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