Sagittal Plane Alignment for First Metatarsal Phalangeal Arthrodesis Correlated with Postoperative Function: What is the Optimal Position?

There have been many reports describing the proposed alignment of a first metatarsal phalangeal arthrodesis to obtain optimum function. Most of these recommendations are based upon historical and anecdotal evidence. Furthermore, there are few reports directly comparing alignment to patient reported function. We studied radiographic sagittal plane alignment in a group of 60 patients (80 feet) who had undergone a first metatarsal phalangeal joint arthrodesis (20 of the 60 had bilateral arthrodesis) to better understand how this component of the arthrodesis position translates to real world function. The patients in this study had completed a functional survey in 2022 at a mean of 28.4 (median 27.8; range 13.2-45.7) months with very high satisfaction for return to activities of daily living and recreational sports. We measured the sagittal plane position of the first metatarsal relative to the proximal phalanx in this cohort with known post operative activity data. We found that a mean (standard of deviation) sagittal plane angle (angle between the anatomic axis of the first metatarsal and the proximal phalanx) of 15.4 (SD 7.4) degrees and a proximal phalanx head to ground height of 12.7 (SD 3.3) mm was present in this group. Comparing the functional and positional results we conclude that this sagittal plane position provides a good recommendation for alignment.