Abstract
Category:
Midfoot/Forefoot; Sports
Introduction/Purpose:
Os vesalianum is a very rare accessory foot bone located adjacent to the fifth metatarsal base. The estimated prevalence is below 1 %. In most cases it remains asymptomatic and is diagnosed as an incidental radiographic finding. Rarely the os vesalianum causes pain in the lateral midfoot. Therefore, only a few case reports about a symptomatic os vesalianum were published in the past. Here, we present what we believe to be the first small case series on that subject together with a review of the literature.
Methods:
Over a course of 10 years, we have treated three female patients (aged 18-36 years) who presented with pain on exercise in their lateral midfoot over the fifth metatarsal base. All of them had been diagnosed having a nonunion of the fifth metatarsal base, two after having sustained a direct or indirect trauma to the foot. The diagnosis of an accessory bone (os vesalianum) adjacent to the fifth metatarsal base fracture and with a joint facet to the cuboid bone could be made in retrospect in all cases by critically evaluating the initial radiographs. Technetium bone scans revealed an isolated increased uptake at the fifth metatarsal base. Upon surgical exploration, an irritation of the lateral facet of the cuboid with focal cartilage lesion through the accessory bone was noted in all 3 cases as a potential source of pain.
Results:
In all three cases, resection of the symptomatic os vesalianum and reinsertion of the peroneus brevis tendon into the fifth metatarsal base with a suture anchor was performed an led to a complete relief of pain within 3 months. At a minimum of 12 months follow-up all three patients fully returned to all previous activities including sports. The foot function index (FFI-D) improved from an average of 25.7 to an average of 3.67 at follow-up. One patient had a prominent subcutaneous suture knot removed, otherwise no complications were seen and no revision surgeries were needed in the further course. A systematic review of the literature revealed just 20 reported cases of a symptomatic os versalianum over 100 years (between 1922 and 2021). Previous treatment included observation, rest, resection with or without tendon reattachment, internal fixation and bone grafting.
Conclusion:
The knowledge of the location and morphology of accessory bones is indispensable when searching for rare causes of chronic foot pain. An os vesalianum may become symptomatic after direct and indirect trauma. The differential diagnosis must include an acute fifth metatarsal base fracture, non-union, or apophysitis (Iselin's disease), a distal peroneus brevis tendon lesion and lateral plantar fasciopathy. Resection of a symptomatic os vesalianum with reattachment of the peroneus brevis tendon to the 5th metatarsal base leads to a foot that is pain free and fully functional in most reported cases including the present series.
