Finger Dislocation

Etiology

Finger dislocations typically result from a direct blow to the digit or a fall onto an outstretched hand. These may occur in the dorsal, volar, or lateral planes, and they are categorized according to the position of the distal bone relative to the more proximal bone.[5] As such, finger dislocations can be classified as:

• Dorsal dislocations
• Volar dislocations
• Lateral dislocations
  • Either radial or ulnar
• Rotatory dislocations
  • Commonly occurs with a volar dislocation of the PIP joint with a rotational component due to rupture of only 1 collateral ligament
• Fracture-dislocations
  • Also occur, but are beyond the scope of this course [6] 

Dislocations are further classified as either "simple," in which the articular surfaces maintain some contact between the condyles, or "complex," where there is a complete loss of contact, often accompanied by bayonet apposition and interposition of the volar plate.[7]

Hyperextension or high-energy axial loads at the MCP joint can result in a dislocation. However, MCP joint dislocations occur infrequently due to protection against hyperextension afforded by the volar plate and the stability against radial and ulnar deviation provided by the collateral ligaments (see Image. Metacarpophalangeal [MCP] Joint Dorsal Dislocation, Radiograph). While MCP joint dislocations most commonly occur at the index finger, dislocations at the middle finger occur more frequently when subjected to ulnar stress during hyperextension.[3] Most MCP joint dislocations are dorsal.[5][8]

Proximal interphalangeal (PIP) joint dislocations are common in athletic settings and are sometimes referred to as “coach’s finger” due to their frequent occurrence and tendency to be underestimated or improperly managed in sports environments. (see Image. Proximal Interphalangeal [PIP] Joint Dorsal Dislocation, Radiograph). Similar to MCP dislocations, PIP dislocations are typically dorsal. Dorsal dislocation results from longitudinal compression and hyperextension, commonly by a ball hitting the fingertip. These most commonly occur at the middle finger and are associated with volar plate, collateral ligament, and dorsal joint capsular injuries. Swan neck deformities may occur in dorsal dislocations from volar plate injury.

Additionally, interposition of the volar plate within the joint may occur, causing malalignment, oblique rotation, and challenging or unsuccessful reduction. Volar dislocation of the PIP joint can occur with and without rotation of the intermediate phalanx. These dislocations are infrequent and can be associated with injury to the central slip of the extensor mechanism. An untreated rupture of the central slip after a PIP joint dislocation is associated with a boutonniere deformity. Lateral PIP dislocations can also occur and involve disruption of the collateral ligaments. Finally, rotary volar dislocations may occur when the phalanx displaces and rotates around 1 collateral ligament, allowing the proximal phalanx to wedge between the lateral band and extensor mechanism. The classic lateral radiographic finding has the colloquial description of the “finger trap”.[1] 

Dorsal DIP joint dislocations occur most frequently and are associated with fractures and skin injuries. (see Image. Distal Interphalangeal [DIP] Joint Dorsal Dislocation, Radiograph). They are not always associated with flexor tendon avulsions but may have an interposed volar plate causing a nonreducible dislocation. Volar DIP joint dislocations are similar to volar PIP joint dislocations, as both are associated with extensor tendon injuries. The lateral DIP joint is more likely to have postreduction instability than volar or dorsal dislocations. An isolated DIP joint dislocation without related injuries to the soft tissues or fractures is rare and is commonly managed with closed reduction and splinting.[9] 

Epidemiology

Overall, dislocations of the fingers are fairly common injuries, with an estimated incidence of 11.1 per 100,000 person-years in the United States.[10] Most of these injuries involve the PIP and DIP joints, while MCP dislocations are associated with an incidence of less than 1 per 100,000 person-years annually. Most dislocations occur in adolescent or young adult men between the ages of 15 and 19 and commonly occur in basketball and football players.

History and Physical

Examiners must conduct a thorough history, which includes the mechanism of injury, hand dominance, previous finger injuries, risk factors such as Ehlers-Danlos syndrome, occupation, and recreational activities. Patients with finger dislocations typically present with joint-specific pain, associated swelling that may extend to adjacent areas, and an observable deformity at the injury site. Some dislocations are reduced by the patient or another individual before presentation, so clinicians should specifically inquire whether a reduction was attempted before evaluation.

