Repair of a Chronic Degenerative Sagittal Band Rupture of the Right Ring Finger

Sagittal band rupture is an injury that causes rupture of the sagittal band, leading to subluxation of the extensor digitorum communis (EDC) tendon at the metacarpophalangeal (MCP) joint. The sagittal band encircles the EDC tendon at the MCP joint and functions as an important part of the extensor mechanism to stabilize the extensor tendon. It is a relatively uncommon injury, typically involving the long finger, that may occur with direct trauma in athletes or atraumatically in inflammatory or spontaneous cases; the mechanism may be acute or chronic. The common presentation involves pain and swelling at the MCP joint, visualization of extensor tendon subluxation during flexion, and inability to actively extend the MCP joint from a flexed position. The treatment for chronic rupture, as in this case, involves surgical repair followed by six weeks in a relative motion splint, in which the injured MCP joint is placed in greater extension relative to adjacent joints. The video here demonstrates direct repair of a chronic degenerative sagittal band rupture of the right ring finger.

Sagittal band rupture is an uncommon injury that involves rupture of the sagittal band, leading to subluxation of the extensor tendon at the metacarpophalangeal (MCP) joint. The sagittal band is a retinacular structure that encircles the extensor digitorum communis (EDC) tendon at the MCP joint via its superficial and deep layers. It has radial and ulnar components that attach to the palmar plate and transverse metacarpal ligaments.¹ The sagittal band functions as an important part of the extensor mechanism to stabilize the extensor tendon and prevent bowstringing during hyperextension.^1, 2 

The mechanism of sagittal band rupture can occur traumatically or atraumatically and more commonly injures the radial sagittal band.³ Traumatic cases typically involve a direct blow to the MCP joint and is seen in boxers and martial artists, hence the term “boxer’s knuckle.”¹ They can also occur under forced flexion or extension of the MCP joint or an open injury to the extensor mechanism. In atraumatic cases, ruptures can occur either spontaneously, via daily activities such as flicking a finger or crumpling paper, or in inflammatory settings such as osteoarthritis or rheumatoid arthritis.^1, 2

The ruptures are classified into three types, as originally described by Rayan and Murray in 1994.³

• Type I: sagittal band rupture without tendon instability
• Type II: sagittal band rupture with tendon subluxation
• Type III: sagittal band rupture with tendon dislocation

The patient typically complains of pain and swelling at the MCP joint, most commonly of the long finger. They may also describe a sensation of snapping at the MCP joint.

On exam, subluxation or dislocation of the extensor tendon towards the edge of the metacarpal head or into the intermetacarpal recess upon MCP flexion may be visualized.¹ The patient may have extensor lag or decreased flexion due to pain. To differentiate between sagittal band injury and extensor tendon dysfunction, the patient will be unable to actively extend the flexed MCP joint but will be able to maintain extension once passively placed in that position. In extensor tendon dysfunction, the patient will be able to actively extend the flexed MCP joint but unable to maintain extension.² The patient may also have pseudo-triggering, secondary to crepitus occurring with subluxation, which is important to distinguish from true trigger finger to prevent unnecessary trigger release surgery.¹

Imaging allows for confirmation of the diagnosis of sagittal band rupture. A series of hand radiographs in posterior-anterior, lateral, and oblique views are obtained to rule out fracture or dislocation.¹ Additionally, a Brewerton view, an anterior-posterior picture of the MCP joint in 65° flexion in which the x-ray beam is directed 15° radially, may help to further characterize pathology in the joint.^{1, 2} Dynamic ultrasonography can provide visualization of tendon instability during flexion.⁴ Magnetic resonance (MR) imaging can confirm the rupture, and an MR arthrogram can show whether the joint capsule is intact, as rupture indicates poor prognosis for nonsurgical treatment.¹

Most acute and closed injury cases can be treated nonoperatively with a relative motion splint that is placed as soon as possible, within three weeks after injury.^{2, 5, 6} The relative motion splint places the injured MCP joint in 15° to 20° of greater extension relative to adjacent digits, markedly reducing the amount of force placed on the tendon. The splint is worn for six weeks and full flexion and extension of digits as able in the splint is encouraged.⁶ Little to no additional therapy is required after this time and is efficacious in up to 71–84% of cases.¹

