Anterior Cruciate Ligament (ACL) Tunnel Widening Comparing All-inside and Interference Screw Fixation Technique

Overview

The purpose of this study is to evaluate the incidence and degree of bone tunnel widening between two groups who have undergone anterior cruciate ligament reconstructive surgery. The two groups have undergone different graft fixation methods: an interference screw/suspensory button fixation hybrid technique, and an all-inside suspensory method fixation. Tunnels are created at the time of surgery for graft placement and fixation, but have been known to enlarge post-operatively. Little has been studied on the relatively new all-inside technique. X-rays of the operative knee will be used to assess tunnel width. Secondary outcomes will include clinical evaluation and outcome scoring questionnaires

1. Purpose The purpose of this study is to compare a cohort of patients who have undergone anterior cruciate ligament (ACL) reconstructive surgery performed using either an interference screw fixation and suspensory button fixation hybrid technique, with another cohort of patients who have undergone an all-inside suspensory method fixation. We plan to evaluate the incidence and degree of bone tunnel widening between the two groups. This will consist of two x-rays of the operative knee in both the anteroposterior and lateral view, at a 1 to 2 year follow-up. 2. Hypothesis Our hypothesis is that the all-inside technique using suspensory button fixation will result in less tunnel widening compared to a hybrid technique using interference screw and suspensory button fixation. With the all-inside technique using the anatomic anterior cruciate ligament (ACL) position there will be less potential for a "bungee-cord effect" and "windshield-wiper effect" as previously seen with more vertical transtibial tunnel techniques. Using this technique, shorter tunnels and closer fixation points will result in less graft motion to cause tunnel widening. This is in contrast to interference screw technique which we feel will enlarge tunnel size mechanically upon insertion. 3. Justification There have been many described techniques for anterior cruciate ligament (ACL) reconstruction surgery. This include graft options, tunnel positioning and fixation methods. Over the last few years, the placement of both femoral and tibial tunnels has evolved from an isometric position to a more anatomic position. The fixation methods can vary from interference screw fixation, suspensory button fixation and a trans-fix pin fixation. What we have seen in the isometric tunnel positions is the issue of tunnel widening. This has been associated with graft failure and increased knee laxity. Tunnel widening can also lead to insufficient bone stock complicating revision surgery and potentially requiring a 2-stage procedure with bone grafting. Tunnel widening has been shown with both interference screw and endobutton fixation in the past. More recently, newer instrumentation and an all-inside technique have been utilized at our institution that has some potential benefits including prevention of tunnel widening. 4. Objectives The primary outcome for this study will be radiographic assessment of tunnel width on both the femoral and tibial tunnels. X-rays will be taken in both the anteroposterior and lateral views to assess tunnel width. X-rays will be taken at 1 to 2 year follow-up following surgery. Tunnel width will be measured perpendicular to the the tunnels based on the sclerotic margins. 3 separate measurements, spaced 5 mm apart, will be taken in both the AP and lateral views. The centre of these measurements will be based at the location of the greatest width. An average of these measurements will be calculated and used to calculate bone tunnel enlargement. 5. Research Methods We plan to review the last 60 patients who have undergone anterior cruciate ligament (ACL) reconstructive surgery (30 in each study arm) performed with either technique by 3 orthopedic surgeons with subspecialty training in arthroscopic knee surgery who use similar techniques. All surgeries were performed at one center from November 2012 until present. All patients who have had anterior cruciate ligament (ACL) surgery at our institution have been entered into a data registry that includes: patient demographics and anterior cruciate ligament Quality of life outcome scores. We plan to analyze this data including surgical data on graft and tunnel sizes, fixation methods and post-operative radiographs. Post-operative radiographs will be taken at one to two year follow-up to assess tunnel width. Clinical assessment, knee ligament arthrometry (KT-1000) measurements, and outcome measure scores, anterior cruciate ligament (Quality of Life) , Lysholm and International Knee Documentation Committee (IKDC) will also be taken during each visit. Written, informed consent will be obtained from each patient prior to entering them into the study.