Elective reconstruction in the valgus hindfoot is a complex and varied field of orthopaedic surgery. Often multiple procedures, both bony and soft tissue are required. The surgical aims are to create a plantigrade foot, restore hindfoot alignment and re-create the medial longitudinal arch in an attempt to allow more normal biomechanical function. Invariably a calcaneal osteotomy is required to correct hindfoot alignment. There are various methods of performing a calcaneal osteotomy [1] but no consensus as to which provides the best correction. Traditionally in our unit a medial displacement calcaneal osteotomy (MCDO) combined with lateral column lengthening (LCL) was used to do this. In this study we undertook radiological evaluation of the efficacy of a different type of osteotomy, the 'z-calcaneal osteotomy'.
Our aim was to assess the radiological improvement in various foot and ankle indices including talonavicular uncoverage, Meary's angle, incongruency angle and calcaneal pitch amongst others [2]. The study was performed retrospectively on 18 foot reconstructions in 14 patients where the z-calcaneal osteotomy was utilised. The surgeries were performed between 2012 and 2017 in Altnagelvin Hospital in Londonderry, Northern Ireland. A series of standardised weight bearing dorsoplantar (DP) and lateral radiographs and hindfoot alignment views were taken pre-operatively and post-operatively. Radiographic parameters were measured by two blinded investigators in both sets of radiographs to assess degree of correction after each reconstruction. The data was analysed using SPSS 22 for Windows and a paired student t-test used to compare the difference in means.
Dorsoplantar radiographic outcomes revealed a mean reduction of 15.7% in talonavicular uncoverage percentage (p = 0.001) and a mean reduction of 22.8 degrees in the incongruency angle (p = 0.01). The talonavicular uncoverage angle was improved by a mean of 16.1 degrees (p = 0.023). On the lateral radiographs the calcaneal pitch was increased by a mean of 6.5 degrees (p = 0.04) and Meary's angle was improved by a mean of 54.3 degrees. Hindfoot alignment was improved by a mean of 6.7 degrees (p = 0.03).
This study demonstrated significant improvements in the radiological indices measured when comparing pre-operative and post-operative radiographs in the cohort of foot reconstructions considered. As the z-calcaneal osteotomy was performed in conjunction with other bony and soft tissue procedures it is not possible to ascertain what degree of correction is attributable to the z-calcaneal osteotomy and what proportion is due to the other procedures.
The method we utilised for assessing hindfoot alignment was standard hindfoot alignment view (HAV) with angle measurement using standard Picture Archiving and Communication System (PACS) software. A long axial view may produce more reliable assessment of the hindfoot [3] and this is one of the limitations of this study. While the z-calcaneal osteotomy does appear to give good radiological correction of the valgus hindfoot, this was a small cohort of patients and the post-operative hindfoot imaging was not as complete as we would have liked. Further studies assessing both radiological improvement and clinical outcome are required to ascertain whether the z-osteotomy provides superior results than other established surgical techniques.