- Email: [email protected]
Hemivertebra Excision for Congenital Scoliosis
Hemivertebra Excision for Congenital Scoliosis Fred Mo, MD,* Matthew Cunningham, MD, PhD,†,‡ and Oheneba Boachie, MD†,‡ Hemivertebrae result from a failure of complete formation of the vertebral body and present as a challenging clinical entity. Progression and ultimate curve magnitude is associated with the degree of segmentation. An accurate assessment and a close follow-up are necessary to make appropriate treatment decisions. The goal of any intervention is to stop progression and provide the smallest degree of deformity at skeletal maturity. If a high degree of deformity is anticipated, intervention should be attempted sooner rather than later. In these cases, an in situ fusion may be appropriate. Single-stage hemivertebra excision is an effective method of both correction and stabilization; however, the procedure is technically demanding. Semin Spine Surg 24:169-173 © 2012 Published by Elsevier Inc. KEYWORDS congenital scoliosis, hemivertebra, instrumented posterior fusion, observation, resection
H
emivertebrae result from a failure of complete formation of the vertebral body and are one of the most common causes of congenital scoliosis. Various degrees of incomplete formation occur, which range from subtle to severe, and these differences correlate with relative deformity progression. In addition to the altered bone morphology, the adjacent disks may also be deficient. Most hemivertebrae possess a normal disk above and below the malformed bone, which is termed a fully segmented hemivertebra. When no disk exists either above or below, it is termed incarcerated or nonsegmented; this scenario is the least common.1 Any part of the spine may be affected, and hemivertebrae may occur at 1 or more locations. The degree of altered formation, location, number, age of the patient, and segmentation dictate the behavior of the spine as the patient grows. Scoliosis associated with fully segmented hemivertebrae progresses at a rate of 1-2 degrees per year.1,2 When the defect occurs at the lumbosacral or thoracolumbar region, a severe trunk shift may occur. A secondary compensatory curve may develop above and become structural over time. Kyphosis is also a concern, which may result in neurologic complications in patients with thoracic hemivertebrae. Semisegmented hemivertebrae cause a slowly progressive scoliotic curve that usually does not exceed 40 degrees at
*Fort Belvoir Community Hospital, Fort Belvoir, VA. †Hospital for Special Surgery, New York, NY. ‡Weill Cornell Medical College, Cornell University, New York, NY. Address reprint requests to Oheneba Boachie, MD, Hospital for Special Surgery, 535 East 70th St, New York, NY 10021. E-mail: oboachie@ gmail.com
1040-7383/$-see front matter © 2012 Published by Elsevier Inc. http://dx.doi.org/10.1053/j.semss.2012.04.007
maturity. A nonsegmented hemivertebra is synostosed above and below its adjacent vertebrae, and, typically, a progressive deformity does not occur because of the lack of growth potential. Defects in the thoracic spine tend to progress at a higher rate than those of the lumbar spine.3
Assessment An accurate assessment to determine whether the curve is progressing is paramount in choosing the appropriate intervention. Careful clinical and radiographic assessments should be made every 3 or 6 months. It is often difficult to obtain accurate radiographic measurements in patients with hemivertebrae; care should be taken when comparing radiographs. Serial follow up imaging allows an estimation of the degree of deformity at skeletal maturity. A common error in treatment of congenital scoliosis is the failure to measure radiographs accurately. Skeletal immaturity and aberrations in the vertebra contribute to difficulties in selecting measurement points. To confirm that progression has occurred, measurements have to overcome interobserver variability. Inter- and intraobserver reliability studies have been performed to assess the accuracy of measurements in congenital scoliosis. In 1 study, interobserver variability was ⫾11.8 degrees, requiring that there should be at least a 23-degree increase to determine curve progression, whereas another article showed interobserver variances to be ⫾7.86 degrees, which corresponds to a 15.7-degree increase to document progression.4-5 When documented progression occurs, it is important to act on the newfound data. 169
F. Mo, M. Cunningham, and O. Boachie
170
Figure 1 Illustrative case.
