Anterior Interosseous Nerve Palsy

Definition

 

Symptoms & signs due to compression of AIN

 

Sites of Compression

 

Fibrous

- Pronator Teres (most common)

- FDS arch

- Fascial bands 

- Bursa

 

Vascular

- thrombosis in leash vessels over AIN

 

Muscular

- aberrant belly FPL (Gantzer's)

- palmaris profundus

- aberrant FCR ulnar origin

- anomalous FDS origins

 

History

 

1.  Pain in proximal forearm

- vague pain

- most common symptom

 

2.  Motor deficiency

- FPL

- IF FDP

- PQ

 

3.  No sensory disturbance

 

Examination

 

Discomfort over site of compression

 

Inability to tip-to-tip pinch grip IF &Thumb

- weak pulp-to-pulp pinch possible

- Weak FPL / Index FDP / PQ

 

Provocation

- resisted pronation with elbow flexed 90o

 

Investigation

 

EMG FDP / FPL / PQ

 

DDx

 

Rupture FPL / FDP

Median N entrapment

C8 lesion

 

Management

 

Non operative Management

 

Avoid Aggravating Factors

RICE

NSAIDS

 

Operative Management

 

Technique

 

Release

- as per pronator syndrome

 

Results

 

Schantz et al J Hand Surg Br 1992

- 20 cases of AIN compression

- operated on 15 with 12 good results / 3 required tendon transfer

- non operative on 5 / 3 continued palsy at 4 years

- recommended operative release