the spine in sport and veteran military parachutistsofthe ex-military parachutists x-rayed, 84 7%had...

Annals of the Rheumatic Diseases, 1977, 36, 332-342

The spine in sport and veteran military parachutistsC. F. MURRAY-LESLIE, D. J. LINTOTT, AND V. WRIGHT

From the Rheumatism Research Unit, University ofLeeds, and Department of Diagnostic Radiology, GeneralInfirmary at Leeds

SUMmARY Spinal injuries and symptoms were studied in 109 ex-military parachutists and 112 sport(free fall) parachutists by means of postal questionnaires. 46 ex-military parachutists aged 50 yearsor over had a radiological examination of the lumbar spine and 58 sport parachutists had a radio-logical examination of the cervical spine as part ofthe survey. A history of back pain was significantly(P<0O01) associated with body weight in sport parachutists but not with the number of descents orwith the subject's age. In the older ex-military group neither age, weight, nor the number of descentswas significantly associated with backache.Of those ex-military parachutists x-rayed, 10 (21 * 7 %) were found to have vertebral body fractures

(most frequently at D12), and 8 of these were unaware of these lesions. Vertebral fractures causedno disability and did not permanently curtail parachuting activities in either the sport or ex-militarygroup.Of the ex-military parachutists x-rayed, 84 7 % had lumbar disc degeneration of all grades of

severity, 17 4% had moderate changes, and 10 8 % had severe changes. The frequency of moderateand severe disc degeneration was significantly related to age but not to body weight or to thenumber of descents. Spondylolysis was found in 2 subjects (4 *3 %) and spondylolisthesis unassoci-ated with spondylolysis in 4 (8 7 %). Spondylolisthesis was always associated with a history ofback pain.A low prevalence of radiological cervical intervertebral disc degeneration of all grades of severity

of 8 7 % was found among the free fall parachutists (mean age 33 years). 2 cases of cervical vertebralbody fracture were seen, one related to a parachute landing injury and the other to a parachuteopening injury.

This study does not implicate parachuting as a cause of intervertebral disc degeneration, eithercervical or lumbar, nor as a cause of spondylolysis or spondylolisthesis. Serious long-term disabilityfrom pain appears to be uncommon among parachutists despite the frequency of the spinal traumathey sustain.

Parachuting is well known to cause injury to thespinal column, most commonly vertebral bodyfractures unassociated with spinal cord or nerve rootdamage (Essex-Lopresti, 1946; Ciccone and Rich-man, 1948; Neel, 1951; Kirby, 1974). The distribu-tion of these is characteristic with maximal frequencyoccurring at or around the first lumbar vertebra, andwith 30% of cases having more than the vertebrainvolved (Neel, 1951; Kirby, 1974). The fracturesare typically ofthe wedge compression type describedby Holdsworth (1970), and are usually caused by

Accepted for publication November 26, 1976Correspondence to Dr. C. F. Murray-Leslie, Dept. ofRheumatology and Rehabilitation, Derbyshire RoyalInfirmary, London Road, Derby DEl 2QY.

landing heavily on thj buttocks, in the course ofbeing blown backwards (Ciccone and Richman,1948; Neel, 1951; Kirby, 1974). The descent rate andhence the vertical component of the eventual landingforce under a military parachute will dependprincipally upon the weight of the man, and for afully equipped soldier weighing 113 kg will be in theregion of 5-4 m/s (B. Tansley, personal communica-tion, 1974). Sophisticated modem sport parachutesgenerally have lower descent rates than conventionalhemispherical canopies, but if mishandled canproduce very high descent rates (E. Edmonds,personal communication, 1975). The peak decelera-tion g forces on the spine in a head-toe directionduring a parachute landing have been shown to