In patients with a question of intraspinal pathology, magnetic resonance imaging, computed tomography, or myelography may be warranted.
Treatment The overall goal of treatment is to prevent the development of a severe deformity. Bracing is far less effective in patients with hemivertebrae than in patients with idiopathic scoliosis.6 In cases where the degree of curvature at skeletal maturity is projected to be severe, surgery is the mainstay of care. Types of surgical intervention include posterior arthrodesis, convex-sided growth arrest, and hemivertebra excision.
Posterior Arthrodesis/Growth Arrest
Figure 2 A 3-year-old patient with low lumbar hemivertebra treated with single-stage excision and fixation.
Isolated posterior procedures have been used in the past in the treatment of hemivertebra. Posterior fusion, the most common surgical technique in the treatment of congenital scoliosis, may not alone provide the desired balance correction in patients with hemivertebrae. By only creating a fusion mass posteriorly, there is always the risk of bending of the fusion mass over time in young patients because of the crankshaft effect. Loss of correction may occur, warranting further intervention. Convex growth arrest is appropriate in patients with remaining growth potential; however, this technique must be performed early.7-9 The patient is generally ⬍5 years of age with curves ⬍50 degrees. An anterior/posterior fusion is performed on only the convex side of the deformity, and the patient is placed in a corrective cast. Close monitoring of the patient is critical because the procedure is done before the
Hemivertebra excision for congenital scoliosis
Figure 3 Illustrative case.
adolescent growth spurt. Results of growth arrest procedures can be unpredictable, but these procedures may result in actual correction of deformity with growth.
Hemivertebra Excision In 1928, Royle10 first described hemivertebra excision using a combined anterior and posterior approach. Although others
171 have shown the technique to produce definitive results with 1 operation, this operation is often technically demanding.11-14 The technique involves placing the patient in a lateral decubitus position, with the convexity of the curve up. The anterior approach is performed first. After visualizing the spine, the anomalous segment is removed by first removing the disks and then subsequently the endplates. Dissection of the hemivertebra should progress in an anterior-to-posterior fashion. In the thoracic spine, the corresponding convex rib should be removed to allow closure of the defect. The rib and the removed bone may be used for bone grafting in the resulting defect. Meticulous hemostasis is achieved, and the wound is closed. The patient is then placed in a prone position; dissection is carried down to the appropriate level. The lamina and transverse process of the hemivertebra are removed, as well as any remaining pedicle. Correction at this point may be achieved before segmental stabilization. Forces may be applied manually or by using a large clamp above and below the targeted segment. The laminae and facets at the level above and below the hemivertebra are decorticated and prepared for fusion. Bone graft is placed, and the wound is then closed. Illustrative cases are shown in Figs. 1-5.
Discussion Congenital scoliotic curves resulting from hemivertebrae encompass a challenging clinical entity. The primary goal of surgical intervention is to halt the progression of the curve and maintain spinal balance. Previous approaches involved fusion of the curve without significant correction, termed “fusion in situ.” Loss of motion of a large spinal segment, loss of future growth, and potential progression because of fur-
Figure 4 A 2-year-old patient with thoracic hemivertebra treated with excision and fusion. (Color version of figure is available online)
F. Mo, M. Cunningham, and O. Boachie
172
Figure 5 Postoperative view of patient in Fig. 4. (Color version of figure is available online.)
