Natural history of radiographic tracker pinhole recovery after robotic-assisted cementless total knee arthroplasty.

Robotic-assisted total knee arthroplasty (RATKA) requires tracker pin placement, creating cortical pinholes that may remain visible on postoperative radiographs. This study evaluated the radiographic natural history of tracker pinhole recovery after RATKA. This retrospective cohort study included 369 consecutive primary RATKAs performed using 4.0-mm bicortical array pins. Each patient had one radiograph within approximately 1 month, 3-4 months, 5-6 months, and 9-12 months; no routine radiographs were scheduled at 7-8 months. Recovery phenotypes were early recovery at 5-6 months (n = 224), delayed recovery first documented at 9-12 months (n = 74), and persistent visibility at the 9-12-month assessment (n = 70). One pinhole-related fracture was analyzed separately. Separate exploratory logistic-regression models compared delayed versus early recovery and persistent visibility versus early recovery, with Benjamini-Hochberg false-discovery-rate adjustment. No complete recovery was observed at 1 month or 3-4 months. Early recovery occurred in 224 knees (60.7%), delayed recovery in 74 (20.1%), persistent visibility at 9-12 months in 70 (19.0%), and an adverse pin-site fracture in one (0.3%). Overall, 298 knees (80.8%) demonstrated radiographic recovery by the late assessment. BMI differed across the three recovery groups (Kruskal-Wallis p = 0.002). In adjusted analysis, higher BMI was associated with delayed versus early recovery (adjusted OR 1.10 per kg/m², 95% CI 1.04-1.17; p = 0.002; false-discovery-rate q = 0.022), but not with persistent visibility. Diabetes and smoking were not associated with either trajectory. Two periprosthetic fractures occurred (0.5%), both requiring reoperation; only one involved the tracker pinhole region. No revision TKA, femoral radiolucency, or progressive radiolucency was recorded. Tracker pinholes after RATKA remodel progressively, with most recovery documented by 5-6 months and additional recovery at the 9-12-month assessment. Higher BMI was associated with delayed but eventual recovery in an exploratory adjusted model, while no association was observed with persistent visibility. Persistent visibility was not accompanied by progressive implant-interface radiolucency. A fracture directly involving a tracker pinhole was rare.