Summary

The enlargement ratio of femoral bone tunnel after PCL reconstruction was significantly high compared with the ratio of tibial bone tunnel. The bone tunnel enlargement was not associated with the posterior knee instability and clinical outcome.

Abstract

Introduction

The ideal treatment for posterior cruciate ligament (PCL) injuries is controversial, but the indication of operative treatment has increased recently because of the advances of surgical technique. Among many surgical options, the most commonly used reconstruction method for PCL injury is the transtibial technique. However, the clinical outcome of this reconstructive procedure remains inconsistent. The purpose of this study is to analyze the relationship between bone tunnel enlargement after PCL reconstruction and posterior knee laxity.

Method

Twenty patients who underwent arthroscopic PCL reconstruction using multi-stranded autogenous semitendinosus and gracilis tendons between November 2011 and March 2016 were retrospectively enrolled in this study. In our department, we perform single-bundle PCL reconstruction with remnant preserving technique. The patients were consisted of 17 men and 3 women, mean age was 38 years at the time of surgery. The cross sectional area of the femoral and tibial bone tunnels (5mm inside from the bone tunnel opening) was evaluated using CT imaging at early postoperative period (less than one month after surgery) and at middle period (around one year after surgery), then an enlargement rate was calculated . The posterior laxity at one year after surgery was measured by the radiographic gravity sag view, posterior stress radiography, and the Kneelax-3. Clinical outcomes were evaluated using Lysholm score, then the relations between tunnel enlargement and clinical outcome were analyzed. Statistic analysis were performed using the Wilcoxon signed rank test.

Results

The cross sectional area of the femoral bone tunnel expanded from 78.5 mm2 at early postoperative period to 94.5 mm2 at middle postoperative period. On the other hand, the cross sectional area of the tibial bone tunnel expanded from 78.5 mm2 at early postoperative period to 94.5 mm2 at middle postoperative period. The enlargement ratio of femoral bone tunnel (20.7±8.8%) was significantly high compared with the ratio of tibial bone tunnel (10.8±5.2) (P<0.05). The side-to-side differences in posterior knee laxity was 2.9mm in posterior stress radiography, 2.1mm in radiographic gravity sag view, and 2.1mm in Kneelax-3. Significant relationship was not found between degree of the expansion of the bone tunnel and posterior knee laxity. Lysholm score was improved from 73.7 to 91.5, but significant relationship between clinical outcome and the bone tunnel enlargement was not found, too.

Conclusions

Bone tunnel enlargement was confirmed on both femoral and tibial bones after PCL reconstruction, but the enlargement ratio of femoral bone tunnel was significantly high compared with the ratio of tibial bone tunnel. The bone tunnel enlargement was not associated with the posterior knee laxity and clinical outcome. Further examination is necessary to identify the factor influencing the bone tunnel expansion.