Treatment of basilar invagination with atlantoaxial dislocation: atlantoaxial joint distraction and fixation with transoral atlantoaxial reduction plate (TARP) without odontoidectomy

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.

Release, reduction, and fixation of one-stage posterior approach for basilar invagination with irreducible atlantoaxial dislocation

PURPOSE

We evaluate the efficacy, safety and indications of single stage posterior release, reduction, and fixation of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD).

MATERIALS AND METHODS

Seventeen patients with BI and IAAD consecutively underwent one-stage release, reduction, and fixation by a posterior approach from July 2000 to June 2015 were followed up for at least 12 months. There were 8 males. Mean age was 56 35.2 ± 13.8 years (range 12-56). The clinical symptoms and signs of the patients were recorded. Pre- and postoperative imaging examinations were performed. Neurological function was assessed using the Japanese Orthopedic Association (JOA) and Ranawat scores.

RESULTS

Average follow-up time was 47.4 months (12-97 months). The JOA score increased from preoperative 4-10 (8.06 ± 2.52) to postoperative 13-16 (15.20 ± 0.62). The preoperative Chamberlain line, McRae line, Wackenheim line, atlantodens interval, and cervico medullary angle were 12.52 ± 5.17 mm, 6.59 ± 3.04 mm, 6.96 ± 4.32 mm, 9.88 ± 1.93 mm, and 115.35 ± 12.40°, respectively. The postoperative values were 2.0 ± 3.67 mm, -3.06 ± 1.85 mm, -1.76 ± 2.88 mm, 1.17 ± 1.18 mm, and 136.76 ± 11.44°, respectively.

CONCLUSION

One-stage release, reduction, and fixation for patients with BI and IAAD through a posterior approach is safe and efficient.

Biomechanical properties of different anterior and posterior techniques for atlantoaxial fixation: a finite element analysis

BACKGROUND

Many techniques for atlantoaxial fixation have been developed. However, the biomechanical differences among various atlantoaxial fixation methods remain unclear. This study aimed to evaluate the biomechanical influence of anterior and posterior atlantoaxial fixation techniques on fixed and nonfixed segments.

METHODS

An occiput-C7 cervical finite element model was used to construct 6 surgical models including a Harms plate, a transoral atlantoaxial reduction plate (TARP), an anterior transarticular screw (ATS), a Magerl screw, a posterior screw-plate, and a screw-rod system. Range of motion (ROM), facet joint force (FJF), disc stress, screw stress, and bone-screw interface stress were calculated.

RESULTS

The C1/2 ROMs were relatively small in the ATS and Magerl screw models under all loading directions except for extension (0.1°-1.0°). The posterior screw-plate system and screw-rod system generated greater stresses on the screws (77.6-1018.1 MPa) and bone-screw interfaces (58.3-499.0 MPa). The Harms plate and TARP models had relatively small ROMs (3.2°-17.6°), disc stress (1.3-7.6 MPa), and FJF (3.3-106.8 N) at the nonfixed segments. Changes in disc stress and FJF of the cervical segments were not consistent with changes in ROM.

CONCLUSIONS

ATS and Magerl screws may provide good atlantoaxial stability. The posterior screw-rod system and screw-plate system may have higher risks of screw loosening and breakage. The Harms plate and TARP model may more effectively relieve nonfixed segment degeneration than other techniques. The C0/1 or C2/3 segment may not be more susceptible to degeneration than other nonfixed segments after C1/2 fixation.

Treating Pediatric Irreducible Atlantoaxial Rotatory Fixation (IAARF) by Unlocking Facet Joint Through Transoral Approach and Fixing With Slim-TARP Plate (15 Cases Series)

BACKGROUND

Irreducible atlantoaxial rotatory fixation (IAARF) often requires surgical treatment. Transoral unlocking the facet joints is a key measure for the treatment of IAARF. We investigate a novel method for treating pediatric IAARF by unlocking facet joint through transoral appraoch and fixed with slim-tarp plate in same stage with same approach.

OBJECTIVE

The objective of this study is to investigate the method and efficacy of a unique transoral approach to unlock facet joints and fixation with slim-shaped transoral anterior reduction plate (slim-TARP) plate in the treatment of IAARF.

METHODS

Fifteen patients diagnosed with AARF were transferred to our hospital. After 1 week of bidirectional cervical cranial traction, they were diagnosed with irreducible AARF that, and then underwent transoral release and fixation with slim-TARP plate procedures. Postoperative computed tomography and magnetic resonance were used to evaluate the reduction effect, bone fusion, and fusion time. Japanese orthopaedic association scores were used to compare the recovery of spinal cord function in patients before and after surgery. Complications such as wound infection, neurovascular injury, and loosening of internal fixation were evaluated too.

RESULTS

All 15 patients underwent transoral unlocking facet joint and fixation with slim-TARP procedures smoothly. The operation time were 129.2±11.9 minutes, blood loose were 83±23 mL. There were no neurological injury, wound infections, verified or suspected vertebral artery injury, etc. All patients were followed up for a mean of 17.8±6.6 months (range: 12 to 36 mo). Bony fusion was achieved in all patients. Mean fusion time was 3.6±1.2 months (range: 3 to 6 mo). Complete correction of torticollis was achieved in all 15 cases. Preoperative symptoms of neck pain and limitation of neck movement were effectively alleviated at 3 months after surgery. The 3 patients with preoperative neurological deficits had significant relief after surgery, and their latest follow-up results showed that their Japanese orthopaedic association scores increased from 13.0±1.0 to 16.3±0.6.

CONCLUSIONS

Transoral release and fixation with slim-TARP plate by transoral approach is a feasible and safe method for treating pediatric irreducible atlantoaxial rotatory fixation.

