Introduction: Standard arthrodesis of the first metatarsophalageal joint (MTPJ) is often carried out for degenerative disease in the presence of a hallux valgus without a first metatarsal corrective osteotomy. Despite this there is an improvement in the intermetatarsal angle (IMA) as well as the position of the tibial sesamoid. We attempt to quantify the amount of correction in this study.

Method: A cohort of 30 (35 feet) consecutive patients (10 males, 20 females) treated from May 2006 to May 2007 were reviewed. The mean age was 61.6 years (39 to 78 years). All patients underwent a standard primary fusion of the first MTPJ with a low profile plate and compression screw. There was no attempt to free the sesamoids, perform a lateral release or medial reefing of the medial capsule. We measured the hallux valgus angle (HVA), IMA as well as the position of the tibial sesamoid pre and postoperatively using a digital radiology imaging system.

Result: The mean improvement in IMA was 3.38° (p< 0.001) with a mean correction of 2.5° (p=0.02), 6.5° (p=0.02) and 5.8° (p=0.06) in the mild, moderate and severe groups respectively. A greater correction is expected with a more severe initial IMA (r=0.688). A similar trend is seen with the severity of the initial HVA (r=0.640). The tibial sesamoid position also tends to improve by one station (spearman correlation 0.861) post operatively.

Conclusion: There is an improvement in the IMA when the first MTPJ is fused. This improvement is proportional to the severity of the initial HVA and IMA. There is also an improvement in the resting position of the tibial sesamoid. We conclude that with a mobile first metatarsal medial cuneiform joint, the IMA corrects spontaneously when the first MTPJ is arthrodesed negating the need for a separate corrective osteotomy of the first metatarsal.