Application of axial load-share ratio testing technology in the bone transport treatment of large segmental tibial...

Bone transport is a widely established method for treating tibial bone defects. However, safely removing the external fixator as early as possible to shorten treatment duration remains a clinical challenge. This study aimed to investigate whether axial load-share ratio (ALSR) testing can safely and effectively assess callus healing strength at the mineralization zone and docking site, and thereby guide the precise timing of external fixator removal during tibial bone transport.

This retrospective study included 42 adult patients with tibial bone defects treated by bone transport between 2019 and 2025. Patients were divided into the ALSR group (n = 20) and conventional group (n = 22) according to the external fixation removal strategy used. In the ALSR group, ALSR testing was performed to evaluate healing strength at the mineralization zone and docking site. In the ALSR group, staged removal of external fixation was considered when ALSR testing showed a value < 5%, in combination with clinical examination and radiographic evidence. In the conventional group, we based removal decisions on standard clinical and radiographic criteria. We compared the following clinical indicators between groups: operative time, intraoperative blood loss, bone transport duration, healing time of the mineralization zone, healing time of the docking site, external fixation duration, and external fixation index. At the final follow-up, we used the Association for the Study and Application of the Method of Ilizarov (ASAMI) scoring system to assess bone healing and functional recovery and performed relevant statistical analyses.

The median bone transport duration was 82.50 (IQR,63.5-109.5) days in the ALSR group and 71.50 (IQR,64.00- 120) days in the conventional group(P > 0.05). The median healing time of the mineralization zone was 182.00 days (IQR,155.25-219.75) in the ALSR group, significantly shorter than 205.50 days (IQR,177.25-285.75) in the conventional group (P < 0.05). The median healing time of the docking site was 207.50 days (IQR,189.00-262.50) in the ALSR group, significantly shorter than 259.50 days (IQR,222.5-332.50) in the conventional group(P < 0.05). The median external fixation duration, which was defined as the primary endpoint, was 219.00 days (IQR, 205.50-277.25) in the ALSR group, significantly shorter than 274.00 days (IQR, 238.25-347.00) in the conventional group (P < 0.05). The external fixation index was 33.25 ± 4.97 d/cm in the ALSR group, significantly lower than 40.05 ± 9.39 d/cm in the conventional group (P < 0.05). At the final follow-up, there was no statistically significant difference in ASAMI scores and complications between the two groups (P > 0.05).

Following bone transport surgery for large segmental tibial bone defects, ALSR testing provides a quantitative and reliable method for evaluating callus strength during bone transport. It enables earlier and safer removal of external fixation, reducing treatment duration without compromising clinical outcomes.