Posterior Interosseus Nerve Syndrome

Other Names

• PIN Compression Syndrome
• PIN Syndrome

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Background

• Compressive neuropathy of the Posterior Interosseous Nerve, a branch of the Radial Nerve

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Pathophysiology

• Three subcategories
  • Neuropraxia: Mildest form, demyelination from compression or traction
  • Axonotmesis: Moderate form, demyelination as well as axonal injury
  • Neurotmesis: Severe, nerve is transected
• Anatomic areas of pathology
  • Most frequently occurs at the Arcade of Frohse
  • Between the Brachialis and Brachioradialis
  • Leash of Henry
  • Edge of Extensor Carpi Radialis Brevis
  • Edge of Supinator
• Etiology
  • Idiopathic
  • Microtrauma
  • Trauma
    • Monteggia fractures
    • Radial head fracture-dislocations
  • Space-occupying lesions
  • Brachial Neuritis
  • Spontaneous compression
  • Iatrogenic (surgery)

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Risk Factors

• Males > Female (2:1)
• Right > Left arm
• Manual Laborers
• Bodybuilders

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Differential Diagnosis

Differential Diagnosis Wrist Pain

• Fractures
  • Distal Radius Fracture
    • Barton's Fracture
    • Chauffer's Fracture
    • Colles' Fracture
    • Die-Punch Fracture
    • Radial Styloid Fracture
    • Smith's Fracture
  • Distal Ulna Fracture
  • Carpal Fractures
    • Scaphoid Fracture
    • Lunate Fracture
    • Triquetrum Fracture
    • Pisiform Fracture
    • Trapezium Fracture
    • Trapezoid Fracture
    • Capitate Fracture
    • Hamate Fracture
  • Essex Lopresti Fracture
• Dislocations
  • Wrist Dislocation (Radiocarpal and/or Ulnocarpal)
  • Carpometacarpal Joint Dislocation
  • Distal Radioulnar Joint Dislocation
  • Lunate Dislocation
  • Perilunate Dislocation
• Instability & Degenerative
  • Scapholunate Instability
  • Lunotriquetral Instability
  • Scaphoid Nonunion Advanced Collapse
  • Distal Radial Ulnar Joint Instability
  • Kienbocks Disease
  • Dorsal Wrist Impingement
• Tendinopathies & Ligaments
  • De Quervain's Tenosynovitis
  • Intersection Syndrome
  • TFCC Injury
  • Wrist Tendinopathies
  • Extensor Carpi Ulnaris Instability
• Neuropathies
  • Carpal Tunnel Syndrome
  • Pronator Teres Syndrome
  • Anterior Interosseus Nerve Syndrome
  • Posterior Interosseus Nerve Syndrome
  • Guyon Canal Syndrome
• Pediatric Considerations
  • Distal Radial Epiphysitis (Gymnast's Wrist)
  • Torus Fracture
• Arthropathies
  • Wrist Osteoarthritis
  • Rheumatoid Arthritis
  • Gout
• Cartilage
  • Osteochondral Defect
• Vascular
  • Hypothenar Hammer Syndrome
• Other
  • Ganglion Cyst of Wrist
  • Ulnar Impingement Syndrome
  • Infectious Tenosynovitis

Differential Diagnosis Forearm Pain

• Fractures
  • Distal Radius Fracture
    • Barton's fracture
    • Chauffer's Fracture
    • Colles' Fracture
    • Die-Punch Fracture
    • Radial Styloid Fracture
    • Smith's Fracture
  • Radius Ulna Fracture (Both Bone)
  • Proximal Radius Fracture (Head, Neck)
  • Isolated Ulna Fracture
  • Monteggia Fracture
  • Galeazzi Fracture
  • Distal Ulna Fracture
  • Essex Lopresti Fracture
• Pediatric Specific Fractures
  • Torus Fracture
  • Greenstick Fracture
  • Salter Harris Fracture
  • Plastic Deformation
• Dislocations & Instability
  • Distal Radioulnar Joint Dislocation
  • Proximal Radioulnar Joint Instability
• Soft Tissue Trauma
  • Acute Compartment Syndrome
• Tendinopathies
  • De Quervain's Tenosynovitis
  • Intersection Syndrome
• Neuropathies
  • Radial Tunnel Syndrome
  • Posterior Interosseus Nerve Syndrome
• Pediatric Considerations
  • Distal Radial Epiphysitis

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Clinical Features

• General: Physical Exam Wrist
• Often goes undiagnosed
• History
  • Etiology is frequently idiopathic, although history of trauma or injury may endorsed
  • Patients often endorse weakness in finger and thumb extension
  • Vague pain in forearm and wrist
• Physical exam
  • Examiner may notice atrophy of extensor muscles
  • Wrist extension is preserved because ECRL is innervated by the radial nerve
  • There may be deviation to the radial side due to ECU weakness and intact ECRL
  • Tinel’s Test can be positive
  • Resisted supination can reproduce symptoms

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Evaluation

Radiographs

• Standard Radiographs Wrist
• Typically normal unless history of trauma
• Useful to evaluate for other etiologies

MRI

• Not commonly needed, helpful to evaluate for other pathology
• Can identify some causes of PIN compression

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Classification

• N/A

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Management

Nonoperative

• Initial management is typically conservative
• Splinting
• NSAIDS
• Physical Therapy
• Activity modification
• Some etiologies can respond to a Corticosteroid Injection

Operative

• Reserved for those who fail at least 3 months conservative therapy
• Involves surgical decompression

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Return to Play

• Needs to be updated

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Complications

• Surgical complications
  • Incomplete decompression
  • Continuation of symptoms
  • Ininability to return to work

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See Also

• Internal
  • Neuropathies (Main)
  • Hand and Wrist Anatomy (Main)
  • Wrist Pain (Main)
  • Forearm Pain (Main)
  • Elbow Pain (Main)
  • Physical Exam Wrist
• External
  • Sports Medicine Review Wrist Pain: https://www.sportsmedreview.com/by-joint/wrist/

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