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The spine in sport and veteran military parachutists 333

range between 3 2 and 17-0 with a mean of 5 8 forseveral different types of parachute (Reid et al.,1971).During the opening of a parachute the spine is

subjected to deceleration forces; in the case of amilitary aircraft slipstream deployment the peakopening forces are around 4 0 g (Neel, 1951). Thisis well within the human spinal tolerance limit of20 g (Ruff, 1945; Laurell and Nachemson, 1963).In free-fall parachute openings where the fallingvelocity of the parachutist is frequently of the orderof 55-4 to 61 5 m/s, peak opening shock forces arehigher than in military openings and inhibitingdevices have to be fitted to slow the opening sequenceof the parachute (Reid et al., 1971; E. Edmonds,personal communication, 1975). Peak head-to-toe gforces of between 3 - 0 and 15 m/s with a mean of 7 * 8have been reported during a series of terminalvelocity openings on different free-fall parachuteswith inhibiting devices fitted (Reid et al., 1971).No systematic study of the long-term effects of

parachuting on the spine has been made. This studyinvestigates the prevalence of lumbar intervertebraldisc degeneration, vertebral body fracture, spondy-lolysis (Wiltse, 1962; Newman, 1963; Turner andBianco, 1971; Wiltse et al., 1975), and spondylolis-thesis (Newman, 1963; Wiltse, 1962; Rosenberg,1975) in veteran military parachutists and the effectsof parachute opening forces on the cervical spine insport parachutists.

Subjects and methods

Medical and parachuting information was obtainedfrom 112 experienced and active (free fall) para-chutists and 109 ex-military parachutists by postalquestionnaire as described previously (Murray-Leslieet al., 1977).

In addition to the radiography described previously(Murray-Leslie et al., 1977) the ex-military para-chutists who were aged 50 or more and who wereagreeable, had lateral and left and right oblique

Fig. 1 Appearance ofa pars interarticularissimulatingspondylolysis.

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334 Murray-Leslie, Lintott, Wright

radiographs of the lumbar spine. Volunteers fromamong the free-fall parachutists had a lateralradiograph of the cervical spine.

RADIOLOGICAL ASSESSMENTSThe lateral lumbar spine radiographs were assessedfor intervertebral disc degeneration by one of us(D.J.L.), in randomized sequence and in ignoranceof the subjects' identities, medical or parachutinghistory. In obtaining an overall grade for each discspace, narrowing and osteophytosis were assessedseparately using a 5 point grading scale (0=normal,1-doubtful, 2=mild, 3=moderate, 4=severe) andthe highest grade for either feature was taken.Spondylolisthesis was recorded, and the level,degree, and direction of slip noted. Vertebral bodyfractures were recorded. The partes interarticularesseen in the right and left oblique radiographs of thelumbar spine were examined for spondylolysis andthis feature recorded as present or absent at eachlevel. Only clear and complete breaks in the bonycontinuity of the partes were taken as constitutingspondylolysis. Sclerosis and apparent or incompleteareas of radiolucency such as shown in Fig. 1 werenot regarded as adequate evidence of spondylolysis.

Marked degenerative changes in the apophysealjoints were also recorded if present and any associa-tion with spondylolisthesis noted.The cervical spine radiographs taken in the free-

fall parachutists were also examined in randomizedsequence and assessed for intervertebral discdegeneration by comparing them with the fivegrades of severity illustrated in the Standard Atlasof Radiographs of Arthritis (Jeffrey et al., 1963).Any vertebral body fractures present wererecorded.

Results

COMPOSITION OF GROUPS STUDIEDThe ages and details of the parachuting experience ofeach of the two groups of parachutists studied isgiven in the preceding article describing the effectsof parachuting on the knees and ankles (Murray-Leslie et al., 1977). The principal differences werethat the free-fall parachutists were all parachuting atthe time of the study, were younger, and as a rulehad carried out a greater number of descents overa shorter period than had their ex-military counter-parts.

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Fig. 2 Prevalence ofdegeneration of each grade ofseverity at each lumbarintervertebral disc level.

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SPINAL INJURIESThe number of subjects reporting either vertebralfractures or soft tissue back injuries, when engagedin parachuting or nonparachuting activities, is givenin Table 1.

