Comparison of the thermal bone damage done by the oscillating saw and bone mill burr during total knee arthroplasty.

Background: Thermal osteonecrosis from bone cutting during total knee arthroplasty (TKA) may cause aseptic implant loosening. The study compares thermal bone injury from oscillating saw (CTKA) and bone milling burr treatments (RATKA). Method: A prospective study comparing thermal necrosis during CTKA and RATKA was performed. The sample size (n = 36) was determined with 18 patients per group, assuming a 15 % relative increase in thermal necrosis with RATKA, with statistical thresholds set at α = 5 % and β = 10 %. The upper tibia cut surface was analyzed, with histological sections examined from 20 randomly selected fields. Thermal necrosis was evaluated by determining the proportion of non-viable cells relative to viable ones and measuring the depth from the cut bone surface at which the first intact osteocyte was observed. Statistical analysis was conducted using appropriate comparative tests, including Chi-square and t-tests, with significance determined at a threshold of p < 0.05. Results: There was no significant variability in preoperative patient characteristics (gender, age, body mass index, diagnosis, range of motion, deformity and comorbidities) between CTKA (n = 18) and RATKA (n = 18) groups. The percentage of dead osteocytes at the resected surface in CTKA and RATKA were 40.3 % and 46.5 % respectively (p = 0.6309). The minimum depth where viable osteocytes were found was 25.5 ± 3.5 μmm and 27.1 ± 3.6 μmm in CTKA and RATKA respectively (p value = 0.091). Conclusion: Conventional TKA and RATKA produce similar thermal effects on bone, with no significant difference in osteocyte viability. This indicates that both surgical methods are comparable regarding thermal impact on bone health.