Ulnar Neuropathy in the Distal Ulnar nerve lesions

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Ulnar Neuropathy in the Distal UlnarTunnelDAVID W SHUPE, PT, ATC

A brief anatomical review of the ulnar nerve and areas of ulnar nerve entrapmentis discussed. The importance of the dorsal cutaneous nerve is presented with regard tolocalizing a lesion to the ulnar nerve in the forearm. A classification system isdescribed for ulnar entrapment that occurs distal to the wrist. The case of a nine-year-old girl with a fibrous entrapment of the ulnar nerve in the distal ulnar tunnel ispresented . The clinical and diagnostic procedures required for localizing the level ofthe ulnar nerve entrapment are described along with the operative findings of thiscase report.

When evaluating and treating patients withtrauma to the upper extremity, a vital part of theassessment is the basic neurological examination.One component of this examination is the evalu-ation of peripheral nerve function. If ulnar nerveinvolvement is suspected, then particular assess-ment of this nerve is warranted. Conclusions de-rived from this assessment will allow the physicaltherapist to develop more realistic treatment goalsand to enhance communication with patients andothers in the medical community.The purpose of this article is to give a briefanatomical review of the ulnar nerve and potentialareas of ulnar nerve entrapment, with emphasison the distal ulnar tunnel. A case report of apatient with a fibrous entrapment of the ulnarnerve in the distal ulnar tunnel is presented.ANATOMY OF THE ULNAR NERVEAn anatomical review of the ulnar nerve showsthat after originating from the medial cord of thebrachial plexus, it descends along the medial as-pect of the arm with the median nerve. In thedistal aspect of the arm, it becomes more super-ficial after passing through the intermuscular septum of the triceps brachii Arcade of Struthers).At the elbow, the nerve passes through a fibro-osseous tunnel, known as the cubital tunnel. Lat-erally, this tunnel is bordered by the elbow joint,

Director. wrtsmedCenter.325 N.25th Street. Lafavette. IN 47904.0190-601 PI11 01 OOO6 03.OO/OTHEJOURNALF ORTHOPAEDICND SPORTSPHYSICALHERAWCopyight 991 by The OrWqwdc and Sports PhysicalTherapyS e c t i s of th Americen Physical Therapy ssociat i

medially by the heads of the flexor carpi ulnaris,and anteriorly by the medial epicondyle 1).After passing through the cubital tunnel. thenerve enters the forearm, taking a less superficialcourse when it descends between the two headsof the flexor carpi ulnaris muscle 7).The ulnarnerve then takes a straight course along the me-dial aspect of the forearm after giving muscularbranches to the flexor carpi ulnaris and the flexordigitorum profundus to the ring and little fingersbarring any anomalies). It is important to notethat entrapments may occur at the Arcade ofStruthers, in the cubital tunnel, and within thefibrous tunnel formed by the two heads of theflexor carpi ulnaris.Approximately eight to ten centimeters prox-imal to the ulnar styloid process, the dorsal cuta-neous nerve branches from the ulnar nerve Figure1).Four to five centimeters proximal to the styloidprocess, the dorsal cutaneous nerve crosses themedial aspect of the ulna to take a position dorsalto the ulna 4, 7). This branch provides sensoryinnervation to the ulnar portion of the dorsum ofthe hand and parts of the dorsal aspect of thelittle and ring fingers Figure 2).The ulnar nerve enters the hand through thedistal ulnar tunnel 2, 5). This tunnel is four to fourand one-half centimeter long, beginning at theproximal edge of the palmar carpal ligament andextending to the fibrous arch of the hypothenarmuscles Figure 3). As described by Gross andGelberman 2), the roof of the tunnel from proximalto distal is composed of the palmar carpal liga-ment, palmaris brevis muscle, and hypothenar fatand fibrous tissue. Kleinert and Hayes 5) reportedthat this roof is multilayered, with the palmar

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carpal ligament blending distally with the hypoth-enar fascia, radially with the palmar aponeurosis,and proximally with the volar forearm fascia.The floor of the tunnel is formed by thetendons of the flexor digitorum prcifundus, thetransverse carpal ligament, the pisohamate andpisometacarpal ligaments, and the opponens digitiminimi 2). The flexor carpi ulnaris, the pisiform,

DorsalCutaneous Branch

Ulnaris

Figure 1. Course of the dorsal cutaneous nerve.

and the abductor digiti minimi comprise the ulnarwall. The radial wall is formed by the tendons ofthe extrinsic flexors, the transverse carpal liga-ment, and the hook of the hamate. Along with theulnar nerve, the ulnar artery lies within the distalulnar tunnel.Within the distal ulnar tunnel, the ulnar nervedivides into a superficial branch and a deep branch5). The superficial branch supplies the skin onthe palmar aspect of the little finger and the medialhalf of the ring finger. Motor fibers to the palmarisbrevis also take their origin from the superficialbranch. After innervating the abductor digiti min-imi, flexor digiti minimi, and opponens digiti minimimuscles, the deep palmar branch turns laterallyto supply the dorsal and palmar interossei, thethird and fourth lumbricals, the adductor pollicis,and the deep head of the flexor pollicis brevismuscles.In their anatomical study of the distal ulnartunnel, Gross and Gelberman 2)used an anatom-ical basis for dividing the tunnel into three zones.

