Summary

Bioabsorbable Poly L (L-lactic acid) screws for ACL reconstruction demonstrated excellent structural and functional outcomes at mean 13-year follow-up, and should be considered as an alternative to metal screws especially in high volume surgeons who undertake revision ACL reconstruction.

Abstract

Introduction

Bioabsorbable screws for ACL reconstruction have been a concern for surgeons. Recent systematic reviews suggest complications of higher graft failure, resultant instability, tunnel widening, screw breakage, and inflammatory/foreign body reaction. The purpose of this study was to determine the accuracy of recent systematic reviews to report our complications, failure rate, tunnel widening, stability, and patient-reported outcomes at mean 13-year follow-up in patients after ACL reconstruction using bioabsorbable Poly (L-Lactic Acid) interference screw fixation.

Methods

All patients who underwent transtibial, single-bundle, bone-patellar tendon-bone (BTB) autograft/allograft ACL reconstruction using a bioabsorbable Poly (L-Lactic Acid) interference screw (ConMed Linvatec, Largo, FL) for the femoral and tibial sockets with a minimum 5-year follow-up were included in the study. Patients who underwent revision ACL reconstructions, multi-ligament reconstructions, and concomitant cartilage repair procedures were excluded. Physical examination included knee range of motion, and stability testing (KT-1000, Lachman, pivot-shift tests). Imaging included a routine knee series and 3-foot standing radiographs, MRI, and CT scan. Patient-reported outcome measures included IKDC, Lysholm, KOOS, Tegner, and VR-12 PCS and MCS questionnaires. Failure was defined as revision ACL reconstruction, tunnel widening on CT scan, or pathologic instability noted on KT-1000.

Results

Eighty patients (46 males, 34 females; mean age 36 years) met the inclusion criteria. Thirty knees underwent BTB autograft reconstruction and 51 knees underwent allograft reconstruction with an average follow-up of 13±4 years (range 5 to 23 years). There were no postoperative infections in any patient as defined by CDC criteria. Tibial and femoral tunnels were created with a 10mm reamer. There were no signs of tunnel widening on CT scan. At 2 years, tunnel narrowing was observed on CT scan. At 13.4 years, the mean size of the femoral tunnel was 8.6±2mm and the mean size of the tibial tunnel was 8.5±2mm which also showed tunnel narrowing. Instability testing with KT-1000 demonstrated a mean manual maximum difference (MMD) compared to the contralateral limb of -0.2mm (range -3.5 to 9mm). Seventy-three knees (92%) had a =3mm MMD difference on KT-1000. One patient (1.25%) required revision ACL reconstruction due to a traumatic event at 6 months. Outcome measures revealed a mean VR-12 PCS=57±8, VR-12 MCS=52±5; Lysholm=89±12; IKDC=76±15; KOOS Symptom=82±17; KOOS Pain=90±15; KOOS ADL=94±10; KOOS Sport=81±22; KOOS QoL=81±16 at average 13-year follow-up with a median postoperative Tegner of 5 (range 2 to 9).

Conclusion

Transtibial, single bundle, BTB ACL reconstruction using a bioabsorbable Poly L (L-lactic acid) screw did not result in delayed graft healing, nor was there any evidence of screw breakage or tunnel widening. Patients exhibited excellent knee stability and functional outcomes at mean 13-year follow-up.