Biomechanical and clinical analysis of pelvic stability and the role of internal fixation after debridement for sacroiliac joint tuberculosis with different degrees of bone destruction.

OBJECTIVE: To investigate the biomechanical characteristics and clinical outcomes after lesion debridement at varying degrees of sacroiliac joint destruction, and to assess the role of internal fixation in postoperative stability.

MATERIALS AND METHODS: Finite element analysis: An intact three-dimensional finite element model of the pelvis was established based on CT data from a healthy adult. On this basis, unilateral sacroiliac joint articular surface destruction of 25%, 50%, 75%, and 100% was simulated. For each destruction level, two postoperative models were constructed: debridement alone and debridement combined with internal fixation. Under physiological standing load conditions, pelvic global displacement, relative displacement of the sacroiliac joint surface, and displacement and stress distributions of the sacrum and ilium were comparatively analyzed among different models. Clinical analysis: A retrospective analysis was performed on 20 patients with sacroiliac joint tuberculosis who underwent lesion debridement at our institution between January 2010 and December 2025. Based on preoperative imaging, all patients had mild sacroiliac joint destruction (<1/3 involvement). The patients were divided into a debridement-alone group (n = 10) and debridement combined with internal fixation group (n = 10). Perioperative variables, including operative time, blood loss, and inflammatory markers, were systematically compared between the two groups. Clinical efficacy was evaluated by dynamically assessing changes in visual analogue scale (VAS) pain scores and Majeed functional scores.

RESULTS: Finite element analysis demonstrated that, in the debridement-alone model, overall pelvic displacement, relative displacement across the sacroiliac joint, as well as local bone displacement and stress values increased progressively with the severity of sacroiliac joint destruction. Under mild destruction, changes in these biomechanical parameters were minimal and showed no significant differences compared with the intact model (P > 0.05). However, under moderate-to-severe destruction, all parameters increased significantly (P < 0.05), indicating a marked reduction in both global and local pelvic stability. Following the addition of internal fixation, overall pelvic displacement, local stress, and relative joint displacement were all significantly reduced under moderate-to-severe destruction conditions. Clinical results showed that, in patients with mild bone destruction, there were no significant differences between the debridement-alone group and the debridement combined with internal fixation group in terms of pain relief, functional recovery, or radiographic improvement during follow-up (P > 0.05). Both groups achieved satisfactory clinical outcomes, with no evident recurrence or complications.

CONCLUSION: This study provides an initial biomechanical arithmetic modeling framework and compares its outputs with relevant clinical findings. The degree of sacroiliac joint destruction is closely associated with postoperative pelvic stability. In cases of mild destruction, debridement alone yields satisfactory outcomes, with no additional benefit observed from adjunctive internal fixation. As the severity of destruction increases, pelvic stability progressively declines, and the stabilizing effect of internal fixation becomes increasingly evident.