Computed tomography and magnetic resonance imaging evaluation of patellofemoral instability

Imaging evaluation of patellofemoral joint instability: a review

The multifactorial origin of anterior knee pain in patellofemoral joint disorders leads to a demanding diagnostic process. Patellofemoral misalignment is pointed out as one of the main causes of anterior knee pain. The main anatomical risk factors of patellofemoral instability addressed in the literature are trochlear dysplasia, abnormal patellar height, and excessive tibial tubercle-trochlear groove distance. Diagnostic imaging of the patellofemoral joint has a fundamental role in assessing these predisposing factors of instability. Extensive work is found in the literature regarding the assessment of patellofemoral instability, encompassing several metrics to quantify its severity. Nevertheless, this process is not well established and standardized, resulting in some variability and inconsistencies. The significant amount of scattered information regarding the patellofemoral indices to assess the instability has led to this issue. This review was conducted to collect all this information and describe the main insights of each patellofemoral index presented in the literature. Five distinct categories were created to organize the patellofemoral instability indices: trochlear dysplasia, patellar height, patellar lateralization, patellar tilt, and tibial tubercle lateralization.

Results of arthroscopic medial retinacular release for treatment of medial subluxation of the patella

BACKGROUND

Medial subluxation of the patella is a rare, disabling condition that has iatrogenic and traumatic causation. To date, only open reconstructions have been reported for operative treatment of this condition, but these procedures have a high rate of complications, revisions, and subsequent surgery. This is the first study to present the results of arthroscopic medial retinacular release for treatment of this problem.

HYPOTHESIS

Arthroscopic release will alleviate painful medial patellar subluxation.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Nine knees (7 patients) with painful, recurrent medial subluxation of the patella that occurred spontaneously (2 knees) or after a lateral release (5 knees) or an injury (2 knees) were treated with an arthroscopic medial retinacular release. The retinaculum was released 2 cm medial to the superior pole of the patella down to the anteromedial portal. At a mean follow-up of 2.7 years (range, 1-8 years), all knees were evaluated, and the results were graded according to the Merchant and Mercer rating scale.

RESULTS

The mean age of the patients was 25 years (range, 15-38 years), and the mean duration of the subluxations before surgery was 28 months (range, 6-48 months). In all 7 patients (9 knees), the medial release relieved their medial subluxation and knee pain, and there were 6 excellent and 3 good results. There were no complications or further realignment surgery needed after this procedure.

CONCLUSION

An arthroscopic medial retinacular release will successfully treat painful medial subluxation of the patella.