Bone, 13, 161-165, (1992) Printed in the USA. All rights reserved. 8156-3282192 $5.00 + .OO Copyright 0 1992 Pergamon Press plc Bone Death in Transient Regional Osteoporosis C. R. DUNSTAN, R. A. EVANS and N. M. SOMERS Metabolic Unit, Concord Hospital, Sydney, Australia Address for correspondence and reprints: Dr. R. A. Evans, Metabolic Unit, Concord Hospital, NSW 2139, Australia. zyxwvutsrqponmlkjihgfedcbaZY Abstract A 4t3-year-old man developed transient regional osteoporosis, with hip and later knee pain. He responded welt to lumbar sympathectomy. The femur and tibia adjacent to the painful knee were osteoporotic, white the medial femoral condyle showed increased uptake in a bone scan. In the femoral condyle, bone histology showed areas of dead bone undergo- ing osteoclastic resorption, and increased bone formation. The tibial bone was hiitologically normal. The partial bone death in the distal femur suggests that the disorder may be related to both avascular necrosis of bone and reflex sympa- thetic dystrophy. Key Words: Bone-Osteonecrosis-Transient osteoporosis- Osteoclast4steoblasts-Osteocytes. Introduction Transient regional osteoporosis (TRO) is characterized by pain in one or more joints, lasting for several months and accompanied by radiographic osteoporosis of the bones adjacent to the affected joints (Lakhanpal et al. 1987). Radionuclide bone scans show increased isotope uptake by bone adjacent to the affected joints. The pathogenesis of TRO is unknown. A similar clinical, x-ray, and scan pattern is seen in avascular necrosis of bone (AVN), Type I (Ficat 1985), which may involve more than one area (Zizic et al. 1986). A final diagnosis of TRO might be thus made if the condition subsided spontaneously, or of AVN if it progressed to subchondral bone collapse. TRO is also considered by some to be a variant of reflex sympathetic dystrophy (RSD) (Rosen 1970; Resnick & Niwayama 1988), and the two disorders am similar in many respects. However, RSD is characterized by trophic changes in the superficial tissues, a lack of migration, frequent involvement of the upper extremities, and often permanent disability, features usually absent in TRO (La- khanpal et al. 1987). Histologic studies of bone in TRO have not been definitive. Doury et al. (1981) considered the histology to reflect best a “high remodelling” osteoporosis. Lakhanpal (19871, in biopsies from ten patients with TRO, noted thin trabeculae in eight, in- creased osteoblastic activity in four, and normal bone in two biopsies. Bloem (1988) noted increased bone turnover and ‘mild chronic inflammatory reaction” in a single patient with TRO. MR scanning suggests that the water content of the involved bone is increased (Wilson et al. 1988). We report here a patient suffering from TRO, comparing the appearances in calcified sections with those in sections processed to show bone viability. 161 Case Report A 48-year-old man noted the gradual onset of pain in his left hip in June 1988. No aetiological factors for bone necrosis were apparent. In particular, there had been no dysbarism, corticoste- roid administration, hip injury, pancreatitis, or gout, and the ethanol intake was 20 g/day. A month after the onset of hip pain, he noted on his right leg a lesion that was identified as a malig- nant melanoma. It was treated by excision, skin grafting and block dissection of the inguinal lymph glands, which were free of malignant cells. He had persisting mild fymphoedema of the right thigh and leg. The left hip pain became more severe. Radiographic appear- ances were normal, but a technetium pyrophosphate bone scan showed increased uptake in the left femoral head (Fig. 1). He was considered to have idiopathic osteoneccosis of the left fem- oral head, and, in September 1988, a core decompression of the femoral head (Ficat 1985; Camp & Colwell 1986; Zizic et al. 1986) was performed, the drill hole being partly filled with meth- yl methacrylate. Routine haematoxylin and eosin stained sec- tions of decalcified bone appeared normal. The hip pain gradu- ally improved following the procedure. In December 1988, he developed a constant pain in the left knee, aggravated by weight bearing or by flexion or extension of the knee. This pain became severe, and he was referred to the Metabolic Unit in March 1989. He was a robust man, showing signs of strain due to pro- tracted severe pain. There was increased temperature and ten- derness on the medial aspect of the left knee. Movements of the knee were inhibited by pain, and there was mild muscle wasting in the left thigh. Radiographically the left femoral head bone seemed normal (Fig. 2) but the bones adjacent to the left knee showed spotty osteoporosis (Fig. 3A). A radionuclide bone scan showed increased uptake on the medial side of the distal left femur (Fig. 3B), with normal uptake in the left femoral head. Chest X-ray, haemoglobin, white cell count, plasma creatinine, and electrolytes were normal. A diagnosis of TRO was made, and in April 1989 he under- went a left lumbar sympathetic block (L2-3), by infiltration of 8 ml 10% phenol in a radio-opaque medium (“Conray”), localis- ing the injection with an image intensifier. The left thigh and leg were then warmer than the right, indicating that the block was effective. The pain improved immediately following the sympathetic block, and he recommenced playing lawn bowls. Ten days later the pain recurred and he developed a small effusion in the left knee joint. Because of the possibility of metastatic melanoma, he underwent needle biopsy of the medial aspects of the left femur and tibia a little above and below the knee joint, six weeks after