Summary

Single Tendon Hamstring ACL Reconstruction with Adjustable Button Fixation leads to lower MRI Graft Signal

Abstract

Introduction

Hamstring harvest for anterior cruciate ligament reconstruction (ACLr) has been associated with reduced hamstring strength; donor site pain and muscle strains after return to sport. Traditional hamstring grafts require dual semi-tendinosus/gracilis tendons (DT) to be harvested to achieve a graft of sufficient length and diameter with screw fixation on the tibia; but newer techniques allow for a shorter; broad single semi-tendinosus tendon (ST) graft using adjustable button fixation. Magnetic resonance imaging (MRI) analysis of ACLr grafts has previously been used as a proxy for healing and integration of the graft. The MRI signal characteristics of single tendon/adjustable button vs dual tendon/screw graft constructs has not previously been established.

Methods

In this double blinded prospective randomised controlled trial (RCT) (registered as a clinical trial with the Australia New Zealand Clinical Trials Registry (ACTRN12620000927921)) patients were recruited and randomised a priori into a single tendon (ST) or a dual tendon (DT) group for ACLR. All anaesthetic and surgical techniques were uniform between the groups aside from graft construct and tibial fixation (Screw (BioRCI-Smith & Nephew, Boston USA) for the DT Group; Adjustable Button (UltraButton-Smith & Nephew, Boston USA) for the ST Group. 128 patients (67 DT, 61 ST) have been included in the RCT with no loss to follow up at 1 year. A subgroup of patients underwent MRI analysis using a single 3T MRI scanner (Siemens; Dusseldorf) using a specialised uniform T1 weighted scanning protocol at 6 months and 12 months. MRI signal was measured at multiple regions of interest; with lower signal indicative of better healing and expressed as the signal intensity ratio (SIR).

Results

Overall; 46 patients (ST 20; DT 26) were assessed at 6 and 12 months post surgery. No significant group differences (P>0.05) were observed in demographics (age; sex; height and body mass) or surgical characteristics (concomitant meniscal repairs and lateral extra-articular tenodeses). In the ST/Adjustable Button group; the median SIR was 1.7 (SD 0.9) at 6 months and median 1.5 (SD 0.6) at 12 months. In the DT/Screw group; the median SIR was 2.3 (SD 1.2) at 6 months and median 2.3 (SD 0.8) at 12 months. SIR was not observed to change in either group over time. The SIR was significantly lower in the ST/Adjustable Button group vs the DT/Screw group at both 6 months (p=0.02) and 12 months (p=0.005).

Conclusion

ACL reconstruction using a Single Hamstring Tendon with Tibial Adjustable Button Fixation results in significantly lower graft signal on MRI at both 6 month and 12-month time points. This indicates radiologically improved healing and integration of this graft/fixation construct; and is the first time this has been reported in the literature. Clinical correlation assessing laxity and re-injury rates will be reported in a future analysis of this DOSTAR RCT sub-group.