Brachymetatarsia or hypoplastic metatarsal is a condition in which there is one or more abnormally short or overlapping toes metatarsals.This condition may result due to a congenital defect or it may be an acquired condition. It most frequently involves the fourth metatarsal. If it involves the first metatarsal, the condition is known as Morton’s syndrome.
Congenital causes include: Aarskog syndrome, Albright’s hereditary osteodystrophy, maternal ingestion of thalidomide during pregnancy and Apert syndrome. Can be caused by a trauma, although the exact mechanism is not known.
The forefoot deformity known as brachymetatasia is a malformation of any of the metatarsals. It most often effects the 4th toe and may be either uni or bilateral. The incidence of this rare deformity is reported between 0.02 to 0.05% and is up to twenty five times more prevalent in women compared to men. Although the main proportion of congenital brachymetatasia is idiopathic in nature it can also be associated with endocrinopathies, such as pseudo-hypoparathyroidism, as well as systemic syndromes such as Turner’s syndrome. The underlying cause of this shortened metatarsal is thought to be due to the premature closure of the metatarsal epiphyseal growth plate, however, the aetiology behind this is not fully understood. There are a number of other acquired causes for the development of shortened metatarsals. Principally trauma and infection, however tumours, radiation exposure and previous surgery are also associated. Morton’s foot, a short first metatarsal, is another less common form of brachymetatasia that becomes obvious by the age of 10 years old.
Patients with brachymetatasia may present in a number of ways. The short toe may sit dorsally which affects cosmesis and impairs load transference of the foot. This can lead to metatarsalgia and callosities particularly over the second and third metatarsal heads.With soft tissue imbalance, clawing of the toe may be problematic for shoe wearing.
The aim of surgery in these cases is to provide symptomatic relief and cosmesis. The two main methods of surgical correction are of distraction osteotomy providing a gradual increase in length, and the single stage osteotomy with bone graft to produce a rapid lengthening.
|Distraction osteogenesis with mini-external fixation||Application of mini-external fixator after a transverse osteotomy. Up to 12 days of gradual increasing of length||Longer lengthening possible||Significant scarring, skin tension from four fixator pin sites, patient co-operation, pin site infections, requires second procedure to remove distraction device||Takakura et al., 1997, (7 patients, Follow up 4.4 years) Magnan et al., 1995 (7 patients, mean follow up 6.5 years)|
|Single stage with allograft bone graft||Tendon Z-Plasty Transverse osteotomy with bone block between held in place by k-wire||Single main procedure, tendon z-plasty, smaller scar||K-wire requires removing, limited lengthening due to soft tissue tension, post-procedure reduction in lengthening, autologous donor site morbidity||Giannini et al., 2010 (29 patients, mean follow up 5 years)|
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