Early revision for isolated internal malrotation of the femoral component in total knee arthroplasty.

PURPOSE: In this prospective study, we determined whether corrective surgery for isolated rotational malalignment of femoral prosthesis components would benefit patients previously treated with total knee arthroplasty. The symptoms, amount of malrotation and type of constraint necessary for the revision prosthesis were investigated.

METHODS: Seventy-two patients were screened with computed tomography; of these, 14 had isolated internal malrotation of the femoral component with no other malpositions and were included in the study. A complete exchange arthroplasty with the correction of the malrotated femoral component was performed within 3 years of primary arthroplasty. Mean follow-up was 57 months.

RESULTS: At the time of revision, patients suffered either from instability in flexion with good range of motion (ROM) (flexion ≥ 90°) and pain on the lateral side of the distal femur and proximal tibia (n = 8) or from stiffness with pain on the medial side of the proximal tibial and poor ROM (flexion < 90°) (n = 6). One patient showed no patellar maltracking, six patients, patellar tilt and six patients, patellar subluxation. Median internal rotation of the femoral component was 7.1° (4.1-10.0°). A condylar-type revision implant with a posterior-stabilized insert was used in all patients. The corrective surgery resulted in an increase in the mean Knee Society Score from 52/65 to 85/84 points and an improvement in the mean Hospital for Special Surgery knee score from 63 to 83 points.

CONCLUSIONS: Correction of isolated internal malrotation of the femoral component ≥ 4° improves patient outcome.