Innovative Hip replacement for Protrusion of cup

Dec. 29, 2010 - PRLog -- Proxima Hip Replacement in Protrusio acetabula
Dr.A.K.Venkatachalam, Consultant Orthopedic surgeon, Chennai, India
Protrusio acetabuli is a medialisation of the medial wall of the acetabulum. The head of the femur lies medial to the Ilio-ischial or Kohler’s line.
•   It is the result of remodeling of weak, medial acetabular bone after multiple, recurring stress fractures
•   Migration occurs along the resultant joint-reaction force vector
•   There is a number of causes, the common ones being secondary to inflammatory cause (inflammatory destruction) or metabolic cause (qualitative deficiency in the bone).
This case of protrusio acetabuli in a 25 year young male resulted from a long standing central fracture dislocation of the acetabulum. Stiffness and short limbed gait were the presenting symptoms. Other symptoms encountered commonly are progressive pain.
Radiological findings- The medial wall of the acetabulum lies medial to the Ilio Ischial line.

Traditional treatment has been total hip replacement. Since many cases occur in young patients, a conventional total hip replacement is not ideal since it removes more host bone. Invariably a revision hip replacement will be required in a young patient undergoing a total hip replacement. A bone sparing option like Hip resurfacing or short-stem hip replacement is preferable. Hip resurfacing is possible in mild grades where bone grafting is not required. In the more severe grades, bone grafting is mandatory. An anti protrusio cage can also be used to reconstruct a severe medial wall deficiency. In advanced grades of protrusion, placement of the cup in the anatomical position is crucial for long term success. The cup has to rely on peripheral fixation with press fit and additional screws. Therefore hip resurfacing as an option goes out of the realm.  
In the present case, an innovative approach was adopted for hip reconstruction. Hip resurfacing was ruled out because of the necessity for bone grafting and severity of the condition (Grade III in this case)
A bone sparing Proxima hip replacement was planned. The uncemented Pinnacle cup was lateralized by bone grafting. Peripheral fit and screw fixation achieved a snug interference fit. A metal liner was used.
Hard on hard bearings were chosen in view of their established favorable long term outcomes. Hard on cross linked poly was not chosen because of the lack of long term results. On the femoral side, a Proxima stem with a Ceramic 36 mm head was used.
As can be seen, the Proxima hip is a stem less femoral implant. It gains purchase in the proximal cancellous bone of the femur. It sacrifices very little bone from the head of the femur. Most of the neck portion is left intact.              
This is probably the first case of Proxima hip replacement done for a case of Protrusio acetabuli.
This operation was performed by consultant Orthopaedic surgeon
Dr.A.K.Venkatachalam.
MS Orth, DNB Orth, FRCS, M.Ch Orth
Chennai Meenakshi mult-specialty hospital
Chettinad hospital
Visit www.hipsurgery.in.

# # #

Orthopedic surgery centre in Chennai offers hip resurfacing, Hip, Knee & Shoulder replacements at affordable costs in 5 * private hospital