Central Slip Tenotomy for the Treatment of Chronic Mallet Finger: An Anatomic Study

ABSTRACT

Mallet finger (closed or open terminal tendon disruption) often results in chronic distal interphalangeal joint extensor lag, even with adequate initial treatment, due to slight lengthening of the healed tendon. Central slip tenotomy, described by Fowler, can clinically improve chronic distal interphalangeal extensor lag by allowing the finger extensor mechanism to slide proximally, thereby reducing the “slack” in the terminal tendon. No known anatomic or biomechanical study has studied the amount of extensor lag correctable with a central slip tenotomy. This study evaluated the potential of central slip tenotomy to restore distal interphalangeal joint extension, with respect to the severity of the pre-existing extensor lag.

Fifteen fresh frozen cadaver fingers (age range: 27-46 years) free of joint contractures, were used for this study. The skin over the dorsal aspect of the fingers was removed. The extensor tendon insertion was identified and a suture anchor placed into the bony insertion. The extensor tendon was sectioned over the distal interphalangeal joint, producing a mallet deformity. The braided suture-anchor suture was secured to the extensor tendon over the middle phalanx with two hemoclips to simulate lengthening of the tendon that may occur with healing. The degree of extensor lag produced was measured with an analog goniometer. A 5-lb weight attached to the proximal extensor tendon over the hand provided a uniform traction force. Central slip tenotomy was performed by lifting the extensor tendon from the ulnar side and completely sectioning the insertion on the middle phalanx. Measurements of the degree of extensor lag pre- and post-tenotomy were made.

Following sectioning of the extensor tendon over the distal interphalangeal joint, the average amount of extensor tendon lag produced was 45º with 5 lbs of proximal traction. After performing central slip tenotomy, the average amount of extensor lag correction was 35.7º. The largest correctable extensor lag measured 46º.

Several clinical studies demonstrate central slip tenotomy as an effective treatment of chronic mallet finger, but may not fully restore distal interphalangeal joint extension. In this study, a distal interphalangeal joint extensor lag of up to 46º was correctable with central slip tenotomy, but the average correction was 36º. Patients with a pre-existing extensor lag .36º may not achieve full correction with central slip tenotomy.