in young gymnasts A magnetic resonance imaging study

Disc

degeneration

MINNA TERTTI,*† MB, HANNU PAAJANEN,† MD, URHO M. KUJALA,‡ MD, ANU ALANEN,† MD, TOIVO T. SALMI,§ MD, AND MARTTI KORMANO,† MD

From the

Departments of t Diagnostic Radiology and § Pediatrics, and the &Dag er; Paavo Nurmi Center, Sports Medical Research Unit, University of Turku, Finland quent degeneration of the disc. 1,5, 12 Fractures of the verte-

ABSTRACT

bral end-plates and discogenic back pain are mentioned in the literature on gymnastics injuries,13 but the incidence of degenerative disc disease and its relation to low back pain in gymnasts remain unclear. Disc degeneration can be detected far earlier by MRI than by plain radiographs or discograms.4,15 Disc degeneration involves a gradual loss of water in the nucleus pulposus, a decrease in proteoglycan content, and an increase in the keratan sulphate to chondroitin sulphate ratio.l° MRI directly measures the altered water content of the nucleus pulposus, whereas only the secondary changes are detectable in radiographs.&dquo; Our goal was to analyze, using MRI and radiographic techniques, the incidence and etiology of disc degeneration and its possible relationship to low back pain in a crosssectional study of young competitive gymnasts.

imaging (MRI) was performed on 35 young competitive gymnasts and 10 control subjects in order to detect the number of degenerated discs and other lumbar spinal disorders. Lumbar radiographs were obtained from all gymnasts who showed evidence of disc abnormality on MRI. Eleven gymnasts had suffered from episodes of low back pain during exercises and eight were found to have evidence of back trauma. Only 3 of the 35 gymnasts had MRI evidence of degenMagnetic

resonance

erated discs associated with Scheuermann’s manifestations and spondylolysis. Lumbar radiographs confirmed the diagnosis in these three cases. The results indicate that despite the excessive range of motion and strong axial loading of the lumbar spine that are associated with gymnastic maneuvers, incurable primary damage to the intervertebral discs is uncommon in

young gymnasts dunng growth.

MATERIALS AND METHODS

Subjects injuries appear to be more common in high level competitive gymnastics than in most other athletic activiLow back

study group consisted of 18 male and 17 female gymrepresenting district (N 12), national (N 21) and international (N 2) levels. In addition, 10 control subjects without any regular sport activities and without history of low back pain were examined. The mean age of the gymnasts was 12 ± 2.6 years (range, 8 to 19 years), the mean weight was 39 ± 9.6 kg (range, 23 to 60 kg) and the mean height was 150 ± 13 cm (range, 126 to 170 cm). The gymnasts’ practice time ranged from 3 hours to 24 hours per week, the mean practice time being 12 ± 5.5 hours per week. The number of years of participation in gymnastics varied from 1 year to 10 years; the mean length of participation was 4.2 ± 2.5 years. Correspondingly, the mean age in the control group was 12 ± 2.5 years (range, 8 to 14 years), the mean weight was 46 ± 10 kg (range, 30 to 57 kg), and the mean height was 160 ± 14 cm (range, 139 to 170 cm). The

nasts

ties.3,1’, 21 In addition

to strains and sprains, the repeated microtrauma resulting from hyperextension, hyperflexion, and twisting movements may cause traumatic spondylolysis, vertebral compression fractures, and mechanical back pain.2, 8, 12, 13 For example, a four-times higher incidence of pars interarticularis defects has been reported in young female gymnasts than in controls.2,8 Not only bony structures, but also intervertebral discs are vulnerable in the excessive range of motion associated with gymnastic maneuvers. Powerful compression and flexion stress to the spine may cause traumatic intraosseous herniation and subse-

=

=

* Address correspondence and repnnt requests to Minna Tertti, MB, c/o Martti Kormano, Department of Diagnostic Radiology, University Hospital of Turku, SF-20520 Turku, Finland

206

=

207

Each gymnast answered a questionnaire on years in competition, weekly hours of practice, and history of back pain or trauma. A clinical examination was performed if any back disorders were revealed in the questionnaire. The clinical examination included the evaluation of sensory changes and motor functions of lower extremities and the assessment of spinal mobility. Neither sensory changes nor motor weakness were revealed in any subjects during clinical examination. MRI and

