Computed tomography assessment of early bone healing after medial open-wedge high tibial osteotomy using unidirectional and spherical porous beta-tricalcium phosphate

Purpose To evaluate the effects of different artificial bone pore architectures on early bone union after medial open-wedge high tibial osteotomy (OWHTO). Methods This retrospective historical control study included 25 patients (30 knees) with varus knee osteoarthritis, who underwent OWHTO using beta-tricalcium phosphate (β-TCP) bone substitutes between January 2019 and August 2024. Patients were allocated to the spherical porous or unidirectional porous (UD) β-TCP groups, according to the pore architecture of the implanted bone substitute. As UD β-TCP was introduced at our institution in December 2022, group allocation was determined based on the surgical period. Radiographic correction loss was evaluated based on the medial proximal tibial angle and the percentage of the mechanical axis. Coronal and sagittal computed tomography (CT) scans were performed to assess bone healing, including bone union rates and CT attenuation values. Result Correction was not lost in either group. Coronal CT revealed significant bone resorption and formation in the UD group. Sagittal CT showed a significantly higher rate of bone union in the UD group than in the spherical porous group (47.2% ± 18.2% vs . 28.5% ± 21.7%; p = 0.008). The CT attenuation values were also significantly lower in the UD group (1312.6 ± 241.0 vs . 1512.4 ± 144.9 Hounsfield units; p = 0.025). Conclusions As assessed on CT, artificial bone with a UD structure was associated with earlier bone healing after OWHTO, without correction loss.