Treatment of irreducible atlantoaxial dislocation by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach

OBJECTIVE

Investigate a novel method for treating irreducible atlantoaxial dislocation (IAAD) or with basilar invagination (BI) by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach.

METHOD

From March 2015 to December 2019, 213 consecutive patients diagnosed as IAAD/BI were treated with transoral bony deformity remodeling and releasing combined with plate fixation. The main clinical symptoms include neck pain, headache, numbness of the limbs, weakness, unstable walking, inflexible hand-held objects, and sphincter dysfunction. The bony factors that impact reduction were divided into as follows: type A1 (sloping of upper facet joint in C2), type A2 (osteophyte in lateral mass joints between C1 and C2), type A3 (ball-and-socket deformity of lateral mass joint), type A4 (vertical interlocking between lateral mass joints of C1-C2), type A5 (regional bone fusion in lateral mass joints), type B1 (bony factor hindering reduction between the atlas-dens gap), type B2 (uncinate odontoid deformity), and type B3 (hypertrophic odontoid deformity). All of them were treated with bony deformity osteotomy, remodeling, and releasing techs.

RESULT

The operation time was 144 [Formula: see text] 25 min with blood loss of 102 [Formula: see text] 35 ml. The average pre-operative ADI improved from 7.5 [Formula: see text] 3.2 mm pre-surgery to 2.5 [Formula: see text] 1.5 mm post-surgery (p < 0.05). The average VDI improved from 12.3 [Formula: see text] 4.8 mm pre-surgery to 3.3 [Formula: see text] 2.1 mm post-surgery (p < 0.05). The average pre-operative CMA improved from 115 [Formula: see text] 25° pre-surgery to 158 [Formula: see text] 21° post-surgery (p < 0.05); the pre-operative CAA changed from 101 [Formula: see text] 28° pre-surgery to 141 [Formula: see text] 10° post-surgery. After the operation, the clinic symptoms improved, and the JOA score improved from 9.3 [Formula: see text] 2.8 pre-operatively to 13.8 [Formula: see text] 2.5 in the sixth months of follow-up.

CONCLUSION

In addition to soft tissue factors, bony obstruction was another important factor impeding atlantoaxial reduction. Transoral bony deformity osteotomy, remodeling, releasing combined with plate fixating was effective in treating IAAD/BI with bony obstruction factors.

Posterior two-step distraction and reduction for basilar invagination with atlantoaxial dislocation: a novel technique for precise control of reduction degree without traction

PURPOSE

The pathological changes of basilar invagination (BI) and atlantoaxial dislocation (AAD) include vertical and horizontal dislocations. Current surgical techniques have difficulty in accurately controlling the degree of reduction in these two directions and often require preoperative traction, which increases patients' pain, hospital stay, and medical cost. This study aimed to introduce a novel technique for accurately reducing horizontal and vertical dislocation without preoperative traction and report the radiological and clinical outcomes.

METHODS

From 2010 to 2020, patients with BI and AAD underwent posterior two-step distraction and reduction (TSDR) and occipitocervical fixation. Radiological examination was used to evaluate the reduction degree (RD) and compression. Japanese Orthopedic Association (JOA) score was used to evaluate clinical outcome.

RESULTS

A total of 55 patients with BI and AAD underwent TSDR and occipitocervical fusion. The clinical symptoms of 98.2% of them improved. JOA score increased significantly after the operation. Appropriate (50% ≤ RD < 80%) or satisfactory (RD ≥ 80%) horizontal reduction was achieved in 92.7% of patients, and 90.9% obtained appropriate or satisfactory vertical reduction. Thirty-one patients did not undergo preoperative skull traction. There was no significant difference in radiological outcomes or JOA scores between the traction and non-traction groups. However, the length of hospital stay in the traction group was longer than that in the non-traction group.

CONCLUSION

TSDR enables horizontal and vertical reduction. It is a safe, simple, and effective technique for patients with BI and AAD. Despite the absence of preoperative skull traction, the degree of reduction and clinical outcomes were satisfactory.

Preoperative management and postoperative complications associated with transoral decompression for the upper cervical spine

Purpose

This review aimed to describe the preoperative management and postoperative complications associated with transoral decompression of the upper cervical spine, and to clarify the risk factors, related issues and complication management.

Methods

Studies on transoral decompression for the upper cervical spine were reviewed systematically. The preoperative management and postoperative complications associated with transoral decompression for upper cervical deformities were analyzed.

Results

Evidence suggests that preoperative management in patients undergoing transoral decompression for the upper cervical spine is closely related to the occurrence of postoperative complications. Hence, preoperative surgical planning, preoperative preparation, and oral nursing care should be seriously considered in these patients. Moreover, while being established as an effective and safe method, transoral decompression is associated with several postoperative complications, which could be prevented by elaborate preoperative management, improved surgical skills, and appropriate precautionary measures.

Conclusions

The effectiveness and safety of transoral decompression has been improved by the constant development of operative techniques and advanced auxiliary diagnostic and therapeutic methods, with the understanding of the anatomical structure of the craniocervical joint. Therefore, the incidence rates of postoperative complications have decreased. The application of individualized anterior implants and less-invasive endoscopic endonasal approach has improved the effectiveness of transoral decompression and reduced the associated complications.

Usefulness of a Three-Dimensional-Printed Model in the Treatment of Irreducible Atlantoaxial Dislocation with Transoral Atlantoaxial Reduction Plate

Objective

To evaluate the usefulness of a 3D‐printed model for transoral atlantoaxial reduction plate (TARP) surgery in the treatment of irreducible atlantoaxial dislocation (IAAD).

