Zusammenfassung
Purpose Rotation of the lower limb in weight bearing long leg radiographs has a great impact on measured component and lower limb alignment parameters. We asked which rotational errors of long leg radiographs are present in a high volume centre and which radiological and clinical consequences arise regarding measured coronal component and lower limb alignment after total knee arthroplasty. ...
Zusammenfassung
Purpose Rotation of the lower limb in weight bearing long leg radiographs has a great impact on measured component and lower limb alignment parameters. We asked which rotational errors of long leg radiographs are present in a high volume centre and which radiological and clinical consequences arise regarding measured coronal component and lower limb alignment after total knee arthroplasty. Methods In 100 long leg radiographs coronal femoral and tibial component alignment and hip knee ankle angle (HKA) were measured. Present rotational errors in long leg radiographs were determined by fibular overlap and its impact on alignment parameters calculated. Results A mean internal rotation of 8.1A degrees (9.3 SD) with a range between 36A degrees of internal and 16A degrees of external rotation was found in long leg radiographs. This resulted in mean differences between measurements before and after rotational correction regarding femoral and tibial component alignment and HKA of 0.6-0.8A degrees (range 3.5A degrees valgus and 1.6A degrees varus error). Clinically, 11 out of 100 patients were wrongly assigned to either mal- or well-alignment (neutral mechanical alignment within +/- 3A degrees varus or valgus). Conclusions Surgeons should be aware of potential rotational errors in long leg radiographs after total knee arthroplasty resulting in wrong measurements. In case of rotational errors, radiographs should be repeated or rotational corrections calculated. For study purposes only radiographs after rotational correction should be accepted.
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