During physical examination, the inspection should include an evaluation of any clinical deformities, skin integrity, swelling, and ecchymosis.[11] Dimpling or puckering of skin may indicate soft tissue interposition. If the examiner identifies a deformity, the examiner must also determine if there is any malrotation or angulation. To assess this, the patient is asked to make a fist (if possible) with the fingertips pointing toward the scaphoid. Overlapping or "scissoring" indicates a rotational component to the injury. Alternatively, the digital cascade can be evaluated through the tenodesis effect by passively flexing and extending both wrists.

The alignment of the fingers can then be compared. Furthermore, palpation can be used to determine the location of maximal tenderness.[5] Each joint should also be assessed for both active and passive range of motion, as tolerated by the patient.[12] Moreover, a thorough neurovascular examination is imperative in evaluating the injured hand. To identify a potential digital nerve injury (such as traction neuropraxia), the injured digit should be compared to the same digit on the unaffected hand for light touch, pinprick, and/or 2-point discrimination. On the opposite hand, the digital artery can be evaluated by comparison to an unaffected digit using capillary refill.  

Stability testing of the injured joint should be performed (typically following reduction) to assess the functional competency of the stabilizing soft tissue structures. Increased laxity or gross instability on testing suggests injury to 1 or more of these structures. A dorsally directed force at the joint is used to evaluate the integrity of the volar plate, while a volarly directed force assesses the dorsal capsule and extensor coverage. Lateral stress testing should be performed with the affected joint in both full (neutral) extension and at 30° of flexion. A radially-directed force tests the ulnar collateral ligament, while an ulnarly-directed force tests the radial collateral ligament.

In addition, in the setting of a suspected (volar) PIP dislocation, the Elson test should be performed to evaluate the integrity of the central slip. This is done by placing the affected digit over the edge of a table and flexing the PIP joint to 90°. The examiner places their finger over the patient's middle phalanx and asks the patient to actively extend the digit against resistance. If the central slip is intact, the patient exhibits strong PIP extension, and the DIP joint is flaccid. However, a central slip rupture would be suspected if there is weak PIP extension while the DIP becomes rigid.

Evaluation

The standard of care for the initial evaluation of injuries to the hand is plain film imaging (see Image. Left Proximal Interphalangeal Dislocation, Radiograph). Posteroanterior (or anteroposterior), oblique, and true lateral radiographic views are necessary for each affected digit. The films must demonstrate an unobstructed view of the affected finger. Widening of the joint space may indicate soft tissue interposition (such as the volar plate). In the setting of an MCP dislocation, sesamoid entrapment strongly indicates a complex dislocation.[13] Examiners should remember that rotational deformities are more commonly diagnosed on physical examination than plain films.[5] In addition to plain radiographs, ultrasound remains an active area of investigation for its potential to detect associated fractures and tendon ruptures in finger dislocations.[14] 

Treatment / Management

The treatment of MCP, PIP, and DIP joint dislocations may be nonoperative or operative, predominantly depending upon the ease of reduction and postreduction joint stability.[15][16] Before any reduction attempt, a digital nerve block using lidocaine, bupivacaine, or a similar anesthetic should be administered to provide adequate anesthesia.[17] Posttreatment splinting and/or buddy taping protocols vary by the type of dislocation, resultant stability, and clinician preference. (A1)

Metacarpophalangeal Joint Dislocation

Nonoperative management

Nonoperative management of MCP joint dislocations consists of closed reduction and splinting. The clinician can achieve closed reduction of a dorsal dislocation by applying extension and axial compression to the proximal phalanx, thereby relocating pressure over the phalangeal base to glide it into position. This approach differs from the traction technique used in PIP joint dislocations. Multiple reduction attempts should be avoided, as the inability to reduce may indicate volar plate interposition requiring open reduction.

Additionally, repeated attempts at MCP reduction have the potential complication of displacing the volar plate or flexor tendons between articular surfaces. Once reduced, a dorsal-block splint should be applied, followed by early range of motion exercises. A volar MCP dislocation is typically reduced by flexing the joint while applying a dorsally-directed force over the proximal phalanx volarly. The finger should then be splinted for approximately 3 weeks to 6 weeks, followed by an additional 2 weeks of buddy taping. 

