Recent advances in shoulder research

Abstract

Shoulder pathology is a growing concern for the aging population, athletes, and laborers. Shoulder osteoarthritis and rotator cuff disease represent the two most common disorders of the shoulder leading to pain, disability, and degeneration. While research in cartilage regeneration has not yet been translated clinically, the field of shoulder arthroplasty has advanced to the point that joint replacement is an excellent and viable option for a number of pathologic conditions in the shoulder. Rotator cuff disease has been a significant focus of research activity in recent years, as clinicians face the challenge of poor tendon healing and irreversible changes associated with rotator cuff arthropathy. Future treatment modalities involving biologics and tissue engineering hold further promise to improve outcomes for patients suffering from shoulder pathologies.

Figure 1

Total shoulder arthroplasty for treatment of severe glenohumeral osteoarthritis. (A) Pre-operative radiograph of an arthritic shoulder with typical loss of normal joint space. (B) Post-operative radiograph after total shoulder replacement of both humeral head and glenoid components. (C) Post-operative radiograph of a shoulder with a reverse shoulder arthroplasty for rotator cuff arthropathy.

Figure 2

Fatty accumulation in a rodent model of chronic rotator cuff degeneration. (A) A normal rat supraspinatus muscle stained with Oil red O showing very few intramuscular fat deposits and intramyocellular fat droplets. The supraspinatus tendon can be seen at the center of the muscle (arrow) and the muscle fibers can be seen above and below the tendon. (B) The infraspinatus muscle of a rat 16 weeks following tenotomy of the supraspinatus and infraspinatus tendons. There are high numbers of fat deposits (seen as red dots). (C) The infraspinatus muscle of a rat 16 weeks following tenotomy plus neurotomy showing high levels of intramuscular fat. (A-C) Oil red O stain; 10× objective. (D) Histology grading results are shown for intramuscular fat on Oil red O stained histology sections. Normal muscles showed no fat. After tenotomy of the supraspinatus (SS) and infraspinatus (IS) tendons, the infraspinatus muscle had more intramuscular fat than the supraspinatus muscle. The 16-week specimens had more intramuscular fat than the 8-week specimens within each group. Note that grading was semi-quantitative in nature; statistical comparison and error bars were therefore not calculated. Reproduced with permission from [50].

Figure 3

The tissue engineering paradigm. The tissue engineering paradigm consists of isolation and proliferation of a cell source, seeding of the cells onto a scaffold, stimulation of the cell-seeded scaffold to develop a tissue equivalent, and implantation of the construct in vivo. Figure reproduced under a Creative Commons Attribution 3.0 Unported license.