Modified technique for C1-2 screw-rod fixation and fusion using autogenous bicortical iliac crest graft

Surgical Failure and Revision Strategy for Atlantoaxial Dislocation: A Retrospective Study of 109 Cases

STUDY DESIGN

Retrospective study.

OBJECTIVE

To classify surgical failures following atlantoaxial dislocation, present strategies for revisions, and evaluate the clinical results of revision surgery.

SUMMARY OF BACKGROUND DATA

With the increase in atlantoaxial dislocation surgery, the number of surgical failures has gradually risen. However, current reports on atlantoaxial surgical revision are limited in scope. There remains a lack of summary regarding the causes of surgical failure, a detailed classification system, and no proposed strategy for revision surgery.

MATERIALS AND METHODS

A total of 109 cases of failed surgery following atlantoaxial dislocation were classified according to the reduction immediately after surgery and the fusion status before revision. The reduction, decompression, fusion status, and outcomes following revision surgery were evaluated by x-ray, computed tomography, magnetic resonance imaging, and the Japanese Orthopaedic Association score. The data were analyzed statistically with a paired-samples t test and multivariable logistic regression analysis.

RESULTS

The 109 patients were classified into three categories of failure: nonreduction with nonfusion (NR-NF, 73 cases), nonreduction with fusion (NR-F, 19 cases), and reduction with nonfusion (R-NF, 17 cases). Sixty-four patients underwent anterior revision, 21 posterior revision, and 24 anteroposterior revision. Postoperative complications were the primary cause of early revisions. After revision, complete decompression was achieved in all cases, anatomical reduction in 89 cases, significant improvement of Japanese Orthopaedic Association score in 77 cases, and fusion achieved in 86 cases. Twelve cases experienced surgical complications and three underwent a second revision.

CONCLUSIONS

The authors found that NR-NF was the most common type of failure following surgery for atlantoaxial dislocation. Revision strategies can be guided according to the descriptive classification of failure, and revision surgery should focus on achieving adequate reduction, appropriate fixation, and reliable fusion to optimize postsurgical outcomes.

Influence of the type of atlantoaxial dislocation secondary to os odontoideum on sagittal alignment and balance of the subaxial cervical spine after posterior atlantoaxial fusion

OBJECTIVE

This retrospective study aims to investigate the effect of the type of atlantoaxial dislocation due to os odontoideum on the sagittal alignment and balance of the cervical spine after posterior atlantoaxial fusion.

METHODS

Data of 48 consecutive patients who underwent posterior C1-C2 fusion to treat atlantoaxial dislocation/instability due to os odontoideum were retrospectively reviewed. Radiographic variables, namely the T1 slope (T1S), C1-C2 angle, C2-C7 angle, C1-C2 sagittal vertical axis (SVA), C2-C7 SVA, and modified atlas-dens interval (MADI), were measured preoperatively, immediate postoperatively, and at final follow-up. Patients were divided into three groups based on the preoperative MADI. Differences within and between groups in radiographic variables and relationships between the investigated variables were analyzed.

RESULTS

The MADI was correlated with the preoperative to postoperative changes in the C1-C2 angle (r = 0.776, P < 0.05) and C2-C7 angle (r = - 0.357, P < 0.05). In the group with anterior atlantoaxial dislocation, the C1-C2 angle and C2-C7 SVA were significantly enlarged at final follow-up (P < 0.05), while the C2-C7 angle was significantly reduced (P < 0.05). The changes in C1-C2 angle and C2-C7 angle were opposite between the posterior group and the anterior dislocation group.

CONCLUSION

The direction/type of atlantoaxial subluxation correlates with the changes in lower cervical curvature after atlantoaxial fusion. Patients with atlantoaxial posterior dislocation and atlantoaxial instability are less likely than those with atlantoaxial anterior dislocation to develop loss of lordosis after posterior atlantoaxial fusion.

Comparison of Atlantoaxial Intra-Articular Fusion and Posterior Structural Bone Grafting Techniques for Treating Atlantoaxial Dislocation

BACKGROUND

The structural bone grafting (SBG) technique provided high fusion rate and satisfied outcomes for treating atlantoaxial dislocation, but it is unclear whether the atlantoaxial intra-articular cage (AIC) technique can provide clinical results comparable with SBG technique.

OBJECTIVE

To compare the outcomes of 2 bone graft techniques applied in posterior C1-C2 screw-rod fixation and fusion surgery for treating atlantoaxial dislocation.

METHODS

The data from 55 patients with atlantoaxial dislocation were retrospectively reviewed. The SBG technique had been used in 29 patients and the AIC technique in 26 patients. The outcomes were evaluated using the Japanese Orthopedic Association scale score, Neck Disability Index, and visual analog scale score for neck pain and compared between the 2 groups. The donor site complications were also recorded in SBG group, and donor site pain was assessed using a visual analog scale.

