Nerve conduction study of ulnar nerve in volleyball players

A. Ozbek1, B. Bamac

1, F. Budak

2, N. Yenigun

3, T. Colak

1

1School of Medicine, Department of Anatomy, 2Department of Neurology, 3School of Physical Education and Sports, KocaeliUniversity, Kocaeli, TurkeyCorresponding author: Belgin Bamac, PhD, PT, Department of Anatomy, School of Medicine, Kocaeli University, Derince,41900 Kocaeli, Turkey. Tel: 190 –262 233 59 80/1237, Fax: 190 –262 322 21 40, E-mail: bbamac@hotmail.com

Accepted for publication 19 April 2005

Ulnar neuropathy at the elbow is a common disorder seen inthe throwing athlete. The purpose of our study was todetermine whether asymptomatic physically active volley-ball players and non-actives demonstrate distinct differencesin nerve conduction of the ulnar nerve at the elbow. Nerveconduction studies were performed on both arms of 24 malevolleyball players and 24 male non-actives. Nerve conduc-tion velocity at the above to below elbow segment of theulnar motor nerve were slower in the volleyball playerscompared with controls and their non-dominant arms. There

were no statistical differences in latencies and conductionvelocity of the ulnar nerve on the forearm, both in volleyballplayers and in the controls. In the evoked responses of theulnar nerve, the amplitude was the same as correspondingnormal values in both sensory nerve and muscle actionpotentials. We conclude that abnormal ulnar (motor) nerveconduction at the elbow segment may suggest a subclinicalentrapment neuropathy as a result of strenuous elbowmovements in volleyball players.

Volleyball imposes a high-impact and weight-bearingload upon the upper extremity. Movements on thecourt and the skills used in playing are performedrepetitively throughout the season. This repetitioncontributes to injuries. Overuse injuries are morecommon in competitive athletes who practice foryears on sport-specific skills (Schutz, 1999). Repeti-tive stress on the dominant extremities of volleyballplayers is responsible for physiological and patholo-gical changes in the dominant shoulder and elbow(Bamac et al., 2003). Peripheral nerve entrapment isone of them. High-velocity arm swing, nerve stretchand stressful deceleration required during spikingand several different ball-striking activities are con-sidered the most common causes of the nerve injury(Khan et al., 2001). In the volleyball players, nerveinjuries to the shoulder have been reported before(Ferreti et al., 1987; Schutz, 1999; Witvrouw et al.,2000). Although ulnar neuropathy at the elbow is acommon disorder seen in the overhand throwingathlete (Glousman, 1990), nerve injuries to the elbowhave not been reported in volleyball players.The nature of the game plays an important role in

the pathogenesis of nerve lesions. Looking at move-ments specific to volleyball, the only two asymme-trical and powerful movements typical of the gameare service and spike (Witvrouw et al., 2000). It hasbeen shown that volleyball maneuvers such as ser-

ving and spiking require a strenuous unilateral actionof the dominant upper extremity (Schutz, 1999;Khan et al., 2001).Various factors such as high repetition of motions,

high muscular forces and extreme elbow positionsaffect the peripheral nervous system with or withoutsigns and symptoms. This is reason to believe thatmany neurological injuries remain subclinical and arenot recognized before neurological damage is perma-nent. Identification of nerve injuries needs an under-standing of their common sites in volleyball.Therefore, it is the purpose of this study to evaluatethe influence of playing volleyball on the ulnar nervecrossing the elbow region.

Materials and methods

The volleyball group consisted of 24 first-division male volley-ball players (age 23.7 � 7.32 years). They had been activein high-level volleyball for 4.7 (2–8) years, and practiced8 h/week, 40 weeks/year. During off-season, they trainedwith weights 1–2 h/week and playing beach volleyball duringweekends. The control group consisted of 24 non-active male(age 24.6 � 8.35 years) not participating in any kind of regularor organized sport activity. Initially, 27 volleyball playersvolunteered to participate. Of these, three athletes wereexcluded because of pre-existing musculo-skeletal injuries(n5 2) and peripheral neuropathy (n5 1). The control groupwas derived from a random selection of students from School

Scand J Med Sci Sports 2006: 16: 197–200 COPYRIGHT & BLACKWELL MUNKSGAARD 2005

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of Medicine. Inclusion in this group required no prior historyof upper extremity dysfunction and no peripheral neuropathy.Before participation, informed consent was obtained fromeach subject. All were examined at the University HospitalKocaeli, Turkey.

