgical (reconstruction of the medial patellofemoral ligament [MPFL]) and non-surgical treatments for acute primary patellar dislocations. Sixty-nine skeletally mature patients (69 knees) were included in this prospective non-randomized controlled trial. At least one predisposing factor for patellar dislocation (including patella alta, high lateral patellar tilt, trochlear dysplasia, and increased TT-TG distance) was identified in the included patients. Thirty patients were treated surgically with MPFL reconstruction, and the other 39 patients were treated non-surgically. The main outcome variable was patellar redislocation within a two year follow-up period. The Kujala questionnaire was applied for analyzing the pain and the quality of life. The additional surgeries due to patellofemoral problems were also recorded. Patellar redislocation occurred in eight patients in the non-surgical group, while no redislocation occurred in the surgical group (P

Background: First-time lateral patellar dislocations have historically been treated with a nonoperative approach; a clinical tool to predict patients who are most likely to redislocate may have clinical utility. Purpose: (1) To determine if there are discriminating factors present between patients who redislocated their patellas and those who did not after a first-time lateral patellar dislocation and (2) to use this information to develop a model that can predict the recurrence risk of lateral patellar dislocation in this population. Study Design: Case-control study; Level of evidence, 3. Methods: The study population included those with first-time lateral patellar dislocation, magnetic resonance imaging within 6 weeks, and 2-year minimum follow-up. Cohort A was from a prospective study with 2-year follow-up. Cohort B was a prospectively identified cohort with retrospective chart review. Follow-up was obtained clinically or via mail for patients without 2-year clinical follow-up. Results: Sixty-one patients (42%) out of 145 with primary lateral patellar dislocation had recurrent dislocation within 2 years. Stepwise logistic regression analysis demonstrated that skeletal immaturity (odds ratio, 4.05; 95% CI, 1.86-8.82; P = .0004), sulcus angle (odds ratio, 4.87; 95% CI, 2.01-11.80; P = .0005), and Insall-Salvati ratio (odds ratio, 3.0; 95% CI, 1.34-6.70; P = .0074) were significant predictors of redislocation. Receiver operator characteristic curves defined the cut points to be sulcus angle ≥154° and Insall-Salvati ratio ≥1.3. The probability of redislocation based on the presence of factors was 5.8% with no factors present and 22.7% with any 1 factor present, increasing to 78.5% if all 3 factors were present. Conclusion: This model demonstrates a high risk of lateral patellar redislocation when a patient presents with skeletal immaturity as well as magnetic resonance measurements of sulcus angle ≥154° and patellar height as measured by Insall-Salvati ratio ≥1.3. A patient will have a low risk of lateral patellar redislocation with the inverse findings.

Medial patellofemoral complex (MPFC) is considered as the primary medial patellar restraint and has a static, as well as dynamic, component. MPFL reconstruction (MPFL-R) restores only the static component of MPFC, is associated with multiple technical concerns, and has a steep learning curve. Need for physeal sparing techniques and relatively high rates of complications including patella fracture are some other concerns with MPFL-R. We propose a simple procedure for advancement of MPFC onto patella, which is indicated in most of the recurrent lateral instabilities (with a positive lateral glide test result and an intact MPFL on magnetic resonance imaging). The procedure is also indicated in selective acute primary dislocations—those with associated chondral lesions and magnetic resonance imaging–documented isolated patellar side avulsion/injury. MPFC advancement is a more anatomical procedure that also restores dynamic medial checkrein of patella and can be performed even by a novice surgeon. MPFC advancement is devoid of the multiple technicalities of MPFL-R, does not require intraoperative imaging or any postoperative immobilization, and renders complications like donor graft-site morbidity and patella fractures irrelevant. It requires no modifications in patients with open physes and can be performed in isolation or with other procedures as per à la carte principle., Technique Video Video 1 Medial patellofemoral complex advancement using suture anchors in a patient with recurrent lateral patellar instability.

Background:Most patellar dislocations occur in a lateral direction because of a summed lateral force vector and predisposing anatomic risk factors. Medial patellar instability is rare and is a well-recognized iatrogenic complication of an overly aggressive lateral retinacular release. Noniatrogenic medial patellar dislocations are rare. The management of these injuries is not well described.Purpose:To describe the experience of the International Patellofemoral Study Group with patients with noniatrogenic medial patellar dislocation.Study Design:Case series; Level of evidence, 4.Methods:Members of the International Patellofemoral Study Group (N = 64) were surveyed between October 2018 and April 2019. This group was chosen because of its wide referral base and interest in patellar instability. Specialists who had encountered a patient with medial patellar instability were sent a questionnaire inquiring about details of the case, including patient demographics, medical history, level of athletic competition, injury characteristics, and treatment. Cases were confirmed by physical examination records and, in some cases, with findings on advanced radiographic imaging.Results:The survey response rate was 73% (47/64). Three of the 47 specialists (6.4%) reported they had seen a case of noniatrogenic medial patellar dislocation, for a total of 6 cases. Four cases were described as recurrent medial dislocations in the setting of hypermobile Ehlers-Danlos syndrome; 2 were treated nonoperatively, 1 underwent lateral patellofemoral ligament reconstruction, and 1 underwent derotational osteotomies. Two medial-sided patellar dislocations in collegiate athletes were sports-related injuries that required surgical debridement but no ligamentous reconstruction. None of the patients had persistent or recurrent instability at the time of their most recent follow-up.Conclusion:Noniatrogenic medial patellar dislocations are extremely rare. This case review suggests that the treatment of first-time medial patellar instability in patients without known risk factors should follow the same principles as the treatment of lateral instability with no known risk factors, which is nonoperative management. For patients with documented risk factors and recurrence, surgery to address the risk factors may be appropriate.

Patellar instability and associated patellar dislocation can result in significant pain, disability, and associated injuries in young athletes. The patellofemoral joint is a complex articulation with stabilizing restraints, both medially and laterally, that help guide the patella into the corresponding trochlear groove as the knee cycles through an extension-to-flexion arc. In addition to soft tissue injuries, many osseous aberrancies can contribute to patellar instability in young athletes, including trochlear dysplasia, patella alta, and axial and coronal plane abnormalities. There is a role for nonoperative treatment in these young athletes; however, if recurrent or associated injuries are identified surgical intervention is warranted. Correct diagnosis of the underlying cause of the patellar instability is paramount to developing a surgical plan that will yield the most favorable outcome for these young athletes.