BACK SYMPTOMS IN SPORT PARACHUTISTSOf the sport parachutists (mean age 33 years), 50(44 5%Y.) reported having suffered from backache,either in the past or currently, and 22 (19 6%) hadlost time at work through backache. 11 parachutists(9 8%) complained of persistent or recurrent back-ache and 2 had had laminectomies. A history ofbackache was significantly associated with anincreased body weight (t=2'85, P<001) but notwith age or the number of descents carried out. Inthis highly experienced group all actively engaged inparachuting at the time of the survey, 16% specifiedbackache as a consequence of an intensive spell ofparachuting, as compared with generalized stiffnessand aching in 82% and knee pain in 4%. Minor

Table 1 Spinal ('back') injuries, both fractures andnonfractures reported in questionnaires by 112 sport and109 ex-military parachutists

Sport parachutists Ex-military parachutists(112) (109)no. with back injuries no. with back injuries

Parachuting Non- Parachuting Non-parachuting parachuting

Vertebralfracture 17 (15>) 0 13 (11-9%) 2 (1-8%)

Soft tissueback injuries 19 (16-9%) 12 (10-7%) 2 (1-8%) 2 (1.8%)

symptoms from parachute opening shocks werefrequent, with 59 parachutists (53%) rememberingat least one unpleasant opening often due to a headdown position during parachute deployment andcanopy inflation or the use of a parachute without adevice to retard the opening sequence. Of those whohad symptoms after a parachute deployment, 16(14 3%) had experienced back pain at least once,

Fig. 3 Vertebralbody fracture at L2in an ex-militaryparachutist.


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33 (29 * 5 %) neck and shoulder pain, and 20 (17 * 8 %)had become transiently dizzy on at least oneoccasion. 2 subjects reported major incidents afterhard parachute openings: one had had a fracture ofthe 6th cervical vertebra, another had becomeunconscious for 30 minutes and had developed

weakness and mild neurological signs in the legsafter an opening.

BACK SYMPTOMS IN EX-MILITARY PARACHUTISTSOf this group (mean age 47-8 years), none stillparachuting at the time of the survey, 61 (56 Y.) gavea history of past or present backache and 26 (23 * 8 %)had lost time from work with backache. 15 para-chutists (13 .4%) complained of persistent orrecurrent backache and one had had a laminectomy.A history of backache was not significantly correlatedwith either weight, age, or the number of parachutejumps, but was more frequent (76- 9 %) in those withsevere and moderate disc degeneration in the lumbarspine than in those with normal, doubtful, or mildchanges (39 4%). The majority of the group con-sidered that parachuting had caused them no harm,but of the 18 (16 5%) who felt at the time of thesurvey that they had symptoms attributable toparachuting, 6 (5 5%.) specified backache and 2neck pain.Of the 6 parachutists who had stopped parachuting

as a direct consequence of symptoms or injuries, 2(1 8 %) had sustained back injuries. Of the remainder,one had leg shortening resulting from a fracturedfemur, 2 had severe persistent knee symptoms, andone had a severe ankle fracture.

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Fig. 4 Vertebral body fractures at T12 and LI in a32-year-old sport parachutist sustained on this 8thdescent. He has subsequently carried out 1000 descentsand has no back pain.

Fig. 5 Distribution of vertebral body fracture, grades of

disc degeneration, spondylolysis, and spondylolisthesisbetween those parachutists with and without a history ofback pain.

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RADIOLOGYForty-six ex-military parachutists over 50 years ofage (mean age 45 years) underwent radiology of thelumbar spine (a completion rate of 73%0) and 58sport parachutists (mean age 33 years) had radiologyof the cervical spine (a completion rate of 69-8 %).