Methods

A retrospective review was conducted of 23 patients (13 men, 10 women; mean age 58.17 ± 5.27 years) with IAAD who underwent TARP from January 2015 to July 2017. Patients were divided into a 3D group (12 patients) and a non‐3D group (11 patients). A preoperative simulation process was undertaken for the patients in the 3D group, with preselection of the TARP system using a 3D‐printed 1:1 scale model, while only imaging data was used for the non‐3D group. Complications, clinical outcomes (Japanese Orthopaedic Association [JOA] and visual analogue score [VAS]), and image measurements (atlas–dens interval [ADI], cervicomedullary angle [CMA], and clivus‐canal angle [CCA]) were noted preoperatively and at the last follow up.

Results

A total of 23 patients with a follow‐up time of 16.26 ± 4.27 months were included in the present study. The surgery duration, intraoperative blood loss, and fluoroscopy times in the 3D group were found to be shorter than those in non‐3D group, with statistical significance. The surgery duration was 3.29 ± 0.45 h in the 3D group and 4.68 ± 0.90 h in the non‐3D group, and the estimated intraoperative blood loss was 131.67 ± 43.03 mL in the 3D group and 185.45 ± 42.28 mL in the non‐3D group. No patients received blood transfusions. The intraoperative fluoroscopy times were 5.67 ± 0.89 in the 3D group and 7.91 ± 1.45 in the non‐3D group. Preoperatively and at last follow up, JOA and VAS scores and ADI, CCA, and CMA were improved significantly within the two groups. However, no statistical difference was observed between the two groups. However, surgical site infection occurred in 1 patient in the 3D group, who underwent an emergency revision operation of the removal of TARP device and posterior occipitocervical fixation; the patient recovered 2 weeks after the surgery. In 2 patients in the traditional group, a mistake occurred in the placement of screws, with no neurological symptoms related to the misplacement.

Conclusion

Preoperative surgical simulation using a 3D‐printed real‐size model is an intuitive and effective aid for TARP surgery for treating IAAD. The 3D‐printed biomodel precisely replicated patient‐specific anatomy for use in complicated craniovertebral junction surgery. The information was more useful than that available with 3D reconstructed images.

Surgical treatment of a complex craniocervical malformation combined with posterior cranial fossa teratoma: a case report and literature review

Background

Basilar invagination (BI) with atlantoaxial dislocation (AAD) is not uncommon in patients with scoliosis, Klippel-Feil syndrome (KFS), and other bone deformities. Cases with combinations of the abovementioned dislocations and deformities with posterior cranial fossa teratoma are rare in the clinic and difficult to handle.

Case presentation

This case presents a 34-year-old woman diagnosed with atlantoaxial dislocation and posterior cranial fossa mass. After two surgeries, the posterior cranial teratoma was completely removed with satisfactory atlantoaxial reduction. The postoperative 1-year follow-up examination showed that the bone graft fusion was successful, without remaining significant dysfunction.

Conclusions

The surgical risk of irreducible atlantoaxial dislocation combined with posterior cranial fossa tumor is huge. Thus, it needs to be fully preoperatively evaluated and managed carefully in accordance with sound surgical principles.

Surgical treatment for basilar invagination with irreducible atlantoaxial dislocation: transoral atlantoaxial reduction plate fixation vs occipitocervical fixation

BACKGROUND

Transoral atlantoaxial reduction plate (TARP) fixation or occipitocervical fixation (OF) is an effective treatment for basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD). But, all current clinical studies involved a single surgical procedure. The clinical effects of TARP and OF operation for BI with IAAD have yet to be compared. We therefore present this report to compare the treatment of TARP and OF procedure for BI with IAAD.

METHODS

Fifty-six patients with BI with IAAD who underwent TARP or OF operation from June 2011 to June 2017 were retrospectively analyzed. Among these, 35 patients underwent TARP operation (TARP group), and 21 patients underwent OF operation (OF group). We compared the difference of clinical, radiological, and surgical outcomes between the TARP and OF groups postoperatively.

RESULTS

Compared with OF group, the operative time and blood loss in TARP group were lower. There was no statistical difference in the atlantodental interval (ADI), clivus canal angle (CCA), cervicomedullary angle (CMA), distance between the top of the odontoid process and the Chamberlain line (CL) and Japanese Orthopaedic Association (JOA) score between the TARP and OF groups preoperatively, but the improvements of these parameters in the TARP group were superior to those in the OF group postoperatively. The fusion rates were higher in the TARP group than those in the OF group at the early stage postoperatively.

CONCLUSIONS

TARP and OF operations are effective surgical treatment for BI with IAAD, but the performance of reduction and decompression and earlier bone fusion rates of TARP procedure are superior to those of OF.

Transoral intraarticular cage distraction and C-JAWS fixation for revision of basilar invagination with irreducible atlantoaxial dislocation

Background

The revision surgery of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD) after a previous occipitocervical fusion (OCF) is challenging. Transoral revision surgery has more advantages than a combined anterior and posterior approach in addressing this pathology. The C-JAWS is a cervical compressive staple that has been used in the lower cervical spine with many advantages. Up to now, there is no report on the application of C-JAWS in the atlantoaxial joint. We therefore present this report to investigate the clinical outcomes of transoral intraarticular cage distraction and C-JAWS fixation for revision of BI with IAAD.

Methods

From June 2011 to June 2015, 9 patients with BI and IAAD were revised by this technique after previous posterior OCF in our department. Plain cervical radiographs, computed tomographic scans and magnetic resonance imaging were obtained pre- and postoperatively to assess the degree of atlantoaxial dislocation and compression of the cervical cord. The Japanese Orthopedic Association (JOA) score was used to evaluate the neurological function.

