Melorheostosis of the cervical and cervicothoracic spine: review of the literature and presentation of 3 new cases.

Melorheostosis is a rare dysplastic bone disease that usually affects long bones at the upper or lower limbs. It is rarely seen at the spine and very rarely located at the cervical spine. To the best of our knowledge, there are currently 6 cases of melorheostosis described at the cervical spine. Here, we give an overview of the current literature of spinal melorheostosis with respect to number of cases and skeletal distribution, aetiology, radiographic appearance, symptoms and treatment. Finally, we describe 3 new clinical cases with manifestation of melorheostosis at the cervical spine and the cervicothoracic junction.

How cervical and cervicothoracic scoliosis influence the atlantoaxial joint.

INTRODUCTION: Children with cervical or cervicothoracic congenital scoliosis are limited in their ability to compensate for the main curve of the deformity because there are only a few mobile segments in their cervical spine. Over the years, we have frequently observed coronal atlantoaxial dislocation (CAAD) in a lateral direction (from left to right or vice versa) in these patients. It was anticipated that CAAD might compensate for the horizontal position of the head, and it is hypothesized that CAAD depends on the degree of scoliotic deformity. Thus, the aim of our study was to investigate whether there is a correlation between CAAD and scoliosis parameters in these patients. METHODS: Retrospective analysis was performed based on CAT scans and preoperative X-rays of patients with cervical and cervicothoracic scoliosis with an apex between C4 and T6. Seventeen patients, with a mean age of 7.25 years, who were 9 girls and 8 boys, and who were treated between 2006 and 2022 were included. Cobb`s angle of the main curve (CA-MC), Cobb`s angle of the secondary curve (CA-SC), and T1-, C2- and UEV (upper end vertebra) tilt were measured on whole-spine radiographs in the standing position. The CAAD was measured via coronal CAT scan reconstruction and defined as the difference in the distances of the lateral masses to the midline of the axis. Pearson`s linear correlation coefficients (r) were determined using SPSS to evaluate correlations between CAAD and the measured parameters. p < 0.05 indicated statistical significance. RESULTS: CAAD toward the convex region in patients with scoliosis was typically observed; the mean CAAD was 3 mm ± 3.7 mm. The mean CA-MC was 46° ± 13°, the mean CA-SC was 16° ± 9.6°, the mean T1 tilt was 17° ± 8.8°, the mean C2 tilt was 9°± 8.8°, and the mean UEV tilt was 24° ± 7.2°. There was a strong linear correlation between CAAD and CA-MC (r = 0.784, p < 0.001), C2 tilt (r = 0.745; p < 0.001), and UEV tilt (r = 0.519; p = 0.033). There was no correlation between CAAD and either CA-SC or T1 tilt. DISCUSSION: Children with cervical or cervicothoracic scoliosis tend to have a CAAD toward the convexity of the scoliosis that correlates to CA-MC, C2-tilt, and UEV-tilt. CAAD may be seen as a compensatory mechanism to keep the head in a horizontal position. Severe or progressive CAAD may result in destruction of the atlantoaxial joint, including severe complaints, thus necessitating close follow-up and possibly early surgical treatment. Moreover, CAAD might be a useful additional radiographic parameter to be checked in future scoliosis studies.

The effect of posterior compression of the facet joints for initial stability and sagittal profile in the treatment of thoracolumbar fractures: a biomechanical study.

PURPOSE: Surgical treatment of thoracolumbar A3-fractures usually comprises posterior fixation-in neutral position or distraction-potentially followed by subsequent anterior support. We hypothesized that additional posterior compression in circumferential stabilization may increase stability by locking the facets, and better restore the sagittal profile. METHODS: Burst fractures Type A3 were created in six fresh frozen cadaver spine segments (T12-L2). Testing was performed in a custom-made spinal loading simulator. Loads were applied as pure bending moments of ± 3.75 Nm in all six movement axes. We checked range of motion, neutral zone and Cobb's angle over the injured/treated segment within the following conditions: Intact, fractured, instrumented in neutral alignment, instrumented in distraction, with cage left in posterior distraction, with cage with posterior compression. RESULTS: We found that both types of instrumentation with cage stabilized the segment compared to the fractured state in all motion planes. For flexion/extension and lateral bending, flexibility was decreased even compared to the intact state, however, not in axial rotation, being the most critical movement axis. Additional posterior compression in the presence of a cage significantly decreased flexibility in axial rotation, thus achieving stability comparable to the intact state even in this movement axis. In addition, posterior compression with cage significantly increased lordosis compared to the distracted state. CONCLUSION: Among different surgical modifications tested, circumferential fixation with final posterior compression as the last step resulted in superior stability and improved sagittal alignment. Thus, posterior compression as the last step is recommended in these pathologies.

