Radiographic assessment of congenital C2-3 synostosis

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1 Journal of Orthopaedic Surgery 2010;18(2):143-7 Radiographic assessment of congenital C2-3 synostosis Myung-Sang Moon, 1 Sung-Soo Kim, 1 Bong-Jin Lee, 1 Jeong-Lim Moon, 2 Jin-Fu Lin, 3 Young-Wan Moon 4 1 Department of Orthopaedic Surgery, Cheju Halla General Hospital, Jeju, Korea 2 Department of Rehabilitation Medicine, Catholic University of Korea, Seoul, Korea 3 Department of Spine Surgery, Taipei Hospital, Taipei, Taiwan 4 Department of Orthopaedic Surgery, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea ABSTRACT Purpose. To evaluate the morphologies of congenital C2-3 synostosis in 25 patients. Methods. Radiographs of 11 males and 14 females aged 5 to 74 years with congenital C2-3 synostosis were reviewed. All cases were found incidentally on radiographs when presenting with neck/shoulder discomfort/pain. Results. 13 of the patients had spondylosis in 21 segments: C1-2 (n=1) and C3-4 (n=1), C4-5 (n=7), C5-6 (n=9), and C6-7 (n=3). Of whom 12 had normal sagittal alignment and one had kyphotic synostosis (who developed compensatory hyperlordosis of the caudal mobile segments and subsequent spondylosis at C3-4 and C5 retrolisthesis). The remaining 12 patients had no spondylosis and had normal sagittal alignment, but had other associated pathologies including disc herniation at C3-4, C1 ring hypoplasia, and calcification of the nuchal ligament. Conclusion. Normally aligned congenital synostosis of C2-3 is rarely associated with a junctional problem, whereas a kyphotic synostosis is associated with a caudal junctional problem. Spondylosis developing after age 40 years is not associated with C2-3 synostosis. Key words: cervical vertebrae; congenital abnormalities; synostosis; zygapophyseal joint INTRODUCTION Congenital cervical block vertebra is considered an incidental radiological finding unrelated to disease, 1 but others consider it causes secondary degenerative changes and mobility disturbances of adjacent segments in the same manner as iatrogenically created immobile segments. 1 8 No quantitative data have been presented to support these differing opinions. 9 We evaluated the morphologies of congenital C2-3 synostosis in the cephlad and caudal adjacent discs and facet joints of 25 patients. MATERIALS AND METHODS Radiographs of 11 males and 14 females aged 5 to Address correspondence and reprint requests to: Dr Young-Wan Moon, Department of Orthopedic Surgery, Samsung Medical Center, Sungkyunkwan University, 50 Ilwon-dong, Kangnam-ku, Seoul, , Korea. ywmoon@skku.edu

2 144 MS Moon et al. Journal of Orthopaedic Surgery Patient age (years) Table Distribution of the 21 spondylotic segments in 13 patients with spondylosis * A 40-year-old woman with C1-2 left facet arthrosis and normal sagittal alignment A 43-year-old woman with kyphotic synostosis No. of spondylotic segments in Male/female C1-2 C3-4 C4-5 C5-6 C /1 0/1 * 0/0 0/0 0/0 0/ /4 0/0 0/1 2/1 2/2 1/ /5 0/0 0/0 1/2 3/2 1/ /1 0/0 0/0 0/1 0/0 0/0 Total 10/11 0/1 0/1 3/4 5/4 2/1 74 years with congenital C2-3 synostosis obtained at 6 hospitals between April 1995 and July 2009 were reviewed. All cases were found incidentally on radiographs; no patient presented with a shortneck appearance. The patients complaints included neck/shoulder discomfort/pain (n=25), neck motion limitation (n=1), an acute wry neck possibly an atlantoaxial rotatory subluxation (n=1, 5-yearold boy), and post-traumatic transient myelopathy symptoms (n=1, 44-year-old man). RESULTS 13 of the 25 patients had spondylosis in 21 segments: C1-2 (n=1) and C3-4 (n=1), C4-5 (n=7), C5-6 (n=9), and C6-7 (n=3) [Table]. Of whom 12 had normal sagittal alignment, and one had kyphotic synostosis who developed compensatory hyperlordosis of the caudal mobile segments and subsequent spondylosis at C3-4 and C5 retrolisthesis (Fig. 1). 11 of the 12 patients with normal sagittal alignment had 2- to 3-segment spondylosis between C4 and C7 (19 segments). The remaining 2 spondylotic segments occurred at C1-2 in a 40-year-old woman (Fig. 2) and at C3-4 in the patient with kyphotic synostosis. Four males and 4 females had one spondylotic segment, 2 males and 2 females had 2 spondylotic segments, and one female had 3 spondylotic segments (Fig. 3). The remaining 12 patients had no spondylosis and had normal sagittal alignment, but had other associated pathologies including disc herniation at C3-4 (in a 43-year-old woman), C1 ring hypoplasia (in a 44-year-old woman), posterior C1 ring hypoplasia (in a 44-year-old man), and calcification of the nuchal ligament (in a 48-year-old man). Figure 1 A 43-year-old woman with kyphotic C2-3 synostosis develops spondylosis at C3-4, compensatory hyperlordosis of the caudal mobile segments, and C5 retrolisthesis. Figure 2 A 40-year-old woman with C2-3 synostosis develops left atlantoaxial facet arthrosis. No degenerative disc disease is seen at the caudal mobile segment.

