What is the treatment for a patient with a reduced posterior shoulder dislocation who now experiences numbness in the small finger?

Treatment of Reduced Posterior Shoulder Dislocation with Small Finger Numbness

The small finger numbness indicates ulnar nerve injury, which requires immediate neurovascular documentation, orthopedic referral within 24-48 hours, and close monitoring with physiotherapy follow-up, as nerve injuries following shoulder dislocation can persist for months and require specialized management. 1

Immediate Post-Reduction Management

Neurovascular Assessment

• Document the ulnar nerve deficit thoroughly, including the exact distribution of numbness (small finger and ulnar half of ring finger), any motor weakness (finger abduction/adduction, grip strength), and compare to the contralateral side 1
• The ulnar nerve injury may have occurred from the initial dislocation mechanism, during the reduction maneuver, or from associated fractures—all possibilities must be considered 1
• Perform a complete neurovascular exam including axillary nerve function (deltoid strength and sensation over the lateral shoulder), as multiple nerve injuries can coexist 1

Mandatory Post-Reduction Imaging

• Obtain post-reduction radiographs immediately to confirm successful reduction and identify any fractures that were obscured by the dislocation 2, 3
• The radiographic series must include AP views in internal and external rotation PLUS an axillary or scapula-Y view, as posterior dislocations are notoriously difficult to assess on AP views alone 2, 3
• If symptoms persist or radiographs are equivocal, obtain a CT scan to better characterize any reverse Hill-Sachs defect (anteromedial humeral head compression fracture) or glenoid fractures that could be compressing the nerve 3, 4

Specific Management of Ulnar Nerve Injury

Initial Treatment Phase

• Immobilize the shoulder in a position of comfort (typically neutral rotation with sling support) to prevent further nerve traction 1
• Avoid positions that place tension on the ulnar nerve, particularly extreme internal rotation or adduction 1
• Arrange urgent orthopedic consultation within 24-48 hours for evaluation of the nerve injury and determination of whether surgical exploration is needed 1

Monitoring and Follow-Up

• Document serial neurovascular exams at each visit to track progression or deterioration of the nerve deficit 1
• Most nerve injuries following shoulder dislocation are neurapraxias (stretch injuries) that recover spontaneously over 3-6 months, but this requires close monitoring 1
• If no improvement occurs within 3 months, electromyography (EMG) and nerve conduction studies are indicated to assess the severity and prognosis of the nerve injury 1

Advanced Imaging Considerations

MRI Evaluation

• Consider MRI without contrast in the subacute period (1-2 weeks post-reduction) to evaluate for associated soft tissue injuries that are common in posterior dislocations, particularly rotator cuff tears in older patients 2, 3
• MRI is superior to CT for assessing rotator cuff pathology, capsular injuries, and labral tears that may require surgical intervention 5, 2
• MRI can also identify any soft tissue masses or hematomas that might be compressing the ulnar nerve 2

CT Indications

• CT is superior to radiography for identifying the reverse Hill-Sachs defect and characterizing complex fracture patterns that may require surgical fixation 3, 6
• If there is concern for vascular injury (diminished pulses, expanding hematoma), obtain CT angiography emergently to rule out axillary artery injury 2, 3

Rehabilitation Protocol

Early Phase (0-6 Weeks)

• Initiate active finger motion exercises immediately to prevent stiffness, including full range of motion of all digits despite the numbness 5
• Passive shoulder pendulum exercises can begin once pain allows, typically within the first week 5
• Avoid aggressive shoulder range of motion until orthopedic clearance, as posterior dislocations have different stability considerations than anterior dislocations 6

Recovery Phase (6 Weeks to 3 Months)

• Progress to active-assisted and then active shoulder range of motion under physiotherapy guidance 1
• Continue physiotherapy specifically targeting nerve recovery, including desensitization techniques and motor re-education if motor deficits are present 1
• Monitor for signs of nerve recovery including return of sensation (typically progresses from proximal to distal) and improvement in motor function 1

Critical Pitfalls to Avoid

Diagnostic Errors

• Never rely on AP radiographs alone for posterior dislocations, as over 60% are initially misdiagnosed without proper orthogonal views 2, 3, 7, 8
• Do not dismiss persistent symptoms as "normal post-reduction pain"—persistent neurological deficits require investigation 1, 4
• Failure to document the initial neurovascular exam makes it impossible to determine if nerve injury occurred during reduction versus was present initially 1

Treatment Delays

• Do not delay orthopedic referral when nerve injury is present, as some nerve injuries require early surgical exploration if there is evidence of nerve laceration or entrapment 1
• Overlooking associated rotator cuff tears, which are common in older patients with posterior dislocations, can lead to persistent weakness and poor functional outcomes 3, 6
• Missing a locked posterior dislocation (where the humeral head remains subluxed posteriorly despite appearing reduced on AP views) leads to chronic pain and loss of motion 4, 6

Long-Term Management

• If no improvement occurs by 3 months, the patient requires EMG/nerve conduction studies and possible surgical consultation for nerve exploration or tendon transfers 1
• Patients with persistent nerve deficits may require occupational therapy for adaptive strategies and splinting to prevent contractures 1