It has long been suspected that compression of the intercostal nerve by the rib spreader is a major cause of both post thoracotomy pain and long term intercostal neuralgia.  A neurophysiological study by John Duffy’s team from Nottingham demonstrated the extent of intercostal nerve injury during thoracotomy (Rogers 2002).  They used a probe to stimulate intercostal nerves and bipolar electrodes to record evoked potentials anteriorly in the nerve adjacent to the thoracotomy.  They found that in all cases the nerve above the incision suffered a total conductional block immediately after the insertion of the retractor.  The nerve below suffered a total conduction block in most cases and the nerves in the interspaces above and below these adjacent nerves showed a considerable incidence of partial conduction block.

They found that multiple intercostal nerves are routinely injured during rib spreading and the nerves immediately above and below were invariably injured.  They postulated a direct ischaemic effect caused by direct pressure on the intercostal nerve immediately above the incision.  They noted that there was a discrete conduction block at the distal end of the rib retractor as soon as it was inserted.  The injury to the adjacent nerves is more likely to be due to a stretch injury (a whole nerve injury akin to a brachial plexus traction injury).  This led to a partial conduction block.

They noted that the method of rib closure did not affect the extent of the nerve injury.  In the absence of rib spreading in a number of cases the intercostal nerve remained intact throughout the incision, operation and closure.  This is the logic behind performing video assisted thoracoscopic surgery without rib retraction. 

Avoiding the intercostal nerve decreases post thoracotomy pain

A group from Korea (Lee 2005) presented a paper at the European Society of  Cardiothoracic Surgeons in September 2005 describing a technique very similar to our own.  They showed that post thoracotomy pain was significantly reduced at two weeks (p=0.024), one month (p=0.026), two months (p=0.007) and three months (p=0.018) post surgery.

Intercostal muscle flap reduces post-thoracotomy pain

A similar technique, but dissecting the whole intercostal flap, has been used by Bob Cerfolio in Birmingham Alabama.  Intercostal muscle flaps have long been used covering bronchial stumps, bringing a vascularised muscle flap to an area of ischaemia.

The group in Alabama noticed that patients with such a flap had decreased post thoracotomy pain.  They performed a prospected, randomised trial of their technique which involves harvesting the intercostal muscle flap including the neuro-vascular bundle, dividing the anterior end near the terminal branches of the nerve and reflecting it posteriorly while the retractor is placed directly against the rib, avoiding any crushing of the nerve.  They found significantly reduced pain at all stages to week 12 postoperatively. 

Post discharge numeric pain rating

(It is not clear whether the reduced pain scores at week 3 are due to the direct face to face interview at this stage, or whether it is a real change from complete anaesthesia to paraesthesia which often occurs after the third week). 

In their study there was also a significant decrease in pain in the first four days postoperatively.  While the aim of most of the nerve strategies is to reduce late post thoracotomy pain, it is interesting they found a reduction in early post thoracotomy pain. 

In-hospital numeric pain scores

Intracostal sutures - do they reduce pressure on the lower nerve?

The Alabama group have also published on the use of intracostal sutures.

This paper from 2003 was prior to their intercostal muscle fat paper and involved drilling holes through the lower ribs passing the costal sutures directly through the ribs.  They reported that they was a reduction in pain scores at all periods from 2 weeks to 3 months. 

This is contrary to our own findings and those of both the Nottingham and Korean groups.  The technique is not without complications. Sandurs and Newman (Sandurs 2005)  reported from Nedlands hospital in Western Australia the combination of local intercostal nerve dissection, as we have described, and the use of intracostal sutures.  They reported the fracture of a number of sutures as they passed through the ribs and the risk of lung hernias.