Abstract A 68-year-old female suffering from habitual patellar dislocations following a mal-positioned total knee arthroplasty (TKA) was successfully treated with a biplanar closed wedge distal femoral osteotomy (CWDFO) and medial patello-femoral ligament (MPFL) reconstruction. To the best of our knowledge, no such case has been previously described. Our experience with this case suggests that treatment for a patella dislocation following valgus mal-positioning of TKA should be considered positively. Level of evidence V

Background: Medial patellofemoral ligament (MPFL) injuries are common in patients with acute lateral patellar dislocations, but the pattern of MPFL injuries is unclear, especially with respect to patient age. Purpose: The primary aim was to determine the prevalence of MPFL injuries according to the site of injury in patients with acute lateral patellar dislocations. The secondary aim was to compare the site of MPFL injuries in patients aged ≤16 versus >16 years. Study Design: Systematic review; Level of evidence, 4. Methods: A systematic literature search was performed with PubMed, Embase, and CINAHL to identify articles published from January 1, 1999, to May 31, 2019, that examined the site of MPFL injuries in patients with acute patellar dislocations. The study design, sample size, age at injury, technique used for diagnosing MPFL injuries (magnetic resonance imaging, ultrasound, and/or surgery), and prevalence and site of MPFL injuries were extracted from each study. The pooled estimate of the proportion of MPFL injuries at each site was calculated (femur, patella, midsubstance, and combined sites of injury) as well as proportions stratified by age group (≤16 and >16 years). Results: The literature search yielded 420 unique articles, of which 52 were screened for eligibility; of these, 17 were excluded. Thus, a total of 35 articles (2558 patients) were included in the final analysis. The overall prevalence of MPFL injuries was 94.7% (95% CI, 91.2%-96.8%). Most MPFL injuries occurred at the patella (37.1% [95% CI, 30.8%-43.9%]), followed by the femur (36.8% [95% CI, 31.0%-43.0%]), combined sites (25.1% [95% CI, 20.7%-30.1%]), and the midsubstance (15.6% [95% CI, 13.2%-18.4%]). In patients aged ≤16 years, most MPFL injuries occurred at the patella (39.3% [95% CI, 27.9%-51.9%]), and in patients aged >16 years, most MPFL injuries occurred at the femur (47.2% [95% CI, 40.6%-54.0%]). Conclusion: The prevalence of MPFL injuries in patients with acute patellar dislocations varied by site of injury and by age. MPFL injuries at the patella were most prevalent overall and in children and adolescents, and MPFL injuries at the femur were more prevalent in adults.

Injuries around the knee are often high-energy injuries. The anatomy of the distal femoral physis contributes to its stability and hence high energy is required for disruption of this physis. As the distal femur contributes to the majority of the growth of the lower limb, injury to this growth plate has a high incidence of growth disturbance. Supracondylar femoral fractures can be difficult to reduce and fix due to the short metaphyseal segment. Patellar dislocations are commonly seen in adolescents. Patellar fractures are the result of direct or indirect trauma in children. These can be associated with osteochondral fragments and sleeve fractures often seen in children. Mechanisms of injury, associated anatomy and management options for distal femoral fractures, distal femoral physeal injuries and patella injuries are discussed in this article.

Approximately one-third of skeletally mature patients with primary patellar dislocation will experience recurrent patellar instability over time. Because of the multifactorial combination of features contributing to overall stability of the patellofemoral joint, first-time patella dislocation presents a challenge to the treating physician. A detailed patient history, focused physical examination, and appropriate diagnostic imaging are essential for identifying risk factors for recurrent instability. Individual risk factors include young patient age, patella alta, trochlear dysplasia, and lateralization of the tibial tubercle. In combination these factors may pose even greater risk, and recently published predictive scoring models offer clinicians objective criteria to identify patients most at risk for recurrence. In patients at low risk of recurrence, nonoperative management can be effective, with "a la carte" surgical treatments gaining popularity in those with a higher than acceptable risk of re-dislocation.

Osteochondral injuries of the patella occur often in the setting of traumatic patellar dislocations. Early fixation of the displaced fragment(s) is paramount to maintaining the viability of the articular cartilage and the congruency of the patella. Multiple fixation techniques have been described to ensure stable fixation, including wires, screws, and all-suture techniques with both absorbable and nonabsorbable materials. We performed an open reduction and internal fixation of a large traumatic patellar osteochondral lesion using 3 bioabsorbable compression screws. The technique is straightforward and provides compression across the fragments, affording excellent stability, which allows early range of motion and ambulation.

Acute patellar dislocations, most commonly in the lateral direction, carry high risk of recurrent patellar instability. The medial patellofemoral ligament (MPFL) is one of multiple ligaments found surrounding the patella and is one of the primary stabilizers of the patella. Up to 94–100% of patients suffer from medial patellofemoral ligament rupture after first time patellar dislocation.1 Due to a six degree valgus angle between the femur and tibia in the coronal plane along with a similar angle between the trochlear groove and the tibial tubercle, there is a lateral force vector acting on the patella with the contraction of the quadriceps.2 The primary role of the MPFL1 is to resist this lateral migration of the patella and to keep the patella centered within the patellofemoral groove. The MPFL is the primary ligamentous restraint of the patella, providing 50–60% of the restraining force against lateral displacement.3 It is most effective between 0–30° of flexion, with the trochlea becoming the primary restraint to lateral migration beyond this range. The MPFL is most commonly injured during lateral patellar dislocation. This typically occurs when the foot is planted and an internal rotatory force is applied to the flexed knee in valgus.4 It is the most important structure that is injured in cases of acute dislocation of the patella.5

Acute patellar dislocation is a common cause of traumatic hemarthrosis and is associated with multiple anatomical abnormalities including patella alta, trochlea dysplasia, and malalignment of lower limbs. The medial patellofemoral ligament (MPFL) stabilizes the patella in the early flexion or terminal extension and ruptures in most of first-time patellar dislocations. Thorough radiological evaluations of the MPFL and predisposing anatomical properties are required for the planning of management of recurrent instability. Conservative treatment is the mainstay management of first-time patellar dislocation and achieves good to excellent outcome in most of the patients. Surgery is indicated for recurrent patellar dislocations and first-time patellar dislocations complicated by osteochondral injuries or major MPFL injuries with high functional demand. Return to sports requires painless full range of motion and symmetrical muscle strength in addition to focusing on sport-specific training. Home exercise and behavior modifications in ADLs are important to decrease the reoccurrence of patellar dislocation/subluxation.

