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SpineDeformity_JSPD_324

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SpineDeformity_JSPD_324

  1. 1. Dear author, Please note that changes made in the online proofing system will be added to the article before publication but are not reflected in this PDF. We also ask that this file not be used for submitting corrections.
  2. 2. Probing and Tapping: Are We Inserting Pedicle Screws Correctly?Q1 Q4 Vishal Prasada , Addisu Mesfinb , Robert Leec , Julie Reigrut, MSd , John Schmidt, PhDd,*Q2 a Medway Maritime Hospital, NHS Foundation Trust, Gillingham, Kent, United Kingdom b Department of Orthopaedics and Rehabilitation, University of Rochester, Rochester, NY, USA c Royal National Orthopaedic Hospital NHS Trust, Brockley Hill, Stanmore, Middlesex HA7 4LP, United Kingdom d K2M Inc., 751 Miller Drive, Leesburg, VA 20175, USA Received 10 November 2014; revised 25 May 2016; accepted 11 June 2016 Abstract Purpose: Although there are a significant number of research publications on the topic of bone morphology and the strength of bone, the clinical significance of a failed pedicle screw is often revision surgery and the potential for further postoperative complications; especially in elderly patients with osteoporotic bone. The purpose of this report is to quantify the mechanical strength of the foam-screw interface by assessing probe/pilot hole diameter and tap sizes using statistically relevant sample sizes under highly controlled test conditions. Methods: The study consisted of two experiments and used up to three different densities of reference-grade polyurethane foam (ASTM 1839), including 0.16, 0.24, and 0.32 g/cm3 . All screws and rods were provided by K2M Inc. and screws were inserted to a depth of 25 mm. A series of pilot holes, 1.5, 2.2, 2.7, 3.2, 3.7, 4.2, 5.0, and 6.0 mm in diameter were drilled through the entire depth of the material. A 6.5  45-mm pedicle screw was inserted and axially pulled from the material (n 5 720). A 3.0-mm pilot hole was drilled and tapped with: no tap, 3.5-, 4.5-, 5.5-, and 6.5-mm taps. A 6.5  45-mm pedicle screw was inserted and axially pulled from the material (n 5 300). Results: The size of the probe/pilot hole had a nonlinear, parabolic effect on pullout strength. This shape suggests an optimum-sized probe hole for a given size pedicle screw. Too large or too small of a probe hole causes a rapid falloff in pullout strength. The tap data demonstrated that not tapping and undertapping by two or three sizes did not significantly alter the pullout strength of the screws. The data showed an exponential falloff of pullout strength when as tap size increased to the diameter of the screw. Conclusion: In the current study, the data show that an ideal pilot hole size half the diameter of the screw is a starting point. Also, that if tapping was necessary, to use a tap two sizes smaller than the screw being implanted. A similar optimum pilot hole or tap size may be expected in the clinical scenario, however, it may not be the same as seen with the polyurethane foam tested in the current study. Ó 2016 Scoliosis Research Society. Keywords: Probe hole; Pilot hole; Tapping; Screw pullout; Polyurethane foam Introduction A PubMed Central search of bone mechanical properties revealed well over 10,000 articles including the effects of genetics, biochemical signals, man-made chemical effects, and a variety of disease states. In spite of all this research, spine surgeons still do not know the quality of the patients’ bone until they open the surgical site and ‘‘poke around.’’ In many cases, the patient undergoing spine surgery has osteoporosis. As has been stated previously, ‘‘Osteoporosis is a major generalized bone disease characterized by a low bone mass and the development of non-traumatic fractures, especially of the vertebral bodies as a direct result of osteopenia’’ [1]. Probing of the vertebral bodies is the best indicator of whether the bone is normal, osteopenic, or osteoporotic. Osteoporotic (weak) bone must be managed more carefully than normal bone. The clinical significance of a failed bone screw is often revision surgery and the potential for further postoperative complications. The holding power of a screw is also critical in deformity corrections, and although this is less of a problem in young healthy bone, it is an issue in elderly Author disclosures: VP (none); AM (none); RL (none); JR (other from K2M, Inc., during the conduct of the study; other from K2M, Inc., outside the submitted work.); JS (other from K2M Inc., during the conduct of the study). *Corresponding author. K2M, Inc., 751 Miller Drive, Leesburg, VA 20175, USA. Tel.: (703) 554-1242; fax: (703) 779-7537. E-mail address: jschmidt@k2m.com (J. Schmidt). 2212-134X/$ - see front matter Ó 2016 Scoliosis Research Society. http://dx.doi.org/10.1016/j.jspd.2016.06.001 Spine Deformity xx (2016) 1e5 www.spine-deformity.org ARTICLE IN PRESS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 FLA 5.4.0 DTD Š JSPD324_proof Š 25 July 2016 Š 11:32 pm Š ce
  3. 3. patients with osteoporotic bone. The importance of correct and positive fixation of bone screws is evident based on the number of publications on the subject. Many of these publications emphasize one particular aspect of fixation, such as probe/pilot hole [2-8] or tapping [9-12]. Typical shortcomings of these studies include the small sample size, use of cadaveric or animal bone (with very large scatter in the data), and an insufficient number of inde- pendent variables tested. To combat the shortcomings of cadaveric studies, polyurethane foam has often been used in biomechanical studies to mitigate the variability of ca- davers (cite). The intent of this study is to quantify the mechanical strength of the foam-screw interface by testing under highly controlled conditions. Testing included: Varying the probe/pilot hole diameter and then inserting a standard-size screw. Using one size pilot hole/screw and varying the tap size. Materials and Methods Two ASTM standards were used to guide the testing: ASTM F1839 and ASTM F543 [19,20]. ASTM F1839-08e1 e Standard Specification for Rigid Polyurethane Foam for Use as a Standard Material for Testing Orthopedic Devices and Instruments. Based on a literature review and previous testing, a general consensus ranking of the foam can be made. The 0.16-g/cm3 foam is similar to osteoporotic whereas the 0.32-g/cm3 foam is near normal bone mineral density and the 0.24-g/cm3 foam is in between [21-27]. All foam was purchased as sheet stock, 62 cm  244 cm  5 cm in thickness (Last-A-Foam, General Plastics, Tacoma, WA) and cut to final dimensions per ASTM F543. Pullout testing was performed parallel to the foam rise in 0.16-, 0.24-, and/or 0.32-g/cm3 foam per section A3 of the standard. There was one deviation from the standard, which was that the screws were inserted to a depth of 25 mm, not 20 mm. A standard metal bushing housed the screws prior to insertion. The bushing provided an interface with the testing machine and allowed for full contact with the head of the screw without slippage or tilting during pullout. All screws were inserted to a depth of 25 mm, using a bushing and spacer (see Fig. 1). Screws were never backed out. Axial pullout strength tests were performed on an Electropuls E3000 using Bluehill2 Software (Instron Cor- poration, Norwood, MA). The bushing around each inserted screw was placed in a custom axial pullout fixture whereas the polyurethane foam block was positioned in a base fixture clamped to the test frame base platen. Both fixtures were designed to ensure that each pedicle screw was centered directly under the load cell, Figure 1. An axial preload of 20 Æ 5 N was established followed by a tensile load at a rate of 5 mm/min until the screw released from the test block. The ultimate axial