Bone scanning in the assessment of patellar viability following knee replacement.

In an attempt to diagnose avascular necrosis (AVN) of the patella, a potential complication of the surgical procedure, 99mTc-MDP bone scanning was performed pre- and postoperation in 37 patients treated by 41 total knee arthroplasties. The normal immediate postoperative scan should demonstrate increased radionuclide uptake in the patella when compared to preoperative scans. Decreased uptake was seen in four cases in the early postoperative period. This latter group was believed to be at risk for osteonecrosis and stress fracture of the patella. For this reason, prophylactic restriction of activity was instituted, with subsequent return of normal radionuclide uptake in the patella. Bone scanning provides an effective method of early diagnosis of patients at risk for the development of AVN and secondary patellar fractures following total knee arthroplasty.

Duplex ultrasound imaging: vascular applications.

A recently developed duplex ultrasonic imaging system that combines high-resolution real-time imaging with simultaneous Doppler analysis provides accurate evaluation of hemodynamically significant occlusive vascular lesions. This system was used in the evaluation of the extracranial carotid arteries, iliofemoral arteries, and hemodialysis shunts. The system obtains information regarding blood velocity, lumen area, plaque composition and ulceration, and hemodynamic turbulence. A total of 140 patients with hemodynamically significant lesions diagnosed by this method was evaluated angiographically. Correlation between the two modalities yielded a sensitivity of 0.94, a specificity of 0.88, and an overall accuracy of 0.92. The diagnostic information obtained can be used to differentiate potential surgically correctable lesions from those that require medical therapy or follow-up.