What are the potential causes and treatment options for an adult patient with a history of repetitive strain or injury to the hand, who is experiencing finger locking up, possibly related to underlying conditions such as diabetes or peripheral neuropathy?

Finger Locking: Diagnosis and Management

Most Likely Diagnosis

The most common cause of finger locking in adults with repetitive hand strain is trigger finger (stenosing tenosynovitis), caused by inflammation and narrowing of the A1 pulley, which is more prevalent in diabetic patients and women in their 50s-60s. 1

Differential Diagnosis to Consider

When evaluating a finger that locks, you must differentiate between several distinct conditions:

• Trigger finger: Painful clicking, catching, or locking during flexion/extension movements, typically affecting the flexor tendons at the A1 pulley level 1, 2
• Locked metacarpophalangeal (MCP) joint: Inability to fully extend the MCP joint with lateral displacement of the extensor tendon, typically in men over 50 with history of repetitive manual work 3, 4
• MCP joint arthritis: Crepitus and stiffness, may include degenerative changes visible on radiographs 2
• Extensor tendon subluxation or dislocation: Visible displacement of extensor tendon over MCP joint 2

The key distinguishing feature is that trigger finger causes locking during active finger motion (flexion/extension), while locked MCP joint presents as fixed inability to extend the MCP joint with the extensor tendon visibly displaced laterally. 3, 4

Initial Diagnostic Workup

Obtain at least 3-view radiographs of the affected digit to exclude:

• Fractures or dislocations 5
• Abnormal metacarpal head shape 3
• Free intra-articular bodies 3
• Degenerative joint changes 3
• Sesamoid bone abnormalities 3

MRI with dedicated neurography sequences should be obtained if there is concern for tendon avulsion, nerve injury, or when diagnosis remains unclear after radiographs. 5, 6

Special Considerations for Diabetic Patients

All diabetic patients should be screened for distal symmetric polyneuropathy at diagnosis and annually thereafter, as diabetic neuropathy can mask pain from ischemia or infection and complicate the clinical picture. 5

Key examination findings in diabetics:

• Test temperature or pinprick sensation (small fiber function) 5
• Test vibration with 128-Hz tuning fork (large fiber function) 5
• Perform 10-g monofilament testing to identify feet at risk 5
• Assess for signs of peripheral arterial disease, as diabetics are prone to access-induced ischemia 5

Treatment Algorithm

For Trigger Finger (Most Common)

Initial conservative management should be attempted before surgical intervention:

1. Splinting: Immobilize the affected finger in extension, particularly effective for mild symptoms 1, 7

2. Corticosteroid injection: Highly effective for moderate symptoms, can be performed in office 1

3. Physical therapy modalities:

   • External shock wave therapy (ESWT) reduces pain and trigger severity while improving function 7
   • Ultrasound therapy (UST) helps prevent symptom recurrence 7

4. Surgical release: Reserved for refractory cases or severe locking that fails conservative treatment 1

For Locked MCP Joint

Attempt gentle manipulation under regional nerve block first, as this is successful in approximately 30% of cases: 3, 4

• Distend the joint capsule with intra-articular local anesthetic injection 4
• Perform gentle manipulation to restore joint mobility 4
• If manipulation fails, surgical intervention is necessary 4

For Suspected Tendon Laceration or Avulsion

Immediate surgical exploration is indicated for complete tendon lacerations with loss of function, as early intervention (within days to weeks) is critical for optimal outcomes. 8, 9

Post-operative protocol:

• Rigid immobilization for 3-6 weeks 6
• Begin active finger motion exercises immediately after immobilization to prevent stiffness 6
• Home exercise programs through complete range of motion 6

Red Flags Requiring Urgent Evaluation

Seek immediate specialist referral if:

• Fingertip necrosis or signs of ischemia (pale/blue/cold hand), especially in diabetics with arteriovenous fistulas 5
• Complete loss of finger function suggesting nerve or tendon laceration 9
• Unremitting pain during follow-up, which may indicate inadequate fixation, pulley injury, or tendon re-rupture 6
• Signs of infection (cellulitis, osteomyelitis) in diabetic patients, as this increases tissue demand and accelerates ischemia 5
• Acute neuropathy with muscle pain and weakness within hours of symptom onset 5

Common Pitfalls to Avoid

• Do not confuse trigger finger with locked MCP joint: Trigger finger locks during motion; locked MCP joint is fixed in flexion with visible extensor tendon displacement 3, 2
• Do not attribute all finger symptoms to neuropathy in diabetics: Always assess vascular status and exclude structural pathology with imaging 5
• Do not delay imaging if clinical diagnosis is uncertain: MRI definitively identifies tendon injuries, nerve damage, and joint pathology 5, 6
• Do not ignore mild ischemic symptoms in diabetics: Early intervention prevents progression to gangrene and amputation 5