Aims: The aims of this study were to evaluate the biomechanical properties and mode of failure of a technique of anterior cruciate ligament (ACL) reconstruction using the Soffix polyester fixation device. A 2-strand equine extensor tendon graft model was used because a previous study has shown it to have equivalent bio-mechanical properties to that of 4-strand human semitendinosus and gracilis tendon grafts.

Method: Ten stifle joints were obtained from 5 skeletally mature pigs, the soft tissues were removed and the ACL and PCL were sacrificed. Tibial tunnel preparation was standardised using the Mayday rhino horn jig to accurately position a guide wire over which an 8mm tunnel was drilled. A 2-strand equine tendon-Soffix graft was used to reconstruct the ACL of the porcine knee using over the top femoral placement with bicortical screw fixation. Mechanical testing of 10 specimens was performed.

Results: The mode of failure included 4 midsubstance tendon failures, 3 Soffix failures and 3 failures at the suture-Soffix interface. The mean ultimate tensile load for the ACL reconstruction was 1360 N (standard deviation (SD) =354), elongation to failure of 41 mm (SD=7.5) and a structural stiffness of 35 N/mm (SD=8.1).

Conclusion: This in vitro study has shown that the technique of ACL reconstruction using the Soffix soft tissue fixation device with a tendon graft placed in the over the top position is biomechanically strong, providing a sufficiently high UTL immediately following reconstruction, therefore allowing early weight bearing and rehabilitation.

Aims: The aims of this study were to evaluate the biomechanical properties and mode of failure of four methods of fixation of hamstring anterior cruciate ligament (ACL) grafts. The fixation methods investigated included titanium round headed cannulated interference (RCI) screws, bioabsorbable RCI screws, Endobuttons and Bollard fixation. A 2-strand equine extensor tendon graft model was used because a previous study has shown it to have equivalent biomechanical properties to that of 4-strand human semitendinosus and gracilis tendon grafts.

Method: Thirty-two stifle joints were obtained from skeletally mature pigs, the soft tissues were removed and the ACL and PCL were sacrificed. Tibial tunnel preparation was standardised using the Mayday rhino horn jig to accurately position a guide wire over which an 8mm tunnel was drilled. A 2-strand equine tendon graft was then introduced into the tibial tunnel and secured with either a titanium RCI screw, a bioabsorbable RCI screw, an Endobutton or an expansile Bollard. The proximal part of the graft was attached to the crosshead of a materials testing machine using the Soffix. Five of each method of fixation were tested mechanically to ultimate failure and under cyclical loading.

Results: The mean ultimate tensile loads (UTL) were: titanium RCI screw = 444 N, bioabsorbable RCI screw = 668 N, Endobutton = 999 N and Bollard = 1153 N. The mode of failure for all RCI screws involved progressive tendon slippage past the screw. Under cyclic loading conditions the titanium and bioabsorbable RCI screws rapidly failed after several hundred 5 to 150 N cycles due to tendon damage and slippage. Both the Bollards and Endobuttons survived 1500 cycles at 50–450N, with less tendon slippage.

Conclusion: Titanium and bioabsorbale RCI screws provide poor initial fixation of tendon grafts used for ACL reconstruction and fail rapidly under cyclic loading. Both Bollards and Endobuttons provide sufficiently high UTL’s and survive cyclic loading to allow early postoperative mobilisation and rehabilitation. Caution must be used in the early postoperative period when using interference screws to secure a hamstring tendon graft because early progressive tendon slippage may result in excessive graft elongation and early clinical failure.

Aims: We present the short term results of a method of reconstruction of the anterior cruciate ligament (ACL) using the Soffix, polyester soft tissue fixation device.

Method: Over a 4-year period, 111 patients underwent reconstruction of the ACL using a 4-strand hamstring graft in combination with a Soffix fixation device. The hamstring tendons were harvested and woven around the Soffix. The tendons are then sutured to the Soffix using polyester baseball type sutures to create a 4-strand graft. Prior to implantation in the knee joint the central part of the Soffix is resected leaving a free tendon window, which eventually becomes intra-articular. Tibial tunnel placement was standardised using the Mayday rhino horn jig. An over the top femoral placement was used together with polysulphon bollard fixation. These patients underwent prospective evaluation in a dedicated research clinic, which included clinical assessment, KT-2000 arthrometric assessment, Lysholm, Tegner and IKDC scoring.

Results: A total of 93 from 111 patients (84%) were available for follow up. The mean follow up time was 22 months (range 12–48). There were 79 males and 14 females with a mean age at operation of 30 years (range 16–48). The pivot shift was abolished in 85% of patients and the mean side to side difference (SSD) was 2.2mm ±1.8. The mean post operative Lysholm score was 93.4 ±8.6, the mean drop in Tegner score was 1.3. 84 patients (90%) scored normal or nearly normal (A or B) using the IKDC system, with no patients scoring D.

Conclusions: We conclude that reconstruction of the ACL using a Soffix-4 strand hamstring graft with an over the top femoral route has good short term subjective and objective outcome measures with a low mean SSD. We recommend this technique in the vast majority of ACL deficient patients.

Aim: The aim of our study was to evaluate the results of the Soffix Mark 1 and Mark 11 hamstring fixation device, placed transtibially with an “over the top” femoral route when applied to revision anterior cruciate ligament (ACL) surgery.

Method and results: Twenty nine ACL revisions performed between 1992 – 2000 were evaluated. Twenty six failed prosthetic ligaments, two failed semitendinosus/ gracilis (STG) and one BTB autografts were revised using hamstring grafts in 26, quadriceps in two, and patella bone tendon bone (BTB) in one patient. Mark 1 and 11 fixation devices were employed. Follow up included clinical examination, KT 2000 arthrometric assessment, Lysholm, Tegner and IKDC scoring. The average follow up time was 50 months ±22.4.

Arthrometric examination showed a mean side to side difference (SSD) of 1.66 mm ±1.5. The mean Lysholm score was 87.2 ±12.5 and 22 patients had a B rating (nearly normal) on IKDC scoring.

The Mark II Soffix group had a mean SSD of 1.23 mm ±1.3, a mean Lysholm score of 85.8 ±14.6 and IKDC B rating in 11/15. The lowest clinical scores were in 4 multiply operated knees but the SSDs were comparable with other groups. The Mark 1 Soffix group had a mean SSD of 2.0 mm ±1.6, Lysholm score of 84.6 ±14.3 and 13/16 had a B rating (IKDC). The smaller SSD in the Mark I Soffix was statistically significant (p< 0.05) when compared with the Mark I device. Multiply operated knees had worse IKDC and Lysholm scores (not statistically significant).

Conclusions: We concluded that a revision technique using the STG Soffix fixation device can restore stability with good functional outcomes following failed primary ACL reconstruction. Multiply re-operated knees had the worst functional results despite restoration of stability.

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.