pullout strength was collected from the recorded load (N) versus displacement (mm) curve. Probe/Pilot hole size To assess the effect of the initial pilot/probe hole diameter, a series of pilot holes were drilled through the entire depth of the foam blocks. Pilot hole diameters were 1.5, 2.2, 2.7, 3.2, 3.7, 4.2, 5.0, and 6.0 mm in diameter. A 6.5  45-mm pedicle screw (K2M MESA) was inserted. Axial pull testing was performed with n 5 30 for each diameter pilot hole in each density of foam: 0.16, 0.24, and 0.32 g/cm3 (n 5 720). Tap size Based on the results of the Probe/Pilot hole study a 3.0-mm pilot hole was drilled and then tapped with the following size taps: no tap, 3.5, 4.5, 5.5, and 6.5 mm. print&web4C=FPO Fig. 1. Insertion of the screw to the standardized depth. Screws were fitted as shown and inserted by hand to a depth of 25 mm. The spacers held the bushing Q5 level during screw insertion, ensuring screws were perpendicular to the foam surface. The bushing/test block were inserted into the axial pullout fixture (right). The test block free floats in the base fixture, which is mounted to the load frame. 2 V. Prasad et al. / Spine Deformity xx (2016) 1e5 ARTICLE IN PRESS 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 FLA 5.4.0 DTD Š JSPD324_proof Š 25 July 2016 Š 11:32 pm Š ce
  4. 4. A 6.5  45-mm pedicle screw was inserted. Axial pull testing was performed for each tap size in 0.16 and 0.32 g/cm3 foam (n 5 300). All test data were analyzed using JMP 11.0 and SAS 9.4 (SAS Institute, Cary NC). Results For all plots the Maximum Load is defined as the peak pullout force in Newtons. Probe/Pilot hole size Table 1 summarizes the mean pullout strength for each probe/pilot hole tested in each of the three foams. Note that eight different pilot holes (independent variables) were assessed. Figure 2 shows the results of the testing in 0.16 g/cm3 foam (osteoporotic). The results for both the 0.24- and 0.32-g/cm3 foam show a similar shape, and all follow the general form of Y5b0 þ b1X þ b2ðX À lÞ 2 ð1Þ A look at the raw data shows that the probe/pilot hole diameter has nonlinear effect and a parabolic shape. The parabola indicates that there is an optimum probe/pilot hole for any given screw size. For the 6.5-mm-outer-diameter screw tested, that optimum appears at 2.7 mm. The regression equation and correlation coefficient (r2 ) for 0.16 g/cm3 foam were as follows: Tap size Table 2 and Figure 3 show the results of tapping a 3.0- mm pilot hole. Figure 3 shows an exponential curve with an ever- increasing rate of decline from an asymptotic value. The solid line represents the regression equation and the data fits the form of: Max loadðNÞ5a À b à expðlÃTap sizeÞ ð3Þ A nonlinear regression shows a plateau at 345.9 N for the 0.16-g/cm3 foam and 1248.93 N for the 0.32-g/cm3 foam. Max loadðNÞ5345:9 À 0:203 à expð1:011ÃTap SizeÞ ð4Þ Table 1 Mean pullout strengths. Probe hole (mm) n 0.16 g/cm3 0.24 g/cm3 0.32 g/cm3 Mean SD Mean SD Mean SD 1.5 30 377.34 15.86 767.54 45.47 1,314.66 90.31 2.25 30 394.51 23.21 771.84 26.90 1,252.65 95.82 2.7 30 373.31 14.67 767.76 51.94 1,426.15 25.80 3.2 30 405.87 17.78 737.33 46.87 1,219.27 76.26 3.7 30 367.74 21.83 682.04 65.30 1,154.41 65.60 4.25 30 341.15 16.71 607.16 28.90 1,117.47 48.89 5 30 255.45 14.31 463.50 22.27 875.60 46.33 6 30 104.80 9.41 256.99 21.37 507.65 66.39 SD, standard deviation. For each of the designated probe/pilot holes and foam densities. All values are in Newtons (N), ntotal 5 720. print&web4C=FPO Fig. 2. Effects of pilot hole size on pullout strength in 0.16 g/cm3 foam. Note the nonlinear, parabolic shape indicating an optimal pilot hole size. The pedicle screw was a 6.5-mm-diameter screw. The solid line represents the predicted values from the regression equation. Table 2 Maximum Load pullout strengths after tapping. Tap size (mm) N 0.16 g/cm3 n 0.32 g/cm3 Mean SD Mean SD 0.00 30 343.86 9.43 30 1,220.36 31.29 3.50 30 334.39 18.15 