eMedicine Specialties > Sports Medicine > Wrist and Hand

Hand Dislocation

Author: Jeff Chan, MD, MS, FACEP, Clinical Instructor, Stanford University; Staff Physician, Department of Emergency Medicine, Regional Medical Center of San Jose
Coauthor(s): Eleby R Washington III, MD, FACS, Associate Professor, Department of Surgery, Division of Orthopedics, Charles R Drew University of Medicine and Science; Igor Boyarsky, DO, Director of Triage, Assistant Professor, Department of Emergency Medicine, King-Drew Medical Center, University of California at Los Angeles
Contributor Information and Disclosures

Updated: Mar 27, 2009

Introduction

Background

Dislocations in the hand are common injuries in sports and in occupational settings, often appearing to be minor. If the athlete, trainer, or coach has already reduced the dislocation, it appears unimpressive compared with a major knee injury or a shoulder dislocation. However, hand dislocations have real potential for long-term disability in sports and other areas of life if adequate reduction is not performed, if associated injuries are not identified and appropriately treated or referred, and if potential complications of the injury and its treatment are not foreseen. The judgment of the initial treating physician can be critical in determining the long-term outcome of these injuries. 

For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center. Also, see eMedicine's patient education articles, Broken Hand, Broken Finger, and Finger Injuries.

Frequency

United States

The annual incidence of all types of dislocations in the hand is approximately 67,000 in the United States. Most hand dislocations are sports or occupational injuries, with a lesser number sustained in falls and traffic collisions (sometimes associated with airbag deployment).^1,2,3,4,5 Most of these are dislocations at the proximal interphalangeal (PIP) joint, because the greater range of motion (ROM) of the PIP joint makes it more vulnerable to injury. Of the PIP dislocations, most are dorsal (see Images 4-5 and 9-10 or below).⁶

Functional Anatomy

The bony anatomy of the PIP joint consists of medial and lateral condyles on the proximal phalanx, with matching concavities on the associated distal phalanx. This allows for a wide ROM in flexion and extension, but it is relatively rigid in abduction and adduction, making it a hinge (ginglymus) joint functionally. DIP joint bony anatomy is similar but with surrounding soft tissue providing more restriction in flexion. The extrinsic flexors across both joints are at least 4 times stronger than the extensors, allowing flexion contractures to develop very rapidly, especially with immobilization in flexion. Adequate ROM, especially at the PIP joint, is critical for normal hand function.

Both types of interphalangeal joints are supported by similar soft-tissue structures on all 4 sides, which includes the volar plate on the palmar side (the integrity of this structure is essential to a stable reduction), collateral ligaments on the radial and ulnar sides, and the extensor complex (central slip, lateral bands, and hood) dorsally. These structures attach to and reinforce the joint capsule. For a dislocation to occur, at least 1, often 2, and sometimes 3 of these structures must be significantly injured.

The volar plate is a roughly triangular structure with its base oriented distally, attaching to the volar base of the middle phalanx with its tip attaching to the distal aspect of the proximal phalanx. The volar plate functions largely in limiting hyperextension. Thus, it is nearly inevitably injured in dorsal dislocations.

The collateral ligaments restrict the joint from opening to varus or valgus stress and are also commonly injured in dorsal dislocation. Injury to the radial collateral ligament is about 6 times more common than injury to the ulnar collateral ligament. The extensor complex over the PIP joint consists of the central slip, which attaches to the base of the middle phalanx; the lateral bands, which run dorsolaterally on each side; and the transverse retinacular ligament, which connects these structures and extends laterally. These structures help to limit volar movement of the base of the middle phalanx and are thus commonly injured in volar dislocations at the PIP joint, with the middle phalanx either tearing the central slip from its insertion or buttonholing through the transverse retinacular ligament between the central slip and one of the lateral bands.

The MCP joint is thought to be an ellipsoid joint. The head of the metacarpal consists of medial and lateral condyles and is narrower on its dorsal surface than on its palmar surface; it fits into the concavity of the base of the proximal phalanx. The true collateral ligament attaches to a recess created by the junction of the shoulder and head. The collateral ligament is composed of the following 2 parts: (1) a dorsally placed cord portion and (2) a fan-shaped volar portion or accessory collateral ligament, which extends from the metacarpal to the sides of the volar plate. To accomplish flexion and extension at the MCP joint, the anterior and posterior parts of the capsule must be lax. When the joint is extended, the phalanges have considerable lateral play in abduction and adduction and, therefore, this joint avoids frequent injury; however, if the ligament is torn, dislocation occurs.

