Atlantoaxial intra-articular cage fusion by posterior intermuscular approach for treating reducible atlantoaxial dislocation: a technique note with case series

PURPOSE

To evaluate the clinical feasibility of atlantoaxial intra-articular cage (AIC) fusion via intermuscular approach for treating reducible atlantoaxial dislocation (AAD).

METHODS

An analysis was conducted on the data of 10 patients who underwent C1-C2 segmental fixation and AIC fusion for AAD by unilateral intermuscular approach and contralateral open approach. Outcome assessments included Japanese Orthopaedic Association score (JOA) and Visual Analog Scale Score for Neck Pain (VASSNP). The duration of surgical exposure, screw insertion and cage insertion, and postoperative drainage volume were also compared between two approaches. Bone fusion was evaluated through computed tomography (CT) reconstruction. Postoperative paravertebral tissue edema was evaluated by paravertebral tissue cross-sectional area (CSA) and signal intensity on T2 weighted sequence of magnetic resonance imaging (MRI) at 3 days postoperatively.

RESULTS

The intermuscular approach exhibited a longer exposure time but lower drainage postoperatively compared to the open approach (P < 0.05). After operation, JOA scores significant improved (P < 0.05), while VASSNP scores significantly decreased (P < 0.05). There was no significant difference in preoperative CSA between two approaches (P > 0.05). However, compared to the open approach, the intermuscular approach exhibited less CSA (P < 0.05) and lower T2 signal intensity on MRI postoperatively, indicating less invasive to the paravertebral tissues.

CONCLUSIONS

AIC fusion by intermuscular approach is an effective and safe technique in the treatment of reducible AAD. Intermuscular approach could reduce the postoperative drainage volume and the extent of paravertebral tissue edema compared to open approach.

Evaluation of the Anatomical Reference Point in Posterior Minimally Invasive Atlantoaxial Spine Surgery: A Cadaveric Anatomical Study

OBJECTIVE

Minimally invasive atlantoaxial surgery offers the benefits of reduced trauma and quicker recovery. Previous studies have focused on feasibility and technical aspects, but the lack of comprehensive safety information has limited its availability and widespread use. This study proposes to define the feasibility and range of surgical safety using the intersection of the greater occipital nerve and the inferior border of the inferior cephalic oblique as a reference point.

METHODS

Dissection was performed on 10 fresh cadavers to define the anatomical reference point as the intersection of the greater occipital nerve and the inferior border of the inferior cephalic oblique muscle. The study aimed to analyze the safety range of minimally invasive atlantoaxial fusion surgery by measuring the distance between the anatomical reference point and the transverse foramen of the axis, the distance between the anatomical reference point and the superior border of the posterior arch of the atlas, and the distance between the anatomical reference point and the spinal canal. Measurements were compared using Student's t test.

RESULTS

The point where the occipital greater nerve intersects with the inferior border of the inferior cephalic oblique muscle was defined as the anatomical marker for minimally invasive posterior atlantoaxial surgery. The distance between this anatomical marker and the transverse foramen of the axis was measured to be 9.32 ± 2.04 mm. Additionally, the distance to the superior border of the posterior arch of the atlas was found to be 21.29 ± 1.93 mm, and the distance to the spinal canal was measured to be 11.53 ± 2.18 mm. These measurement results can aid surgeons in protecting the vertebral artery and dura mater during minimally invasive posterior atlantoaxial surgery.

CONCLUSIONS

The intersection of the greater occipital nerve with the inferior border of the inferior cephalic oblique muscle is a safe and reliable anatomical landmark in minimally invasive posterior atlantoaxial surgery.

Posterior atlantoaxial internal fixation using Harms technique assisted by 3D-based navigation robot for treatment of atlantoaxial instability

Background

To evaluate the accuracy of screw placement using the TiRobot surgical robot in the Harms procedure and to assess the clinical outcomes of this technique.

Methods

This retrospective study included 21 patients with atlantoaxial instability treated by posterior atlantoaxial internal fixation (Harms procedure) using the TiRobot surgical robot between March 2016 and June 2021. The precision of screw placement, perioperative parameters and clinical outcomes were recorded. Screw placement was assessed based on intraoperative guiding pin accuracy measurements on intraoperative C-arm cone-beam computed tomography (CT) images using overlay technology and the incidence of screw encroachment identified on CT images.