RESULTS

In the final follow-up, the bone fusion rate was 100% in both groups. No significant differences were found in the bone fusion time between the 2 groups ( P > .05). Postoperatively, the Japanese Orthopedic Association, Neck Disability Index, and visual analog scale score for neck pain indexes improved significantly within both SBG (all P < .05) and AIC groups (all P < .05). Nevertheless, there were no statistically significant differences between the 2 groups (all P > .05).

CONCLUSION

The SBG and AIC techniques were both effective for achieving atlantoaxial arthrodesis, and the AIC technique is a perfect alternative to the SBG technique when the posterior arch of C1 is incompetent.

Open Reduction for Potentially Reducible Atlantoaxial Dislocation Secondary to Transverse Ligament Laxity in Patients with Rheumatoid Arthritis

OBJECTIVE

Atlantoaxial dislocation (AAD) is classified into reducible AAD and irreducible AAD (IRAAD). Anterior or posterior releasing followed by occipitocervical/atlantoaxial fusion is often performed for IRAAD, but is technically demanding. This study aimed to evaluate the results of the posterior open reduction technique without releasing the atlantoaxial joint in the treatment of potentially reducible AAD (PRAAD) caused by transverse ligament laxity in patients with rheumatoid arthritis (RA).

METHODS

Data from 38 RA patients who experienced PRAAD due to transverse ligament laxity were retrospectively reviewed. They all underwent posterior open reduction and fusion without releasing the atlantoaxial joint. Outcomes were evaluated by using atlantodental interval, modified Japanese Orthopedic Association scores, Nurick grade, Neck Disability Index, and visual analog scale score for neck pain.

RESULTS

All the patients achieved solid bone fusion at follow-up. The mean atlantodental interval was reduced to 5.6 ± 0.7 mm and 2.1 ± 0.5 mm after traction and operation, respectively, from a preoperative score of 8.2 ± 0.6 mm (P < 0.05). Compared with the respective preoperative values, the mean modified Japanese Orthopedic Association score and Nurick grade were significantly increased at the final follow-up (both P < 0.05), whereas the Neck Disability Index and visual analog scale score for neck pain were significantly decreased (both P < 0.05).

CONCLUSIONS

AAD with partial reduction after skeletal traction for 48 hours should be defined as PRAAD, not IRAAD. Open reduction with a C1-C2 pedicle screw-rod system can be safely and effectively applied in the treatment of PRAAD due to transverse ligament laxity in patients with RA.

Biomechanical Effects of Lateral Inclination C1 and C2 Pedicle Screws on Atlantoaxial Fixation

Objective

To assess the biomechanical effect of lateral inclination C₁ and C₂ pedicle screws on the atlantoaxial fixation through vitro human cadaveric study.

Methods

From January 2016 to December 2017, fresh‐frozen cadaveric cervical spines with intact ligaments from eight donated cadavers at an average age of 71.5 ± 10.6 years, comprising of six males and two females, were collected. There were no fracture and congenital malformation in all specimens according to the imaging examination. The range of motion (ROM) of the specimens were tested in their intact condition and destabilized condition. Next, the specimens were randomly divided into two groups to ensure no differences in sex and age: Group 1 was medial inclination C₁ pedicle screw and C₂ pedicle screws (C₁MPS‐C₂PS) and Group 2 was lateral inclination C₁ pedicle screw and C₂ pedicle screws (C₁LPS‐C₂PS). The ROM of the fixation scenarios were recorded. Thereafter, all the specimens with fixation constructs were tested for 1,000 cycles of axial rotation and tensile loading to failure was carried out collinearly to the longitudinal axis of all the screws, the data were documented as screw pullout strength (SPS) in newtons. All the recorded data subjected to quantitative analysis.

Results

The ROM of specimens was increased significantly in destabilized condition and significantly reduced in fixation condition compared with intact condition. In C₁LPS‐C₂PS groups, the C₁‐C₂ cervical segment showed 3.96° ±1.21° and 3.75° ± 1.33° in flexion and extension direction, 2.85° ± 0.91° and 2.96° ± 0.71° in right and left lateral bending, 2.20° ± 0.43° and 2.15° ± 0.40° in right and left axial rotation. In C₁MPS‐C₂PS groups, it showed 4.24° ±1.31° and 3.98° ± 1.21° in flexion and extension direction, 2.76° ± 1.10° and 3.23° ± 0.62° in right and left lateral bending, 2.20° ± 0.46° and 2.21° ± 0.42° in right and left axial rotation. There was no statistically significant difference on ROM and screw pullout strengths (764.29 ± 129.00 N vs 714.55 ± 164.63 N) between the two groups. However, there was one specimen in the C₁MPS‐C₂PS group showing rupture the inferior wall of the left screw trajectory owing to the relatively thin posterior arch of the atlas, the screw pullout strength was significantly reduced (left pullout strength value: 430.5 N, right pullout strength value: 748.4 N). Therefore, in the case of the thin posterior arch of the atlas, the C₁LPS‐C₂PS group had strong long‐term biomechanics.

