Medial Tibial Plateau Stress Fracture Following Navigated Total Knee Arthroplasty: Two Case Reports

BACKGROUND Computer navigation in total knee arthroplasty has been gaining worldwide interest among orthopedic surgeons. While there is controversial data regarding its potential better clinical outcomes compared to conventional total knee arthroplasty, it has been shown to improve component and limb alignment reliability at a potential cost of increased complications. We present 2 case reports of medial tibial stress fracture through navigated tibial cutting block pinhole sites. CASE REPORT Both cases involved morbidly obese patients who underwent a navigated total knee arthroplasty. During surgery, there were no intraoperative concerns. Both knees were well aligned postoperatively and no unusual pain was reported. At 6 months after total knee arthroplasty, a periprosthetic fracture was initiated at a cutting block pinhole site with varus collapse of the tibial component. In both cases, the pinhole site was close to the medial tibial cortex and the primary tibial component collapsed into the varus, requiring revision to a stemmed component with allograft bone. For both patients, the revision arthroplasty continues to perform well. We believe cutting block design in combination with small tibias and elevated body mass index contributed to this complication. CONCLUSIONS Robotic-assisted total knee replacement has been shown to improve precision in component alignment. We caution against placing cutting block pinholes close to the medial tibial cortex, especially in morbidly obese patients with small tibias.