30 1,235.42 25.82 4.50 30 339.07 11.74 30 1,219.63 27.33 5.50 30 285.94 12.39 30 1,032.25 24.17 6.50 30 201.90 11.08 30 687.01 25.85 SD, standard deviation. Student t-testing was performed with alpha 5 0.05 and a critical T value of 1.97646. Note that the greatest decrease in strength for a 6.5-mm screw occurs at tap sizes greater than 4.5 mm. All values are in newtons (N); ntotal 5 300. Max load ðNÞ5551:1 À 48:90 à Hole Diam À 25:3 à ðHole Diam À 3:58Þ 2 ; r2 50:954; n5240 ð2Þ 3V. Prasad et al. / Spine Deformity xx (2016) 1e5 ARTICLE IN PRESS 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 FLA 5.4.0 DTD Š JSPD324_proof Š 25 July 2016 Š 11:32 pm Š ce
  5. 5. Discussion of Results Probe/Pilot hole The concept of an optimum probe/pilot hole has been previously proposed [2-5]. However, in each of these studies, only three or four pilot hole sizes were tested. In the testing described by George [4], the method of hole preparation involved either a drilled hole or probe hole. Eight cadaveric spine segments from three separate ca- davers provided vertebral bodies. They found no difference in pullout strength based on how the probe/pilot hole was made: drilled (mean 907.38 Æ 208.95N) or probed (mean 919.75 Æ 191.31N). This was confirmed by the work of Zdeblick [5], who also reported no difference in pullout strength based on how the probe/pilot hole was made. These studies showed that it does not matter how the hole is created; it is the size of the probe/pilot hole that determines the final holding power of the screw. Two nonlinear models were analyzed for the pilot hole data: a parabolic model, Eq. (1), and an exponential one very similar to Eq. (3). The exponential model took the form Max load5b0 À b1 à expðb2ÃHole DiameterÞ ð5Þ Both models were fit to the data, and the important metric is the residual error. Residual error is the error that cannot be accounted for by the fit of the model to the data and just like in golf, the low score wins. In all cases, the parabolic data had the lowest residual error. For the data of Figure 2, that error was as follows: parabolic 5 101,809 and exponential 5 125,994. Therefore, the parabola is the best fit. By testing eight pilot hole sizes, the true, parabolic shape of this relationship becomes apparent. The parabolic shape indicates there is an optimal size hole that should be made prior to screw insertion. For the 6.5-mm screws tested in the PU foam, the peak of the parabola, which is the optimum-sized hole, occurs at 2.6 mm. But why does the pullout strength drop off at pilot hole sizes smaller than this? The answer has to do with the materials involved. The screw is made of metal, typically stainless steel, Ti-6Al-4V, or cobalt/chrome. The modulus of the metal (Young’s modulus, E) is a measure of the stiffness, and the metals used in bone screws are roughly 10 higher than bone. Because of this mismatch, the screw will force its way, fracturing the underlying material. With the substrate fractured, the pullout strength will decrease. The idea of making a pilot hole exactly at the optimum hole size is tempting. However, because it is unusual to know the true quality of the material, a probe/pilot hole slightly larger than optimum should be considered. For the case of the 6.5-mm screw tested in the current study tested in PU foam, a pilot hole size of 3.2 mm would provide approximately a 25% margin of safety (from fracturing the underlying material) while sacrificing only 10 N in pullout strength. (These values come from the predicted values of the regression equation of Figure 2: peak 399.6 N at the 2.6-mm pilot hole, 390.9 N at the 3.2-mm pilot hole.) Tap size This aspect of the study suffers from a shortfall of the number of dependent variables, tap sizes. The number of tap sizes used in this study is a reflection of availability; all taps that could be used were utilized in this experiment. Nonetheless, the graph of Figure 3 clearly