Conclusion

The lateral inclination C₁ pedicle screw can achieve the same biomechanical strength as the traditional atlas pedicle screw. However, for the case where the posterior arch of the atlas is relatively thin, a lateral inclination C₁ pedicle screw is more suitable.

Supplementation of Screw-Rod C1-C2 Fixation With Posterior Arch Femoral Head Allograft Strut

BACKGROUND

Numerous C1-C2 fixation techniques exist for the treatment of atlantoaxial instability. Limitations of screw-rod and sublaminar wiring techniques include C2 nerve root sacrifice and dural injury, respectively. We present a novel technique that utilizes a femoral head allograft cut with a keyhole that rests posteriorly on the arches of C1 and C2 and straddles the C2 spinous process, secured by sutures.

OBJECTIVE

To offer increased fusion across C1-C2 without the passage of sublaminar wiring or interarticular arthrodesis.

METHODS

A total of 6 patients with atlantoaxial instability underwent C1-C2 fixation using our method from 2015 to 2016. After placement of a C1-C2 screw/rod construct, a cadaveric frozen femoral head allograft was cut into a half-dome with a keyhole and placed over the already decorticated dorsal C1 arch and C2 spinous process. Notches were created in the graft and sutures were placed in the notches and around the rods to secure it firmly in place.

RESULTS

The femoral head's shape allowed for creation of a graft that provides excellent surface area for fusion across C1-C2. There were no intraoperative complications, including dural tears. Postoperatively, no patients had sensorimotor deficits, pain, or occipital neuralgia. 5 patients demonstrated clinical resolution of symptoms by 3 mo and radiographic (computed tomography) evidence of fusion at 1 yr. One patient had good follow-up at 1 mo but died due to complications of Alzheimer disease.

CONCLUSION

The posterior arch femoral head allograft strut technique with securing sutures is a viable option for supplementing screw-rod fixation in the treatment of complex atlantoaxial instability.

Muscle Sparing C1-C2 Laminoplasty: Cadaveric Feasibility Study

BACKGROUND

Posterior cervical approaches for atlantoaxial and craniovertebral junction pathologies with or without instrumentation are often associated with excessive soft tissue dissection and bleeding consequent with disruption of the venous plexus. A few minimally invasive approaches to this region have been reported from clinical and cadaveric studies in an effort to minimize blood loss, reduce soft tissue dissection, and decrease postoperative pain; however, unilateral minimally invasive approaches have not been described. Here, we describe a minimally invasive atlantoaxial and craniovertebral approach.

METHODS

Using fresh cadavers, we performed a novel, right-sided, muscle-sparing minimally invasive C1-C2 laminotomy with laminoplasty for access to the atlantoaxial level and craniovertebral junction and used the traditional approach on left sides.

RESULTS

Using this approach, the atlantoaxial space and craniovertebral junction with wide and generous exposure via unilateral soft tissue dissection and muscle splitting was achieved. After exposure, the musculoosseous unit was easily repositioned, thus allowing for C1-C2 laminoplasty. Grossly, no damage to the vertebral artery or regional nerves was noted.

CONCLUSIONS

We present a novel, unilateral minimally invasive approach to reach the atlantoaxial and craniovertebral junction. This could allow for faster postoperative recovery, less pain and opioid requirement, and increased maintenance of atlantoaxial stability. Such a technique, after being confirmed in patients, could optimize this surgical technique.

Comparison of Two Bone Grafting Techniques Applied During Posterior C1-C2 Screw-Rod Fixation and Fusion for Treating Reducible Atlantoaxial Dislocation

BACKGROUND

Several bone grafting techniques for posterior atlantoaxial arthrodesis have been reported. The techniques of placing a cancellous morselized bone graft (MBG) on decorticated surfaces of the atlantoaxial complex and securing a structural iliac bone graft (SBG) between C1 and C2 have been used widely. The aim of the present study was to compare the outcomes of these 2 bone grafting techniques for atlantoaxial arthrodesis.

METHODS

The data from 64 patients with reducible atlantoaxial dislocation treated using posterior C1-C2 screw-rod fixation and fusion were retrospectively reviewed. The MBG technique had been used in 32 patients and the SBG technique in 32 patients. The time required for bone fusion was recorded. The outcomes were evaluated using the Japanese Orthopaedic Association scale score, Neck Disability Index, visual analog scale (VAS) score for neck pain, patient satisfaction, and neck stiffness and compared between the 2 groups. The donor site complications were also compared, and donor site pain was assessed using a VAS.

