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Corresponding author: Shinsuke Morisaki, MD, PhD, Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan.
Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Japan
Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Japan
Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Japan
Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Japan
Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Japan
A patient presented with an abducted little finger due to the avulsion of the third volar interosseous muscle. For treatment, we transferred the fourth dorsal interosseous muscle arising from the ulnar side of the fourth metacarpal bone to the lateral band of the little finger.
A person with an abducted little finger has difficulty in scooping handfuls of water and inserting the affected hand into a pocket. Ulnar nerve palsy causes an abducted finger. Tendon transfer using the extensor tendon has been reported as a treatment for ulnar nerve palsy.
A patient presented with an abducted little finger caused by the traumatic avulsion of the third volar interosseous muscle. To treat it, we transferred the fourth dorsal interosseous muscle (4DIOM), arising from the ulnar side of the fourth metacarpal bone, to the lateral band of the little finger. This approach can be an effective treatment option for the reconstruction of adduction.
Indications and Contraindications
Our procedure is applicable for treating a traumatic rupture of the third volar interosseous muscle. When the cause of an abducted little finger is ulnar nerve palsy, the 4DIOM might also be weak. In this situation, it would not serve as a candidate for the reconstruction of an abducted little finger.
Surgical Anatomy
We used the superficial head of the 4DIOM, which originates from the fourth metacarpal bone, to create the force of adduction. The dorsal interosseous muscles are bipennate muscles and have 2 muscle heads: the superficial head and the deep head. The superficial head of the 4DIOM is on the ulnar side of the fourth metacarpal bone. The deep head is on the radial side of the fifth metacarpal bone. We, therefore, used the superficial head of the 4DIOM. After transferring the superficial head of the 4DIOM, the patient could still abduct the ring finger by contracting the deep head of the 4DIOM.
Surgical Technique
During the surgery, a zigzag incision was created between the fourth and fifth metacarpal bones on the palmar side. The 4DIOM arising from the ulnar side of the fourth metacarpal bone was detached from its insertion in the ring proximal phalanx (Fig. 1A ). It was then transferred and sutured to the radial lateral band of the little finger (Fig. 1B). When the 4DIOM was transferred, it was passed palmar to the deep transverse metacarpal ligament and dorsal to the superficial transverse ligament. The 4DIOM was sutured to the lateral band under slight tension with the metacarpophalangeal joint in flexion and the little finger in adduction.
Figure 1The surgical scheme. A The 4DIOM is detached at the insertion of the ring proximal phalanx. B The 4DIOM is transferred and sutured to the radial lateral band of the little finger.
The little finger was immobilized with the ring finger for 3 weeks, with the metacarpophalangeal joints flexed. After the 3 weeks of immobilization, the patient was allowed to perform active abduction and adduction exercises for the ring and little fingers.
Pearls and Pitfalls
To transfer the 4DIOM to the little finger, an adequate length of donor muscle should be preserved. Therefore, the 4DIOM should be detached from its insertion to the ring proximal phalanx.
Complications
The general risks of this surgery include pain, hematoma, scarring, and infection. When transferring the 4DIOM, the ulnar digital nerve of the ring finger should be protected.
Case Illustration
A 35-year-old woman worked as a cashier and experienced pain in her left hand when she held a heavy object with her little finger hyperabducted. She had tenderness in the web space between the ring and little finger. However, she continued working for 1 month because she had no limitation in the functions of flexion, extension, and abduction. Two months after the injury, she noticed that her little finger was abducted, and she could not adduct it actively. Therefore, she visited our clinic.
A physical examination revealed that the patient could not adduct the little finger, whereas abduction was intact (Fig. 2A ). The metacarpophalangeal joint of the little finger was stable, and the range of active motion, including flexion and extension, was not limited (Fig. 2B). She had no sensory disturbance of the fingers, which suggested that the ulnar nerve was intact. Coronal T2-weighted magnetic resonance imaging showed a high-intensity area in the third volar interosseous muscle where it is attached to the proximal phalanx of the little finger (Fig. 3). During the surgery, repairing the third volar interosseous muscle was impossible because of scarring and contracture. The 4DIOM was transferred and sutured to the lateral band of the little finger (Fig. 4). After 6 months, the patient could actively adduct the little finger. She had no loss of abduction, flexion, or extension of the metacarpophalangeal joint (Fig. 5). The angle between the ring and little finger in their maximal active adduction state improved from 22° before the surgery to 0° after the surgery. The visual analog scale pain score improved from 5 before the surgery to 0 after the surgery. The grip strength improved from 21.3 kg before the surgery to 28.3 kg after the surgery. At the 1-year follow up, the patient had no limitation or pain.
Figure 2A The bilateral hands are adducted. However, the patient is unable to adduct the little finger of the left hand. B Abduction of both hands is intact.
Figure 3The T2-weighted magnetic resonance image (coronal view) shows a high-intensity area on the third volar interosseous muscle attached to the little proximal phalanx (arrow).
Figure 4Surgical findings. A The 4DIOM (arrow) is visible. B It is detached at the site of the insertion of the ring proximal phalanx. C The 4DIOM is transferred and passed volar to the transverse intermetacarpal ligament sutured to the radial lateral band of the little finger.
In this report, we describe 2 important clinical issues. First, a rupture in the third volar interosseous muscle can cause an inability to adduct the little finger. Second, to restore adduction of the little finger, the fourth dorsal interosseous muscle was transferred to the radial lateral band, with satisfactory results.
An abducted small finger caused by ulnar nerve palsy has been reported, but few reports exist regarding traumatic ruptures.
reported a case of a hyperabducted small finger in a football player who had tackled a ball carrier. In our patient, the small finger was hyperabducted when she carried a heavy object.
When the third volar interosseous muscle is ruptured, the patient can actively flex and extend the metacarpophalangeal joint. The abduction force is also intact. Therefore, treatment that repairs the injured muscle is reasonable. However, when an injury is subacute, the ruptured muscle becomes contracted and is difficult to repair. Under that condition, reconstruction is an alternative. Tendon transfer has been suggested for the reconstruction of a traumatic rupture.
Several authors have suggested different methods for the surgical correction of an abducted little finger. Previous investigators have reported using the extensor digiti minimi.
However, this procedure has some concerns, such as the anatomic variability of the extensor system and possible loss of active extension and abduction. Furthermore, in this technique, the extensor digiti minimi should be rerouted to shift the extensor force to an adduction force. Therefore, determining the strength of the force is difficult.
Other investigators have reported using the extensor indicis proprius transfer.
This technique also requires sacrificing the extensor indicis proprius muscle-tendon unit and poses a potential loss of index finger extension. In this procedure, the extensor indicis proprius tendon is also split for elongation and passed dorsal to the extensor digitorum communis. Therefore, the procedure can be technically difficult. Some authors have reported tenodesis using a tendon graft. However, this technique has the risk of limiting the abduction of the little finger.
Our procedure has 3 merits. First, locating the 4DIOM is easy. A surgeon can readily detect the insertion of the muscle at the ulnar side of the ring proximal phalanx. Second, the 4DIOM is anatomically similar to the third volar interosseous muscle. Therefore, when transferring the 4DIOM, moving it ulnarly and suturing it to the radial lateral band of the proximal phalanx of the little finger is not complicated. Passing over other tendons is unnecessary. Therefore, determining the tendon strength is uncomplicated. Third, this technique is not associated with the risk of the loss of extensor and abduction forces.
This technique should be considered as a treatment option for the reconstruction of the little finger adduction force.
References
Blacker G.J.
Lister G.D.
Kleinert H.E.
The abducted little finger in low ulnar nerve palsy.
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