PURPOSE

The antegrade planning method according to Miniaci was primarily developed for high tibial osteotomies but is also used by several surgeons for planning of distal femoral osteotomies (DFO) in daily clinical practice. Strecker adapted in 2006 the Miniaci method as a retrograde method for planning of DFO. It is not yet known whether there is a difference between the planning methods for correction angles and osteotomy wedge heights in DFO planning.

MATERIALS AND METHODS

Three knee surgeons independently performed DFO planning with the antegrade Miniaci method, the retrograde method and the semiautomated method with the software mediCAD as a gold standard on 40 anonymized preoperative whole-leg X-rays of patients with a coronal deformity treated with DFO. Subsequently, the difference for correction angles and osteotomy wedge heights between the three methods was analyzed and the interobserver reliability was calculated.

RESULTS

The retrograde method resulted in significantly higher correction angles (+ 1.42° ± 0.55°; p < 0.001) and osteotomy wedge heights (+ 1,36 ± 0.61 mm; p < 0.001) than the antegrade Miniaci methods. A linear regression analysis showed a significant relationship between the extent of coronal deformity and the difference in correction angles between the two methods (p < 0.001, R = 0.74). The correction angles determined with the software-based method almost matched the values of the retrograde Miniaci method (mean difference: -0.06° ± 0.37°; p = 0.307). The interobserver reliability was almost perfect for all three techniques (ICC: antegrade: 0.85, retrograde: 0.92, software-based: 0.98).

CONCLUSION

Planning a DFO with the antegrade Miniaci method results in lower correction angles and osteotomy wedge heights than with the retrograde method, which in turn exhibits comparable values to software-based method as gold standard, leading to the risk of undercorrection with the antegrade method. In order to reduce the risk of undercorrection in DFO, the retrograde method appears to be superior.

LEVEL OF EVIDENCE

Level 3 - diagnostic retrospective cohort study.