RESULTS

At the final follow-up, the bone fusion rate was 100% in both groups. No significant differences were found in the bone fusion time or donor site pain between the 2 groups (P > 0.05). Postoperatively, The Japanese Orthopaedic Association scale scores, Neck Disability Index, and VAS score for neck pain had improved significantly within both groups (P < 0.05), with no statistically significant differences between the 2 groups (P > 0.05). Additionally, no differences were found between the 2 groups in patient satisfaction and neck stiffness postoperatively (P > 0.05).

CONCLUSIONS

The MBG and SBG techniques were both effective for atlantoaxial arthrodesis, with the advantages of reducing the potential risk of catastrophic bleeding of the epidural venous plexus and C2 nerve root injury.

Miniplate-Augmented Interlaminar Fusion in C1-C2 Screwing

OBJECTIVE

The interlaminar fusion combination involving C1-C2 screwing fixation is one of the most effective techniques for atlantoaxial dislocation or subluxation, and the bone graft is usually stabilized by wiring constructs. However, some adverse events were reported during the insertion of sublaminar wiring, such as accidentally damaging the spinal cord or dura. Thus we used the miniplate to stabilize the harvest bone graft on the C1-C2 laminar, which led to a shorter operation time and prevented spinal canal violation. This study investigated the safety and efficacy of the novel surgical technique, namely miniplate-augmented interlaminar fusion.

METHODS

We retrospectively reviewed 43 patients who underwent posterior atlantoaxial fusion with the miniplate-augmented iliac crest autograft at our institute. Complications related to surgery were recorded and calculated. After operation, patients were followed up through routine radiography to examine whether the fusion of the atlantoaxial segment was achieved. Success of fusion was defined as follows: 1) the presence of bone bridging between the bone graft and both the atlas and axis; and 2) the absence of movement of the atlantoaxial spinous process on flexion-extension radiography, which meant that the variation of length measured in 2 views, respectively, was <1 mm. The first time when radiography showed successful fusion after surgery was termed as fusion time and was recorded individually. In addition, overall fusion rates and mean fusion times were analyzed.

RESULTS

Of 43 patients, long-term follow-up data were available for 31 patients, whereas the remaining 12 patients had dropped out (mean follow-up duration, 24.91 months; range, 6-72 months). Among 31 patients, 22 (70.96%) were women and 9 (29.03%) were men. The mean age was 63.33 years. Regarding the etiology, atlantoaxial dislocations or subluxations were caused due to degeneration, rheumatoid arthritis, odontoid fracture, trauma, and os odontoideum in 14 (45%), 3 (10%), 5 (16%), 8 (26%), and 1 (3%) patient(s), respectively. Successful fusion was achieved in 30 (96.77%) patients, with a mean fusion time of 6.23 months, whereas only 1 (3.23%) patient did not meet the fusion criteria. No complications related to the miniplate occurred. We noted vertebral artery rupture not requiring blood transfusion in 1 patient, aspiration pneumonia in 1 patient, urinary tract infection in 1 patient, anemia requiring transfusion in 1 patient, and leg dysesthesia in 1 patient. No neurologic deficit was found.

CONCLUSIONS

Miniplate-augmented interlaminar fusion with C1-C2 screwing resulted in excellent fusion rates with a considerably low probability of complications. Hence this novel technique for bone graft fixation with atlantoaxial screwing has a good efficacy and safety and can serve as an alternative for bone graft fixation during C1-C2 fusion.

C2 Pedicle Screws Combined With C1 Laminar Hooks for Reducible Atlantoaxial Dislocation: An Ideal Salvage Technique for C1-C2 Pedicle Screws

BACKGROUND

A C1 laminar hook can theoretically avoid vertebral artery injury and is less technically demanding. However, only few studies with small samples analyzed the short-term outcomes of C2 pedicle screws combined with C1 laminar hooks (C2PS-C1LH) technique in the treatment of atlantoaxial dislocation. Furthermore, it is not confirmed whether similar clinical outcomes can be achieved with C1-C2 pedicle screw and rod construct (PSRC).

OBJECTIVE

To evaluate the outcomes of C2PS-C1LH and C1-C2 PSRC fixation techniques for treating atlantoaxial dislocation.

METHODS

Data of 52 patients with atlantoaxial dislocation treated by C1-C2 PSRC or C2PS-C1LH fixation were retrospectively reviewed. Outcomes evaluated by visual analog scale score for neck pain (VASSNP), Neck Disability Index (NDI), atlantodental interval (ADI), and the perioperative parameters including blood loss and operation time were analyzed and compared between 2 techniques. Patient satisfaction at final follow-up was also investigated.

