Carpal tunnel syndrome andmotor vehicle accidentsELLIOT L. AMES, DO

Carpal tunnel syndrome can resultfrom acute injury, as indicated by a retro-spective study. Symptoms of carpal tunnelsyndrome developed in 96 patients within 2months after an automobile accident. Forty-four (46%) of these 96 patients underwentcarpal tunnel release. It is postulated that themechanism of injury is blunt trauma from thesteering wheel or dashboard.

(Key words: Carpal tunnel syndrome, auto-mobile accident, motor vehicle accident)

Carpal tunnel syndrome has become the diagnosisof the 1990s. As a result, patients often will relatethe onset of symptoms to an accident or to the tasksrequired by their occupation. Litigation and sec-ondary gain often result.

The physician treating such a patient is usual-ly placed in the position of having to determinecausality by the insurance company (defense) and thepatient's lawyer (plaintiff). Often, one side or theother will request an independent medical exami-nation. The treating physician, who is often thepatient advocate, may establish causal relationship,whereas the independent medical examiner, beingthe defense advocate, may deny a causal relation-ship. Compounding this dilemma is the fact thatcarpal tunnel syndrome often does not develop imme-diately after the accident,' and the emergency depart-ment record may not reflect a hand injury. Therefore,in this adversarial relationship, it is imperative thatthis problem be addressed objectively.

The purpose of the present study is to investi-gate the relationship and frequency of carpal tunnelsyndrome and automobile accidents.

Method and materialsThe charts of all patients with the diagnosis of carpaltunnel syndrome, seen during a 2-year period (1990

Dr Ames is a clinical assistant professor of surgery, Divisionof Orthopedic Surgery, University of Medicine and Dentistryof New Jersey–School of Osteopathic Medicine, Stratford, NJ.

Correspondence to Elliot L. Ames, DO, 1878 Route 70 East,Suite 5, PO Box 4474, Cherry Hill, NJ 08034-0681.

through 1991), were reviewed. The diagnosis was basedon history and findings of the clinical examination and elec-trodiagnostic study. A total of 335 patients, includingboth new and established patients, met the diagnosticcriteria for inclusion. There were 243 female and 92 malepatients, with a mean age of 45 years (range, 17 to 58years). Ninety-six (29%) of these patients reported hav-ing been involved in a motor vehicle accident; 75 werewomen and 21 were men. Electrodiagnostic studies werepositive in 64 (67%) of the 96 patients. Treatment protocolconsisted of splinting and steroid injection into the carpaltunnel, unless declined by the patient. If thenar atrophywas present, surgery was advised. Among the total group,156 (47%) patients underwent carpal tunnel release,whereas 44 (46%) of the 96 patients involved in a motorvehicle accident underwent surgery.

Associated conditions of the patients involved inmotor vehicle accidents were also noted (Table 1).

ResultsAmong the 44 patients involved in motor vehicleaccidents who underwent surgery, 32 had excellentresults; 7, good results; 3, fair results; 1, a poorresult; and 1 was lost to follow-up. The criteria usedwere based on the findings of the examination at thetime of discharge. Those patients who were com-pletely asymptomatic were considered to have an excel-lent result. If the symptoms of carpal tunnel syndromewere completely relieved, but the patient had aresidual problem (such as scar tenderness), thenthe result was considered good. If the symptomswere improved, but not completely relieved, theresult was considered fair; and, if no improvement,the result was deemed poor.

The interval between the time of the accidentand the onset of symptoms ranged from immedi-ately to 2 months postaccident. Surgery was per-formed 1.1 to 38 months postaccident.

Table 2 lists the complications in the 44 patientswho underwent surgery.

DiscussionThe carpal tunnel, trapeziometacarpal joint, andanatomic snuffbox 2,3 on the radial aspect of thewrist are in close proximity as the hand grasps thesteering wheel, and, as a result, are vulnerable dur-

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Table 1Associated Conditions in Motor Vehicle Accident

Victims With Carpal Tunnel Syndrome (n=96)

