The Tibia Plafond Horizontal Orientation Angle for Frontal Alignment Evaluation of the Distal Lower Extremity.

PURPOSE OF THE STUDY Osteotomies around the knee are an established technique for treating knee osteoarthritis and other knee conditions by redistributing the body's weight and force within and around the knee joint. The aim of this study was to determine if the Tibia Plafond Horizontal Orientation Angle (TPHA) is a reliable measure for describing ankle alignment of the distal tibia in the coronal plane. MATERIALS AND METHODS This retrospective study included patients who underwent supracondylar rotational osteotomies for correction of femoral torsion. All patients had standing radiographs taken preoperatively and postoperatively with both knees pointed forward. Five variables, including Mechanical Lateral Distal Tibia Angle (mLDTA), Mechanical Malleolar Angle (mMA), Malleolar Horizontal Orientation Angle (MHA), Tibia Plafond Horizontal Orientation Angle (TPHA), and Tibio Talar Tilt Angle (TTTA), were collected. The preoperative and postoperative measurements were compared to each other using the Wilcoxon signed rank test. RESULTS A total of 146 patients were included in the study, with a mean age of 51.47 ± 11.87 years. There were 92 (63.0%) males and 54 (37.0%) females. MHA decreased from 14.0° ± 5.32° preoperatively to 10.59° ± 3.93° (p < 0.001) postoperatively, and TPHA decreased from 4.88° ± 4.07° preoperatively to 3.82 ± 3.10° (p = 0.013) postoperatively. The change in TPHA was significantly correlated with the change in MHA (r = 0.185, CI 0.023 - 0.337; p = 0.025). No differences were found between the measurements of mLDTA, mMA, and mMA pre- and postoperatively. DISCUSSION The orientation of the ankle should be taken into consideration during preoperative planning of osteotomies and should be measured in cases of postoperative ankle pain. CONCLUSIONS The TPHA is a reliable measure for describing ankle alignment of the distal tibia in the frontal plane. Key words: osteotomy, ankle, realignment, coronal alignment, preoperative planning.