RESULTS

There were no complications related to the surgical approach and instrumentation in either group. The mean bone fusion time was 5.06 ± 1.65 mo for the C2PS-C1LH group and 3.93 ± 0.99 mo for the C1-C2 PSRC group (P &gt; .05). Hundred percent of fusion rates were achieved in both groups at month 12 after operation. The ADI, VAS scores, the NDI scores, and the JOA scores were greatly improved in both the groups (P &lt; .05), but there were no significant differences between the 2 groups.

CONCLUSION

C2PS-C1LH fixation technique was comparable to C1-C2 PSRC in the treatment of reducible atlantoaxial dislocation. C2PS-C1LH fixation was an ideal alternative strategy to C1-C2 PSRC fixation.

Comparison of Outcomes Between C1-C2 Screw-Hook Fixation and C1-C2 Screw-Rod Fixation for Treating Reducible Atlantoaxial Dislocation

STUDY DESIGN

Retrospective comparative study.

OBJECTIVE

To compare the outcomes of C1-C2 transarticular screw with C1 laminar hook (TAS + C1H) fixation and C1 trans-arch lateral mass screw with C2 pedicle screw (C1TLMS + C2PS) fixation in the treatment of reducible atlantoaxial dislocation (AAD).

SUMMARY OF BACKGROUND DATA

TAS + C1H is comparable to TAS with posterior wiring techniques and superior to C1 lateral mass screw combined with C2 pedicle screw (C1LMS + C2PS) in biomechanics. There were, however, few studies analyzing the differences in outcomes between TAS + C1H technique and modified C1LMS + C2PS technique (C1TLMS + C2PS) for treating AAD.

METHODS

Data of 30 patients with reducible AAD treated by TAS + C1H fixation and another 30 cases treated by C1TLMS + C2PS fixation were retrospectively analyzed. Bone fusion time was recorded. The outcomes evaluated by American Spinal Injury Association impairment scale, visual analog scale score for neck pain, neck stiffness (none/mild/severe), patient satisfaction, and Neck Disability Index (NDI) were compared between two groups.

RESULTS

There were no complications related to the surgical approach and instrumentation in either group. At the final follow-up, bone graft fusion rates were 100% in both the TAS + C1H fixation group and the C1TLMS + C2PS fixation group (P > 0.05). The neurological status evaluated by American Spinal Injury Association impairment scale were greatly improved in both screw-hook group (P < 0.001) and screw-rod group (P < 0.001), but with no significant differences between groups (P > 0.05). There were no significant differences between two groups in visual analog scale score for neck pain, neck stiffness, patient satisfaction, or Neck Disability Index (all P > 0.05).

CONCLUSION

C1TLMS + C2PS fixation was comparable to TAS + C1H fixation in fusion rate and functional outcomes for treating reducible AAD. To reduce the risk of vertebral artery injury, computed tomography scan, and reconstruction should be done to analyze vertebral artery course and C1-C2 anatomic structures before operation.

LEVEL OF EVIDENCE

3.

Steinmann Pins for C1 Lateral Mass Screw Placement During Atlantoaxial Stabilization

OBJECTIVE

The authors describe a modified technique for placement of the C1 lateral mass screw using a Steinmann pin as a guide. This technique minimizes dissection and provides atlantoaxial stabilization during arthrodesis.

METHODS

In our technique, a nonthreaded 1.6-mm spade-tip Steinmann pin is placed into the lateral mass of C1 to serve as a guide over which a powered drill is used for screw insertion. Perioperative data were collected for consecutive patients who underwent a C1-2 arthrodesis that involved the modified technique between March 2010 and July 2016. Data included blood loss, operative times, and C2 nerve root injury.

RESULTS

The data for 93 patients were reviewed. Most (91.4%) patients presented with a fracture from an acute trauma. A mean of 1.97 levels was fused in these patients, with a mean blood loss of 76 mL and a mean operative time of 144 minutes. The overall morbidity and mortality rate was 10.7%. The morbidity rate of 7.5% included 30-day postoperative complications of respiratory failure and dysphasia. There were no postoperative vertebral artery injuries, hardware failures, or instances of occipital neuralgia.

CONCLUSIONS

The use of Steinmann pins to guide the placement of C1 lateral mass screws is safe and effective in C1-2 arthrodesis. Limiting dissection minimizes blood loss and injury, maintains efficient operative time, and assists in accurate placement of the screws. Furthermore, with less manipulation and retraction of the C2 nerve root, postoperative occipital neuralgia and the need for C2 root transection are avoided.

