INTER AND INTRA-OBSERVER VARIATION OF CLASSIFICATION SYSTEMS FOR IMPENDING FRACTURES OF BONE METASTASES

Abstract

The study was designed to assess the reproducibility and reliability of Mirels scoring system and the conventional scoring system for impending pathological fractures. The results of both classification systems influence the choice of therapeutic procedures offered to these patients.

Blinded plain antero-posterior radiographs from forty-seven patients with bone metastases were scored by eight independent observers (four orthopaedic surgeons and four radiologists with varying clinical experience). Each observer scored the radiographs as per the Mirels and the conventional systems. After twelve weeks, the radiographs were scored again by the same observers. Inter– and intra-observer agreement was assessed based on the weighted kappa coefficient values for both systems.

For intra-observer reproducibility, kappa values for the conventional system had a mean of 0.495 (SD 0.12) showing a moderate agreement, while Mirels scoring system had a mean of 0.386 (SD 0.143) showing a fair agreement. For inter-observer reliability, kappa values for the conventional scoring system were 0.322 for the first test and 0.47 for the second test giving fair and moderate agreements respectively. For Mirels’ scoring system, kappa coefficient for inter-observer reliability was 0.183 for the first test and 0.218 for the second giving poor and fair agreements respectively.

The conventional scoring system showed a better inter and intra-observer agreement compared to Mirels’ scoring system. Consultants had a better intra-observer agreement compared to their registrars. We also found that radiologists, in our study, had better intra-observer agreement compared to orthopaedic surgeons. Radiographs should be scored cautiously by experienced doctors in a multi-disciplinary setting to achieve the best decision of whether to proceed with a prophylactic surgery or not.