We compared the initial strength of two techniques for repair of rotator cuff tears. Eight paired cadaveric shoulders with a standardized supraspinatus defect were studied. A transosseous suture and anchor repair was conducted on each side. Specimens were tested under cyclic loading, while fixation was monitored with an optical tracking technique. Mode of failure, number of cycles and load to failure were measured for 50% (5 mm) and 100% (10 mm) loss of repair. Anchors provide improved repair strength at 50% repair loss, in comparison to sutures (p< 0.05). Strength was unaffected by bone mineral density, age and gender.

The purpose of this study was to compare the initial strength of two rotator cuff repair techniques.

Repair strength with anchors was superior to sutures. Strength was unaffected by bone quality.

Anchors, enabling a quicker, less invasive arthroscopic repair, offer improved fixation over sutures, which are more time consuming and invasive.

Eight paired shoulders with a standardized supra-spinatus defect were randomized to anchor or suture repair, and subjected to cyclic loading. Repair migration was measured using a digital camera. Failure mode, cycles and load were measured for 50% and 100% loss of repair. Results were correlated with bone mineral density, age and gender.

The anchors failed at the anchor-tendon interface, whereas the sutures failed through the sutures. Mean values for 50% loss of repair were 205.6 ± 87.5 cycles and 43.8 ± 14.8 N for the sutures, and 1192.5 ± 251.7 cycles and 156.3 ± 19.9 N for the anchors (p< 0.05). The corresponding values for 100% loss of repair were 2457.5 ± 378.6 cycles and 293.8 ± 27.4 N for the sutures, and 2291.9 ± 332.9 cycles and 262.5 ± 28.0 N for the anchors (p> 0.05). These results did not correlate with bone quality.

This study has demonstrated that anchors provide improved repair strength, in comparison to sutures. This may be due to the relative less deformability of the anchors. Repair strength did not correlate with bone quality. This may be attributed to each repair failing primarily through the repair construct or at the anchor-tendon interface, and not through bone.

A load cell, capable of measuring medial and lateral loads independently, was used to evaluate current methods of ligamentous balancing in total knee arthroplasty. Ten cadaveric knees were randomized with the surgeons blinded or unblinded to the load cell’s output. Before ligament resection, there were differences between medial and lateral forces (p< 0.05). Balance improved in both groups following ligamentous releases. There was a trend for superior balance (medial-lateral compressive force) with load cell feedback provided: 30°(11.1 vs. 44.4N), 60°(7.1 vs. 36.9N), and 90°(3.0 vs. 8.7N). Further in-vivo studies with this device may improve load transfer and the longevity of TKA.

The purpose of this study was to employ a tibial load cell to assess current methods of ligamentous balance during total knee arthroplasty, and to determine whether the load cell can improve load distribution between the medial and lateral compartments.

Current methods achieve imperfect load balance, however this may be improved with the assistance of an intra-operative load cell.

Intra-operative assessment and quantification of load balance with a load cell may improve the longevity of TKA.

TKA was performed on five pairs of cadaveric knees which were randomly assigned into one of two groups based upon whether the surgeons were blinded or unblinded to the load cell’s output. A validated tibial load cell, capable of measuring medial and lateral loads independently, was inserted. Compartment forces were recorded at discrete flexion angles prior to ligamentous balancing and again after soft tissue balancing with final components cemented into position.

Initially, there were significant differences between the loads in the medial and lateral compartments (p< 0.05). With soft tissue release, there was improved balance. There was a trend for superior balance (medial minus lateral compressive force) in the unblinded group at 30°: 11.1N unblinded vs. 44.4N blinded, 60°: 7.1 vs. 36.9N, and 90°: 3.0 vs. 8.7N.

Failure to achieve ligamentous balance results in instability and unequal load distribution. Current balancing techniques are not perfect, but appear to be improved with the use of the load cell. Further in-vitro and in-vivo studies are needed to improve the load distribution following TKA.

Introduction and Aims: Suture anchors allow consistent reattachment of tendons and ligaments to bone. Many options are available. The purpose of this study was to compare the initial strength of two rotator cuff repair techniques. The hypothesis was that rotator cuff repair strength with anchors would be inferior to transosseous sutures.

