Tibial tunnel widening in patients undergoing primary anterior cruciate ligament reconstruction: hydroxyapatite-coated vs. uncoated interference screws

Abstract

Introduction

Tunnel widening following anterior cruciate ligament (ACL) reconstruction remains a significant clinical concern. Polyether ether ketone (PEEK) screws offer favorable biomechanical properties and MRI compatibility; however, they lack osteoconductivity, which may contribute to tunnel widening. This study investigated whether hydroxyapatite (HA)-coated polyether ether ketone (PEEK) screws reduce tibial tunnel widening compared to uncoated PEEK screws, considering the osteoconductive properties of HA. We hypothesized that HA-coated PEEK screws would demonstrate significantly less tibial tunnel widening at one year postoperatively than uncoated PEEK screws.

Materials and methods

A retrospective cohort study was conducted on patients who underwent primary ACL reconstruction using hamstring autografts. The patients were divided into two groups: Group 1 received HA-coated PEEK interference screws, and Group 2 received uncoated PEEK screws. Tibial tunnel diameters were measured on standardized anteroposterior and lateral radiographs immediately postoperatively (baseline) and at the first-year follow-up. Tunnel width was assessed perpendicular to the tunnel axis at consistent locations, and the percentage tunnel widening was calculated from the baseline. Two independent observers measured the tunnel dimensions separately.

Results

A total of 65 patients were analyzed, of whom 31 received HA-coated PEEK screws and 34 received standard uncoated PEEK screws. At the first-year follow-up, tunnel widening was significantly lower in the HA-coated group across all measurement sites. In the AP view, the proximal, middle, and distal regions showed significantly reduced tunnel widening in the HA-coated group (p < 0.05). A similar outcome was observed in all three regions of the lateral view, with significantly less widening with HA-coated screws than with uncoated screws (p < 0.05).

Conclusion

Compared with standard uncoated PEEK screws, HA-coated PEEK screws significantly reduced tibial tunnel widening at the one-year follow-up after primary ACL reconstruction. The added osteoconductive properties of HA may be the underlying mechanism. These findings suggest that HA-coated screws may offer improved biological fixation and better long-term graft stability compared to uncoated screws.

Level of evidence

Level III, retrospective cohort study.