Results

Among the 21 patients, the mean age was 44.8 years, and the causes of atlantoaxial instability were os odontoideum (n = 11), rheumatoid arthritis (n = 2), unknown pathogenesis (n = 3), and type II odontoid fracture (n = 5). A total of 82 screws were inserted with robotic assistance. From intraoperative guiding pin accuracy measurements, the average translational and angular deviations were 1.52 ± 0.35 mm (range 1.14–2.25 mm) and 2.25° ± 0.45° (range 1.73°–3.20º), respectively. Screw placement was graded as A for 80.5% of screws, B for 15.9%, and C for 3.7%. No complications related to screw misplacement were observed. After the 1-year follow-up, all patients with a neurological deficit experienced neurological improvement based on Nurick Myelopathy Scale scores, and all patients with preoperative neck pain reported improvement based on Visual Analog Scale scores.

Conclusions

Posterior atlantoaxial internal fixation using the Harms technique assisted by a 3D-based navigation robot is safe, accurate, and effective for treating atlantoaxial instability.

Percutaneous Posterior Cervical Pedicle Instrumentation (C1 to C7) With Navigation Guidance: Early Series of 27 Cases

STUDY DESIGN

This is a technique paper describing minimally invasive, navigated, percutaneous pedicle screw fixation of the cervical spine. In addition, we include a retrospective feasibility analysis of our initial experience with 27 patients undergoing this procedure.

OBJECTIVE

The purpose of this study is to describe the technique of MIS navigated percutaneous cervical pedicle screw instrumentation and to report our initial experience.

METHODS

This is a retrospective review of 27 patients undergoing MIS navigated percutaneous posterior cervical pedicle screw fixation at 2 institutions. We describe the technique and report the radiographic outcomes and all intraoperative and postoperative complications.

RESULTS

A total of 27 patients underwent MIS navigated percutaneous pedicle screw fixation. Indications included odontoid fracture, subaxial fracture dislocations and burst fracture, pathological fracture, and degenerative spondylosis. There were no nerve root or vascular injuries. There were no spinal cord injuries. Two screws required repositioning intraoperatively, and 1 patient required reoperation for symptomatic malpositioned screw.

CONCLUSIONS

MIS navigated percutaneous posterior pedicle screw fixation can be performed safely. These constructs are biomechanically superior with neurovascular complication rates comparable to traditional lateral mass screw technique. While the current indications for this technique are relatively limited, the evolution of MIS cervical decompression techniques as well as navigation and robotics will provide an expanded role for percutaneous cervical pedicle screw instrumentation.

Patient-rated outcome after atlantoaxial (C1-C2) fusion: more than a decade of evaluation of 2-year outcomes in 126 patients

INTRODUCTION

Various surgical techniques have been introduced for atlantoaxial (C1-C2) fusion, the most common being Magerl's (transarticular) or the Harms/Goel screw fixation. Common indications include degenerative osteoarthritis (OA), trauma or rheumatoid arthritis (RA). Only few, small studies have evaluated patient-reported outcomes after C1-C2 fusion. We investigated 2-year outcomes in a large series of consecutive patients undergoing isolated C1-C2 fusion.

METHODS

We analysed prospectively collected data (2005-2016) from our Spine outcomes database, collected within the framework of EUROSPINE's Spine Tango Registry. It included 126 patients (34 (27%) men, 92 (73%) women; mean (SD) age 67 ± 19 y) who had undergone first-time isolated C1-C2 fusion (61% Magerl, 39% Harms(-Goel)) at least 2 years ago for OA (83 (66%)), RA (20 (16%)), fracture (15 (12%)) or other (8 (6%)). Patients completed the multidimensional Core Outcome Measures Index (COMI; 0-10) and various single item outcomes.

RESULTS

Questionnaires were returned by 118/126 (94%) patients, 2 years post-operative. Mean COMI scores showed a significant reduction from baseline: 6.9 ± 2.4 to 2.7 ± 2.5 (p < 0.0001). Overall, 75% patients achieved the MCIC of ≥ 2.2 points reduction in COMI and 88% reported a good global outcome. 91% patients were satisfied/very satisfied with their care. Self-reported complications were declared by 16% patients and further surgery at the same segment, by 2.5%.

CONCLUSION

In this large series with almost complete follow-up, C1-C2 fusion showed extremely good results. Despite the complexity of the intervention, outcomes surpassed those typically reported for simple procedures such as ACDF and lumbar discectomy, suggesting reservations about the procedure should perhaps be reviewed.

