Carpal ligament injuries

Carpal ligament injuries are typically caused by forceful wrist hyperextension (e.g., fall on an outstretched hand). These injuries follow a progressive pattern; the scapholunate ligament is affected first and causes scapholunate dissociation. More severe trauma can disrupt the lunocapitate, lunotriquetral, and lunoradial ligaments, causing perilunate, triquetral, or lunate dislocations. Symptoms of carpal ligament injuries include wrist swelling and pain, restricted range of motion, and point tenderness at the dorsal scapholunate interval. Symptoms of median nerve injury may also occur. Diagnosis is based on features of carpal malalignment on imaging. Scapholunate dissociation is managed with immobilization and orthopedics follow-up within one week. Carpal dislocations require emergency reduction and stabilization followed by definitive treatment with open reduction and internal fixation. Carpal ligament injuries can result in carpal instability, particularly if the ligamentous support is significantly compromised. Other complications include chronic carpal instability, degenerative arthritis, dorsal intercalated segment instability (DISI), and volar intercalated segment instability (VISI).

• Trauma (most common)
  • Typically caused by sudden impact to the wrist in hyperextension (e.g., fall on an outstretched hand) ^[1][2][3]
  • Can also be caused by repetitive strain injury ^[4]
• Other possible underlying causes (rare) ^[4]
  • Infectious or inflammatory arthritis
  • Congenital anomalies

• Carpal instability: impaired ability to maintain normal anatomical alignment of carpal bones under physiological stress ^[4]
• Progressive perilunate instability: results from sequential injury of ligaments that surround the lunate bone (e.g., scapholunate ligament, lunotriquetral ligament), which is the common process underlying the Mayfield classification of carpal ligament injuries (i.e., scapholunate dissociation, perilunate dislocation, midcarpal dislocation, and lunate dislocation)
• Intercalated segment instability ^[2][3][5]
  • Intercalated segment of the wrist: a term used to describe the proximal carpal row (i.e., scaphoid, lunate, triquetrum, and pisiform)
    • Located between the distal carpal row and the distal radius and ulna but functions independently from them
    • Has no direct tendinous insertions and relies on carpal ligaments for stability and coordinated motion
  • Carpal ligament injuries disrupting the alignment of the intercalated segment lead to specific instability patterns (i.e., DISI or VISI).

• Wrist swelling and pain ^[2][6][7]
• Restricted range of motion ^[7]
• Point tenderness at the dorsal scapholunate interval ^[2][6]
• Visible deformity (in severe perilunate dislocations and lunate dislocations) ^[6]
• Signs of median nerve injury; (e.g., acute carpal tunnel syndrome): more common in perilunate and lunate dislocations than in isolated scapholunate dissociation ^[1][2]

Approach ^[3][6][8]

• Perform a neurovascular examination to assess digital capillary refill and identify median nerve palsy, ulnar nerve palsy, or radial nerve palsy
• Perform the Watson test to identify laxity of the scapholunate ligament. ^[2]
• Obtain imaging in all patients.
• Specific wrist fractures : Consider carpal ligament injuries even if typical fracture findings are not seen on x-ray. ^[1][6]
• Use the Mayfield classification to classify perilunate injuries as they occur on a spectrum. ^[1][2][3]
  • A system based on the four stages of progressive perilunate instability.
  • The wrist arcs may be affected in any of the stages.

Imaging ^[3][6][8]

• X-ray wrist: Obtain PA and lateral views in all patients to identify abnormal widening of the carpal joints, assess carpal bone alignment, and identify any concomitant fractures.
• Stress x-rays (i.e., clenched fist, ulnar deviation): Obtain if standard x-rays are normal but clinical suspicion is high.
• Advanced imaging ^[2][7]
  • MRI, MRA, and CT may be performed if x-rays are inconclusive.
  • For chronic injuries, MRA and CT are the preferred modalities to assess for cartilage defects.
• Arthroscopy: gold standard for a definitive diagnosis if MRI and CT are inconclusive
• Findings: See “Scapholunate dissociation,” “Perilunate dislocation,” “Midcarpal dislocation,” and “Lunate dislocation.”