Iatrogenic Intracranial Hypotension after Surgery of Adolescent Idiopathic Scoliosis due to a Misplaced Screw within the Thoracic Thecal Sac.

We present the case of a postoperative intracranial hypotension due to a misplaced intrathecal screw. Although typical symptoms such as orthostatic headache were present immediately after surgery, diagnosis was hidden until 20 years later, resulting in a disastrous clinical course.

The Feasibility of C1-C2 Screw-rod Fixation in the Children 5 Years of Age and Younger.

BACKGROUND: Atlantoaxial fixation is technically challenging in younger children. The C1-C2 screw-rod fixation technique is established for adults but limited data about the clinical and radiographical outcome for the treatment of children with 5 years of age or younger is available. METHODS: All files of children who were consecutively treated for spinal disorders were reviewed. Inclusion criteria for further evaluation were: 0 to 5 years of age at initial procedure; detailed surgical report of a posterior C1-C2 fusion with mass lateral and pedicle screw-rod fixation as described by Harms; a minimum clinical and radiographical follow-up of 24 months. The postoperative and last follow-up computed tomography scan and radiographs were used to assess the positioning and stability of the C1-C2 screw-rod construct. RESULTS: Eleven patients (3 boys) with a mean age of 46 months (range: 8 to 66 mo) fulfilled inclusion criteria and were evaluated retrospectively. The mean clinical and radiographical follow-up was 79 months (range: 24 mo to 170 mo). The diagnosis was atlantoaxial rotatory dislocation (4 cases), C1-C2 instability with subluxation (3 cases), atlantoaxial dislocation and os odontoideum (1 case), type II odontoid fracture (1 case), traumatic odontoid epiphysiolysis (1 case), and traumatic rupture of the transverse ligament with C1 subluxation (1 case). Intraoperatively and postoperatively no new neurovascular or vascular complication occurred. C1 lateral mass screws were placed correctly in all cases. Twenty-two C2 pedicle screws were placed correctly (85.7%), and 3 screws showed penetration of the pedicle wall (14.3%). No implant revision, implant failure, and pseudarthrosis were noted. Loss of correction was noted in 1 patient with unilateral C1-C2 fixation and a repeated dorsal fusion procedures were performed. A repeat procedure for implant removal and segmental release was performed in 3 patients to increase the axial rotation of the head. CONCLUSIONS: The C1-C2 screw-rod fixation is a safe technique that achieves solid fixation of the atlantoaxial complex in young children with various disorders. The technique preserves the joint and allows for segmental release via implant removal.

Atlantoaxial Rotatory Dislocation: Delayed Diagnose Will Result in More Invasive Treatment Options.

PURPOSE: The atlantoaxial joint represents the most mobile joint complex within the spine, secured by ligaments and capsules. Integrity of the atlantoaxial joint is crucial with respect to the mobility of the head and the upper spine. Atlantoaxial rotatory dislocation is the most common type of injury within this joint in children and is characterized by a typical position of the head (cock robin position). Nevertheless, this type of injury is frequently overlooked. The purpose of the current study was threefold. First, the characteristics of the patients with atlantoaxial dislocation were identified. Next, we checked if the time to treatment did influence the type of treatment. Finally, we checked if the age of the child at the time of treatment influenced the type of treatment. METHODS: Forty-four children, who were treated consecutively due to atlantoaxial dislocation at a single spine center between September 1993 and October 2018, are analyzed retrospectively regarding age, sex, symptoms, etiology, time to diagnosis, time to treatment, and outcome. RESULTS: Forty-four children (30 girls, mean age 8.9 years) were included in the study. The cock robin head position was found in all of them, but neurological deficits were not found in any of them. In 21 patients, dislocation was caused by previous infection (Grisel's syndrome), whereas in 19 patients, dislocation was due to minor trauma. In 4 cases, etiology remained unknown. Mean time to sufficient treatment was 178 days. Eighteen patients received closed reduction and immobilization after 57 days at mean. Open reduction followed by temporary fixation was done in 12 patients after a mean time gap of 188 days. Bony atlantoaxial fusion was necessary in 14 children, who were diagnosed after 319 days on average. Invasiveness of treatment was dependent on the time delay between development of dislocation and treatment; a significant difference was found between invasiveness of treatment and time to treatment (Kruskal-Wallis test, p < 0,05). Moreover, older children were treated significantly more often with fusion than younger ones (χ 2, p = 0,002). CONCLUSION: Young girls are predisposed to incur an atlantoaxial rotatory dislocation, which usually occurs due to minor trauma or infection. The cock robin position is characteristic, but neurological deficits are not common. There is a need for early and sufficient treatment because delayed treatment necessitates more invasive treatment, thus leading to a complete loss of function of the most mobile joint within the spine. Finally, older children are predisposed to more invasive treatment strategies.