ther growth of the young patient are all potential disadvantages of this technique. Convex-sided growth arrest has also emerged as a potential treatment option; however, the number of patients who fit the indications is limited, and in addition, the outcomes are not always predictable. Hemivertebra excision, although technically demanding, provides a definitive treatment in the sense that future curve progression is eliminated with immediate correction of the underlying deformity.15-16 The extent of fusion required is also shorter compared with in situ fusion. Considerations in preoperative planning include which hemivertebrae require resection, how many additional vertebrae to include in the fusion, when to intervene (Cobb measurement vs best age), and whether a staged or combined procedure should be used. In cases where a fully segmented hemivertebra is located at the lumbosacral junction, early intervention is important to prevent severe deformity. Considerations should also be made to intervene early in cases of kyphosis. Early studies have recommended 2-stage procedures versus single-stage combined resections in the treatment of hemivertebra. Multiple recent reports have shown that single-stage vertebral excision is safe and effective. In a series of 6 patients who were treated with single-stage anterior–posterior surgery, the average long-term correction of the curve was noted to be 46%, with good long-term follow-up.17 Some have advocated for a posterior-only approach. Nakamura et al performed hemivertebra excision with an all-posterior approach in a series of 5 patients and showed a correction of 54.3% in the coronal plane and 67.4% for kyphosis, with minimal loss of correction after long-term follow-up. When comparing anterior–posterior single-stage surgery with pos-
terior-alone approach, time of surgery was faster in cases treated with posterior-alone approach; however, complication rates were significantly higher. Mean correction of the curves was similar.18-19 When comparing the different types of treatment modalities for congenital hemivertebra, hemivertebra excision offers immediate correction with stable long-term results, obviating the need for further treatments.
Disclosure The authors have no financial arrangements or conflicts of interest that influenced the work described in this manuscript and received no grants for this project.
References 1. McMaster MJ, Ohtsuka K: The natural history of congenital scoliosis: a study of two hundred and fifty-one patients. J Bone Joint Surg Am 64:1128-1147, 1982 2. McMaster MJ, David CV: Hemivertebra as a cause of scoliosis. A study of 104 patients. J Bone Joint Surg Br 68:588-595, 1986 3. Winter RB, Lonstein JE, Denis F, et al: Convex growth arrest for progressive congenital scoliosis due to hemivertebrae. J Pediatr Orthop 8:633-638, 1988 4. Facanha-Filho FA, Winter RB, Lonstein JE, et al: Measurement accuracy in congenital scoliosis. J Bone Joint Surg Am 83-A:42-45, 2001 5. Loder RT, Urquhart A, Steen H, et al: Variability in Cobb angle measurements in children with congenital scoliosis. J Bone Joint Surg Br 77:768-770, 1995 6. Winter RB: Congenital scoliosis. Clin Orthop Relat Res Jun 93:75-94, 1973 7. Dubousset J, Katti E, Seringe R: Epiphysiodesis of the spine in young children for congenital spinal deformations. J Pediatr Orthop Part B 1:123-130, 1993
Hemivertebra excision for congenital scoliosis 8. Cheung KM, Zhang JG, Lu DS, et al: Ten-year follow-up study of lower thoracic hemivertebrae treated by convex fusion and con-cave distraction. Spine 27:748-753, 2002 9. Andrew T, Piggott H: Growth arrest for progressive scoliosis: combined anterior and posterior fusion of the convexity. J Bone Joint Surg Br 67:193-197, 1985 10. Royle ND: The operative removal of an accessory vertebrae. Med J Aust 1:467-468, 1928 11. McMaster MJ, David CV: Hemivertebrae as a cause of scoliosis. J Bone Joint Surg Br 68:588-595, 1986 12. Holte DC, Winter RB, Lonstein JE, et al: Excision of hemivertebrae and wedge resection in the treatment of congenital scoliosis. A study of 104 patients. J Bone Joint Surg Am 77:159-171, 1995 13. Bradford DS, Boachie-Adjei O: One-stage anterior and posterior hemivertebral resection and arthrodesis for congenital scoliosis. J Bone Joint Surg Am 72:536-540, 1990 14. Bollini G, Docquier PL, Viehweger E, et al: Lumbar hemivertebra resection. J Bone Joint Surg Am 88:1043-1052, 2006
