A Tissue Engineering Approach for Treating Early Osteonecrosis of the Femoral Head

Abstract

Early osteonecrosis of the femoral head (ONFH), without structural collapse or subsequent degeneration of the overlying articular cartilage, presents the clinician with an opportunity to save the hip joint and thus avoid joint replacement surgery. To accomplish this goal, core decompression, in which the osteonecrotic segment of the femoral head is drilled, was devised. This operation stimulates a localized response to injury, similar to fracture healing. However, this procedure may not fully address two important issues: the need for vascular and osteogenic progenitor cells in an area with a compromised blood supply, and the need for structural support to “shore up” the involved segment of the femoral head. The current manuscript puts forth the thesis that in order to salvage the femoral head ideally, novel tissue engineering approaches to ONFH are needed that address both the biological and mechanical deficiencies. This would entail providing viable progenitor cells, currently obtained from concentration of iliac crest aspirates, together with a structural scaffold to help withstand physiological loads and supply a template for cell attachment and growth. By using this combined approach, it is hoped the natural hip joint could be maintained in this younger, highly active patient population with ONFH. Osteonecrosis of the femoral head (ONFH) is a painful progressive disorder in which cells within the femoral head die. In early ONFH, the head is still round and the hip is not arthritic and still salvageable. This presents the clinician with opportunities to save the hip rather than replace it with artificial components. The most logical approach to accomplishing this goal is to provide biomechanical structural support to the femoral head while new cells repopulate the dead areas. This latter goal may involve injecting concentrated bone and vascular progenitor cells, harvested from the patient, into the femoral head for biological healing. Preclinical studies should test novel in vivo treatments that provide both mechanical support and delivery of progenitor cells for early-stage ONFH. Future clinical studies derived from these preclinical studies should validate the safety and efficacy of these treatment principles for femoral head retention using combined biomechanical and biological treatments.