[Biomechanical compensatory mechanisms of hips and spine : The essentials for spine and hip surgeons]. / Biomechanische Kompensationsmechanismen der Hüftgelenke und der Wirbelsäule : Das Wesentliche für Wirbelsäulen- und Hüftchirurgen.

Spinal alignment changes with age and degeneration. Different compensatory mechanisms of the spine are necessary to preserve spinal balance. The capacity of compensation of the spine decreases with age. Thus, the pelvis and the lower limbs become involved in the compensatory mechanism. Concomitant osteoarthritis of the hip could impair this capacity. The biomechanical principles of compensation are described with respect to planning reconstructive hip and spine surgery.

[Diagnostics and treatment of cervical spine trauma in pediatric patients : Recommendations from the Pediatric Spinal Trauma Group]. / Diagnostik und Therapie von Verletzungen der Halswirbelsäule im Kindesalter : Empfehlungen der AG Wirbelsäulentrauma im Kindesalter.

BACKGROUND: Severe cervical spine injuries in children under the age of 17 years are rare. Recommendations or even guidelines for the diagnostics and treatment of such injuries in children are currently not available. OBJECTIVE: The aim of the study was to formulate recommendations for diagnostics and treatment of injuries of the cervical spine in pediatric patients. MATERIAL AND METHODS: First, a search of primary and secondary literature on the topic complex of diagnostics and treatment of cervical spine injuries in children was carried out. An appropriate internal literature database was defined and maintained. Second, within the framework of 9 meetings from April 2017 to December 2019 the members of the Pediatric Spinal Trauma Group of the Spine Section of the German Society for Orthopaedics and Trauma (DGOU) systematically formulated recommendations for the diagnostics and treatment of injuries of the cervical spine in pediatric patients by a consensus process. RESULTS: Recommendation for the diagnostics and treatment for injuries of the cervical spine could be formulated for three age groups (age group I: 0-6 years; age group II: 7-9 years; age group III: 10-16 years). The diagnostic and therapeutic principles known from adult patients suffering from injuries to the cervical spine cannot be easily transferred to pediatric patients. CONCLUSION: Injuries to the pediatric spine are rare and should be treated in specialized spine centers. Pediatric patients with a stable cardiopulmonary status should undergo magnetic resonance imaging (MRI) if a spinal trauma is suspected. Classification systems and therapeutic recommendations for injuries to the cervical spine known from adult patients could also be used for adolescent patients. This is not possible for children under the age of 10 years. Only few classification systems exist for this age group. Basic principles of the treatment of spinal trauma in children is the restoration of spinal stability and correct anatomical relationships as well as the protection of all neural structures.

The Effect of Cervicodorsal Hemivertebra Resection on Head Tilt and Trunk Shift in Children With Congenital Scoliosis.