The medial patellofemoral ligament (MPFL), which is critical for both patellar stability and normal kinematics of the patellofemoral joint, is disrupted in most patellar dislocations. Consequently, MPFL reconstruction is advocated in recurrent dislocations to restore native patellar constraints. Fixation of the MPFL graft to the medial border of the patella can be achieved through various methods, each with its own benefits and drawbacks. We present a technique for MPFL fixation to the patella using all-soft suture anchors, theoretically decreasing the risk of patellar fracture and articular surface violation.

There are multiple etiologies for recurrent patellar instability. While patella alta, an elevated tibial tubercle trochlear groove distance, and prior lateral patellar dislocations with medial patellofemoral ligament (MPFL) insufficiency have been shown to be risk factors for recurrent patellar instability, trochlear dysplasia can result in a significant impediment to normal patellar tracking. With the adequate identification of risk factors, appropriate surgical treatments can be individually tailored to the patient. We present a combined surgical technique of a sulcus-deepening trochleoplasty using knotless suture anchors for fixation, with MPFL reconstruction using gracilis autograft through short, oblique patellar bone tunnels to address severe trochlear dysplasia.

Medial patellofemoral ligament (MPFL) injuries are common in children and young adults. In patients with recurrent patellar dislocations with normal lower-extremity alignment, anatomic reconstruction of the MPFL has been shown to restore patellar stability. We describe a technique that creates an anatomic reconstruction using a dual docking technique into the patella. Our technique is simple and efficacious for reconstructing the MPFL without implant fixation in the patella, allowing a maximal bone-tendon interface for healing.

External torsion of the anterior tibial tubercle (TT), defined as external rotation around a craniocaudal axis with respect to the posterior femoral condylar plane, may induce patellar instability. To our knowledge no studies have focused on this parameter. The present study aimed to perform an MRI analysis of TT torsion. The study hypothesis was that TT torsion correlates with patellar instability and with 3 of its components: tibial tubercle-trochlear groove (TT-TG) distance, axial engagement index of the patella (AEI), and patellar tilt.Four observers performed MRI measurements for 2 groups: 37 patellar instability patients (PI group) with history of at least 2 patellar dislocations, and 50 control patients with meniscal lesion but free from patellofemoral pathology. All measurements were taken from 2 axial slices with the posterior condylar plane as reference.The intra-class correlation coefficient (ICC) was 0.88. TT torsion correlated with patellar instability, with a mean 5.8̊ in controls and 17.9̊ in the PI group (P0.001). There were also excellent correlations between TT torsion and TT-TG distance, patellar tilt and patellar lateralization (measured by AEI), with correlation coefficients greater than 0.85.TT torsion is a reproducible measurement, with excellent ICC. It is significantly correlated with patellar instability, with a discrimination threshold of 11.5̊, and correlations with all 3 components of instability. These statistical correlations enable TT torsion to be added to the list of patellar instability factors. Further studies should determine its biomechanical role and assess the contribution of associating TT derotation to medialization or distalization procedures.III; case-control study.

Background: Patients with recurrent lateral patellar dislocations are often treated with reconstruction of the medial patellofemoral ligament (MPFL). Purpose: To perform a systematic review to evaluate clinical outcomes and the risk of recurrent patellar dislocation after MPFL reconstruction (MPFLR) with autograft versus allograft. Study Design: Systematic review; Level of evidence, 4. Methods: The authors conducted a search of PubMed, the Cochrane Library, and Embase to identify studies comparing outcomes of MPFLR with autograft versus allograft. The inclusion criteria were full-text studies that directly compared clinical outcomes and/or risk of recurrent patellar instability between patients undergoing MPFLR with autograft versus allograft. A quality assessment was performed using the modified Coleman Methodology Score, and risk-of-bias assessment was performed using the Risk Of Bias In Non-randomized Studies–of Interventions and the Cochrane Collaboration tools. Results: Seven studies (1 evidence level 2, 3 level 3, 3 level 4) that met inclusion criteria were identified and included a total of 150 patients who underwent MPFLR with autograft and 193 with MPFLR with allograft. One study found a significantly higher failure rate among patients with autograft, and another study found a trend toward a significantly higher failure rate among patients with autograft. One study demonstrated no significant difference between postoperative tibial tubercle–trochlear groove distance (measured on magnetic resonance imaging scans) in failed versus successful grafts. One study found that patellar tilt angle improved significantly from preoperatively to postoperatively ( P < .001) but there was no difference between the groups. Kujala scores significantly improved for both autograft and allograft groups across studies. Two studies found significant differences in postoperative Kujala scores between the 2 groups, 1 of which found better scores in the allograft group ( P = .0032) and another in which scores were better in the autograft group ( P = .02). Conclusion: Patients undergoing MPFLR with either autograft or allograft can expect to experience improvement in clinical outcomes. Subjective outcomes improved to a similar degree in both groups. Graft failure was more frequently observed in patients with autograft. Allograft may be a better option for MPFLR owing to lower failure rate.

