1. The Use of Pedicle-Screw Internal Fixation for the Operative Treatment of Spinal Disorders*
by Robert W. Gaines
J Bone Joint Surg Am
Volume 82(10):
October 1, 2000
©2000 by The Journal of Bone and Joint Surgery, Inc.

2. The Roy-Camille plate137,138 (left) and the Steffee variable-screw-placement (VSP) plate152 (right).
The Roy-Camille plate137,138 (left) and the Steffee variable-screw-placement (VSP) plate152 (right). The former plate, with its fixed screw-hole distances, was not able to accommodate the individual patient anatomy as well as the latter plate.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

3. Drawings clearly illustrating the benefits of screw triangulation to improve pullout strength, particularly when the screws are cross-connected to one another9.
Drawings clearly illustrating the benefits of screw triangulation to improve pullout strength, particularly when the screws are cross-connected to one another9. (Reprinted, with permission, from: Barber, J. W.; Boden, S. D.; Ganey, T.; and Hutton, W. C.: Biomechanical study of lumbar pedicle screws: does convergence affect axial pullout strength? J. Spinal Disord., 11: 216, 1998.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

4. The 4R-4bar linkage collapse associated with parallel pedicle screws (left) can be resisted only by load-sharing through the fracture site (right)23.
The 4R-4bar linkage collapse associated with parallel pedicle screws (left) can be resisted only by load-sharing through the fracture site (right)23.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

5. The "JIKEI Index" easily relates bone-mineral density and pedicle-screw pullout strength with this simple x-ray-based scheme.
The "JIKEI Index" easily relates bone-mineral density and pedicle-screw pullout strength with this simple x-ray-based scheme. Pullout strength is severely limited when there are spontaneous compression fractures as in stages 2 and 3. Pedicle-screw fixation is contraindicated when there is this much osseous deterioration151. (Reprinted, with permission, from: Soshi, S.; Shiba, R.; Kondo, H.; and Murota, K.: An experimental study on transpedicular screw fixation in relation to osteoporosis of the lumbar spine. Spine, 16: 1336, 1991.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

6. Model developed by the American Society for Testing and Materials for construct or subconstruct testing.
Model developed by the American Society for Testing and Materials for construct or subconstruct testing. Polyethylene blocks are used to mimic vertebral bodies. Here, under axial load, spinal deformity secondary to distortion at the longitudinal member-connector interface is seen34,60. (Reprinted, with permission, from: Cunningham, B. W.; Sefter, J. C.; Shono, V.; and McAfee, P. C.: Static and cyclical biomechanical analysis of pedicle screw spinal constructs. Spine, 18: 1680, 1993.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

7. Bar graphs showing the changes in pullout force (A) and bending stiffness (B) when screws with five and six-millimeter major diameters are compared.
Bar graphs showing the changes in pullout force (A) and bending stiffness (B) when screws with five and six-millimeter major diameters are compared. Improvements in both parameters are related directly to the major diameter of the screw170,179. (Reprinted, with permission, from: Wittenberg, R. H.; Lee, K.-S.; Shea, M.; White, A. A., III; and Hayes, W. C.: Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength. Clin. Orthop., 296: 282, 1993.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

8. Bar graphs showing differences in resistance to cyclic loading34.
Bar graphs showing differences in resistance to cyclic loading34. All of these implant systems have been used extensively, although their biomechanical performance differs dramatically. The healing of the fusion is much better in patients with stiffer implants34. VSP = variable screw placement (Steffee) plate, KPL = Kirschner plate, DLO = Dyna-lok plate, ISO = Isola rod, TSR = Texas Scottish Rite Hospital rod, CCD = Compact CD (Cotrel-Dubousset) rod, CDC = CD cold rolled rod, FIX = AO fixateur interne, CDS = CD standard rod, and KRO = Kirschner rod. (Reprinted, with permission, from: Cunningham, B. W.; Sefter, J. C.; Shono, V.; and McAfee, P. C.: Static and cyclical biomechanical analysis of pedicle screw spinal constructs. Spine, 18: 1681, 1993.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