The bony anatomy of the CMC joint consists of the 5 metacarpal bases that articulate with the trapezoid, trapezium, capitate, and hamate (in that order) from the radial to the ulnar aspect of the hand. The CMC joint is a relatively fixed joint segment because of the articular congruity of the joint surfaces, with the metacarpal bases acting like concave receptacles to the distal carpal row, and because of the strong interosseous and extrinsic ligament complex. The palmar and dorsal ligaments are distinct, with the palmar ligaments being stronger. The scaphoid acts as a link between the proximal and distal carpal rows. The extensor and flexor tendons pass over this articular area but add no strength to the CMC joint because the bases of the metacarpals dislocate dorsally relative to the distal carpal row.

The MCP joint of the thumb has radial and ulnar collateral ligaments, which are loose when the joint is extended and tight when flexed. When the joint is extended, the proximal phalanx has the lateral play achieved by the action of the interosseous muscles. When the thumb is flexed and in a functional position, as in the case of many sports situations (eg, skiing, falls on a gloved hand), the ulnar collateral ligament is the structure at risk and can be ruptured (see also the eMedicine article Skier’s Thumb). The ulnar collateral ligament can then be displaced so that the adductor aponeurosis is interposed between the ruptured end of the ligament and its site of bony attachment.

The first CMC joint or the first metacarpotrapezoid joint is a very mobile saddle joint, with articular surfaces that are reciprocally concavoconvex. The most important soft-tissue support for this first CMC joint is the deep ulnar or anterior oblique ligament that runs from the volar beak of the metacarpal to the tubercle of the trapezium. This ligament can be ruptured, but it tends to be avulsed with a piece of bone (Bennett fracture-dislocation).

Sport-Specific Biomechanics

Dislocations of the interphalangeal joints of the hand probably occur most commonly in basketball and football. In basketball, the usual mechanisms of injury include being struck by the ball, catching a finger on the rim, or contact with another player. In football, the finger may be caught on a jersey, slapped against a helmet, or crushed between some combination of other players, their equipment, and the ground. Linemen and defensive players are at highest risk for hand injuries. In both of these sports, return to play almost always requires that the injury can be splinted stably to allow for a power grip.

Dislocations of the MCP and basilar CMC joints occur most commonly with falls on the outstretched hand (FOOSH injury) or the flexed supinated wrist. With this extension vector, the forces are transmitted up through the carpus.

Injuries and dislocations of the thumb, MCP joint, and the CMC basilar joint can commonly occur in falls, with the thumb in abduction. Examples of this type of injury include falls on the gloved hand in baseball or an abduction force applied to a flexed thumb while grasping an object, such as in skiing injuries when the pole impacts the proximal phalanx tearing the radial collateral ligament. This occurs when the wrist is extended at the time of the injury.

Clinical

History

As with any hand injury, the history of a patient with a suspected hand dislocation should begin with determining the patient's age; handedness; sex; and type of participation in sports, hobbies, or occupation, because these affect both the presentation of the injury and the goals of treatment. The patient most likely presents with a history of trauma leading to finger deformity. The clinician should inquire about whether other injuries took place to rule out the presence of any life-threatening injury.

Because the patient or others involved at the scene often reduce the dislocation, eliciting the mechanism of injury (eg, hyperextension, axial loading, torsion, radial/ulnar stress, direct blow) and the resultant deformity in the history is important. The patient is often not able to clearly describe the mechanism of injury, but the description of the deformity (volar vs dorsal) is valuable because the associated injuries and the appropriate treatment of these 2 injuries differ significantly. The exact location of pain can be helpful in localizing the injury, but this is more precisely defined by tenderness on physical examination.

Most injuries to the carpus occur when the patient falls on the outstretched hand, as might occur in any sport or accident. When the resultant vector is primarily one of ulnar deviation and intercarpal supination, ligamentous disruption and carpal dislocations tend to result. This mechanism can be observed in glove-side injuries in baseball fielders or hockey goalies.

Past medical and surgical history should focus on previous injuries to the hand and underlying conditions that may affect healing.

Physical

Areas that need to be assessed in the physical examination of a hand dislocation injury may include the following:

• Neurovascular status, both prereduction and postreduction
• Sensation - Best assessed with moving, 2-point discrimination (<5 mm) if any question exists
• Capillary refill
• Skin assessment
• Check for any breaks in the skin.
• The skin of the fingers is tightly stretched over the underlying structures and adherent to them, especially on the volar aspect and toward the fingertip. This makes the interphalangeal joints more prone to open dislocations than many other joints in the body.
• Any skin defect in the area of a joint must be presumed to be an open dislocation with direct communication of the joint with potentially contaminating bacterial flora. This flora can be destructive to articular cartilage and, therefore, may require intravenous (IV) antibiotics and consultation with a hand surgeon for irrigation and debridement. One should be suspicious of an open injury in a patient presenting with a laceration over a joint even without deformity, because the patient may have reduced the jammed finger before an examination.
• Deformity
• Hyperextension - Typical of dorsal PIP dislocations, indicating damage to the volar plate
• Angulation - Radial or ulnar, indicates damage to one or both of the collateral ligaments
• Rotation - Common in rotatory subluxation, which is a subtype of volar dislocation versus a separate class of injury (This deformity is best noted by looking at the nails. They should all lie in the same plane; the nail of an injured digit is rotated out of the plane of the others.)
• Displacement of the more distal phalanx - Volar in volar dislocations, dorsal or dorsolateral in dorsal dislocations (This finding may be obscured by swelling or may be subtle in partially reduced dislocations with entrapped soft tissue.)

