Abstract
Aim: MRI examination of tibial tunnel enlargement after hamstring ACL surgery.
Methods and Results: 101 primary hamstring ACL reconstructions were carried out employing a transtibial over-the-top route with fixation provided by the Soffix buttonhole polyester double loop device (1186 N mean UTL to failure with young human cadaveric STG tendons). 24 were reviewed and bony tunnel enlargement was evaluated. 18 prospective reconstructions at 4 months and 6 randomly selected cases at a mean of 14 months were subjected to MRI scanning performed perpendicular to the tibial tunnel axis and the cross sectional area (CSA) was calculated with a computer programme.
In 7 cases there was no enlargement, in 5 cases there was cylindrical enlargement, in 12 cases there was conical enlargement but no cavitation was noted. A maximum mean CSA of 33% ± 38.84 sd was noted at the upper tibial tunnel exit whilst the CSA increase at the distal tibial tunnel entrance was 13% ± 16.77 sd.
In addition the MRI scan showed no evidence of excessive granulation tissue ingrowth or synovial fluid between the graft and the tunnel wall. It would appear that micro-motion which is a major factor in tunnel enlargement is eliminated by the combination of a tight fitting graft, the strength and stiffness of the fixation device and highly accurate, low stress placement of the tibial tunnel. Post operative KT 2000 arthrometric testing of the mean side to side difference (SSD) was 1.71 mm ± 1.82 sd confirming that the graft remained stiff in vivo.
Conclusion: We concluded that our technique avoids excessive tunnel enlargement and leads to greater post-operative graft stiffness than that reported in other series, where hamstring reconstruction has been employed.
The abstracts were prepared by Mr R. B. Smith. Correspondence should be addressed to him at the British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN.
