Th.B. Grivas (Ed.) Research into S p i n a l Deformities 4 IOS Press, 2 0 0 2

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Study of vertebral morphology inScheuermann's kyphosis before and after

treatmentE. Pola, S. Lupparelli*, A .G. Aulisa, G. Mastantuoni, O. Mazza, V. De Santis

C l i n . O r t h o p . P o l . A . G e m e l l i - U n i v e r s i t _ C a t t o l i c a d e l S a c r o C u o r e , R o m a , I T A L Y* C e n t r o O r t h o p e d i c o U m b r o , P e r u g i a , I T A L Y

Abstract Variation of vertebral morphology in Scheuermann's Kyphosis before andafter orthopedic treatment is usually measured by the entity of the curve, using Cobb'smethod, and by vertebral wedging. But the lack of correlation between these parametersand the clinical evolution of the deformity , lead to the possibility of other alterationsthat can explain part of the kyphosis deformities before and after the treatment. In thisgroup of alterations the inclination of anterior and posterior walls, that express thetrapezoid deformity of vertebras, seem to be more reliable indicators of curve responseto ortopedic treatment.

1. Introduction

In 1920 Scheuermann [1] first described the association of developmental Kyphosisand wedging of thoracic vertebrae; he used the term "osteochondritis juvenilis dorsi" [2], butthe condition is universally known today as Sheuermann's kyphosis. Sorenson [3], proposeda diagnosis based on the presence of three or more adjacent vertebrae wedged 5° or more andno evidence of congenital, infectious or traumatic disorders of the spine. These criteria arewidely accepted and used today.

Vertebral geometry alterations in Scheuermann's kyphosis and results of theorthopedic treatment have been measured by radiographic measure of both curve entity andvertebral wedging on longitudinal section [4,5,6,7,8].Clinical evolution of the deformity is not always correlated to presently used radiographicparameters.

On the other hand, it is possible that vertebal morphology alteration in kyphotic curvecould be explained by a more complex theory model than the currently accepted one.In this case currently used radiographic parameters could be insufficient for the evaluation ofentity, progression and response to medical treatment.We have made a revision of our cases in order to define present parameters limits and, at thesame time, to determine new parameters, which could be useful for a better correlationbetween clinical and radiographical findings and a better description of vertebral alterations.

2. Materials and Methods

We made a retrospective study on a specimen of 16 patients with Scheuermann'skyphosis, treated using anti-gravity brace between 1996 and 2000, at Agostino GemelliHospital, department of Orthopaedics, Rome, Italy. 90% of our patients is male, 10% female.

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The mean age at the beginning of the treatment was 13 years. A l l patients had the same bonematurity grade, determined by Bick's method [9,10]. The mean curve entity before treatment, measured by Cobb's method, was 54,5°, a value that, according to literature data, requiresorthopaedic treatment [11]. Radiographical measurement were performed on radiographstaken from a focal distance of 2 meters, on radiographic film 36x91 cm, from a lateralprojection, at the beginning and at the end of the treatment. Vertebral geometry modificationsbefore and after treatment were analysed according to the following parameters, evaluated bythree independent researchers:

- Anterior wedging angle (ALFA)- Anterior wall inclination (AANT)- Posterior wall inclination (APOS)

Anterior wedging angle A L F A has been calculated by two methods (figure la and lb).The first method, used in the measurement of small deformities, is the calculation of

the convex angle obtained by the intersection of two lines, orthogonal to both of the two linespassing through the extremities of superior and inferior vertebral body limits.

The second method, used in the measurement of severe deformities, is the calculationof the convex angle formed by both of the two lines passing through the vertebral plates.The degree of inclination of the anterior wall (AANT) and posterior wall APOS has beenmeasured by the disk limit of every vertebral body (figure 2). Specifically, we measured theangles formed by the line orthogonal to the inferior plate and the line passing trough inferiorand superior limits of the anterior and posterior wall.

Study of the variation of these three parameters (ALFA, AANT, APOS) before andafter orthopaedic treatment was conducted in two phases. During first phase modification ofboth parameters was analysed with the confrontation of pre- and post-treatment vertebralvalues, not considering the vertebra position in the kyphotic curve. During the second phasewe analysed data dividing vertebras in sub-groups, or sectors, in relationship to their positionin the curve. Inclusion of the vertebras in a defined sector followed these criteria: apexvertebra received, conventionally, value 4; upper vertebra received value 3, and lowervertebra value 5. Vertebras positioned at highest and lowest limits of the kyphotic curvereceived, respectively, value 2 and 6. We took L2 as control vertebra, and gave it value 1.

