Purpose: To test the hypothesis that in patients with unilateral patellofemoral instability (PI), the contralateral asymptomatic joints have abnormal morphology and imaging features of osteoarthritis (OA) at four-dimensional (4D) computed tomography (CT).
Materials and Methods: The institutional review board approved this HIPAA-compliant retrospective study. Informed consent was waived. Radiology records were reviewed to identify 25 patients (male-female ratio, 0.56; median age, 20 years; range, 13-43 years) with unilateral PI undergoing 4D CT and 25 age- and sex-matched control patients undergoing multidetector CT. Trochlear groove depth (TGD), tibial tuberosity-trochlear groove (TT-TG) distance, and patellar height ratio (PHR) were determined to compare morphology, and bisect offset (BO) measurements were obtained to compare lateral displacement of the patella between the two groups by using the Wilcoxon rank-sum test. All images were interpreted by trained observers. Tracking patterns of the patellae were determined by obtaining BO measurements at various flexion angles with 4D CT.
Results: In the contralateral asymptomatic joints, TGD (median, 3.0 mm; 95% confidence interval [CI]: 2.5, 4.6; P < .0001), TT-TG (median, 15 mm; 95% CI: 12.7, 18; P = .008), PHR (median, 1.17; 95% CI: 1.09, 1.2; P = .002), and patellar lateral displacement (BO, 85%; 95% CI: 76.2%, 98.2%; P < .0001) were different from measurements obtained in the control group: TGD median, 5.0 mm (95% CI: 2.2, 7.6); TT-TG median, 10.9 mm (95% CI: 3.4, 20.7); PHR median, 0.92 (95% CI: 0.67, 1.36); and BO median, 63% (95% CI: 59%, 68.4%). OA was detected in 40% of asymmetrical contralateral joints (10 of 25). By using 4D CT data, multiple regression analysis demonstrated that TGD (P = .026) and BO measurements obtained at 30° of knee flexion (P = .047) had an association with the presence of OA.
Conclusion: Abnormal morphology and imaging features of OA are relatively common in contralateral asymptomatic joints of young patients with unilateral PI.
Bibliographical notePublisher Copyright:
© RSNA, 2014.