Proximal Interphalangeal Joint Dislocation

Last updated on December 31, 2020

Proximal interphalangeal joint (PIPJ) dislocation is one of the most common hand injuries. Dislocation refers to displacement in which the two articular surfaces are no longer in contact, in contrast to subluxation, in which there is some contact (may be referred to as complete versus simple dislocation in some texts). Studies have shown that dislocation most commonly occurs at the small finger, with decreasing frequency with the more radial fingers.

Case example

A 50-year-old male presented to the emergency department with a left index finger deformity consistent with a PIPJ dorsal dislocation and volar laceration after a mechanical fall that occurred after he tripped while walking and looking at his cell phone at the same time. He reported an inability to flex or extend his left index finger associated with slight numbness distal to the injury. Finger radiograph demonstrated an acute dorsal dislocation of the PIPJ with concern for a nondisplaced fracture at the base of the middle phalanx.

All images have been de-identified and are shared with the informed consent of the patient.

Anatomy

The PIPJ refers to the articulation between the head of the proximal phalanx and the base of the middle phalanx [1].

Ligaments

Collateral ligament complex: This complex is composed of the proper and accessory collateral ligaments. The proper collateral ligaments arise from the dorsal concave areas on the radial and ulnar surfaces of the proximal phalangeal head. The accessory collateral ligaments arise from the volar portion of the proper collateral ligaments and insert onto the volar plate. Together, collateral ligaments serve to stabilize against varus and valgus stress during flexion.
Volar plate: The volar plate is a stout fibrous structure that inserts onto the volar side of the middle phalanx. It serves to resist hyperextension at the PIPJ. Its thickness has been found to differ among the digits with the ulnar-sided digits having thinner, and consequently weaker, volar plates.
Central slip of the extensor mechanism: The central slip inserts onto the dorsal portion of the median ridge of the middle phalanx.

Muscles

Flexor digitorum superficialis (FDS): The FDS is an extrinsic flexor muscle in the anterior forearm that inserts onto the volar shaft of the middle phalanx.
Flexor digitorum profundus (FDP): The FDS is an extrinsic flexor muscle in the anterior forearm that inserts onto the volar shaft of the distal phalanx.
Lumbricals: The four lumbricals originate from the FDS tendon and insert onto the extensor expansions to flex the metacarpophalangeal joints and extend the interphalangeal joints.
Dorsal interossei: The dorsal interossei muscles abduct the index, middle, and ring fingers, as well as extend the metacarpophalangeal and interphalangeal joints

Blood supply

The PIPJ is supplied by branches of the proper palmar digital arteries.

Nerve supply

The palmar digital nerves supply the volar PIPJ with branches innervating the proximal phalanx, tendon sheath, capsule, vincula, and collateral ligaments. The PIPJ also has dorsal innervation with branches from the superficial radial nerve from the index and middle fingers and the ulnar nerve for the ring and small fingers.

Movements of proximal interphalangeal joints

The PIPJ was originally described as a hinge model, but this has been shown to be inaccurate due to the incongruities between the proximal and middle phalanx. Such incongruities allow abduction, adduction, axial rotation, and sagittal rotation.

Mechanism of injury

Nearly all of PIPJ dislocations are dorsal; volar and lateral dislocations are significantly less common. Dorsal dislocations occur as a result of forced hyperextension, axial load, and radial or ulnar deviation. They are characterized by volar plate rupture at its distal attachment and a split between the proper and accessory collateral ligaments. Volar dislocations occur with or without torsion. If there is no torsion, direct volar translation of the middle phalanx causes rupture of the central slip, volar plate, and one collateral ligament. If there is torsion, in which one condyle of the proximal phalanx slides past the central slip, a tear is formed between the intact central slip and lateral band with rotation of the middle phalanx around the collateral ligament. Lateral dislocations result from direct radial or ulnar stress on the PIPJ with axial load, causing the ipsilateral collateral ligament to avulse. Many lateral dislocations also involve a dorsal component and may more accurately described as dorso-lateral.

Symptoms

PIPJ dislocation presents with pain, swelling, ecchymosis, and deformity at the joint with an inability to flex or extend the affected digit.

Physical examination

The examination should include inspection for skin compromise, deformity, swelling, tenderness, malrotation, or angulation of the affected digit (Figure 1). The presence of skin puckering suggests the interposition of soft tissues within the joint that may prevent successful reduction. The patient may also report diminished sensation due to traction neuropraxia secondary to stretching of the adjacent digital nerves.

Figure 1. This patient demonstrated deformity at the dorsal aspect of the left index PIPJ with the DIPJ held in flexion and ulnar angulation. He also had a laceration along the volar aspect of the PIPJ. Image by Catherine Ly, licensed under CC BY-NC-SA 4.0).

Radiology

Conventional radiographs of the affected digit should be obtained with three views (anteroposterior, lateral, and oblique). Dislocation is indicated by loss of the normal joint space and loss of contact between the articular surfaces (Figure 2). Lateral radiographs are often the best view for visualization of the overlapping of the middle phalanx base and proximal phalanx head.

Figure 2. This patient’s radiographs demonstrated dorsal dislocation of the left index finger middle phalanx onto the proximal phalanx. This is most clearly seen on the lateral and oblique views. Image by Catherine Ly, licensed under CC BY-NC-SA 4.0).

