A BIOMECHANICAL COMPARISON OF MATCHED FOUR-STRAND AND FIVE-STRAND SEMITENDINOSUS-GRACILIS GRAFTS

ABSTRACT Introduction: Recent studies have shown that the likelihood of semitendinosus-gracilis graft rupture is inversely correlated to its diameter. A graft can be prepared in a five-strand or four-strand fashion to increase its diameter. However, the biomechanical superiority of five-strand semitendinosus-gracilis grafts is still under debate. Objective: This study aimed to evaluate the biomechanical characteristics of matched four-strand and five-strand human semitendinosus-gracilis grafts. Methods: We evaluated semitendinosus-gracilis tendons harvested from ten fresh human male and female cadavers, aged 18-60 years. Four-strand or five-strand grafts were prepared with the tendons and fixed to wooden tunnels with interference screws. Each graft was submitted to axial traction at 20 mm/min until rupture; the tests were donor matched. Data were recorded in real time and included the analysis of the area, diameter, force, maximum deformation and stiffness of the grafts. Results: The diameter, area and tunnel size were significantly greater in the five-strand grafts than in the four-strand grafts. There were no significant differences in biomechanical properties. The area and diameter of the graft were positively correlated to stiffness, and inversely correlated to elasticity. There was no significant correlation between graft size and maximum force at failure, maximum deformation or maximum tension. Conclusion: Five-strand hamstring grafts have greater area, diameter and tunnel size than four-strand grafts. There were no significant differences in biomechanical properties. In this model using interference screw fixation, the increases in area and diameter were correlated with an increase in stiffness and a decrease in elasticity. Level of evidence V; biomechanical study.

Strength of interference screw fixation of meniscus prosthesis matches native meniscus attachments

Purpose Meniscal surgery is one of the most common orthopaedic surgical interventions. Total meniscus replacements have been proposed as a solution for patients with irreparable meniscal injuries. Reliable fixation is crucial for the success and functionality of such implants. The aim of this study was to characterise an interference screw fixation system developed for a novel fibre-matrix-reinforced synthetic total meniscus replacement in an ovine cadaveric model. Methods Textile straps were tested in tension to failure (n = 15) and in cyclic tension (70–220 N) for 1000 cycles (n = 5). The textile strap-interference screw fixation system was tested in 4.5 mm-diameter single anterior and double posterior tunnels in North of England Mule ovine tibias aged > 2 years using titanium alloy (Ti6Al4Va) and polyether-ether-ketone (PEEK) screws (n ≥ 5). Straps were preconditioned, dynamically loaded for 1000 cycles in tension (70–220 N), the fixation slippage under cyclic loading was measured, and then pulled to failure. Results Strap stiffness was at least 12 times that recorded for human meniscal roots. Strap creep strain at the maximum load (220 N) was 0.005 following 1000 cycles. For all tunnels, pull-out failure resulted from textile strap slippage or bone fracture rather than strap rupture, which demonstrated that the textile strap was comparatively stronger than the interference screw fixation system. Pull-out load (anterior 544 ± 119 N; posterior 889 ± 157 N) was comparable to human meniscal root strength. Fixation slippage was within the acceptable range for anterior cruciate ligament graft reconstruction (anterior 1.9 ± 0.7 mm; posterior 1.9 ± 0.5 mm). Conclusion These findings show that the textile attachment-interference screw fixation system provides reliable fixation for a novel ovine meniscus implant, supporting progression to in vivo testing. This research provides a baseline for future development of novel human meniscus replacements, in relation to attachment design and fixation methods. The data suggest that surgical techniques familiar from ligament reconstruction may be used for the fixation of clinical meniscal prostheses.

Biomechanical Comparison of FiberTape Device Repair Techniques of Ligamentous Lisfranc Injury in Cadaveric Model

Category: Trauma; Basic Sciences/Biologics; Midfoot/Forefoot; Sports Introduction/Purpose: Lisfranc ligamentous injuries are complex. Controversy exists regarding their treatment and preferred method of fixation. Fixation methods employing a FiberTape device and interference screw fixation have been described as an alternative to traditional screw fixation. The purpose of this biomechanical study was to evaluate two methods of fixation utilizing interference screw fixation with FiberTape augmentation in a cadaveric model. Methods: 9 paired cadaveric feet (mid tibia/fibula) were separated into two groups based on fixation method: FiberTape alone and FiberTape with supplementary limb into the middle cuneiform via anchor. At three joints of the midfoot (second metatarsal - medial cuneiform, intermediate cuneiform - medial cuneiform, second metatarsal - intermediate cuneiform), the diastasis and relative angular displacement between bones in the coronal plane were measured for static and cyclic loading. Measurements were obtained for the native (pre-injured), injured, and post-fixation in static loading. Fixed specimens then underwent stepwise increases in cyclic loading performed at 1 Hz and 100 cycles, at 100 N intervals from 500 to 1800 N ground reaction force. The Achilles tendon was also loaded to simulate postoperative weightbearing. Failure of fixation was defined as diastasis at the second metatarsal - medial cuneiform joint greater than 2 millimeters. Results: FiberTape specimens demonstrated diastasis failures of 3 of 9 (33%) specimens at cyclic loads of 1000 N. Conversely, FiberTape with supplementary limb specimens all survived past this loading magnitude, with 1 failing at supraphysiologic loads (>1200 N). The difference in diastasis at the second metatarsal-medial cuneiform joint was statistically significant between the two groups at forces of 1600N (p = 0.019) and 1800N (p = 0.029). There were no significant differences between the other joint diastases and relative angular displacements. Conclusion: The use of FiberTape for fixation of ligamentous Lisfranc injuries appears to provide a biomechanically viable alternative for withstanding early post-operative protected weightbearing. Furthermore, the use of a supplementary limb in addition to the FiberTape fixation method appears to enhance its biomechanical efficacy under cyclic loading especially at higher loads.

Is all-inside with suspensory cortical button fixation a superior technique for anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis

Background To compare the clinical results of all-inside anterior cruciate ligament reconstruction (ACLR) using suspensory cortical button fixation and full tibial tunnel drilling Methods Systematic searches were conducted of published literature up to November 2019 on PubMed, Embase, and Cochrane for studies comparing all-inside ACLR using suspensory cortical button fixation and full tibial tunnel ACLR. Two reviewers independently determined eligibility, extracted the outcome data, and assessed the risk of bias of the eligible studies. The clinical outcome and graft reruptures were pooled by using random effects with mean differences and risk ratios for continuous and dichotomous variables, respectively. Result A total of nine studies (five randomized controlled trials and four comparative studies) involving 613 patients were included in the meta-analysis. The postoperative functional outcome, knee laxity measured with arthrometer, and graft reruptures were comparable between patients with all-inside ACLR using suspensory cortical button fixation and full tibial tunnel ACLR. However, a significantly greater thickness of autologous tendon was used and less change in drilling tunnel diameter was noted in patients with suspensory cortical button graft fixation.Conclusions All-inside ACLR with suspensory cortical button fixation was not clinically superior to full tibial tunnel ACLR with interference screw fixation in functional outcomes, knee laxity measured with arthrometer, or rerupture rate. However, the advantage of using suspensory cortical button fixation was that a thicker graft could be used for reconstruction, and brought less tibia tunnel widening compared with bioabsorbable interference screw fixation.