Background:The surgical management of traumatic patellar dislocations in adolescents is associated with a lower rate of recurrent dislocations compared with nonoperative care. However, the attendant cost of surgery and the quality-of-life benefit of a surgical treatment strategy are unclear.Purpose:To compare the cost-utility of 3 management strategies for acute first-time patellar dislocations in adolescents: (1) nonoperative treatment only, (2) initial nonoperative treatment with surgery only for recurrent dislocations, and (3) immediate surgery.Study Design:Economic and decision analysis; Level of evidence, 2.Methods:A 10-year state-transition Markov model was constructed to compare the cost-utility of the 3 index treatment protocols. Utilities used to define health states were derived from a telephone interview of 60 adolescents with a history of acute patellar dislocations. The probability of transition between each health state was informed by the available literature. Direct costs were estimated using a statewide ambulatory surgery database, and indirect costs were estimated based on parental lost productivity. Effectiveness was expressed in quality-adjusted life years (QALYs). The principal outcome measure was the incremental cost-effectiveness ratio (ICER).Results:In the base case for our model, nonoperative treatment only was the least costly ($7300) but also the least effective (5.30 QALYs); initial nonoperative treatment with delayed surgery cost $10,500 for a 5.93 QALY benefit, while immediate surgical treatment cost $17,100 and provided 6.32 QALY benefits. Compared with nonoperative treatment only, initial nonoperative treatment with delayed surgery was associated with an ICER of $5100 per QALY. When immediate surgery was compared with a strategy of delayed surgery, immediate surgery provided incremental benefits at an ICER of $17,000 per QALY. The model was sensitive to the probability of surgical versus nonoperative treatment to achieve a full return to preinjury activity versus an intermediate lower state. When the probability of achieving a full return to preinjury activity with initial nonoperative treatment exceeds 47.5% (compared with 34.2% in the base case), then initial nonoperative treatment with delayed surgery is preferred to immediate surgery. Similarly, when the probability of achieving a full return to full preinjury activity with surgery falls below 51% (compared with 64% in the base case), then delayed surgery after initial nonoperative treatment is preferred.Conclusion:Immediate surgery and delayed surgical treatment are both cost-effective treatment options; however, immediate surgical treatment provides the highest QALY gains within a 10-year time horizon. Our model sensitivity analysis highlights the role of optimizing functional and quality-of-life benefits in the treatment of acute traumatic patellar dislocations. These findings have implications for clinical guidelines and policy decisions relating to adolescent patellar dislocations.

The purpose of this study was to evaluate subjective outcomes after medial patellofemoral ligament (MPFL) reconstructions. Fifty-four knees of 46 patients who received MPFL reconstruction for recurrent patellar dislocations were examined with a minimum follow-up of two years. To assess patient-based outcomes, the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Kujala score were assessed. The mean Kujala score was significantly improved from 64.6 ± 22.1 pre-operatively to 84.7 ± 11.8 post-operatively (P

Background Patellar dislocations account for two percent of all knee injuries with a 17% chance of re-dislocation. There are few validated scores specific to instability. One of these is the Norwich Patellar Instability Score. There has been limited assessment of the validity, floor-ceiling effect and responsiveness of the Norwich Patellar Instability (NPI) Score from an independent centre. The purpose of this paper is to address this limitation. Methods Data from 90 patients referred to a tertiary referral patellofemoral clinic were analysed. All routinely completed data including NPI Score, Kujala Patellofemoral Disorder Score, and demographic outcomes during appointments, up to 36 months following initial clinical assessment was analysed. Convergent validity was assessed by correlating outcomes of the Kujala Patellofemoral Disorder Score to the NPI Score. Effect size (ES) was determined between baseline to 12-month and 12 to 36-month assessments to determine responsiveness. Floor-ceiling effect was evaluated at baseline, 12-month and 12 to 36-month follow-up. Results NPI Score demonstrated good convergent validity to the Kujala Patellofemoral Disorder Score (p Conclusions The NPI Score is a valid and responsive outcome for people with recurrent patellar dislocation.

Adolescents with osteochondral loose bodies after a first-time patellar dislocation are most commonly treated with surgical intervention. However, the ideal method of managing a concurrent medial patellofemoral ligament (MPFL) disruption is still unknown. Recent evidence suggests high failure rates are associated with primary MPFL repair. The purpose of this Technical Note is to describe an alternative surgical technique for managing acute first-time patellar dislocations by using high-strength suture augmentation of the MPFL.

Accurate assessment of the locations of patellar avulsion fractures in acute patellar dislocations is clinically relevant for decision making for treatment. The study aim was to classify the locations of patellar avulsion fractures with a focus on the ligament attachments of medial stabilizing structures. Out of 131 first-time acute traumatic patellar dislocations, 61 patients had patellar fractures. Subsequently, 10 patients with isolated osteochondral fractures of the articular surface in the patella were excluded. Finally, 51 patients (34 females and 17 males, average age: 18.5 years, 95% CI 16.1–20.9) were included in the study cohort. Based on the locations of the patellar attachment, the patients were divided into three groups: the superior group [medial patellofemoral ligament (MPFL) attachment], inferior group [medial patellotibial ligament (MPTL)/medial patellomeniscal ligament (MPML) attachment], and mixed group. In the patellar avulsion group (51 patients), the superior group, mixed group, and inferior group contained 8/51 (16%), 12/51 (24%), and 31/51 (61%) patients, respectively. This study showed that 84% of the patellar avulsion fractures were located in the inferomedial patellar border, which consisted of MPTL/MPML attachments that were clearly different from the true “MPFL” attachment at the superomedial patellar border. In terms of the clinical relevance, the acute surgical repair of MPTL/MPML attachments in the inferomedial patellar border may not sufficiently control the patella if optimal management of the MPFL is not performed. IV.

Congenital (fixed) dislocations and obligatory (habitual) patellar dislocations represent a complex clinical and surgical challenge. Numerous treatment options, offering different perspectives, and surgical solutions are reported in the literature.We implemented the surgical technique principles, originally described by Stanisavljevic, for congenital (fixed) and obligatory (habitual) patellar dislocations, with slight modifications.We retrospectively evaluated the results of group of 12 patients (15 knees), operated between the years 2002 and 2013. The procedure includes extensive subperiosteal quadriceps realignment and soft tissue medial plication, followed by distal realignment through patellar tendon splitting. The outcome measures were patellar stability, knee range of motion, Pedi-IKDC knee function score, and the PODCI global function score.The study group included 12 patients, 9 females and 3 males (15 knees) whose mean age was 5 years 2 months at diagnosis and 7 years 5 months at surgery. Nine patients had an underlying diagnosed genetic background [Down syndrome (n=6), Larsen syndrome (n=2), nail-patella syndrome (n=1)]. The mean follow-up was 46.2 months. Eleven patients, gained stable patella with no recurrence of dislocation. Postoperative knee active extension was improved significantly (P0.0001) for all patients. The average postoperative Pedi-IKDC and PODCI scores were significantly higher (P0.001) among the idiopathic group.These results suggest that the Stanisavljevic procedure principles with modifications, provides an efficient method for treatment of fixed and obligatory patellar dislocation. In our opinion, young age at surgery played an important role in the surgical outcome.Level IV-therapeutic.

