Abstract
Protrusio acetabuli can be either primary or secondary. Primary or idiopathic protrusio is a rare condition of unknown etiology. Secondary protrusio may be associated with rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, osteomalacia, trauma and Paget's disease. Challenges in surgery include: lack of bone stock, deficient medial support to the cup, difficulty in dislocating the femoral head, and medialization of the hip joint center. Several surgical techniques have been described: use of cement alone without bone graft; morselised impacted autograft or allograft with a cemented cup; metal cages, reinforcement rings, and solid grafts.
We describe our technique of impaction grafting using autologous bone and a cementless porous-coated hemispherical cup without the use of acetabular rings or cages in patients with an average age of 46 years. Protrusion was graded depending on distance of medial wall from Kohler's line as mild (1–5 mm medial), moderate (6–15 mm medial) and severe if it was more than 15 mm medial to the Kohler's line. All patients were operated in the lateral position using a modified Hardinge's anterolateral approach. Adductor tenotomy may be required in cases of severely stiff hips. After careful dislocation of the femoral head, it was sectioned in situ into slivers to facilitate obtaining the graft. The periphery was reamed and care was taken to preserve the membrane lining the floor of the defect. Morselised graft was impacted with hemispherical impactors and the trial cup 1–2 mm larger than the last reamer placed in the desired position. The final socket was then inserted. Femoral preparation was performed in routine fashion.
The mean pre-operative Harris Hip Score of 52 improved to 85 points at a mean follow up of 4 years. The average acetabular inclination angle was 42 degrees. Our results have shown incorporation of the graft in all cases. There was no evidence of progression of the protrusio or cup loosening in any of the cases. Thus far, our hips have not shown osteolytic lesions. The technique described is a satisfactory biological solution of restoring bone stock particularly in young and middle-aged patients.