BACKGROUND: Congenital scoliosis due to hemivertebra of the cervicodorsal spine is a rare disorder. It might be accompanied by impaired cosmetic appearances such as head tilt and trunk shift. Little is known about the effect of correction of the major curve on head tilt and trunk shift in children. The purpose of this study was to assess radiographic changes of head tilt and trunk shift following posterior hemivertebra resection (PHVR). METHODS: Retrospectively, all children who underwent PHVR at the cervicodorsal spine (C6-Th6) with pedicle screw fixation with a minimum radiographic follow-up of 1 year were identified for further assessment. A total of 5 radiographic parameters were assessed on preoperative, postoperative, and final follow-up radiographs. (1) Head tilt was defined as the angle between the horizontal line and the line through both molars of the maxillary, (2) trunk shift as the angle between the line of the center of C7 to the sacrum and the central sacral vertical line, (3) Cobb angle was used to assess the major curve, (4) cranial, and (5) caudal compensatory curvature. RESULTS: Seven boys and 10 girls with a mean age of 9.0 years at surgery were evaluated. The mean radiographic follow-up was 89.5 months (range: 12 to 166 mo). The mean head tilt reoriented from 6.9 to 1.9 degrees (P<0.001); trunk shift improved from 4.3 to 2.5 degrees after surgery (P=0.100). There was a significant correlation between head tilt and trunk shift on preoperative and postoperative radiographs (P=0.030/0.031). The major curve, and compensatory curvatures were all significantly corrected (P<0.001). Head reorientation was significantly influenced by patient age at surgery. Repeated procedures due to decompensation of the compensatory curvature were performed in 2 cases. CONCLUSIONS: PHVR and pedicle screw fixation is an effective treatment for patients with congenital scoliosis. Surgery achieves a significant correction of the major curve and reorientation of the head postoperatively, and till the last follow-up. LEVEL OF EVIDENCE: Level IV.

Degenerative Cervical Myelopathy: A 7-Letter Coding System That Supports Decision-Making for the Surgical Approach.

OBJECTIVE: To validate with a prospective study a decision-supporting coding system for the surgical approach for multilevel degenerative cervical myelopathy. METHODS: Ten cases were presented on an internet platform, including clinical and imaging data. A single-approach (G1), a choice between 2 (G2), or 3 approaches (G3) were options. Senior and junior spine surgeons analyzed 7 parameters: location and extension of the compression of the spinal cord, C-spine alignment and instability, general morbidity and bone diseases, and K-line and multilevel corpectomy. For each parameter, an anterior, posterior, or combined approach was suggested. The most frequent letter or the last letter (if C) of the resulting 7-letter code (7LC) suggested the surgical approach. Each surgeon performed 2 reads per case within 8 weeks. RESULTS: G1: Interrater reliability between junior surgeons improved from the first read (κ = 0.40) to the second (κ = 0.76, p < 0.001) but did not change between senior surgeons (κ = 0.85). The intrarater reliability was similar for junior (κ = 0.78) and senior (κ = 0.71) surgeons. G2: Junior/senior surgeons agreed completely (58%/62%), partially (24%/23%), or did not agree (18%/15%) with the 7LC choice. G3: junior/senior surgeons agreed completely (50%/50%) or partially (50%/50%) with the 7LC choice. CONCLUSION: The 7LC showed good overall reliability. Junior surgeons went through a learning curve and converged to senior surgeons in the second read. The 7LC helps less experienced surgeons to analyze, in a structured manner, the relevant clinical and imaging parameters influencing the choice of the surgical approach, rather than simply pointing out the only correct one.

Changes in Swallowing After Anterior Cervical Discectomy and Fusion With Instrumentation: A Presurgical Versus Postsurgical Videofluoroscopic Comparison.

Purpose: The purpose of this study was to explore the impact of anterior cervical discectomy and fusion (ACDF) with anterior instrumentation on swallowing function and physiology as measured on videofluoroscopic swallowing studies. Method: We retrospectively analyzed both functional measures (penetration-aspiration, residue) and physiological/anatomical measures (hyoid excursion, posterior pharyngeal wall thickness) in a series of 17 patients (8 men, 9 women, mean age 54 years). These measures were extracted from calibrated 5-ml boluses of thin radio-opaque liquids on both pre-ACDF and post-ACDF videofluoroscopies, thus controlling for individual variation and protocol variation. Results: After ACDF surgery, we found significant within-subject worsening of Penetration-Aspiration Scale (Rosenbek, Robbins, Roecker, Coyle, & Wood, 1996) scores, vallecular (but not piriform sinus) residue, superior (but not anterior) hyoid excursion, and posterior pharyngeal wall thickness. Results are discussed in the context of previous literature. Conclusions: ACDF surgery can affect both physiological/anatomical and functional measures of swallowing. Future research should expand to other biomechanical and temporal variables, as well as greater bolus volumes and a wider array of viscosities and textures.

