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Femoral valgus angle may better determine knee prosthesis positioning
Measurement of femoral valgus angle can reduce the outliers among patients undergoing elective TKA.
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Researchers found that a preoperative measurement of a patient’s femoral valgus angle could help them reduce the number of outliers of femoral component positioning in total knee arthroplasty and may improve how accurately a knee prosthesis is positioned.
Justinas Stucinskas, MD, and colleagues conducted a randomized control trial in which they included 100 consecutive patients with severe osteoarthritis (OA) who were admitted for unilateral elective total knee arthroplasty (TKA). They randomized the patients into two groups of 50 patients each.
“Measuring preoperative femoral valgus angle on X-rays for femoral cut reduces the number of outliers of femoral component positioning in TKA,” Stucinskas and colleagues wrote in their study.
Valgus angle and arthroplasty
According to details of the study that Stucinskas presented at the European Federation of National Associations of Orthopaedics and Traumatology Congress Annual Meeting, both groups underwent conventional TKA with the same type of implant, but in the control group the femoral valgus angle for intramedullary femoral guide was set at 7°.
Images: Stucinskas J
The other group of 50 patients — the measured group — had their femoral valgus angles measured preoperatively from a long hip-knee-ankle radiograph. Surgeons then set the intramedullary femoral guide angle for the femoral cut accordingly.
At 6-month follow-up, 88 patients were available for review. A blinded investigator took long-standing radiographs and noted the coronal alignment of the femoral and the tibial components, and mechanical axis (hip-knee-ankle) angle.
There were no significant differences between the 46 patients in the control group and the 42 patients in the measured group in terms of age, gender, body mass index, preoperative varus/valgus knee deformity and severity of knee OA.
In the measured group, investigators reported the preoperative average femoral valgus angle was 7° ± 1°, which varied from 5° to 10°.
The results showed that in the control group there was no statistically significantly different rate of outliers in terms of postoperative mechanical axis and tibial component alignment.
Possible to reduce outliers
Stucinskas and colleagues also found no significant differences in mean preoperative mechanical axis angles between the two groups. The control group mean mechanical axis angles were 173 °± 9° and the measured group mean mechanical axis angles were 172° ± 9°. Postoperatively, the angles in the control group as measured were 179° ± 3° compared to 178° ± 4° in the measured group.
The researchers noted they observed no significant differences in mean femoral and tibial component alignment because the mean femoral alignment in the control group was 89° ± 3° and in the measured group it was 89° ± 3°. Both groups demonstrated similar tibial component alignment, as well, which was 90° ± 2° and 89° ± 2°, respectively, in the control and measured groups.
There was a significantly higher number of outliers in terms of femoral component alignment in the control group; 12 patients (26%). In the group, 4 patients were outliers (10%), according to the study findings. – by Robert Linnehan
- Reference:
- Stucinskas J. Paper #3053. Presented at: 15th EFORT Congress — A combined programme in partnership with the BOA; 4-6 June 2014; London.
- For more information:
- Justinas Stucinskas, MD, can be reached at the Department of Orthopaedics, Lithuanian University of Health Sciences, Eiveniu 2 LT-50009, Kaunas, Lithuania; email: justinas.stucinskas@lsmuni.lt.
Disclosure: Stucinskas has no relevant financial disclosures.