Heterotopic Ossification at Tracker Pin Sites Following Robotic-Assisted Total Knee Arthroplasty.

CASE: A 72-year-old Caucasian man presented with left knee osteoarthritis and underwent Mako robotic-assisted total knee arthroplasty (TKA). Two months postoperatively, he complained of mild discomfort in his left quadriceps and limited flexion, with an active range of motion (ROM) from 0° to 60°. At 10 months, his ROM had not improved, and plain radiographs revealed a large, calcified mass in the distal femur, which appeared to be emanating from the tracker pin sites used during Mako robotic-assisted TKA, raising concern for heterotopic ossification (HO). He subsequently underwent excision of the HO and was started on indomethacin. CONCLUSION: Surgeons performing robotic-assisted TKAs should be aware of the potential for HO formation at tracker pin sites as a possible complication, particularly in patients presenting with postoperative stiffness.