Radionuclide joint imaging: an ancillary technique in the diagnosis of canine hip dysplasia.

Radionuclide joint imaging has been adapted for use in the diagnosis of canine hip dysplasia. Studies were done on 29 growing Labrador Retriever pups between 3 months and 1.5 years of age and on two adult dogs. Initally, pelvic radiographs and joint images were done on pups 12 to 16 weeks of age and were repeated at 2-week intervals thereafter. 99mTechnetium methylene diphosphonate (99mTcMDP), an osteotrphic agent, was the radiopharmaceutical used for all imaging studies. Inteference due to 99mTcMDP accumulation in the urinary bladder was avoided by static abdominal pressure. In 19 of the 21 dogs identified as abnormal by pelvic radiography, a similar diagnosis based on joint imaging was made for a true positive ratio of 0.90. Eight of ten dogs were identified as normal by means of both procedures, for a true negative ratio of 0.80. The overall accuracy was 0.87. Joint imaging was thus shown to be of similar value as pelvic radiography in the diagnosis of hip dysplasia. Joint images, however, displayed information on bone metabolic activity that could not be determined by pelvic radiography.