C1-C2 Instrumentation According to Harms/Goel in Case of Vertebral Artery below the Arch of C1: A Case Report.

Study Design Case report. Background and Study Aims For stabilizing surgery of the atlantoaxial region, a precise evaluation of the course of the vertebral artery (VA) is essential to avoid vessel injury and life threatening complications. In patients with aberrant VA course, an appropriate way for fusion needs to be found. This article presents a case of an unusual VA course and illuminates the importance of surgical planning with computed tomography angiography identifying VA variations at the atlantoaxial region. Case Report A 71-year-old woman with atlantoaxial arthrosis had a VA variation (persistent first intersegmental artery). She underwent C1-C2 posterior fixation according to Harms/Goel using the typical entry points, requiring VA dissection in caudal direction. The postoperative clinical as well as radiographic result was excellent. Angiography 6 months postoperatively showed the VAs below the C1 screws with normal blood flow. Conclusions Placement of C1 screws in a patient with a persistent first intersegmental VA is possible. Careful VA dissection is the key step for safe screw placement, screw anchoring, and clinical success.

Resection of a Hemivertebra Within the Craniocervical Junction.

STUDY DESIGN: Case report on resection of a hemivertebra at the craniocervical junction. OBJECTIVE: To describe technique and result of a hemivertebra resection within the craniocervical junction (axis). SUMMARY OF BACKGROUND DATA: To our knowledge, this is the first report on a transoral and posterior hemivertebra resection at C2. METHODS: A 42-year-old patient presented with coronal imbalance due to a hemivertebra at C2. Correction was performed by a combined anterior (transoral) and posterior approach with hemivertebra resection and compression instrumentation. RESULTS: The postoperative course was uneventful. The radiographs showed a complete correction of the deformity with a perfect clinical result. CONCLUSION: Hemivertebra resection at the craniocervical junction can be performed safely with good clinical and radiographical outcome. LEVEL OF EVIDENCE: 4.

Left-right axial rotation within C1-2 after implant removal.

OBJECT: Surgical treatment of atlantoaxial injuries may be performed by a variety of surgical procedures, with each of these having its own specific advantages and disadvantages. To preserve the range of motion within the atlantoaxial joint after surgical treatment, posterior atlantoaxial screw fixation according to the method of Goel and Harms could be beneficial. This technique is not considered to fix the joint permanently if the screws are removed. However, this must not necessarily be true, especially if one notices that cervical joints have a tendency for rapid fusion after surgery. The objective of this study was to analyze left-right axial rotation following implant removal, with the following research questions addressed: 1) is there a relevant rotational left-right mobility in C1-2; 2) is there a difference in mobility depending on sex; 3) is there a correlation of mobility to age; 4) is there a correlation of mobility to the "implant-in-body time"; and 5) is neck pain improved by this method of surgical treatment? METHODS: This is a retrospective study in 10 patients who had received atlantoaxial fixation according to the Harms method following atlantoaxial injury. These patients had undergone implant removal after a mean time of 128 days, followed by functional atlantoaxial CT in left-right rotation. Statistical analysis was performed using the SPSS software package; significance was assumed for p < 0.05. RESULTS: The following findings are reported. 1) Left-right axial rotation within the atlantoaxial joint was measured to be 17° (mean value) following implant removal. 2) There was no significant difference between men (20°) and women (14.8°) (p = 0.595). 3) Left-right axial rotation negatively correlated to the age of the patient (r = -0.646, p = 0.043). 4) "Implant-in-body time" did not influence left-right axial rotation (r = 0.04, p = 0.907) if the implants are removed within 90-180 days after surgery. 5) Neck pain as assessed by the patients themselves on the visual analog scale was 7.9 ± 1.1 preoperatively and 3.6 ± 1.2 (mean ± SD) after implant removal (p = 0.002). CONCLUSIONS: The authors conclude that removal of the implants 3-6 months after posterior atlantoaxial fixation according to the method of Goel and Harms is beneficial for obtaining some axial rotation within the atlantoaxial joint. The range of motion preserved depends on the age of the patient.