Lumbar ,,pine in ex-military parachutistsThe overall grading of the intervertebral discdegeneration usually depended on the severity of theosteophytosis seen, and of the 222 disc spacesvisualized and graded in the lumbar spine in onlyfour instances was disc space narrowing given ahigher grade than osteophytosis and this narrowingwas mild (grade 2) in three and moderate (grade 3)in one instance (Fig. 10). The grading ofosteophytosisin this study closely resembled the osteophytosis ofthe composite grades (0-4) shown in the StandardAtlas ofRadiographs ofArthritis (Jeffrey et al., 1963).The prevalence of intervertebral disc degeneration

at each vertebral level for each grade of severity is

shown in Fig. 2, and the frequency of multiple discdegeneration occurring in the same spine in Table 2.39 (84 8 %) of the spines examined had some degreeof disc degeneration (grades 2-4), with 26 (56 5 %)having no more than mild (grade 2) changes present,8 (17 * 4 %) no more than moderate (grade 3) changes,and 5 (10 9 %) severe (grade 4) changes. Parachutistsshowing at least one disc with moderate (grade 3) or

Table 2 Prevalence of multiple intervertebral discdegeneration in the lumbar spines of 46 ex-militarypararhutists (mean age 55 years)

No. of discs No. of subjectsinvolved

Grade 2-4 Grade 3-4

1 39 (84-8%) 13 (28-3%)2 28 (60-8%) 7 (15-2%)3 16 (34-8%) 2 (4-4%)4 6(13.0%) 1 (2-2%)5 1 (2-2%) 0

See Table 4 for explanation of grades.

Fig. 6 Bilateralspondylolysis occurringat L3 seen on a lateralradiograph in a50-year-old ex-militaryparachutist with 100descents.


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severe (grade 4) changes in their lumbar spines weresignificantly older than those with normal (grade 0),doubtful (grade 1), or mild changes (grade 2)(t=3-24, 0 01>P>0 005). No significant relation-ship to body weight or the number of parachutedescents made between these groups was found.Subjects with two or more moderate or severelydegenerated lumbar discs were also significantlyolder (t=3-46, 0-02>P>0-01), but not heavier ormore experienced in terms of descents comparedwith those with only one moderate or severelydegenerated lumbar disc.

Fourteen vertebral body fractures were seen in 10subjects (21 7%) (Figs. 3, 4) and their frequency ateach level is given in Table 3. 8 subjects had beenunaware of the vertebral body fractures and 6 wereunable to remember any specific injury which mighthave accounted for these. The distribution of thefractures in subjects with and without backache isshown in Fig. 5. Four instances of spondylolisthesiswith less than a 25% diameter slip were seen in 4subjects (8'7 %) and their distribution in the lumbarspine is shown in Table 3. In one the spondylolis-thesis at L4/5 was associated with marked osteo-arthrosis of the apophyseal joints, and in anotherthe slip at L3/L4 was reversed. All the subjects withspondylolisthesis gave a history of backache (Fig. 5).

Table 3 Frequency and site of vertebral body fractures,spondylolisthesis, and spondylolysis in 46 ex-militaryparachutists

Type of lesion Vertebral body Spondylolysis Spondylolisthesisfracture

No. of lesions 14 3 4 (grade 1)No. of subjects 10 2 4Distributions Dt1 2 L3 (bilaterally L2/3 1

D12 5 same subject L3/4 2LI 5 L5 1 L4/5 1L2 1L3 0L4 1L5 0

Spondylolysis of the partes interarticulares wasfound in 2 subjects (6' 5%), occurring at L5 on theright in one subject, unassociated with back pain orspondylolisthesis, and occurring bilaterally at L3 inthe other subject where it was associated with backpain but not with spondylolisthesis (Figs. 6 and 7).

Cervical spine in sport parachutistsThe prevalence of cervical intervertebral discdegeneration is shown in Table 4. Two instances offracture of the bodies of cervical vertebrae wereseen. One at C6 (Fig. 8) was related to a parachuteopening shock taken in a head down position, the

Fig. 7 One of the lesions seen inFig. 6 on a left oblique radiograph.


