ultrasound diagnosis.html


    
        
            
                
                    

                

            

            
                Ultrasound diagnosis of ulnar nerve dislocation and snapping triceps syndrome

                V B Gupta, MBBS, DNB
            

            K B Patankar, MD, DMRD
        

        F Paranjpe, MD
    

    J Patil, MD, DNB


Department of Radiology, Apple Hospital, Kolhapur, Maharashtra, India


    Corresponding author: V Gupta (vivekforever@lycos.com)

    
    

    
        Dislocation of
        the ulnar nerve with snapping triceps syndrome has been implicated as a
        cause of cubital tunnel syndrome. Patients with this condition may
        clinically present with a snapping sensation at the elbow upon flexion
        along with ulnar neuropathic symptoms. Though demonstration of this
        condition is possible by static MRI images, ultrasound can be used as a
        more accessible and inexpensive modality for attaining diagnosis. This
        pictorial essay emphasises the technique, findings and role of dynamic
        ultrasound in the diagnosis of this entity.

        
            S Afr J Rad 2012;16(2):65-67.

        

        
        

        Introduction

        The preferred modality for imaging of the
        musculoskeletal system for suspected nerve entrapment is magnetic
        resonance imaging (MRI). Alternatively, high-resolution ultrasound (US)
        can be an inexpensive and more accessible modality. One of the assets
        of US in musculoskeletal imaging is its ability to image parts in
        dynamic motion, which may not be feasible for conventional MRI or CT.
        This essay emphasises the role of US in the diagnosis of ulnar nerve
        dislocation and snapping triceps syndrome and describes the preferred
        technique, imaging findings and dynamic monitoring by US. The essay
        highlights the need for awareness of this entity when dealing with
        medial elbow pain and/or ulnar neuropathy. Though the condition of
        ulnar nerve dislocation itself is not uncommon, the fact that it can be
        associated with triceps snapping is often overlooked, and the
        combination of ulnar nerve dislocation with triceps snapping syndrome
        has been implicated as one of the causes of cubital tunnel syndrome.
        Once diagnosed, options of conservative as well as surgical management
        of the condition are available.

        Clinical presentation

        A 35-year-old male manual labourer presented with
        pain in the left elbow region. He complained of a characteristic
        snapping sensation in the medial aspect of his elbow on flexion. The
        pain was along the ulnar nerve distribution and was often associated
        with tingling and numbness. The symptoms were of increasing severity
        over a 6-month period. There was no history of fever. His past history
        was unremarkable. On local examination, there was no visible swelling
        at the elbow. His basic laboratory investigations were normal. Plain
        films were normal. An US of the left elbow was advised.

        Ultrasound technique

        At sonography, the position of the ulnar nerve was
        noted with respect to the medial epicondyle. The patient was examined
        in the seated position with both elbows comfortably resting on a
        cushion placed on his lap. US of the left elbow was performed at the
        level of the cubital tunnel; this was achieved by placing the
        transducer over the medial epicondyle at one end and over the head of
        the olecranon at the other end of the transducer. A high-frequency (8.5
        MHz) linear transducer was used. The elbow at the level of the cubital
        tunnel was examined initially in extension and then in flexion. The
        patient was made to externally rotate his shoulder for optimal
        visualisation of the cubital tunnel. Dynamic US of the tunnel was
        performed while flexing the elbow. Comparison was made with the
        asymptomatic right elbow. Care should be taken not to exert too much
        pressure with the probe as this will prevent dislocation.1
    

    
    

    
        Findings
    

    With the arm in extension, the ulnar nerve was
    noted in the cubital tunnel and the adjacent triceps muscle was in the
    expected normal position posterior to the apex of the medial epicondyle
    on extension (Figs 1 and 2). The site of the common origin of the
    flexor muscles of the forearm was identified at the apex of the medial
    epicondyle. There was no significant difference in the cross-sectional
    diameter of the ulnar nerves in comparison on extension measured at the
    level of the medial epicondyle. In the symptomatic left elbow,
    following flexion, the ulnar nerve dislocated over the medial
    epicondyle and lay anteromedially. The triceps muscle was also noted to
    dislocate and move over the medial epicondyle (Figs 3 and 4). The ulnar
    nerve and adjacent triceps remained stable in the asymptomatic right
    side (Fig. 5). There was separation of the ulnar nerve from the triceps
    while dislocating over the apex of the medial epicondyle. This
    phenomenon was well demonstrated using dynamic extension followed by
    flexion with the transducer held firmly with respect to the medial
    epicondyle continuously monitoring the movement in the cubital tunnel.
    The moment of dislocation of the ulnar nerve and triceps over the
    medial epicondyle that be felt by the patient as a snapping senstion
    was also noted by the observer. After flexion, the cross-sectional
    appearance of the dislocated ulnar nerve over the medial epicondyle
    appeared elongated and obtained a flattened shape instead of its normal
    rounded appearance in the cubital tunnel (Fig. 4). After extension, the
    ulnar nerve and triceps were noted to revert back to their respective
    normal positions and morphology in the cubital tunnel.

