The prognostic value of quantitative bone scan in knee osteochondritis dissecans. A preliminary experience

We reviewed the records of 12 patients ages 9 to 16 years with knee osteochondritis dissecans. All patients had clinical histories and examinations, four radiographic views of the knee, and technetium-99m diphosphonate quantitative bone scans. Scan results (symmetric, increased, or decreased activity), clinical course, healing time, and final outcome were correlated to determine the prognostic value of the scan. We divided the patients into those with open physes (distal femoral and proximal tibial) and those with closed physes. Four of the six patients with open physes had increased activity on the bone scan. All four of these knees healed with nonsurgical treatment. The other two patients had decreased activity on bone scan, and both required surgical treatment after nonsurgical treatment failed. Of the six patients with closed physes, all had increased activity on the bone scan, but only two patients had healing of the osteochondral lesion without surgery. Quantitative bone scanning had a 100% predictive value for the prognosis in osteochondritis dissecans patients with open physes, but for those with closed physes the predictive value was less. Because the natural history in the adolescent group is less predictable, it is in this group that the quantitative scan would be most helpful. In this small group of patients, quantitative bone scanning had limited prognostic value.