Results

The revision surgeries were successfully performed in all patients. The average follow-up duration was 18.9 ± 7.3 months (range 9–30 months). The postoperative atlas-dens interval (ADI), cervicomedullary angle (CMA), distance between the top of the odontoid process and the Chamberlain line (CL) and JOA score were significantly improved in all patients (P < 0.05). Bony fusion was achieved after 3–9 months in all cases. No patients developed recurrent atlantoaxial instability.

Conclusions

Transoral revision surgery by intraarticular cage distraction and C-JAWS fixation could provide a satisfactory outcome for BI with IAAD after a previous unsuccessful posterior operation.

Outcome of Surgery for Congenital Craniovertebral Junction Anomalies with Atlantoaxial Dislocation/Basilar Invagination: A Retrospective Study of 94 Patients

OBJECTIVE

To evaluate the results of surgery for congenital craniovertebral junction (CVJ) anomalies with atlantoaxial dislocation (AAD)/basilar invagination (BI) and compare the results of transoral odontoidectomy and posterior fusion (TOO+PF) with only posterior fusion (PF) in patients with irreducible AAD/BI.

METHODS AND RESULTS

All 94 patients with congenital CVJ anomalies with AAD/BI operated on during the 3-year study period (June 2013-May 2016) were included. Of these patients, 55 had irreducible AAD/BI and the remaining 39 had reducible AAD/BI. TOO+PF was restricted to patients (34/94; 36.2%) with irreducible AAD/BI when reduction and realignment by intraoperative C1-C2 facet joint manipulation were considered technically difficult and risky. The remaining patients with irreducible AAD/BI and all the patients with reducible AAD/BI (60/94; 63.8%) were managed with only posterior fusion. Poor preoperative Nurick grade, preoperative dyspnea/lower cranial nerve deficits, and syringomyelia were associated with significantly higher incidence of postoperative pulmonary complications. Follow-up ≥3 months (final follow-up) was available for 87 patients. Good outcome (Nurick grade 0-3) at final follow-up was noted in 90% (45/50) of the patients with irreducible AAD/BI and 91.9% (34/37) of the patients with reducible AAD/BI. Preoperative poor Nurick grade (4-5) was the only factor associated with poor outcome. No significant difference in perioperative complications, outcome, and fusion was noted between patients who underwent TOO+PF or only PF for irreducible AAD/BI.

CONCLUSIONS

Many of the patients with congenital AAD/BI showed remarkable recovery after surgery. Preoperative poor Nurick grade (4-5) is associated with poor outcome. TOO+PF is a safe alternative treatment option for irreducible AAD/BI when only PF techniques are technically difficult/risky.

Reconsideration of the transoral odontoidectomy in complex craniovertebral junction patients with irreducible anterior compression

Background

Although the single-stage posterior realignment craniovertebral junction (CVJ) surgery could treat most of the basilar invagination (BI) and atlantoaxial dislocation (AAD), there are still some cases with incomplete decompression of the spinal cord, which remains a technique challenging situation.

Methods

Eleven patients were included with remained myelopathic symptoms after posterior correction due to incomplete decompression of the spinal cord. Transoral odontoidectomy assisted by image-guided navigation and intraoperative CT was performed. Clinical assessment and image measurements were performed preoperatively and at the most recent follow-up.

Results

Eleven patients were followed up for an average of 47 months. Symptoms were alleviated in 10 of 11 patients (90.9%). One patient died of an unknown reason 1 week after the transoral approach. The clinical and radiological parameters pre- and postoperatively were reported.

Conclusion

Transoral odontoidectomy as a salvage surgery is safe and effective for properly selected BI and AAD patients after inadequate indirect decompression from posterior distraction and fixation. Image-guided navigation and intraoperative CT can provide precise information and accurate localization during operation, thus enabling complete resection of the odontoid process and decompression of the spinal cord.

Occipitocervical fusion combined with 3-dimensional navigation and 3-dimensional printing technology for the treatment of atlantoaxial dislocation with basilar invagination: A case report

INTRODUCTION

Basilar invagination (BI) is a common deformity in the occipitocervical region. The traditional surgical method of BI is direct transoral decompression followed by posterior decompression and fixation. Posterior-only decompression and fixation have achieved good efficacy in the treatment of BI in recent years, but complications are common due to the operation in the upper cervical vertebra and the medulla oblongata region. Moreover, posterior-only occipitocervical fusion combined with an intraoperative 3-dimensional (3D) navigation system is relatively rare, and reports of this procedure combined with 3D printing technology have not been published. We present a case of BI treated with posterior-only occipitocervical fusion combined with 3D printing technology and 3D navigation system to reduce the risk of surgical complications.

PATIENT CONCERNS

A 55-year-old patient with a history of neck pain and numbness of the extremities for 6 years developed a walking disorder for 1 year.

DIAGNOSES

Atlantoaxial dislocation with BI.

INTERVENTIONS

The patient underwent posterior-only occipitocervical fusion combined with intraoperative 3D navigation system and 3D printing technology.

OUTCOMES

The patient's walking disorder was resolved and he was able to walk approximately 100 m by himself when he was allowed to get up and move around with the help of a neck brace. At 6 months postoperatively, the patient reported that the numbness of the limbs was reduced, and he could walk >500 m by himself.

CONCLUSION

Occipitocervical fusion is one of the established techniques for the treatment of BI. The biggest advantage of the 2 technologies was that it ensured precise implant placement. The advantages of intraoperative 3D navigation systems are as follows: real-time intraoperative monitoring of the angle and depth of implant placement; the best nailing point can be determined at the time of implantation, rather than according to the operator's previous experience; and the extent of screw insertion is visible to the naked eye, rather than being dependent on the "hand feel" of the surgeon. At the same time, the 3D printing technology can be applied to clarify the relationship between blood vessels and bone around the implant to minimize injury to important structures during implantation.