3. Statistics

Measurement variability among observers has been analysed by the Bland-Altmantest. The absence of a significant variability among measurements performed by threeindependent observers enabled us to use, in the statistic elaboration, the mean value of threemeasurements, taking into consideration every parameter.

We used the Shapiro-Wilk test in the evaluation of the gaussian distribution of thepre-treatment ALFA, AANT and APOS values. This evaluation was necessary, as we wereanalysing a specimen not selected from general population through a random process, andbecause it could not satisfy central limit teorema. Test signification (P<0.05), showingnormal distribution of parameters values, allowed us to use, in the statistical interferenceprocedure, the t-test for paired data, i.e. a parametric test, appropriate when the data shownormal distribution. Significative level has been fixed at P<0.05.

4. Results

The results of the analysis are shown in tables 1-6.

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Figure l a and l bMethod for anterior wedging angle A L F A measureTop (figure la) method used for the measure of mild deformity: calculation of convex angleformed by two lines perpendicular to the lines passing through posterior and anterior limit,respectively of superior and inferior disk plates of vertebral body.Bottom (figure lb) method used for the measure of severe deformity, calculation of theconvex angle formed by two lines passing trough vertebral plates.

Figure 2 Measure of anterior wall inclination AANT and posterior wall inclination APOS , conductedusing disk plate limits of every vertebra. More specifically, we have calculate the anglesbetween the line perpendicular to inferior plate and the line passing trough superior andinferior limit of anterior and posterior wall, respectively.

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Table I shows data without making sector division, while tables II-VI show results with thevertebrae divided in sectors.

W h o l e iperkyphotic c u r v e . The pre- and post-treatment variation in ALFA, AANT andAPOS parameters in all the kyphotic curve vertebrae shows a significant reduction in thewedging angle A L F A (P<0.01) and in the posterior wall inclination APOS (P<0.0002). Therewas no significant variation in the anterior wall inclination.

Sector 2 . In this sector, before treatment, mean wedging was 5° Cobb, the posteriorwall ventral inclination was 4° Cobb and the anterior wall dorsal inclination was 2° Cobb.After treatment the wedging decreased from 5° to 3° (P not significant), the anterior wallinclination did not show significant variation, and the posterior wall inclination decreased byabout 50% in value (P<0.02).

Sector 3 . In sector 3 we saw an increase, after treatment, of the wedging angle andthe anterior wall inclination values. The posterior wall inclination decreased. Value variation,however, was not significant.

Sector 4 . At the apex vertebra level, body wedging, which is the highest among thevertebral wedging in all sectors, decreased by 50% in value after treatment (P<0.004). Theanterior and posterior wall inclination decreased, even if the value variation was notsignificative.

Sector 5. Wedging angle showed an increase, even if not significant, of about onegrade, while the anterior wall inclination showed no significant variation. The posterior wallinclination decreased (PO.009).

Sector 6. In sector 6 the wedging angle decrease was not significant and the increasein the anterior wall inclination was not significant, either. The posterior wall inclinationrecorded a significant decrease of about 2° (PO.OOl).

5. Discussion

Conservative treatment of vertebral deformity promotes the application, viaappropriate geometry orthesis, of external forces to obtain, during skeletral growing,remodelling of the deformed vertebras.

In the case of the specific treatment of Scheuermann kyphosis using an antigravitybrace, the biomechanical action ofthe brace applies external forces related to the three pointsprinciple: one force is applied behind the curve apex and the other two forces are applied atthe end of the vertebrae at the curve ends.

Moreover, in according to the vector calculation principles, a force applied to a curvestructure is divided in two components with direction and course determined by theapplication point and by the space orientation of the resultant. Therefore it is logical thatforces applied by an antigravity brace could produce different effects on the vertebralremodelling, depending on vertebra position. Moreover, it's highly probable that vertebralbody deformation caused by an alteration of biomechanical properties of the movementsegment, due to the alteration of ossification nuclei in vertebral bodies, [12,13, 6], consist ofa complex variation of vertebral geometry. Therefore, the deformation of movementsegments, as a consequence of the orthesis treatment action, could not be adequatelyevaluated with present parameters, such as the wedging angle and the curve entity.

