Does a 1st metatarsophalangeal fusion in a patient with pes planus improve the pes planus deformity? A retrospective case series
J. Chapman, N. Dalal, H. Jenkinson, L. Mason
Introduction: Fusion of the 1st metatarsophalangeal joint (MTPJ) is the most common orthopaedic operation in the treatment of 1st MTPJ arthritis. In patients with concomitant pes planus deformity, what is unknown is if stabilising the distal aspect of the medial ray improves the pes planus deformity.
Primary objective: Our primary objective was the analyse the pes planus deformity pre and post 1st MTPJ fusion with the nul hypothesis that there was no difference.
Methods: We identified patients who underwent 1st MTPJ fusion using our electronic database from January 2011 to October 2021. Inclusion criteria were pre- and post-operative weightbearing plain radiographs, with a Meary’s angle of >4 degrees on pre-operative radiographs. Routine pes planus measurements were undertaken. Pre- and post-operative measurements were tested for significant change using Wilcoxon Signed Rank or Paired T-Tests. Data was analysed using IBM SPSS v.27.
Results: 26 feet were identified. The mean patient age was 62 years (range=38–76). There was no pre-operative correlation between Meary’s angle (MA) and the hallux valgus angle (HVA) (p=.923). A significant improvement between the pre- and post-operative measurements was identified in MA (mean reduction=3.69°; range: 13.47-0.05, p<.001), medial cuneiform height (mean increase=2.48mm; range: -8.26-3.7, p=.035), talo-navicular coverage angle (mean decrease=2.23°; range -6.94-13.14, p=.03), talar 1stmetatarsal angle (mean decrease=3.64°, range -5.71-20.12, p=.021) and intermetatarsal angle (mean decrease=4.17°, range -4.2-15.32, p<.001). As expected, the HVA was also significantly decreased post-operatively. Talo-navicular angle (p=.819), medial cuneiform 1st metatarsal angle (p=.594) and calcaneal pitch angle (p=.120) were not significantly changed. A post-operative MA of <4° was only achieved in 5/26 (19%) of cases.
Conclusions: Our results suggest that 1st MTPJ fusion improves axial alignment of the foot as well as reducing MA by a significant amount, although diagnostic criteria for pes planus remained in many cases.
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