PubMed · 1202449
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J J Herbert, A Herbert. 1975-11-01. [A new total hip prosthesis].. https://pubmed.ncbi.nlm.nih.gov/1202449/
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Although subchondral changes are reported to be associated with transient osteoporosis of the hip (TOH), the etiology of this disorder is unknown.In this paper, we describe a 45-year-old man with TOH who underwent both MRI and CT examinations. Plain radiographs obtained 2 months after the onset of hip pain showed a focal loss of radiodensity in the left femoral head. MRI revealed a bone marrow edema pattern in the left femoral head and neck with an associated subchondral serpiginous low signal intensity line on the T1-weighted images. A CT scan showed a subchondral fracture in the corresponding area. The hip pain and imaging abnormalities resolved spontaneously following conservative treatment. This case study demonstrated that a subchondral fracture of the femoral head was associated with TOH using MRI and CT examinations, and suggests that the presence of a subchondral fracture may be important for the pathophysiology of TOH.
Metal-on-metal hip arthroplasty has the longest clinical history of all total arthroplasties. We asked whether large diameter femoral heads would result in less wear than those with small diameters. We also asked if there is a threshold diameter that ensures good wear behavior. We tested three batches of cast high-carbon cobalt-chromium-molybdenum hip implants (28 mm, 36 mm, and 54 mm diameters) in a hip simulator for 5 million cycles. We used bovine serum as lubricant and weighed the samples at regular intervals during testing. The 28-mm configuration had almost twice the wear of the 54-mm configuration, but we observed no difference between the 36-mm and the 54-mm configurations. The similarity in the wear performances of the larger configurations supports the presence of a threshold diameter that ensures good wear behavior.
BACKGROUND: The prospect for success in the efficacy of osteotomy for precollapse stage of femoral head osteonecrosis depends on the ability to predict reliably the stress changes derived from specific osteotomies. A three-dimensional finite-element analysis was thus designed to compute necrotic femoral head stress changes with different extent of necrocrosis that accompany anterior or posterior rotational osteotomies. METHOD: Computed tomography images of a standard composite femur were used to create the three-dimensional finite-element intact femur model. Based on the intact model, 27 models simulating three different levels of necrotic region together with nine different rotational osteotomies were created. The von Mises stress distributions of each model were analyzed and compared for a loading condition simulating single-legged stance. FINDINGS: (1) The stress reduction in anterior rotational osteotomy is more effective as compared to that of the posterior rotational osteotomy for various necrotic lesion sizes. (2) Von Mises stress on the necrotic zone decreased with increasing rotational angle. The decreasing rate was higher for the femoral head with a narrow lesion. (3) Femoral head with a wider necrotic lesion had a higher risk for developing collapse due to high local stress on the surface of necrotic region; whereas the necrotic region tended to expand in size instead of collapse for femoral head with a narrow lesion due to high local stress on the interface between necrotic region and healthy bone. INTERPRETATION: Transtrochanteric rotational osteotomy is a technically demanding procedure and associated with high complication risks, a more scrupulous planning including the finite-element analysis should be considered before doing surgery in clinical subjects.