Immunohistochemical investigation of nerve fiber presence and morphology in elderly cervical spine meniscoids.

BACKGROUND CONTEXT: Innervation of anatomical structures is fundamental to their capacity to generate nociceptive impulses. Cervical spine meniscoids are hypothesized to be contributors to neck pain; however, their innervation is not comprehensively understood. PURPOSE: This study aimed to examine the presence and morphology of nerve fibers within cervical spine meniscoids and adjacent joint capsules. STUDY DESIGN: This is a cross-sectional study. PATIENT SAMPLE: The sample consists of cervical hemispines of 12 embalmed cadavers (mean [standard deviation] age 82.9 [6.5] years, six female, six left). Either the right or the left half of the cervical spine (hemispine) of each cadaver was included in the sample. So six left sides and six right sides of the cadaver cervical spines made up the 12 hemispines that formed the sample. METHODS: Cervical spine meniscoids and adjacent joint capsules were excised from lateral atlantoaxial and cervical zygapophyseal (C2-C3 to C6-C7) joints (n=67), then paraffin embedded. Meniscoids were sectioned sagittally (5 µm), slide mounted, and immunohistochemistry was performed using primary antibodies to neurofilament heavy (NF-H) and pan-neurofilament (Pan-NF) to identify nerve tissue. The study was supported by institutional graduate student funding. The authors have no conflicts of interest to declare. RESULTS: Seventy-seven meniscoids (23 lateral atlantoaxial, 54 cervical zygapophyseal) were extracted and processed (154 sections in total). Sixty-four individual nerve fiber bundles were identified (26 NF-H positive, 38 Pan-NF positive) from 14 meniscoids. Nerves immunoreactive to both NF-H and Pan-NF were identified in 13 of 77 meniscoids (10 of 14 lateral atlantoaxial joint) from 11 joints (eight cadavers). Nerves were always located in joint capsules except three exclusively Pan-NF immunoreactive nerve fiber bundles from two adipose meniscoids. CONCLUSIONS: The low nerve prevalence in elderly cervical spine meniscoids, with nerves only found in two adipose type meniscoids, suggests these structures may play a minimal role in cervical nociception generation in this demographic. The joint capsules, which were more frequently innervated, appear to be more likely generators of nociception in the elderly. Joint capsule nerves were mostly NF-H positive, indicating potential Aδ-fiber presence.

Anatomy and development of the craniovertebral junction.

The occipital bone is the upper end of the somatic spine, limited cranially by the tentorium. The bony craniovertebral junction (caudal occiput, atlas, and axis) is interposed between the unsegmented occipital and the intersegmental spinal sclerotomes, separated from the occiput and C3 by the intrasegmental clefts of O4 and C2 sclerotomes, respectively. It retains a primitive segmental hypocentrum (anterior arch of C1) and is unsegmented from caudal O4 to cranial C2 half-sclerotomes (axis). Its morphology relates to the dual function of providing support and mobility (visual/olfactory/auditory pursuit, oral prehension) to the head. The early notochord passes through the odontoid tip to the basiocciput surface before entering the clivus up to the craniopharyngeal canal; later, the rostralmost chordal remnant is the C2/3 nucleus pulposus. Chondrification starts in the second fetal month and ossification in the fetal or postnatal periods depending on the structure.

Long-term maintenance of cervical alignment after occipitocervical and atlantoaxial screw fixation in young children.

