Kiloh-Nevin syndrome associated with humeral shaft fracture

Abstract

Fracture humerus may be associated with nerve injuries. However, among them median nerve is uncommonly involved and clinical affection of the anterior branch of median nerve is rare which can be easily missed and could be under-reported. A 42-year-old man presented with closed fracture of shaft of humerus right sided following fall. He had isolated weakness of flexor pollicis longus and flexor digitorum profundus of index finger without any other sensorimotor dysfunction. The findings were consistent with isolated palsy of anterior interosseous nerve (AIN). The patient was operated with fixation of humerus without exploring the AIN. At 6-month follow-up, the patient had complete recovery of both the muscles. This case highlights the classical clinical presentation of a rare injury associated with humerus fracture. Awareness and knowledge of this entity is of paramount importance for the practitioners.

Background

Humerus fractures are more commonly associated with nerve injuries than any other long bone fracture. But injury to median nerve with humeral shaft fracture is uncommon because of anatomical protection of posterior compartments of muscles. Anterior interosseous nerve (AIN) is a branch of median nerve providing motor supply to flexor pollicis longus, flexor digitorum profundus of index and pronator quadratus. Clinical affection of the anterior branch of median nerve is rare which can be easily missed and could be under-reported. Though management is conservative with full recovery, awareness and knowledge of this entity among the students and practising orthropods is important to explain the complicated and also functional outcome of fracture management.

Case presentation

A 42-year-old man presented with closed fracture of shaft of humerus right side following fall with outstretched hand (figure 1A). After primary care, initial stabilisation with U slab applied. On next day ward round, the patient complained of pain in proximal forearm and dysfunction of hand of the same side. Plaster was removed and thorough clinical exploration was done. He had weakness of flexor pollicis longus and flexor digitorum profundus of index finger without any evidence of remaining median nerve dysfunction. Ulna and radial nerve examination was normal. There was no sensory deficit. According to the patient, the weakness of thumb and index finger was there immediately after injury.

Figure 1.

X-rays of the patient preoperative (A) and postoperative (B) demonstrating fracture shaft of humerus and fixation on the right side.

The findings correlated with isolated palsy of AIN. He was asked to demonstrate the ‘O’ sign using thumb and index finger but he failed. On attempted ‘O’ sign there was increased flexion of proximal interphalangeal joint with extension of distal interphalangeal joint of index finger and increased flexion of metacarpo-phalangeal joint with hyperextension of interphalangeal joint of thumb. The pulp contact between thumb and index finger was unusual with area of contact between two tips more proximal than normal (figure 2).

Figure 2.

Clinical picture showing the inability to demonstrate the ‘O’ by using index and thumb in the affected right hand (inset arrow).

Differential diagnosis

Differential diagnoses include brachial neuritis, floxor pollicis longus (FPL) tendon rupture and Parsonage-Turner syndrome (viral neuritis).

Treatment

The patient was taken to the operation theatre for fixation of humerus without exploring the median nerve (figure 1B).

Outcome and follow-up

The patient was followed up regularly. At 6-week follow-up, fracture was uniting and the patient had an Medical Research Council (MRC) grade 2/5 power in both flexor pollicis longus and flexor digitorum profundus. As the recovery was progressive, nerve conduction study seemed unnecessary. At 3-month follow-up, muscle strength increased up to 4/5 MRC muscle grade. At 6 months, the patient had complete recovery of his weakness with full power of both the muscles and he was able to demonstrate ‘O’ with thumb and index finger of the affected hand.

Discussion

An isolated palsy of flexor pollicis longus was first reported in 1872 by Duchene De Boulogne,¹ but a first detailed clinical manifestation of AIN palsy was described by Kiloh and Nevin in 1957.² Since then AIN palsy is known as Kiloh-Nevin syndrome.

AIN is the largest branch of the median nerve, which rises 5–8 cm distal to the lateral epicondyle immediately distal to the superior border of superficial head of pronator teres. But the fibres destined to form AIN can be isolated from median nerve proximal at the level of the brachial plexus. During its course through forearm, it usually innervates three muscles, flexor pollicis longus, radial half of flexor digitorum profundus and pronator quadrates. At the end of its passage, it supplies sensory fibres to radiocarpal, intercarpal and carpometacarpal joints.

Kiloh-Nevin syndrome is a clinical entity with pain in proximal forearm and pure motor palsy of any or all of the muscles innervated by the nerve, FPL, flexor digitorum longus (FDP) of index and pronator quadratus. During an attempted pinch, normally there are varying degrees of flexion in all joints of thumb and index finger. But with Kiloh-Nevin syndrome the index finger shows extension of distal interphalangeal joint (DIP) and increased flexion of proximal interphalangeal joint (PIP) joint, and thumb shows increased flexion of MCP joints and hyperextension of IP joints. Also the area of pulp contact between thumb and index finger becomes more proximal than normal.

The cause of Kiloh-Nevin syndrome is most of the times traction neuropathy or entrapment neuropathy, and less frequently due to direct nerve damage related to fracture. A study by Kleinrensink on the influence of posture and motion on peripheral nerve says a fall with elbow and wrist extended produces traction on median nerve and medial cord.³ Engber and Keene reported a case of palsy following Monteggia lesion and considered traction neuropathy is the most probable mechanism.⁴ Collins and Weber considered entrapment to be the most common cause of AIN palsy.⁵ Schantz and Riegels-Nielson found evidence of nerve compression in 9 of 15 patients.⁶ In four cases reported by Casey and Moed, the usual finding was tight strip of cotton padding across antecubital fossa.⁷ Gessler et al reported a close both bone forearm fracture with AIN palsy, and on surgical exploration found a bony spike perforating the nerve directly.⁸ Direct iatrogenic injury to AIN nerve occurs by improper use of bone forceps, dressings,⁹ slings,¹⁰ venipuncture¹¹ and even after elbow and shoulder arthroscopy.^{12 13}

AIN palsy has mostly been reported with trauma to either supracondylar area of the humerus or trauma to forearm. There are only three case reports of the AIN palsy with injury above the supracondylar level.¹³ Though AIN originates distal to the elbow, the fibres destined to form AIN can be isolated from median nerve proximal at the level of the brachial plexus which explains the Kiloh-Nevin syndrome at level above the supracondylar area.

The differential diagnoses include brachial neuritis, FPL tendon rupture and Parsonage-Turner syndrome (viral neuritis). Diagnoses of Kiloh-Nevin syndrome are mostly clinical. Electrodiagnostic studies confirm the diagnoses and assess the severity of the neuropathy. EMG differentiates palsy from flexor tendon rupture. MRI shows increased signal intensity in AIN innervated muscles on T2 image.

There are no prospective studies or randomised control trials to compare operative management with conservative management or ideal timing of surgical intervention in AIN palsy. Recovery may take a year or more. Spinner et al recommended surgical exploration if no signs of clinical and electromyographical improvement within 6–8 weeks of injury.¹⁴ Hill et al recommended exploration and neurolysis to be undertaken if no clinical improvement within 12 weeks.¹⁵ If motor function does not recover, brachioradialis tendon transfer restores the function satisfactorily. However, spontaneous recovery in a later course has been described by many authors. To our surprise, function of flexor digitorum profundus returned within 3 months and within 6 months complete recovery occurred.

Learning points.

• Emphasising the importance of thorough preoperative assessment.

• Able to diagnose a rare complication clinically.

• Communicating the patient about the condition and explaining prognosis.

• Educating the orthopaedician, particularly students, about the entity.