DISLOCATION, FINGER DISTAL INTERPHALAGEAL (DIP) JOINT

Isolated distal interphalangeal (DIP) joint dislocations are uncommon injuries. This is primarily due to the strong attachment of the flexor digitorum profundus (FDP) tendon, which maintains the alignment of the DIP joint.¹ Associated fractures, avulsions, tendon ruptures, and/or proximal interphalangeal (PIP) joint involvement are more common. The mechanism of injury is typically a violent hyperextension of the finger with an element of rotatory force, which is why ball-catching sports like basketball and football are often responsible.^2-4 Complex (irreducible) DIP dislocations are rare but may involve interposition or entrapment of the volar plate or FDP tendon in the joint. The recommended treatment for most DIP dislocations is conservative and should involve closed reduction followed by mobilization, while surgery is reserved for dislocations that are open, irreducible, or delayed, and when associated soft-tissue injury is present.⁵

Definitions

• A DIP joint dislocation occurs when the articular surface of the base of the distal phalanx is displaced off the articular surface of the head of the middle phalanx.

Hand Surgery Resource’s Dislocation Description and Characterization Acronym

D O C S

D – Direction of displacement

O – Open vs closed dislocation

C – Complex vs simple

S – Stability post reduction

D – Direction of displacement

• The primary description and characterization of DIP joint dislocations are done by noting the direction of the displacement of the distal phalanx relative to the head of the middle phalanx. The three possible directions of displacement are dorsal, lateral, and volar.⁶Dorsal DIP dislocations are the most common.
• Dorsal dislocations are further divided into two subtypes
  • Hyperextension: volar base of distal phalanx catches on the dorsal edge of the middle phalanx condyles in an extended position
  • Bayonet: base of distal phalanx is displaced on top of the neck of the middle phalanx in a position parallel to the longitudinal axis of the middle phalanx neck
• Dorsal dislocations are also more likely to be complex injuries, while volar dislocations carry a higher risk for instability after reduction and are more likely to have an extensor injury and complete collateral ligament rupture.⁴
  • The degree of displacement of the distal phalanx further characterizes DIP dislocations. In a true complete dislocation, the articular surface of the distal phalanx is no longer in contact with the articular cartilage of the head of the middle phalanx. If there is partial contact of the cartilaginous surfaces, this is a joint subluxation.⁶

O – Open vs closed

• Open DIP joint dislocations are extremely rare but urgent irrigation, debridement, open reduction, and ligament repair is indicated.
• The majority of DIP dislocations are closed; the skin is intact, and there is no route for bacteria to contaminate the joint space.
• In closed dislocations, the volar plate is typically avulsed from the middle phalanx and interposed in the DIP joint; in open dislocations, the FDP tendon tends to be displaced dorsal to the condyles of the middle phalanx.¹
• Open dislocations also commonly present with a transverse laceration in the flexion crease, which must be treated as a contaminated joint.⁵

C – Complex vs simple

• Almost all DIP joint dislocations are simple, meaning that reduction is easily achieved under digital anesthetic block and is not blocked by soft tissue being interposed in the joint between the distal and middle phalanx joint surfaces.
• Complex DIP joint dislocations do occur, but are rare.  Most of these cases involve dorsal dislocation in which the FDP tendon becomes interposed into the DIP joint, while volar dislocations are extremely rare.⁷ It is also possible that excessive traction may convert a simple dislocation into a complex one by pulling the avulsed volar plate into the joint space.⁸

S – Stability

• A stable DIP joint dislocation can be reduced and then put through an active range of motion (ROM) test under a local anesthetic block without redislocating.
• A stable DIP joint dislocation is stable to stress testing of the collateral ligaments in the radial/ulnar plane after reduction.

DIP dislocation with special and complex features other than fractures

Complex (irreducible) DIP dislocation

• Complex DIP joint dislocations are very rare.
• The mechanism of injury involves DIP flexion and torsional stresses.
• Majority are dorsal DIP joint dislocations that are closed injuries, while volar dislocations and open injuries are both rare.^4,7
• Complex DIP joint dislocations are generally caused by FDP tendon dislocation or interposition of the volar plate into the DIP joint.  Complex DIP dislocations can also be caused by a buttonhole tear through the volar plate or entrapment of the distal middle phalanx into a longitudinal split of the FDP tendon.⁵

Imaging

• X-ray
• MRI

Treatment

• Early diagnosis of complex DIP joint dislocations is important.
• Ideally, this is followed by open reduction and surgical anatomic repair of the collateral and tendon injuries.
• Postoperatively, early motion with dynamic extension splint helps improve the post-injury function.

Complications

• Stiffness
• DIP joint pain
• Persistent deformity

Outcome

• Early diagnosis, surgical repair, and therapy will give a functional outcome, but some limited ROM is to be expected.

