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Purpose: To describe, in controls and in a population with patellar instability, magnetic resonance imaging values of measurements representing major associated factors for patellar instability (patellar height, trochlear dysplasia, and extensor mechanism alignment), as well as their cutoff values., Methods: In total, 323 knee magnetic resonance imaging scans, 142 with patellar instability and 181 controls without patellofemoral complaints (anterior cruciate, medial collateral ligament, meniscus ruptures or normal) were evaluated. Means, normality values in the control population, ideal cutoff values through receiver operating characteristic curves analysis, and interobserver reliability (intraclass correlation coefficient) were described for a series of measurements., Results: All measurements were statistically different in control and instability patients, except for the patellotrochlear index and tibial tuberosity to posterior cruciate ligament distance. The interobserver intraclass correlation coefficient was good or excellent (above 0.75) only for the patellotrochlear index, patellar tendon-trochlear groove (PTTG) angle, and patellar tilt. The optimal cutoff value for each measurement was: PTTG angle ≥25.3 o with sensitivity (S) of 70% and specificity (E) of 89%, patellar tilt ≥16 o (S: 69% and E: 84%), trochlear sulcus angle ≥153 o (S: 75% and E: 76%), Carrillon ≤12.8 o (S: 62% and E: 87%), PTTG distance ≥11mm (S: 71% and E: 78%), Caton-Deschamps index ≥1.23 (S: 72% and E: 76%) and trochlear bump ≥3.95 mm (S: 76% and E: 65%)., Conclusions: Caton-Deschamps index (≥1.23), trochlear sulcus angle (≥153 o ), ventral prominence of the trochlea (≥3.95 mm), PTTG distance (≥11 mm), PTTG angle (≥25.3 o ), Carrillon angle (≤12.8 o ), and patellar tilt (≥16 o ) presented better diagnostic performance for patellar instability. Patellotrochlear index and tibial tuberosity to posterior cruciate ligament distance were not related to patellar instability. The interobserver reliability of the factors related to patellar instability was excellent only for the PTTG angle and lateral patellar tilt., Level of Evidence: Level III, retrospective case-control study., (Copyright © 2023 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Osteochondral fracture after acute patellar dislocation in teenagers is relatively common (up to 60% of cases of patellar dislocation), but poorly diagnosed. There are several treatments proposed for this type of injury, but none well defined in the literature. A male patient, 13 years old, with a diagnosis of osteochondral fracture of the lateral femoral condyle after acute dislocation of the right patella. He underwent surgical treatment of the chondral injury, which consisted of suturing of the chondral fragment to the cartilage defect and, in a second approach, reconstruction of the medial patellotibial ligament and medial patellofemoral ligament with autologous flexor graft. Currently, the patient has been followed up for 16 months postoperatively for the suture of the chondral fragment and for 8 months for the ligament reconstruction. He has been evaluated through functional scores and T2 weighted magnetic resonance imaging. Acute fixation through direct bone suturing of a purely chondral fragment can be considered in special situations.

Objective: To present the indications, technical aspects, and initial results of the first cases using Endo-Model™ implants in Brazil., Methods: A prospective study was conducted. It included nine patients submitted to a total knee arthroplasty, of which six were primary and three were revisions, using exclusively the Endo-Model™ implant. These patients were followed for an average of 12 months and evaluated with functional scores, such as the Knee injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), and visual analog pain scale (VAS)., Results: There were statistically significant improvements in all scores evaluated in every patient. Only one complication occurred postoperatively (apraxia of the peroneal nerve) and did not require surgery revision., Conclusion: The use of a rotating-hinge implant for knee arthroplasty is a new option for complex cases with severe instability in Brazil; the initial results are satisfactory.