    The US findings were consistent with ulnar nerve
    dislocation and associated triceps snapping syndrome. Nerve conduction
    studies were positive for ulnar neuropathy at the elbow.

    The patient was initially managed
    conservatively on an analgesic regime but did not show significant
    clinical improvement, and subsequently underwent surgery.
    Intra-operatively, on passive flexion and extension of the elbow, the
    ulnar nerve as well as the medial head of the triceps were noted to
    dislocate over the medial epicondyle, confirming the diagnosis. The
    ulnar nerve was transpositioned anteriorly and the medial head of the
    triceps was transpositioned laterally by the orthopaedic surgeon. On a
    post-surgery follow-up at 6 months, the patient reported significant
    relief from the symptoms.

    Discussion

    Cubital tunnel syndrome is a concise term for
    conditions that result in strain on the ulnar nerve at the elbow.
    Patients with this condition typically complain of pain and tingling
    numbness in the distribution of the ulnar nerve, exaggerated on flexion
    of the elbow.2  One of the
    possible causes for cubital tunnel syndrome is ulnar nerve dislocation,
    which may be associated with triceps snapping syndrome. In this
    condition, the ulnar nerve dislocates over the medial epicondyle
    following flexion of the elbow which may or may not be accompanied by
    triceps dislocation. As the elbow moves from extension to flexion, the
    distance between the medial epicondyle and the olecranon increases by 5
    mm for every 45° of elbow flexion. The cubital tunnel’s loss
    in height with flexion results in a 55% volume decrease in the canal,
    which doubles the mean ulnar intraneural pressure.3
    ,
    4 
    Subluxation of the nerve is common, and not every individual with this
    condition is symptomatic. Friction generated with repeated subluxations
    may cause inflammation within the nerve and, in the subluxed position,
    the nerve may be more susceptible to inadvertent trauma.5
    ,
    6


Congenital absence of the cubital tunnel
retinaculum, a fibrous band extending from the olecranon process to the
medial epicondyle and forming roof of the cubital tunnel, is thought to
be one of the causes of ulnar nerve dislocation with triceps snapping.7  Other possibilities include bodybuilding, post-trauma effects, congenital accessory triceps tendon and abnormal medial triceps.8


Dynamic US can help to demonstrate abnormal
dislocation of the ulnar nerve, with and without snapping triceps
syndrome through continual visualisation of the ulnar nerve and triceps
muscle in active elbow flexion and extension.1 
Knowledge of this condition and the relevant anatomy is essential for
diagnosis and for musculoskeletal US in general. The condition can also
be demonstrated through MRI and CT,9 
which requires imaging the limb in static extension and flexion to
diagnose the dislocation. However US is a cost-effective modality which
has the superior advantage of demonstrating the condition dynamically.
Additionally, the snapping sensation on dislocation can be actively
appreciated on US by the examiner.

The technique for an US diagnosis of ulnar nerve
dislocation and triceps snapping requires identification of the apex of
the medial epicondyle as a landmark.1 
On extension, the ulnar nerve is located posterior to the epicondyle
which dislocates over it on flexion,reverting to its original position
on extension. If the medial head of the triceps also dislocates over
the medial epicondyle, triceps snapping is also associated, which may
be felt as two snaps: the first when the ulnar nerve dislocates,
followed by a second snap upon triceps dislocation. If the medial head
of the triceps does not dislocate, isolated dislocation of the ulnar
nerve should be considered. US findings suggest that dislocation is
diagnosed conclusively on flexion. As appreciated in this case, it has
been shown that the ulnar nerve flattens during elbow flexion, and this
flattening is most marked with ulnar nerve subluxation.10


Treatment for this condition depends on symptom
severity. For milder cases, conservative treatment including
physiotherapy and avoiding activities involving repeated flexion and
extension may suffice. Patients with persistent or severe symptoms may
require surgery such as lateral repositioning, medial epicondylectomy
or anterior transposition of the ulnar nerve.6
,
9






    Acknowledgements.
    We thank Dr Ajit Patil, the orthopaedic surgeon managing this case, for
    his co-operation; Miss Geeta Awate, General Manager, Apple Hospital,
    for her keen interest in research projects at the institute; Dr V
    Degaonkar for his invaluable guidance; and Mr Yuvraj Shinde for his
    contribution in preparing the manuscript and images.

    
    

    1. Jacobson JA, Jebson PJ, Jeffers AW, Fessell DP, Hayes CW. Ulnar
    nerve dislocation and snapping triceps syndrome: Diagnosis with dynamic
    sonography – report of three cases. Radiology 2001;220(3):601-605.

