J. Anat. (1992) 180, pp. 189-190, with 2 figures Printed in Great Britain
Short Report A
variant of flexor
carpi
ulnaris causing ulnar
nerve
compression M. M. AL-QATTAN AND F. DUERKSEN Section of Orthopaedic Surgery, Health Sciences Centre, General Hospital, Winnipeg, Manitoba, Canada
(Accepted 9 August 1991)
ABSTRACT
Anatomical variations of the muscles and nerves around the wrist are common. Knowledge of such variations is derived from 2 sources: anatomical dissections and clinically reported cases. We present a case of duplication of the tendon of flexor carpi ulnaris with splitting of the ulnar nerve. The ulnar slip of the tendon was inserted into the pisiform bone and the radial slip into the proximal phalanx of the ring finger. The anatomical literature and the clinically reported cases of variations of the flexor carpi ulnaris are reviewed.
Anatomical variations of the muscles and nerves around the wrist are common. We present a previously unreported variation of the flexor carpi ulnaris causing ulnar nerve compression at the wrist. CASE REPORT
A 38-year-old right-handed male carpenter fell onto the back of his left hand and sustained a left Smith's fracture and a fracture of the ulnar styloid process. He was treated by closed reduction and immobilisation for 6 weeks. Four months later he presented with ulnar wrist pain on lifting, numbness in the small and ring fingers, and weakness of the grip. Examination revealed wasting of the first dorsal interosseous muscle and weakness of abductor digiti minimi. All other intrinsic hand muscles were normal and Froment's sign was negative. Flexor carpi ulnaris and flexor digitorum profundus were normal, although mild pain was elicited when flexor carpi ulnaris was tested. There was decreased sensation for light touch in the palmar distribution of the ulnar nerve. X-rays revealed union of the radius fracture but nonunion of the fracture of the ulnar styloid. Surgical exploration (Figs 1, 2) showed a duplicated flexor carpi ulnaris tendon with splitting of the ulnar nerve proximal to the pisiform bone. The ulnar slip of the tendon inserted into the pisiform. The smaller radial slip passed lateral to the pisiform. Exploration of the insertion of the radial slip was not undertaken, but pulling on the tendon produced flexion of the metacarpophalangeal joint of the ring finger.
Splitting of the ulnar nerve was observed 5 cm proximal to the pisiform bone. The smaller ulnar division of the nerve looped around the radial slip of the tendon of flexor carpi ulnaris to rejoin the ulnar nerve just proximal to the pisiform. More distally the ulnar nerve was found to divide normally into superficial and deep divisions in Guyon's canal. The radial slip of the tendon was excised and epineurolysis of the ulnar nerve performed. Postoperatively there was gradual but complete relief of the patient's symptoms and he resumed working normally 2 months later.
DISCUSSION
The flexor carpi ulnaris muscle arises from the medial epicondyle and receives a further contribution from a wide aponeurosis which forms a bridge between the medial border of the olecranon and the upper threefourths of the subcutaneous border of the ulna. Normally, both humeral and ulnar heads unite in a single muscle belly with a single tendon of insertion into the pisiform. The pisiform is morphologically a sesamoid bone in the tendon; by way of the pisohamate and pisometacarpal ligaments the muscle establishes more distal insertion. Anatomical variations of the flexor carpi ulnaris that have been reported previously are (1) extratendinous bands or extensions from the tendon of flexor carpi ulnaris to the fourth or more commonly the fifth metacarpal bone; (2) duplication of the flexor
Correspondence to Dr M. M. Al-Qattan, Section of Orthopaedic Surgery, GF307, General Hospital, 820 Sherbrook Street, Winnipeg, Manitoba, Canada, R3A 1R9.
M. M. Al-Qattan and F. Duerksen
190
Distal ^
A
Ulnar nerve
F I
Ulnar a rte ry
~
A-
4't
,
i
liiL I ,r:.%
0711,
* _
5
Flexor
N..
1%S' Ulnar nerve
ca
rpi
ulnaris
-ex ,
M.
Proximal
Fig. 1. The duplicated tendon of flexor carpi ulnaris with splitting of the ulnar nerve is shown. Note the smaller ulnar division of the ulnar nerve looping around (*) the radial slip of the flexor carpi ulnaris tendon.
