Summary
A Randomised Controlled Trial Comparing Single Tendon/Adjustable Button to Dual Tendon/Screw Hamstring Grafts for ACL Reconstruction
Abstract
Background
Hamstring tendon harvest for anterior cruciate ligament reconstruction (ACLR) is associated with reduced strength, donor site pain and muscle strains after surgery, whilst the impact of additional Gracilis tendon harvest is unclear. Traditional graft fixation using a tibial interference screw requires both Semitendinosus and Gracilis tendons, but newer techniques allow for a short single tendon (Semitendinosus) graft and suspensory fixation on the tibia with the theoretical benefit of minimising hamstring donor site morbidity and improved fixation. This double blinded randomised controlled trial (RCT) prospectively compared outcomes between single-tendon adjustable button (ST-AB) and dual-tendon screw (STG-S) hamstring grafts for ACLR.
Methods
131 patients were randomised and included in the RCT of which 62 received ST-AB and 69 STG-S. All patients underwent hamstring ACLR by the senior author (PD) using minimum 8mm diameter grafts. Suspensory femoral fixation (Fixed Loop Endobutton-Smith & Nephew) was used for all patients, while tibial fixation utilised an interference screw (BioRCI-Smith & Nephew) in the STG-S group and adjustable button (UltraButton-Smith& Nephew) in the ST-AB group. All other anaesthetic, surgical and rehabilitation techniques were uniform. The patient and therapist were blinded to graft choice and fixation method. PROMs were assessed pre-surgery and at 3, 6, 12 and 24 months, including the IKDC, Lysholm, ACL-RSI, Cincinnati, and VAS pain scale for frequency (VAS-F) and severity (VAS-S). Donor-Site-Related Functional Problems following ACLR (DFPACLR) scores were recorded. Graft laxity (KT-1000), isokinetic hamstring/quadriceps strength and functional hop testing were undertaken. Logistic regression evaluated associations of graft type with re-tear within 24 months controlling for age, sex, BMI and meniscal repair.
Results
All patients have reached 24 months post-surgery, with only 3 patients unavailable to undertake final follow up (2.2%). All PROMs significantly improved over time (p<0.05) with no differences between groups (p>0.05). There were no differences in KT-1000 laxity (STG-S 1.3mm, ST-AB 1.4mm). STG-S patients had larger mean diameter grafts (ST-AB 8.5mm, STG-S 8.95mm, p=0.001). A significantly lower/better (p<0.0001) DFPACLR score was seen in the ST-AB group at 6 months, maintained at 12 (p=0.003) and 24 (p=0.039) months. The ST-AB group demonstrated greater peak knee flexor strength limb symmetry (p<0.001) at 6 months, though no further differences in strength or hop outcomes were observed. Over the 24-month post-operative period there were 5 (7.2%) ACL graft re-tears in the STG-S group and only 1 (1.6%) in the ST-AB group. The ST-AB group had an 82.2% lower risk of ACL re-tear (OR 0.195, CI 0.02-1.69) though the p=0.133 likely reflects limited power to detect differences in re-tear rates.
Conclusions
This study provides the first demonstration in a prospective, RCT of improved outcomes using single tendon hamstring ACL grafts with adjustable suspensory tibial fixation. There is better early knee flexion strength symmetry and significantly reduced donor site morbidity in this group, an effect that is maintained over 2 years. There is no difference in PROMs, knee laxity and functional assessments, but the risk of graft re-tear is 82% lower in patients with single tendon/adjustable button hamstring graft ACLR.