A BIOMECHANICAL AND CLINICAL STUDY OF THE SURGICRAFT MARK II STG ACL RECONSTRUCTION USING THE SOFFIX FIXATION SYSTEM VIA THE OVER THE TOP TECHNIQUE

Abstract

Background: The over the top technique was first described in 1974. The Mark II ACL reconstruction was a development on the ABC and the Mark I procedure and was introduced into clinical practice in March 1998. The soffix used is a polyester hamstring graft support device with three button holes at each end. Clinical observation showed progressive slackening of some initially successful reconstructions. Retightening restored stability. We studied the medium and long-term outcome of the procedure and tested the effects of preconditioning on its biomechanical properties.

Patients and methods: 90 patients underwent a prospective medium and long-term follow-up (3–5 years) in a dedicated research clinic. Standardised scores Lysholm, Tegner, and IKDC. were used. Biomechanical tests were performed in vitro using double equine extensor tendon-soffix model constructs. 18 experiments with an MTS Hydraulic testing machine, were carried out, preconditioning with 300, 400 and 500N. Constructs were then cyclically loaded 3000 times at 1 Hz and finally tested to failure.

Results Clinical follow-up showed good overall results. The mean Tegner score increased from 2.5 pre-operatively to 4.5. The majority had a Lysholm score of > 90(72%). The majority had an IKDC of B (75%). 10% had a side to side difference > 6mm. The mean stretch of 14mm after 3000 cycles was reduced to 4.2 mm by preconditioning with 500N. This had no adverse effect on the ultimate tensile strength.

Conclusion: The medium and long-term results of the MarK II ACL reconstruction are encouraging. Preconditioning the soffix tendon construct reduces the creep with no adverse effect on the ultimate tensile strength. A pre-conditioning device has been made to replicate this in theatre.