The results of our research seem to confirm both theses. Data analysis shows thatspine remodelling in Sheuermann kyphosis is the resultant of two components: vertebralwedging, represented by the anterior wedging angle A L F A , and trapezoid deformation,shown by the anterior wall inclination angle A A N T and the posterior wall inclination angleAPOS. Before the treatment wedging was present in all vertebrae including the curve range,and it was most apparent in the apex vertebra and very high in the adjacent vertebrae, with a

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certain prevalence in the superior vertebra. After the treatment the wedging evolveddifferently in relation with the position of the studied vertebra. The restoration was verygood in apex vertebra, good in sector 2 vertebrae and average in sector 6 vertebrae. It waszero in the vertebra inferior to apex, while deformation was even worse in the superiorvertebra. As for the trapezoid deformity, at the beginning of the treatment this was mostapparent in the vertebra superior to apex, very high in apex vertebra and rather high in thesuperior end of the curve, while it was not so evident in the inferior end. At the end of thetreatment the variation in the inclination of both the anterior and the posterior wall shows,despite the variability of results, constant improvement, more evident in the distal sectorsthan in the apex vertebra.

So our study data shows that, in a state-of-the-art corrective treatment of kyphosis,anterior vertebral wedging angle varied in a different way in the different spine sectors, andin some cases the wedging was even worse after treatment. The analysis of the variation ofanterior and posterior wall inclination shows a constant improvement in the entire curve.Therefore it is probable that there are other alterations that could explain part of the kyphosisphenomena before and after treatment.

We sustain that using new parameters to study vertebral remodelling enables us toreach a better comprehension of Sheuermann spine response to anti-gravity brace treatment.

References

1. Scheuermann HW: Kyphosis dorsalis juvenilis. Ugeskr Laeger 82:385-393,19202. Scheuermann HW: Kyphosis juvenilis (Scheuermann Krankheit). Fortschr Geb Rontgenstr 53:1-16, 19363. Sorenson KH: Scheuermann's Juvenile Kyphosis. Cophenagen, Munksgaard, 19644. Ascani E, Montanaro A. Scheuermann's disease. In: Bradford D, Hensinger R (Eds): "The Pediatric

Spine". Thieme Verlag, New York, 19855. Aufdermaur M. Juvenile kyphosis (Scheuermann's disease): radiography, histology and pathogenesis.

Clin Orthop. 154,166-174,1981.6. Bradford DS, Moe JH. Scheuermann's juvenile kyphosis. A histologic study. Clin Orthop. 110, 45-53,

1975.7. Ferraro C, Fabris D, Ortolani M. Le deformita somatovertebrali nella malattia di Scheuermann. Studio

radiologico e considerazioni biomeccaniche. Progressi in Patologia vertebrale. 5,23-37,1982.8. Fletcher GH. Anterior vertebral wedging. Frequency and significance. Am J Rheum. 57,232-238,1947.9. Bick EM, Copel JW. Longitudinal growth of the human vertebra: a contribution to human osteology. J

Bone Joint Surg. 32-A, 803-814,195010. Bick E M , Copel JW. The ring apophysis of the human vertebra: contribution to human osteogeny. J

Bone Joint Surg 33-A, 783-787, 195111. Aulisa L, Valassina A. La cifosi. In: Autori Vari "Argomenti di Ortopedia e Traumatologia, Verduci

Editore, 1989.12. Ascani E, et al. Studio istologico, istochimico, ultrastrutturale. Progressi in Patologia Vertebrale. 5, 105¬

109, 1982.

13. Ippolito E, Ponseti IV. Juvenile kyphosis. Histological and histochemical studies. J Bone Joint Surg. 63-A, 175-182, 1981.

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Table 1 A v g ± D Spre-treat.

