Journal of Cap ital M edical University

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Mark Garrison
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1 Journal of Cap ital M edical University Dec Vol. 29 No. 6 ( ),, 16 1 ( ) kg, 8 T 8 T 9 25 mm, 5 mm 4, 12 Cobb ( T 9 ), t, , : ( ) kg, : ( ) kg, P = , 2 1 T 9 ( ) mm, 12 ( ) mm, 1 T 8 2T 10 Cobb , , ( P < ), ,, , ( P = ) T 8 2T 10,, N Hueter2Volkmann, ; ; ; ; R Effect of M im ic Poster ior A symm etr ic Tether by M agnetic Force on Sp ina l Growth of Imma ture M in i2p ig( Establishm en t of an Exper im en ta l ScoliosisM odel) Ma Xiongjun, W ei J ianjun, W ang Dong, Sun Tong (D epartm ent of O rthopedic, B eijing A nzhen Hospital, Capital M edical U niversity) T 10 ABSTRACT O bjective To exp lore the etiology and pathogenesis of idiopathic scoliosis by creating experimental scoliosis aswell as validate the hypothesis of sp inal growth imbalance. To determ ine the magnitude ranges of sp inal tether force and observe the changes of m ini2p ig s sp inal deform ity in three2dimensional sections by posterior transpedicle screws with Nd2Fe2B magnetic materials. M ethods Sixteen m ini2p igs( female, 4 weeks old, ( ) kg were random ly arranged averagely into tethering group and control group. Left2 side posterior transpedicle screws(25 mm) with magnets were p laced into vertebrae from T 8 to T 10 in tethering group s and maintained the p roper magnetic polarity within distance of 5 mm; in the control group p igs underwent operation only using pedicle screws; they were all checked by A2P and lateral X2ray film s every 4 weeks until 12 weeks to measure item s responded to degrees of sp inal deform ity including weights and Cobb angles in coronal section and sagittal kyphosis and the heights of apex vertebral ( T 9 ) between two sides as well as magnitudes of magnetic forces among the involved vertebrae. Results Mean weights of m ini2p ig increased about 2 times in 12 weeks ( ) kg in tethering group and (21. 75kg 1. 67) kg in control group, P > 0. 05). The heights of T 9 vertebral increased double during 12 weeks from 6. 5 mm 0. 6 mm to mm mm in control group. The radiographic analysis demonstrated scoliosis of in T 8 2T 10 tethered segments, as compared with in the control group ( P < ). Sim ilarly, thoracic lordosis developed in the tethered segments , as compared to at the control levels ( P = ). Conclusion The asymmetrical tethering performed by transpedicle screws with Nd2Fe2B magnets upon the vertebral body T 8 2T 10 of m ini2 p igs can modulate their sp inal growth and create the m ild scoliosis in coronal section and lordosis in sagittal section. of magnetic force upon sp inal growth p lates is from 1. 0 N to 2. 3 N. scoliosis pathology and abide by the Hueter2Volkmann law. the magnitude range Thismethod validate the hypothesis of sp inal growth imbalance related The asymmetrical posterior tethering of sp ine have an important role in scoliotic onset and p rogressing, lordosis in the sagittal section may be the p rimary deform ity of scoliosis.

2 6 : 691 KEY WO RD S experimental scoliosis; sp inal posterior tether; growth modulation; etiology; pathogenesis,,, ( ),, ( ) kg 1. 2,, 0. 5 cm,,, (10 mg/kg), X 1 1 N e e d ling po in t o f tho ra c ic ve rte b ra e ( T 8, T 9 a nd T 10 ), N233, 8 mm 2) :, 10 mm 10 mm, ( ) Gs, Gs ( ) mm 10 mm 2. 5 mm 1),, ( ) 2. 5 mm ( ) mm, 2) 4 X, 1. 3 : : 16, 8 ; :,, T 8 2T 10 Cobb ( : ( T 9 ) ; 13362) ) : 3% (1 ml /kg) SPSS 12. 0,, 15 m in, ( gx s), t, P < 0. 05, 5 cm, 1 Ansoft (5 g/l ) Cobb,, T 8 T 9 T 10 2, 1 1 / mm, 1,, 15, 10,,, 2, 1 /3,, 1,, T 8 T 9 T 10,,, F ig.