carpi ulnaris tendon with insertion of the extra tendon onto the metacarpophalangeal joint of the little finger; (3) a fibrous or muscular extension from the tendon of the flexor carpi ulnaris to the carpal ligaments; and (4) duplication of the flexor carpi ulnaris muscle from the medial epicondyle to the pisiform. The above 4 anatomical variations were described by Testut & Latarjet (1928). Elliott Smith (1895) described a fifth anatomical variation, with the flexor carpi ulnaris muscle giving origin to an accessory abductor digiti' minimi muscle in the distal forearm to run a course superficial to the abductor digiti minimi with fused insertions. Clinically, the reported anatomical variations of flexor carpi ulnaris causing ulnar nerve compression include (1) fibrous bands from the belly of flexor carpi ulnaris and the ulnar artery (Holtzman et al. 1984); (2) the tendon of flexor carpi ulnaris at the pisiform giving origin to an anomalous muscle that passes between the motor and sensory branches of the ulnar nerve to be inserted into the carpal ligaments (Turner & Caird, 1977); (3) hypertrophy of flexor carpi ulnaris in the distal forearm (Harrelscn & Newman, 1975); and (4) splitting of the insertion of flexor carpi ulnaris with splitting of the ulnar nerve proximal to the pisiform (O'Hara & Stone, 1988; Zook et al. 1988).
Fig. 2. Diagrammatic representation of the anomaly. The insertion of the radial slip of the flexor carpi ulnaris (FCU) tendon was not surgically explored, but pulling on the slip produced flexion of the metacarpophalangeal joint of the ring finger.
In our patient, the duplicated flexor carpi ulnaris tendon is similar to the second anatomical variation reported by Testut & Latarjet (1928), except that the insertion of the extra tendon is to the ring instead of the little finger. REFERENCES
ELLIOTr SMITH G (1895) An account of some rare nerve and muscle anomalies with remarks on their significance. Journal of Anatomy and Physiology 29, 84-97. HARRELSON JM, NEWMAN M (1975) Hypertrophy of the flexor carpi ulnaris as a cause of ulnar nerve compression in the distal part of the forearm. Case report. Journal of Bone and Joint Surgery 57A, 554-555. HOLTZMAN RNN, MARK MH, PATEL MR, WIENER LM (1984) Ulnar nerve entrapment neuropathy in the forearm. Journal of Hand Surgery 9A, 576-578. O'HARA JJ, STONE JH (1988) Ulnar neuropathy at the wrist associated with aberrant flexor carpi ulnaris insertion. Journal of Hand Surgery 13A, 382-384. TEsTuJr L, LATARJET A (1928). Traite d'Anatomie Humaine, 8th edn, p. 1043. Paris: Gaston Doin. TURNER MS, CAIRD DM (1977) Anomalous muscles and ulnar nerve compression at the wrist. The Hand 9, 140-142. ZOOK EG, KUCAN JO, Guy RJ (1988) Palmar wrist pain caused by ulnar nerve entrapment in the flexor carpi ulnaris tendon. Journal of Hand Surgery 13A, 732-735.
Short Report A
variant of flexor
carpi
ulnaris causing ulnar
nerve
compression M. M. AL-QATTAN AND F. DUERKSEN Section of Orthopaedic Surgery, Health Sciences Centre, General Hospital, Winnipeg, Manitoba, Canada
(Accepted 9 August 1991)
ABSTRACT
Anatomical variations of the muscles and nerves around the wrist are common. Knowledge of such variations is derived from 2 sources: anatomical dissections and clinically reported cases. We present a case of duplication of the tendon of flexor carpi ulnaris with splitting of the ulnar nerve. The ulnar slip of the tendon was inserted into the pisiform bone and the radial slip into the proximal phalanx of the ring finger. The anatomical literature and the clinically reported cases of variations of the flexor carpi ulnaris are reviewed.
Anatomical variations of the muscles and nerves around the wrist are common. We present a previously unreported variation of the flexor carpi ulnaris causing ulnar nerve compression at the wrist. CASE REPORT
A 38-year-old right-handed male carpenter fell onto the back of his left hand and sustained a left Smith's fracture and a fracture of the ulnar styloid process. He was treated by closed reduction and immobilisation for 6 weeks. Four months later he presented with ulnar wrist pain on lifting, numbness in the small and ring fingers, and weakness of the grip. Examination revealed wasting of the first dorsal interosseous muscle and weakness of abductor digiti minimi. All other intrinsic hand muscles were normal and Froment's sign was negative. Flexor carpi ulnaris and flexor digitorum profundus were normal, although mild pain was elicited when flexor carpi ulnaris was tested. There was decreased sensation for light touch in the palmar distribution of the ulnar nerve. X-rays revealed union of the radius fracture but nonunion of the fracture of the ulnar styloid. Surgical exploration (Figs 1, 2) showed a duplicated flexor carpi ulnaris tendon with splitting of the ulnar nerve proximal to the pisiform bone. The ulnar slip of the tendon inserted into the pisiform. The smaller radial slip passed lateral to the pisiform. Exploration of the insertion of the radial slip was not undertaken, but pulling on the tendon produced flexion of the metacarpophalangeal joint of the ring finger.