3 Vol. 18 No. 2, August 2010 Radiographic assessment of congenital C2-3 synostosis 145 (a) (b) (c) Figure 3 (a) One-segment spondylosis at C5-6 in a 51- and a 54-year-old women, (b) 2-segment spondylosis at C4-5 and C6-7 in a 55-year-old man, and (c) 3-segment spondylosis at C4-5, C5-6, and C6-7 in a 52-year-old man. Figure 4 A 5-year-old boy develops acute torticollis, without cervical disc degeneration, segmental instability, and other anomaly. Torticollis is probably caused by the atlantoaxial rotatory subluxation after flu, rather than C2-3 synostosis, as it reduces spontaneously. DISCUSSION Congenital cervical synostosis may alter kinematics and exert extra stress on adjacent unfused/mobile segments, and result in progressive joint degeneration and segmental instability. 2 7,9 14 Adjacent joint disease was associated with patient age, presumably due to differences in physical adaptability to stress between children and adults. 7,8 In our study, a 5-year-old boy developed acute torticollis after flu, probably caused by atlantoaxial rotatory subluxation, rather than C2-3 synostosis, as it reduced spontaneously (Fig. 4). However, arthrosis of the left atlantoaxial (C1-2) facet joint in a 40-yearold woman with normal sagittal alignment was considered to be associated with C2-3 synostosis (Fig. 2). Whether caudal joint changes below C4 were associated with C2-3 synostosis remain unknown. Such changes might have been more related to constitutional factors than stresses arising from the C2-3 synostosis. Moreover, degenerative disc changes at caudal mobile segments below C4 were not encountered in 12 patients aged <40 years with a normally aligned synostosis (Fig. 5), whereas spondylosis in 12 patients with normally aligned synostosis were found at the non-adjacent caudal mobile segments. Only the 43-year-old female with kyphotic synostosis had spondylosis at the adjacent caudal joint with C5 retrolisthesis (Fig. 1). Thus, spondylosis should be assumed to be produced by natural ageing, unrelated to C2-3 synostosis and malalignment. We speculated that normally aligned C2-3 synostosis does not affect adjacent caudal joints despite altered biomechanics. Thus, in the patient with kyphotic synostosis, the caudal mobile segments developed compensatory hyperlordosis that resulted in spondylosis at the adjacent caudal segment and C4

4 146 MS Moon et al. Journal of Orthopaedic Surgery Figure 5 Five patients aged 18 to 35 years with C2-3 synostosis showing normal discs below C3-4. retrolisthesis at the apex of hyperlordosis (C4-5) [Fig. 1]. We therefore advise that kyphotic synostosis of any degree should be carefully followed up. It is debatable whether congenitally fused vertebrae are similar to surgically fused vertebrae. 1,15 18 This would be possible only if (1) segments adjacent to block vertebrae are truly normal to start with, and (2) side effects of surgical fusion are negligible. Both assumptions are speculative. 3 Our findings on congenital C2-3 synostosis may not be comparable to those on surgically fused C2-3. Therefore, normally aligned congenital C2-3 synostosis is only likely to develop adjacent joint disease late in life, whereas kyphotic C2-3 synostosis is likely to associate with junctional problems early in life. Limitations of this study were the small case number (because of rarity), no cases of surgically fused C2-3, no cases of monosegment synostosis of the other levels, and no cases with variably severe kyphotic fusion as controls. REFERENCES 1. Frobin W, Leivseth G, Biggemann M, Brinckmann P. Sagittal plane segmental motion of the cervical spine. A new precision measurement protocol and normal motion data of healthy adults. Clin Biomech (Bristol, Avon) 2002;17: Epstein NE, Epstein JA, Zilkha A. Traumatic myelopathy in a seventeen-year-old child with cervical spinal stenosis (without fracture or dislocation) and a C2-C3 Klippel-Feil fusion. A case report. Spine (Phila Pa 1976) 1984;9: Leivseth G, Frobin W, Brinckmann P. Congenital cervical block vertebrae are associated with caudally adjacent discs. Clin Biomech (Bristol, Avon) 2005;20: Hall JE, Simmons ED, Danylchuk K, Barnes PD. Instability of the cervical spine and neurological involvement in Klippel- Feil syndrome. A case report. J Bone Joint Surg Am 1990;72: Ross J, Myles L. Cervical spine problems in children. Curr Orthop 2006;20: Tracy MR, Dormans JP, Kusumi K. Klippel-Feil syndrome: clinical features and current understanding of etiology. Clin Orthop Relat Res 2004;424: Hensinger RN. Congenital anomalies of the cervical spine. Clin Orthop Relat Res 1991;264: Eck JC, Humphreys SC, Lim TH, Jeong ST, Kim JG, Hodges SD, et al. Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion. Spine (Phila Pa 1976) 2002;27: Ducker TB. Cervical myeloradiculopathy: Klippel-Feil deformity. J Spinal Disord 1990;3: Lee CK, Weiss AB. Isolated congenital cervical block vertebrae below the axis with neurological symptoms. Spine (Phila Pa 1976) 1981;6: Nagib MG, Maxwell RE, Chou SN. Identification and management of high-risk patients with Klippel-Feil syndrome. J Neurosurg 1984;61: Baba H, Maezawa Y, Furusawa N, Chen Q, Imura S, Tomita K. The cervical spine in the Klippel-Feil syndrome. A report of 57 cases. Int Orthop 1995;19: Ritterbusch JF, McGinty LD, Spar J, Orrison WW. Magnetic resonance imaging for stenosis and subluxation in Klippel-Feil syndrome. Spine (Phila Pa 1976) 1991;16(10 Suppl):S Samartzis DD, Herman J, Lubicky JP, Shen FH. Classification of congenitally fused cervical patterns in Klippel-Feil patients:

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