OBJECT: Despite decades of surgical experience, the long-term consequences of occipitocervical (OC) and atlantoaxial (C1-2) fusions in children are unknown. The purpose of this study was to determine the long-term effects of these fusions on growth and alignment of the maturing cervical spine. METHODS: A retrospective chart review was conducted for patients 6 years of age or younger (mean 4.7 years, range 1.7-6.8 years) who underwent OC or C1-2 fusion at the Primary Children's Medical Center at the University of Utah within the last 10 years. Immediate postoperative plain radiographs and computed tomography (CT) scans were compared with the most recent plain and dynamic radiographs to assess changes in spinal growth and alignment. Seventeen children met entry criteria for the study. All patients had fusion documented on follow-up radiography or CT scans. At a mean follow up of 28 months, there were no cases of sagittal malalignment (kyphotic or swan-neck deformity), subaxial instability (osteophyte formation or subluxation), or unintended fusion of adjacent levels. The lordotic curvature of the cervical spine increased from a mean of 15 degrees postoperatively to 27 degrees at follow up (p = 0.06). A mean of 34% of the vertical growth of the cervical spine occurred within the fusion segment. When data were analyzed pertaining to a subgroup of five patients who underwent follow-up periods for longer than 48 months (mean 50.2 months, range 48-54 months), similar results were seen. CONCLUSIONS: Preliminary follow-up results indicate that, compared with older children, children 6 years of age or younger undergoing OC or C1-2 fusion are not at an increased risk of spinal deformity or subaxial instability. Longer follow-up periods, during which measurements of the spinal canal are taken, will be necessary to determine precisely how children's spines grow and remodel after an upper cervical spine fusion.

C1-C2 posterior fusion in growing patients: long-term follow-up.

STUDY DESIGN: A retrospective review of patients undergoing C1-C2 posterior fusion during childhood was undertaken. OBJECTIVES: The aim of this study was to investigate the change in the sagittal curvature of the cervical spine in children after C1-C2 posterior fusion. SUMMARY OF BACKGROUND DATA: There have been only a few reports on postoperative changes in the sagittal curvature of the cervical spine after C1-C2 posterior fusion in children. However, they have all described the onset of sagittal postoperative cervical deformities. METHODS: Between January 1977 and December 1992, a total of 12 children underwent C1-C2 posterior fusion for atlantoaxial instability resulting from congenital malformation in eight, juvenile rheumatoid arthritis in one, and rotatory subluxation in three. The average age at the time of surgery was 10.9 years (range 7-12 years). All children underwent a similar treatment program with gradual preoperative reduction in halo cast, followed by C1-C2 posterior fusion with Mersilene loops in two cases, wiring in eight (Gallie's or Brooks' techniques), and interlaminar clamps in the remaining two. The halo cast made it possible to avoid a hyperextended or hyperflexed C1-C2 position while performing the atlantoaxial fusion, thus ensuring a more anatomic position during C1-C2 fusion. In the postoperative period, the halo cast was maintained for 7 to 9 weeks. RESULTS Follow-up ranged from 7 years to 13 years. Preoperative alignment of the cervical spine was classified into two groups: lordosis (eight patients) and straight (four patients). Postoperative subaxial malalignment (kyphosis) occurred in four cases (33%): these patients showed evidence of spontaneous and gradual sagittal improvement and presented either a straight (two cases) or a lordotic (two cases) cervical spine at follow-up. Immediately after surgery, the cervical spine was normally aligned in the remaining eight patients (lordosis and straight alignment in six and two cases, respectively) and was unchanged at follow-up. At follow-up, none of the 12 patients had a cervical deformity on sagittal plane. CONCLUSION: In children, a spontaneous realignment of the subaxial kyphosis observed after C1-C2 posterior fusion can be noted at follow-up, when a postoperative deformity occurs (33% in the present series). According to the present findings, it is not always mandatory to perform occipitocervical fusion in children with atlantoaxial instability just to prevent subaxial deformity in the cervical spine.

Craniocervical junction as a focus for craniofacial growth studies.

The craniocervical junction is a highly specialized unit simultaneously supporting head during movements in all planes and protecting the spinal cord. Anatomically, it includes an atlantoaxial complex, part of which embryonically arises from the occipital region of the skull. This review deals with the gross anatomy, kinematics, and growth reactions associated with functional alteration in this complex. Particular attention is paid to the atlas, the connecting element between the head and the vertebral column proper. From several studies it is concluded that the horizontal growth of the atlas is regulated by synchondroseal growth, whereas the vertical growth is determined by appositional growth. Some vertebral anomalies and concomitant anomalies of the cranial base are reported, to point out the ontogenetic integration between the skull base and the craniocervical junction. The high frequencies of atlantal posterior arch deficiency in cleft palate patients have led to speculations about common etiologic factors in these conditions.