Muscle strength was determined by resisted manual muscletesting. Subjects were tested by the same investigator (B.Bamac, physical therapist).

No subluxation of the ulnar nerve out of the cubital tunneloccurred, evaluated by palpation of the nerve above themedial epicondyle.

The neurophysiological study consisted of motor and sen-sory nerve conduction of the ulnar nerve. The nature of theprocedure was explained to the subjects. They lay supine on apadded table with the upper limb supported. Comparablevalues for maximal motor conduction velocity across the elbowand in the forearm were obtained when the elbow was in theflexed position. All the studies were performed in a warm roomwith the temperature maintained at 26–28 1C. Skin temperatureof the upper limb was checked to eliminate the influence oftemperature on the conduction parameters. If necessary, thelimb was warmed with the aid of an infra-red heat lamp tomaintain the temperature of 32 1C or more. In an effort toreduce diurnal variation, all measurements were made atapproximately the same time of the day for each subject. Theintercathodal distances were measured with an anthropometer.Both dominant and non-dominant extremities of all subjectswere tested by a neurologist using a Medelec Saphire Electro-myograph (Medelec, Woking, UK). The electrophysiologicstudy was conducted according to the American Associationof Electrodiagnostic Medicine (AAEM) practice guidelines.

Nerve conduction studies were performed using standardtechniques of supramaximal percutaneus stimulation with aconstant current stimulator and surface electrode recording onboth extremities of each subject. Sensory responses wererecorded antidromically. The ulnar nerve was stimulated atthe wrist, and the sensory response was recorded from the littlefinger with ring electrodes.

The results of the ulnar motor nerve were obtained bystimulating the ulnar nerve at the wrist, below the elbow (5 cmbelow the medial epicondyle) and above the elbow (6 cm abovethe tip of the medial epicondyle) with bipolar surface electrodes.The motor response was recorded with surface electrodes fromabductor digiti minimi muscle with the forearm flexed at 901.

In the present study, the following ulnar nerve measureswere used: (1) baseline-to-peak amplitude of the sensory nerveaction potential (Amp-S), (2) distal peak latency of the sensorynerve action potential (DL-S), (3) conduction velocity of thesensory nerve fibers (CV-S), (4) baseline-to-peak amplitude ofthe compound muscle action potential (Amp-M), (5) distalonset latency of the compound muscle action potential (DL-M), (6) conduction velocity of the motor nerve fibers (CV-M)(below elbow to wrist) and (7) conduction velocity of themotor nerve fibers (CV-M) (above elbow to below elbow).Latency was calculated from the start of the electrical artifactto the first positive peak of the nerve potential.

When performing nerve conduction studies, the observerswere not blinded to the subject’s volleyball-playing habits.

The results are presented as means � SD. Differences be-tween the groups were calculated using a non-parametric testfor independent samples (Mann–Whitney U-test). The SPSSpackage (Statistical Programs for Social Sciences, Chicago,Illinois, USA) for personal computer was used for the statis-tical analyses. A P-value of less than 0.05 were consideredsignificant.

This study was conducted according to the guidelines ofthe Declaration of Helsinki, and was approved by the ethicscommittee of our faculty.

Results

Two groups of subjects were examined. Table 1displays the physical characteristics of volleyballplayers and controls. There were no significantdifferences between controls and volleyball playerswith respect to their physical characteristics.On physical examination, each athlete had normal

results for the range of motion of the upper extre-mity. There was no history of significant injury orpain. There was no weakness in the ulnar innervatedmuscles. In the evaluation of the elbow, there was nosubluxation of the ulnar nerve.The motor conduction velocity of the ulnar nerve

at the above elbow to below elbow segment wassignificantly delayed in the dominant arms of volley-ball players compared with their non-dominantarms and with controls (Po0.05). The distal laten-cies, amplitude and conduction velocity of the ulnarmotor nerve on the forearm were not significantlydifferent in the dominant arms of volleyball playerscompared with their non-dominant arms and controlsubjects (Table 2). There were no statistical differ-ences in conduction velocities, latencies and ampli-tudes of the ulnar sensory nerve between the controlgroup and volleyball players in both dominant andnon-dominant arms.