Management of pediatric patients with irreducible atlantoaxial dislocation: transoral anterior release, reduction, and fixation

OBJECTIVE

Although transoral atlantoaxial reduction plate (TARP) surgery has been confirmed to be safe and effective for adults who have irreducible atlantoaxial dislocation (IAAD) with or without basilar invagination or upper cervical revision surgery, it is rarely used to treat these disorders in children. The authors of this study aimed to report on the use of the anterior technique in treating pediatric IAAD.

METHODS

In this retrospective study, the authors identified 8 consecutive patients with IAAD who had undergone surgical reduction at a single institution in the period between January 2011 and June 2104. The patients consisted of 5 males and 3 females. Three had os odontoideum, 2 had basilar invagination, and the other 3 experienced atlantoaxial rotatory fixed dislocation (AARFD). They were all treated using transoral anterior release, reduction, and fusion with the TARP. Preoperative and postoperative CT scans and MR images were obtained. American Spinal Injury Association (ASIA) Impairment Scale grades were determined.

RESULTS

All symptoms were relieved in all 8 patients but to varying degrees. Intraoperative loose reduction and fixation of C1-2 were achieved in one stage. The 4 patients with preoperative neurological deficits were significantly improved after surgery, and their latest follow-ups indicated that their ASIA Impairment Scale grades had improved to E. Postoperative pneumonia occurred in 1 patient but was under complete control after anti-infective therapy and fiber optic-guided sputum suction.

CONCLUSIONS

One-stage transoral anterior release, reduction, and fixation is an effective, reliable, and safe means of treating pediatric IAAD. The midterm clinical results are satisfactory, with the technique eliminating the need for interval traction and/or second-stage posterior instrumentation and fusion.

Sagittal Atlantoaxial Joint Inclination and Reduction Index Values for Diagnosis and Treatment of Irreducible Atlantoaxial Dislocation

BACKGROUND

Irreducible atlantoaxial dislocation (IAAD) is a disorder of atlantoaxial joint instability with various causes. The diagnostic criteria for IAAD are variable. The diagnosis of IAAD is mainly based on preoperative and intraoperative traction results, as well as the physician's experience, with no relatively uniform guidelines for the selection of treatment. This study evaluates sagittal atlantoaxial joint inclination (SAAJI) and reduction index (RI) values for diagnosis and treatment of IAAD.

MATERIALS AND METHODS

24 IAAD patients treated in our hospital from January 2008 to July 2014 were retrospectively analysed. Patients included were 13 males and 11 females, with a mean age of 43 years. The various causes for IAAD were atlantoaxial transverse ligament rupture (n=3), old dens fracture (n=15), occipitalization of the atlas (n=6). The patients were divided into two groups. group A underwent anterior release with posterior reduction and fixation; Group B underwent posterior reduction and fixation; 12 healthy individuals served as controls. SAAJI and atlas-dens interval (ADI) values before and after traction were measured, and RI was calculated. Imaging data were analyzed.

RESULTS

The mean SAAJI values were as follows: left, 5.6 ± 1.9° and right, 5.1 ± 2.1° in the control group; right, 39.5 ± 6.0° and left, 38.8 ± 5.8° in Group A; and right, 23.1 ± 7.0° and left, 23.9 ± 6.1° in Group B. There was no significant difference in the SAAJI values of the three groups (P < 0.05). The mean RIs in Groups A and B were 17.6 ± 9.3% and 34.4 ± 5.2%, respectively, and the difference was statistically significant (P < 0.05). There were obvious negative correlations between the SAAJI and RI values in Groups A and B.

CONCLUSIONS

SAAJI and RI can be used as important imaging indicators to determine the reversibility of IAAD. If the RI value is >27.9% and SAAJI value is <32.5°, reduction and fixation can be achieved by the posterior approach alone; otherwise, a combination of anterior and posterior approaches would be necessary.

Atlantoaxial Joint Distraction for the Treatment of Basilar Invagination: Clinical Outcomes and Radiographic Evaluation

OBJECTIVE

To investigate the causes of partial remission in patients with basilar invagination (BI) and irreducible atlantoaxial dislocation (IAAD) treated with transoral atlantoaxial reduction plate (TARP) without odontoidectomy and quantify the distance of odontoid descent.

METHODS

Between August 2010 and July 2012, 22 consecutive patients with BI with IAAD who underwent TARP surgery were reviewed. The preoperative and postoperative radiographic parameters were evaluated. Follow-up data and the symptom treatment interval (STI), defined as the interval between the onset of symptoms and surgical treatment, were assessed. Neurological function was evaluated as neurologic improvement, defined as ([Postoperative Japanese Orthopedic Association (JOA) score] - [Preoperative JOA score])/(17 - [Preoperative JOA score]). The patients were assigned to group A (<50%) or group B (≥50%) based on their level of neurologic improvement.

RESULTS

All 22 patients improved clinically to varying degrees. The mean preoperative STI was 105.6 ± 67.6 months for group A and 45.3 ± 46.7 months for group B (P < 0.05). There were no significant between-group differences in follow-up (P > 0.05) or with respect to radiographic parameters (P > 0.05). Persistent brainstem compression was observed in 1 patient, whose symptoms were not adequately relieved after revision surgery (transoral odontoidectomy and posterior decompression and fusion). No fixation failure was observed.

CONCLUSIONS

Descent of the odontoid process is useful for treating basilar invagination. TARP surgery without odontoidectomy may pull the dens caudally and ventrally to achieve sufficient decompression of the spinal cord. Neurologic improvement may be associated with STI.

