BACKGROUND:
The lowest contact pressure point is presumed to be the best site to harvest an osteochondral plug and minimize morbidity.

HYPOTHESIS:
Patellofemoral contact pressures are not uniform and are lowest along the medial patellofemoral articulation.

STUDY DESIGN:
Controlled laboratory study.

METHODS:
Seven cadaveric knees were tested with an electroresistive, dynamic pressure sensor placed onto the femoral side of the patellofemoral joint. The extensor mechanism was loaded with 89.1 N and 178.2 N, and the knee was manually cycled 3 times (0 degrees -105 degrees ) per load. Mean trochlear pressures were calculated.

RESULTS:
Mean contact pressures were greatest in the central trochlea (5.80 kgf/cm(2)), followed by the lateral (2.56 kgf/cm(2)) and medial trochlea (1.60 kgf/cm(2)) at 89.1 N (P < .05). At 178.2 N, pressures increased to 9.47, 5.81, and 2.75 kgf/cm(2), respectively (P < .05). Lateral trochlear pressures decreased moving distally from 1.25 to 0.50 kgf/cm(2) at 89.1 N and 4.57 to 1.29 kgf/cm(2) at 178.2 N.

CONCLUSIONS:
Contact pressures are lowest along the medial trochlea and decrease distally along the lateral trochlea.

CLINICAL RELEVANCE:
Osteochondral plugs from the medial femoral trochlea may be desirable if trochlear size permits. If harvesting from the lateral femoral trochlea, consider harvesting distally near the sulcus terminalis.





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