Discussion

The ulnar nerve arises from the medial cord of thebrachial plexus. The nerve courses along the medialhead of triceps in the upper arm. At the elbow, it liesbehind the medial epicondyle of the humerus. Dis-tally, the nerve passes through the cubital tunnel,which is a fibro-osseous canal. It then runs down theforearm and enters the palm of the hand (Apfelberg& Larson, 1973; Snell, 1995).The ulnar nerve may be compressed at any point in

its course, from the axilla to the hand. Even with anormal range of motion, the ulnar nerve approachesstrain levels that could potentially create directmechanical problems, electrophysiologic effects and/or a blood supply problem. Lesions of the ulnarnerve occur most commonly in the region of theelbow joint as the nerve runs in the groove behind themedial epicondyle and descends in the cubital tunnel

Table 1. Comparison of the physical characteristics of controls and

volleyball players

Controls (n 5 24) Volleyball players (n 5 24) P

Age (years) 24.6 � 8.35 23.7 � 7.32 0.193Height (cm) 192.5 � 9.3 196.0 � 10.3 0.09Weight (kg) 85.8 � 6.9 87.1 � 5.7 0.12

Values are given as mean � SD.

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(Khoo et al., 1996; Aminoff, 1998; Wright et al.,2001). There are numerous causes of ulnar neuro-pathy at the elbow in the athletes. Because of theintensity of sporting activities and the biomechanicsinvolved, the athlete tends to develop ulnar nerveirritation from mechanical sources: compression,traction and friction. Compression of the ulnar nerveis often caused by hypertrophy of the surroundingsoft tissues. Friction may develop from subluxationor dislocation of the nerve because of congenitalor developmental laxity of the soft-tissue restraintsthat normally hold the ulnar nerve in its groove atthe cubital tunnel. Traction of the nerve can occurbecause of the valgus forces that occur with throwing(Safran, 1995; Wilk et al., 2003). Repetitive flexionand extension of the elbow with an unstable nervecan irritate or inflame the nerve. Any factor thatlimits normal excursion at the elbow may play a rolein the pathophysiology of the nerve. Specific posi-tions of the upper extremity can lead to increasedstrain in the ulnar nerve. In previous studies (Apfel-berg & Larson, 1973; Khoo et al., 1996; Bozentka,1998; Wright et al., 2001; Byl et al., 2002), increasedcubital tunnel pressures with elbow flexion have beenreported. Excursion of the nerve at the elbow isfurther increased when the shoulder is placed inabduction, and the wrist and fingers in extension(Wright et al., 2001). Although these positions areusually held only for brief periods, cumulative da-mage may result in a nerve injury.Volleyball can repetitively stress the elbow and

shoulder because of repetitive overhead throwing.The biomechanics of throwing can be applied tovolleyball spiking and serving. The spiking motionis typically broken down into three phases: cocking,acceleration and deceleration. The cocking phaseends at approximately 901 of abduction and maximalrotation of the glenohumeral joint (Khan et al.,2001). Kinetic research has shown excessive valgusimparted to the medial elbow during late cocking andacceleration phases of throwing (Maloney et al.,

2002; Wilk et al., 2003). Continued valgus andextension forces and subtle laxity may also causeexcessive medial soft-tissue stretch, resulting in trac-tion injury to the ulnar nerve and eventually apathologic condition, ulnar neuropathy (Cain et al.,2003).Our results were considered valid evidence of

