Background: The association between patella alta and episodic patellar dislocation (EPD) has been well described, but its pathophysiology is not completely clear. Patella alta causes decreased contact between the patella and trochlea and decreased resistance to lateral translation of the patella. Additionally, increased patellar tendon length may allow pathologically increased coronal plane patellar motion. It may thus be desirable to address the length of the patellar tendon itself rather than just its insertion site.
Hypothesis: Tenodesis of the patellar tendon in association with tibial tubercle distalization in patients with EPD and abnormally long patellar tendons (>52 mm) results in significant reduction in patellar tendon length, prevention of further patellar dislocation, and good knee function at long-term follow-up.
Study Design: Case series; Level of evidence, 4.
Methods: Twenty-seven knees in 22 patients with EPD and patella alta were treated with patellar tendon tenodesis and tibial tubercle distalization. Following tubercle distalization, the patellar tendon was tenodesed into the original location of the tibial tubercle with suture anchors. Changes in patellar tendon length and patellar height were measured radiographically. Any recurrent dislocation was documented, and patients completed an International Knee Documentation Committee (IKDC) subjective form at a mean of 9.6 years (range, 6-14 years) after surgery.
Results: The mean length of the patellar tendon decreased from 56.3 ± 2.7 mm to 44.3 ± 8.6 mm (P < .0001). The Caton-Deschamps index decreased from 1.22 ± 0.17 to 0.95 ± 0.22 (P < .0001), and the Insall-Salvati ratio decreased from 1.42 ± 0.17 to 0.91 ± 0.18 (P < .0001). No patellar dislocations occurred postoperatively. The mean postoperative subjective IKDC score was 75.6 ± 9.5.
Conclusion: Patellar tendon tenodesis and tibial tubercle distalization result in normalization of patellar tendon length, a stable patellofemoral joint, and good long-term knee function in patients with patella alta and EPD.
Background: It is not known whether nonisometric femoral graft attachment diminishes the effectiveness of medial patellofemoral ligament reconstruction.
Purpose: To determine whether a nonisometric femoral attachment point is associated with differences in contact area and pressure in the patellofemoral joint as compared with an isometric attachment point.
Study Design: Controlled laboratory study.
Methods: Eleven cadaveric knees were amputated and secured in a loading fixture. The quadriceps tendon was clamped 5 cm above the proximal pole of the patella and fixed to a plate. Colinear compressive forces were applied. Forces were set to achieve isometric quadriceps moments at 30°, 45°, 60°, and 90° of knee flexion. Contact areas and pressures were measured using a sensor system. Initially, isometric reconstruction was done using the known isometric femoral attachment point of the posterior medial epicondyle. The attachment was then revised in each specimen to the known nonisometric femoral attachment of the adductor tubercle.
Results: Before medial patellofemoral ligament reconstruction, average facet patellofemoral contact area and pressure generally increased with angle of knee flexion. With few exceptions, initial versus postprocedure data and isometric versus nonisometric contact area and pressure data did not differ significantly at any angle tested. Percentage contact area and contact pressure in the medial facet did not differ significantly from the initial percentage for either attachment, and no difference was found in the percentage medial contact area or pressure for isometric versus nonisometric attachment at the angles tested.
Conclusion: Use of the nonisometric attachment point of the adductor tubercle in medial patellofemoral ligament reconstruction did not appear to alter knee contact area or contact pressures as compared with isometric femoral attachment at the posterior medial epicondyle.
Clinical Relevance: In medial patellofemoral ligament reconstruction, patellofemoral contact area and pressure may not be adversely affected by use of the nonisometric femoral attachment point used in this study.