Method: Eight paired shoulders with a standardised supraspinatus defect were randomised to bioabsorbable nonsuture-based anchor or transosseous suture repair. Each specimen was then subjected to a stepwise cyclic loading protocol, utilising a custom-designed loading apparatus. Repair site migration was measured using an optical measurement system, consisting of a digital camera and custom software. Mode of failure, number of cycles and load to failure were measured for 50% (5 mm) and 100% (10 mm) loss of repair. These results were correlated with bone mineral density, age and gender. Statistical analysis utilised paired t-tests and Pearson correlations.

Results: The anchors failed at the anchor-tendon interface, whereas the sutures failed through the sutures. Mean values for 50 percent loss of repair were 206 ± 88 cycles and 44 ± 15 N for the sutures, and 1193 ± 252 cycles and 156 ± 20 N for the anchors (p< 0.05). The corresponding values for 100 percent loss of repair were 2458 ± 379 cycles and 294 ± 27 N for the sutures, and 2292 ± 333 cycles and 263 ± 28 N for the anchors (p> 0.05). These results may be due to the relative less deformability of the anchors. This may be relevant clinically, as in the early post-operative period, while tendon healing to bone is occurring, anchors may offer improved strength, allowing improved initial healing. Strength was unaffected by bone quality. This may be attributed to each repair failing primarily through the repair construct or at the anchor-tendon interface, and not through bone. Strengths of this study include the use of paired specimens, the stepwise cyclic loading protocol, as well as increased accuracy of our measurement system. Limitations include the use of an in vitro model, as well as a simulated, standardised rotator cuff tear.

Conclusion: Repair strength with anchors was superior to sutures. Strength was unaffected by bone quality. Anchors facilitate an arthroscopic procedure, decrease operative time, and may allow a faster post-operative recovery. This study has described a new high-resolution method of measuring tendon repair failure and may be useful in future studies.

Introduction: Previous studies have demonstrated that exposure of normal bovine and human osteoarthritic cartilage to n-3 polyunsaturated fatty acids (PUFAs) such as those present in fish oils can modulate the expression and activity of the degradative and inflammatory factors that are responsible for cartilage destruction [1,2]. In these studies, supplementation of cartilage explant cultures with n-3 PUFAs resulted in an abrogation of aggrecanase activity as well as mRNA expression of mediators of inflammation. To date, few studies have examined the effect of PUFAs on the metabolism of other tissues within the musculoskeletal system, therefore the present work examines the effect of n-3 PUFA supplementation on tendon metabolism.

Methods: Bovine deep digital flexor tendon explants were obtained from the compressed region of young metacarpophalangeal joints (2-week-old) and supplemented with eicosapentaenoic acid (EPA), as previously described [2]. Release of proteoglycan metabolites was analysed using Western blotting whilst RT-PCR analysis was used to examine the mRNA expression patterns of matrix proteases and inflammatory agents.

Results: Exposure to the n-3 fatty acid, EPA, markedly changed the overall lipid composition profile of the tendon with major changes occurring in the supplemented fatty acid (i.e., EPA), with a concomitant percentage reduction in other polyunsaturated fatty acids. Aggrecanase activity was present in the media from control cultures, as expected [3]. However, supplementation with EPA had no effect on this activity, in contrast to articular cartilage where aggrecanase catabolites were absent from the conditioned media following treatment with n-3 PUFAs [1,2]. mRNA expression for the inflammatory mediators (COX-2, IL-1β, TNF), ADAMTS-5, MMPs and TIMPs was also unchanged following supplementation with EPA, again contrasting with articular cartilage where mRNA expression was abolished.

Discussion: This study demonstrates that exposure of bovine tendon explant cultures to an n-3 PUFA, EPA, had no effect on the mRNA expression or activity of aggrecanases; similarly, expression of the inflammatory mediators was also unaffected. Importantly, within this musculoskeletal tissue, aggrecanases are constitutively active and appear to be involved in normal, everyday turnover of aggrecan, in contrast to non-pathological articular cartilage where aggrecanase-generated metabolites are only detected following treatment with catabolic agents. Similarly, COX-2 mRNA expression is present constitutively within tendons whereas in cartilage it is absent under basal (unstimulated) conditions. These data demonstrate that the incorporation of n-3 PUFAs have a differential effect on the regulatory mechanisms which control gene expression within articular cartilage versus tendon.