Complications of Anterior and Posterior Cervical Spine Surgery

Cervical spine surgery performed for the correct indications yields good results. However, surgeons need to be mindful of the many possible pitfalls. Complications may occur starting from the anaesthestic procedure and patient positioning to dura exposure and instrumentation. This review examines specific complications related to anterior and posterior cervical spine surgery, discusses their causes and considers methods to prevent or treat them. In general, avoiding complications is best achieved with meticulous preoperative analysis of the pathology, good patient selection for a specific procedure and careful execution of the surgery. Cervical spine surgery is usually effective in treating most pathologies and only a reasonable complication rate exists.

Posterior Open Reduction and Interlaminae Compression Fusion for Os Odontoideum with Atlantoaxial Dislocation

OBJECTIVE

To evaluate the outcome of posterior open reduction and interlaminae compression fusion using a screw-rod system combined with a structural iliac bone graft in the treatment of atlantoaxial dislocation (AAD) secondary to os odontoideum.

METHODS

A retrospective study was performed on 24 patients with AAD secondary to os odontoideum. All cases were with partial reduction after skeletal traction. Intraoperative open reduction and fixation were performed with a posterior screw-rod system, followed by interlaminae compression of an autologous iliac bone graft for fusion. The modified atlanto-dental interval (MADI) was measured to assess the degree of dislocation before traction, after traction, and postoperatively. Japanese Orthopaedic Association (JOA) score, Nurick scale score, visual analog scale score for neck pain (VASSNP), Neck Disability Index (NDI) score, and neck stiffness were used to evaluate functional outcomes.

RESULTS

The mean duration of follow-up was 43.0 ± 24.0 months. All patients achieved relief of symptoms and solid bone fusion. There were no complications associated with instrumentation and operation. At the final follow-up, the average MADI was reduced to 2.0 ± 0.8 mm (pretraction: 9.2 ± 1.1 mm; post-traction: 6.6 ± 0.7 mm; P < 0.001). The neck stiffness was significantly relieved (P < 0.001), and function of the spinal cord manifested by the JOA score and Nurick scale score significantly improved (all P < 0.001). The NDI score and VASSNP markedly decreased (all P < 0.001).

CONCLUSIONS

Intraoperative open reduction and interlaminae compression fusion using a posterior screw-rod system combined with a structural iliac bone graft is a safe and effective procedure for AAD secondary to os odontoideum.

Allograft versus autograft for pediatric posterior cervical and occipito-cervical fusion: a systematic review of factors affecting fusion rates

OBJECT Fusion rates are high for children undergoing posterior cervical fusion (PCF) and occipito-cervical fusion (OCF). Autologous bone has been widely used as the graft material of choice, despite the risk of donor-site morbidity associated with harvesting the bone, possibly because very low fusion rates were reported with posterior allograft cervical fusions in children several decades ago. Higher overall fusion rates using allograft in adults, associated with improvements in internal fixation techniques and the availability of osteoinductive substances such as bone morphogenetic protein (BMP), have led to heightened enthusiasm for the use of bank bone during pediatric PCF. A systematic review was performed to study factors associated with successful bone fusion, including the type of bone graft used. METHODS The authors performed a comprehensive PubMed search of English-language articles pertaining to PCF and OCF in patients less than 18 years old. Of the 561 abstracts selected, 148 articles were reviewed, resulting in 60 articles that had sufficient detail to be included in the analysis. A meta-regression analysis was performed to determine if and how age, fusion technique, levels fused, fusion substrate, BMP use, postoperative bracing, and radiographic fusion criteria were related to the pooled prevalence estimates. A systematic review of the literature was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. RESULTS A total of 604 patients met the specific inclusion and exclusion criteria. The overall fusion rate was 93%, with a mean age of 9.3 years and mean follow-up of 38.7 months. A total of 539 patients had fusion with autograft (94% fusion rate) and 65 patients with allograft (80% fusion rate). Multivariate meta-regression analysis showed that higher fusion rates were associated with OCF compared with fusions that excluded the occiput (p < 0.001), with the use of autograft instead of allograft (p < 0.001), and with the use of CT to define fusion instead of plain radiography alone. The type of internal fixation, the use of BMP, patient age, and the duration of follow-up were not found to be associated with fusion rates in the multivariate analysis. CONCLUSIONS Fusion rates for PCF are high, with higher rates of fusion seen when autograft is used as the bone substrate and when the occiput is included in the fusion construct. Further study of the use of allograft as a viable alternative to autograft bone fusion is warranted because limited data are available regarding the use of allograft in combination with more rigid internal fixation techniques and osteoinductive substances, both of which may enhance fusion rates with allograft.