Background: The etiology for recurrent patellar dislocations in children with patellofemoral instability (PFI) is not always apparent. Radiographic and other imaging measures help guide the clinician. However, the imaging parameters for pathologic pediatric PFI and the significance of these measures based on severity are not clearly defined. This study compares common imaging measures for PFI in a non-pathologic and known patellar dislocation pediatric population and determines the likelihood of symptoms based on the severity of each individual measure. Methods: An IRB-approved retrospective review of knee MRIs and radiographs at a single pediatric institution identified 108 limbs (102 patients) meeting inclusion criteria. Sixty-nine limbs had no known patellar pathology (control group) and 39 had surgery for recurrent patellar dislocations (surgical group). MRI measures included tibial tuberosity-trochlear groove distance (TT-TG), tibial tuberosity-posterior cruciate ligament distance (TT-PCL), and lateral trochlear inclination (LTI). Radiographic measures included the Caton-Deschamps Index (CDI) and Insall-Salvati Index (ISI). These measures are representative of PFI risk factors, specifically patellar tendon malalignment, trochlear dysplasia, and patella alta. Binomial logistic regression was used to relate the anatomical parameters to the probability of PFI. Results: The surgical and control groups were similar in terms of age, height and weight. The logistic regression analysis indicated that the TT-TG (p=0.001) and LTI (pConclusion/Significance: Comparing pediatric patients with recurrent patellar dislocations to controls, logistic regression analysis suggests the likelihood of PFI correlates with the severity of specific radiographic measures, specifically those representing the degree of patellar tendon alignment (TT-TG) and trochlear dysplasia (LTI). Knowing this correlation can help guide the treatment of PFI in pediatric patients by providing physicians and families with a continuum on which to base their decisions.

Background: The incidence of primary lateral patellar dislocation (LPD) in children aged 9 to 14 years is 0.6 to 1.2 per 1000. Causation is assumed to be multifactorial, including anatomic variants of the patellofemoral (PF) joint that result in a higher risk of LPD. No publication has compared the morphology of the PF joint and anatomic patellar instability risk factors (APIFs) in a primary LPD population versus controls, defining children by skeletal maturity. Purpose: To characterize the PF morphology and APIFs (trochlear dysplasia, abnormal lateral patellar tilt, elevated tibial tubercle–trochlear groove [TT-TG] distance, patella alta) through magnetic resonance imaging (MRI) measurements in skeletally immature children with and without a primary LPD and to identify (potential) distinctive differences between these 2 groups. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A prospective series of 103 skeletally immature children aged 9 to 14 years with an MRI-confirmed primary LPD were matched with a control group of 69 children. The PF morphology and APIFs were assessed during a 2.5-year period with standardized MRI using sagittal and axial views. Results: In the LPD group, 79% had 2 to 4 APIFs compared with 7% in the control group. All major measurements of trochlear dysplasia were significantly different between the 2 groups. The mean central condylar height was significantly higher in the LPD group compared with the control group, resulting in a lower trochlear depth (2.3 vs 4.5 mm, respectively) and higher sulcus angle (156.7° vs 141.1°, respectively). The LPD group had significantly higher values of patellar height, Caton-Deschamps index (1.33 vs 1.15, respectively), lateral patellar tilt (21.1° vs 8.5°, respectively), and TT-TG distance (13.9 vs 9.8 mm, respectively) compared with the control group. The main divergent APIF was trochlear dysplasia (defined as trochlear depth Conclusion: There was a significant difference in mean values of all established APIFs between the children with a first-time LPD and the controls. Trochlear dysplasia was the main APIF, and together with lateral patellar tilt (≥20°), they had the strongest association with LPD.

Summary Patellar dislocations are mainly characterized by a lateral movement of the patella out of the trochlear groove of the femur. Football, American football, basketball and gymnastics are the most common sports to induce patellar dislocations. However, many individual factors can impact the risk of these injuries and influence the treatment strategy. New evaluation methods like the patellar instability severity score, which is based on the individual risk factors, may be helpful to assess the risk for recurrent dislocations and help the medical management. Non-operative treatment is usually preferred for a primary dislocation without major structural risk factors or structural damage. Surgery is recommended mostly for secondary and recurrent dislocations.

Various knee anatomic imaging factors have been historically associated with lateral patellar dislocation. The characterization of these anatomic factors in a primary lateral patellar dislocation population has not been well described. Our purpose was to characterize the spectrum of anatomic factors from slice imaging measurements specific to a population of primary lateral patellar dislocation. A secondary purpose was to stratify these data by sex/skeletal maturity to better detail potential dimorphic characteristics. Patients with a history of primary lateral patellar dislocation between 2008 and 2012 were prospectively identified. Ten MRI measurements were analysed with results stratified by sex/skeletal maturity. A ‘4-factor’ analysis was performed to detail the number of ‘excessive’ anatomic factors within a single individual. This study involved 157 knees (79 M/78 F), and 107 patients were skeletally mature. The measurements demonstrate more anatomic risk factors in this population than historical controls. Patella height and trochlear measurements are the most common ‘dysplastic’ anatomic factors in this population. There were differences based on sex for some patellar height measurements and for TT-TG; there were no differences based on skeletal maturity. Primary lateral patellar dislocation patients have MRI measurements of knee anatomic factors that are generally more dysplastic than the normal population; however, there is a broad spectrum of anatomic features with no pattern predominating. Characterizing knee anatomic imaging factors in the patient with a primary lateral patellar dislocation is a necessary first step in characterizing the (potential) differences between the primary and recurrent patellar dislocation patient. IV.

Background: Whether surgical or nonsurgical management is more appropriate for primary patellar dislocations (PPDs) in adolescents (younger than 18 years) remains controversial. Purpose: To compare the clinical outcomes of surgical versus nonsurgical treatment for adolescents and children with PPDs. Study Design: Systematic review; Level of evidence, 3. Methods: There were 2 reviewers who independently searched the PubMed, Embase, Ovid, and Cochrane databases for English-language studies of randomized controlled trials (RCTs), quasi-RCTs, and observational studies comparing surgical with nonsurgical treatment for PPDs. The primary outcomes were redislocations, the Kujala score, and the Knee injury and Osteoarthritis Outcome Score (KOOS), and the secondary outcome was subsequent surgery. Results: A total of 6 studies were included in our systematic review and meta-analysis. Among patients younger than 18 years, surgery was associated with a lower redislocation rate compared with nonsurgical treatment within 5 years of treatment (risk ratio [RR], 0.58 [95% CI, 0.37-0.91]; P = .02; I 2 = 47%) but not beyond 5 years (RR, 0.80 [95% CI, 0.59-1.07]; P = .14; I 2 = 34%). However, surgery resulted in worse Kujala and KOOS scores compared with nonsurgical treatment. Yet, the treatment difference between the 2 groups tended to decrease over time. Conclusion: The available evidence suggests that for adolescents with PPDs, surgery was superior to nonsurgical treatment in the short term to reduce the redislocation rate but resulted in poorer outcomes of knee function based on the Kujala and KOOS scores. However, the superiority of either surgical or nonsurgical treatment in adolescents did not appear to persist in the long term.