The following items should be checked postreduction:

• The point of maximum tenderness may not be easy to determine but helps to define damaged structures.
• Lateral - Collateral ligaments (radial and/or ulnar)
• Volar - Volar plate
• Dorsal (base of middle phalanx) - Central slip
• Active range of motion (AROM) may be difficult to test if the patient is experiencing significant pain. Digital block (after neurologic examination) may be necessary to adequately determine ROM (see Image 29 or below).
  
  

  
  
  

  

  Digital block.

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  Digital block.

  
  

• The examiner must test full active extension of the PIP joint against resistance. In a PIP joint injury, inability to perform this motion with preservation of passive range of motion (PROM) is diagnostic of a rupture of the central slip of the extensor tendon. This injury must be splinted in extension to avoid development of a boutonniere deformity (see Images 14-17 or below).
  
  

  
  
  

  

  Boutonniere deformity.

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  Boutonniere deformity.

  
  

  
  
  

  

  Normal lateral band location, dorsal to the axis of rotation of the proximal interphalangeal joint.

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  Normal lateral band location, dorsal to the axis of rotation of the proximal interphalangeal joint.

  
  

  
  
  

  

  After central slip disruption, lateral bands migrate volar to the axis of rotation of the proximal interphalangeal joint.

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  After central slip disruption, lateral bands migrate volar to the axis of rotation of the proximal interphalangeal joint.

  
  

  
  
  

  

  Lateral view of relevant finger anatomy.

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  Lateral view of relevant finger anatomy.

  
  

• The joint should stay reduced throughout the ROM examination. Instability or redislocation, usually in extension, requires extension block splinting at an angle that preserves the reduction.
• If both AROM and PROM are reduced, this is consistent with entrapment of a soft-tissue structure (eg, volar plate, collateral ligament, flexor or extensor tendon) in the joint and persistent subluxation. This requires a further attempt at closed reduction. If this is unsuccessful, open reduction is urgently indicated.
• Stability to gentle passive stress should be checked.
• Hyperextension tests the volar plate.
• Ulnar deviation tests the radial collateral ligament.
• Radial deviation tests the ulnar collateral ligament. If the joint opens up 20° or more with minimal resistance, this is consistent with a complete collateral ligament tear.
• Avoid forceful passive testing for stability, because this can convert a partial tear to a complete one, and instability of any of these structures to passive stress is unlikely to change the management of an injury that is stable with AROM. Note: The one potential exception to this is complete rupture of the radial collateral ligament of the index finger PIP joint in a young, active patient. This injury is often surgically repaired, primarily because stability at this joint (required for a normal pinch grip) is more important than ROM.
• Dorsal deformities can be observed in both MCP-joint and CMC-joint dislocations. Because of swelling, these dislocations are sometimes hard to clinically identify. Bony prominences at the joints of maximum tenderness may be the most common physical findings.
• After reduction, stability of the MCP joint should be checked with radial and ulnar deviation with the joint in flexion to determine the functional stability of the radial and ulnar collateral ligaments. The MCP joint should be put through an ROM examination to determine the stability.
• In CMC dislocations after reduction, an ROM evaluation of the hand in dorsal and palmar flexion should be carried out to determine the intrinsic stability of the CMC joint.
• Physical examination testing specific to the thumb includes the following: In addition to AROM, testing of the thumb includes flexion of the MCP joint with radial and ulnar stress testing in extension and flexion with contralateral side-to-side comparison. Increased laxity with pain to palpation suggests an ulnar collateral ligament injury (see also the eMedicine article Gamekeeper's Thumb) (see Images 18-19 or below).
  

  

  Anteroposterior radiograph displaying a gamekeeper's fracture.

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  Anteroposterior radiograph displaying a gamekeeper's fracture.

  
  

  

  Lateral radiograph displaying a gamekeeper's fracture.

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  Lateral radiograph displaying a gamekeeper's fracture.

Entrapment of the ulnar collateral ligament in the aponeurosis (Stener lesion) prevents healing and may require surgical intervention (see Images 20-21 or below).

Ruptured ulnar collateral ligament.

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Ruptured ulnar collateral ligament.

Completed UCL repair using suture anchors for fixation (same patient as in Image 20).

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Completed UCL repair using suture anchors for fixation (same patient as in Image 20).

Causes

• Sports injuries (usually involving contact sports or a ball forcefully striking the tip of the finger)
• Occupational injuries
• Falls
• Traffic collisions

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