Objective To evaluate the effect of posteromedial tibial plateau osteophytes on intraoperative joint gap balance during robot-assisted total knee arthroplasty (TKA). Methods A retrospective analysis was performed on the clinical data of 82 patients with knee osteoarthritis who underwent robot-assisted TKA between November 2023 and December 2025. There were 13 males and 69 females, aged 55-83 years with a mean age of 69.1 years. Fourteen patients received left-sided surgery and 42 received right-sided surgery. The preoperative hip-knee-ankle angle was (6.8±1.4)°. After resecting anterior/lateral osteophytes intraoperatively, the robotic system was used to measure the medial/lateral joint gaps at full extension and 90° of knee flexion before osteotomy (planned state) and after osteotomy, which were recorded as medial extension gap (ME), lateral extension gap (LE), medial flexion gap (MF), and lateral flexion gap (LF). The differences (changes) between post-osteotomy gaps and planned gaps were calculated to assess osteotomy accuracy. Patients were stratified into four groups according to posteromedial tibial plateau osteophyte size measured on preoperative CT: no osteophyte, osteophyte size<5 mm, 5-10 mm, and >10 mm. Intergroup differences in the above gap changes were analyzed to evaluate the effect of osteophyte size on joint gap balance. Results In all 82 patients, joint gaps after osteotomy were significantly larger than the planned gaps (P<0.05). Only 13 patients (15.9%) showed no change in both medial and lateral extension gaps, and 25 patients (30.5%) had unchanged medial and lateral flexion gaps at 90° of knee flexion compared with the planned gaps. The size of posteromedial tibial plateau osteophytes ranged from 0 to 14.2 mm in the 82 patients, with a mean value of 5.62 mm. Among them, 15 patients had no osteophytes, 22 had osteophytes size <5 mm, 32 had osteophytes size of 5-10 mm, and 13 had osteophytes size >10 mm. The changes of ME, LE, MF, and LF increased progressively with the enlargement of osteophyte size, but the intergroup differences were not significant (P>0.05). There was no significant difference in the changes of ME, LE, MF, and LF among the three groups with osteophyte size ≤10 mm (P>0.05). Patients in the osteophyte size >10 mm group exhibited a significantly greater change in ME compared with all other gaps (P<0.05). Conclusion Osteotomy may alter the planned joint gap balance, and the degree of gap variation is correlated with the size of posteromedial tibial plateau osteophytes. For patients with osteophytes size >10 mm, the planned medial extension gap should decrease by 2 mm during preoperative osteotomy planning to obtain optimal intraoperative gap balance after bone resection.
