Conservative treatment of humeral shaft fractures with radial nerve axonotmesis
Electrodiagnostic study

 

G. SKOUTERIS[1], D. PATATOUKAS[2], S. KALOS[1], E. SARIDAKI[2], P. THOEDORAKOPOULOS[1], N. LAGOGIANNIS[2]
[1]2nd Orthopaedic Department, Asklepieion General Hospital, Voula, Greece
[2]Department of Physical & Rehabilitation Medicine, Asklepieion General Hospital,
Voula, Greece

 

ABSTRACT
The purpose of this study is to evaluate the recovery of radial nerve palsy after humeral shaft fracture. Eleven patients with posttraumatic radial nerve palsy (axonotmesis), following closed humeral shaft fractures were treated by Sarmiento splint without early exploration of the nerve. All patients had acute and complete paralysis of the muscles, innervated by the radial nerve (triceps not included). Electrodiagnostic studies (including electro-myography of the muscles innervated by the radial nerve, and measurement of the distal radial motor and sensory potential) and Manual Muscle Tests were performed within 3 days and in 1, 2, 4 and 6 months from the accident. In the first examination, 3 days postinjury, all patients demonstrated no motor unit action potentials (MUAP), but distal radial motor provoked potential (DRMPP). Muscle test was 0/5. One month postinjury, all patients demonstrated no MUAP, but DRMPP and spontaneous activity. Two months postinjury, 6 patients demonstrated reinnervation in muscles innervated by the radial nerve, and four month postinjury all patients demonstrated reinnervation. The muscle grade was 4/5 in 7 patients and 3/5 in the rest. Six months postinjury, muscle grade was 5/5 in 6, 4/5 in 3 and 3/5 in 2 patients. In conclusion, we believe that in cases of axonotmesis of radial nerve, following humeral shaft fracture with electrodiagnostic signs of recovery, the conservative treatment is preferable with very good results.

Key words: Humeral fracture, axonotmesis, radial nerve.

INTRODUCTION
Radial nerve palsy is the second most common complication associated humeral with shaft fracture. The incidence of this complication varies among reported studies1-5 (table 1). Treatment of these fractures also varies among studies. Early surgical exploration was suggested by some authors[1,6], but during the recent years more authors suggest conservative treatment due to high incidence of spontaneous neurologic recovery of radial nerve palsy and due to limited number of patients underwent surgical exploration[2,3,5,7-11] (table 2).
The decision for early exploration or for initial expectance depends on type, location of the fracture and severity on nerve injury. Spiral, Holstein-Lewis type, fractures of the distal third and fractures of the middle third of the humeral shaft are more frequently associated with radial nerve palsy[1,12]. Even then, in Holstein-Lewis fractures, spontaneous neurologic recovery is very high[7].
Radial nerve palsy occurs during the fracture or iatrogenic during the surgical exploration of the nerve, and this is another reason why some authors suggest conservative treatment[11,13,14].
The aim of this study is to evaluate the rate and degree of spontaneous neurologic recovery in patients with humeral shaft fractures associated with radial nerve axonotmesis, with series of electrodiagnostic studies.

MATERIAL AND METHOD
Eleven patients with humeral shaft fracture associated with radial nerve palsy that did not fulfill the criteria of early nerve exploration were studied. They were conservatively treated with immobilization in a Functional Sarmiento brace. Nine patients were male and two female aged 24 to 50 years old. Five fractures were simple and six were comminuted. Three of the comminuted were Holstein-Lewis type. Patients had an evaluation protocol included clinical, radiological and mainly electrodiagnostic studies in regular base due to posttraumatic radial nerve palsy (axonotmesis) that was diagnosed during the first month.
Methods of evaluation of the nerve recovery were the measurement of the grade of Manual Muscle Test (MMT) according to Medical Research Council Scale ranged from 0 (no contraction) to 5 (normal response) (table 3). Electrodiagnostic studies were also performed including Electromyography (EMG) and radial Nerve Conduction Velocity (NCV).
Follow up of the patients were performed 3 days, 1 month, 2 months, 4 months and six months postinjury. Complete recovery was considered at MMT grade 3/5.