Minimally invasive robotic cervicothoracic fusion: a case report and review of literature

Minimally invasive surgery (MIS) of the posterior cervical spine with robotic assistance has recently emerged to treat degenerative disc disease. Robotic arms and 3D neuronavigation with preoperatively planned placement are used to achieve real-time intraoperative guidance, reducing screw malposition through increased accuracy and stability. This results in decreased blood loss, postoperative pain, and quicker recovery time compared to other techniques. We aim to demonstrate a novel technical approach to posterior cervical spine fusion using robotic assistance and discuss its advantages. In a patient with right hand weakness and a right paracentral disc herniation of the cervicothoracic spine, we performed a MIS percutaneous and robotically assisted posterior spinal fusion at C7-T2, with complete C7-T1 and T1-2 right-sided facetectomies and also a T1-T2 discectomy. Preoperative software planning and a robotic platform attachment configuration was used. There was immediate postoperative improvement in upper extremity strength and the patient was discharged without complications. Postoperative imaging confirmed accurate hardware placement, and follow-up at both 3- and 4-month confirmed improved upper extremity strength with sensation intact throughout. MIS robotic posterior cervicothoracic fusion can effectively be used to improve patient outcomes. Further implementation of robotic assistance during cervical fusion in larger studies is needed to further evaluate its effectiveness.

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.

Percutaneous, Navigated Minimally Invasive Posterior Cervical Pedicle Screw Fixation

BACKGROUND

Cervical pedicle screws provide significant biomechanical advantage but can be technically challenging and associated with morbid exposure. Improvements in intraoperative navigation guidance and instrumentation have made feasible this biomechanically robust, but technically challenging procedure. We present our initial experience with minimally invasive (MIS) percutaneous pedicle screw fixation in the cervical atlantoaxial and subaxial spine.

METHODS

A retrospective review was performed on 27 cases that involved a novel MIS percutaneous cervical pedicle screw technique. Small lateral skin incisions were made bilaterally on the neck using intraoperative navigation guidance. Subsequently, navigated, percutaneous screws were placed using the Proficient Minimally Invasive System (PROMIS; Spine Wave, Shelton, CT). Computed tomography (CT)-guided navigation was used for cervical pedicle screw placement with subsequent placement of percutaneous rods.

RESULTS

Indications for surgery included type II odontoid fractures, subaxial fracture dislocations and burst fracture, metastatic pathological burst fracture, and degenerative spondylosis with stenosis. There were 15 men and 12 women, with an average age 63.5 years. Follow-up ranged from 3 to 24 months (average = 16.7 months). One screw was revised intraoperatively. Two patients (7.7%) required reoperation, 1 patient required repositioning of a C5 pedicle screw, and 1 suffered a C7 body fracture. No nerve root injury, spinal cord injury, or vertebral artery injuries were reported.

CONCLUSIONS

Percutaneous cervical pedicle screw fixation is a feasible and safe technique when performed with CT-guided intraoperative navigation techniques. Cervical pedicle screw fixation provides a biomechanically superior construct in comparison with a lateral mass technique. In addition, the lack of paraspinal muscle disruption preserves important stabilizers of the posterior ligamentous complex and may reduce wound-healing issues in high-risk cases (eg, trauma patients). Although the current role for percutaneous instrumentation is relatively narrow, the advancement of MIS posterior cervical techniques may provide expanded opportunities in the future.

[Minimally invasive techniques for traumatic injuries of the cervical spine]

Nowadays, although minimally invasive procedures are the standard for the treatment of thoracolumbar spinal injuries, these techniques are not yet established for the cervical spine. This is due to anatomical and technical reasons and also due to the fact that the classical anterior decompression and fusion procedure already fulfils the criteria of minimally invasiveness and is suitable for the vast majority of injuries. The existing literature consists mainly of case reports and small comparative cohort studies, the results of which are presented. There is a minimally invasive variant for nearly all open procedures, mainly in the upper cervical spine but also in the lower cervical spine. The further development of these promising techniques is still pending.

Change in rates of primary atlantoaxial spinal fusion surgeries in the United States (1993-2015)

OBJECTIVE

The objective of this study was to investigate revision burden and associated demographic and economic data for atlantoaxial (AA) fusion procedures in the US.

METHODS

Patient data from the National Inpatient Sample (NIS) database for primary AA fusion were obtained from 1993 to 2015, and for revision AA fusion from 2006 to 2014 using ICD-9 procedure codes. Data from 2006 to 2014 were used in comparisons between primary and revision surgeries. National procedure rates, hospital costs/charges, length of stay (LOS), routine discharge, and mortality rates were investigated.