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Table 4 Frequency of cervical intervertebral discdegeneration in 58 sport parachutists (mean age 33 years)

Grade of severity (0%)

Level 0+1 2 3 4normal and mild moderate severedoubtful

C2/3 100 - - -C3/4 100 - - -C4/5 100 - - -C5/6 92.9 7-1 - -C6/7 93 5*3 1.7 -

other a fracture dislocation at C4 (Fig. 9) resultedfrom a flexion injury of the neck on landing inhigh winds.

Discussion

The prevalence of vertebral body fractures reportedby sport and ex-forces parachutists of 15 and 11 9%respectively is similar, despite more descents havingbeen made by the former group (mean 788, range200-2966) compared with the latter (mean 236,range 7-1600). However, the finding that 80% of theex-military parachutists were apparently unaware ofvertebral fractures discovered by radiology duringthis survey suggests that either some of thesefractures were not initially painful or, more likely,that they either were not x-rayed initially or have ashort memory for such injuries. In keeping with thelast suggestion is the low reported frequency of backinjury in both groups (16-9% for sport and 1.8%for ex-military), and the staunch conviction of bothgroups that parachuting did not or had not causedthem any harm apart from limb fractures. Backinjuries had in fact only caused 2 men (1 8 %), bothin the ex-military group, to give up parachuting.

Present or previous back pain of all grades ofseverity was reported with similar frequency by bothgroups of parachutists, but it is possible thatalthough the free-fall parachutists were younger theopportunities for backache may have been greaterowing to their much greater parachuting activity-often 4 to 8 jumps in a day.Although the method of grading lumbar disc

degeneration is a little different from the methodused by Lawrence (1969), the overall prevalence oflumbar disc degeneration (grades 2-4) and theprevalence of the severer grades (3 & 4) seems to behigher in the ex-military parachutists studied thanin a sample of men of comparable age from thegeneral population (Table 5).The prevalence of spondylolysis of the lumbar

partes interarticulares in this series, three lesions in2 subjects (4- 3 %.) and unassociated with spondylolis-thesis, is less than has been reported for the general

population (Roche and Rowe, 1952; Baker andMcHollick, 1956; King, 1966). However, on thefilms available it was not possible to make a decisionabout the presence or absence of spondylolysis atevery level in every subject and films were not

Fig. 8 Fracture of body of C6 in a 37-year-old sportparachutist caused by a parachute opening shock.


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repeated for technical reasons owing to the studyinvolving volunteers. In all, 20% of the 460 lumbarpartes were not sufficiently well-defined for a decisionto be made.Although cervical vertebral body fractures and

Table 5 Comparison of the frequency of lumbarintervertebral disc degeneration in 46 ex-militaryparachutists with men of similar age from a populationsurvey

Population survey (%) Ex-military parachutists (%)(Lawrence, 1969)154 men (54 to 64 years) 46 men (50 to 70 years, mean

55-2 years)

Grade 2 59*8 56.5Grade 3 16-2 17-4Grade 4 3-9 10-9Grades 2-4 77.9 84-8

neurological damage can rarely occur on parachutedeployment, premature degenerative disc diseasedoes not appear to be a feature of free-fall para-chuting.

This study has shown a moderately increasedprevalence of moderate and severe lumbar inter-vertebral disc degeneration in the 46 ex-militaryparachutists studied radiologically, which does notseem to be directly related to the number of descentscarried out, or the subject's weight, but related moreto the subject's age. Severe back pain and long-termdisability were uncommon. They usually did notaccompany the more marked lumbar disc degenera-tion (Fig. 11) and were never associated withprevious vertebral body fractures (Fig. 4).

We particularly thank the parachutists who tookpart, but also the radiologists and radiographers,both military and civilian, who organized theradiology; the British Parachute Association; Irvinsof Great Britain Ltd.; Wing Commander G.Turnbull; Squadron Leader D. Reader of R.A.E.Farnborough, R.A.F. Boscombe Down; and ColonelM. Hector, Dr. J. T. Patton, Dr. J. C. MacLarnon,Major J. Loveday, Major W. H. Leach, Lt. Col.I. M. Carmichael, Mr. A. C. Quinlan, Mr. H. B.Bentley, Miss E. Robbins, Mrs. R. Hopkins, andMrs. J. Battersby for their generous help.