Surgery is indicated for open injuries, chronic ruptures and those who fail nonoperative treatment. The general technique involves repair of the sagittal band and recentralization of the extensor tendon, performed under local anesthesia to assess for tendon stability.^{1, 2} There have been numerous methods reported in literature regarding strategies to augment the repair or stabilize the tendon when direct repair is insufficient. They primarily differ in what structure the proximal or distal EDC strip is routed around before being sutured to the intact EDC or joint capsule. These include the volar interosseous muscle, deep transverse metacarpal ligament, radial collateral ligament, and lumbrical tendon.¹ Others have reported success with tendon graft pulleys, using the palmaris longus, juncturae tendinum, or extensor retinaculum routed directly through the metacarpal head.⁶ In chronic cases, release of tight ulnar structures or imbrication of the radial sagittal band may be required.² There is considerable debate on whether the joint capsule should be repaired, as excessive repair may lead to decreased range of motion.^{1, 2}

The goals of treatment, as alluded to above, are to ultimately minimize pain, restore function, and stabilize the extensor tendon for the patient. In the case here, the patient received surgery due to the chronic nature of the rupture, completed through direct repair which did not necessitate augmentation.

The repair is performed under local anesthesia in a wide-awake fashion. This allows for assessment of subluxation after sagittal band repair; however the surgery may be performed under other forms of anesthesia. The surgical site is marked out directly over the fourth metacarpal head, consistent with zone five of the extensor mechanism. Blunt dissection is performed until the extensor tendon and sagittal band is fully exposed. Once exposed, active motion by the patient confirms subluxation of extensor tendon, most commonly in the ulnar direction, which implies that the radial sagittal band is incompetent. In cases of acute ruptures, the ends of the sagittal band are readily approximated and repaired. In chronic ruptures, adequate tissues may not be available for primary repair. However, in this case, adequate tissue is confirmed for primary repair along the radial side. Additionally, in chronic cases, the competent side often becomes contracted and may require release to help with centering of the extensor mechanism, as performed here. For chronic ruptures, an imbrication of the extensor mechanism is required, completed via nonabsorbable 2-0 or 3-0 sutures in a figure-of-eight fashion.

Following surgery, the wound is washed, closed and dressed, with the hand placed in an Orthoplast yoke splint to be worn for the next six weeks. This is a hand-based splint that places the MP joint in extension relative to the other MP joints, to offload the repair while still allowing for tendon excursion to occur. However, both the DIP and PIP joints remain free, and the patient is allowed to move their fingers within the splint.

The case here consists of a repair of a chronic degenerative sagittal band rupture of the ring finger. Sagittal band ruptures represent a type of extensor tendon injury that result in subluxation of the extensor tendon over the metacarpal head with active flexion and extension. They can either be traumatic in origin or atraumatic, as in this case. Most acute cases are treated nonoperatively via splinting, with 71% or more achieving resolution of symptoms.^{2, 7} Chronic ruptures warrant surgery as in this case, with outcomes similar to or better than that of nonoperative treatment.^{1, 3, 8}

The major complication for sagittal band rupture repair is recurrence; however, these are very rare with insufficient literature to describe these cases.^{1, 3, 8} In general, there remains dispute over the ideal method for repair, especially regarding augmentation methods of the sagittal band. One option is to transfer the ulnar-sided juncturae tendinum through the repaired radial sagittal band.¹ Another option is to utilize the proximal or distal strips of the EDC tendon to route around the volar interosseous muscle, deep transverse metacarpal ligament, radial collateral ligament, or lumbrical tendon.^{1, 2} A third option involves creating tendon graft pulleys, via the palmaris longus, juncturae tendinum, or extensor retinaculum that is passed through the metacarpal head and dorsal to the tendon before being sutured to itself.⁶ All of these methods have been performed with excellent results.^{1, 2} There is also debate on management of joint capsule injury in cases of concomitant rupture. There have been studies demonstrating success and return to full activity with capsule repair while other studies warn against the potential for decreased MCP flexion.^{1, 2} Despite the variation in surgical technique, postoperative care is relatively consistent among surgeons. The relative motion splint, placed for four to six weeks, is superior to the splint that was previously used which placed the MCP joint in a neutral position.² 

However, there is still a need for more robust studies and literature regarding ideal surgical technique and clarity on joint capsule repair. Studies with larger cohort sizes will allow for higher quality conclusions and lend towards standardization of care. 

x1 3-0 nonabsorbable suture, Ethibond Excel

x1 orthoplast yoke splint

Nothing to disclose.

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.