Scapholunate dissociation ^[3][9]

• Definition: disruption of the scapholunate and radioscaphocapitate ligaments
• Mayfield classification: stage I
• Imaging findings
  • Terry Thomas sign: > 3 mm widening of the scapholunate joint on PA view ^[6][8]
  • Signet ring sign: ring-like shadow appearance of the scaphoid tubercle cortex on x-ray due to rotary subluxation of the scaphoid ^[6][8]

Perilunate dislocation ^[3][9]

• Definition: disruption of the lunocapitate ligament
• Mayfield classification: stage II
• Imaging findings ^[6]
  • Capitate appears dislocated and dorsally displaced on lateral view.
  • Lunate remains articulated and aligned with the radius.
• Subtypes ^[1][6]
  • Transscaphoid perilunate fracture-dislocation: perilunate dislocation with an associated scaphoid fracture
  • Other associated fractures: radial styloid or capitate

Midcarpal dislocation ^[3][9]

• Definition: disruption of the lunocapitate, lunotriquetral, and scaphotriquetral ligaments
• Mayfield classification: stage III
• Imaging findings
  • Perilunate dislocation with superimposed triquetrum and lunate or hamate on lateral view ^[6]
  • Possible dorsal displacement of the triquetrum or visible triquetral avulsion fracture

Lunate dislocation ^[3][9]

• Definition: disruption of all perilunate ligaments, causing palmar lunate dislocation into the carpal tunnel
• Mayfield classification: stage IV
• Imaging findings
  • Piece of pie sign: triangular shape on PA view due to volar rotation of the lunate ^[3][6]
  • Spilled teacup sign: The lunate appears tipped forward on lateral view due to volar rotation. ^[3][6]
  • Lateral view: The capitate has migrated proximally behind the lunate and is in contact with the radius. ^[6]

Initial management ^[1][6]

• All carpal ligament injuries
  • Provide acute pain management as needed.
  • Immobilize the wrist (see “Upper extremity splints”).
  • Consult orthopedics or hand surgeon if there is a concomitant fracture with reasons to consult orthopedics for fractures.
• Scapholunate dissociation without nerve injury
  • Immobilize with radial gutter splint or volar-dorsal splint. ^[10]
  • Arrange outpatient orthopedics or hand surgeon follow-up within 1 week to be evaluated for surgical repair ^[6][10][11]
• Perilunate dislocation, midcarpal dislocation, and lunate dislocation
  • Consult orthopedics or hand surgeon for urgent reduction and immobilization with a long arm splint. ^[6][10]
  • Treatment options include:
    • Closed reduction and splinting for some reducible dislocations
    • Surgical repair and fixation for all open dislocations and most unstable or irreducible dislocations
• Neurovascular injury
  • Consult orthopedics for urgent reduction and immobilization.
  • After reduction and stabilization, perform serial examinations to monitor for acute carpal tunnel syndrome. ^[1]

Surgery ^[1][11][12]

• Arthroscopic or minimally invasive techniques
  • Selected scapholunate dissocations ^[13]
  • Early perilunate dislocations (i.e., before the onset of fibrosis) with minimal carpal instability
• Open reduction and internal fixation
  • Perilunate dislocations that are displaced, irreducible, or have measurable carpal instability
  • Midcarpal dislocations
  • Lunate dislocations
  • Carpal fracture-dislocations (e.g., transscaphoid perilunate dislocation) ^[14]

General complications

• Chronic carpal instability
• Degenerative arthritis

Dorsal intercalated segment instability (DISI) ^[2][3]

• Definition: carpal instability caused by scapholunate ligament disruption, where the scaphoid flexes forward and the lunate is pulled dorsally by the intact lunotriquetral ligament. ^[2][3][11]
• Diagnosis
  • Abnormal scapholunate angle on x-ray due to excessive scaphoid flexion and lunate (and often triquetrum) extension ^[3]
  • A scapholunate gap > 4mm and lunate extension > 10° suggest DISI. ^[15]
• Management ^[3]
  • Outpatient orthopedic referral for surgical repair is appropriate for most cases.
  • Urgent evaluation is indicated if there is instability post-trauma, with dislocation and/or neurovascular compromise.

In DISI, scapholunate ligament disruption leads to dorsal rotation of the lunate and excessive volar rotation of the scaphoid. ^[2][3]

Volar intercalated segment instability (VISI) ^[2][3][7]

• Definition: abnormal volar rotation of the lunate due to lunotriquetral ligament injury, causing the lunate to follow the scaphoid into flexion while the scapholunate ligament remains intact ^[7][12]
• Diagnosis
  • Excessive volar rotation of the lunate relative to the capitate on x-ray ^[3]
  • A scapholunate angle < 30° in the presence of lunotriquetral diastasis supports a diagnosis of VISI. ^[15]
• Management ^[3][7]
  • Outpatient orthopedic referral for surgical repair is appropriate for most cases.
  • Urgent evaluation is indicated if there is instability post-trauma, with dislocation and/or neurovascular compromise.

In VISI, lunotriquetral ligament disruption results in excessive volar flexion of the lunate relative to the capitate on x-ray. ^[7]

We list the most important complications. The selection is not exhaustive.