66 Injury: the British Journal of Accident Surgery (1987) Vol. 18/No. 1

DISCUSSION Acknowledgement My thanks are due to Mr T. Dunningham, consultant orthopaedic surgeon, for permission to report this case.

Carpometacarpal dislocation other than of the thumb is

rare (Whitsun, 1955; Breiting, 1983). It is usually dorsal

(Hartwig, 1979). Only three cases of volar dislocation have been reported (Nalebuff, 1968; Gore, 1971; Schutt et al., 1981).

For multiple dislocations open reduction and Kir-

schner wire fixation are the recommended treatment of choice by most authors (Kleinman and Grantham, 1978; Hartwig, 1979; Breiting, 1983). For isolated volar dislocation of the carpometacarpal joint of the little finger, Nalebuff (1968) achieved reduction by closed manipulation. Kirschner wire fixation was necessary to prevent redisplacement.

REFERENCES Bora W. and Didizian N. H. (1974) The treatment of injuries

to the carpometacarpal joint of the little finger. J. Bone Joint Surg. 56A, 1459.

Breiting V. (1983) Simultaneous dislocation of the bases of the four ulnar metacarpals upon the last row of carpals. Hund 15(3), 287.

Bora and Didizian (1974) analysed 25 cases of the isolated carpometacarpal dislocation of the little finger. Their results show that complete reduction is necessary for full recovery of the gripping power. Kinnett and Lyden (1979) and Whitsun (1955) employed closed manipulation and plaster-of-Paris splintage for isolated carpometacarpal dorsal dislocations. Functional recov- ery was satisfactory despite persistent dorsal deformity.

Gore D. R. (1971) Carpometacarpal dislocation producing compression of the deep branch of the ulnar nerve. J. Bone Joint Surg. 53A, 1387.

Hartwig R. H. (1979) Multiple carpometacarpal dislocations. J. Bone Joint Surg. 61A. 906.

Kinnett J. G. and Lyden J. P. (197’)) Posterior fracture dislocation of the IV metacarpal hamate articulation. J. Trauma 19(4), 290.

Gore (1971) reported a delay of 5 weeks in the diagnosis of volar dislocation of the carpometacarpal joint of the little and ring fingers. This is the only case report in the literature of palsy of the deep branch of the ulnar nerve. Complete recovery followed open reduction of the dislocation and decompression of the nerve. In Bora’s series, those who were operated on had a delay in diagnosis of 3 days.

Kleinman W. B. and Grantham S. A. (1978) Multiple volar carpometacarpal joint dislocation. J. Hand Surg. 3(4). 377.

Nalebuff E. A. (1968) Isolated anterior carpometacarpal dislocation of the fifth finger. J. Truumu 8(6), 11 IS).

Schutt R. C., Boswick J. A. and Scott F. A. (1981) Volar fracture-dislocation of the carpometacarpal joint of the index finger treated by delayed open reduction. J. Truutnu 21( 11). 986.

Whitsun R. 0. (1955) Carpometacarpal dislocation. Clin. Orthop. 6. 189.

Palsy of the deep branch of the ulnar nerve following dorsal dislocation of the carpometacarpal joint of the ulnar two fingers has not been previously reported. In the case presented here, full recovery was achieved following closed reduction 9 days after the accident. Paper accepted 7 May 1986.

Reque.srs fbr rqwiw.s shoctkl he trdtlrewrl m: Thomas B. Young. Department ol’ Accident and Emergency. York District Hospital, Wigginton

Road. York YO3 7HE.

Ulnar nerve compression by an accessory abductor digiti minimi muscle presenting following injury

M. R. James, D. I. Rowley and S. H. Norris

Department of Orthopaedics, Northern General Hospital, Sheffield

INTRODUCTION THERE are many causes of ulnar nerve compression at the wrist; one of the less common causes is pressure by an anomalous muscle belly (SAgeback, 1977). Two

cases of nerve compression caused by an accessory abductor digiti minimi are described.