173 15. Ruf M, Jensen R, Jeszenszky D, et al: Hemivertebra resection in congenital scoliosis—Early correction in young children. Z Orthop Ihre Grenzgeb 144:74-79, 2006 16. King JD, Lowery GL: Results of lumbar hemivertebral excision for congenital scoliosis. Spine 16:778-782, 1991 17. Leong JC, Day GA, Luk KD, et al: Nine-year mean follow-up of onestage anteroposterior excision of hemivertebrae in the lumbosacral spine. Spine 18:2069-2074, 1993 18. Nakamura H, Matsuda H, Konishi S, et al: Single-stage excision of hemivertebrae via the posterior approach alone for congenital spine deformity: follow-up period longer than ten years. Spine 27:110-115, 2002 19. Jalanko T, Rintala R, Puisto V, et al: Hemivertebra resection for congenital scoliosis in young children: comparison of clinical, radiographic, and health-related quality of life outcomes between the anteroposterior and posterolateral approaches. Spine (Phila Pa 1976) 36: 41-49, 2011
H
emivertebrae result from a failure of complete formation of the vertebral body and are one of the most common causes of congenital scoliosis. Various degrees of incomplete formation occur, which range from subtle to severe, and these differences correlate with relative deformity progression. In addition to the altered bone morphology, the adjacent disks may also be deficient. Most hemivertebrae possess a normal disk above and below the malformed bone, which is termed a fully segmented hemivertebra. When no disk exists either above or below, it is termed incarcerated or nonsegmented; this scenario is the least common.1 Any part of the spine may be affected, and hemivertebrae may occur at 1 or more locations. The degree of altered formation, location, number, age of the patient, and segmentation dictate the behavior of the spine as the patient grows. Scoliosis associated with fully segmented hemivertebrae progresses at a rate of 1-2 degrees per year.1,2 When the defect occurs at the lumbosacral or thoracolumbar region, a severe trunk shift may occur. A secondary compensatory curve may develop above and become structural over time. Kyphosis is also a concern, which may result in neurologic complications in patients with thoracic hemivertebrae. Semisegmented hemivertebrae cause a slowly progressive scoliotic curve that usually does not exceed 40 degrees at
*Fort Belvoir Community Hospital, Fort Belvoir, VA. †Hospital for Special Surgery, New York, NY. ‡Weill Cornell Medical College, Cornell University, New York, NY. Address reprint requests to Oheneba Boachie, MD, Hospital for Special Surgery, 535 East 70th St, New York, NY 10021. E-mail: oboachie@ gmail.com
1040-7383/$-see front matter © 2012 Published by Elsevier Inc. http://dx.doi.org/10.1053/j.semss.2012.04.007
maturity. A nonsegmented hemivertebra is synostosed above and below its adjacent vertebrae, and, typically, a progressive deformity does not occur because of the lack of growth potential. Defects in the thoracic spine tend to progress at a higher rate than those of the lumbar spine.3
Assessment An accurate assessment to determine whether the curve is progressing is paramount in choosing the appropriate intervention. Careful clinical and radiographic assessments should be made every 3 or 6 months. It is often difficult to obtain accurate radiographic measurements in patients with hemivertebrae; care should be taken when comparing radiographs. Serial follow up imaging allows an estimation of the degree of deformity at skeletal maturity. A common error in treatment of congenital scoliosis is the failure to measure radiographs accurately. Skeletal immaturity and aberrations in the vertebra contribute to difficulties in selecting measurement points. To confirm that progression has occurred, measurements have to overcome interobserver variability. Inter- and intraobserver reliability studies have been performed to assess the accuracy of measurements in congenital scoliosis. In 1 study, interobserver variability was ⫾11.8 degrees, requiring that there should be at least a 23-degree increase to determine curve progression, whereas another article showed interobserver variances to be ⫾7.86 degrees, which corresponds to a 15.7-degree increase to document progression.4-5 When documented progression occurs, it is important to act on the newfound data. 169
F. Mo, M. Cunningham, and O. Boachie
170
Figure 1 Illustrative case.
In patients with a question of intraspinal pathology, magnetic resonance imaging, computed tomography, or myelography may be warranted.
Treatment The overall goal of treatment is to prevent the development of a severe deformity. Bracing is far less effective in patients with hemivertebrae than in patients with idiopathic scoliosis.6 In cases where the degree of curvature at skeletal maturity is projected to be severe, surgery is the mainstay of care. Types of surgical intervention include posterior arthrodesis, convex-sided growth arrest, and hemivertebra excision.