Treatment of Basilar Invagination With Klippel-Feil Syndrome: Atlantoaxial Joint Distraction and Fixation With Transoral Atlantoaxial Reduction Plate

BACKGROUND

Klippel-Feil syndrome (KFS) is characterized by congenital vertebral fusion of the cervical spine and a wide spectrum of associated anomalies. In patients with KFS with basilar invagination (BI), compression of the brainstem and upper cervical cord results in neurological deficits, and decompression and occipitocervical reconstruction are required. The highly varied anatomy of KFS makes a posterior occipitocervical fixation strategy challenging. For these patients, the transoral atlantoaxial reduction plate (TARP) operation is an optimal option to perform a direct anterior fixation to achieve stabilization.

OBJECTIVE

To evaluate the effectiveness of TARP internal fixation for the treatment of BI with KFS.

METHODS

Ten consecutive patients with BI and KFS who underwent TARP reduction and fixation from 2010 to 2012 were reviewed. Clinical assessment and image measurements were performed preoperatively and at the most recent follow-up. Nine patients (9/10) were followed for an average of 31.44 months.

RESULTS

Symptoms were alleviated in 9 of 9 patients (100.00%). The odontoid process was ideally corrected with the TARP system. The mean clivus canal angle improved from 124° preoperatively to 152° postoperatively. The average preoperative and postoperative Japanese Orthopedic Association scores were 10.56 (n = 9) and 14.67 (n = 9), respectively, indicating 63.82% improvement. There was bony bridge catenation on the computed tomography scans and no evidence of hardware failure at 6 months.

CONCLUSION

The TARP operation is effective and safe for treating patients with BI with KFS. The midterm clinical results were satisfactory.

A unique procedure of joined transoral and retropharyngeal high cervical approach (JTRC) without mandibulectomy for treating upper cervical neoplasm involving both C2 and C3

PURPOSE

To investigate a unique procedure of joined transoral and retropharyngeal high cervical approach (JTRC) without mandibulectomy for treating upper cervical neoplasm involving both C2 and C3.

METHOD

A 23-year-old male patient had neoplasma involving C2 and C3 that caused pathologic fracture of C2 and bony destruction of C3. The neoplasm excision and cervical spine reconstruction were performed through JTRC approach without splitting up the mandible. In this approach, there were two surgery windows that could be applied in turns by closing or opening the mouth to gain an ideal exposure. By rotating the mandible, we could gain maximized exposure for either surgery windows. In addition, there was an overlay zone between transoral approach and high cervical retropharyngeal approach that could eliminate the blind area behind the mandible.

RESULTS

All the procedures were successfully performed; the surgical incisions healed without infection. By operating alternatively between the two surgery windows, we have successfully performed neoplasm excision and cervical spine reconstruction involving both C2 and C3. Pathologic results showed metastatic renal cell cancer to the resected cervical tumor and confirmed the patient's diagnosis of tuberous sclerosis (Bourneville disease). A 3-month postoperative cervical spine radiography and CT scan demonstrated a favorable placement of the bone implant as well as a favorable instrumentation.

CONCLUSION

The JTRC approach could provide good surgical exposure for treating disorders involving both upper and lower cervical spine without splitting up the mandible.

Surgical Outcome and Prognostic Analysis of Transoral Atlantoaxial Reduction Plate System for Basilar Invagination: A Voxel-Based Morphometry Study

BACKGROUND

The use of a transoral atlantoaxial reduction plate (TARP) system is an effective surgical approach for the treatment of basilar invagination. With the aim of improving the therapeutic efficacy of the TARP operation, we conducted a voxel-based morphometric study to quantitatively investigate the descent of the odontoid process and craniocervical volume changes.

METHODS

We enrolled 20 patients with basilar invagination who underwent a TARP procedure. Craniocervical computed tomography (CT) scanning and a 3-dimensional (3-D) reconstruction of the craniocervical junction were performed. Craniocervical volumes and odontoid process descent distances were measured preoperatively and postoperatively. Individual neurological function was evaluated according to the Japanese Orthopaedic Association (JOA) scoring system for cervical disorders. Pearson correlation analysis was applied for statistical testing.

RESULTS

Surgical efficacy (the JOA-score improvement rate) was significantly associated with the craniocervical volume improvement rate, the odontoid descent distance, and the absolute craniocervical volume changes (p < 0.01 for all), with correlation coefficients (r) of 0.83, 0.80, and 0.61, respectively. No significant correlation was noted between surgical efficacy and age, symptom duration, preoperative neurological function, odontoid process displacement, or change in clivus-odontoid angle (p > 0.05). The craniocervical volume improvement rate was significantly associated with the odontoid descent distance (r = 0.8; p < 0.01), but it was not associated with the odontoid displacement or the change in the clivus-odontoid angle (p > 0.05).

CONCLUSIONS

We found that the odontoid descent distance predicted the craniocervical volume improvement rate following TARP procedures in patients with basilar invagination, and we believe that both can serve as predictors of surgical efficacy. We believe that planning the odontoid descent distance preoperatively may help to improve the efficacy of TARP operations.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Selection of surgical procedures for basilar invagination with atlantoaxial dislocation

BACKGROUND CONTEXT

Basilar invagination (BI) is a malformation of craniovertebral junction. However, surgical procedures on BI with atlantoaxial dislocation (AAD) remain controversial.

PURPOSE

This research aimed to investigate the selection of surgical procedures and its significance in the surgical treatment of patients with BI and AAD.

STUDY DESIGN

This was a retrospective study.

PATIENT SAMPLE

This study enrolled 33 patients who were diagnosed with BI and AAD and were followed up for at least 6 months.

OUTCOME MEASURE

All of the patients were assessed for neurologic recovery observation in terms of Japanese Orthopaedic Association scores and Odom criteria. X-ray, magnetic resonance imaging, or computed tomography scanning was used to determine reduction, compression, bone graft, and internal fixation before and after operation.

