A cadaveric survey of the thoracic spines of extant species of nonbipedal primates for the presence of Scheuermann kyphosis.
To determine the presence and prevalence of Scheuermann kyphosis in quadrupedal species of the closest living relatives to humans to demonstrate that bipedalism is not an absolute requirement for the development of Scheuermann kyphosis.
The etiology of Scheuermann kyphosis remains poorly understood. Biomechanical factors associated with upright posture are thought to play a role in the development of the disorder. To date, Scheuermann kyphosis has been described only in humans and extinct species of bipedal hominids.
Thoracic vertebrae from 92 specimens of Pan troglodytes (chimpanzee) and 105 specimens of Gorilla gorilla (gorilla) from the Hamann-Todd Osteological Collection at the Cleveland Museum of Natural History were examined for Scheuermann kyphosis on the basis of Sorenson criteria and the presence of anterior vertebral body extensions and for the presence of Schmorl nodes.
Two specimens of P. troglodytes (2.2%) were found to have anatomic features consistent with Scheuermann kyphosis including vertebral body wedging greater than 5° at 3 or more adjacent levels and the presence of anterior vertebral body extensions. One of the affected specimens (50%) demonstrated the presence of Schmorl nodes whereas 2 of the unaffected specimens (2.2%) had Schmorl nodes. None of the specimens of G. gorilla (0%) were found to have anterior vertebral body extensions characteristic of Scheuermann kyphosis or Schmorl nodes.
Thoracic kyphotic deformity consistent with Scheuermann kyphosis exists in quadrupedal nonhuman primates. Bipedalism is not a strict requirement for the development of Scheuermann kyphosis, and the evolutionary origins of the disease predate the vertebral adaptations of bipedal locomotion.
Scheuermann kyphosis has been described only in humans and extinct species of bipedal hominids. This cadaveric study demonstrates the presence of Scheuermann kyphosis in a quadrupedal hominid, Pan troglodytes (chimpanzee). The results show that upright posture and habitual bipedal locomotion are not strict requirements for the development of Scheuermann kyphosis.
*St. Mary's Medical Center, San Francisco, CA
†San Francisco Orthopaedic Residency Program, St. Mary's Medical Center, San Francisco, CA; and
‡The Taylor Collaboration, San Francisco, CA.
Address correspondence and reprint requests to Brian M. Farrell, MD, San Francisco Orthopaedic Residency Program, St. Mary's Medical Center, 450 Stanyan St., San Francisco, CA 94117; E-mail: email@example.com
Acknowledgment date: March 15, 2012. First revision date: July 29, 2012. Acceptance date: August 3, 2012.
The manuscript submitted does not contain information about medical device(s)/drug(s).
No funds were received in support of this work.
One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., honoraria, gifts, consultancies, royalties, stocks, stock options, decision-making position.