Radial nerve injuries occur in approximately 12 per cent of humeral shaft fractures. There is an increased risk when the fracture involves either the middle third or occurs at the junction of the middle and distal thirds; this is the site where the nerve is relatively immobile as it emerges from the spiral groove and traverses the intermuscular septum. Although 90 per cent comprise neurapraxia and recover fully, the nerve may also potentially become entrapped between fracture segments or be lacerated by the fracture.
The first step in the management of radial nerve injuries is to undertake a detailed assessment of the neurovascular status at the time of presentation. This must be carefully documented. Electrophysiological nerve assessment is not of value until 3–4 weeks after injury; furthermore, to defer intervention beyond this time must be measured against increased surgical difficulty and poorer outcomes if nerve repair is necessary. Decision- making should therefore be based on a clinical assessment of neurological function.
Once detected, the management of the nerve palsy should be tailored to the pattern and level of the fracture. Any fracture involving the intermuscular septum represents a higher risk to the nerve, which is relatively fixed at this point. Although all radial nerve palsies should be treated with a wrist extension splint and physiotherapy until recovery is noted, early intervention is recommended or, if in doubt, consultation with a peripheral nerve injury surgeon.
The following is a suggested guide:
Radial nerve palsy with a closed and favourable (stable) fracture pattern: If radial nerve palsy is noted at the time of presentation of a closed but favourable fracture pattern, the likely diagnosis of the nerve lesion is a neurapraxia. Because the management of such fractures is likely to be non-operative, a conservative approach may be initially adopted. However, if no neurological recovery is noted at 3 weeks,
and this is supported by unfavourable electromyographic (EMG) studies, surgical exploration should be undertaken. The timing of this intervention should allow a relatively straightforward dissection that is not complicated by excessive inflammation or early callus formation.
Radial nerve palsy with a closed but unfavourable fracture pattern: In such circumstances one must assume that radial nerve injury has occurred and therefore the nerve must be addressed as well as the fracture. This necessitates an open procedure such that the nerve can be explored, as well as a definitive plating procedure.
Radial nerve injury with an open fracture:
In the presence of an open fracture and nerve palsy, the radial nerve must be considered lacerated until proven otherwise.
Open exploration must therefore be
undertaken, at which time definitive plating or possibly intramedullary nailing can be undertaken.
Radial nerve palsy after manipulation under anaesthesia: If the nerve was functioning before MUA, this situation is an absolute indication for immediate surgical exploration to ensure that nerve entrapment has not occurred.
Radial nerve palsy following open reduction and internal plate fixation: Provided the radial nerve was meticulously protected throughout the procedure and the plate was accurately placed, avoiding any nerve entrapment at the time of surgery, postoperative radial nerve palsy can be monitored until recovery. If, however, the radial nerve was not visualized and/or protected, exploration is necessary.
Radial nerve palsy after intramedullary nailing: The management of this situation depends on the level of the fracture and placement of the locking screws. If the fracture is at the level of the spiral groove, or if the locking screws are anatomically close to the course of the radial nerve, then exploration of the nerve should be considered. Otherwise, the injury can be assumed to be neurapraxic and investigated with EMG studies 3 weeks postoperatively.
Care with intramedullary nailing is therefore essential – some authors advocate direct visualization of the fracture site in all cases where intramedullary nailing is undertaken, to ensure that the radial nerve is not damaged during either fracture reduction or the reaming process.
REFERENCES AND FURTHER READING
Holstein A, Lewis GM. Fractures of the
humerus with radial nerve paralysis. J Bone Joint Surg Am 1963;45:1382–8.
Müller ME, Nazarian S, Koch P, Schatzker J.
The Comprehensive Classification of Fractures of Long Bones. Berlin: Springer, 1990, pp 120–1.
Sarmiento A, Latta LL. Functional Fracture Bracing: Tibia, Humerus, and Ulna. New York:
Springer; 1995.
Shao YC, Harwood P, Grotz M, et al. Radial nerve palsy associated with fractures of the shaft of the humerus. J Bone Joint Surg Br 2005;87:1647–52.
Zagorski JB, Latta LL, Zych GA, Finnieston AR.
Diaphyseal fractures of the humerus: treatment with prefabricated braces. J Bone Joint Surg Am 1988;70:607–10.
MCQs
1. Concerning the anterolateral approach to the humerus:
a. The incision cannot be modified to address a concurrent shoulder injury.
b. The musculocutaneous nerve is retracted laterally to avoid iatrogenic injury.
c. Dissection relies on the dual innervation of the brachialis muscle to maintain the viability of the muscle during the approach to the humerus.
d. The brachialis muscle is reflected laterally to expose the shaft.
e. The approach may also be used for the management of distal humeral fractures.
2. A complex closed mid-shaft segmental humeral fracture, with no neurological compromise, in a 30-year-old patient:
a. Is classified using the AO classification as a 12-C1 fracture.
b. Is best managed with a retrograde IM nail.
c. Should be approached via a posterior approach if an ORIF is planned.
d. Should initially always be managed non-operatively.
e. Must have the radial nerve fully isolated before proceeding with fixation.
Viva questions
1. Discuss the course of the radial nerve from the brachial plexus to the hand.
2. What risks are involved in antegrade and retrograde IM nailing of the humerus? How can you minimize these risks?
3. What factors would lead you to manage a humeral shaft fracture conservatively?
4. Describe the anterolateral approach to the humerus. In which mid-shaft humeral fractures would you not use this approach?
5. How would you manage a pathological mid- shaft humeral fracture in an 85-year-old patient?
Introduction Assessment Anatomy
Surgical approaches Capitellar fractures Coronoid fractures Elbow dislocations Distal humeral fractures
Total elbow arthroplasty Olecranon fractures Radial head fractures Hinged external fixators Distal biceps tendon rupture MCQs
Viva questions