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Fig. 9 Fracture/dislocation at C4/5 in a 36-year-oldsport parachutist as a result ofa backward landing.

._ c v E E 2,z 0 ~~~z 0

Fig. 10 Comparison of the separate grading of vertebralosteophytes and intervertebral disc space narrowing inthe same series of lumbar spine radiographs of46ex-military parachutists.


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Fig. 11 Severe degenerativechanges in the lumbar space ofa60-year-old ex-RAFparachuteinstructor who made 1200 descentsover 18 vears with a body weightof 90 kg, and who does notcurrently suffer from back pain.

References

Baker, D., and McHollick, W. (1956). Spondyloschisis andspondylolisthesis in children. Journal of Bone and JointSurgery, 38A, 933-934.

Ciccone, R., and Richman, R. M. (1948). Mechanism ofinjury and distribution of 3000 fractures and dislocationscaused by parachute jumping. Journal of Bone and JointSurgery, 30A, 77-97.

Essex-Lopresti, P. (1946). The hazards of parachuting.British Journal of Surgery, 34, 1-13.

Holdsworth, F. (1970). Fractures, dislocations and fracture-dislocations of the spine. Journal ofBone andJoint Surgery,52A. 1534-1551.

Jeffrey, M. R., Kellgren, J. H., and Ball, J. R. (1963). TheEpidemiology of Chronic Rheumatism. Vol. II. Atlas ofStandard Radiographs of Arthritis. Blackwell, Oxford.

King, A. B. (1966). Experiences with spondylolisthesis. JohnsHopkins Medical Journal, 118, 2-9.

Kirby, N. G. (1974). Parachuting injuries. Proceedings of theRoyal Society of Medicine, 67, 17-21.

Laurell, L., and Nachemson, A. (1963). Some factorsinfluencing spinal injuries in seat ejected pilots. AerospaceMedicine, 34, 726-729.

Lawrence, J. S. (1969). Disc degeneration: its frequency andrelationship to symptoms. Annals of the RheumaticDiseases, 28, 121-138.


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Murray-Leslie, C. F., Lintott, D., and Wright, V. (1977). Theknees and ankles in sport and veteran military parachutists.Annals of the Rheumatic Diseases, 36, 327-331.

Neel, S. H. (1951). Medical aspects of military parachuting.Military Surgeon, 108, 91-105.

Newman, P. H. (1963). The aetiology of spondylolisthesis.Journal of Bone and Joint Surgery, 45B, 39-59.

Reid, D. H., Doerr, J. E., Doshier, H. D., and Ellerston,D. G. (1971). Acccleration and opening shock forces duringfree fall parachuting via FM/FM telemetry. AerospaceMedicine, 42, 1207-1212.

Roche, M. B., and Rowe, G. G. (1952). The incidence ofseparate neural arch and coincident bone variations.Journal of Bone and Joint Surgery, 34A, 491-494.

Rosenberg, N. J. (1975). Degenerative spondylolisthesis.Journal of Bone and Joint Surgery, 57A, 467-474.

Ruff, S. (1945). Brief acceleration in less than one second.German Aviation Medicine, World War 2, p. 584, UnitedStates Government Printing Office, Washington, D.C.

Turner, R. H., and Bianco, A. J. (1971). Spondylolysis andspondylolisthesis in children and teenagers. Journal ofBone and Joint Surgery, 53A, 1298-1306.

Wiltse, L. L. (1962). The aetiology of spondylolisthesis.Journal of Bone and Joint Surgery, 44A, 539-560.

Wiltse, L. L., Widell, E. H., and Jackson, D. W. (1975).Fatigue fracture: the basic lesion in isthmic spondylolis-thesis. Journal of Bone and Joint Surgery, 57A, 17-22.


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