Metatarsus primus adductus (MPA) is a foot deformity where the first metatarsal bone is adducted away from the second metatarsal creating a gap between the two. It is generally thought to have unknown aetiology, with the other four metatarsals maintaining a comparatively parallel orientation.
The adduction of the first metatarsal bone at the first metatarsocuneiform joint causes the proximal phalanx to move away from this alignment back towards the midline of the foot creating a Hallux abducto valgus (HAV) due to footwear pressure and ground reaction forces.

There is a misconception that a bunion is an enlargement of the bone, but this is not usually  the case, but caused by an inflamed bursal sac that can develop on the medial side of the joint due to footwear pressure.

In my experience MPA cannot be corrected conservatively, but can be stabilised and made more comfortable with the use of orthoses and foot wear changes. If surgery is required the proximal end of the MPA at the metatarsocuneiform joint is normally left intact with most surgeons preferring reconstructive osteotomy procedures at the distal margins around the first metatarsophalangeal joint (MTPJ).

My recommend treatment plan includes:

• Orthoses – dealing with any leg length inequality – because you will often find that the shorter limb will have an early heel lift creating increased abductory forces on the HAV, while the longer limb often has delayed heel lift increasing the time:pressure integral on the medial column, which again can put stress on the MTPJ.
• Footwear advice – running shoes being my personal go-to for my active clients.
• Stretching sagittal plane structures like the calves and hamstring – to reduce any sagittal plane blockages.
• Modifying activities: Avoid standing for long periods and other activities that cause HAV pain especially if Hallux limitus is also present.
• Medication: Anti-inflammatory medications, such as ibuprofen, can help reduce the pain and swelling.
• I can also often use Class 4 laser which seems to provide moderate pain relief.

1. Fraissler L, Konrads C, Hoberg M, Rudert M, Walcher M. Treatment of hallux valgus deformity. EFORT Open Rev. 2016;1(8):295-302. doi:10.1302/2058-5241.1.000005
2. Wu DY, Lam EKF. Can the Syndesmosis Procedure Prevent Metatarsus Primus Varus and Hallux Valgus Deformity Recurrence? A 5-Year Prospective Study. J Foot Ankle Surg. 2018;57(2):316-324. doi:10.1053/j.jfas.2017.10.012