RESULTS - ELECTRODIAGNOSTIC STUDY
All patients had complete radial nerve palsy. First examination was performed 3 days postinjury. MMT revealed that brachioradialis, extensor carpi radialis longus, extensor carpi ulnaris, extensor digitorum, extensor indicis, extensor digiti minimi, abductor pollicis longus, and extensor pollicis longus and brevis were at grade 0/5. EMG showed absence of motor unit action potentials (MUAP) and absence of spontaneous activity (SA). Compound motor unit potential (CMUP) from radial nerve was difficult to be recorded due to the presence of the Sarmiento splint. Distal sensory latency was recorded. These evidence couldn't made the distinction between neuraplaxia and axonotmesis but could exclude neurotmesis.
Thirty days postinjury, all patients had MMT grade 0/5, distal sensory latency was disappeared and spontaneous activity (positive ways and fibrillations) appeared. These were enough to exclude neurapraxia (intact nerve axons, absence of Wallerian degeneration).
In axonotmesis, that mostly occurs in closed fractures[15], nerve axons are damaged, although endoneurium, perineurium and epineurium remain intact. Axonal loss leads to degeneration, that is reversible in such cases, and finally leads to reinnervation.
Sixty days postinjury, in 6 patients reinnervation evidence appeared under the form of low amplitude, long duration, polyphasic MUAPs. MMT of these patients were 2/5. One hundred and twenty days postinjury, reinnervation evidence appeared in all patients. MMT in 7 patients was 4/5, and in the rest patients was 3/5. One hundred and eighty days postinjury MMT was 5/5 in 6 patients, 4/5 in 3 and 3/5 in 2 patients. Table 4 shows the rate and degree of recovery of all patients.

DISCUSSION
Radial nerve palsy after closed humeral shaft fracture occur primary at the time of the initial trauma, secondary after close reduction of the fracture and delayed during the treatment period. Radial nerve is most vulnerable at the middle and distal part of humeral shaft as it is in close contact to bone and as it is less mobile as it enters the lateral intermuscular septum. Therefore, radial nerve palsy is most often associated with spiral distal humeral fracture (Holstein-Lewis type).
Injury at the radial nerve, with frequency up to 18%, is the second most common complication after humeral fracture. Patients with radial nerve palsy associated humeral fracture retain active elbow extension with loss of active wrist and fingers extension.
All patients of our study had axonotmesis and all of them (100%) gained muscle strength of grade 3/5 or more by 4 months postinjury. Muscle strength 3/5 is considered as functional strength since antigravity full range of motion allows patients to perform fundamental function of the hand like grasping, moving and releasing objects.
Our results are similar to other studies which give incidence of neurologic recovery from 60% to 100%[2,3,5,7-11].
Primary radial nerve palsy is frequent and as a result of neuraplaxia, recovers quickly without surgical intervention. In cases of more severe lesions like axonotmesis, the question of early surgical exploration is posed, because in early stages the differential diagnosis between axonotmesis and neurotmesis is not easily established.
According to Pollock et al[9], primary nerve injuries are neurapraxias and neurotmeses that recover after 8 weeks up to 92%. They recommend waiting time 3-4 months before proceeding to nerve exploration.
Postaccini and Morace[16] recommend early surgical intervention based on four criteria: fracture site, degree of displacement, soft tissue injuries and neurological deficits. In their study, the rate of neurologic recovery of radial nerve in the conservative treatment group and the early exploration group is the same (86%).
Indications of early nerve exploration are the open humeral shaft fractures, sudden nerve palsy after closed reduction, progressive nerve palsy after the fracture and fractures associated with gunshots or sharp objects[7,17].
As the treatment of humeral shaft fractures is mainly conservative with plaster sling at the beginning and functional brace later, in cases of radial nerve palsy, it is very important to distinguish as early as possible with electrodiagnostic studies whether the nerve injury is neurapraxia, axonotmesis or neurotmesis and thus make the decision to continue or not the conservative treatment.

CONCLUSION
The good progress of our cases confirms the view that humeral shaft fractures associated with radial nerve palsy (axonotmesis) with recovery signs in electrodiagnostic studies, should be continuously treated conservatively without early exploration.
It should be emphasized the importance of early electrodiagnostic evaluation that will distinguish whether the nerve injury is neurapraxia or axonotmesis or it is neurotmesis were exploration is inevitable.
Our study proves that in humeral shaft fractures associated with radial nerve palsy, proper and regular electrodiagnostic tests can lead to continuation of conservative treatment not only in cases with neurapraxia but also in cases with axonotmesis with high incidence of nerve recovery. Surgical exploration should only be considered if evidence of neurotmesis is present.

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Dimitrios Patatoukas
Asklepieion General Hospital
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