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Intrapelvic protrusion of the acetabular component following total hip replacement
Insights
Intrapelvic protrusion after total hip replacement can occur in patients with severe bone defects. Preserving acetabular bone stock and using low-friction prostheses are crucial to prevent this complication.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
Background:
- Total hip replacement (THR) is a common procedure for hip joint pathology.
- Severe protrusio acetabuli and osteoporosis present unique challenges in THR.
Observation:
- Five patients experienced acetabular component protrusion into the true pelvis post-THR.
- Four patients had rheumatoid arthritis; one had degenerative hip disease.
- Preoperative conditions included severe protrusio acetabuli, thin medial acetabular walls, and osteoporosis.
Findings:
- McKee-Farrar prostheses (metal-to-metal) were used in four cases, noted for high friction and lack of damping.
- Failure to preserve medial acetabular bone stock increases protrusion risk.
- Loosened prostheses can cause progressive bone reabsorption, leading to irreparable loss.
Implications:
- Meticulous preservation of medial acetabular bone stock is essential.
- Use low-friction prosthetic devices and acrylic cement for stress distribution.
- Careful component orientation and reinforcement of defective medial walls (bone grafting/wire mesh) are recommended.
- Reoperation for loosened components is indicated to prevent further bone loss.
Abstract:
Protrusion of the acetabular component into the true pelvis following total hip replacement has occurred in 5 patients, 4 with severe rheumatoid arthritis and 1 with a destructive type of degenerative hip disease. Preoperatively all hips had severe protrusio acetabuli, a markedly thin acetabular medial wall and advanced osteoporosis. Four had a McKee-Farrar prosthesis, a metal-to-metal device with high frictional torque, particularly when the contact is equatorial, and no damping capacity against marginal impingement in the extreme range of motion. In order to reduce the incidence of intrapelvic protrusion, extreme care should be given to preserve the medial bone stock of the acetabulum, more so when it is already damaged or defective. If anchoring holes are used they should be restricted to the superior ilium, pubis and ischium and should not perforate the medial wall. Once loosening is present, reoperation is indicated to avoid progressive bone reabsorption by the abrasive motion of the loosened prosthesis, that might lead to irreparable bone loss. To reduce the stress transmitted to an already weakened acetabulum, select a total prosthetic device with low friction; fix it with acrylic cement in order to distribute the stress over a large surface; carefully orient both components to avoid marginal impingement; be certain to preserve the medial wall as much as possible and if it is already defective reinforce it by bone grafting and/or wire mesh.