Operative management

Operative intervention is indicated for irreducible MCP joint dislocations, as volar plate involvement is highly likely in these cases. Open reduction of the MCP joint can be performed using either a dorsal or volar approach. However, the dorsal approach is preferable as it carries a lower risk of neurovascular injury. After surgery, the wrist is splinted in 30° of extension with the MCP joint in slight flexion for 2 weeks. The recommendation is that the PIP and DIP joints not be immobilized. Recovery of preinjury motion may take several weeks to months.[18]

Volar approach for MCP joint dislocation 

To prevent neurovascular damage, a volar Bruner-like incision is made over the MCP joint, between the proximal and distal volar creases, while the patient is under general anesthesia. The flexor tendons are on the ulnar side, whereas the neurovascular bundle is on the radial side. The volar plate's proximal connection on the metacarpal is usually ruptured. By releasing the A1 pulley, the tension created by the muscle-tendon constriction around the metacarpal neck is released. Superficial transverse ligament, natatory ligament, and palmar fascia are then incised. The joint can be manually reduced following a longitudinal incision in the volar plate. The volar plate's free slips are wrapped around the metacarpal head and secured using sutures. A dorsal-block splint is applied following skin closure. After healing, active flexion activities are promoted. The splint is removed approximately 3 weeks later, and active extension exercises are introduced.[7]

Dorsal approach for MCP joint dislocation

Over the MCP joint, a dorsally curved incision is made either on the ulnar or radial aspect. Usually, a dorsoradial incision is made for the first and second MCP joints, but a dorsoulnar incision is preferred for the fourth and fifth MCP joints. The skin flaps are raised, protecting sensory nerve branches and longitudinal vasculature. The extensor mechanism is incised longitudinally along the extensor digitorum tendon. A capsulotomy of the MCP joint is made longitudinally. An elevator is used to shift the intervening volar plate volarly, which reduces the MCP joint. Clinical testing is performed upon reduction to assess stability. Following surgery, the MCP joint is immobilized for 2 weeks at 30° of flexion, and then dorsal-block splinting is performed for 4 weeks.[19] (B3)

The benefits of the dorsal open reduction method include adequate volar plate visibility and prevention of digital neurovascular injury. However, this procedure could require longitudinal division of the volar plate and extensor apparatus, potentially impairing MCP stability.[20] The volar open reduction method offers several benefits, including clear visibility of the MCP joint, which facilitates the surgical removal and realignment of the volar plate. In a volar approach to the MCP joint, the radial digital nerve and the neurovascular structures volar to the lumbrical muscles are at risk.[21] The dorsal approach has been shown to be safe for the open reduction of complex MCP dislocations. In this procedure, the deep transverse ligament does not need to be divided. Both approaches provide a stable MCP joint with appropriate functional outcomes.[22](B3)

Proximal Interphalangeal Joint Dislocation

Nonoperative management

For closed reduction of dorsal PIP joint dislocations, the clinician should apply slight extension with longitudinal traction and, with the other hand, apply volarly-directed pressure to the dorsal aspect of the middle phalanx. After reduction, the examiner should evaluate the joint for stability in all planes and then obtain postreduction radiographs. The normal contour of the dorsal aspect of the PIP joint on lateral plain film is "C"-shaped. If, after reduction, this contour presents a "V" shape, it may indicate persistent dorsal subluxation, which can lead to severe stiffness and post-traumatic osteoarthritis.[3] Dorsal PIP joint dislocations are often stable after reduction and are treated with buddy taping for 3 to 6 weeks. However, if unstable following reduction, a dorsal-block splint at 30° of flexion is applied. Volar PIP dislocations are the least common, but reducing the volar PIP joint dislocation is generally successful. The reduction is performed by applying mild traction with the PIP and MCP joints in flexion. After reducing the volar dislocation, an extension splint is applied for 6 to 8 weeks.