Zone one is the portion of the tunnel proximal tothe bifurcation of the nerve. Any lesion of the ulnarnerve in this zone would lead to both motor andsensory deficits. Zone two encompasses thedeep motor branch of the nerve. Any involvementof the nerve in this zone would lead to motordeficits only. The superficial branch is located inzone three. Any lesion at this level would lead tosensory involvement and a motor deficit of thepalmaris brevis.

Figure 2. Sensory distribution of the dorsal cutaneous branch of the ulnar nerve.

SENSORY ND MOTOR EV LU TIONUnderstanding the distribution of the dorsal cuta-neous branch of the ulnar nerve is extremelyimportant in helping to differentiate the approxi-mate level of any lesion of the ulnar nerve in thedistal one-half of the forearm. Any problem prox-imal to the dorsal cutaneous branch would resultin a sensory disturbance to the dorsal and ulnaraspect of the hand, parts of the dorsal aspect ofthe ring and little fingers, and a sensory deficit onthe palmar surface of the little finger and medialaspect of the ring finger. A lesion distal to theorigin of this small cutaneous branch would onlyproduce a sensory deficit in the little finger andmedial aspect of the ring finger 7). Regardless ofwhere an ulnar nerve lesion in the distal forearmwould be located, the same motor deficit wouldexist.A thorough assessment of the motor functionof the hand, fingers, and thumb is an essentialcomponent of the evaluation process. Along withany functional tests, a detailed manual muscletest should always be performed. Strength defi-cits in the hand muscles innervated by the ulnarnerve can result directly from an ulnar motorbranch dysfunction as discussed. However, these

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Opponens Digiti MinimiFlexor Digiti Minimi

Superficial BranchDeep Branch Ulnar Nerve

Abductor Digiti MinimiHamate

Pisohamate LigamentTransverse CarpalLigamentPalmar CarpalLigament Flexor Carpi U lnaris

strength deficits may also arise from othersources that should not be ignored, even in thepresence of known trauma to the ulnar nerve.Other sources of dysfunction may include motorneuron diseases, nerve root compression, bra-chial plexopathy from various etiologies, diseasesof peripheral nerves, mechanical abnormalities asa result of a disease process, and nerve entrap-ments (3).C SE REPORTA nine-year-old girl fell from a balance beam duringgymnastics practice. She landed on her right handwith the wrist extended and the elbow in a fullyextended position (Figure 4). Immediate pain anddisability were reported in the right elbow. Afterx-ray examination revealed a displaced fractureof the medial epicondyle of the right humerus, anopen reduction and internal fixation of the dis-placed fragment were performed (Figure 5). Sta-bilization was maintained with percutaneous pin-ning, and a posterior plaster splint was appliedwith the elbow at 60' of flexion.After five weeks, the Steinman pins wereremoved and the patient was referred to physicaltherapy for rehabilitation. Active range of motion(AROM) of the right elbow was 50-1 05'; supina-tion was 0-45'; and pronation was 0-73'. AnAROM and gravity-assisted, static-stretching pro-gram was begun.At the seventh postoperative week, elbowAROM was 48-1 13O, with supination and prona-tion showing normal ROM measurements. Thepatient, now less focused on the elbow, reported

that her ring and little fingers 'felt cold at times.Examination of the right hand revealed an abnor-mal resting finger position that consisted of claw-ing of the fourth and fifth fingers 6). Atrophy ofthe intrinsic hand muscles innervated by the ulnarnerve was noted. Trophic changes were presentin the ring and little fingers, consisting of a white,leathery appearance to the skin and a brittie,ridged look to the nails.A sensory evaluation was normal to lighttouch and pinprick. Two-point discrimination wasalso normal at five millimeters. Manual muscletesting revealed normal function of all musclesinnervated by the median nerve. Normal functionof the flexor carpi ulnaris and flexor digitorumprofundus to all fingers was present. No functionof the intrinsic hand muscles innervated by theulnar nerve was noted, although a minimal degreeof abduction of the little finger was present. Thiswas in the presence of no palpable contractionof the abductor digiti minimi and was thoughtto have resulted from aponeurotic attachmentsfrom the flexor carpi ulnaris to the abductor digitiminimi.Finger tip prehension (thumb to index) waspossible, but lateral prehension was not. A nega-tive Tinel's sign was present at the elbow andwrist over the ulnar and median nerves. Markedtenderness was found with palpation in the areaof the hook of the hamate. A positive Tinel's signwas also present at this location. These findingswere documented and reported to the referringphysician.After carpal tunnel views of the right wristruled out a fracture of the hook of the hamate (6),