A v g ± D Spost-treat.

t-test P

ALFA 7,71 ±5,79 5,78 ±5,02 -2,44 0,01AANT 2,22 ± 3,23 2,17 ±2,77 -0,13 0,89APOS 4,47 ±4,23 2,74 ±2,42 -3,86 0,0002

Table 1 Results of analysis on variations before and after anti-gravity brace treatment of: the anteriorwedging angle (ALFA), the anterior wall inclination angle (AANT), the posterior wallinclination angle (APOS). It is evident that there gas an important reduction of wedging angleA L F A (P 0.01) and ofthe posterior wall inclination angle APOS (P<0.0002). Variation of theanterior wall inclination is not important. Confrontation with tables II-VI shows that statisticanalysis on undifferentiated data is not able to study the effects of brace treatment on everysingle vertebra.

Table 2 A v g ± D S A v g ± D S t-test Ppre-treat. post-treat.

ALFA 5,28 ±4,87 3,21 ±5,66 -1,34 0,17AANT 1,91 ±2,14 1,24 ±1,41 -1,10 0,27APOS 4,06 ± 3,78 2,16±2,19 -2,36 0,02

Table 2 Results of analysis in sector 2 on variations of: the anterior wedging angle (ALFA), theanterior wall inclination angle (AANT) and the posterior wall inclination angle (APOS). Inthis sector, before treatment, the mean wedging angle is 5 ° Cobb, the posterior wall ventralinclination angle is 4° Cobb and the anterior wall dorsal inclination angle is about 2 °. Aftertreatment the wedging angle decreases from 5 ° to 3 ° (P not significative), the anterior wallinclination does not record important variation, while the posterior wall inclination anglerecords a 50% decrease (P<0.02)

Table 3 Avg ± DSpre-treat.

A v g ± D Spost-treat.

t-test P

ALFA 7,88 ±5,13 9,59 ±5,12 1,23 0,28AANT 2,31 ±3,13 3,01 ± 3,56 0,31 0,69APOS 7,24 ±5,24 6,12 ±4,32 -0,67 0,51

Table 3 Results of analysis in sector 3 on variations of: anterior wedging angle (ALFA), anterior wallinclination angle (AANT) and posterior wall inclination angle (APOS). In this sector ,aftertreatment, wedging angle and anterior wall inclination angle increases. Posterior wallinclination angle decreases. Observed values variation isn't significative.

E. P o l a et al. /Study of V e r t e b r a l Morphology in Scheuermann's Kyphosis 411

Table 4 A v g ± D Spre-treat.

A v g ± D Spost-treat.

t-test P

ALFA 15,32 ±6,12 7,17 ±4,88 -3,50 0,004AANT 3,84 ±2,75 2,52 ± 3,29 -1,52 0,11APOS 6,34 ±3,71 4,23 ±3,12 -0,15 0,29

Table 4 Results of analysis in sector 4 on variations of: anterior wedging angle (ALFA), anterior wallinclination angle (AANT9 and posterior wall inclination angle (APOS). In apex vertebrawedging is higher than in all other vertebras in different sectors. Wedging angle decrease of50% after treatment (P<0.004). Anterior wall inclination angle as well as posterior wallinclination angle decreases, even if the variation isn't important.

Table 5 A v g ± D Spre-treat.

A v g ± D Spost-treat.

t-test P

ALFA 6,71 ±4,11 7,35 ±3,12 0,29 0,77AANT 2,21 ±2,22 2,34 ±1,12 0,07 0,93APOS 3,54 ±3,10 2,11 ±1,10 -3,09 0,009

Table 5 Results of analysis in sector 5 on variations of: anterior wedging angle (ALFA), anterior wallinclination angle (AANT) and posterior wall inclination angle (APOS). In this sectorwedging angle increases, not significatively, of about 1°, while anterior wall inclinationdoesn't have important variations. Posterior wall inclination angle decreases significatively(P<0.009)

Table 6

A v g ± D S A v g ± D S t-test Ppre-treat. post-treat.

ALFA 6,07 ±4,25 4,67 ± 3,54 -1,23 0,23AANT 1,20 ±0,09 2,20 ±1,64 0,95 0,36APOS 3,22 ± 2,49 1,01 ±0,55 -3,78 0,001

Table 6 Results of analysis in sector 6 on variations of: anterior wedging angle (ALFA), anterior wallinclination angle (AANT) and posterior wall inclination angle (APOS). In sector 6 wedgingangle decreases not significatively and anterior wall inclination angle increases, as well notsignificatively. Posterior wall inclination angle decreases significatively of about 2JE (P<0.001)