Objectives: Osteochondral fractures occur in 5-15% of cases of acute or recurrent patellar dislocations. In these settings, early surgical intervention with biodegradable fixation nails is recommended to optimize healing. The aim of this study was to determine the incidence of recurrent instability and second surgery following osteochondral fracture fixation with concomitant medial patellofemoral ligament (MPFL) reconstruction. Methods: We conducted a retrospective cohort study of 321 MPFL reconstructions performed by a single surgeon between 2011 and 2019. Thirty-eight knees underwent MPFL reconstruction with osteochondral fixation. Demographic data, surgical details, date of latest radiographic and clinical follow-up, and subsequent surgical procedures were collected. Results: Thirty-seven MPFL reconstructions with osteochondral fracture fixation in 36 patients were performed by a single surgeon from 2011 to 2019 (1 bilateral). The average age at surgery was 14.8 years (range 10.6– 19.6 years). The average length of clinical follow-up was 2.1 years (range 0.3– 5.5 years). The average number of biodegradable fixation nails used was 4.4 (range: 2-8). Twenty-seven (72.9%) fractures were fixed to the patella and 10 were fixed to the lateral femoral condyle or trochlea. There was 1 report of recurrent instability. Ten (27%) patients required a second surgery on the ipsilateral knee, and underwent chondroplasty (n=8), removal of biodegradable fixation nails (n=4), removal of hemi-epiphysiodesis or TTO hardware (n=2), revision MPFL with tibial tubercle osteotomy (n=1), lateral meniscus repair (n=1). The one patient who required revision MPFL reconstruction has juvenile idiopathic arthritis and underwent 3 additional surgeries after the initial MPFL procedure. Eight patients (22%) underwent a second surgery to address cartilage damage or removal of nails. The mean time to second surgery was 40.0 weeks (range:11-82.7). Of the four patients who required removal of nails, the average number of nails initially placed was 7 ± 1.7. This was significantly more than the patients who did not require second surgery related to nail removal (4.1 ± 1.6, p < .05). Conclusion: Approximately 78% of patients undergoing MPFL reconstruction and osteochondral fracture fixation with biodegradable nails showed good fracture healing and patellar stability while 22% went on to require a second surgery. The second surgery most commonly involved debridement of an unhealed portion of the cartilage.

Aims and Objectives: The medial patellofemoral ligament (MPFL) is the most important passive stabilizer of the patella. In recurrent lateral patellar dislocations reconstruction of the MPFL with an autologous tendon transplant is a frequently performed surgical procedure that shows a low redislocation rate between 1%-7%. However, a complication rate of up to 26% and a reoperation rate of 4% has also been observed. The question, therefore, arises which parameter determines MPFL reconstruction failure. Thus, the purpose of this study was to identify reasons for MPFL reconstruction failure with regard to patients’ complaints leading to reoperation. Materials and Methods: Between July 2015 and May 2019 28 patients (M/F 9/19; mean age 27 ± 8 years) with postoperative complaints after MPFL reconstructive surgery had to undergo revision surgery. Preoperative failure analysis included clinical examination (ROM, ReDPAT, J-sign, and Patella-Glide Test) and radiological imaging with regard to anatomical risk factors of patellar instability and MPFL tunnel positioning. Anatomical predisposition was assessed according to Dejour’s classification of trochlear dysplasia, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, patellar height, varus/valgus malalignment and torsional profile. Results: Three major reasons for revision surgery were identified: (1) patellar redislocation, (2) limited range of motion (ROM), and (3) anterior knee pain (AKP). Sixteen of the 28 patients (57%) suffered from recurrent patellar dislocation. Severe trochlear dysplasia (type B/D according to Dejour) (44%), valgus deformity (19%), increased patellar height (19%), and misplaced femoral drill channels (31%) could be identified as risk factors for redislocation. An increased TT-TG (>20mm) or TT-PCL (>24mm) distance could not be observed in any patient in this group. Limited ROM with an average maximum flexion ability of about 92 ± 26° was observed in 10 of the 28 patients (36%), of which 9 patients additionally complained of AKP. Misplaced femoral drill channels (80%), severe trochlear dysplasia (type B/D according to Dejour) (20%) and postoperative decreased patellar height (20%) could be identified as risk factors for postoperative limited ROM. Other reasons for postoperative AKP were increased femoral antetorsion (n=1) and retropatellar cartilage damage (n=2) without any loss of ROM. Conclusion: Recurrent dislocation of the patella, limited ROM and AKP were identified as most common complications after MPFL reconstruction leading to revision surgery. Failures are mainly due to neglected bony risk factors of patellar instability (trochlear dysplasia, patella alta and valgus deformity) and to misplaced femoral drill channels. Appropriate patient selection and an accurate surgical technique appear mandatory for a good clinical outcome when patellar instability is treated solely with an MPFL reconstruction.

