Outcomes Following Transtibial Amputation with and without a Tibiofibular Synostosis Procedure: A Multicenter Randomized Clinical Trial (TAOS Study)

Background: This study compared outcomes at 18 months between patients who underwent transtibial amputation with and without a tibiofibular synostosis procedure. We hypothesized that complication rates would be lower in patients who did not receive a synostosis procedure compared with those who did receive a synostosis procedure, but the synostosis group would report better function. Methods: This multicenter randomized clinical trial (RCT) included patients aged 18 to 60 years who were treated without (n = 52) or with synostosis (n = 54) during transtibial amputation. Patients who refused randomization were enrolled in an observational (OBS) study (n = 93; 31 synostosis, 62 non-synostosis). There were 2 primary outcomes: operative treatment for a complication within 18 months of amputation and Short Musculoskeletal Function Assessment (SMFA) scores. The primary analyses were based on the RCT participants, and the secondary analyses were based on the treatment received by the combined RCT + OBS participants. Results: In the primary RCT analysis, the probability of ≥1 operatively treated complication was higher for the synostosis group (42%; 95% confidence interval [CI]: 29.8% to 56.2%) than the non-synostosis group (24%; 95% CI: 14.2% to 37.9%), with an absolute risk difference of 18% (95% CI: 0.31% to 36%). There were no appreciable differences in mean SMFA scores. In the secondary combined analysis, the probability of an operatively treatment complication was larger in patients who did versus did not receive a synostosis procedure (absolute risk difference: 26.1%; 95% CI: 12.0% to 40.3%). Differences in SMFA scores favored synostosis, although there were no differences in pain, prosthetic use, and satisfaction. Conclusions: The results of the primary RCT analysis supported our hypothesis of fewer complications in patients who do not undergo a synostosis procedure compared with those who undergo a synostosis procedure, but we found insufficient evidence to conclude that those in the synostosis group have better function. The trial did not reach target enrollment. The secondary combined analysis supported the primary analysis in terms of complications. In the secondary analysis, while pain, prosthetic use, and satisfaction remained similar, the SMFA scores were better for the patients who received a synostosis procedure, although the differences are of uncertain clinical importance.