3 692 29,, , : ( ) kg, : ( ) kg, P = , 2, 1 T 9 ( ) mm, 12 ( ) mm, X, T 8 2T 10 Cobb , , ( P < ), ,, , ( P = ) T 9 ( ) ( ) mm ( ) mm, ( P = ) T 9 ( P = ), ( P = ) T , , 2 ( t = 1. 34, P = ),,, 4. 25, 1 Ta b. 1 Ana lysis o f c lin ica l da ta be tw e en two g ro up s ( gx s) Scoliosis/ Item Control Tethering t P Kyphosis/ H ight of T 9 /mm Height of T 9 /mm < HC / C F ig. 2 The AP a nd la te ra l view s befo re su rge ry dem o n stra te d C kyp ho sis o f tho rac ic2lum be r segm e n ts o n m in i2p ig N233, MGOe, 1 ( ) mm, ( ) mm,,,, Ansoft,, 4mm 7mm,

4 6 : 693 F ig The AP a nd la te ra l view s a fte r su rge ry (12 w e eks la te r) dem o n stra ted no cu rve in co ro na l p lane a nd lo rdo sis in sa gg ita l p la ne in co n tro l g ro up Gs Gs ( 5 6),, N, MPa 6,,,, SirW illiam Adam s, Somerville [ 1 ] Roaf [ 2 ],,,,,, Stoke [ 3 ],, Stoke Hueter2Volkmann,,,,,,, Porter [ 4 ],, Porter [ 5 ] 15,,, Cobb,, T 8 2T 10,,,,, T 8 2T 10 ( ), 12,

5 F ig. 4 The AP view in the in stan t o f po st2op e ra tio n and 12 w ee ks la te r o f po st2op e ra tio n A: The AP view in the instant of post2operation demonstrated no spinal curve occurred in coronal plane; B: The lateral view in the instant of post2operation demonstrated 5 sp inal lordosis occurred in sagittal p lane; C: The AP view (12 weeks later) demonstrated development of sp inal scoliosis convex to the right side, Cobb angle 15 ; D: The lateral view (12 weeks later) demonstrated development of sp inal lordosis in sagittal p lane (5. 5 )., T 9, T 9,,,, Hueter2Volkmann,, 12,,,,,

6 6 : 695, : 1), T, T, 2) 3,, : 1), ; 2), ; 3) 4) 4, Ansoft 1. 0 N 2. 3 N, Cobb ,, 15 mm 2, MPa, [ 6 ] MPa, [ 1 ] Somerville E W. Rotational lordosis: The development of the single curve[ J ]. J Bone Joint Surg, 1952, 34: [ 2 ] Roaf R. The basic anatomy of scoliosis [ J ]. J Bone Joint Surg B r, 1966, 48: [ 3 ] Stokes I A, Spence H, A ronsson D D, et al. Mechanical modulation of vertebral body growth: imp lications for scolio2 sis p rogression[ J ]. Sp ine, 1996, 21: [ 4 ] Porter R W. Idiopathic scoliosis: the relation between the vertebral canal and the vertebral bodies[ J ]. Sp ine, 2000, 25: [ 5 ] Porter R W. Can a short sp inal cord causes idiopathic scoli2 osis[ J ]. Eur Sp ine J, 2001, 10: 229. [ 6 ] Stokes IA, Gardner2Morse M. Muscle activation strategies and symmetry of sp inal loading in the lumbar sp ine with scoliosis[ J ]. Sp ine, 2004, 29: ( : )

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