Introduction Sequestered disc fragments in the achondroplastic dwarf are rare. They should be removed by an anterior approach because:

access to remove the fragment posteriorly is severely compromised by the condition.

Method The case is of a 30 year old achondroplastic dwarf with spontaneous sudden onset of myelopathy over three myotomes. An MRI scan revealed an L1-2 large disc herniation compressing the thecal sac in an already small canal.

Results The spinal decompression resulted in recovery from the paresis without creating the instability associated with a wide posterior exposure.

Discussion The thoraco-abdominal approach involves incision along the line of the rib two levels above the most proximal vertebral body to be visualized. The external oblique and internal oblique are incised in the line of the rib. The diaphragm is taken down from the costal cartilage to the crus posteriorly allowing access to the upper lumbar spine. The segmental vessels are identified and subperiosteal dissection carried out. The disc is excised and the adjacent posterolateral vertebral body extending toward the segmental vessels. The neural elements are decompressed and the spine is stabilized using the rib strut as graft in the space created by the vertebral resection with morselized graft into the intervertebral disc space.

Total hip arthroplasty (THA) using modular components offers many advantages such as a reduction in the implant inventory required and increased intra-operative flexibility with component sizing and selection. However, it also comes at the price of the additional complication of component dissociation, in particular at the non-fixed interface between the polyethylene cup and the acetabular metal backing.

A review of 110 patients requiring revision THA from June 1993 to December 2000 performed by the senior authors revealed seven patients presenting with the triad of signs suggestive of this complication – a previously successful, painless THA that had become acutely painful and with radiographic evidence of femoral head asymmetry in the acetabular cup. Each of these patients had Harris - Galante II porous acetabular cups. At the time of the revision, these patients were found to have dissociated polyethylene cup liners and several with broken locking mechanisms warranting replacement of the acetabular cups, the liners and the worn femoral heads.

This is an uncommon complication of THA, with characteristic presenting symptoms and signs. The importance of comparison of previous radiographs with those at presentation and the postulated mechanisms for dissociation is stressed. Certain precautions are imperative when using modular implants and the pitfalls of the Harris - Galante II porous acetabular component locking mechanism should be acknowledged.