subclinical entrapment in apparently unaffected vol-leyball players. These results showed that the volley-ball players have a tendency toward having ulnar(motor) nerve damage in the elbow region althoughthey were asymptomatic. Findings in the volleyballplayers’ group could have been a result of demyeliza-tion rather than axonal degeneration. Because de-layed conduction velocity indicates demyelization,this process can occur by short-term mechanicalforce, long-term mechanical force or ischemia fromentrapment. The ulnar nerve responds to increasedpressure in a dose-related manner by demonstratingaltered intraneural microvascular blood flow, axonaltransport and nerve function, thus implicating re-peated overhead throwing as a source for neuraldysfunction (McCluskey & Webb, 1999; Maloneyet al., 2002). We suggested that during the overheadthrowing motion, extreme valgus forces make theulnar nerve susceptible to traction injury as it coursesfrom the upper arm to the forearm through thecubital tunnel. However, entrapment of the nervebetween hypertrophic triceps muscle heads was alsoconsidered to be a possible reason for the abnormalconduction velocities.The findings in the present study clearly demon-

strate statistically significant differences betweendominant and non-dominant extremities in volley-ball players. The demands placed on the upperextremities in volleyball generally occur bilaterally.Nevertheless, the spike and serve motions are man-euvers that require strenuous unilateral action, typi-cally from the dominant arm (Khan et al., 2001).Our study reflected the neurophysiological changes

at rest. As the control group in our study was

Table 2. Nerve conduction results of the ulnar nerve

Variable Controls (n 5 24) Volleyball players (n 5 24)

Dominant Non-dominant P Dominant Non-dominant P

Amp-S (mV) 28.4 � 12.3 25.9 � 10.6 0.4 29.1 � 10.5 25.8 � 11.1 0.2DL-S (ms) 2.70 � 0.24 2.65 � 0.25 0.4 3.13 � 0.24 3.06 � 0.26 0.3CV-S (m/s) 52.8 � 4.0 54.1 � 4.2 0.2 53.7 � 4.8 54.7 � 5.3 0.4Amp-M (mV) 5.4 � 2.1 5.6 � 2.0 0.7 5.6 � 2.2 5.57 � 2.1 0.9DL-M (ms) 2.91 � 0.38 2.93 � 0.36 0.8 3.22 � 0.72 3.36 � 0.78 0.5CV-M (m/s) (below elbow to wrist) 56.9 � 5.4 57.1 � 5.3 0.8 57.1 � 5.3 56.4 � 5.2 0.6CV-M (m/s) (above elbow to below elbow) 61.4 � 4.9 61.1 � 5.1 0.8 57.5 � 5.8* 60.4 � 5.4 0.04

Values are given as mean � SD. Amp-S, baseline-to-peak amplitude of the sensory nerve action potential; DL-S, distal peak latency of the sensory nerve

action potential; CV-S, conduction velocity of the sensory nerve fibers; Amp-M, baseline-to-peak amplitude of the compound muscle action potential; DL-

M, distal onset latency of the compound muscle action potential; CV-M, conduction velocity of the motor nerve fibers.*Significantly different than the dominant arm of the controls (P 5 0.01).

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inactive, standard conditions as those of the volley-ball players after the activity could not be achieved.Therefore, the study was performed in the restingposition.In the present study, many of the asymptomatic

volleyball players with slowing nerve conductiontests may represent presymptomatic or asympto-matic neuropathy similar to the type of subclinicalentrapment neuropathy. We propose that excursionof the nerve at the elbow with repetitive motion ofupper extremity and abnormal elbow mechanicsmakes the volleyball player vulnerable to ulnar nervedisorders. The physician should be aware of thepossible occurrence of neuropathies. In the evalua-tion of volleyball players with elbow complaint,physical examination should include inspection ofcarrying angle and palpation of the ulnar nervebecause increased valgus deformity may result in alengthened ulnar nerve course and increased suscept-ibility to traction injury. In conclusion, an under-standing of the injury mechanisms and risk factors is

important for training and rehabilitation in volley-ball.

Perspectives

It is well known that playing volleyball producessignificant stresses in the elbow region during volley-ball maneuvers such as serving and spiking. Thisstudy demonstrated that excessive upper extremitymovements may place volleyball players at a greaterrisk of developing ulnar neuropathy. However, theseresults must be interpreted with caution. The smallsample size limits the possibility of drawing definiteconclusions. This study can be considered as a pilotstudy for more extensive investigations into the exactrelation between excessive upper extremity motionand the presence of subclinic ulnar neuropathy involleyball players.

Key words: elbow, overuse, injury, valgus stress.

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