Specialty Update: What’s New in Shoulder and Elbow Surgery (2005)

Tue, 01 Feb 2005 17:00:00 GMT

Sources

The sources for this annual update on shoulder and elbow surgery were presentations and symposia at meetings of the American Shoulder and Elbow Surgeons (October 8 through 11, 2003, and March 13, 2004), the Arthroscopy Association of North America (November 13 through 16, 2003; March 13, 2004; and April 23 through 25, 2004), the Orthopaedic Re-search Society (March 6 through 9, 2004), the American Academy of Orthopaedic Surgeons (March 9 through 13, 2004), the American Orthopaedic Society for Sports Medi-cine (March 13, 2004), and the American Orthopaedic Asso-ciation (June 23 through 26, 2004).

Shoulder
Rotator Cuff
Basic Science

Zuckerman discussed the early work on cartilage-derived morphogenetic protein-2 (CDMP-2). Rat tendon repairs that had been treated with CDMP-2 were stronger than untreated repairs at four weeks. Dines discussed his initial investigations involving platelet-derived growth factor (PDGF) and insulin-like growth factor-1 (IGF-1). Studies at his laboratory demon-strated that cultured rat fibroblasts could be transduced with the genes from the growth factors and then seeded onto a polymer scaffold and cultured to form tissue-engineered ten-don constructs. Fibroblasts apposed to the tissue engineered constructs containing the IGF gene demonstrated up to a ten-fold stimulation of collagen synthesis compared with con-structs with the gene. The author stated that he hopes that this research can lead to the development of biologically active patches capable of accelerating and modulating rotator cuff repair.

Kikugawa reported on the effects of synovial tissue and growth factors on rotator cuff healing. A supraspinatus ten-don defect was created in forty-eight rats. In half of the rats, the defect was filled with synovial tissue. Compared with the specimens without synovial tissue-filled defects, specimens with filled defects appeared to be more mature, with more-intense staining for TGF-α and increased production of type-I and type-III procollagen. These findings suggest that synovial tissue plays an important role in modulating tendon-healing and that expression of TGF-α may influence the synovial tis-sue in this role.

Sprott investigated the potential for reversal of fatty infiltration following rotator cuff repair in a rabbit model. Fifteen rabbits underwent unilateral detachment of the su-praspinatus tendon from the greater tuberosity. Six weeks following detachment, five rabbits were killed to halt the fatty infiltration process and ten underwent repair of the rotator cuff followed by unrestricted activity. The ten rabbits in the repair group were killed at six months. At six weeks following detachment, significant fatty infiltration was demonstrated (p = 0.001). At six months following repair, the muscle dem-onstrated no further increase in fat (p = 0.03), suggesting that the process of fatty infiltration associated with chronic rotator cuff detachment can be halted, but not reversed, by repair.

Meyer used computerized tomography and both light and electron microscopy to study fatty muscle changes that occur after a rotator cuff tear in a sheep model. Eight sheep underwent unilateral infraspinatus tendon release and delayed repair. Seventy-five weeks after the repair, significant in-creases in muscle retraction and pennation angle as well as significant muscle-fiber shortening (p < 0.0001) were identi-fied. Interstitial fat and fibrous tissue increased from 4% to 46% of the muscle volume. On the basis of geometric model-ing, the authors concluded that the fatty tissue may fill spaces created by the combination of retraction, shortening, and changes in pennation angle. These findings contradict cur-rent thinking that the fatty changes represent primarily a de-generative process.

Bishop evaluated the changes in muscle fatty infiltration and atrophy following rotator cuff repair. Preoperative and postoperative magnetic resonance imaging was used to grade fatty infiltration on a 5-point scale and muscle atrophy on a 4-point scale. Fatty infiltration and muscle atrophy correlated positively with tear size (p < 0.0001, r = 0.712). Moreover, American Shoulder and Elbow Surgeons (ASES) and Constant scores as well as strength measurements correlated inversely with fatty infiltration and muscle atrophy (p < 0.03). Repeat tear was associated with fatty infiltration of the supraspinatus and weakness in forward flexion, and external rotation was most strongly associated with fatty infiltration of the in-fraspinatus. However, pain relief was independent of the de-grees of fatty infiltration and muscle atrophy.

Cohen reported on the inhibitory effects of traditional nonsteroidal anti-inflammatory drugs and cyclooxygenase-2- selective inhibitors on rotator cuff tendon-healing in a rat model. Following rotator cuff detachment and repair, 180 rats were randomly assigned to receive celecoxib, indomethacin, or no drug. Groups of animals were killed at two, four, and eight weeks postoperatively, and the tendons were subjected to bio-mechanical and histologic evaluation. The author found that load to failure was significantly lower in the indomethacin and celecoxib groups compared with the control group at two, four, and eight weeks. In contrast to both treatment groups, the control group exhibited improved collagen maturity and organization at the tendon-insertion site. The results demon-strate that both traditional nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors significantly impair tendon-to-bone healing in the rat rotator cuff.

Tingart evaluated the effect of suture anchor design and bone density on the pullout strength of suture anchors used for rotator cuff repair. The trabecular and cortical bone min-eral density was determined for six regions within the greater tuberosity. Metal screw-type and biodegradable hook-type su-ture anchors were inserted into each region and were cyclically loaded until failure. Metal anchors failed at an average 66% higher load than bioabsorbable anchors did (p < 0.01). For both anchor types, failure loads correlated with bone-mineral density and were significantly higher in the proximal tuberos-ity (p < 0.01).

1-Feb-05 11:00 AM

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Specialty Update: What’s New in Shoulder and Elbow Surgery (2005)