Risk of periprosthetic fracture after anterior femoral notching: a 9-year follow-up of 200 total knee arthroplasties

Background Notching of the anterior femoral cortex in distal femoral fractures following TKR has been observed clinically and studied biomechanically. It has been hypothesized that femoral notching weakens the cortex of the femur, which can predispose to femoral fractures in the early postoperative period. We examined the relationship between notching of the anterior femoral cortex during total knee replacement (TKR) and supracondylar fracture. Patients and methods Postoperative lateral radiographs of 200 TKRs were reviewed at an average of 9 (615) years postoperatively. 72 knees (41%) showed notching of the anterior femoral cortex. Notches were classified into 4 grades using the Tayside classification as follows. Grade I: violation of the outer table of the anterior femoral cortex; grade II: violation of the outer and the inner table of the anterior femoral cortex; grade III: violation up to 25% of the medullary canal (from the inner table to the center of the medullary canal); grade IV: violation up to 50% of the medullary canal (from the inner table to the center of the medullary canal) and unclassifiable. Results The interobserver variability of the classification system using Cohen's Kappa score was found to be substantially reliable. 3 of the 200 TKRs sustained later supracondylar fractures. One of these patients had grade II femoral notching and the other 2 showed no notching. The patient with femoral notching sustained a supracondylar fracture of the femur following a simple fall at home 9 years after TKR. Interpretation There is no relationship between minimal anterior femoral notching and supracondylar fracture of the femur in TKR.