TABLE 1

Subjects who had abnormal MR or radiographic examination

radiographs

MRI of the lumbar spine was performed using a 0.02 Tesla ultralow field resistive system (Acutscan, Instrumentarium Imaging Corp., Finland). The details of the imaging device and the technical parameters of the surface coil have been described earlier.&dquo; The slice thickness was 10 mm and the imaging matrix was 256 x 128. The pixel size was 1.2 X 2.4 mm. Both spin echo (SE) 1000/100 ms (T2-weighted) and gradient echo (SR) 120/30 ms (Tl-weighted) multislice sequences were used to obtain sagittal images of the lumbar

spine. Intervertebral discs with a high signal intensity on T2weighted images were considered healthy and well-hydrated. When the nucleus pulposus desiccates, the signal intensity of the disc diminishes and the disc appears darker on a T2weighted MR image.l5 In this study, all intervertebral discs were considered to be abnormal and degenerated if an over 50% decrease of MR signal intensity was detected when compared to the maximal signal intensity of the lumbar discs. Subsequently, anteroposterior and lateral lumbosacral radiographs were obtained from each subject with abnormal findings on MR images. For ethical reasons, we did not obtain radiographs in the control group.

moderate back trauma (strain or sprain), and four gymnasts ( 11 % ) had a history of both pain and trauma. Two of the three individuals with abnormal discs (Subjects 5 and 7) reported episodes of low back pain during exercises and the third (Subject 6) had a history of two moderate back traumas without episodic pain. In the group of gymnasts with structural abnormality without disc degeneration, two out of four had no history of back trauma or pain at all (Subjects 1 and 4), one had mild trauma (Subject 3), and the last (Subject 2) had a history of episodes of pain and moderate trauma. When viewing types of lumbar abnormalities in relation to history of pain or trauma, it was noticed that all gymnasts with Scheuermann’s disease complained of episodic low back

pain. In the nongymnast control subjects, MRI was normal in nine cases. In one subject (aged 10 years) the L5-S1 disc was abnormal. Because no lumbar radiographs were available, the existence of possible structural abnormalities remained

RESULTS

unknown.

The lumbar discs of 32 of 35 gymnasts were normal on MR images. Three gymnasts had disc degeneration; one of them had two degenerated discs, the others each had one (Table 1). Two of the four degenerated discs were related to Schmorl’s prolapses associated with Scheuermann’s disease (Table 1). In the two remaining abnormal discs, an associated anomaly of the lumbosacral junction was present (Table 1). Four gymnasts had structural abnormalities of the lumbar spine without any signs of disc degeneration (Table 1). It is of concern that all of these gymnasts were quite young (10 to 13 years); however, the gymnasts with structural abnormality associated with degenerated discs were older (15 to 19 years) (Table 1). In addition, the only Scheuermann’s manifestation (in Subject 2) consisted of gross disturbed ossification of the anterior apophysis of T-12 and L1 vertebrae without any Schmorl’s herniations. In this case, the nucleus in the Ll-2 space was displaced posteriorly on the MR image, but the signal intensity remained normal. Eleven gymnasts reported episodes of low back pain during exercises (31%). Eight (22%) had a history of mild or

DISCUSSION This

study indicates that intervertebral discs are surprisingly well preserved in young competitive gymnasts. All of them were intensively practicing gymnastics, trying constantly to improve their performance. Only 4 of 175 discs evaluated

on

MR

scans were

abnormal. Three of the four

degenerated discs were related to structural abnormalities confirmed by radiographs. The only degeneration at a radiographically normal disc space was seen in the oldest gymnast (19 years). This could be assessed as a physiological degeneration, since according to previous results, normal, physiological degeneration appears in 35% of asymptomatic 20year-old volunteers. 16 The present study was cross-sectional. However, the trainers of the teams did not report any drop-outs caused by back pain during preceding years. Thus, a prospective follow-up study would be expected to give the same incidence of degenerative discs. One could expect an increased incidence of abnormal discs

208

in gymnasts. Previous reports clearly indicate that prolonged static load and axial compressive forces can cause end-plate fractures associated with Schmorl’s nodes.’ 5,’, ~2 These prolapses of disc tissue through gaps in the end-plates are probably secondary to the loss of mechanical strength in these defective areas.&dquo; Desiccation of the nucleus pulposus is more likely after such intravertebral prolapses, the net result being disc degeneration. Both cadaveric and clinical studies using discography indicate that Schmorl’s nodes and disc degeneration occur concurrently.6, 11, 20 Our results indicate that the end-plates of the gymnast’s discs are well protected against stress caused by continual alteration of loading and unloading. Such stress may actually promote the metabolism of the intervertebral segment.9 It can also be speculated that a young disc in growing age has a greater ability to adapt to physical stress than an adult disc. In order to evaluate the significance of our results, it should be determined whether the disc degeneration seen by MRI is a pathologic phenomenon or a normal consequence of aging. In fact, disc degeneration is a more or less physiological phenomenon resulting from several factors such as aging, motion, hereditary differences, and various spinal anomalies.22 Autopsy studies indicate that physiologic disc degeneration begins at 20 to 25 years of age.14,19 Further, recent MRI studies confirm that asymptomatic, physiologic disc degeneration begins at the end of the second decade of age and is detected in 6% to 20% of asymptomatic subjects under the age of 20.18 Moreover, it has been previously demonstrated that one or more lumbar discs were degenerated in 57% of 20-year-old patients seen with low back pain and in 35% of the same age symptomless controls. 16 This emphasizes the association of early disc degeneration with low back pain. However, even though 11 gymnasts reported low back pain during exercises and 8 had a history of trauma, only three of them had abnormal MR scans. This indicates that back pain during gymnastic exercises is not suggestive of disc degeneration.