    1. Jacobson JA, Jebson PJ, Jeffers AW, Fessell DP, Hayes CW. Ulnar
    nerve dislocation and snapping triceps syndrome: Diagnosis with dynamic
    sonography – report of three cases. Radiology 2001;220(3):601-605.

    2.	Cubital Tunnel Syndrome, Information for Public And Patients. Rosemont, IL: American Society for Surgery of the Hand, 2011.

    2.	Cubital Tunnel Syndrome, Information for Public And Patients. Rosemont, IL: American Society for Surgery of the Hand, 2011.

    3. Watchmaker GP, Lee G, Mackinnon SE. Intraneural topography of the
    ulnar nerve in the cubital tunnel facilitates anterior transposition. J
    Hand Surg [Am] 1994;19(6):915-922.

    3. Watchmaker GP, Lee G, Mackinnon SE. Intraneural topography of the
    ulnar nerve in the cubital tunnel facilitates anterior transposition. J
    Hand Surg [Am] 1994;19(6):915-922.

    4. Pechan J, Julis I. The pressure measurement in the ulnar nerve. A
    contribution to the pathophysiology of the cubital tunnel syndrome. J
    Biomech 1975;8(1):75-79.

    4. Pechan J, Julis I. The pressure measurement in the ulnar nerve. A
    contribution to the pathophysiology of the cubital tunnel syndrome. J
    Biomech 1975;8(1):75-79.

    5.	Childress HM. Recurrent ulnar-nerve dislocation at the elbow.Clin Orthop 1975;108:168-173.

    5.	Childress HM. Recurrent ulnar-nerve dislocation at the elbow.Clin Orthop 1975;108:168-173.

    6. Verheyden JR, Palmer AK. Cubital tunnel syndrome. Medscape, June
    2011. http://emedicine.medscape.com/article/1231663-overview#a0104
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    6. Verheyden JR, Palmer AK. Cubital tunnel syndrome. Medscape, June
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    7. O’Driscoll SW, Horii E, Carmichael SW, Morrey BF. The cubital
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    7. O’Driscoll SW, Horii E, Carmichael SW, Morrey BF. The cubital
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    8. Spinner RJ, Goldner RO. Snapping of the medial head of the triceps
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    1998;80:239-247.

    8. Spinner RJ, Goldner RO. Snapping of the medial head of the triceps
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    9.	Spinner RJ, Hayden FR, Hipps CT, Goldner RD. Imaging of snapping triceps. Am J Roentgenol 1996;167:1550-1551.

    9.	Spinner RJ, Hayden FR, Hipps CT, Goldner RD. Imaging of snapping triceps. Am J Roentgenol 1996;167:1550-1551.

    10. Okamoto M, Abe M, Shirai H, Ueda N. Morphology and dynamics of the
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    Hand Surg [Br] 2000;25:85-89.




    




    
        
    

    
        Fig. 1. The asymptomatic right elbow at the level of
        the cubital tunnel. The elbow is in extension. The ulnar nerve
        (arrowhead) and the medial head of the triceps muscle (TR) are in the
        cubital tunnel posterior to the apex of the medial epicondyle (ME). The
        common origin of the flexor muscles (FE) of the forearm is visualised
        at the apex of the medial epicondyle. One end of the transducer is at
        the medial epicondyle and the other at the head of the olecranon (OL).

        
        

    




    
        

    




    
        
    

    
        Fig. 2. The symptomatic left elbow at the level of
        the cubital tunnel in extension. The ulnar nerve (arrowhead) and the
        medial head of triceps (TR) are in the cubital tunnel posterior to the
        medial epicondyle (ME) similarly to the anatomy of the extended right
        elbow. Note the round contour of the cross-section of the ulnar nerve.

    




    
        
            

        

    

    
        
        

        Fig. 3. The symptomatic left elbow at the level of the cubital tunnel
        in mid-flexion. The ulnar nerve (arrowhead) has moved over the medial
        epicondyle (ME). Note the flattening of the contour of the ulnar nerve.
        In addition, the medial head of the triceps (TR) has moved towards the
        medial epicondyle.
        				

    

    
        
            
                

            

        

        
            
            

            Fig. 4. At full flexion, the ulnar nerve along with the medial head of
            the triceps have dislocated (shown by the arrowhead) over the medial
            epicondyle (ME). The dislocation was perceived as a snapping sensation
            felt through the transducer.
            				

        

        
            
                
            

            
                Fig. 5. The asymptomatic right elbow at the level of
                the cubital tunnel is depicted at full flexion following continuous
                dynamic monitoring by keeping the transducer fixed over the medial
                epicondyle (ME) during flexion. The ulnar nerve (arrowhead) and medial
                head of triceps (TR) remain in the cubital tunnel posterior to the
                medial epicondyle with no evidence of dislocation.