Boutonniere Injuries

Boutonniere injury involves rupture of the central slip of the extensor mechanism at its insertion into the base of the MP. Injuries may be due to either direct trauma to the dorsum of the PIP joint or an acute flexion force applied to the PIP joint with opposed active extension. The term boutonniere is derived from the French word for buttonhole, which refers to a split that occurs in the dorsal covering of the PIP joint where the central slip of the extensor mechanism avulses from its insertion. Late cases with a classic boutonniere deformity consisting of flexion of the PIP joint and hyperextension of the DIP joint are readily apparent on physical examination. However, the acute case can easily be missed.

Acutely, the athlete presents with swelling about the PIP joint with inability to actively extend the joint. Diagnosis may be confused with more common PIP joint sprain or even dislocation that has been reduced. Radiographs are frequently normal. However, a small avulsion at the dorsal base of the MP may be present in some cases. An effective diagnostic measure in acute cases is to perform a digital block, thus limiting pain and guarding, and to ask the patient to actively extend the PIP joint. If the patient is unable to do this, it is most likely due to rupture of the extensor mechanism.

The goal of treatment of an acute central slip injury is to prevent the late classic boutonniere deformity. If this lesion is untreated or splinted in flexion as is sometimes done for PIP joint sprains, the unopposed pull of the flexor digitorum sub-limis along with swelling of the PIP joint will maintain a flexion deformity. The disrupted ends of the central slip will migrate proximally and the lateral bands will migrate volarly, thus giving a classic boutonniere posture (Fig. 41-24). Burton81 has

Figure 41-24 A, Rupture of the central slip of the extensor mechanism. B, Central slip rupture with volar migration of the lateral bands causing flexion of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint (DIP). EDC, extensor digitorum communis. (From Hastings, Rettig, Strickland: Management of Extra-articular Fractures of the Phalanges and Metacarpals. Philadelphia, Elsevier, 1992.)

B DIP hyperextension

Figure 41-24 A, Rupture of the central slip of the extensor mechanism. B, Central slip rupture with volar migration of the lateral bands causing flexion of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint (DIP). EDC, extensor digitorum communis. (From Hastings, Rettig, Strickland: Management of Extra-articular Fractures of the Phalanges and Metacarpals. Philadelphia, Elsevier, 1992.)

described three stages of deformity: stage 1, dynamic imbalance that is fully correctable passively; stage 2, extensor tendon contracture that is not passively correctable but does not involve the joint structure; stage 3, fixed contracture with joint changes involving a collateral ligament and volar plate scarring and intra-articular adhesions.

Once the diagnosis of acute extensor disruption at the base of the MP is made, splinting of the PIP joint in full extension is begun. The DIP joint is allowed to be free, and active flexion of this joint is encouraged. Active DIP joint flexion with the PIP joint maintained in extension is encouraged as this helps to maintain the lateral bands in anatomic position dorsal to the PIP joint. Splinting should be continued for a period of 6 to 8 weeks. The athlete may continue to compete with the protective splint holding the joint in full extension or taping to prevent full flexion of the PIP joint during participation and splinting all other times.

If avulsion of a significant portion of the MP is present, open reduction and internal fixation may be indicated. The PIP joint is maintained in full extension by placement of a transarticular pin and the fragment is fixed by either a pull-out suture or small K wires. The transarticular pin may be removed in 10 days to 2 weeks. A protective splint with the PIP joint in extension should be worn for an additional 2 months.

Volar PIP joint dislocations result in rupture of the central slip along with collateral ligament rupture. In these cases, which are frequently irreducible by closed means, authors have recommended open reduction and repair of the central slip and

Figure 41-25 Three-stage exercise program for boutonniere deformity.

A, The index finger of the opposite hand is placed on the dorsum of the involved proximal interphalangeal (PIP) joint. The uninjured thumb is placed on the flexor aspect of the distal interphalangeal (DIP) joint.

B, The PIP joint is passively extended as tolerated. C, Patient actively flexes the DIP joint over the thumb of the opposite hand. (From Hastings, Rettig, Strickland: Management of Extra-articular Fractures of the Phalanges and Metacarpals. Philadelphia, Elsevier, 1992.)

Figure 41-25 Three-stage exercise program for boutonniere deformity.

A, The index finger of the opposite hand is placed on the dorsum of the involved proximal interphalangeal (PIP) joint. The uninjured thumb is placed on the flexor aspect of the distal interphalangeal (DIP) joint.

B, The PIP joint is passively extended as tolerated. C, Patient actively flexes the DIP joint over the thumb of the opposite hand. (From Hastings, Rettig, Strickland: Management of Extra-articular Fractures of the Phalanges and Metacarpals. Philadelphia, Elsevier, 1992.)

transarticular pinning for 3 weeks.82 If these dislocations can be reduced closed, they should be treated as an acute boutonniere injury with splinting to protect the central slip.

Frequently the physician is presented with boutonniere injuries that have been neglected or treated inappropriately. Treatment of chronic boutonniere deformity has been well documented and involves the use of dynamic splinting and in some cases the use of serial casts in order to decrease the flexion contracture of the PIP joint. Of most importance is a boutonniere exercise program in which the PIP joint is extended to a maximum degree, and active flexion at the DIP joint is instituted (Fig. 41-25). These exercises must be done regularly for long periods of time.

Surgery for the correction of chronic boutonniere deformity is very rarely indicated. In some cases, once full extension has been achieved passively, an Elliott type repair of the extensor mechanism may be performed followed by postoperative transarticular pin fixation for 3 weeks, and then rehabilitation.

It is important to carefully evaluate the finger to differentiate boutonniere from pseudoboutonniere injuries described by McCue and Wooten.71 Pseudoboutonniere occurs if hyperextension injury results in rupture of the proximal attachment of the volar plate with fibrosis and occasional calcification leading to a flexion contracture at the PIP joint. This lesion is not usually accompanied by a hyperextension deformity at the DIP joint, and calcification may often be seen on lateral radiographs at the proximal volar plate attachment.

The pseudoboutonniere can frequently be treated just by simple splinting; however, in cases of greater than 45 degrees of flexion contracture, an open release of the proximal portion of the volar plate may be undertaken.

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