N. Santori (Rome, Italie)
Two step strategy for THA in AVN of the femoral head.
Several orthopaedic procedures have been developed treasuring previous experiences of dental surgery. The feasibility of total hip replacement with a two step approach was evaluated. Rationale for this procedure follows the philosophy of dental implantology. In the first step a titanium fiber mesh rod with a proximal Morse cone is implanted in the proximal metaphysis trough a 2 centimetres incision in day surgery. Immediate, full weight bearing is allowed. In the 2° phase, 6 months after rod implant, the femoral head is replaced and the cup implanted.
Experimental trials were performed in a series of 29 mongrel dogs operated using the same implant either in a single or in two subsequent steps. The second experimental investigation was performed in a series of 26 sheep again in one or two steps. Bone ingrowth was evaluated with micro radiography and histology.
A human series of 75 rods has been implanted since may 2001. In 15 cases the rod was implanted for avascular necrosis and associated with forage biopsy, in 60 cases for osteoarthritis.
In 35 human cases the second step with total hip replacement was performed.
The experimental studies gave clear evidence of the value of the two step approach. Animals operated in a single step had a 90% rate of early loosening because on the early uncontrolled full weight bearing. Dogs operated in two steps did well.
In two cases of the human series, the rod was found to be loose at the time of the second step and a conventional THR implant was applied. Both these cases had first been operated for AVN. At an average 19 months follow-up the remaining 33 patients are doing well. Radiographic evolution is good.
A totally new philosophy for total hip replacement is being evaluated. Theoretically, it allows the best environment for implant integration, minimal bony resections and immediate full weight bearing. Experimental and first human clinical results show interesting results.