Summary

The rate of initial fixation failure was not different between the usage of metallic and bioabsorbable interference screws for femoral fixation in anatomic rectangular tunnel with a bone-patellar tendon-bone graft.

Abstract

Introduction

Interference screw fixation has been widely used in anterior cruciate ligament reconstruction surgery. The disadvantages of using metallic interference screws include distorted magnetic resonance images and difficulty in revision surgery. To overcome these, the use of bioabsorbable interference screws has been reported. However, certain problems, such as screw breakage and initial fixation failure, have been encountered. In anatomical rectangular tunnel anterior cruciate ligament reconstruction with bone-patella tendon-bone graft (ART-BTB), a snug fitting of the graft is achieved at a 5 × 10 mm rectangular femoral tunnel interface. We considered that a metallic interference screw might not be necessary for this and began using bioabsorbable interference screws for femoral fixation. In addition, we have invented and performed a “tensioning trial” to evaluate initial fixation strength during surgery. This study aimed to investigate screw breakage and initial femoral fixation failure during ART-BTB using bioabsorbable interference screws.

Materials And Methods

Data were collected prospectively from 142 patients undergoing ART-BTB and computed tomography (CT) scan until 3 weeks after surgery. Metallic (metallic group, n = 34) or bioabsorbable (bioabsorbable group, n = 108) interference screws were used for femoral fixation. The latter group was further divided into subgroups: cases wherein dilation was not performed before inserting bioabsorbable interference screw (non-dilating group, n = 15) and those wherein dilation was performed (dilating group, n = 93). These were historically controlled.
The ART-BTB procedures were performed almost exactly according to the procedure described by Shino. We routinely used the outside-in method to make a tunnel and insert the interference screw. After insertion, a “tensioning trial,” which we invented, was performed by passing fiberwire through the distal side of the tendon of the graft and pulling with maximum manual force while simultaneously viewing the femoral tunnel aperture arthroscopically. Cases wherein a bone plug appeared even slightly unstable were considered as having initial fixation failure. Double Spike Plate fixation (Meira, Aichi, Japan) was added for these cases to achieve stable fixation. The MILAGRO (Depuy Mitek, Raynham, MA, USA) or BIOSURE HA (Smith & Nephew, Andover, MA, USA) bioabsorbable interference screws were used in this study.
The following parameters were intraoperatively assessed: interference screw breakage, initial fixation failure by tensioning trial, and posterior wall breakage before fixation. Posterior wall breakage was also assessed by CT scan.
The non-dilating and dilating groups were compared using Fisher’s exact probability test, chi-square test, or t-test. The metallic and bioabsorbable groups were also compared. Multivariate analysis using logistic regression analysis was performed to investigate the factors predictive of initial fixation failure or screw breakage. All analyses were performed using SPSS 21.0. P values of <0.05 were considered statistically significant. [Result] Screw breakage was significantly higher in the non-dilating group than in the dilating group (20.0% vs 2.2%, p = 0.01); the other factors did not significantly differ between groups. Logistic regression analysis revealed that the dilating procedure only predicted screw breakage (p = 0.01). The rate of initial fixation failure and the other factors were not significantly different between the metallic and bioabsorbable groups. Logistic regression analysis revealed that posterior wall breakage only predicted initial fixation failure (p = 0.01).

Discussion

The rate of bioabsorbable interference screw breakage decreased from 20.0% to 2.2% due to dilation before insertion. The rate of initial fixation failure, evaluated by tensioning trial, was not different between the usage of metallic and bioabsorbable interference screws. Thus, we suggest that the use of bioabsorbable screws may be safe during ART-BTB surgery.