Posterior Arthrodesis/Growth Arrest
Figure 2 A 3-year-old patient with low lumbar hemivertebra treated with single-stage excision and fixation.
Isolated posterior procedures have been used in the past in the treatment of hemivertebra. Posterior fusion, the most common surgical technique in the treatment of congenital scoliosis, may not alone provide the desired balance correction in patients with hemivertebrae. By only creating a fusion mass posteriorly, there is always the risk of bending of the fusion mass over time in young patients because of the crankshaft effect. Loss of correction may occur, warranting further intervention. Convex growth arrest is appropriate in patients with remaining growth potential; however, this technique must be performed early.7-9 The patient is generally ⬍5 years of age with curves ⬍50 degrees. An anterior/posterior fusion is performed on only the convex side of the deformity, and the patient is placed in a corrective cast. Close monitoring of the patient is critical because the procedure is done before the
Hemivertebra excision for congenital scoliosis
Figure 3 Illustrative case.
adolescent growth spurt. Results of growth arrest procedures can be unpredictable, but these procedures may result in actual correction of deformity with growth.
Hemivertebra Excision In 1928, Royle10 first described hemivertebra excision using a combined anterior and posterior approach. Although others
171 have shown the technique to produce definitive results with 1 operation, this operation is often technically demanding.11-14 The technique involves placing the patient in a lateral decubitus position, with the convexity of the curve up. The anterior approach is performed first. After visualizing the spine, the anomalous segment is removed by first removing the disks and then subsequently the endplates. Dissection of the hemivertebra should progress in an anterior-to-posterior fashion. In the thoracic spine, the corresponding convex rib should be removed to allow closure of the defect. The rib and the removed bone may be used for bone grafting in the resulting defect. Meticulous hemostasis is achieved, and the wound is closed. The patient is then placed in a prone position; dissection is carried down to the appropriate level. The lamina and transverse process of the hemivertebra are removed, as well as any remaining pedicle. Correction at this point may be achieved before segmental stabilization. Forces may be applied manually or by using a large clamp above and below the targeted segment. The laminae and facets at the level above and below the hemivertebra are decorticated and prepared for fusion. Bone graft is placed, and the wound is then closed. Illustrative cases are shown in Figs. 1-5.
Discussion Congenital scoliotic curves resulting from hemivertebrae encompass a challenging clinical entity. The primary goal of surgical intervention is to halt the progression of the curve and maintain spinal balance. Previous approaches involved fusion of the curve without significant correction, termed “fusion in situ.” Loss of motion of a large spinal segment, loss of future growth, and potential progression because of fur-
Figure 4 A 2-year-old patient with thoracic hemivertebra treated with excision and fusion. (Color version of figure is available online)
F. Mo, M. Cunningham, and O. Boachie
172
Figure 5 Postoperative view of patient in Fig. 4. (Color version of figure is available online.)
ther growth of the young patient are all potential disadvantages of this technique. Convex-sided growth arrest has also emerged as a potential treatment option; however, the number of patients who fit the indications is limited, and in addition, the outcomes are not always predictable. Hemivertebra excision, although technically demanding, provides a definitive treatment in the sense that future curve progression is eliminated with immediate correction of the underlying deformity.15-16 The extent of fusion required is also shorter compared with in situ fusion. Considerations in preoperative planning include which hemivertebrae require resection, how many additional vertebrae to include in the fusion, when to intervene (Cobb measurement vs best age), and whether a staged or combined procedure should be used. In cases where a fully segmented hemivertebra is located at the lumbosacral junction, early intervention is important to prevent severe deformity. Considerations should also be made to intervene early in cases of kyphosis. Early studies have recommended 2-stage procedures versus single-stage combined resections in the treatment of hemivertebra. Multiple recent reports have shown that single-stage vertebral excision is safe and effective. In a series of 6 patients who were treated with single-stage anterior–posterior surgery, the average long-term correction of the curve was noted to be 46%, with good long-term follow-up.17 Some have advocated for a posterior-only approach. Nakamura et al performed hemivertebra excision with an all-posterior approach in a series of 5 patients and showed a correction of 54.3% in the coronal plane and 67.4% for kyphosis, with minimal loss of correction after long-term follow-up. When comparing anterior–posterior single-stage surgery with pos-
terior-alone approach, time of surgery was faster in cases treated with posterior-alone approach; however, complication rates were significantly higher. Mean correction of the curves was similar.18-19 When comparing the different types of treatment modalities for congenital hemivertebra, hemivertebra excision offers immediate correction with stable long-term results, obviating the need for further treatments.
