Definition
Dynamic structural compression syndrome of PIN
- causing pain with little or no muscular weakness
- similar presentation to lateral epicondylitis / pain more distal
Anatomy
Radial tunnel begins at radiohumeral joint
Extends to end of supinator muscle
Sites of compression
PIN can be compressed by FREAS in radial tunnel
Fibrous bands
- level of radio-capitellar joint
Recurrent leash of Henry
- radial recurrent artery
- vessels to mobile wad
ECRB
- nerve branches caught between ECRB and supinator
Arcade of Frohse
- free fibrous proximal edge supinator (superficial belly)
- most common site of compression
- thought to be more tendinous in some patients (30 - 80%)
- thought to become more fibrous in some patients with repetitive supination
Supinator distal edge
- occasional cause
- always decompress to here
Clinical
Pain is similar to tennis elbow
- lateral elbow joint / CEO area often radiating to wrist
- deep ache or similar to muscle cramp
- often at night
- exacerbated by exercise
- relieved by rest
Examination
Point tenderness 5cm distal to CEO
- more proximal with Tennis Elbow
- Often tender in normal individual --> compare to other side
Provocation test
- Arcade of Frohse
- resisted supination
NCS
- unhelpful / usually normal
Local Anaesthetic block
Best test
- inject LA in most tender spot
- usually distal to CEO
- must produce PIN palsy to confirm diagnosis
- A prior negative injection to lateral condyle for tennis elbow
DDx
Tennis Elbow
- failure of HCLA lateral epicondyle to relieve pain
- can have both tennis elbow and radial tunnel syndrome
Radiocapitellar pathology
- OA / RA / OCD / Loose body
- no pain with supination / pronation
Radiculopathy
NHx
Tends to resolve spontaneously
Management
Non-Operative
RICE
Avoid provocative activities
Splint
Operative
Options
- anterior (can release all potential sites of compression)
- posterior (can only release supinator)
- brachioradialis muscle splitting
Anterior approach
Henry's approach
- start 4cm proximal to elbow joint
- identify nerve between BR & Brachialis & then follow distally
- release any proximal fibrous bands / divide recurrent vessels
- pronate / supinate and release ECRB if any compression
- fully pronate and divide all fibres of supinator
Posterolateral approach
Thompson's
- incision just distal to lateral condyle for 8cm
- dissection between ECRB & EDC
- identify supinator
- find PIN distally and follow proximally
Trans-brachial approach
Brachioradialis splitting
- direct approach to radial tunnel
- longitudinal incision 6cm long over BR at neck of radius
- incise BR in line of incision
- identify fat covering superficial Radial Nerve
- beneath this branch is arcade of Frohse and PIN
- extend proximally and distally till released
Results
Jebson et al J Hand Surg Am 1997
- surgical release in 31 patients
- excellent or good results in 67%, fair or poor in 33%
Lee et al J Plast Recons Aesthet Surg 2008
- 86% good results in isolated radial tunnel syndrome
- dropped to around 50% if
- other nerve compression / lateral epicondylitis / workers compensation