Early Femoral Insufficiency Fractures After Primary Total Knee Arthroplasty

Abstract

Background: Periprosthetic femur fracture following total knee arthroplasty (TKA) is a devastating complication. Although trauma-related periprosthetic femur fractures have been well studied, early atraumatic insufficiency periprosthetic fractures (IPFs) are gaining attention. We present the largest IPF series to date to better understand and prevent this complication.

Methods: A retrospective study of all patients who underwent a revision surgery for periprosthetic fracture within 6 months of primary TKA between 2007 and 2020 was performed. Patient demographics, preoperative radiographs, implant details, and fracture radiographs were reviewed. Alignment measurements and fracture characteristics were assessed.

Results: Sixteen patients met criteria (rate 0.05%), and 11 had posterior-stabilized TKAs. The mean age was 79 years, mean body mass index was 31 kg/m², and 94% (15/16) were female. Seven (47%) patients had a confirmed history of osteoporosis. IPF occurred on average 4 weeks (range, 4 days-13 weeks) after the index TKA. Overall, 12 of 16 (73%) had preoperative valgus deformities, and 11 patients (10 valgus, 1 varus) had preoperative deformities >10 degrees. A characteristic radiographic appearance of femoral condylar impaction and collapse was noted in 12 of 16 cases (75%); 11 of these 12 fractures (92%) involved the unloaded compartment based on preoperative varus/valgus deformity.

Conclusions: Patients who developed IPFs were most commonly elderly, obese women with osteoporosis and severe preoperative valgus deformities. The apparent mechanism of failure was overloading of previously unloaded osteopenic femoral condyle. In high-risk patients, the use of a cruciate-retaining femoral component or a femoral stem for a posterior-stabilized femur may be considered to help avoid this catastrophic complication.

Keywords: Fracture; Insufficiency; Total knee arthroplasty.

Figure 1

An 81-year-old female patient with severe preoperative valgus deformity seen on anteroposterior (AP) view (a) who received a bicruciate-stabilized primary total knee replacement as demonstrated on the AP view (b). The patient reported progressively worsening lower-extremity pain and decreased lower-extremity function at the 2-week postoperative visit and was found to have a varus deformity with collapse of the medial femoral condyle as demonstrated on the AP view (c). The fracture was treated with revision of the femoral component only as demonstrated on the AP view (d).

Figure 2

A 68-year-old female patient with severe preoperative valgus deformity demonstrated on the AP view (a). The patient received a posterior-stabilized primary total knee replacement demonstrated on the AP view (b). At 3 weeks postoperatively, the patient reported increasing knee pain and was found to have a vertical medial condylar fracture demonstrated on the AP view (c). The fracture was treated with a distal femoral replacement demonstrated on the AP view (d).

Figure 3

A patient with a preoperative varus deformity demonstrated on the AP view (a) subsequently experienced collapse of the lateral femoral condyle and failure into valgus as seen on the AP view (b) following primary total knee replacement. (c) Immediate postoperative AP view.