Revisiting scoliosis in the KNM-WT 15000 Homo erectus skeleton

Abstract

Owing to its completeness, the 1.5 million year old Nariokotome boy skeleton KNM-WT 15000 is central for understanding skeletal biology of Homo erectus. Nevertheless, since Latimer and Ohman (2001, Axial dysplasia in Homo erectus. J Hum Evol 40:A12) reported on asymmetries and distortions of Nariokotome boy's axial skeleton suggesting adolescent idiopathic scoliosis, possibly associated with congenital skeletal dysplasia, it is questionable whether it still can be used as reference for Homo erectus. Recently, however, the presence of skeletal dysplasia has been refuted. Here, we present a morphologic and morphometric reanalysis of the assertion of idiopathic scoliosis. We demonstrate that unarticulated vertebral columns of non-scoliotic and scoliotic individuals can be distinguished based on the lateral deviation of the spinous process, lateral and sagittal wedging, vertebral body torsion, pedicle thickness asymmetry and asymmetry of the superior and inferior articular facet area. A principal component analysis of the overall asymmetry of all seven vertebral shape variables groups KNM-WT 15000 within non-scoliotic modern humans. An anomaly of vertebrae T1-T2 is compatible with a short left convex curve at the uppermost thoracic region, possibly due to injury or local growth dysbalance. Asymmetries of the facet joints L3-L5 suggest a local right convex curve in the lower lumbar region that probably resulted from juvenile traumatic disc herniation. This pattern is incompatible with adolescent idiopathic scoliosis or other types of scoliosis, including congenital, neuromuscular or syndromic scoliosis. It is, however, consistent with a recent reanalysis of the rib cage that did not reveal any asymmetry. Except for these possibly trauma-related anomalies, the Nariokotome boy fossil therefore seems to belong to a normal Homo erectus youth without evidence for adolescent idiopathic scoliosis or other severe pathologies of the axial skeleton. AbstractOwing to its completeness, the 1.5 million year old Nariokotome boy skeleton KNM-WT 15000 is central for understanding skeletal biology of Homo erectus. Nevertheless, since Latimer and Ohman (2001, Axial dysplasia in Homo erectus. J Hum Evol 40:A12) reported on asymmetries and distortions of Nariokotome boy's axial skeleton suggesting adolescent idiopathic scoliosis, possibly associated with congenital skeletal dysplasia, it is questionable whether it still can be used as reference for Homo erectus. Recently, however, the presence of skeletal dysplasia has been refuted. Here, we present a morphologic and morphometric reanalysis of the assertion of idiopathic scoliosis. We demonstrate that unarticulated vertebral columns of non-scoliotic and scoliotic individuals can be distinguished based on the lateral deviation of the spinous process, lateral and sagittal wedging, vertebral body torsion, pedicle thickness asymmetry and asymmetry of the superior and inferior articular facet area. A principal component analysis of the overall asymmetry of all seven vertebral shap...

Palaeopathology: Current challenges and medical impact

“…Latimer and Ohman () diagnosed in this fossil the oldest case of congenital dysplasia of the axial skeleton. Yet, a recent reanalysis of the Nariokotome boy rejected this claim (Schiess and Haeusler, ; Schiess et al, ; Meyer and Haeusler, ). Instead, a nearthrosis was discovered between the left superior articular process of the fifth lumbar vertebra (L5) and the inferior side of the pedicle of L4 (Haeusler et al, ).…”

Case study: Scoliosis in a Bonobo (Pan paniscus)

“…These characteristics include lateral wedging of the vertebral body, horizontal torsion of spinous process and vertebral body, and asymmetry of the neural arch, transverse, and articular processes. The additional characteristic pedicle width asymmetry was also assessed. The presence of osteoarthritis (OA) was evaluated using criteria for human skeletons:the presence of osteophytes, joint surface remodeling, and/or eburnation (loss of subchondral bone)…”

“…The specimen exhibited no evidence for the severe malformations (e.g., fused ribs, hemivertebrae) that result in congenital scoliosis. Diagnosing idiopathic scoliosis in skeletal specimens is difficult; all clinical definitions require measurements from radiographs of live patients, which is not possible for skeletonized individuals, and some require the involvement of 5 to 6 vertebrae . We therefore relied on evaluating whether the skeletal criteria for scoliosis were present.…”

“…Because only 2 vertebrae are involved, this case may not meet all criteria for idiopathic scoliosis and may be an instance of physiological scoliosis. Both idiopathic and physiological scoliosis have, however, been considered the result of human obligate bipedalism …”

“…Congenital scoliosis results from segmentation error deformities, for example, hemivertebrae, block vertebrae, fused ribs . The etiology of idiopathic scoliosis is less clear, and is hypothesized to be unique to humans due to obligate bipedalism . The human vertebral column bears large amounts of vertical and shear loading, and maintains the center of mass directly over the pelvis during locomotion .…”