Summary

The 5HS autograft technique is a valid option when faced with a graft of insufficient diameter and when subjected to interference screw fixation.

Abstract

Introduction

The purpose of this study was to systematically review the literature to examine the biomechanical and clinical outcomes of five-strand hamstring (5HS) autografts for anterior cruciate ligament reconstruction (ACLR).

Methods

A systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was performed by searching PubMed, Embase, and the Cochrane Library for studies reporting the biomechanical results of 5HS autografts and clinical outcomes of patients undergoing ACLR using 5HS autografts. All English-language literature published from 2012-2018 which reported biomechanical strength and properties of 5HS autografts and clinical outcomes following ACLR 5HS autografts with a minimum one-year follow-up was reviewed by 2 independent reviewers. Data on graft diameter, stiffness, displacement, strength, failure rate and patient-reported outcomes (PROs), including postoperative Lysholm scores were collected. Study methodological quality was evaluated with the Modified Coleman Methodology Score (MCMS).

Results

Five studies, including two biomechanical studies and three clinical outcome studies (1 Level II, and 2 Level III), were included. The two biomechanical studies compared graft diameter, strength, stiffness and displacement of four-strand hamstring (4HS) grafts to 5HS grafts via in vitro models. One study compared outcomes of 16 cadaveric lower extremities assigned to either a 4HS or 5HS group. The mean diameters for the 4HS and 5HS grafts were 6.8mm and 8.2mm, respectively. All grafts were subjected to Krackow Interlocking Sutures for tests. There were no significant differences in stiffness or displacement between groups (p=0.82, p=0.29, respectively). In the second biomechanical study, ovine flexor tendon split grafts were used to create 4HS and 5HS constructs, which were both subjected to suspensory fixation. The mean diameter and length for the 4HS graft was 5.2mm and 172.2mm, respectively. Whereas, the mean diameter and length for the 5HS ovine grafts was 5.3mm and 215mm, respectively. Ultimate load, stiffness and stress-relaxation were measured using a uniaxial electromechanical load system, and there were no observed significant differences across all measurements (p=0.46, p=0.30, p=0.80, p=0.59, respectively). Additionally, three clinical outcome studies including a total of 115 patients who underwent primary ACLR using hamstring autografts were included. Of the clinical studies, one study reported outcomes of 25 patients (median age, 24 years; average follow-up, 17.8 months) who underwent ACLR using a 5HS autograft. The remaining two clinical studies compared outcomes of 62 patients (average age, 28.6 years; average follow-up, 25.3 months) who underwent ACLR using a 4HS autograft to 53 patients (average age, 29.5 years; average follow-up, 26.4 months) who underwent the same procedure using a 5HS autograft. The overall mean diameter for 4HS and 5HS grafts were 8.4mm and 9.1mm, respectively, and all three studies exclusively used interference screw fixation. The overall postoperative mean Lysholm score was 93.4 (4HS, 91.5; 5HS, 94.6).

Conclusion

The 5HS autograft technique is a valid option when faced with a graft of insufficient diameter and when subjected to interference screw fixation. However, 4HS autografts with a diameter greater than 8mm appear to achieve comparable results. Further study is necessary for determining the in vivo effects of different fixation techniques.