shows the effect of undertapping. Table 2 shows that the three smallest taps evaluated (0, 3.5, 4.5 mm) result in nearly identical pullout strengths. The shape of the curve in Figure 3 is the important feature. The influence of tap size on pullout strength is obvious for the larger sizes tested; both the 5.5 and 6.5 mm taps. The data illustrate that with a decreasing tap size (under- tapping), a plateau is reached where tapping the pilot hole allows for easier insertion of the screw without a decrease in pullout strength. If the tap size is too large, pullout strength literally ‘‘falls off a cliff.’’ Based on the data presented in the current study, a similar optimum pilot hole or tap size may be expected in the clinical scenario; however, it may not be the same as seen with PU foam. Limitations One limitation of this study is that it was not performed in cadavers and therefore is not representative of the print&web4C=FPO Fig. 3. The effect of tap size on probe/pilot hole tapping in 0.16-g/cm3 foam. There were small and statistically significant differences noted in the pullout strengths for each tap size. But the primary feature of the curve is the ‘‘cliff’’ that occurs just after the 4.5-mm tap size. The solid line rep- resents the predicted values from the regression equation. The pedicle screw was a 6.5-mm-diameter screw. 4 V. Prasad et al. / Spine Deformity xx (2016) 1e5 ARTICLE IN PRESS 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 FLA 5.4.0 DTD Š JSPD324_proof Š 25 July 2016 Š 11:32 pm Š ce
  6. 6. clinical situation. This study is not intended to duplicate the clinical situation. Normal bone, found in the spine, consists of a high- density cortical shell surrounding a cancellous, lower den- sity, interior. The combination of these two types of bone determines the insertion torque and pullout strength of a bone screw. The material used in this study is uniform in properties and as such cannot duplicate the combined cortical/cancellous bone found in the human spine. How- ever, the ASTM standard clearly states that polyurethane foam is ideal for testing bone screws in cancellous bone. Conclusions and Recommendations In the current study, the ideal pilot hole size in PU foam was half the diameter of the screw while data demonstrated that if tapping was necessary, to use a tap two sizes smaller than the screw being implanted. The findings of this study further emphasize the impact of pilot hole/tap sizes on screw pullout strength and suggest there are optimum sizes for both. Although a similar ideal pilot hole and tap size may be expected in a clinical sce- nario, the optimum sizes will not be the same for bone. Uncited References [13-18]. Acknowledgments We thank K2M for providing all of the instrumentation used for this study. We acknowledge the contributions of all of the summer interns who worked on this project over two years. In alphabetical order: Morgan Brown, Karli Johnson, Katherine Kamis, Daniel Schmidt, Kaci Schwarz, Griffin Smith, and Peter Williams. References [1] Ritzel H, Amling M, Posl M, et al. The thickness of human vertebral cortical bone and its changes in aging and osteoporosis: a histomor- phometric analysis of the complete spinal column from thirty-seven autopsy specimens. J Bone Miner Res 1997;12:89e95. [2] Battula S, Schoenfeld AJ, Sahai V, et al. The effect of pilot hole size on the insertion torque and pullout strength of self-tapping cortical bone screws in osteoporotic bone. J Trauma 2008;64:990e5. [3] Steeves M, Stone C, Mogaard J, et al. How pilot hole size affects bone-screw pullout strength in human cadaveric cancellous bone. Can J Surg 2005;48:207e12. [4] George DC, Krag MH, Johnson CC, et al. Hole preparation tech- niques for transpedicular screws. Effect on pull-out strength from hu- man cadaveric vertebrae. Spine 1991;16:181e4. [5] Zdeblick TA, Kunz DN, Cooke ME, McCabe R. Pedicle screw pull- out strength, correlation with