Local autograft retrieval from a cervical vertebral body: biomechanical consequences.

OBJECT: To avoid the cost of bone graft substitutes and the morbidity of iliac crest bone graft retrieval, locally harvested vertebral body bone has been used to fill interbody cages. When marginal hypertrophic osteophytes are used, there is little impact on the adjacent vertebrae, but when cancellous bone is removed from the central part of the vertebral body, it is not clear how significantly this procedure weakens the vertebra. The objective of this study was to investigate the immediate mechanical response of the cervical spine after removing bone from the central vertebral body. METHODS: Fourteen cervical functional spinal units (FSUs) (mean age 73.3 years, range 63-90 years) were used. For each FSU, bone mineral density (BMD) was determined using lateral-view dual-energy x-ray absorptiometry studies. The FSUs were assigned to 1 of 2 groups (test group or control group) with an equal distribution of BMD. All specimens received a cage placed into the cleaned disc space. The specimens from the test group had a 5-mm-diameter bone plug removed from the vertebral bodies superior and inferior to the cage-fitted disc. The specimens were loaded in flexion-compression until failure via an eccentric compressive force at 0.25 mm/second. RESULTS: The yield compression strength was 1149 ± 523 N for the test group and 1647 ± 962 N for the control group (p = 0.25). The ultimate compression strength was 1699 ± 498 N for the test group and 2450 N ± 835 N for the control group (p = 0.06). Force at 4 mm displacement was 1064 N for the test group and 1574 N for the control group (p = 0.15). Displacement at yield compression strength was 4.4 mm for the test group and 4.2 mm for the control group (p = 0.78). There was no significant intergroup difference for any of the studied parameters. CONCLUSIONS: There does not appear to be a significant early biomechanical weakening of adjacent vertebrae caused by aforementioned technique of local bone harvest.

Comparison of bioresorbable and titanium plates in cervical spinal fusion: early radiologic and clinical results.

STUDY DESIGN: This is a prospective, randomized, and controlled study, approved by the local ethical committee of Saarland (Germany), no. 209/06. OBJECTIVE: The aim of this study was to compare clinical results, segmental motility, magnetic resonance imaging (MRI) compatibility, and change of the bone density of a cervical spine segment that was treated with either bioresorbable or titanium plates in single level. SUMMARY AND BACKGROUND DATA: Anterior cervical discectomy and fusion including plate fixation is an accepted technique for treatment of symptomatic degenerative disc disease. Titanium plates have been used but cause imaging artifacts. Radiolucent bioresorbable plates and screws were developed to reduce the imaging artifacts associated with titanium. METHODS: Forty patients with single level cervical radiculopathy were randomized to anterior discectomy and fusion with bioresorbable plate (19 patients, study group) or titanium plate (18 patients, control group). Follow-up used a visual analog scale (VAS) with regard to brachial pain and Neck Disability Index (NDI) for neck pain. Radiostereometry was performed immediately postoperative and after 6 weeks, 3, and 6 months. MRI of the cervical spine was obtained immediately postoperatively at 3 and 6 months to assess hematoma, infection, and swelling. Computed tomography of the operated cervical spine segment was performed to assess bone density, expressed in Hounsfield units. RESULTS: Three-dimensional analysis of segmental motion (medio-lateral, cranio-caudal and anterior-posterior) did not reveal any statistical difference between both groups at any time postoperatively (P>0.05). Fusion rate and speed evaluated on Radiostereometric analysis and computed tomography of cervical spine segment were similar in both groups. MRI of cervical spine did not show any pathology, especially hematoma and infection. The VAS and NDI did not differ between both groups after 6 months (P>0.05). CONCLUSIONS: Anterior plate fixation by using a bioresorbable plate has the same fusion progress and stability as titanium. During the study, no complications like soft tissue swelling and infection occurred.

Implant complications, fusion, loss of lordosis, and outcome after anterior cervical plating with dynamic or rigid plates: two-year results of a multi-centric, randomized, controlled study.

