Michael P. Kefer
ANATOMY AND EXAMINATION
The intrinsic muscles of the hand originate and insert within the hand. These are the thenar and hypothenar muscle groups, adductor pollicis, the interossei, and the lumbricals.
Thenar muscles abduct, oppose, and flex the thumb and are innervated by the median nerve.
Hypothenar muscles abduct, oppose, and flex the little finger and are innervated by the ulnar nerve.
Adductor pollicis adducts the thumb and is innervated by the ulnar nerve.
Interosseous muscles adduct and abduct the fingers and are innervated by the ulnar nerve.
Lumbricals flex and extend the digits. The two radial lumbricals are innervated by the median nerve. The two ulnar lumbricals are innervated by the ulnar nerve.
Flexor digitorum superficialis inserts into the middle phalanges and flexes all the joints it crosses. Function is tested when the patient flexes the proximal inter-phalangeal (PIP) joint while the other fingers are held in extension.
Flexor digitorum profundus inserts at the base of the distal phalanges and flexes the distal interphalangeal (DIP) joint as well as all the other joints flexed by flexor digitorum superficialis. Function is tested when the patient flexes the DIP joint while the PIP and meta-carpal phalangeal (MCP) joints are held in extension.
Extensor digitorum extends all the digits. Function is tested by having the patient hold the hand in the “stop traffic” position. This also tests radial nerve motor function.
None of the intrinsic muscles of the hand are innervated by the radial nerve.
Figure 172-1 shows sensory innervation of the hand. This is best screened by testing two-point discrimination.
FIG. 172-1. The cutaneous nerve supply in the hand. DCU = dorsal branch of ulnar nerve; M = median; PCM = palmar branch of median nerve; R = radial; U = ulnar.
HAND INJURIES
Injuries requiring hand surgery consult are listed in Tables 172-1 and 172-2.
TABLE 172-1 Immediate Hand Surgery Consultation Guidelines
Vascular injury with signs of tissue ischemia or poorly controlled hemorrhage
Irreducible dislocations
Grossly contaminated wounds
Severe crush injury
Open fracture
Compartment syndrome
High pressure injection injury
Hand/finger amputation
TABLE 172-2 Delayed Hand Surgery Consultation Guidelines
Extensor/flexor tendon laceration (if not repaired in ED)
Flexor digitorum profundus rupture (closed)
Nerve injury (proximal to mid middle phalanx)
Closed fractures
Dislocations
Ligamentous injuries with instability
TENDON INJURY
Knowing the position of the hand at the time of injury predicts where, along its course, a tendon is injured.
Extensor tendon repair can often be performed by the emergency physician.
Flexor tendon repair should be performed by the hand surgeon.
It is common for the emergency care of tendon lacerations to consist of closing the skin and splinting until definitive repair by the hand surgeon.
MALLET FINGER
This injury results from rupture of the extensor tendon at the base of the distal phalanx.
On examination, the DIP joint is flexed at 40 degrees.
Splint the DIP joint in slight hyperextension and refer to a hand specialist.
BOUTONNIERÈ DEFORMITY
This results from injury at the dorsal surface of the PIP joint that disrupts the extensor hood.
Lateral bands of the extensor mechanism become flexors of the PIP joint and hyperextensors of the DIP joint.
Splint the PIP joint in extension and refer.
DISTAL INTERPHALANGEAL JOINT DISLOCATION
This is uncommon due to firm attachment of skin and fibrous tissue to underlying bone.
Dislocation is usually dorsal.
Reduction is performed under digital block anesthesia. The dislocated phalanx is distracted, slightly hyperextended, and then repositioned.
Splint the joint in full extension.
Inability to reduce the joint may be from an entrapped volar plate, profundus tendon, or avulsion fracture.
PROXIMAL INTERPHALANGEAL JOINT DISLOCATION
Dislocation is usually dorsal and results from rupture of the volar plate. Volar dislocation is rare.
Lateral dislocation results from rupture of the collateral ligaments.
Reduction is the same method as described above for DIP joint dislocation.
An irreducible joint from an entrapped volar plate may require surgical reduction.
Splint the joint in 30-degree flexion after reduction and refer.
METACARPOPHALANGEAL JOINT DISLOCATION
Dislocation is usually dorsal and requires surgical reduction due to volar plate entrapment.
Closed reduction is attempted with the wrist flexed and pressure applied to the proximal phalanx in a distal and volar direction.
Splint the joint in 70- to 90-degree flexion.
THUMB DISLOCATION
Interphalangeal (IP) and MCP joint dislocations usually involve volar plate rupture.
Reduction of the IP joint is as described above for DIP joint dislocation.
Reduction of the MCP joint is by flexing and abducting the metacarpal and applying pressure directed distally to the base of the proximal phalanx.
Apply a thumb spica splint after reduction.
