Hybrid femoral fixation of soft-tissue grafts in anterior cruciate ligament reconstruction using the EndoButton CL and bioabsorbable interference screws: a biomechanical study.

PURPOSE: The purpose of this study was to evaluate the effect of hybrid femoral fixation with bioabsorbable interference screws (BioRCI; Smith & Nephew Endoscopy, Andover, MA) and EndoButton CL (Smith & Nephew Endoscopy) fixation. METHODS: Biomechanical testing of 3 different fixation techniques was performed by use of porcine hind-limb distal femurs and mature bovine extremity common extensor tendons. Two independent testing sessions were examined. The first testing session (group A) compared femoral fixation via the EndoButton CL device (n = 6) with femoral fixation via the EndoButton CL device with the addition of a BioRCI screw (n = 6). The second testing session (group B) compared femoral fixation via BioRCI screws alone (n = 6) with femoral fixation via the EndoButton CL device with the addition of a BioRCI screw (n = 6). The femur-graft complex was cyclically loaded between 50 and 250 N at 1 Hz for 1,000 cycles. After cycling, the amount of graft slippage was determined by measuring the change in grip-to-grip distance. The complex was then loaded to failure at 1 mm/s, and the ultimate tensile strength, stiffness, and mode of failure were determined. RESULTS: In group A the addition of an interference screw to the EndoButton CL fixation increased the ultimate tensile strength (1,364.7 +/- 102.4 N for EndoButton CL alone v 1,449.3 +/- 94.4 N for combined technique, P = .035) and stiffness (195.5 +/- 12.1 N/mm for EndoButton CL alone v 307.3 +/- 54.9 N/mm for combined technique, P = .004) and decreased the amount of graft slippage (2.6 +/- 0.5 mm for EndoButton CL alone v 2.0 +/- 0.3 mm for combined technique, P = .017). In group B the addition of the EndoButton CL device to interference screw fixation significantly increased the ultimate tensile strength (643.5 +/- 148.4 N for BioRCI screws alone v 1,290.3 +/- 254.4 N for combined technique, P = .004) but had no effect on stiffness (315.7 +/- 38.9 N/mm for BioRCI screws alone v 341.5 +/- 64.0 N/mm for combined technique, P = .267) or graft slippage (2.7 +/- 1.0 mm for BioRCI screws alone v 2.0 +/- 0.6 mm for combined technique, P = .087). CONCLUSIONS: Our study shows that hybrid femoral fixation of double-looped gracilis-semitendinosus grafts via the EndoButton CL device and a bioabsorbable interference screw is stronger than interference or EndoButton CL fixation alone with respect to ultimate tensile strength, stiffness, and slippage. The addition of an interference screw to suspensory fixation via the EndoButton CL device increased the ultimate tensile strength from 1,360 N to 1,450 N, improved reconstruction stiffness from 200 N/mm to 300 N/mm, and decreased the amount of graft slippage resulting from cyclic loading from 2.6 mm to 2.0 mm. CLINICAL RELEVANCE: The hybrid fixation of the EndoButton CL device and an interference screw is a stronger and stiffer construct than either device alone and allows for aperture fixation, which may translate into better clinical results.

The effect of interference screw diameter on soft tissue graft fixation.

Tibial fixation of soft-tissue grafts is a weak link in anterior cruciate ligament reconstruction. Previous studies have examined varying interference screw lengths, screw types and tunnel sizes as means to improve graft fixation. We hypothesized that increasing interference screw diameter would significantly increase the maximum load to failure of the graft and decrease the graft's initial slippage. Seventy tibialis anterior and tibialis posterior tendons were divided, looped, trimmed, and sutured to simulate 4-strand hamstring grafts. These grafts were then inserted into composite bone blocks having pre-drilled 8 mm holes and fixed with 8 mm, 9 mm, 10 mm, 11 mm, or 12 mm interference screws. Fourteen grafts were tested for each screw size. The graft was first cyclically loaded from 50 N to 250 N at 0.3 Hz for 100 cycles to measure graft slippage. The graft was then tested to failure at 0.5 mm/sec to determine the maximum load to failure and mode of failure. Graft slippage was not affected by screw diameter. Maximum load to failure increased with increasing screw diameter up to 11 mm; 11 mm screw fixation was 20% stronger than 8 mm screw fixation. In this model, no increase in graft fixation was seen in by increasing interference screw diameter beyond 3 mm of the tunnel diameter.

The interaction between the whipstitch sutures of multi-strand ACL grafts and interference screw fixation.

In a recent experiment examining the effect of interference screw sizing on the fixation stability of multi-strand anterior cruciate ligament grafts, we noticed a large variation in fixation strengths and attributed it to the suturing of the grafts and its interaction with the screw. We performed an experiment using interference screws for fixation of hamstring grafts within a bone tunnel model to compare how the presence of sutures affected graft fixation. We found that having sutures along the region of the graft that contacts the screw within the bone tunnel can increase graft fixation strength 100%.

All-arthroscopic removal of a suture anchor using an arthroscopic bur sheath.

Suture anchors are commonly used in shoulder repairs, especially arthroscopically performed repairs. Anchors can become prominent and require removal. We describe a technique of arthroscopic anchor removal using a bur sheath.

Shoulder pain and the overhand athlete.

There has been much controversy surrounding the issue of shoulder pain and the overhand athlete. Several hypotheses have been suggested as to the cause of the shoulder pain--subacromial impingement, anterior capsular laxity, internal or posterosuperior impingement, traction injury, and scapular imbalance. Treatment for the patient depends on the specific cause of the pain. As always, a full routine of nonoperative therapeutic measures should be administered before resorting to surgical intervention.