Treatment

PIPJ dislocations should be reduced as soon as possible to avoid sequelae of chronic dislocation [2]. While not specifically studied, there is probably a correlation between time to reduction and stiffness, as scarring and cartilage degeneration are proportional to the duration of dislocation. A patient should never be discharged with a dislocated joint in the finger. Closed reduction should be attempted in the emergency department. Open wounds should also be irrigated extensively and repaired if necessary. A course of antibiotics should be provided if there is concern for an open dislocation or fracture. Prior to reduction attempt, local anesthesia should be achieved using nerve and field blocks. If the patient is not adequately blocked, and has pain during the reduction maneuver, they may be able to overpower the treating physician and prevent reduction. Reduction of a dorsal dislocation is performed by hyperextending the middle phalanx with subsequent volar force; traction should not be applied (video). The key to the reduction maneuver is to “push” the base of the middle phalanx over the distal end of the proximal phalanx instead of applying traction (Figure 3). Volar dislocations are reduced similarly, by pushing the base of the middle phalanx over the end of the proximal phalanx while the metacarpal and PIP joints are in 90 degrees of flexion. Rotatory dislocation reductions require additional rotatory motion.

Figure 3. This video depicts successful reduction of a dorsal PIPJ dislocation with hyperextension of and volar force on the middle phalanx without longitudinal traction. Video by Catherine Ly, licensed under CC BY-NC-SA 4.0).

If the initial reduction attempt is unsuccessful (as demonstrated on post-reduction radiographs), an additional attempt at closed reduction may be performed (the patient is still anesthetized). Repeated reduction attempts should not be performed to limit risks of soft tissue or bony injury from the reduction attempts themselves.

It is important to perform a repeat examination after reduction to determine joint stability and ligament integrity. The ability to achieve active full range of motion indicates a stable joint. The collateral ligaments are assessed by applying lateral stress when the joint is in full extension and in 30 degrees of flexion. Injury can subsequently be classified into three grades: I, pain without laxity; II, laxity with a firm endpoint and a stable arc of motion; and III, gross instability without an endpoint. Passive hyperextension is performed to assess the competency of the volar plate. The Elson’s test is used to assess central slip stability; the patient’s PIP is placed in 90 degrees of flexion and then the patient is asked to extend against resistance on the middle phalanx. If the central slip is injured, the normally loose lateral bands will be held taut and the DIPJ will be in near hyperextension rather than in a floppy, flexed position.

Physical examination is also important to assess the stability of the joint as a relation to the degree of flexion. As extension is performed passively by the examiner, the stability of the joint can be evaluated, and the point at which repeat dislocation is imminent can be felt and avoided. The joint should be splinted with a dorsal blocking splint in the position (degrees of flexion) that prevents repeat dislocation. Usually, this will be close to 0 degrees of flexion – immobilization in excessive degrees of flexion should be avoided to prevent a flexion contracture – but each joint should be assessed individually.

Post-reduction radiographs (specifically, true PA and lateral views of the finger) should be performed to confirm joint alignment (Figure 4). A reduction can be confirmed if a normal joint space is visible on the PA and lateral views, and cortical surfaces are parallel on both views. The axes of the bones should intersect at the mid-point between the condyles on the PA view, and at the axis of the joint on the lateral view (Figure 5).

Figure 4. *Post-reduction radiographs demonstrating successful reduction of dorsal PIPJ dislocation.* Note the normal joint space and parallel joint surfaces on all of the views, .Image by Catherine Ly, licensed under CC BY-NC-SA 4.0).

Figure 5. Demonstrating that the projected axes of the proximal and middle phalanges intersect at the PIP joint axis on the PA and later views – indicating that the reduction is complete. Image by Catherine Ly, licensed under CC BY-NC-SA 4.0).

Surgical intervention is required if reduction attempts are not successful or the joint is unstable as a result of a concomitant fracture. Surgery is not urgent but should be performed at the earliest time at which anesthesia can be safely administered. The structures that could be responsible for unsuccessful closed reduction (creating an “irreducible dislocation”) include volar plate entrapment in closed dorsal dislocations, a dislocated FDP tendon in open dislocations, or lateral band interposition in lateral dislocations [3]. Open reduction of dorsal and dorso-lateral dislocations may be performed using a volar Bruner incision that allows for retraction of the flexor tendons for exposure of the volar plate and/or collateral ligament or a midlateral skin incision through which the transverse retinacular ligament is excised longitudinally for joint exposure. Volar dislocations may be treated with a dorsal approach with a longitudinal midline or slightly curved incision with preservation of the dorsal veins. However, if there is no extensor tendon disruption, a lateral approach may be preferable. Simultaneous dorsal and volar incisions should be avoided because of excessive swelling that can occur.

Early motion with hand therapy is critical to prevent stiffness. Even short periods of immobilization of the PIPJ may lead to permanent loss of function. Dorsal blocking splint with full active and passive flexion is the recommended post-reduction treatment. The physician should specify to the hand therapist the degrees of flexion that the dorsal blocking splint should be constructed with, based on the instability of the joint assessed by the physician during the immediate post-reduction period.

Consult Summary/Pearls

PIPJ dislocation is a common injury that should be suspected with any traumatic injury resulting in loss of function.
Radiographs are essential for accurate diagnosis of dislocation and to determine if there are any associated fractures.
Dorsal dislocation is the most common type of PIPJ dislocation.
Reduction should be attempted as soon as possible under adequate anesthesia with hyperextension of the base of the middle phalanx combined with palmar force.
Repeat radiographs should be obtained, and assessment of joint stability and ligament competency should be assessed after reduction attempts.
Unsuccessful reduction attempts should be limited, and operative relocation should be performed in irreducible cases.
Extension block splinting should be used to prevent repeat dislocation, but prolonged immobilization after reduction should be avoided to prevent stiffness.

References

Proximal Interphalangeal Joint Dislocation

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