Background The medial patellofemoral ligament (MPFL) is an important soft tissue constraint to preventing patellar dislocations in young athletes. The anatomy of the MPFL has been investigated in cadaveric studies and magnetic resonance studies. No studies to date have provided anatomical data of the MPFL on ultrasonography. Purpose To investigate the feasibility of musculoskeletal ultrasonography for the evaluation of the MPFL, and to determine interrater and intrarater reliability for MPFL ultrasound measures. Methods Ten control participants (20 knees) 20 to 50 years underwent ultrasonography performed by 3 researchers (musculoskeletal ultrasound radiologist, athletic trainer/biomechanist, primary care sports medicine physician) from 3 different institutions for interrater reliability testing. Intrarater reliability testing was performed at 2 separate institutions by 4 physicians, each performing the same knee ultrasound protocol on 20 knees in 10 study participants 2 to 3 weeks apart. In total, 180 images were created for interrater reliability, and 480 images for intrarater reliability. Examinations were performed with linear high-frequency transducers (10-18 MHz) with the participant in the supine position and the extremity flexed at 45°. Measurements included ligament length (long axis to ligament) from the patellar to the femoral attachment sites, ligament width (short axis to ligament) at the patellar attachment, and ligament thickness (long axis to ligament) midway between the patella and femur. Mean and SD were calculated for all measurements. Intraclass correlation coefficient (ICC) analysis was used to assess intrarater and interrater reliability. ICC values < 0.40 indicated poor reliability, whereas those between 0.40 and 0.75 indicated fair to good reliability, and those > 0.75 indicated excellent reliability. Results The mean US value for MPFL length was 44.83mm (SD 6.68), mean thickness 2.66mm (SD 0.85), and mean width 11.76mm (SD 2.99). The overall ICC values for interrater reliability testing indicated fair to good reliability for length measures (0.7) and poor reliability for thickness (–0.1) and width (0.3; Table 1.1). Overall ICC values for intrarater reliability indicated fair to good reliability for length (0.5), excellent for thickness (0.9), and poor reliability for width (–0.3; Table 1.2). Conclusions Musculoskeletal ultrasonography is a feasible and reliable office-based method of measuring MPFL length and thickness. These quantitative measures set the groundwork for establishing normative anatomical measures of the MPFL in athletes and establish a protocol for testing and measuring the MPFL using musculoskeletal ultrasonography. Table 1.1. Intraclass Correlation Coefficients (ICC) for testing reliability between physicians (inter-rater). ICC Length Thickness Width Overall 0.708(0.291, 0.898) -0.047(-0.452, 0.442) 0.253(-0.179, 0.652) xx vs xx 0.833(0.562, 0.937) -0.055(-0.312, 0.309) 0.062(-0.389, 0.498) xx vs xx 0.297(-1.246, 0.776) -0.014(-0.385, 0.447) 0.253(-0.130, 0.672) xx vs xx 0.707(0.053, 0.907) 0.032(-2.554, 0.704) 0.286(-0.874, 0.756) *Data analyzed using two-way mixed, absolute agreement analysis. Expected value is shown, along with lower and upper bounds of 95% confidence intervals. Table 1.2. Intraclass Correlation Coefficients (ICC) for test-retest (intra-rater) reliability among individual physicians. Length Thickness Width Overall 0.492*(0.190, 0.681) 0.858(0.772, 0.912) -0.319(-0.056, 0.566) Physician 1 0.589(-0.024, 0.842) 0.400(-0.300, 0.754) 0.386(-0.241, 0.756) Physician 2 0.014(-0.393, 0.447) 0.260(-0.965, 0.722) -0.097(-0.683, 0.432) Physician 3 -0.085(-2.104, 0.604) 0.463(-0.228, 0.786) -1.910(-7.683, -0.027) Physician 4 0.792(0.467, 0.918) 0.634(0.053, 0.857) -0.224(-1.272, 0.435) *Data analyzed using two-way mixed, absolute agreement analysis. Expected value is shown, along with lower and upper bounds of 95% confidence intervals.

Vertical patellar dislocations (VPDs) are a rare event, and even more so among pediatric female patients. There have been less than 30 vertical patellar dislocations reported in the literature since the first in 1844. In this type of dislocation, the patella rotates about its vertical axis with the articular surface facing either medially or laterally. The mechanism of injury for a VPD can be broadly divided into two themes: a twisting injury or direct impact to the medial or lateral edge of the patella. We present a 10-year-old girl with a VPD after experiencing a twisting injury when descending a playground slide. The purpose of this study is to present a case report and review of the literature on vertical patella dislocations, including mechanisms of injury and suggested methods of treatment. We aim to provide a comprehensive understanding of the various categories of patella dislocations to alleviate confusion when classifying patellar dislocations. Furthermore, we provide clear suggestions for reduction methods and techniques with regards to vertical patellar dislocations, including a suggested protocol for an irreducible patella.

With the exponential increase in the arthroscopic treatment of medial patellar instability through lateral sided “capsular” releases, the iatrogenic upsurge of lateral patellar dislocations has become more evident. Although few reports exist detailing the occurrence of this phenomenon due to traumatic or idiopathic etiologies, the vast majority (over 90%) are iatrogenic. Originally described by Kaplan and later by Reider, the lateral patellofemoral ligament (LPFL) constitutes one of the main stabilizers for medial patellar translation. Thus, understanding the anatomy and biomechanics of the LPFL is of utmost importance as reconstruction can potentially restore patellar instability and improve function in cases when this mechanism is compromised. However, few studies have sought to thoroughly describe the intricate anatomy and biomechanics of the LPFL to this end. The purpose of this article was to review the evidence on the anatomy of the LPFL and the lateral retinaculum, its biomechanical behavior, and previously reported surgical approaches to LPFL reconstruction.

Objectives: To determine the prevalence of high patella in adult patients with knee pain, and to correlate patellar height with symptoms of patellar instability, episode of patellofemoral dislocation and anterior pain in the knee; and also verify the concordance correlation between the Insall-Salvati and Caton-Deschamps indices. Method: Cross-sectional study analyzing the medical records of patients with knee pain, using lateral view knee radiographs with 30º degrees of flexion and computed tomography. The values of the Insall-Salvati index and the Caton-Deschamps index were used to determine the patellar height. Results: A total of 756 records were analyzed, resulting in 140 knees studied, 39% men and 61% women. Both indices produced statistically significant associations for the occurrence of high patella and signs of instability and episodes of dislocation, but there was no significant association for anterior knee pain. The Kappa index obtained when analyzing the concordance correlation between the Insall-Salvati index and Caton-Deschamps index points to a regular association between them. Conclusion: Patients with high patella present a higher prevalence of instability. Having a high patella has no significant relationship with the presence of anterior knee pain. The Insall-Salvati and Caton-Deschamps indices demonstrate a regular agreement on the presentation of patellar heights results. RESUMO Objetivos: Determinar a prevalência de patela alta em pacientes adultos portadores de dor no joelho, correlacionar a altura patelar com sintomas de instabilidade patelar e dor anterior no joelho. Verificar índice de concordância entre os índices de Insall-Salvati e Caton-Deschamps. Métodos: Estudo de corte transversal, com análise de prontuários de pacientes portadores de dor no joelho e radiografias em perfil do joelho a 30º graus de flexão e tomografia computadorizada. Usadas as medidas do Índice de Insall-Salvati e Índice de Caton-Deschamps para determinar a altura patelar. Resultados: Foram analisados 756 prontuários, 140 joelhos, 39% de homens e 61% de mulheres. Para ambos os índices obtivemos associações estatisticamente significantes para a ocorrência de patela alta e sinais de instabilidade patelar, entretanto não houve associação significativa para a dor anterior no joelho. O índice Kappa obtido para analisar a relação de concordância entre o Índice de Insall-Salvati e Caton-Deschamps aponta para uma associação regular entre eles. Conclusão: Pacientes portadores de patela alta apresentam maior prevalência de instabilidade na população estudada. Ter patela alta não apresenta relação significativa com a presença de dor anterior do joelho. Os Índices de Insall-Salvati e Caton-Deschamps apresentam concordância regular na apresentação dos resultados das alturas patelares.

