Courtesy: Dr Jennifer Kargel MD, Director of Hand Surgery, Chief of Plastic Surgery at VA Dallas, Assistant Professor, UT SouthWestern, Dallas, Texas, USA

 

“Zebras” in Hand Surgery

Introduction

In clinical medicine, the term “zebras” refers to rare or uncommon diagnoses, while “horses” represent common conditions encountered in routine practice. In hand surgery, most patients present with familiar problems such as fractures, tendinitis, nerve compression syndromes, or arthritis. However, atypical presentations may occasionally represent uncommon disorders that require a high index of suspicion.

This review summarizes several important “zebra” conditions in hand surgery, focusing on their clinical presentation, diagnosis, differential diagnosis, and management.

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Parsonage-Turner Syndrome (Neuralgic Amyotrophy)

Overview

Parsonage-Turner syndrome is a rare brachial plexus neuropathy characterized by sudden severe pain followed by weakness and muscle atrophy.

It may be:

• Idiopathic (likely immune-mediated)
• Hereditary (autosomal dominant)

Incidence is approximately 2–3 per 100,000 population.

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Etiology and Triggers

Common triggers include:

• Viral infections
• Immunization
• Surgery
• Trauma
• Exercise
• Peripartum state

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Clinical Presentation

Initial Phase

Patients typically develop:

• Acute severe neuropathic pain
• Shoulder and neck pain
• Pain lasting days to weeks

Subsequent Phase

Pain is followed by:

• Weakness
• Muscle wasting
• Sensory disturbances

Nerve involvement is usually patchy rather than dermatomal.

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Commonly Involved Nerves

Frequently affected nerves include:

• Upper brachial plexus
• Long thoracic nerve
• Axillary nerve
• Musculocutaneous nerve

Median and ulnar nerve involvement is uncommon.

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Differential Diagnosis

Conditions that may mimic Parsonage-Turner syndrome include:

• Cervical radiculopathy
• Rotator cuff pathology
• Thoracic outlet syndrome
• Brachial plexus injury
• Pancoast tumor

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Investigations

Electromyography (EMG)

Typical findings include:

• Fibrillations after approximately 1 month
• Reinnervation changes after 3–4 months

Chest X-ray

Obtained to exclude apical lung tumors such as Pancoast tumor.

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Treatment

There is no definitive treatment.

Management includes:

• Physiotherapy
• Neuropathic pain medications (e.g., gabapentin)
• Possible corticosteroids in early stages

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Prognosis

• Recovery may take months to years
• Average recovery approximately 2 years
• Around 30% may have residual symptoms

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Lateral Epicondylitis (Tennis Elbow)

Overview

Lateral epicondylitis is a common condition involving degenerative changes of the extensor tendon origin.

The most commonly involved tendon is:

• Extensor Carpi Radialis Brevis (ECRB)

It is more accurately described as tendinosis rather than inflammation.

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Clinical Features

Patients commonly present with:

• Pain over the lateral epicondyle
• Radiation of pain into the forearm
• Weak grip strength

Pain is aggravated by:

• Resisted wrist extension
• Resisted middle finger extension

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Differential Diagnosis

Important differentials include:

• Radial tunnel syndrome
• Ligament injuries
• Cervical radiculopathy
• Intra-articular elbow pathology

A useful distinction:

• Lateral epicondylitis ? pain directly over epicondyle
• Radial tunnel syndrome ? pain 3–5 cm distal to epicondyle

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Treatment

Conservative Treatment

Approximately 75% improve with:

• Rest
• Splinting
• Physiotherapy
• Steroid injections

Important Clinical Point

Avoid overly tight counterforce braces because they may cause posterior interosseous nerve compression.

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Surgical Treatment

Surgery may be considered after 6–12 months of failed conservative management.

Procedures include:

• Debridement of diseased tendon
• Release procedures

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Flexor Carpi Radialis (FCR) Tendinitis

Overview

FCR tendinitis is an uncommon cause of radial volar wrist pain caused by stenosing tenosynovitis within a tight fibro-osseous tunnel.

