Incidence and radio-uptake patterns of femoral head avascular osteonecrosis at 1 year after renal transplantation: a prospective study with planar bone scintigraphy.

OBJECTIVES

We prospectively investigated the incidence of femoral head avascular osteonecrosis (AVN) and radio-uptake patterns of femoral heads on bone scintigraphy at 1 year after renal transplantation.

METHODS

A total of 237 subjects (473 femoral heads) were included. A bone scintigraphy was performed at 12 +/- 1.1 months after renal transplantation, and 17 hips were painful at the time of bone scintigraphy. We graded the radioactivity in each femoral head as normal (grade 0), mildly increased (grade I), and definitely increased (grade II). Typical photon defects in the upper lateral femoral heads were evaluated separately. AVN was confirmed with clinical follow-up of more than 1 year and MRI and/or plain radiography findings.

RESULTS

Femoral head AVN was detected in 15 of the 237 patients and 23 of the 473 femoral heads. When grade I and II activities were used as positive criteria, bone scintigraphy had a sensitivity of 91.3% (100% with pain) and specificity of 74.0% (100% with pain) for AVN diagnosis. When only grade II activity was considered positive, the rates were 56.5% (80.0% with pain) and 99.5% (100% with pain), respectively. The presence of a typical photon defect had a low sensitivity of 47.8%, although the specificity was high (99.1%).

CONCLUSIONS

The incidence of femoral head AVN was low among a prospective cohort of renal transplantation recipients at the time of 1 year after engraftment. Planar bone scintigraphy is sufficient to diagnose AVN in symptomatic patients at risk for femoral head AVN using grade I and II activities as positive criteria.