Background: It has often been hospital policy to send all resected specimens obtained during a total hip or knee arthroplasty for histological evaluation. This practice is expensive and may be unnecessary. We sought to determine the ability of surgeons to diagnose primary joint conditions correctly, and we attempted to identify any possible risks to the patient resulting from the omission of routine histological evaluation of specimens at the surgeon's discretion. Our objective was to ascertain whether routine histological evaluation could be safely omitted from the protocol for primary hip and knee arthroplasty without compromising the care of the patient.Methods: A total of 1388 consecutive arthroplasties in 1136 patients were identified from a database of primary total hip and knee arthroplasties that was prospectively maintained by the senior one of us. Follow-up data obtained at a mean of 5.5 years (range, two to ten years) were available after 92 percent (1273) of the 1388 arthroplasties. The preoperative diagnosis was determined from the history, findings on clinical examination, and radiographs. The intraoperative diagnosis was determined by gross inspection of joint fluid, articular cartilage, synovial tissue, and the cut surfaces of resected specimens. The combination of the preoperative and intraoperative diagnoses was considered to be the surgeon's clinical diagnosis. All resected specimens were sent for routine histological evaluation, and a pathological diagnosis was made. Attention was given to whether a discrepancy between the surgeon's clinical diagnosis and the pathological diagnosis altered the management of the patient. The original diagnoses were updated with use of annual radiographs and clinical assessments. The cost of histological examination of specimens obtained at arthroplasty was determined by consultation with hospital administration, accounting, and pathology department personnel.Results: A pathological fracture or an impending fracture was diagnosed preoperatively and confirmed intraoperatively during twelve of the 1388 arthroplasties. Histological analysis demonstrated malignancy in specimens obtained during eleven of these arthroplasties and evidence of a benign rheumatoid geode in the specimen obtained during the twelfth arthroplasty. The preoperative and intraoperative diagnoses made before and during the remaining 1376 arthroplasties were benign conditions, which were confirmed histologically in all patients. No diagnosis changed during the follow-up period. As demonstrated by a comparison with the histological diagnosis, the surgeon's clinical diagnosis of malignancy had a sensitivity of 100 percent (95 percent confidence interval, 74.0 to 100 percent), a specificity of 99.9 percent (95 percent confidence interval, 99.6 to 100 percent), a positive predictive value of 91.7 percent (95 percent confidence interval, 64.6 to 98.5 percent), and a negative predictive value of 100 percent (95 percent confidence interval, 99.7 to 100 percent).There was a discrepancy between the preoperative and intraoperative diagnoses associated with eleven arthroplasties. All eleven intraoperative diagnoses were correct, as confirmed histologically. Excluding the patients who had a pathological or impending fracture, the accuracy of the surgeon's preoperative diagnosis was 99.2 percent (95 percent confidence interval, 98.6 to 99.5 percent). When the intraoperative and preoperative diagnoses were combined, the accuracy was 100 percent (95 percent confidence interval, 99.7 to 100 percent).Histological evaluation at our hospital resulted in total charges, including hospital costs and professional fees, of $196.27 and a mean total reimbursement of $102.59 per evaluation. In our series of 1136 patients with 1388 arthroplasties, these costs could have been eliminated for all but the twelve patients who had a suspected malignant lesion and the one patient in whom pigmented villonodular synovitis was found.Conclusions: Benign conditions can be diagnosed accurately by an experienced surgeon. The preoperative diagnosis should be determined on the basis of a carefully obtained history, a detailed physical examination, and a thorough evaluation of radiographs. To complete the clinical diagnosis, the preoperative information should be combined with findings obtained through careful intraoperative observation of resected specimens and, in the case of hip arthroplasty, inspection of the divided femoral head. In so doing, the surgeon can usually exclude clinically the possibility of malignancy or another condition that may alter the management of the patient and thus can reserve histological analysis for situations where the diagnosis is suspect or unexpected findings are noted intraoperatively. This selective, surgeon-directed use of histological analysis can result in notable financial savings.