Summary

Preoperative Anterior Tibial Subluxation associated with Medial Meniscus injury and influenced knee stability after ACL Reconstruction.

Abstract

Purpose

The purpose of this study was to investigate whether preoperative anterior
tibial subluxation (ATS) with anterior cruciate ligament (ACL) deficient knees influences
knee stability after ACL reconstruction.

Methods

In this prospective cohort study, 46 patients who had unilateral ACL injury and underwent anatomic double-bundle ACL reconstruction using semitendinosus tendon were included. Before surgery, we took a true lateral radiograph under general anesthesia with both knees in full extension and evaluated the intersectional point of the extension line of Blumensaat’s line (B line) and the tibial plateau. We measured both the length from the tibial anterior margin to the intersection point (A) and the anteroposterior length of the tibial plateau (B). The roof plateau intersection ratio was calculated as follows: Intersection ratio = A/B × 100 (%). The patients were designated as the positive ATS group if the intersection ratio of injured knee was 5% or more anterior compared to uninjured knee, as negative ATS group if it was less than 5% anterior compared to uninjured knee. To evaluate the factors associated with preoperative ATS, we investigated each patient’s age, sex, time from injury to surgery and concomitant meniscus injury. One year after surgery, we evaluated the side-to-side difference in anterior tibial translation on stress radiographs, as well as rotational stability by the pivot-shift test. We compared postoperative knee stability between the groups.

Results

There were 13 patients in the positive ATS group and 33 patients in the negative ATS group. The postoperative mean side-to-side difference was 4.1 ± 2.2 mm for the positive ATS group and 1.8 ± 2.6 mm for the negative ATS group, a significant difference (P < 0.01). The positive ratios of the pivot-shift test were significantly different between the positive ATS and negative ATS groups (46% vs 12% P<0.01). Concomitant medial meniscus injuries were seen in 8 of 13 knees in the positive ATS group and 6 of 33 knees in the negative ATS group, and incidence of concomitant medial meniscus injury was significantly higher in the positive ATS group (P = 0.03).

Conclusion

Our study suggested that preoperative ATS with ACL deficient knees associated with concomitant medial meniscus injury and influenced anterior and rotational knee stability after ACLR. Further clinical research is needed to investigate whether the treatment for concomitant meniscus injury and the reconstruction for extraarticular ligament (ex. Anterolateral ligament) with ACL deficient knees having preoperative ATS make postoperative knee stability improve.