Anterior cortical defects following infra-tubercle slope-reducing osteotomy show consistent remodelling without impairing union: A radiographic study with 12-month follow-up

Abstract

Purpose: To quantitatively evaluate anterior cortical defect remodelling and bone healing following infra-tubercle anterior closing-wedge high tibial osteotomy (ACW-ITO) and to identify clinical and surgical factors associated with remodelling. We hypothesised that substantial spontaneous remodelling would occur, that greater slope correction would result in larger initial defects with greater regrowth, and that patient-related factors would influence remodelling. Methods: A retrospective cohort of 100 consecutive patients undergoing infra-tubercle slope-reducing osteotomy was analysed. Standardised lateral radiographs were obtained preoperatively, immediately postoperatively, at regular intervals until consolidation, and at 12 months. Defect area (mm(2)) and step-off height (mm) were measured using calibrated digital imaging. Remodelling was expressed as percentage reduction from post-operative to final follow-up. Associations between remodelling and clinical variables were assessed using univariate and multivariable analyses. Results: Mean defect area decreased from 82.6 +/- 21.3 mm(2) postoperatively to 31.8 +/- 19.4 mm(2) at final follow-up, corresponding to 60.7% +/- 23.3% regrowth (p < 0.001). Step-off height decreased from 6.0 +/- 1.6 mm to 2.8 +/- 1.4 mm (51.7% +/- 23.9%; p < 0.001). Radiographic union was achieved in 98% of cases by 4 months and 100% by 6 months, with no cases of non-union or hinge fracture. Multivariable analysis identified age, body mass index (BMI), smoking status, and sex as independent predictors of remodelling, while slope correction was not independently associated. Conclusion: Anterior cortical defects following ACW-ITO undergo consistent and substantial remodelling within the first post-operative year. While greater slope correction produces larger initial defects, neither the magnitude of correction nor the initial defect size independently determines the extent of remodelling, partially refuting our pre-specified second hypothesis. These findings suggest that the immediate post-operative step-off undergoes substantial remodelling over time and should not be interpreted as a marker of impaired healing, even when considerable residual defect persists at 12 months.