Trochlear contact pressures after anteromedialization of the tibial tubercle.

BACKGROUND: Anteromedialization is recommended for cartilage restoration of patellofemoral defects, with the presumption that it decreases contact pressures across the trochlea. No study has evaluated pressures on the trochlear side of the patellofemoral joint after anteromedialization of the tibial tubercle. HYPOTHESIS: Anteromedialization of the tibial tubercle decreases contact pressure across the trochlea. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were tested by placing an electroresistive pressure sensor on the femoral side of the patellofemoral joint. A validated model of nonweightbearing resisted extension was simulated by loading the extensor mechanism at 89.1 N and 178.2 N. Knees were tested 3 times per load at 30 degrees , 60 degrees , 90 degrees , and 105 degrees . The center of force and pressure across the patellofemoral articulation were compared before and after a reproducible and consistent anteromedialization. RESULTS: The mean center of force shifted medially after anteromedialization at 89.1 N and 178.2 N. At 89.1 N, the mean total contact pressure decreased significantly (P < .05) at all angles, and at 178.2 N, it decreased significantly at 30 degrees , 60 degrees , and 90 degrees of knee flexion. The mean lateral trochlear contact pressure decreased significantly (P < .05) at all flexion angles at both 89.1 N and 178.2 N. The mean central trochlear contact pressure decreased significantly (P < .05) at 30 degrees with the 89.1-N and 178.2-N loads but increased significantly (P < .05) at 90 degrees with the 89.1-N load. The mean medial trochlear contact pressure increased significantly (P < .05) at all flexion angles at 89.1 N and 178.2 N. CONCLUSION: Anteromedialization shifts the contact force to the medial trochlea and decreases the mean total contact pressure. CLINICAL RELEVANCE: Anteromedialization decreases the mean total contact pressure while shifting contact pressure toward the medial trochlea. This study suggests that anteromedialization is appropriate for unloading the lateral trochlea. However, this procedure appears to have minimal benefit on central chondral defects, and it may actually increase the load in patients with medial defects.

Contact pressure at osteochondral donor sites in the patellofemoral joint.

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.

Postoperative pain management after anterior cruciate ligament reconstruction.

This study compared pain and its management in four groups of patients after anterior cruciate ligament (ACL) surgery. Group 1 consisted of primary ACL reconstruction, group 2 primary ACL reconstruction with meniscal repair, group 3 primary ACL reconstruction with meniscal resection, and group 4 revision ACL reconstruction with patellar tendon allograft. Each patient was instructed to record his or her pain level on a visual analog pain scale (VAS) prior to the procedure and for 7 days postoperatively. All patients received a prescribed narcotic to be taken orally as needed every 4-6 hours. Each patient was instructed to taper its use and supplement with non-narcotic as symptoms allowed. The VAS score for all groups peaked at postoperative day 1 and remained elevated at postoperative day 2. At postoperative day 7, the VAS scores for groups 1, 2, and 3 began to show signs of further decline, whereas group 4 persisted at postoperative day 5 levels. A general trend of decreasing narcotic use over time and increasing non-narcotic use was noted in each group; however, these findings were not statistically significant. All four groups had nearly identical mean VAS scores and corresponding narcotic use for each postoperative day despite the differing levels of complexity of surgical intervention in each group.