[The role of core decompression for the treatment of femoral head avascular necrosis in renal transplant recipients].

Avascular bone necrosis is a relatively rare but significant complication in renal transplant recipients because it causes progressive pain and invalidity. It can be the consequence of the action of numerous causative factors, but it is mostly connected to corticosteroid treatment.The underlying pathophysiologic mechanism is a diminished blood flow to the bone leading to necrosis and bone destruction. During the past 25-years period, 570 renal transplantations and five combined kidney and pancreas transplantations were performed in our centre. A part of the patients was lost to follow-up due to the separation of Croatia from the former Republic of Yugoslavia. After transplantation, we revealed aseptic necrosis of the femoral head in five female patients. All patients had a history of treatment with pulse doses of corticosteroids. At transplantation the average age of the patients was 52.2 yrs (range 46 to 62 yrs), and dialytic treatment before transplantation lasted in average 9.2 yrs (range 2.5 to 21.2 yrs). The period between renal transplantation and the development of clinical signs of avascular bone necrosis lasted in average 1.2 yrs (range 0.3 to 2.3 yrs). We will demonstrate our 62-year old female patient with terminal renal failure caused by post-streptococcal glomerulonephritis, who was treated with peritoneal dialysis 2.5 years before renal transplantation. Twenty months before renal transplantation the patient received pulse doses of corticosteroids, together with immunoglobulins and plasmapheresis, for the treatment of an acute polyradiculoneuritis Guillaine Barré. After transplantation a standard immunosuppressive protocol was applied which included tacrolimus, mycophenolate mofetil, corticosteroids and induction with basiliximab. Four months after transplantation the patient started to feel pain in the right hip after longer standing, in addition to the earlier long-lasting problems caused by bilateral coxarthrosis. The pelvic radiograph showed subchondral radiolucencies in the lateral part of the head circumference spreading into the proximal part of the neck of the right femur, which indicated the presence of aseptic necrosis, but these changes could have also been caused by coxarthrosis. Unexpectedly, magnetic resonance imaging (MRI) did not reveal changes characteristic for avascular bone necrosis. Due to the progressively worsening of pain and the radiographic finding, the patient was submitted to decompression surgery of the femoral head. The surgical procedure was performed under diascopic guidance (C-arm) which allowed the correct positioning of a Kuerschner wire. A cannulated drill (diameter 4.0 mm) was placed over the wire and we performed two drillings of the spongiosis of the femoral head through to the subchondral area. Postoperatively, the patient was soon verticalized and advised to walk with crooks during a period of six weeks. This time is necessary to allow the mineralisation and strengthening of the bone which is now better vascularised. The patient recovered well and had no more pain. In renal transplant recipients it is most important to raise suspicion and verify the presence of avascular bone necrosis early, because timely bone decompression surgery can eliminate pain and cure the patient or it can prevent or delay bone destruction. When clinical signs of avascular bone necrosis arise and radiographic or standard MRI findings are negative, additional investigations (i.e. SPECT or MRI with contrast) should be performed to confirm or exclude the diagnosis. In latter phases of the disease, surgical decompression of the femoral head cannot lead to permanent amelioration, and it is inevitable to perform more invasive surgical procedures like "resurfacing" or bone grafting in younger patients, or the implantation of total hip endoprotheses.