9. Photographs illustrating the Funnel Technique.
Photographs illustrating the Funnel Technique. A: The dorsal projection of the pedicle (red circle) is localized. B: A one-centimeter-diameter section of cortical bone is removed over the top of the pedicle with a burr or Lexcel rongeur. C: The cancellous bone within the pedicle is then visualized. D: The cancellous bone is removed with a curet until the cortical wall of the pedicle can be felt and visualized. This is followed by going deeper into the pedicle toward the isthmus. E: The Kerrison rongeur is used to remove the cortical bone peripherally so that the isthmus of the pedicle can be seen. F: Once the isthmus of the pedicle is directly palpated, a small two-millimeter pedicle probe is passed through the isthmus into the vertebral body. G: A larger (five-millimeter) probe then is used to enlarge the path through the isthmus of the pedicle. H andI: Small Steinmann pin segments (fifty-five millimeters in length) are placed into the probed pedicles as radiographic markers. (The anteroposterior [H] and lateral [I] c-arm images confirm the pedicle path. The lateral c-arm image [I] also confirms the length of the screw to be used; the depth of each Steinmann pin is measured after it is removed.) J: Threads then are cut into the pedicle with progressively larger taps until firm cortical purchase is achieved. The feel achieved during the tapping process determines the screw diameter that is used. K: A ball-tip probe is used to feel the pedicle in all directions: the bottom of the pedicle (in the vertebral body) and the superior, inferior, medial, and lateral inner walls of the pedicle. L: The screw then is inserted into the pedicle with the screwdriver. The purchase (insertional torque) must progressively increase until final seating. M: The anteroposterior and lateral c-arm images confirm proper positioning after all of the screws, rods, and connectors are inserted. (Grateful appreciation to Byron R. Tarbox, M.D., Wicharn Yingsakmongkol, M.D., Michael R. Viau, M.D., and Eldin E. Karaikovic, M.D., Ph.D., for assistance with the "funnel technique.")‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

10. Graph showing improved screw-bending stiffness due to the addition of polymethylmethacrylate (PMMA) and polypropylene glycol-fumarate (PPF).
Graph showing improved screw-bending stiffness due to the addition of polymethylmethacrylate (PMMA) and polypropylene glycol-fumarate (PPF). (Reprinted, with permission, from: Wittenberg, R. H.; Lee, K.-S.; Shea, M.; White, A. A., III; and Hayes, W. C.: Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength. Clin. Orthop., 296: 284, 1993.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

11. The load-sharing classification permits quantification of comminution of spinal fracture sites so that the load-sharing capability of the injured vertebral body itself, along with the implant system, can be determined.
The load-sharing classification permits quantification of comminution of spinal fracture sites so that the load-sharing capability of the injured vertebral body itself, along with the implant system, can be determined. This approach has allowed surgeons to perform short-segment fixation for most isolated spinal fractures in cooperative patients103,127. A: Comminution/involvement. 1 = little comminution (less than 30 percent), 2 = more comminution (30 to 60 percent), and 3 = gross comminution (more than 60 percent) on computed tomographic sagittal plane sections. B: Apposition of fragments. 1 = minimal displacement, 2 = spread of displacement (at least two millimeters of displacement of less than 50 percent of the cross section of the body), and 3 = wide displacement (at least two millimeters of displacement of more than 50 percent of the cross section of the body). C: Deformity correction. 1 = kyphotic correction of 3 degrees or less, 2 = kyphotic correction of 4 to 9 degrees, and 3 = kyphotic correction of 10 degrees or more on lateral plain radiographs. (Reprinted, with permission, from: McCormack, T.; Karaikovic, E.; and Gaines, R. W.: The load sharing classification of spine fractures. Spine, 19: 1742, 1994.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