CASE REPORTS Case 1 A 37-year-old right-handed housewife hit her right hand on a wall 3 days before coming to hospital. She complained of pain on the ulnar side of the hand with loss of sensation in the distribution of the ulnar nerve. A diagnosis was made of acute entrapment of the ulnar nerve at the wrist, possibly associated

with injury to the ulnar artery. At operation an abnormal muscle was found overlying the ulnar nerve and artery. This took its origin from the deep fascia of the forearm, well over to the radial side, and after running obliquely over the ulnar nerve and artery, it joined the hypothenar muscles (Fig. 1). The nerve and artery were traced proximal and distal to the muscle and no arterial damage or other abnormality was found. The muscle was therefore excised. There was a full motor and sensory recovery in 6 months.

Case 2 A 50-year-old right-handed hospital porter complained of pain and numbness in the distribution of the left ulnar nerve, with some radiation of the pain towards the elbow. He had

Case reports 67

recently sustained a chip fracture of the base of the fifth (Turner and Caird, 1977). One of the two cases reported metacarpal. On examination, he had sensory changes in the here was a manual worker and both associated the onset distribution of the ulnar nerve in the hand and early clawing of the ring and little fingers. Nerve conduction studies sug-

of symptoms with minor injury, although it is open to

gested a defect in the ulnar nerve below the elbow, probably question whether or not this was a precipitating factor.

at the level of the wrist. An operation was performed to Minor injury could cause compression by causing

decompress the ulnar nerve at the wrist. The findings were swelling in the canal of Guyon, or thrombosis of the

the same as in Case 1. One year after operation he had full ulnar artery (Zweig et al., 1969). Neither of these cases sensory recovery, incomplete motor recovery and normal showed any signs of ulnar artery thrombosis, and exci- nerve conduction studies. sion of the muscle resulted in resolution of the symp-

toms.

DISCUSSKIN Accessory muscles running from the distal part of the forearm into the hypothenar eminence are well REFERENCES documented (Turner and Caird, 1977) and are all sup- Jeffery A. K. (1971) Compression of the deep palmar branch plied by the ulnar nerve. The most common variant is an of the ulnar nerve by an anomalous muscle. .I. Bone Joint accessory abductor digiti minimi (Smith, 1895). This h-g. 53B, 718.

may arise from the deep fascia of the forearm, the Wgeback S. (1977) Ulnar tunnel syndrome caused by ano-

anterior carpal ligament, the tendon of palmaris longus malous muscles. &and. J. Plast. Reconstr. Surg. 11, 255.

or of flexor carpi ulnaris and it runs into the hypothenar Smith G. E. (1985) An account of some rare nerve and

eminence, passing over the anterior carpal ligament muscle anomalies with remarks on their significance. J.

and the ulnar neurovascular bundle. Anat. 29, 84.

Accessory hypothenar muscles occur in approxi- Turner M. S. and Caird D. M. (1977) Anomalous muscles

mately 3 per cent of the population (Jeffery, 1971), but and ulnar nerve compression at the wrist. Hand 9(2), 140.

Zweig J., Lie K. K., Posch J. L. et al. (1969) Thrombosis of only rarely do they result in compression of the ulnar the ulnar artery following blunt trauma to the hand. J. nerve, so there must be a precipitating cause for the Bone Joint Surg. 51A, 1191.

entrapment. The most common reported cause is hyper- trophy of the muscles in the confined space, causing compression of the nerve, especially in manual workers Paper accepted 19 February 1986.

Requests for reprints should be addressed to: Dr M. R. James, Department of Orthopaedics, Northern General Hospital, Sheffield SS 7AU.

Ulnar Radial side side

b Fig. 1. Voiar aspect of right wrist of patient at operation. 1, Ulnar nerve. 2, Accessory abductor digiti minimi,