ANALYSIS AND PLANNING OF HINDFOOT DEFORMITY CORRECTION IN SAGITTAL PLANE

Abstract

Background. The disadvantage of the known methods of analysis and planning of hindfoot deformities in the sagittal plaBackground. Long bone deformity planning is well established. However, there are not well described methods of analysis and planning of hindfoot deformities in the sagittal plane. Such planning is made even more difficult with concomitant deformation of the midfoot and/or ankle contracture or malpositioned arthrodesis. The aim of our study was to develop a universal method of analysis and planning of the calcaneus correction, based on the normally derived reference lines and angles.Methods. We analyzed 65 standing lateral foot films in normal adults, 23-54 years old were analyzed. We drew the talus joint line (points “a” and “b” – Line 1). We drew a second line, (Line 2) the calcaneal line, which starts at the back of the calcaneal tuberosity (point “d”), drawn perpendicular to a line from top to bottom of the calcaneal tuberosity. The intersection of the calcaneal line and the talar joint line form point (c) anteriorly. We measured lines ab, ac and cd, and their ratios: ac/ab, and cd/ab.Results. Talar joint line (Line 1) and calcaneal line (Line 2) intersect at a point (c), forming an angle 15.2° (±3.4°). The ratio ac/ab = 2.56 (± 1.1). The ratio cd/ab = 4.59 (±1.0). These ratios are constants for calculating the idealized joint lines for deformity planning. For deformity cases, draw Line 1, the talar joint line ab. Extend that line anteriorly to (c), which is a distance ab×2.56 from point (a). From (c), draw an idealized calcaneal line, Line-2, at an angle 15° to Line 1. Place (d) on this line, at a distance ab×4.59 from point (c). Next, draw the deformed calcaneal line (Line 3) and point (d1 ) where it exits the calcaneal tuberosity. Use the same technique and landmarks as for drawing the normal calcaneal line. The intersection of Lines 2 and 3 is the apex of the deformity. Rotate the piece containing Line 3 around this apex, until it is collinear with Line 2, and (d) is coincident with (d1 ).Conclusions. We describe the normal sagittal plane relationships between the hindfoot (calcaneus – talus). This normative data is used for planning sagittal plane hindfoot deformity corrections. It can be used for hindfoot deformities analysis and correction planning. It is independent of ankle joint equinus or malpositioned ankle arthrodesis, which can be considered as separate deformities.