Bilateral Pedicle and Crossed Translaminar Screws in C2

Multiple techniques exist for the fixation of C2, including axial pedicle screws and bilateral translaminar screws. We describe a novel method of incorporating both the translaminar and pedicle screws within C2 to improve fixation to the subaxial spine in patients requiring posterior cervical instrumentation for deformity correction or instability. We report three cases of patients with cervical spinal instability, who underwent cervical spine instrumentation for stabilization and/or deformity correction. Bilateral C2 pedicle screws were inserted, followed by bilateral crossed laminar screws. The instrumentation method successfully achieved fixation in all three patients. There were no immediate postoperative complications, and hardware positioning was satisfactory. Instrumenting C2 with translaminar and pedicle screws is technically feasible, and it may improve fixation to the subaxial spine in patients with poor bone quality or severe subaxial deformity, which require a stronger instrumentation construct.

Posterior atlantoaxial fixation: a review of all techniques

BACKGROUND CONTEXT

Posterior atlantoaxial fixation is an effective treatment for atlantoaxial instability. Great advancements on posterior atlantoaxial fixation techniques have been made in the past decades. However, there is no article reviewing all the posterior atlantoaxial fixation techniques yet.

PURPOSE

The aim was to review the evolution and advancements of posterior atlantoaxial fixation.

STUDY DESIGN

This was a literature review.

METHODS

The application of all posterior fixation techniques in atlantoaxial stabilization, including wiring techniques, interlaminar clamp fixation, transarticular fixation, screw-plate systems, screw-rod systems, and hook-screw systems, are reviewed and discussed. Recent advancements on the novel technique of atlantoaxial fixation are described. The combination of the C1 and C2 screws in screw-rod systems are described in detail.

RESULTS

All fixation techniques are useful. The screw-rod system appears to be the most popular approach. However, many novel or modified fixation methods have been introduced in recent years.

CONCLUSIONS

Great advancements on posterior atlantoaxial fixation techniques have been made in the past decades. The wiring technique and interlaminar clamps technique have fallen out of favor because of the development of newer and superior fixation techniques. The C1-C2 transarticular screw technique may remain the gold standard for atlantoaxial fusion, whereas screw-rod systems, especially the C1 pedicle screw combined with C2 pedicle/pars screw fixation, have become the most popular fixation techniques. Hook-screw systems are alternatives for atlantoaxial fixation.

Comparison of Clinical Outcomes of Posterior C1-C2 Temporary Fixation Without Fusion and C1-C2 Fusion for Fresh Odontoid Fractures

BACKGROUND:

Posterior C1-C2 temporary-fixation technique can spare the range of motion (ROM) of the atlantoaxial joint after odontoid fracture healing. However, few studies analyze the difference in clinical outcome between this technique and posterior C1-C2 fusion technique for new odontoid fracture.

OBJECTIVE:

To verify whether the clinical outcome of the posterior C1-C2 temporary-fixation technique is superior to that of the posterior C1-C2 fusion technique in the treatment of a new odontoid fracture.

METHODS:

Twenty-one of 22 patients who underwent posterior C1-C2 temporary fixation of an odontoid fracture achieved fracture healing and regained motion of the atlantoaxial joint. The functional outcomes of these 21 patients were compared with that of a control group, which consisted of 21 randomly enrolled cases with posterior C1-C2 fixation and fusion. The differences between the 2 groups in the visual analog scale score for neck pain, neck stiffness, Neck Disability Index, 36-Item Short Form Health Survey, and time to fracture healing were analyzed.

RESULTS:

Significantly better outcomes were observed in the temporary-fixation group for visual analog scale score for neck pain, Neck Disability Index, and neck stiffness. The outcomes in the temporary-fixation group was superior to those in the fusion group in all dimensions of the 36-Item Short Form Health Survey. There were no significant differences in fracture healing rate and time to fracture healing between the 2 techniques.

CONCLUSION:

Functional outcomes were significantly better after posterior C1-C2 temporary fixation than after fusion. Temporary fixation can be used as a salvage treatment for an odontoid fracture with an intact transverse ligament in cases of failure of, or contraindication to, anterior screw fixation.

Posterior reduction and temporary fixation for odontoid fracture: a salvage maneuver to anterior screw fixation

STUDY DESIGN

A prospective study.

OBJECTIVE

To evaluate the outcomes of posterior reduction and temporary fixation using the C1-C2 screw-rod system for odontoid fracture unsuitable for anterior screw fixation.

SUMMARY OF BACKGROUND DATA

Anterior screw fixation has become the most widely used surgical procedure for the stabilization of odontoid fractures. However, if there is any contraindication for anterior fixation, posterior atlantoaxial fusion is preferred, eliminating the normal rotation of the atlantoaxial complex.

METHODS

A consecutive series of 22 patients with odontoid fracture unsuitable for anterior screw fixation were involved in this study. Posterior reduction and fixation without fusion using the C1-C2 screw-rod system was performed. Once fracture healing was obtained, instrumentation was removed. The visual analogue scale of neck pain, neck stiffness, American Spinal Injury Association impairment scale, patient satisfaction, and neck disability index were recorded. The range of motion of C1-C2 in flexion-extension and rotation was calculated.

