Background

Anterior Cruciate Ligament (ACL) injuries often damage the posterior horn of the lateral meniscus (PHLM). While structural lesions are easy to identify during arthroscopy, assessment of PHLM instability may be difficult.

Purpose

The main objective of this prospective multi-center study was to present preliminary results of a comparison between two diagnostic tests: the aspiration and the probing test. The secondary objective was to evaluate the incidence of PHLM instability in a population of ACL injured patients. The hypothesis of this study was that the incidence of PHLM instability is underestimated by the probing test.

Methods

This prospective analysis was performed in three sports medicine centers. Fifty-two consecutive patients operated for a primary isolated ACL reconstruction without multiligament injuries or concomitant osteotomies were identified and included. Preoperative clinical symptoms related to PHLM instability and MRI were collected. The probing and the aspiration tests were consecutively executed according to previously published methods before as well as after all surgical procedures were achieved. The Mc Nemar test was computed to assess the agreement between the 2 diagnostics tests. Significance was set at p<0.05.

Results

Nine out of 52 (17 %) patients presented pre-operative clinical symptoms related to PHLM instability (knee locking or lateral compartment pain). Preoperative MRI revealed 9 (17%) lateral root tears and 4 (8 %) lateral femoral or tibial defects (ICRS = 2). A positive probing test (displacement = 50%) was observed in 21 (40%) patients and a positive aspiration test in 27 (52 %) patients. When the probing test was positive, the aspiration test was always positive. However, in 6 patients (12%) with a positive aspiration test, the probing test was negative. A significant discrepancy could be observed between both tests (p<0.05).
Meniscal repairat was performed in 13 (25 %) patients with an all inside fixation and in 9 patients (17%) with a trans-tibial pull out suture. In all patients with meniscal repair, both a negative aspiration test and a negative probing test could be observed after the repair.

Conclusion

The preliminary results of this study demonstrated that the instability of the PHLM is present in a high percentage of ACL injured patients. A significant discrepancy between instability of the PHLM at probing and with aspiration was also observed. The aspiration test seems superior to the probing test to firmly identify PHLM instability as well as to verify stability after arthroscopic repair.