Fracture of the cobalt-chromium modular femoral neck component in total hip arthroplasty.

Total hip prostheses using cervico-metaphyseal modularity were designed to better replicate the geometry of the native extra-medullary femur. However, they are associated with numerous complications including corrosion, disassembly, pseudotumours and, most notably, fractures of the modular neck. All reported cases of modular neck fractures occurred with titanium components (Ti-6Al-4V). To prevent this weakness, manufacturers developed modular necks made of cobalt-chromium (Co-Cr). We report a fracture of a long, 8° varus, Co-Cr modular neck connected to a 36-mm short (-3.5mm) femoral head. The fracture occurred 22 months post-implantation in a woman who had a low level of physical activity and a body mass index of 28.7 kg/m(2). To our knowledge, this case is the first reported instance of Co-Cr modular neck fracture. It may challenge the wisdom of further developing this modularity design, as our patient had none of the known risk factors for modular neck fracture. In addition, cases of pseudotumour have been reported with Co-Cr modular necks subjected to fretting corrosion, which contributed to the fracture in our patient.

[Use of bone SPECT of the dorsolumbar spine in oncological patients with suspected bone metastases]. / Utilidad del SPECT óseo de columna dorsolumbar en pacientes oncológicos con sospecha de metástasis óseas.

UNLABELLED: A retrospective study was made to evaluate the usefulness of bone SPECT of the dorsolumbar spine in identifying benign and malignant lesions. A study was made of oncological patients who presented active images in the spinal column visible on planar radionuclide scans who also underwent SPECT. The average follow-up period was 25+/-13 months. MATERIAL AND METHOD: In 43 neoplastic patients 55 visible lesions on SPECT were evaluated, of which 29 were benign and 26 metastatic. The criteria for benign lesions were the absence of change or involution without treatment in the follow-up period. The criteria for classifying metastases were: 1. Positive biopsy. 2. Neurological complications derived from the lesion. 3. Increased extension and tracer uptake by the lesion, and the appearance of other bone metastases. RESULTS: Twelve of 15 lesions located in the vertebral body or pedicle and 11/16 located in the body with extension toward the pedicles were metastases. Twenty-one of 24 lesions located on the anterior face of the vertebral body, articular processes, lamina, or intervertebral disk were benign. CONCLUSION: Bone SPECT was useful for locating the vertebral lesion, which in many cases allows differentiation of benign and metastatic lesions.