Age-related degenerative functional, radiographic, and histological changes of the shoulder in nonhuman primates

Abstract

Background Non-human primates have similar shoulder anatomy and physiology compared to humans and may represent a previously underutilized model for shoulder research. This study sought to identify naturally occurring bony and muscular degeneration in the shoulder of non-human primates and to assess relationships between structural and functional aspects of the shoulder and measures of physical function of the animals. We hypothesized that age-related degenerative changes in the shoulders of non-human primates would resemble those observed in aging humans. Methods Middle-aged (n=5, ages 9.4 to 11.8 years) and elderly (n=6, ages 19.8 to 26.4 years) female vervet monkeys were studied for changes in mobility and shoulder function, and radiographic and histologic signs of age-related degeneration. Results Four out of six (4/6) elderly animals had degenerative changes of the glenoid compared to 0/5 of the middle-aged animals (p=0.005). Elderly animals had glenoid retroversion, decreased joint space, walked slower and spent less time climbing and hanging than middle-aged vervets (p<0.05). Physical mobility and shoulder function correlated with glenoid version angle (p<0.05). Supraspinatus muscles of elderly animals were less dense (p=0.001), had decreased fiber cross-sectional area (p<0.001), but similar amounts of nuclear material (p=0.085). Degenerative rotator cuff tears were not observed in any of the eleven animals. Discussion and Conclusion The vervet monkey naturally undergoes age-related functional, radiographic and histological changes of the shoulder and may qualify as an animal model for selected translational research of shoulder osteoarthritis. Level of evidence Basic Science Study, in-vivo Animal Model

High Incidence of Hemiarthroplasty for Shoulder Osteoarthritis Among Recently Graduated Orthopaedic Surgeons

“…Walch et al [24] showed that increasing age was associated with increased glenoid retroversion in patients with primary glenohumeral arthritis. Similar results have also been found in studies of non-human primates [19]. However, it is possible that in patients where the arthritis has progressed to the point of needing a shoulder arthroplasty, age no longer predicts the amount of glenoid wear, and by extension the need for glenoid resurfacing.…”

Age-related structural changes in upper extremity muscle tissue in a nonhuman primate model

“…Reductions in muscle fiber force in the vastus lateralis were present in older vervets, 7 although it is unclear if the upper extremity musculature experiences the same decline. Older vervets demonstrated age-related deteriorations of the shoulder similar to reports in older adult humans including; degeneration of the glenoid, increased glenoid retroversion, and decreased supraspinatus superficial cross-sectional area.. 31 Similarly, measures of physical performance that incorporate the upper extremity were diminished in older vervets. 7,31,39 However, within this vervet species, age-related changes to the upper extremity musculature have not been evaluated and degenerative rotator cuff tears, a common age-related injury affecting older adult humans, 44 have not been described.…”

“…An animal model of upper extremity aging would more easily allow for longitudinal studies by limiting many of the logistical concerns associated with human subjects. Unfortunately, data regarding musculoskeletal degeneration in animals resulting strictly from normal aging are limited 7,12,24,31,32 and many of the animal models are small, quadrupedal, or have bony geometry that is substantially different from that of a human. 9,22,31 A non-human primate model may offer a solution that mitigates many of these problems.…”

Animal Models of Osteoarthritis

“…Although experimental models of disease do exist, 85 a major advantage of these species is the development of naturally occurring OA in multiple joints that very closely mimics the onset and progression seen in aging humans. 23,24,55,86,120 Disease severity and age are closely correlated in this model, but the spectrum of disease across ages mimics that seen in humans, with some younger animals affected with moderate disease (particularly young males) and some elderly individuals spared entirely. 55,86 Although the joint biomechanics of nonhuman primates do differ from humans, they are more similar than those of strict quadrupeds.…”