RESULTS

Between 1993 and 2014, 52,011 patients underwent primary AA fusion. Over this period, there was a 111% increase in annual number of primary surgeries performed. An estimated 1372 patients underwent revision AA fusion between 2006 and 2014, and over this time period there was a 6% decrease in the number of revisions performed annually. The 65-84 year-old age group increased as a proportion of primary AA fusions in the US from 35.9% of all AA fusions in 1997 to 44.2% in 2015, an increase of 23%. The mean hospital cost for primary AA surgery increased 32% between 2006 and 2015, while the mean cost for revision AA surgery increased by 35% between 2006 and 2014. Between 2006 and 2014, the mean hospital charge for primary AA surgery increased by 67%; the mean charge for revision surgery over that same period increased by 57%. Between 2006 and 2014, the mean age for primary AA fusions was 60 years, while the mean age for revision AA fusions was 52 years. The mean LOS for both procedures decreased over the study period, with primary AA fusion decreasing by 31% and revision AA fusion decreasing by 24%. Revision burden decreased by 21% between 2006 and 2014 (mean 4.9%, range 3.2%-6.4%). The inpatient mortality rate for primary AA surgery decreased from 5.3% in 1993 to 2.2% in 2014.

CONCLUSIONS

The number of primary AA fusions between 2006 and 2014 increased 22%, while the number of revision procedures has decreased 6% over the same period. The revision burden decreased by 21%. The inpatient mortality rate decreased 62% (1993-2014) to 2.2%. The increased primary fusion rate, decreased revision burden, and decreased inpatient mortality determined in this study may suggest an improvement in the safety and success of primary AA fusion.

The use of minimally invasive surgery in spine trauma: a review of concepts

Traumatic injuries to the spine can be common in the setting of blunt trauma and delayed diagnosis can have a deleterious effect on patients' health. The goals of treatment in managing spine trauma are prevention of neurological injury, providing stability to the spine, and correcting post-traumatic deformity. Minimally invasive spine surgery (MISS) techniques are an alternative to open spine surgery for treatment of spine fractures. MISS is also a viable treatment in the setting of damage control orthopedics, when patients with multiple traumatic injuries may be unable to tolerate a traditional open approach. MISS techniques have been used in the treatment of unstable fractures with or without spinal cord injury, flexion and extension-distraction injuries, and unstable sacral fractures. Traditional open surgeries have been associated with increased blood loss, longer operative times, and a higher risk for surgical site infection (SSI). MISS techniques have the potential to reduce open approach-associated morbidity, and improve postoperative care and rehabilitation. MISS techniques for spine trauma are an indispensable option in the treatment armamentarium of spine surgeons.

Reoperation for Symptomatic Nonunions in Atlantoaxial (C1-C2) Fusions with and without Bone Morphogenetic Protein: A Cohort of 108 Patients with >2 Years Follow-Up

OBJECTIVE

To determine if there is a difference in reoperation rates for symptomatic nonunions in atlantoaxial (C1-C2) fusions with or without bone morphogenetic protein (BMP) using data from a national spine registry and to analyze the different types of bone grafts used in the non-BMP group.

METHODS

Data from the Kaiser Permanente spine registry were used to identify patients with C1-C2 fusions with >2 years follow-up. Patient characteristics, diagnosis, operative times, length of stay, and reoperations were extracted from the registry. The data set was divided into patients with and without BMP. Further analysis was made of the different types of non-BMP grafts as well as the instrumentation used.

RESULTS

In our cohort, we found 58 patients (53.7%) with BMP and 50 patients (46.3%) without with an average follow-up time of 5 years (interquartile range, 2.04-8.49). The BMP versus non-BMP groups differed in admitting diagnosis, operative times, length of stay, and follow-up times. There were no reoperations for symptomatic nonunions in both groups. The non-BMP group included iliac crest graft (with or without allograft [+/-] allograft); lamina (+/- allograft); and allograft alone.

CONCLUSIONS

Using one of the largest retrospective studies on C1-C2 fusions with and without BMP, we found no difference in reoperation rates for symptomatic nonunions. For the non-BMP group, we found that lamina (+/- allograft) or allograft alone may also be just as effective as iliac crest graft (+/- allograft) in having no reoperations for symptomatic nonunions.

Minimally invasive spinal surgery for trauma: a narrative review

Over the past decade there has been a revolution in availability for minimally invasive techniques for the fixation of spinal fractures. In this narrative review we aimed to take a comprehensive look at these developments and their results from the Atlas to the Sacrum establishing the current evidence base for percutaneous fixation at each level of the spine.

Posterior Bilateral Intermuscular Approach for Upper Cervical Spine Injuries

OBJECTIVE

To investigate a novel intermuscular surgical approach for posterior upper cervical spine fixation.