METHODS

Thirty-three patients who suffered from BI with AAD were treated in our department from July 2000 to October 2014. Preoperatively, the patients were divided into two types on the basis of whether dislocation was reduced after anesthesia and traction were performed: reducible dislocation (Type A) and irreducible dislocation (Type B). Reducible dislocation was further divided into two subtypes: full reducible dislocation (Type A1) and partial reducible dislocation (Type A2). Type A1 patients were treated with direct posterior fixation and fusion after traction and reduction. Type A2 patients received posterior atlantoaxial release, fixation, and fusion under traction. Type B patients underwent transoral atlantoaxial release, posterior fixation, and fusion.

RESULTS

There were 5 Type A1 patients, 10 Type A2 patients, and 18 Type B patients treated in accordance with the proposed scheme. Postoperatively, sufficient reduction and decompression were achieved for all cases. Two Type B patients died. Other patients were followed up from 6 months to 42 months (average=16.6 months); follow-up results showed sufficient decompression, effective fixation and fusion, and no reduction loss. The Japanese Orthopaedic Association Score increased from preoperative 4-12 (average, 7.8) to postoperative 10-17 (average, 14.3), and neurologic recovery was satisfactory.

CONCLUSIONS

Under traction, simple posterior fixation and fusion were effective for Type A patients suffering from BI with AAD; anterior atlantoaxial release and posterior fixation and fusion were effective for Type B patients with BI and AAD.

An 11-Year Review of the TARP Procedure in the Treatment of Atlantoaxial Dislocation

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of the study was to introduce the surgical techniques and evaluate the clinical outcomes of transoral atlantoaxial reduction plate (TARP) for the treatment of atlantoaxial dislocation.

SUMMARY OF BACKGROUND DATA

Researchers have reported on transoral plate internal fixation for the treatment of irreducible atlantoaxial dislocation (IAAD) without long-term follow-up and detailed clinical experience.

METHODS

The clinical records of 388 patients with atlantoaxial dislocation (IAAD, 340 cases; fixed atlantoaxial dislocation [FAAD], 48 cases) who received the TARP procedure from April 2003 to September 2014 were retrospectively reviewed. They were treated separately with TARP-I or TARP-II (82 cases), TARP-III (248 cases), or TARP-IV (58 cases). X-ray and magnetic resonance imaging were used to evaluate the efficacy of reduction and the degree of decompression, respectively. The long-term clinical outcome was evaluated by Japanese Orthopaedic Association scoring and the Symon and Lavender standard.

RESULTS

Immediate reduction was achieved for all the patients with IAAD (340/340), whereas anatomical reduction was achieved for 98.2% of patients (334/340). Anatomical reduction was achieved in 87.5% of patients with FAAD (42/48). The average degree of spinal cord decompression ranged from 75% to 100% with an average of 88.4%. The clinical data of 106 patients were evaluated in the latest follow-up (12-108 mo, average 60.5 mo). The average spinal cord improvement rate by Japanese Orthopaedic Association scoring was 62.1%. According to the Symon and Lavender standard, there were 85 cases rated as markedly effective, 104 cases as effective, and 2 cases as noneffective. The overall markedly effective rate was 80% and the effective rate was 98%.

CONCLUSION

The TARP procedure showed good anterior atlantoaxial release, reduction, decompression, and internal fixation for patients with IAAD and FAAD through a single anterior approach. It has the advantages of three-dimensional immediate atlantoaxial reduction and sufficient decompression.

LEVEL OF EVIDENCE

3.

Minimally Invasive Surgical Approach for Odontoid Lesions: A Technical Description in a Case of High Cervical Osteomyelitis and Abscess

BACKGROUND

Cervical approaches to the dens are limited by the presence of several structures, including the spinal cord, vertebral arteries, C1 articular pillars, and C2 nerves. Surgical approaches to access the high anterior cervical spine classically encompass the extended anterior retropharyngeal route, transoral route, and extreme lateral route, each of which has its own pattern of morbidity or complications. Percutaneous procedures to drain infections in this area have a limited yield. Osteomyelitis of the dens is a rare but serious condition that is associated with significant mortality. Patients with cervical osteomyelitis and epidural abscess are likely to have significant coexistent medical comorbidities and are often poor candidates for extensive surgical procedures. A minimally invasive approach that gives access to the entire odontoid process would allow for more aggressive treatments and potentially even a complete odontoidectomy without resection of the C1 anterior arch.

CASE DESCRIPTION

We describe a minimally invasive approach to drainage and debridement of an atlantoaxial epidural abscess and osteomyelitis. Using minimally invasive techniques from a posterolateral trajectory in a cadaveric specimen, we were able to safely access the anterior epidural space, odontoid, and retropharynx. We then performed this approach in our patient who was unable to tolerate a large surgical procedure.

CONCLUSIONS

We developed, tested, and then applied a minimally invasive approach that combined tubular retractors with positioning of the head and neck to optimize the exposure in a patient with a complex abscess that involved the ventral epidural space, odontoid process, and retropharyngeal space. The abscesses were successfully drained along with local tissue debridement without complication. A posterolateral minimally invasive approach is a safe alternative in patients with an atlantoaxial epidural abscess, odontoid osteomyelitis, or retropharyngeal abscess with significant medical comorbidities who are unlikely to tolerate a more extensive surgery. It can also be used for resections of lesions of an oncologic nature and could even be used to resect pannus or os odontoideum, without necessitating an anterior approach or resection even of the C1 arch.

Biomechanical Comparison of Modified TARP Technique Versus Modified Goel Technique for the Treatment of Basilar Invagination: A Finite Element Analysis

STUDY DESIGN

A finite element analysis.

