Isolated Symmetrical Brachymetacarpia of the Thumb—Case Report

Abstract

The authors report a case of isolated symmetrical metacarpia of the first metacarpal in a 33-year-old serving soldier. The patient was totally unaware of the deformity, which was found incidentally while radiographs were done for the wrist to rule out scaphoid fracture. To the best of our knowledge, there have been no similar reports in the English literature before.

Introduction

Brachymetacarpia or short metacarpal may be part of a syndrome, acquired due to diseases in childhood or idiopathic. If the lesser metacarpals are short, the diagnosis is made early as there would be a gap in the metacarpal row with loss of grip strength. There are no genetic or biochemical anomalies in isolated brachymetacarpia [2]. We report a case of brachydactyly E as per the Bell classification, with isolated metacarpia of the first metacarpal.

Case Report

A 33-year-old soldier presented in the orthopedic clinic, with history of fall on the left outstretched hand. He had tenderness in the anatomical snuff box. His radiographs of the wrist did not show any fracture but a short first metacarpal. X-rays of the opposite hand also showed a similar anomaly. The phalanges of the thumb were normal. The other bones were normal. There was no history of similar anomaly in the family. There was no history of trauma or infection in childhood (Figs. 1 and 2).

Figure 1.

a and b Minimal hypoplasia of the thumb.

Figure 2.

AP radiograph of the hands showing brachymetacarpia of the thumb, with normal metacarpal arch.

His thumbs were found hypoplastic, with normal function. The range of movements of the thumb was normal. His foot, clinically and radiologically, was normal. The other hand bones were normal. Blood tests including the assessment for serum calcium, phosphorous alkaline phosphatase, and parathormone were normal. The patient was totally unaware of the deformity and is currently working in the Armed Forces.

Discussion

Brachymetacarpia is the shortening of the digit due to shortening of the metacarpal. Isolated brachymetacarpia is seen only occasionally. Childhood injury, osteomyelitis, and infections of the epiphysis can result in acquired brachymetacarpia, but these cases usually are unilateral [8]. Short metacarpals also have been observed as part of various syndromes [11] and as part of hyperphalangism (brachydactyly C) [1, 6]. Short first metacarpal has been described as part of hyperphalangism by Gunal et al. in their series of 42 cases of hyperphalanagism they observed “pear-shaped” short thumb metacarpal in 12 cases [6]. Almasi and Solgaard also reported a case of short thumb metacarpal in a child with hyperphalangism [1].

A widely used classification of brachydactyly is that of Julia Bell. She classified brachydactyly into five types, A to E, and brachydactyly A is further sub-classified into A1–A5 [3–5, 9] (Tables 1 and 2).

Table 1.

Bell classification.

Bell Type	Description
A	Middle phalanx of one, several, or all fingers and toes are short
	Further sub-classified into A1–A5 (see Table 2)
B	Distal phalanges and nails of the fingers and/or toes are small or absent. Middle phalanges may also be short
C	Short middle phalanges of the second and third fingers, sometimes with short first metacarpal. Hypersegmentation of the proximal phalanx of the index and middle fingers. The ring finger is the longest finger
D	Distal phalanges of the thumbs and/or big toe short and broad
E	Long, ring and little metacarpals and metatarsals are short. But any of them may be affected

Table 2.

Sub classification of Bell type A.

A Sub type	Description
A1	Broad hands, shortening of all digits. Middle phalanges and first phalanx are the most severely shortened. May be accompanied by symphalangism.
A2	Shortening confined to middle phalanx of the index finger
A3	Shortening confined to middle phalanx of the little finger
A4	Middle phalanges of index and little finger are short, with radial clinodactyly of the ring finger
A5	Absent middle phalanges

In brachydactyly E, the long, ring, and little metacarpals together or in isolation are short [2, 4, 7]. Idiopathic isolated bilaterally symmetrical brachymetacarpia of the first metacarpal has not been reported in the English literature before [9].

Brachymetacarpia may lead to functional and cosmetic complaints if the metacarpal arch is affected. In isolated brachymetacarpia of the lesser metacarpals, the diagnosis is made early in childhood as the deformity is made evident when the child makes a fist. When patients present late as adults treatment is usually not necessary.

Surgery is usually done for cosmetic reasons since the hand function is usually normal. Various procedures including osteotomy and intercalary bone grafting and callotasis has been advocated by some authors to increase the length of the metacarpal to improve cosmesis and function [2, 8]. Kato recommends callus lengthening when patients are 10 to 15 years of age [7].

In our case, since the patient already has been accustomed to the deformity and was totally unaware of this, no treatment was advised. Further to this, there was no functional deficit in our patient.