Localized SDF-1α Delivery Increases Pro-Healing Bone Marrow-Derived Cells in the Supraspinatus Muscle Following Severe Rotator Cuff Injury.

To examine how the chemotactic agent stromal cell-derived factor-1alpha (SDF-1α) modulates the unique cellular milieu within rotator cuff muscle following tendon injury, we developed an injectable, heparin-based microparticle platform to locally present SDF-1α within the supraspinatus muscle following severe rotator cuff injury. SDF-1α loaded, degradable, N-desulfated heparin-based microparticles were fabricated, injected into a rat model of severe rotator cuff injury, and were retained for up to 7 days at the site. The resultant inflammatory cell and mesenchymal stem cell populations were analyzed compared to uninjured contralateral controls and, after 7 days, the fold-change in anti-inflammatory, M2-like macrophages (CD11b+CD68+CD163+, 4.3X fold-change) and mesenchymal stem cells (CD29+CD44+CD90+, 3.0X, respectively) was significantly greater in muscles treated with SDF-1α loaded microparticles than unloaded microparticles or injury alone. Our results indicate that SDF-1α loaded microparticles may be a novel approach to shift the cellular composition within the supraspinatus muscle and create a more pro-regenerative milieu, which may provide a platform to improve muscle repair following rotator cuff injury in the future.

The effect of flexor digitorum profundus tendon shortening on jersey finger surgical repair: a cadaveric biomechanical study.

Delayed diagnosis of jersey finger injuries often results in retraction of the flexor digitorum profundus tendon. Current practice recommends limiting tendon advancement to 1 cm in delayed repairs. The purpose of this study was to investigate the biomechanical consequences of tendon shortening on the force required to form a fist. The flexor digitorum profundus muscle was isolated in ten cadaveric forearms and the force required to form a fist was recorded. Simulated jersey finger injuries to the ring finger were then created and repaired. The forces required to pull the fingertips to the palm after serial tendon advancements were measured. There was a near linear increase in the force required for making a fist with shortening up to 2.5 cm. The force required to make a fist should be taken into account when considering the limit of 'safe' tendon shortening in delayed repair of jersey finger injuries.

Obesity and symptomatic osteoarthritis of the knee.

Given the growing prevalence of obesity around the world and its association with osteoarthritis of the knee, orthopaedic surgeons need to be familiar with the management of the obese patient with degenerative knee pain. The precise mechanism by which obesity leads to osteoarthritis remains unknown, but is likely to be due to a combination of mechanical, humoral and genetic factors. Weight loss has clear medical benefits for the obese patient and seems to be a logical way of relieving joint pain associated with degenerative arthritis. There are a variety of ways in which this may be done including diet and exercise, and treatment with drugs and bariatric surgery. Whether substantial weight loss can delay or even reverse the symptoms associated with osteoarthritis remains to be seen. Surgery for osteoarthritis in the obese patient can be technically more challenging and carries a risk of additional complications. Substantial weight loss before undertaking total knee replacement is advisable. More prospective studies that evaluate the effect of significant weight loss on the evolution of symptomatic osteoarthritis of the knee are needed so that orthopaedic surgeons can treat this patient group appropriately.

The 2.5 mm PushLock suture anchor system versus a traditional suture anchor for ulnar collateral ligament injuries of the thumb: a biomechanical study.

We compared the biomechanical strength of the 2.5 mm PushLock suture anchor with a traditional Bio-SutureTak suture anchor in repair of ulnar collateral ligament injuries. Iatrogenic ulnar collateral ligament injuries in 18 cadaveric thumbs were repaired and used to test for load to failure and cyclic loading. The average force required to generate a 2 mm gap was 7.7 N for the 2.5 mm PushLock and 6.3 N for the Bio-SutureTak (p = 0.04). The ultimate load to failure was 28.0 N for the 2.5 mm PushLock and 18.8 N for the Bio-SutureTak (p = 0.16). There were no statistical differences between the two suture anchors under cyclic loading. The 2.5 mm PushLock suture anchor provides significantly stronger resistance to 2 mm gap formation at the repair site and is less likely to fail at the suture-ligament interface. However, there was no difference in the load to failure between the two suture anchors.