Fracture of the Femoral Component in TKR – A Case Report

Femoral component fracture in total knee replacement (TKR) is a rare complication. In the majority of case reports, stress fractures of the femoral component have predominantly affected the medial condyle, following uncemented implantation of fixed-bearing knees. We report the case of fracture of the lateral condyle of a cemented fixed TKR due to bad cementing technique.


Introduction
The failure of total knee prosthetic components is a rare event and has been most commonly reported around the polyethylene insert of tibia or the tibial prosthesis. Issues with polyethylene fracture and subsequent base plate failure are already documented [1]. Femoral component fracture in total knee replacement (TKR) is a rare complication [2][3][4][5][6][7][8][9][10][11][12][13][14]. The 1990s saw an increased incidence of implant fractures with the three largest series reported with the uncemented Whiteside Ortholoc II knee replacements (Dow Corning Wright, Arlington, TN, USA) [12][13][14]. In the majority of case reports, stress fractures of the femoral component have predominantly affected the medial condyle, following uncemented implantation of fixed-bearing knees. In this case, failure of bone ingrowth in uncemented components, higher body mass index, and a higher athletic activity led to fatigue fracture of the femoral components [9]. We report the case of fracture of the lateral condyle of a cemented TKR.

Case Report
In 2000 TKR of the left knee was performed elsewhere in a 55-year-old male patient due to posttraumatic osteoarthritis using a PFC Sigma prosthesis (DePuy Orthopaedics, Warsaw, IN, USA). 10 years later revision arthroplasty was performed due to aseptic loosening of the tibial component ( Figure 1) using a PFC Sigma tibial prosthesis with a cemented intramedullary stem ( Figure 2). Postoperative follow-up was uneventful. In 2017 the obese patient (BMI: 40.3) suffered from acute knee pain again. X-ray of the left knee showed loosening of the tibial component ( Figure 3). Scintigraphy revealed enhancement in the region of the tibial and lateral femoral component ( Figure 4). Revision arthroplasty of the left knee was recommended. Three weeks later x-ray in respect to preoperative planning showed fracture of the femoral component ( Figure 5). Intraoperatively tibial and femoral component was found to be loose and the lateral condyle of the PFC Sigma prosthesis (DePuy Orthopaedics, Warsaw, IN, USA) was fractured (
Our patient had a normal anatomic static alignment of the total knee prosthesis but was extremely obese (BMI: 40.3) The patient suffered from acute knee pain, breakage of the femoral component was missed examining first x-rays. We follow Sarraf et al. who postulated that TKR is increasing more and more worldwide [10]. An increasing number of patients is obese at index operation. In that way component fracture is likely to become a more prevalent complication. Presently, it is a rare cause of knee pain after TKR; however, surgeons should remain vigilant and maintain a high index of suspicion with a patient who presents with acute onset pain, evidence of a varus deformity, and concomitant obesity, especially since component fractures can be easily missed on plain radiography [10]. To minimize risk of that rare complication we strongly recommend well performed modern cementing techniques and optimal leg axis in TKR [15].

Conflicts of Interest
None.

Funding
None.