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.

Aim: The purpose of the study was to assess the outcome results of an artificial bioprosthetic ligament used at Mayday University Hospital for ACL reconstruction in a cohort of patients after 1992 following the introduction of special instrumentation and to compare it with the results in an earlier cohort of patients. A high incidence of implant failure including rupture and stretching was noted in the early cohort with a 44% failure rate noted at three years following implantation. A mode of failure analysis led to the development of a modification of the implant, and introduction of new surgical instrumentation resulting in an improved implantation technique.

Method: The Fresh cohort of patients was reviewed after the introduction of the new surgical instrumentation in 1992. 80 out of 111 operated patients were available for follow-up. There was 21.6 % failure rate and the following objective and subjective parameters were used: side to side difference measurements using the KT2000 arthrometer, average Lysholm score, average Tegner score and average Mohtadi score. The mean SSD was 3.14mm, the average Lysholm score was 74.93, the average Tegner score was 4.72 and the average Mohtadi score was 45.32.

Conclusion: We were able to review 71% of patients operated on since 1992 using the above outcome measures. We concluded that the introduction of new surgical instrumentations and alterations in surgical technique since 1992 has improved the outcome following this type of surgery, although these results do not match the best reported for autologous ACL reconstruction.