Summary

Second-look arthroscopy showed gap formation at the graft/PLB bone tunnel interface was present in 40 % of the examined knees. Incomplete interface healing as evidenced by this arthroscopic finding was associated with too elliptic aperture shape. In addition, increased long axis of the aperture at surgery lead to higher incidence of postoperative tunnel enlargement.

Abstract

Introduction

It has been recognized that presence of gap at the graft-bone tunnel interface following anterior cruciate ligament (ACL) reconstruction using free tendon grafts indicates incomplete graft-bone healing. In this study, graft-bone healing was examined by second-look arthroscopy, and the shape (dimension) of the bone tunnel aperture was measured on postoperative CT images. We have hypothesized that too elliptic aperture at surgery may interfere with healing at the graft-bone interface.
The purpose of this study was to examine the graft-bone healing at the femoral aperture by second-look arthroscopy, and assess the relationship between the healing status at the aperture and the tunnel geometry evaluated on postoperative CT images.
Subjects and methods
During the study period, a total of 234 knees underwent primary anatomic double-bundle ACL reconstruction using hamstring tendon autografts. Among those knees, complete data of second-look arthroscopy and CT evaluations were available for 54 knees. There were 17 males and 37 females. The mean age of the patients was 23 years with the mean follow-up period of 16 months. Since incidence of gap formation at the aperture has been reported to be higher for the posterolateral bundle (PLB) femoral tunnel, PLB femoral aperture was subjected to the analysis of this study. At surgery, the PLB femoral tunnel was drilled with either outside-in or transportal technique, and the EndoButton-CL was used for femoral fixation.
At second-look arthroscopy, the graft-tunnel interface at the aperture was carefully visualized and assessed for any gap by probing. CT examinations were performed for all knees at one week and one year after surgery. Zio Term 2009, analysis software, was used for three-dimensional imaging analysis of the CT data. Postoperative enlargement of tunnel aperture was evaluated by comparing 1-week and 1-year results. In the data analysis, the relationship between the gap formation at the tunnel aperture and CT-evaluated parameters was statistically assessed.

Results

Second-look arthroscopy revealed graft-bone gap at the aperture in 22 of the 54 knees (40%). CT evaluation at 1 year showed that the long axis of the PLB tunnel aperture enlarged with the ratio of 1.43 compared to the 1-week results. A moderate positive correlation was observed between the standardized long axis dimension of the aperture at one week and the ratio of tunnel widening (r=0.536, p=0.001). The incidence of gap formation at the aperture was significantly higher in knees with more elliptic aperture shape at surgery and correlated with the extent of tunnel aperture enlargement at 1 year.

Discussion

This study showed that graft-bone gap and tunnel enlargement at the femoral PLB tunnel aperture were observed for 40% and 43% of the study subjects respectively. The results of this study suggested that too elliptic tunnel aperture may induce excessive graft-bone motion and synovial fluid inflow at the graft-bone tunnel interface impairing the filling of the healing tissue. Considering this etiologic sequence, it may be preferable to create the bone tunnel with round intraarticular aperture and reduce the bone-graft gap.

Conclusion

Second-look arthroscopy showed gap formation at the graft/PLB bone tunnel interface was present in 40 % of the examined knees. Incomplete interface healing as evidenced by this arthroscopic finding was associated with too elliptic aperture shape. In addition, increased long axis of the aperture at surgery lead to higher incidence of postoperative tunnel enlargement.