No. ofCondition patients

Cervical strain/sprain 18

Cubital tunnel syndrome 6

Cervical radiculopathy 5

Previous contralateral carpal 5tunnel syndrome

Thoracic outlet syndrome 4

Osteoarthritis 3

DeQuervain's tendinitis 2

Rheumatoid arthritis 2

Occupation-related 2

Previous symptoms 2

Head injury 2

Ulnar nerve subluxation 1

Pregnancy 1

Water retention 1

Cervical spondylosis 1

Dupuytren's contracture 1

Hand mass 1

Median nerve neuroma 1

Gout 1

Table 2Complications in Motor Vehicle Accident Victims

Who Underwent Surgery forCarpal Tunnel Syndrome (n=44)

No. ofComplication patients

Scar tenderness 9

Dupuytren's contracture 1

Weakness 1

Pisotriquetrial pain 1

ing an impact (Figures 1 and 2). These structurescan be injured when the hand is braced on the steer-ing wheel at the time of either a front- or rear-endcollision. 1-4 Trauma can exacerbate asymptomatic pre-existing arthritis, 5 and it is not uncommon to seepatients with preexisting osteoarthritis of thetrapeziometacarpal joint, or scaphoid non-union6

Figure 2. Outline of steering wheel on hands seen in Figure 1.Note proximity of the carpal tunnel and the trapeziometacar-pal joint.

become symptomatic after an accident. Becausestructures at the base of the thumb can be injuredby the steering wheel and the carpal tunnel is in closeproximity to the trapeziometacarpal joint, it is rea-sonable to assume that the carpal tunnel receivesblunt trauma at the time of impact.

Folmar and others, ? in 1972, reported that flex-or tendon injuries, especially crush injuries, maycause carpal tunnel syndrome secondary to chron-ic tenosynovitis. In 1975, Brown and Snyder 8 report-ed that 14 of 89 patients who underwent surgery forcarpal tunnel syndrome had had previous trauma,with 9 having had previous wrist injuries and 5having had flexor tendon trauma distal to the carpaltunnel.

In 1977, Guyon and Honet9 reported that of450 patients with neck pain after an automobileaccident, 4 had carpal tunnel syndrome diagnosedand 3 had trigger finger. All patients were involvedin rear-end collisions. Five of the 7 were driversof the vehicle. Of the 4 with carpal tunnel syn-drome, one gripped the steering wheel at impact,and another braced against the dashboard. Guyon

224 • JAOA • Vol 96 • No 4 • April 1996 Original contribution • Ames

Figure 3. Two methods of performing wrist flexion test with the elbow in less than90 degrees of flexion.

Figure 4. Wrist neutral test.

and Honet postulated that wrist and finger exten-sion against the dashboard or wrist and finger flex-ion while gripping the steering wheel may increasepressure in the carpal tunnel.

Finally, Haas and associates,' in 1981, report-ed the development of carpal tunnel syndrome inseven patients after a motor vehicle accident, withrelief of symptoms after surgery. They thoughtthat the mechanism for the develop-ment of the carpal tunnel syndrome inthese patients was chronic nerve com-pression from the steering wheel.

In the study reported here, 29% ofpatients with carpal tunnel syndromeseen during a 2-year period reportedbeing involved in an automobile acci-dent. This prevalence may reflect thepatient mix in the practice, referral pat-terns, and demographics. However, itis noteworthy that 67% of this grouphad positive results of electrodiagnosticstudies, and 46% of the group involvedin motor vehicle accidents underwentsurgery, with the majority thereby beingrelieved of their symptoms. This fact

would certainly support the diagnosisof carpal tunnel syndrome in the groupinvolved in motor vehicle accidents andlend credibility to the presenting com-plaints.

Patients involved in motor vehicleaccidents usually initiate litigation, withthe prospect of secondary gain. Conse-quently, the patient often demonstratesa subjective response on examinationand will respond similarly to testingfor the various compression neuropathiesin the upper extremity. 10 Therefore, itis important for the physician to dif-ferentiate subjective from objectiveresponses by use of the following clin-ical tests.

In order to isolate the median nerve,it is preferable to perform the Phalen'swrist flexion test with the elbows inless than 90 degrees of flexion to avoidpressure on the ulnar nerve at the elbow(Figure 3). If ulnar nerve entrapmentat the elbow (cubital tunnel syndrome)is suspected, then the passive elbowflexion test" and Tinel's sign at theelbow should be checked before test-ing for carpal tunnel syndrome.