STUDY DESIGN: Prospective, controlled, randomized, multicenter study. OBJECTIVE: To analyze implant complications and speed. SUMMARY OF BACKGROUND DATA: Rigid plate designs, in which the screws are locked to the plate, are in common use and thought to provide more fixation than dynamic designs, in which the screws may glide when the graft is settling. The aim of the study is to analyze (1) implant complications, (2) speed of fusion, (3) loss of lordosis, and (4) clinical outcome in both types of plates. METHODS: One hundred thirty-two patients were included and assigned by randomization to one of the groups in which they received a routine anterior cervical discectomy and autograft fusion with either a dynamic plate (ABC, study group) or a rigid plate (CSLP, control group). At discharge, after 3 and 6 months and finally after 2 years, implant complications, segmental mobility, absence of radiolucencies, absence of bone sclerosis, evidence of bridging trabecular bone, loss of lordosis, Visual Analog Scale (VAS) and Neck Disability Score were recorded. All radiographic measurements were performed by an independent radiologist. RESULTS: There have been 4 patients with implant complications within the control group and no implant complications within the study group, P = 0.045. Mean segmental mobility before discharge for the study group was 1.7 mm, 1.4 mm after 3 months, 0.8 mm after 6 months, and 0.4 mm after 2 years. For the control group, these values were 1.0, 1.8, 1.6, and 0.5 mm. The difference at 6 months between both groups was significant (P = 0.024). Neither absence of radiolucencies, nor absence of sclerosis, nor evidence of bridging bone showed significant differences between the 2 groups through the postoperative follow-up (P > 0.05). The loss of segmental lordosis for the study group with respect to intraoperative radiograph was 1.3 degrees at discharge and 4.3 degrees after 2 years. For the control group, these values were 0.9 degrees , 0.7 degrees . The difference at 2 years was significant (P = 0.003). Clinical postoperative outcome (VAS and ODI) was not different between the 2 groups through the postoperative follow-up (P > 0.05). CONCLUSION: Dynamic cervical plate designs provide less implant complications (no patient) compared with rigid plate designs (4 patients). Speed of fusion was faster in the presence of a dynamic plate. However, loss of segmental lordosis is significantly higher if dynamic plates are used, which did not result in differences regarding clinical outcome between dynamic and constrained plates after 2 years. Thus, dynamic plates should be considered to be the preferred treatment option because of the lower risk for implant failure-related revision surgery.

Fusion and failure following anterior cervical plating with dynamic or rigid plates: 6-months results of a multi-centric, prospective, randomized, controlled study.

Anterior cervical plate fixation is an approved surgical technique for cervical spine stabilization in the presence of anterior cervical instability. Rigid plate design with screws rigidly locked to the plate is widely used and is thought to provide a better fixation for the treated spinal segment than a dynamic design in which the screws may slide when the graft is settling. Recent biomechanical studies showed that dynamic anterior plates provide a better graft loading possibly leading to accelerated spinal fusion with a lower incidence of implant complications. This, however, was investigated in vitro and does not necessarily mean to be the case in vivo, as well. Thus, the two major aspects of this study were to compare the speed of bone fusion and the rate of implant complications using either rigid- or dynamic plates. The study design is prospective, randomized, controlled, and multi-centric, having been approved by respective ethic committees of all participating sites. One hundred and thirty-two patients were included in this study and randomly assigned to one of the two groups, both undergoing routine level-1- or level-2 anterior cervical discectomy with autograft fusion receiving either a dynamic plate with screws being locked in ap - position (ABC, Aesculap, Germany), or a rigid plate (CSLP, Synthes, Switzerland). Segmental mobility and implant complications were compared after 3- and 6 months, respectively. All measurements were performed by an independent radiologist. Mobility results after 6 months were available for 77 patients (43 ABC/34 CSLP). Mean segmental mobility for the ABC group was 1.7 mm at the time of discharge, 1.4 mm after 3 months, and 0.8 mm after 6 months. For the CSLP- group the measurements were 1.0, 1.8, and 1.7 mm, respectively. The differences of mean segmental mobility were statistically significant between both groups after 6 months (P = 0.02). Four patients of the CSLP-group demonstrated surgical hardware complications, whereas no implant complications were observed within the ABC-group (P = 0.0375). Dynamic plate designs provided a faster fusion of the cervical spine compared with rigid plate designs after prior spinal surgery. Moreover, the rate of implant complications was lower within the group of patients receiving a dynamic plate. These interim results refer to a follow-up period of 6 months after prior spinal surgery. Further investigations will be performed 2 years postoperatively.