OBJECTIVE

The aim of this study was to determine the biomechanical differences between atlantoaxial fusion cage combined with transoral atlantoaxial reduction plate fixation (TARP + Cage, modified TARP technique) and that combined with C1 lateral mass screw and C2 pedicle screw fixation (C1LS + C2PS + Cage, modified Goel technique) in the treatment of basilar invagination (BI) by finite element analysis.

SUMMARY OF BACKGROUND DATA

Clinical studies have shown that transoral anterior atlantoaxial release followed by TARP fixation can achieve reduction, decompression, fixation, and fusion of C1-C2 through a transoral-only approach. Although cage has been used to reduce the BI through posterior approach, there are no studies referred to the cage combined with TARP for C1-C2 fusion.

METHODS

A finite element model was used to investigate and compare the stability between TARP + Cage fixation and C1LS + C2PS + Cage fixation in the treatment of BI. Vertical load of 40  N was applied on the C0, to simulate head weight, and 1.5  Nm torque was applied to the C0 to simulate flexion, extension, lateral bending, and rotation.

RESULTS

In comparison with the C1LS + C2PS + Cage model, the TARP + Cage model reduced the ROM by 44.7%, 30.0%, and 10.5% in extension, lateral bending, and axial rotation, while the TARP + Cage model increased the ROM by 30.0% in flexion, and the TARP + Cage model also led to lower screw stress in all motions with one exception (anterior C2PS stress in extension).

CONCLUSION

Our results indicate that the TARP + Cage fixation may offer higher stability to C1LS + C2PS + Cage in extension, lateral bending, and axial rotation but lower stability in flexion. Compared with modified Goel technique, the modified TARP technique not only has the capability of transferring the load and distributing the stress but also can provide neural decompression, stabilization and fusion, and restore C1-C2 normal fusion angle.

LEVEL OF EVIDENCE

N/A.

Modified technique of transoral release in one-stage anterior release and posterior reduction for irreducible atlantoaxial dislocation

BACKGROUND

One-stage anterior release and posterior reduction is one of the most effective methods for irreducible atlantoaxial dislocation. However, the criteria of appropriate tissue release for successful posterior reduction is yet to be confirmed. Hence, an assistant technique using the transoral approach to verify satisfactory release is required. To evaluate the efficacy of the modified technique of transoral release for irreducible atlantoaxial dislocation (IAAD) with patients underwent one-stage anterior release and posterior reduction.

METHODS

Between January 2009 and June 2014, 23 consecutive patients diagnosed with IAAD free from bony union between the C1-C2 facet joints on reconstructive computed tomography scan underwent one-stage anterior release and posterior reduction after no response to 2 weeks of skull traction. During transoral release, an elevator was used as a lever repeatedly to confirm a 3-5 mm bilateral joint space between the lateral masses of the atlas and axis. The release was accomplished since a 3-5 mm joint space was achieved. After anterior release, posterior reduction and instrumented fusion were subsequently performed.

RESULTS

All patients were observed for an average of 18 (range 6-50) months. Nineteen of 23 patients achieved complete reduction while four had an incomplete reduction. Significant differences in pre- and postoperative JOA scores and cervicomedullary angle (CMA) were found. Twenty-one patients presenting with myelopathy had a JOA score of 12.9 at final follow-up, improved from 7.8 before surgery. The mean CMA improved to 143.5° postoperatively from 101.8° preoperatively. Bony fusion was confirmed in all cases under radiologic assessment during follow-up; there were no instrument failures.

CONCLUSION

The modified technique of transoral release provides appropriate criteria for anterior release, to achieve good posterior reduction without excessive tissue release or intraspinal manipulation, proving its value as an assistant technique in one-stage anterior release and posterior reduction for IAAD.

Biomechanical comparison of a novel transoral atlantoaxial anchored cage with established fixation technique - a finite element analysis

BACKGROUND

The transoral atlantoaxial reduction plate (TARP) fixation has been introduced to achieve reduction, decompression, fixation and fusion of C1-C2 through a transoral-only approach. However, it may also be associated with potential disadvantages, including dysphagia and load shielding of the bone graft. To prevent potential disadvantages related to TARP fixation, a novel transoral atlantoaxial fusion cage with integrated plate (Cage + Plate) device for stabilization of the C1-C2 segment is designed. The aims of the present study were to compare the biomechanical differences between Cage + Plate device and Cage + TARP device for the treatment of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD).

METHODS

A detailed, nonlinear finite element model (FEM) of the intact upper cervical spine had been developed and validated. Then a FEM of an unstable BI model treated with Cage + Plate fixation, was compared to that with Cage + TARP fixation. All models were subjected to vertical load with pure moments in flexion, extension, lateral bending and axial rotation. Range of motion (ROM) of C1-C2 segment and maximum von Mises Stress of the C2 endplate and bone graft were quantified for the two devices.

RESULTS

Both devices significantly reduced ROM compared with the intact state. In comparison with the Cage + Plate model, the Cage + TARP model reduced the ROM by 82.5 %, 46.2 %, 10.0 % and 74.3 % in flexion, extension, lateral bending, and axial rotation. The Cage + Plate model showed a higher increase stresses on C2 endplate and bone graft than the Cage + TARP model in all motions.

CONCLUSIONS

Our results indicate that the novel Cage + Plate device may provide lower biomechanical stability than the Cage + TARP device in flexion, extension, and axial rotation, however, it may reduce stress shielding of the bone graft for successful fusion and minimize the risk of postoperative dysphagia. Clinical trials are now required to validate the reproducibility and advantages of our findings using this anchored cage for the treatment of BI with IAAD.