Tetracycline fluorescence for the peroperative localization of osteoid osteoma of the triquetrum.

Osteoid osteoma is infrequently encountered in the carpal bones. Its typical radiological features are not usually observed in this localization, which may result in delayed diagnosis. Since incomplete removal of the nidus may result in persistance or recurrence of the symptoms, other methods of locating the tumour during the resection should be used. We report a case of an osteoid osteoma of the triquetrum which, after incomplete initial resection and several revisions, developed instability of the carpus which required a limited intracarpal arthrodesis. A screw fragment left after implant extraction limited the imaging possibilities to study the persistent nidus. Intra-operative localization of the nidus with tetracycline dye and its visualization with ultraviolet light facilitated the complete removal.

A comparative study of the accuracy of Ranawat's and Pierchon's methods to determine the centre of rotation in bilateral coxopathy.

OBJECTIVE: The objective of the study was to compare two methods (Ranawat's and Pierchon's) used to determine the centre of rotation of the hip and establish which method calculates a position nearer to the real centre of rotation. PATIENTS AND DESIGN: We selected 24 patients with unilateral osteoarthritis of the hip. The centre of rotation of the healthy hip was determined in two consecutive radiographic studies by superimposing a template of circles and using two axes as the reference lines (X-axis=teardrop line; Y-axis=a line perpendicular to the X-axis, drawn from the intersection of the ilio-ischiatic line and the teardrop line). After ensuring the stability of these references, both methods were applied to the same radiograph to determine which one established a centre of rotation nearer to the anatomical centre identified by the template of circles. RESULTS: When the values for the healthy hip are compared with those obtained using Ranawat's method, highly significant differences are observed for both X (P<0.0001) and Y (P<0.0001). When the results for the healthy hip are compared with the values obtained using Pierchon's method, neither the X (P=0.722 ) nor the Y values (P=0.112) show any significant differences. It would be advisable to use Pierchon's method to determine the centre of rotation during the preoperative planning for a total hip arthroplasty when the anatomical alteration is bilateral.