A large or aspherical femoral head can be made smaller and round to improve hip function with surgery. Based on the location of the asphericity and the importance of the cartilage overlying the aspherical part, various techniques are available. Moving the bump away from the acetabulum is an alternative if the contact area and hip motion will be adequate.
Excision of aspherical portion
If the aspherical part is out of the weight bearing area and the cartilage covering it is not required for hip function, the aspherical part can be simply removed till the head is small and round to fit the socket well. Femoral neck osteoplasty and excision of one lobe of a bilobed head are examples.
Head Reshaping and Reduction retaining overlying cartilage
A bump in the weight bearing part of the head needs retention of the cartilage covering the bump. Undercutting and removing the bone under the bump can reduce the bump and make the head rounder without removing the overlying cartilage.
Central Head Reduction Osteotomy
This is a powerful technique to make a large round head smaller, flat head rounder, and remove unhealthy cartilage from central parts of the head. It requires experience with surgical dislocation, extended retinacular flap development, and creativity to design the bone cuts to match the two halves after excising some of the central part of the head. Preop templating helps, but intraoperative versatility is required to get the best results.
- Hinged Abducted from a large head not fitting the acetabulum
2. Central part of the head removed
3. The smaller head fit the socket well after head reduction osteotomy