Figure3 Diagramo the distal ulnar tunnel

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Figure 4. Mechanism of injury for nine-yearsld pa-tient in case study.

the decision was made in favor of nonsurgicalmanagement to see if spontaneous recovery offunction would occur.At five months postinjury, ROM measure-ments of the right, elbow, along with supinationand pronation of the forearm, were normal. Theneurological status, however, remained un-changed. At this time, further evaluation was re-quested by her physician.Motor and sensory nerve conduction studiesof the right median nerve were normal. Ulnar nerve

studies using a needle electrode showed noresponse from the abductor digiti minimi or thefirst dorsal interosseous muscles. No evoked sen-sory action potential was elicited when recordingfrom the little finger using an antidromic testingtechnique.Ulnar sensory testing for the dorsal cuta-neous nerve showed significant slowing, with theamplitude of evoked sensory action potentialsomewhat decreased compared to the contralat-era1 side. Over a six centimeter segment, thelatency on the left was 1.8 msec with an amplitude

Figure 5. Postoperative radiographs of right elbow:A lateral view; B anterior-posterior view.of 21.0 pV. The values on the right were 4.2 msecand 11.3 pV, respectively.This was a somewhat surprising finding sincesensory testing of the dorsal cutaneous nervewas normal. The slowing, thought to result froma retrograde demyelination rather than from amore proximal process, seemed to be supportedby the electromyographic EMG) findings.Electromyographic sampling of the right a bductor pollicus brevis and the flexor carpi ulnarismuscles showed normal, insertional activity withelectrical silence at rest. Motor units were normalfor shape, amplitude, and duration, and there wasa normal interference pattern in the abductor pol-licus brevis with a slightly reduced interferencepattern in the flexor carpi ulnaris. The decreasedinterference pattern in the flexor carpi ulnaris wasassociated with subjective complaints of pain atthe sampling site.When the abductor digiti minimi and the firstdorsal interosseous muscles were sampled, min-imal insertional activity with 2+ denervation po-tentials at rest was noted in both muscles. No

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motor units were located at multiple samplingsites in either of the latter muscles.

A surgeon localized the ulnar nerve lesionand performed surgery at a level distal to thewrist. The hook of the hamate was found to bestable, but a significant fibrosis of the motorbranch of the ulnar nerve and a lesser degree offibrosis of its sensory branch was observed.Dissection, release of the entrapment, and anexternal neurolysis were performed in all threezones (2).

At two weeks postsurgery, the patient re-ported that the fourth and fifth fingers feltwarmer. According to the surgeon, some inter-ossei muscle function was noted at four weeksfollowing surgery. After this time, objective infor-mation and the opportunity for further evaluationof the patient were no longer available to theauthor. However, at four months postsurgery,an uncomplicated recovery was reported by thesurgeon.

SUMM RYPeripheral nerve njury can bea common sequelaein trauma involving the upper extremity. Recog-nizing an orthopaedic injury and its soft tissueand/or neurological components is critical. Neu-rological assessment should be a routine part ofa thorough physical therapy examination in anyorthopaedic and sports rehabilitation practice.

Appreciation s extended to Hospital Services. Inc. for all o th irassistance.

REFERENCES1. Green DP: Operative Hand Surgery. d 2. Churchill/Livingstm:New York 19822. Gross MS. Gelbennan RH:The Anatomyofth Distal Unar Tunnel.Clin Orthop 196:238-247. 19853. Hogue RE: Compression of the deep palmar branchof th ulnarnerve: case report. Phys Ther 65203-205.19854. Jabre JF: Unar nerve lesions at the wrist: new technique forrecording rom the sensory dorsal branch of the ulnar nerve.Neurology 30373-876. 19805. Klemert HE. Hayes JE: The Unar TunnelSyndrwne.Plast ReconstrSurg 47:21-24. 19716. Parker RD. Berkowitz MS. Brahrns MA. Bohl WR Hook o thharnate fractures in athletes. Am J Sports Med 14517-523. 19867. Spmner M: Injuries to the Major Branches of PeripheralNw es ofthe Forearm, pp 114-127. Philadelphia: WE Saunders

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Ulnar Neuropathy in the Distal Ulnar nerve lesions