An earlier publication'° describedthe wrist neutral test. To perform thistest, have the patient place his/her fiststogether, with the metacarpal headsgently interlocked and wrists in the

neutral position (Figure 4). This test is timed for 1minute, similar to the Phalen's wrist flexion test,reverse Phalen's test, and passive elbow flexiontests, and it is done after these other tests. Thewrist neutral test is considered positive when thepatient reports the onset of numbness or pares-thesia in the hand, or has an increase in symptomsif, at initial presentation, the patient had a histo-

Original contribution • Ames JAOA • Vol 96 • No 4 • April 1996 • 225

ry of constant pain, numbness, or paresthesia inthe hand, and is indicative of a subjective response.1°

The following clinical findings would suggest asubjective response by the patient:q Positive wrist neutral test and negative stan-

dard test for median and ulnar nerve compres-sion.

q Production of the same symptoms by standard testsfor median and ulnar nerve compression com-bined with a positive wrist neutral test.Because the elbows are flexed during the wrist

neutral test, a false-positive test can occur in the pres-ence of ulnar nerve entrapment at the elbow.

The issue of preexisting carpal tunnel syndromedeserves mention. Only two patients in the studyreported here were found to have this conditionpreexisting, and then, preexistence was only foundby the defense during discovery. Neither patientoffered this information. It is reasonable to assumethat this number is actually higher, owing to thesecondary gain involved. However, because almosta third of the total number of patients reportedonset of symptoms after an automobile accident,one must assume that there is a mechanism ofinjury to the carpal tunnel at the time of the acci-dent. It is the author's opinion that the steeringwheel, and, on occasion, the dashboard, is respon-sible for blunt trauma to the carpal tunnel. Theamount of trauma required to produce carpal tun-nel syndrome is unknown. An important area tostudy would be to measure the force across thecarpal tunnel by the steering wheel at impact, andat various speeds, using crash dummies.

CommentThis study suggests that carpal tunnel syndromecan be a sequela to a motor vehicle accident. Byhistory, all patients become symptomatic within 2months after the accident. Because secondary gainmight be an objective in this group of patients, onecannot be certain that carpal tunnel syndrome exists

without objective testing, such as electromyogra-phy. In the retrospective study reported here, 67%of the group of patients who had a motor vehicleaccident had positive results of electromyographicstudies.

Finally, validity of the diagnosis of carpal tun-nel syndrome in the group involved in an automo-bile accident is further supported by the large per-centage (89%) of good or excellent results achievedby surgery. One would not expect these results if thepatients were feigning illness. In the author's opin-ion, the mechanism of injury is blunt trauma to thecarpal tunnel inflicted by the steering wheel, or,less likely, by the dashboard.

Reference1.Haas DC, Nord SG, Bonne MP: Carpal tunnel syndrome fol-lowing automobile collisions. Arch Phys Med Rehabil 1981;62:204-206.2. Grant JCB: Grant's Atlas of Anatomy, ed 5. Baltimore, Md,Williams & Wilkins, 1962, Figures 73-76, 79.3.Netter FH: The Ciba Collection of Medical Illustrations, Vol-ume 8. Musculoskeletal System, Part 1. Summit, NJ, Ciba-GeigyCorporation, 1991, pp 56, 60.4.Tubiana R: The Hand, Volume II. Philadelphia, Pa, WB Saun-ders Co, 1985, p 839.5.McCarty DJ, Koopman WJ: Arthritis and Allied Conditions.Philadelphia, Pa, Lea & Febiger, 1993, p 1524.6. Ruby LK, Stinson J, Belsky MR: The natural history ofscaphoid non-union. J Bone Joint Surg [Am] 1985;67:428-432.7. Folmar RC, Nelson CL, Phalen GS: Ruptures of the flexortendons in hands of non-rheumatoid patients. J Bone Joint Surg[Am] 1972;54:579-584.8. Browne EZ, Snyder CC: Carpal tunnel syndrome caused byhand injuries. Plast Reconstr Surg 1975;56:41-43.9.Guyon MA, Honet JC: Carpal tunnel syndrome or trigger fin-ger associated with neck injury in automobile accidents. Arch PhysMed Rehabil 1977;58:325-327.10.Ames EL: Wrist neutral test, in Kasdan ML, Amadio PC,Bowers WH (eds): Technical Tips for Hand Surgery. Philadelphia,Pa, Hanley & Belfus, 1994, pp 162, 163.11.Lister G: The Hand: Diagnosis and Indications, ed 2. NewYork, NY, 1984, pp 204, 205.

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