|Year : 2016 | Volume
| Issue : 3 | Page : 147-150
Proximal humerus fracture associated with delayed axillary nerve injury
Department of Rehabilitation, Srinagarind Hospital, Khon Kaen University, Khon Kaen, Thailand
|Date of Web Publication||14-Sep-2016|
Department of Rehabilitation, Faculty of Medicine, Srinagarind Hospital, Khon Kaen University, Khon Kaen
Source of Support: None, Conflict of Interest: None
Axillary nerve injury is the most common complication in humerus fracture. The symptoms that are caused by affecting axillary nerve vary according to the structures involved such as sensory disturbance and weakness of muscles, e.g., three parts of deltoid and teres muscles in an affected limb. The severity of injury is classified in demyelinating and axonal lesions, which usually occurs at the onset of fracture. The author reports a case of humerus fracture with delayed axonal lesion of axillary nerve result from inadvertent traction.
Keywords: Axillary nerve injury, electrodiaginostic study, humerus fracture
|How to cite this article:|
Sirasaporn P. Proximal humerus fracture associated with delayed axillary nerve injury. J Sci Soc 2016;43:147-50
| Introduction|| |
Incidence of proximal humerus fracture is 2-3% of upper extremity fracture.  This injury usually occurs as a result from a direct blow to the shoulder, either in a fall or as the result of a high-energy trauma. It usually can be treated conservatively with immobilization by casting but more complex fracture patterns often require an operation.  Moreover, this injury is associated with neurovascular injuries about 21-36%.  Axillary nerve injury is the most common complication because such a nerve runs just anterior and inferior to the glenohumeral joint, so the proximity of the axillary nerve makes it particularly vulnerable to both traumatic and iatrogenic injury. , The symptoms that are caused by affecting axillary nerve vary according to the structures involved, such as sensory disturbance and muscle weakness in an affected limb. Moreover, the severity of nerve injury is variable as demyelinating or axonal lesion depends on the severity of injury.  However, no previous study reported delayed axonal lesion of axillary nerve injury.
| Case report|| |
The case of a 25-year-old, right hand dominant female presented with a sudden right shoulder pain after she had fallen from a bicycle. On initial examination, there was limitation of the right shoulder movement in all directions due to severe pain. The sensation was intact. However, muscle power of the right upper limb could not be evaluated. The anteroposterior shoulder radiograph showed fracture of the right proximal humerus. A general physician, practicing in a primary care hospital first diagnosed her symptom as right proximal humerus fracture and decided to immobilize the right arm by casting [Figure 1]. After 6 weeks, the casting was removed. Range of motion exercise of the right shoulder was advised. There was no muscle weakness or numbness. She felt a little pain at her shoulder and was able to move her right arm in all directions. She was able to return to work and live independently. However, 1 week later, she got a traditional Thai massage for body relaxation for about 1 hour, after which, she noticed that she could not move her right arm independently and felt numbness around her right shoulder. She immediately came to the tertiary care hospital. An orthopedic surgeon urgently reevaluated the patient and investigated anteroposterior shoulder radiograph and computed tomography scan of the right shoulder that revealed comminuted fracture of the right proximal humerus [Figure 2] and [Figure 3]. The orthopedic surgeon first diagnosed her symptoms as right proximal humerus fracture together with suspected right axillary nerve injury. She was referred on to the rehabilitation clinic for further investigation. Therefore, electrodiagnostic study was performed to confirm and localize the lesion.
|Figure 1: The anteroposterior radiograph of the right shoulder showing proximal humerus fracture with casting|
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|Figure 2: The anteroposterior radiograph of the right shoulder with an arrow showing proximal humerus fracture|
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|Figure 3: Computed tomography scan of the right shoulder with arrows showing comminuted fracture of right proximal humerus|
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At a rehabilitation clinic, 1 month later, physical examination revealed mild muscle atrophy at the right shoulder. Limited right shoulder passive range of motion in all directions was detected due to severe pain. Motor power of the right anterior deltoid, middle deltoid, and posterior deltoid muscles were all at least grade 1, whereas motor power of right biceps, triceps, extensor carpi radialis, flexor digitorum superficialis, abductor pollicis brevis, and abductor digiti minimi were all grade 5. Impaired pinprick sensation and temperature sensation at the right axillary nerve dermatome were noted. Tinel's sign was negative at right Erb's point. Deep tendon reflex at right biceps jerk and triceps jerk were normal.
Nerve conduction studies (NCS) and needle electromyography was conducted. NCS showed no electrical motor response at the right motor axillary nerve compared to the left motor axillary nerve [Table 1]. Needle electromyography showed increased insertional activity, variability of spontaneous activity, polyphasic, and impairment of recruitment at right anterior deltoid, middle deltoid, posterior deltoid, and teres minor muscles [Table 2]. This result was summarized to incomplete right axillary nerve injury and axonal involvement.
The patient underwent surgery 1 week later. The operation was done under general anesthesia. There was comminuted fracture of the right proximal humerus that was compromised to the right axillary nerve. It was found to be bruised. The comminute bones were reduced and fixed with proximal humerus locking plate to its anatomical bed [Figure 4]. There were no operation-related complications.
|Figure 4: The anteroposterior radiograph of the right shoulder with an arrow showing proximal humerus locking plate|
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Postoperatively, the shoulder was supported in a shoulder sling and passive-assisted pendulum exercise was recommended. She had no pain and felt better in sensation at the right axillary nerve dermatome, 6 weeks after operation. She was advised for a progressive range of motion exercise and strengthening exercise of right shoulder girdle muscles. The muscle power of right deltoid muscles was normal and no other complications were found 6 months later.
| Discussion|| |
Most common neurologic sequela of proximal humerus fracture is the axillary nerve.  Patients with axillary nerve injury present frequently with weakness of the shoulder girdle muscle and numbness or paresthesia in the lateral shoulder area. The physician should differentiate it from brachial plexopathy. Neurological findings of axillary nerve injury include only weakness of three parts of deltoid muscles and numbness along axillary nerve distribution and no variable weakness in other innervated muscles. The hallmarks of electrodiagnostic study for axillary nerve injury are spontaneous activity in only axillary innervated muscles including anterior deltoid, middle deltoid, posterior deltoid, and teres minor muscles. The motor NCS of axillary nerve reveals diminished or no electrical response. 
This report showed that delayed axonal lesion of the axillary nerve can occurr in proximal humerus fracture, especially in comminuted fracture.  The causes of axillary nerve injury in this patient may be caused by a result of inadvertent traction from massage in the fragile humeral bone. This force caused fracture of fragile bones and caused a compromise to the axillary nerve. However, most of proximal humerus fractures are nondisplaced or minimally displaced, which are treated nonoperatively by casting and an early range of motion exercise. While comminuted fractures, such as in this case, are usually treated operatively such as open reduction and internal fixation. , Moreover, rehabilitation is ongoing for months. The goal of rehabilitation is progressing from passive activities to all range of motions being fully active. In conclusion, the physician should become aware of axillary nerve injury, especially in comminute fracture. Neurological examination is important during assessment of the patient. The axillary nerve can be tested via sensation over the deltoid muscle and deltoid motor function. Electrodiagnostic study is a crucial key to confirm diagnosis.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]