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Clinical Features

Symptoms include:

• Radial volar wrist pain
• Pain worsened by wrist flexion
• Pain during lifting or repetitive activities

Localized tenderness is present over the FCR tendon.

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Risk Factors

• Repetitive wrist use
• Carpometacarpal arthritis
• Scaphotrapeziotrapezoid arthritis
• Post-traumatic changes

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Diagnosis

MRI

May show:

• T2 hyperintensity around the tendon

Diagnostic Injection

Local anesthetic injection can be highly useful diagnostically.

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Treatment

First-Line Management

• Splinting
• NSAIDs
• Steroid injection

Surgery

Persistent symptoms may require:

• Tendon sheath release

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Intersection Syndrome

Overview

Intersection syndrome is an overuse condition caused by friction where the:

• First dorsal compartment (APL, EPB)

crosses the:

• Second dorsal compartment (ECRL, ECRB)

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Commonly Affected Individuals

Seen frequently in:

• Rowers
• Weightlifters
• Climbers
• Ice axe users

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Clinical Features

Typical findings include:

• Pain 4–5 cm proximal to wrist
• Swelling
• Crepitus

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Differential Diagnosis

Important differential:

• De Quervain’s tenosynovitis

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Treatment

Conservative Management

Approximately 60% improve with:

• Wrist and thumb splinting
• NSAIDs
• Steroid injections

Surgical Treatment

Persistent symptoms may require release of:

• First dorsal compartment
• Second dorsal compartment

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Lindburg-Comstock Syndrome

Definition

Lindburg-Comstock syndrome is caused by an anomalous connection between:

• Flexor Pollicis Longus (FPL)
• Flexor Digitorum Profundus (FDP) to the index finger

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Clinical Features

Patients may have:

• Difficulty independently flexing thumb and index finger
• Volar forearm or wrist pain
• Symptoms triggered by repetitive activity

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Clinical Examination

Passive extension of the index finger while flexing the thumb may reproduce:

• Pain
• Linked movement

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Treatment

Surgical options include:

• Excision of anomalous connection
• Tenosynovectomy

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Saddle Deformity (Interosseous-Lumbrical Adhesion)

Etiology

Usually occurs after:

• Crush injury
• Hand trauma

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Pathophysiology

Adhesions develop between:

• Interosseous muscles
• Lumbrical muscles

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Clinical Features

Patients may complain of:

• Pain in intermetacarpal space
• Difficulty extending fingers
• Pain during gripping

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Examination

• Positive intrinsic tightness test

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Treatment

Surgical Management

• Adhesiolysis

Most patients show good improvement following surgery.

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Sesamoiditis of the Thumb MCP Joint

Overview

Sesamoiditis is a rare cause of thumb metacarpophalangeal joint pain.

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Clinical Features

• Localized MCP joint pain
• Pain during flexion-extension movement
• Grinding sensation

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Diagnosis

Diagnosis is based on:

• Clinical examination
• Focused radiographs

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Treatment

Conservative Treatment

• Splinting
• Steroid injection

Approximately 70% respond to conservative management.

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Surgical Treatment

Persistent symptoms may require:

• Sesamoidectomy

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Glomus Tumor

Origin

Glomus tumors arise from:

• Glomus bodies involved in thermoregulation

Most commonly located in the:

• Subungual region

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Classic Clinical Triad

Patients typically present with:

• Severe localized pain
• Cold sensitivity
• Point tenderness

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Clinical Tests

Useful examination tests include:

• Love’s pin test
• Cold sensitivity test

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Important Diagnostic Considerations

Suspicious nail lesions should always be biopsied to exclude:

• Squamous cell carcinoma
• Melanoma

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Treatment

Surgical Excision

Definitive management is:

• Complete excision

Recurrence

Recurrence rates range from:

• 1–18%

Usually due to incomplete excision.