12. Figs. 11-A through 11-E: A patient with severe thoracic scoliosis who had excellent correction of both the primary curve and the tilt angle with use of pedicle screws for the caudal platform.
Figs. 11-A through 11-E: A patient with severe thoracic scoliosis who had excellent correction of both the primary curve and the tilt angle with use of pedicle screws for the caudal platform. The screws' ability to control the caudal segments in the fusion in a very secure manner allowed much better realignment of the tilt angle than would have been possible with only hook systems10,67.Fig. 11-A: Posteroanterior and forward-bending posteroanterior photographs.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

13. Posteroanterior radiographs demonstrating an 88-degree curve with the patient standing and a 53-degree right thoracic curve with the patient stretching.
Posteroanterior radiographs demonstrating an 88-degree curve with the patient standing and a 53-degree right thoracic curve with the patient stretching.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

14. Posteroanterior radiograph made ten months postoperatively, demonstrating correction and restored compensation.
Posteroanterior radiograph made ten months postoperatively, demonstrating correction and restored compensation.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

15. Postoperative posteroanterior and forward-bending posteroanterior photographs, demonstrating good balance and mobility in the lumbar spine.
Postoperative posteroanterior and forward-bending posteroanterior photographs, demonstrating good balance and mobility in the lumbar spine.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

16. Preoperative and postoperative standing lateral radiographs demonstrating correction of the midthoracic kyphotic deformity.
Preoperative and postoperative standing lateral radiographs demonstrating correction of the midthoracic kyphotic deformity.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

17. Intermediate-grade spondylolisthesis and/or degenerative spondylolisthesis can now be well treated with reduction with the posterior approach only, with use of interbody fusion with cages and pedicle screws.
Intermediate-grade spondylolisthesis and/or degenerative spondylolisthesis can now be well treated with reduction with the posterior approach only, with use of interbody fusion with cages and pedicle screws. The union rate is very high, and straightforward reduction of intermediate slips is safe neurologically, provided that the roots are visualized and protected carefully during the procedure.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

18. Reconstruction of spinal fractures is much more secure with pedicle screws.
Reconstruction of spinal fractures is much more secure with pedicle screws. In this patient, realignment of adjacent-level injuries at the third and fourth thoracic vertebrae was accomplished with short-segment pedicle-screw instrumentation in the second and fifth thoracic vertebrae. (Case contributed by Dr. Marc Asher.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

19. Figs. 14-A through 14-D: Spinal osteotomy has become a much more predictable surgical technique since the adoption of pedicle screws, which provide more secure fixation than any previous technique.Fig. 14-A: The site of the corrective osteotomy should be at...
Figs. 14-A through 14-D: Spinal osteotomy has become a much more predictable surgical technique since the adoption of pedicle screws, which provide more secure fixation than any previous technique.Fig. 14-A: The site of the corrective osteotomy should be at the apex of the deformity, with removal of the laminar arch, the pedicles, and the part of the vertebral body and disc that represent the apex of the deformity.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

20. This patient had a post-fracture flatback deformity after Harrington instrumentation, with fixed deformity in the lumbar spine.
This patient had a post-fracture flatback deformity after Harrington instrumentation, with fixed deformity in the lumbar spine. The osteotomy was performed through the third lumbar level.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

21. Close-up preoperative and postoperative lateral radiographs.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

22. Preoperative and postoperative lateral photographs showing dramatic realignment.
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.

23. In tumor reconstructions, pedicle screws permit segmental resection, realignment, and reconstruction over shorter segments than was possible before their introduction.
In tumor reconstructions, pedicle screws permit segmental resection, realignment, and reconstruction over shorter segments than was possible before their introduction. In this patient, a chordoma of the sacrum was resected, and reconstruction was performed with use of short-segment anterior and posterior approaches along with pedicle screws and sacral and iliac screws155. (Case contributed by Dr. Stefano Boriani.)‏
Robert W. Gaines, Jr. J Bone Joint Surg Am 2000;82:1458
©2000 by The Journal of Bone and Joint Surgery, Inc.