Disclosure The authors have no financial arrangements or conflicts of interest that influenced the work described in this manuscript and received no grants for this project.
References 1. McMaster MJ, Ohtsuka K: The natural history of congenital scoliosis: a study of two hundred and fifty-one patients. J Bone Joint Surg Am 64:1128-1147, 1982 2. McMaster MJ, David CV: Hemivertebra as a cause of scoliosis. A study of 104 patients. J Bone Joint Surg Br 68:588-595, 1986 3. Winter RB, Lonstein JE, Denis F, et al: Convex growth arrest for progressive congenital scoliosis due to hemivertebrae. J Pediatr Orthop 8:633-638, 1988 4. Facanha-Filho FA, Winter RB, Lonstein JE, et al: Measurement accuracy in congenital scoliosis. J Bone Joint Surg Am 83-A:42-45, 2001 5. Loder RT, Urquhart A, Steen H, et al: Variability in Cobb angle measurements in children with congenital scoliosis. J Bone Joint Surg Br 77:768-770, 1995 6. Winter RB: Congenital scoliosis. Clin Orthop Relat Res Jun 93:75-94, 1973 7. Dubousset J, Katti E, Seringe R: Epiphysiodesis of the spine in young children for congenital spinal deformations. J Pediatr Orthop Part B 1:123-130, 1993
Hemivertebra excision for congenital scoliosis 8. Cheung KM, Zhang JG, Lu DS, et al: Ten-year follow-up study of lower thoracic hemivertebrae treated by convex fusion and con-cave distraction. Spine 27:748-753, 2002 9. Andrew T, Piggott H: Growth arrest for progressive scoliosis: combined anterior and posterior fusion of the convexity. J Bone Joint Surg Br 67:193-197, 1985 10. Royle ND: The operative removal of an accessory vertebrae. Med J Aust 1:467-468, 1928 11. McMaster MJ, David CV: Hemivertebrae as a cause of scoliosis. J Bone Joint Surg Br 68:588-595, 1986 12. Holte DC, Winter RB, Lonstein JE, et al: Excision of hemivertebrae and wedge resection in the treatment of congenital scoliosis. A study of 104 patients. J Bone Joint Surg Am 77:159-171, 1995 13. Bradford DS, Boachie-Adjei O: One-stage anterior and posterior hemivertebral resection and arthrodesis for congenital scoliosis. J Bone Joint Surg Am 72:536-540, 1990 14. Bollini G, Docquier PL, Viehweger E, et al: Lumbar hemivertebra resection. J Bone Joint Surg Am 88:1043-1052, 2006
173 15. Ruf M, Jensen R, Jeszenszky D, et al: Hemivertebra resection in congenital scoliosis—Early correction in young children. Z Orthop Ihre Grenzgeb 144:74-79, 2006 16. King JD, Lowery GL: Results of lumbar hemivertebral excision for congenital scoliosis. Spine 16:778-782, 1991 17. Leong JC, Day GA, Luk KD, et al: Nine-year mean follow-up of onestage anteroposterior excision of hemivertebrae in the lumbosacral spine. Spine 18:2069-2074, 1993 18. Nakamura H, Matsuda H, Konishi S, et al: Single-stage excision of hemivertebrae via the posterior approach alone for congenital spine deformity: follow-up period longer than ten years. Spine 27:110-115, 2002 19. Jalanko T, Rintala R, Puisto V, et al: Hemivertebra resection for congenital scoliosis in young children: comparison of clinical, radiographic, and health-related quality of life outcomes between the anteroposterior and posterolateral approaches. Spine (Phila Pa 1976) 36: 41-49, 2011