METHODS

Twenty-three healthy volunteers underwent magnetic resonance imaging. By using the magnetic resonance imaging scans in transverse view at the level of lower edge of atlas, the distances from the posterior midline to lateral margin of trapezius, to the medial margin of splenius capitis, and to middle line of semispinalis capitis were recorded. The angle between posterior middle line and the line crossing the lateral margin of trapezius and middle point of ipsilateral pedicles. From October 2009 to May 2013, 12 patients with upper cervical spine injuries were operated via the bilateral intermuscular approach. The time required for surgery, blood loss, and pre- and postoperative visual analogue scale scores were analyzed.

RESULTS

The average distance of 0-T was 39.2 ± 7.5 mm, the angle between the approach and posterior middle line was 33.2 ± 8.4°. The surgical time was 78.3 ± 22.5 minutes (45-140 minutes), and the mean intraoperative blood loss was 87.5 ± 44.2 mL (30-200 mL). Preoperative and postoperative visual analogue scale scores were 6.4 ± 0.8 and 1.8 ± 0.7, respectively. The average follow-up time was 19.7 ± 11.5 months (9-48 months).

CONCLUSIONS

The posterior bilateral intermuscular approach for upper cervical spine injuries is a valid alternative for Hangmans' fractures type I, type II, and type Ia according to Levine and Edwards classification as well as atlantoaxial subluxation caused by upper cervical spine trauma.

Minimally invasive atlantoaxial fusion: cadaveric study and report of 5 clinical cases

OBJECTIVE

Minimally invasive techniques are being increasingly used to treat disorders of the cervical spine. They have a potential to reduce the postoperative neck discomfort subsequent to extensive muscle dissection associated with conventional atlantoaxial fusion procedures. The aim of this paper was to elaborate on the technique and results of minimally invasive atlantoaxial fusion.

MATERIALS

Minimally invasive atlantoaxial fusion was done initially in 4 fresh-frozen cadavers and subsequently in 5 clinical cases. Clinical cases included patients with reducible atlantoaxial instability and undisplaced or minimally displaced odontoid fractures. The surgical technique is illustrated in detail.

RESULTS

Among the cadaveric specimens, all C-1 lateral mass screws were in the correct position and 2 of the 8 C-2 screws had a vertebral canal breach. Among clinical cases, all C-1 lateral mass screws were in the correct position. Only one C-2 screw had a Grade 2 vertebral canal breach, which was clinically insignificant. None of the patients experienced neurological worsening or implant-related complications at follow-up. Evidence of rib graft fusion or C1–2 joint fusion was successfully demonstrated in 4 cases, and flexion-extension radiographs done at follow-up did not show mobility in any case.

CONCLUSIONS

Minimally invasive atlantoaxial fusion is a safe and effective alternative to the conventional approach in selected cases. Larger series with direct comparison to the conventional approach will be required to demonstrate clinical benefit presumed to be associated with a minimally invasive approach.

C1-C2 stabilization by Harms arthrodesis: indications, technique, complications and outcomes in a prospective 26-case series

INTRODUCTION

C1-C2 arthrodesis is a surgical challenge due to the proximity of neurovascular structures (vertebral arteries and spinal cord) and the wide range of motion of the joint, hampering bone fusion. A variety of techniques have been successively recommended to reduce anatomic risk and improve results in terms of biomechanical stability and fusion rates. Recently, Harms described a new technique using polyaxial screws in the C1 lateral masses and C2 pedicles.

MATERIAL AND METHOD

The present study reports our experience in a consecutive series of 26 patients operated on by C1-C2 arthrodesis using the Goel and Harms technique, and details technical aspects step by step. Routine systematic immediate postoperative CT and 6-month CT controlled screw positioning and assessed fusion. Follow-up was at least 1 year, except in 2 cases (10 months).

RESULTS

Twenty-six patients with a mean age of 57 years were included. Indications comprised: C2 non-union (n=11), C1-C2 fracture and/or dislocation (n=11), inflammatory pathology (n=2) and tumoral pathology (n=2). The results showed the technique to be reliable (no neurovascular complications and 85% of screws with perfect positioning) and an excellent rate of fusion (100% at 6 months).

CONCLUSION

Anatomic and biomechanical considerations, combined with the present clinical and radiological outcomes, indicate that Goel and Harms fusion is to be considered the first-line attitude of choice for posterior C1-C2 arthrodesis.

LEVEL OF EVIDENCE

Level IV prospective study.