CONCLUSIONS

degeneration was an uncommon finding within young competitive gymnasts. No clear correlation between low back pain or low back trauma and disc degeneration was revealed in this study. During growth, the intervertebral disc seems either to adapt to the physical stress associated with modern gymnastics training or, alternately, the possible Disc

injuries primarily affecting the disc tend to heal spontaneously. However, in the present study, older gymnasts (Table 1) with Scheuermann’s disease (i.e., Schmorl’s prolapses) or spondylolysis also had secondary early disc degeneration. It seems that the intervertebral disc itself adapts to physical stress well, but osseous abnormalities, such as Scheuermann’s disease and spondylolysis, need attention, because they in the course of time lead to disc degeneration. REFERENCES 1

2

3 4

5 6 7

8 9 10 11

12. 13 14

Blumenthal SL, Roach J, Herring JA: Lumbar Scheuermann’s. A clinical series and classification Spine 12. 929-932, 1987 Ciullo JV, Jackson DW Pars interarticularis stress reaction, spondylolysis, and spondylolisthesis in gymnasts Clin Sports Med 4 95-110, 1985 Garnck JG, Requa RK. Epidemiology of women’s gymnastics injuries Am J Sports Med 8 261-264, 1980 Gibson MJ, Buckley J, Mawhinney R, et al: Magnetic resonance imaging and discography in the diagnosis of disc degeneration A comparative study of 50 discs J Bone Joint Surg 68B 369-373, 1986 Greene TL, Hensinger RN, Hunter LY Back pain and vertebral changes simulating Scheuermann’s disease J Pediatr Orthop 5 1-7, 1985 Hilton RC, Ball J, Benn RT. Vertebral end-plate lesions (Schmorl’s nodes) in the dorsolumbar spine Ann Rheum Dis 35. 127-136, 1976 Horne J, Cockshott WP, Shannon HS Spinal column damage from water ski jumping Skel Radiol 16 612-616, 1987 Jackson DW, Wiltse LL, Cirincione RJ Spondylolysis in the female gymnast Clin Orthop 117 . 68-73, 1976 Kraemer J, Kolditz D, Gowin R: Water and electrolyte content of human intervertebral discs under variable load Spine 10 69-71, 1985 Lyons G, Eisenstein SM, Sweet MBE Biochemical changes in intervertebral disc degeneration Biochem Biophys Acta 673 443-453, 1981 Malmivaara A, Videman T, Kuosma E, et al Plain radiographic, discographic, and direct observations of Schmorl’s nodes in the thoracolumbar junctional region of the cadavenc spine Spine 12 453-457, 1987 McCall IW, Park WM, O’Bnen JP, et al Acute traumatic intraosseous disc herniation Spine 10 134-137, 1985 Micheli LJ Back Injuries in gymnastics Clin Sports Med 4 : 85-93, 1985 Miller JAA, Schmatz C, Schultz AB Lumbar disc degeneration: Correlation with age, sex, and spine level in 600 autopsy specimens Spine 13. 173-

178, 1988 15 Modic MT, Masaryk TJ, Ross JS, et al Imaging of degenerative disk disease Radiology 168 : 177-186, 1988 16 Paajanen H, Erkintalo M, Kuusela T, et al Magnetic resonance study of disc degeneration in young low-back pain patients Spine 14 982-985, 1989 17 Pettrone FA, Ricciardelli E Gymnastic injuries The Virginia experience 1982-1983 Am J Sports Med 15 59-62, 1987 18 Powell MC Wilson M Szypryt P: Prevalence of lumbar disc degeneration observed by magnetic resonance in symptomless women. Lancet II 1366-

1367,1986 19 Pritzker KPH Aging and degeneration in the lumbar intervertebral disc Orthop Clin North Am 8 65-77, 1977 20 Quinnell RC, Stockdale HR: The significance of osteophytes on lumbar vertebral bodies in relation to discographic findings. Clin Radiol 33. 197-

204,1982 21

Snook GA Injuries in women’s gymnastics A 5-year study Am J Sports Med7 242-244, 1979 22 Wiltse LL The effect of the common anomalies of the lumbar spine upon disc degeneration and low back pain Orthop Clin North Am 2 569-582, 1971