Use of bisphosphonate to manage avulsion fracture of tibial tuberosity with underlying angiomatosis: A case report

Journal of Orthopaedic Surgery, Jun 2003 by Wong, J W K, Yip, D K H, Kong, J K F, Chien, E P, Shek, T W H

ABSTRACT

An unusual case of avulsion fracture of the tibial tuberosity with underlying angiomatosis in a middle-aged man is described, with particular emphasis on the successful use of bisphosphonate in its treatment and the value of serial dual energy X-ray absorptiometry in its subsequent disease monitoring. This case illustrates the importance of careful correlation of the clinical, radiological, and histological findings in the management of skeletal tumour and tumour-like lesions. The differential diagnosis of osteolysis with vascular ectasia is discussed.

Key words: angiomatosis of bone; avulsion fracture; bisphosphonate; densitometry, X-ray; tibial tuberosity

CASE REPORT

A 53-year-old Chinese man had an avulsion fracture of the left tibial tuberosity that occurred while walking downstairs (Fig. 1). The fracture was initially treated with open reduction, bone grafting, and screw fixation. Bone biopsy results, performed at the same setting, were initially interpreted as being compatible with Paget's disease owing to the presence of irregular cement lines. The fracture site united after 3 months but the surrounding osteolysis did not resolve. The patient was therefore treated with a nasal preparation of calcitonin for 8 weeks. The disease progressed and the patient was referred to the Department of Orthopaedics & Traumatoloy, Queen Mary Hospital.

Investigations were performed to detect a possible bone tumour in the left proximal tibia. Plain X-rays showed areas of osteolysis at the proximal tibia, but did not have the characteristic features of Paget's disease, such as bowing or advancing radiolucent wedge (Fig. 2). Bone scanning showed a focal area of diffuse increased activity around the left tibial lesion, including the patella and femur. Serum alkaline phosphatase, calcium, and phosphate levels were normal. Lactate dehydrogenase levels were marginally raised. The 24-hour urine examination showed a marginally raised hydroxyproline level of 444 [mu]mol/dl (normal range, 120-320 [mu]mol/dl). A second biopsy showed the presence of irregular dilated vessels with an associated decrease in bone trabeculae. No osteoclastic activity or prominent cement lines were visible. The histological findings were thus not typical of Paget's disease and were more indicative of a vascular lesion (Fig. 3). In the light of the histological findings and the isolated bone involvement, the lesion was identified to be an unusual form of skeletal angiomatosis that involved one single osseous site, with associated osteolysis. Further progression of the osteolysis was evident during the observation period, and a course of palmidronate was used in an attempt to halt the disease process. The patient was given 60 mg intravenous infusion of palmidronate over one hour. he was also given supplement of calcium carbonate 1250 mg and calcitriol 0.5 [mu]g once daily for 6 months to maximise calcium absorption. The palmidronate infusion was repeated monthly for 6 months. Radiotherapy was not given. Progress was monitored by clinical symptoms and plain X-rays. Because of the possible risk of reavulsion of the tibial tubercule, the patient was allowed to walk only with toe touch down and assistance of crutches, during palmidronate treatment, and with a hinged knee brace.

As a time lag was expected for conventional X-rays to document new bone formation, bone densitometry (dual energy X-ray absorptiometry [DEXA]) technique was used to document the healing process and the bone mineral density changes during treatment with bisphosphonate (QDR 4500; Hologic Inc., Waltham, United States). The affected knee showed a definite increase in bone density after palmidronate treatment was commenced. The rate of increase of the bone density was uniform and peaked at the same time period for the different sampling areas. There was a subsequent decrease in the density, followed by another increase (Fig. 4). There were no such changes on the normal side, and there was no increase in bone density of the unaffected bone.

By one year after treatment, there was complete resolution of symptoms, return of full range of motion to the knee, and radiological consolidation of the tibia and static DEXA parameters for 6 months (Fig. 5). We thus recommended that the original screws be removed and a biopsy of the healed area be repeated. Histological investigation showed morphologically normal cortical and cancellous bone with no conspicuous osteoblastic or osteoclastic activity. The cement lines were not prominent and no vascular component was visible. The patient remained well and symptom-free at 3 years since treatment.

DISCUSSION

Spontaneous avulsion fracture of the tibial tuberosity in adults is uncommon and, in this case, occurred in bone with underlying angiomatosis. Making the diagnosis in this case was challenging. The initial histology was very limited and showed certain histological features of Paget's disease. However, the radiological features, biochemical findings, clinical presentation, and its subsequent clinical course were most unusual features of Paget's disease. Furthermore, Paget's disease is extremely rare among the Chinese population.1