Quantitative assessment of joint space width with an electronic caliper.

UNLABELLED: The progression of joint space narrowing (JSN) is considered to be the best available marker of osteoarthritis (OA) progression. Several techniques have been proposed for the measurement of joint space at its narrowest point in OA of the hips and knees. OBJECTIVE: To evaluate the properties of the technique using an electronic caliper for the measurement of JSN in OA patients. DESIGN: We used an electronic caliper to measure joint space width (JSW) for hips on 100 plain radiographs. JSW was measured in the vertical position at the center of the femoral head. Femoral head diameter was also determined to correct for variations due to differences in magnification of digitized X-rays. All films were read twice by each of two rheumatologists (one junior, one senior) and two radiologists (one junior, one senior). Intraclass correlation coefficients and their 95% confidence intervals were calculated. RESULTS: Detailed results are given for right hips (38 with OA, 18 inflammatory, 44 normal); very similar results were obtained for left hips. For JSW, the intraclass correlation coefficient was between 0.96 and 0.99 for intraobserver reliability. The level of reliability was similar for analysis of the diameter of the femoral head (R:0.84 to 0.98) and for the ratio of these two measurements (0.96 to 0.99). The most reliable measurements were those made by the senior radiologist, followed by those made by the two rheumatologists. In assessments of interobserver reliability for the measurement of JSW, R varied from 0.91 to 0.96 for the first reading and from 0.88 to 0.96 for the second reading. For the measurement of femoral head diameter, R varied from 0.86 to 0.96 for the first reading and from 0.74 to 0.96 for the second reading. CONCLUSION: The electronic caliper technique is an accurate method for measuring JSW in the hip. This technique seems to be reproducible, is simple, and could be used for routine evaluation. Further validation is required, with the measurement of serial X-rays from the same patients.

Brown tumor of the spine revealing secondary hyperparathyroidism. Report of a case.

Brown tumors are classic skeletal manifestations of hyperparathyroidism usually seen in severe forms with subperiosteal bone resorption. They are exceedingly rare at the spine. We report the case of a woman on hemodialysis who developed two brown tumors, including one at the spine, as the first manifestations of secondary hyperparathyroidism. There were no neurologic manifestations. The clinical and radiologic abnormalities resolved after parathyroidectomy preceded by a bisphosphonate infusion to prevent possible spinal lysis progression during the immediate postoperative period. In addition to the location of one of the brown tumors at the spine, unusual features in this case were the explosive onset of hyperparathyroidism and the absence of detectable subperiosteal resorption. We also suggest that bisphosphonate therapy given before parathyroidectomy may be useful in patients with spinal brown tumors.