The effect of arthroscopic partial medial meniscectomy on tibiofemoral stability.

BACKGROUND

There is still little known regarding the effects of meniscus resection size on tibiofemoral stability.

PURPOSE

To determine if partial medial meniscectomy of the posterior horn significantly alters tibiofemoral stability as measured by the anterior-posterior (AP) position and laxity of the medial femoral condyle.

STUDY DESIGN

Controlled laboratory study.

METHODS

Five cadaveric knees were dissected to the capsule, preserving all ligaments and the quadriceps tendon. Each specimen was first tested on a rig where the AP position and laxity of the medial femoral condyle were measured while a range of forces was applied from full extension to 90° of flexion. Magnetic resonance imaging (MRI) at 3 tesla was then performed for baseline measurements of the meniscus before partial meniscectomy. Arthroscopic partial medial meniscectomy aimed at 30% of the posterior horn was then performed, followed by repeat mechanical testing and MRI. The sequence was then repeated for arthroscopic partial meniscectomy aimed at 60% and 100% of the posterior horn of the medial meniscus.

RESULTS

The MRI analysis demonstrated that 22% ± 9% of the original width of the posterior horn was removed at the first resection, 46% ± 11% was removed at the second resection, and the third resection was 100% removal of the posterior horn for all specimens. After 22% resection, no significant difference in AP laxity was observed. A statistically significant increase in AP laxity was observed with 46% resection under a 500-N compressive load compared with the intact meniscus. After full resection, significant increases in AP laxity were observed under a 50-N compressive load compared with the intact and 22% and 46% resections. The 22% resection had similar AP positions as the intact knee, whereas the 46% resection and 100% removal of the posterior horn had statistically further posterior AP positions than the intact knee.

CONCLUSION

Partial medial meniscectomy with ≥46% resection of the original width of the posterior horn significantly altered the AP position of the medial femoral condyle and also increased laxity.

CLINICAL RELEVANCE

These mechanical changes may lead to abnormal cartilage loading and early osteoarthritis.