Lateral dislocations may be more likely to require operative intervention. Closed reduction requires relaxation of the extensor tendon and lateral bands through wrist extension and MCP flexion, respectively. Then, the middle phalanx is gently rotated back into position. If the lateral PIP joint reduction affords a full range of motion without subluxation, then the joint is not grossly unstable. Splinting and reassessment in 2 to 3 weeks are recommended in these cases, although buddy taping has also been described as an alternative approach. A recent randomized controlled trial compared buddy taping versus aluminum digital splinting treatment of hyperextension-type injuries and found no difference in strength, pain, or function at 3 weeks. However, the buddy tape did show an earlier range of motion and decreased edema.[23](A1)

Operative management

Unstable dislocations require referral for orthopedic evaluation and possible open treatment. Indications for operative intervention for PIP joint dislocations include persistent joint instability, significant ligament/soft tissue/tendon injuries, or dislocations that are not reducible.[24] 

Dorsal approach for PIP joint dislocation

For volar PIP dislocations, the dorsal approach is indicated.[25] Midline longitudinal, curvilinear, and lazy "S" incisions are used for the dorsal approach of the PIP joint. Full-thickness skin flaps are elevated, preserving the sensory nerve branches and the longitudinal superficial vasculature, while the transverse vein may be ligated. After exposing the extensor aponeurosis, there are 3 ways to approach the PIP joint capsule: between the central and lateral slips, splitting the central slip (Swanson approach), and flap elevation of the central slip (Chamay approach).[26][27] A capsulotomy is made transversely, preserving the central slip and extensor tendons.

Volar approach for PIP joint dislocation

A Bruner or zigzag incision is made between the flexor crease and the PIP joint. After raising thick skin flaps, flexor pulleys are released (C1, A3, C2). The A2 and A4 pulleys should not be incised as they could lead to bowstringing of the flexor tendons. The flexor tendons are then retracted, and the joint capsule is incised. The volar plate is mobilized, the joint is reduced, and a layered closure is performed.[28](B2)

Lateral approach for PIP joint dislocation

A mid-axial incision is made over the PIP joint, and a plane is developed between the dorsal extensor tendon and the volar digital neurovascular bundle. The transverse retinacular and collateral ligaments are incised to expose the PIP joint, which is later repaired after reduction.[29]

Distal Interphalangeal Joint Dislocation

Nonoperative management

Dorsal dislocations are reduced with longitudinal traction and a volarly-directed force on the dorsal distal phalanx with the DIP joint in flexion. Often, the reduction occurs with relative ease, followed by splinting of the DIP joint in 10° to 20° of flexion for 2 to 3 weeks if persistent instability persists.[9] A dorsally-directed force at the distal phalanx, coupled with traction, is used to reduce a volar DIP dislocation, typically followed by 6 weeks of extension splinting.

Operative management

Irreducible dislocations are typically due to volar plate (for dorsal dislocations), flexor digitorum profundus (for open dorsal dislocations), or terminal tendon (for volar dislocations) interposition and require surgical intervention. A zigzag or mid-axial incision is made centered over the DIP joint. The entrapped volar plate, flexor digitorum profundus, or terminal tendon, is mobilized to reduce the DIP joint. After confirming concentric reduction and stability, range of motion exercises are initiated immediately after operative reduction.

Differential Diagnosis

The differential diagnosis for finger dislocations includes: 

• Fracture-dislocation
• Isolated collateral ligament injuries/sprains
• Boutonniere or pseudo-Boutonniere deformity
• Mallet finger
• Swan neck deformity
• Dupuytren contracture

Prognosis

The prognosis for finger dislocations varies depending on the joint and injury characteristics. MCP joint dislocations often require operative intervention due to the complexity of the surrounding anatomy, and recovery to preinjury range of motion may take several months to achieve.[18] In contrast, most PIP joint dislocations are stable following reduction; however, lateral PIP dislocations can present with ongoing instability and may require additional management. Isolated DIP joint dislocations are rare, but similar to PIP injuries, lateral DIP dislocations may also demonstrate persistent instability following reduction.[9]

Complications

Complications for finger dislocations include:

• Chronic stiffness
• Persistent pain
• Post-traumatic arthritis
• Residual deformities
• Persistent swelling
• Loss of hand function
• Overtreatment
  • This includes prolonged splinting and multiple attempts at reduction of volar PIP joint dislocations, which increases the likelihood of volar plate scarring and flexion contractures.