RESULTS

The average age at internal fixation surgery was 40.2±11.3 years. The mean duration of follow-up was 41.8±26.8 months. There were no complications associated with instrumentation. All patients returned to their preoperative work. Fracture healing was observed in 21 patients and the instrumentation was removed. After removing the instrumentation, the visual analogue scale was reduced and neck stiffness were relieved (all P<0.01). Patient satisfaction and neck disability index had improved (all P<0.01). The range of motion of C1-C2 returned to 4.75°±1.62° and 25.70°±5.51° in flexion-extension and in rotation, respectively. No osteoarthritis was observed at the C1-C2 lateral mass joints.

CONCLUSION

Posterior reduction and temporary fixation using the C1-C2 screw-rod system was an optimal salvage maneuver to anterior screw fixation for odontoid fracture. It could effectively avoid the motion loss of C1-C2 caused by posterior atlantoaxial fusion.

LEVEL OF EVIDENCE

3.

Posterior C1-C2 screw and rod instrument for reduction and fixation of basilar invagination with atlantoaxial dislocation

PURPOSE

To report the surgical technique and preliminary clinical results for the treatment of basilar invagination (BI) with atlantoaxial dislocation (AAD) by posterior C1-C2 pedicle screw and rod instrument.

METHODS

Between July 2012 and August 2013, 33 patients who had BI with AAD underwent surgery at our institution. Pre and postoperative three-dimensional computed tomographic (CT) scans were performed to assess the degree of dislocation. Magnetic resonance (MR) imaging was used to evaluate the compression of the medulla oblongata. For all patients, reduction of the AAD was conducted by two steps: fastening nuts and rods was performed to achieve the horizontal reduction. Distraction between C1 and C2 screws was performed to obtain the vertical reduction.

RESULTS

No neurovascular injury occurred during surgery. Follow-up ranged from 6 to 15 months (mean 10.38 months) in 32 patients. Post-operative three-dimensional CT showed that complete horizontal reduction was obtained in 30/33 (90.9%), and complete vertical reduction was obtained in 31/33 (93.9%). The repeated three-dimensional CT and MR image demonstrated that bony fusion and the decompression of the medulla oblongata were obtained in all patients. Clinical symptoms improved significantly 3 months after surgery.

CONCLUSIONS

This C1-C2 pedicle screw and rod instrument is a promising technique for the treatment of BI with AAD.

Minimally invasive anterior transarticular screw fixation and microendoscopic bone graft for atlantoaxial instability

PURPOSE

Even though transarticular screw (TAS) fixation has been commonly used for posterior C1-C2 arthrodesis in both traumatic and non-traumatic lesions, anterior TAS fixation C1-2 is a less invasive technique as compared with posterior TAS which produces significant soft tissue injury, and there were few reports on percutaneous anterior TAS fixation and microendoscopic bone graft for atlantoaxial instability. The goals of our study were to describe and evaluate a new technique for anterior TAS fixation of the atlantoaxial joints for traumatic atlantoaxial instability by analyzing radiographic and clinical outcomes.

METHODS

This was a retrospective study of seven consecutive patients with C1-C2 instability due to upper cervical injury treated by a minimally invasive procedure from May 2007 to August 2009. Bilateral anterior TAS were inserted by the percutaneous approach under Iso-C3D fluoroscopic control. The atlantoaxial joint space was prepared for morselized autogenous bone graft under microendoscopy. The data for analysis included time after the injuries, operating time, intraoperative blood loss, X-ray exposure time, clinical results, and complications. Radiographic evaluation included the assessment of atlantoaxial fusion rate and placement of TAS. Bone fusion of the atlantoaxial joints was assessed by flexion extension lateral radiographs and 1-mm thin-slice computed tomography images as radiographic results. Clinical assessment was done by analyzing the recovery state of clinical presentation from the preoperative period to the last follow-up and by evaluating complications.

RESULTS

A total of 14 screws were placed correctly. The atlantoaxial solid fusion without screw failure was confirmed by CT scan in seven cases after a mean follow-up of 27.5 months (range 18-45 months). All patients with associated clinical presentation made a recovery without neurologic sequelae. Postoperative dysphagia occurred and disappeared in two cases within 5 days after surgery. There were no other complications during the follow-up period.

CONCLUSIONS

Percutaneous anterior TAS fixation and microendoscopic bone graft could be an option for achieving C1-C2 stabilization with several potential advantages such as less tissue trauma and better accuracy. Bilateral TAS fixation and morselized autograft affords effective fixation and solid fusion by a minimally invasive approach.