insertional torque. Spine 1993;18: 1673e6. [6] Chatzistergos PE, Sapkas G, Kourkoulis S. The influence of the inser- tion technique on pullout force of pedicle screws. An experimental study. Spine 2010;35:e332e7. [7] Gantous A, Phillips JH. The effects of varying pilot hole size on the holding power of miniscrews and microscrews. Plast Reconstr Surg 1995;95:1165e9. [8] Halverson TL, Kelley LA, Thomas KA, et al. Effects of bone mineral density on pedicle screw fixation. Spine 1994;19:2415e20. [9] Kuklo TR, Lehman RA. Effect of tapping diameters on insertion of thoracic pedicle screws: a biomechanical analysis. Spine 2003;28: 2066e71. [10] Oktenoglu BT, Ferrara LA, Andalkar N, et al. Effects of pilot hole preparation on screw pullout resistance and insertional torque: a biomechanical study. J Neurosurg 2001;1:91e6. [11] Ronderos JF, Jacobwitz R, Sonntag VKH, et al. Comparative pull-out strength of tapped and untapped pilot holes for bicortical anterior cer- vical screws. Spine 1997;22:167e70. [12] Pfeiffer FM, Abernathie DL. A comparison of pullout strength for pedicle screws of different designs. A study using tapped and un- tapped pilot holes. Spine 2006;23:e867e70. [13] Choma TJ, Frevert WF, Carson WL, et al. Biomechanical analysis of pedicle screws in osteoporotic bone with bioactive cement augmenta- tion using simulated in vivo multicomponent loading. Spine 2011;36: 454e62. Q3 [14] Choma TJ, Pfeiffer FM, Swope RW, Hirner JP. Pedicle screw design and cement augmentation in osteoporotic vertebrae: effects of fenes- trations and cement viscosity on fixation and extraction. Spine 2012;37:E1628e32. [15] Waits C, Burton D, McIff T. Cement augmentation of pedicle screw fixation using novel cannulated cement insertion device. Spine 2009;34:E478e83. [16] Xi Y, Wang Y, Lu H, et al. Augmentation of pedicle screw fixation strength using an injectable calcium sulfate cement: an in vivo study. Spine 2008;33:2503e9. [17] Lowe T, O’Brien M, Smith D, et al. Central and juxta-endplate verte- bral body screw placement. A biomechanical analysis in a human cadaveric model. Spine 2002;27:369e73. [18] Rodriguewz-Olaveri JC, Hasharoni A, DeWal H, et al. The Effect of end screw orientation on the stability of anterior instrumentation in cyclic lateral loading. Spine J 2005;5:554e7. [19] ASTM F1839dRigid polyurethane foam for use as a standard mate- rial for orthopedic devices and instruments. [20] ASTM F543dStandard specification and test methods for metallic medical bone screws (specifically Section A3. Test method for deter- mining the axial pullout strength of medical bone screws). [21] Goel V, Dick D, Rengachary S, et al. Tapered pedicle screw pull out strengths; Effect of increasing screw height outside the pedicle. Sum- mer Bioengineering Conference, 2003. [22] Krenn MH, Piotrowski WP, Penzkofer R, et al. Influence of thread design on pedicle screw fixation. J Neurosurg Spine 2008;9:90e5. [23] Pfeiffer FM, Abernathie DL. A comparison of pullout strength for pedicle screws of different designs. Spine 2006;31:e867e70. [24] Chatzistergos PE, Sapkas G, Kourkoulis K. The influence of the insertion technique on the pullout force of pedicle screws: an exper- imental study. Spine 2010;35:e332e7. [25] Chao CK, Hsu CC, Wang JL, et al. Increasing bending strength and pullout strength in conical pedicle screws: biomechanical tests and finite element analyses. J Spinal Disord Tech 2008;21:130e8. [26] Patel P. Screw fixation of implants to the spine. PhD Thesis, Univer- sity of Birmingham, UK. [27] Calvert KL, Trumble KP, Webster TJ, et al. Characterization of com- mercial rigid polyurethane foams used as bone analogs for implant testing. J Mater Sci Mater Med 2010;21:1453e61. 5V. Prasad et al. / Spine Deformity xx (2016) 1e5 ARTICLE IN PRESS 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 FLA 5.4.0 DTD Š JSPD324_proof Š 25 July 2016 Š 11:32 pm Š ce

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