Splitting of the ulnar nerve was observed 5 cm proximal to the pisiform bone. The smaller ulnar division of the nerve looped around the radial slip of the tendon of flexor carpi ulnaris to rejoin the ulnar nerve just proximal to the pisiform. More distally the ulnar nerve was found to divide normally into superficial and deep divisions in Guyon's canal. The radial slip of the tendon was excised and epineurolysis of the ulnar nerve performed. Postoperatively there was gradual but complete relief of the patient's symptoms and he resumed working normally 2 months later.
DISCUSSION
The flexor carpi ulnaris muscle arises from the medial epicondyle and receives a further contribution from a wide aponeurosis which forms a bridge between the medial border of the olecranon and the upper threefourths of the subcutaneous border of the ulna. Normally, both humeral and ulnar heads unite in a single muscle belly with a single tendon of insertion into the pisiform. The pisiform is morphologically a sesamoid bone in the tendon; by way of the pisohamate and pisometacarpal ligaments the muscle establishes more distal insertion. Anatomical variations of the flexor carpi ulnaris that have been reported previously are (1) extratendinous bands or extensions from the tendon of flexor carpi ulnaris to the fourth or more commonly the fifth metacarpal bone; (2) duplication of the flexor
Correspondence to Dr M. M. Al-Qattan, Section of Orthopaedic Surgery, GF307, General Hospital, 820 Sherbrook Street, Winnipeg, Manitoba, Canada, R3A 1R9.
M. M. Al-Qattan and F. Duerksen
190
Distal ^
A
Ulnar nerve
F I
Ulnar a rte ry
~
A-
4't
,
i
liiL I ,r:.%
0711,
* _
5
Flexor
N..
1%S' Ulnar nerve
ca
rpi
ulnaris
-ex ,
M.
Proximal
Fig. 1. The duplicated tendon of flexor carpi ulnaris with splitting of the ulnar nerve is shown. Note the smaller ulnar division of the ulnar nerve looping around (*) the radial slip of the flexor carpi ulnaris tendon.
carpi ulnaris tendon with insertion of the extra tendon onto the metacarpophalangeal joint of the little finger; (3) a fibrous or muscular extension from the tendon of the flexor carpi ulnaris to the carpal ligaments; and (4) duplication of the flexor carpi ulnaris muscle from the medial epicondyle to the pisiform. The above 4 anatomical variations were described by Testut & Latarjet (1928). Elliott Smith (1895) described a fifth anatomical variation, with the flexor carpi ulnaris muscle giving origin to an accessory abductor digiti' minimi muscle in the distal forearm to run a course superficial to the abductor digiti minimi with fused insertions. Clinically, the reported anatomical variations of flexor carpi ulnaris causing ulnar nerve compression include (1) fibrous bands from the belly of flexor carpi ulnaris and the ulnar artery (Holtzman et al. 1984); (2) the tendon of flexor carpi ulnaris at the pisiform giving origin to an anomalous muscle that passes between the motor and sensory branches of the ulnar nerve to be inserted into the carpal ligaments (Turner & Caird, 1977); (3) hypertrophy of flexor carpi ulnaris in the distal forearm (Harrelscn & Newman, 1975); and (4) splitting of the insertion of flexor carpi ulnaris with splitting of the ulnar nerve proximal to the pisiform (O'Hara & Stone, 1988; Zook et al. 1988).
Fig. 2. Diagrammatic representation of the anomaly. The insertion of the radial slip of the flexor carpi ulnaris (FCU) tendon was not surgically explored, but pulling on the slip produced flexion of the metacarpophalangeal joint of the ring finger.
In our patient, the duplicated flexor carpi ulnaris tendon is similar to the second anatomical variation reported by Testut & Latarjet (1928), except that the insertion of the extra tendon is to the ring instead of the little finger. REFERENCES
ELLIOTr SMITH G (1895) An account of some rare nerve and muscle anomalies with remarks on their significance. Journal of Anatomy and Physiology 29, 84-97. HARRELSON JM, NEWMAN M (1975) Hypertrophy of the flexor carpi ulnaris as a cause of ulnar nerve compression in the distal part of the forearm. Case report. Journal of Bone and Joint Surgery 57A, 554-555. HOLTZMAN RNN, MARK MH, PATEL MR, WIENER LM (1984) Ulnar nerve entrapment neuropathy in the forearm. Journal of Hand Surgery 9A, 576-578. O'HARA JJ, STONE JH (1988) Ulnar neuropathy at the wrist associated with aberrant flexor carpi ulnaris insertion. Journal of Hand Surgery 13A, 382-384. TEsTuJr L, LATARJET A (1928). Traite d'Anatomie Humaine, 8th edn, p. 1043. Paris: Gaston Doin. TURNER MS, CAIRD DM (1977) Anomalous muscles and ulnar nerve compression at the wrist. The Hand 9, 140-142. ZOOK EG, KUCAN JO, Guy RJ (1988) Palmar wrist pain caused by ulnar nerve entrapment in the flexor carpi ulnaris tendon. Journal of Hand Surgery 13A, 732-735.