THUMB ULNAR COLLATERAL LIGAMENT RUPTURE
Also known as gamekeeper’s or skier’s thumb, this results from forced radial abduction at the MCP joint.
This is the most critical of collateral ligament injuries due to affect on pincer function.
Ligament integrity is tested with the MCP joint in both full extension and 30-degree flexion. Complete rupture is diagnosed when abduction stress on the proximal phalanx causes more than 40 degrees of radial angulation relative to the metacarpal.
Splint in thumb spica and refer.
DISTAL PHALANX FRACTURES
Tuft fracture is the most common. If associated with subungual hematoma, drainage is recommended. Treat with a volar or hairpin splint.
Transverse fracture with displacement is always associated with nail bed laceration, which may require repair.
Avulsion fracture of the base results in a mallet finger (see above).
MIDDLE AND PROXIMAL PHALANX FRACTURES
Fracture of the base or neck that is nondisplaced and stable can be treated with buddy taping.
Transverse or spiral midshaft fracture or intra- articular fracture often requires surgical fixation. Place a gutter splint with flexion of the MCP joint at 90 degrees, the PIP joint at 20 degrees, and the DIP joint at 10 degrees and refer.
METACARPAL FRACTURES
Fracture of the fourth or fifth metacarpal neck, often called a boxer’s fracture, is the most common. Angulation more than 20 degrees in the ring finger, 40 degrees in the fifth finger, or 15 degrees in the middle or index finger should be reduced.
Treat with a gutter splint with the wrist extended 20 degrees and the MCP joint flexed 90 degrees and refer.
First metacarpal base fractures with intra-articular involvement (Bennett and Rolando fractures) should be immobilized in a thumb spica splint and referred for surgical repair.
COMPARTMENT SYNDROME
Crush injury to the hand is especially at risk for compartment syndrome, which is a surgical emergency.
The patient will complain of pain that is out of proportion to examination findings.
Examination reveals the hand in a resting position is extended at the MCP joint and slightly flexed at the PIP joint. There is pain with passive stretch of the involved compartment and tense edema.
HIGH PRESSURE INJECTION INJURY
This injury, which is a surgical emergency, occurs when substances in a high-pressure device, such as grease, paint, or hydraulic fluid, are injected into the hand.
Oil-based paint causes the most severe tissue reaction and can result in ischemia, leading to amputation.
Radiographs of the hand and forearm are indicated to evaluate for radiopaque substances and subcutaneous air.
WRIST INJURIES
SCAPHOLUNATE DISSOCIATION
This injury presents with wrist pain at the scapholunate joint.
Posteroanterior (PA) radiograph demonstrates a space more than 3 mm between the scaphoid and lunate and the cortical ring sign of the subluxed scaphoid.
Treat this injury with a radial gutter splint and refer for ligament repair.
LUNATE AND PERILUNATE DISLOCATION
In both injuries, a lateral wrist radiograph reveals the dislocation, as the normal alignment of the radius- lunate-capitate (the “3 C’s” sign) is lost.
With a lunate dislocation, the lunate dislocates volar to the radius, but the remainder of the carpus aligns with the radius. On PA radiograph, the lunate has a triangular shape, referred to as the “piece of pie” sign. Lateral radiograph reveals the lunate to be displaced and tilted volar, which has been described as the “spilled teacup sign.”
With a perilunate dislocation, the lunate remains aligned with the radius, but the capitate and the remainder of the carpus are dislocated, usually dorsal to the lunate.
Emergent hand surgery consult for closed reduction or surgical repair is indicated.
CARPAL BONE FRACTURES
Management is summarized in Table 172-3.
The scaphoid is the most common carpal fractured.
Fracture of the scaphoid, lunate, or capitate can cause avascular necrosis of the bone.
Scaphoid and lunate fractures are often not detected on plain wrist radiograph, so diagnosis and treatment should be based on examination findings alone.
TABLE 172-3 Summary of Carpal Bone Fractures and ED Management
COLLES, SMITH, AND BARTON FRACTURES
These fractures involve the distal radius at the meta-physis (Table 172-4).
Most of these fractures can be treated with closed reduction and a sugar tong splint.
TABLE 172-4 Radiographic Appearance of Distal Radius Fractures
RADIAL STYLOID FRACTURE
Radial styloid fracture can produce carpal instability with scapholunate dissociation as major carpal ligaments insert here.
Splint the wrist in mild flexion and ulnar deviation and refer.
ULNAR STYLOID FRACTURE
Ulnar styloid fracture may result in radial ulnar joint instability.
Place an ulnar gutter splint with the wrist in neutral and slight ulnar deviation and refer.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 265, “Injuries to the Hand and Digits,” by Moira Davenport, and Dean G. Sotereanos, and Chapter 266, “Wrist Injuries,” by Robert Escarza, Maurice F. Loeffel III, and Dennis T. Uehara.