Background: The first-line treatment for patellar dislocations is often nonoperative and consists of physical therapy and immobilization techniques, with various adjuncts employed. However, the outcomes of nonoperative therapy are poorly described, and there is a lack of quality evidence to define the optimal intervention. Purpose: To perform a comprehensive review of the literature and assess the quality of studies presenting patient outcomes from nonoperative interventions for patellar dislocations. Study Design: Systematic review; Level of evidence, 4. Methods: The MEDLINE, AMED, Embase, CINAHL, Cochrane Library, PEDro, and SPORTDiscus electronic databases were searched through July 2017 by 3 independent reviewers. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. Study quality was assessed using the CONSORT (Consolidated Standards for Reporting Trials) criteria for randomized controlled trials and the Newcastle-Ottawa Scale for cohort studies and case series. Results: A total of 25 studies met our inclusion criteria, including 12 randomized controlled trials, 7 cohort studies, and 6 case series, consisting of 1066 patients. Studies were grouped according to 4 broad categories of nonoperative interventions based on immobilization, weightbearing status, quadriceps exercise type, and alternative therapies. The most commonly used outcome measure was the Kujala score, and the pooled redislocation rate was 31%. Conclusion: This systematic review found that patient-reported outcomes consistently improved after all methods of treatment but did not return to normal. Redislocation rates were high and close to the redislocation rates reported in natural history studies. There is a lack of quality evidence to advocate the use of any particular nonoperative technique for the treatment of patellar dislocations.

Background: Many factors are involved in causing patellar instability or recurrent patellar dislocations. However, factors affecting the outcomes of anatomic medial patellofemoral ligament (MPFL) reconstruction have not been fully documented. Purpose: To evaluate the rate of recurrent patellar instability after isolated MPFL reconstruction and to elucidate factors affecting the outcomes of isolated MPFL reconstruction using multivariable statistics. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 42 patients (44 knees) who underwent isolated, anatomic MPFL reconstruction using a semitendinosus autograft without any additional patellar stabilization procedures for treating recurrent patellar dislocations were included in this study. All patients were followed for more than 2 years; the mean follow-up period was 3.2 years (range, 2-9 years). Postoperative patellofemoral instability was diagnosed when the patient complained of recurrent patellar subluxations or dislocations or had a positive apprehension sign during follow-up. Preoperative radiographic findings were obtained using plain radiography and computed tomography. Femoral tunnel positions were assessed on postoperative radiographs. The strength of the relationship between postoperative patellofemoral instability and potential risk factors such as preoperative age, sex, body mass index, patellar type, sulcus angle, congruence angle, lateral tilt angle, patellar height, tibial tubercle–trochlear groove (TT-TG) distance, degree of trochlear dysplasia, and femoral bone tunnel position were evaluated by univariate and multivariate logistic regression analyses. Results: At follow-up, 2 knees had experienced a redislocation (4.5%). A positive apprehension sign was still evident in 8 knees (18.2%). Three factors, including the sulcus angle, the congruence angle, and trochlear dysplasia, were extracted by single linear regression analysis. Univariate logistic regression analysis showed that the sulcus angle (odds ratio [OR], 1.11; 95% CI, 1.01-1.22; P = .04) and trochlear dysplasia (OR, 3.04; 95% CI, 1.39-6.63; P = .01) were associated with postoperative patellofemoral instability. Trochlear dysplasia was independently associated with postoperative patellofemoral instability by multivariable logistic regression analysis ( P < .05). An increased TT-TG distance exerted a significant effect on the outcomes of MPFL reconstruction, particularly in patients with type D trochlea. Conclusion: Severe trochlear dysplasia is the most important predictor of residual patellofemoral instability after isolated MPFL reconstruction. In addition, an increased TT-TG distance affected the outcomes in patients with type D trochlea. Additional patellar stabilization procedures should be considered for patients with severe trochlear dysplasia and an increased TT-TG distance.

While a significant research has gone into identifying patients at highest risk of recurrence following primary patellar dislocation, there has been little work exploring the outcomes of patients who do not have a recurrent patellar dislocation. We hypothesize that patients without recurrent dislocation episodes will exhibit significantly higher KOOSs than those who suffer recurrent dislocations, but lower scores than published age-matched normative data. A retrospective review of patients with nonoperatively treated primary lateral patellar dislocations was carried out, and patients were contacted at a mean of 3.4 years (range 1.3–5.5 years) post-injury. Information regarding subsequent treatment and recurrent dislocations along with patient-reported outcome scores and activity level was collected. One hundred and eleven patients (29.8 %) of 373 eligible patients agreed to study participation, seven of whom were excluded because they underwent subsequent patellar stabilization surgery on the index knee. Seventy-six patients (73.1 %) reported no further dislocation events, and the mean KOOS subscales at follow-up were: symptoms—80.2 ± 18.8, pain—81.8 ± 16.2, ADL—88.7 ± 15.9, sport/recreation—72.1 ± 24.4, and QOL—63.9 ± 23.8 at a mean follow-up of 3.3 years (range 1.3–5.5 years). No significant differences in any of the KOOS subscales were noted between these patients and the group that reported recurrent patellar dislocations. Only 26.4 % of the patients without further dislocations reported they were able to return to desired sport activities without limitations following their dislocation. Patients who do not report recurrent patellar dislocations following nonoperative treatment of primary patellar dislocations are in many cases limited by this injury 3 years following the initial dislocation event. Retrospective cohort study, Level III.