Related anatomy^1,5

• Extensor tendon – central slip and lateral bands
• FDP tendon
• Dorsal capsule
• Proper collateral ligament
• Accessory collateral ligament
• Volar plate
• Osteology of the head of the middle phalanx and base of the distal phalanx

Overall Incidence

• DIP joint dislocations are very rare injuries and far less common than PIP joint dislocations.  One of the primary reasons for their low incidence is the strong attachment of the FDP tendon, which maintains the alignment of the DIP joint in these injuries. Consequently, avulsions of the FDP with no bony abnormality are more common, particularly in the ring finger.¹
• Catching injuries in sports like basketball, football, and volleyball are common causes for DIP joint dislocations.⁴

Related Injuries/Conditions

• Fractures of the middle phalanx
• Fractures of the distal phalanx, especially chip fractures at the volar or dorsal lip
• Collateral ligament injuries
• Volar plate injuries
• Central slip ruptures

Work-up Options

• X-ray
  • Should include anteroposterior (AP) and lateral views to evaluate for fracture and/or other joint deformity.⁵

The typical patient is a 25-year-old, left-handed male who was playing a pick-up game of basketball when the ball was quickly thrown at him. He didn’t have enough time to place his hands in the proper position to catch the ball, which severely hyperextended with his left index finger DIP joint. The trauma resulted in a DIP dislocation in this finger.  The patient experienced immediate pain and swelling in and around the joint. He subsequently took himself out of the game and sought medical attention in the local emergency room.

Post-treatment Management

• Many patients with DIP joint dislocations that are closed and reduced early can potentially exercise their finger on their own. If the reduction is stable after open reduction, active movements within the limits of pain can start immediately, but patients should avoid strong gripping activities for ~3 weeks.⁸
• However, patients with marked swelling and pain will need hand therapy to help reduce swelling and improve ROM and strength.
• Surgically repaired DIP joint complex dislocations, repaired collateral ligaments, and unstable DIP dislocations will definitely need hand therapy, custom splinting, and dynamic extension splints.

• Pain
• Stiffness
• Residual deformity
• Weak grip
• Pin tract infection
• Joint instability
  • The risk of complication is higher in volar dislocations.⁴

• Simple DIP joint dislocations that are treated early typically have an excellent outcome.³
• However, all patients with DIP joint dislocations should be warned that the DIP joint on the injured side will likely remain slightly larger than the opposite DIP joint because the stretched collateral ligaments are likely to heal with a little extra bulk (collagen).
• In one study, 30 cases of DIP joint dislocations were reduced either opened or closed, with 13 requiring K-wire fixation due to instability.  At a mean follow-up of 12.1 weeks, there was no recurrent dislocation.  At the final follow-up, volar dislocations had significantly higher pain scores and less DIP joint ROM compared with dorsal dislocations.⁴

• Simple closed DIP joint dislocations can be mobilized early and should get a good outcome with minimal loss of ROM and residual deformity.
• Unstable DIP joint dislocations require prolonged extension block splinting with continuous monitoring by hand therapy for splint adjustment, etc.
• Open and complex DIP joint dislocations require urgent surgical treatment.
• Classic hyperextension FDP tendon ruptures are rare in children because they are not involved in the same type of aggressive sports-related activities as teens and adults and the distal phalanx growth plate is the weaker link.  Thus, Salter fractures are more common than DIP dislocations.¹
• Complex DIP joint dislocations are considered the distal counterpart of complex metacarpophalangeal (MP) dislocations and the two have many parallels.⁸
• MRI - A high degree of clinical suspicion must be maintained for FDP dislocation or interposition of the volar plate into the DIP joint during evaluation.

New and Cited Articles

1. Banerji, S., Bullocks, J., Cole, P., et al. Irreducible distal interphalangeal joint dislocation: a case report and literature review. Ann Plast Surg 2007;58(6):683-5.PMID: 17522495
2. Abdelaal, A., Edwards, T. and Anand, S. Simultaneous dislocation of both the proximal and distal interphalangeal joints of a little finger. BMJ Case Rep 2016;2016.PMID: 26837941
3. Shyamsundar, S. and Macsween, W. Simultaneous dorsal dislocation of the interphalangeal joints in ring finger with proximal interphalangeal joint dislocation of the middle finger: case report and review of the literature. Hand Surg 2005;10(2-3):271-4.PMID: 16568526
4. Abouzahr, M. K. and Poblete, J. V. Irreducible dorsal dislocation of the distal interphalangeal joint: case report and literature review. J Trauma 1997;42(4):743-5.PMID: 9137270
5. Chung, S., Sood, A. and Lee, E. Principles of management in isolated dorsal distal interphalangeal joint dislocations. Eplasty 2014;14:ic33. PMID: 25328578
6. Merrell G, Slade J.F. Dislocations and ligament injuries in the digits. In: Wolfe, SW, Hotchkiss RN, Pederson WC, Kozin SH (eds): Green’s Operative Hand Surgery.  Philadelphia 2011: Elsevier Churchill Livingstone, pp. 291-332.
7. Hibino, N., Hamada, Y., Toki, S., et al. Irreducible Palmar Dislocation of the Distal Interphalangeal Joint Due to Closed Degloving of the Distal Phalanx of the Little Finger. Hand Surg 2015;20(2):304-6. PMID: 26051774
8. Sankaran, A., Bharathi, R. R. and Sabapathy, S. R. Complex dorsal dislocation of the distal interphalangeal joint: Perspectives on management. Indian J Plast Surg 2016;49(3):403-405. PMID: 28216823

Reviews

1. Banerji, S., Bullocks, J., Cole, P., et al. Irreducible distal interphalangeal joint dislocation: a case report and literature review. Ann Plast Surg 2007;58(6):683-5.PMID: 17522495
2. Abouzahr, M. K. and Poblete, J. V. Irreducible dorsal dislocation of the distal interphalangeal joint: case report and literature review. J Trauma 1997;42(4):743-5.PMID: 9137270

Classic

1. Pohl, A.L. Irreducible dislocation of a distal interphalangeal joint. Br J Plast Surg