Harms C1-C2 instrumentation technique: anatomo-surgical guide

Study on articular surface morphology of atlantoaxial lateral mass based on differential manifold

OBJECTIVES

To propose a surface reconstruction algorithm based on a differential manifold (a space with local Euclidean space properties), which can be used for processing of clinical images and for modeling of the atlantoaxial joint. To describe the ideal anatomy of the lateral atlantoaxial articular surface by measuring the anatomical data.

METHODS

Computed tomography data of 80 healthy subjects who underwent cervical spine examinations at our institution were collected between October 2019 and June 2022, including 46 males and 34 females, aged 37.8 ± 5.1 years (28-59 years). A differential manifold surface reconstruction algorithm was used to generate the model based on DICOM data derived by Vision PACS system. The lateral mass articular surface was measured and compared in terms of its sagittal diameter, transverse diameter, articular surface area, articular curvature and joint space height.

RESULTS

There was no statistically significant difference between left and right sides of the measured data in normal adults (P > 0.05). The atlantoaxial articular surface sagittal diameter length was (15.83 ± 1.85) and (16.22 ± 1.57) mm on average, respectively. The transverse diameter length of the articular surface was (16.29 ± 2.16) and (16.49 ± 1.84) mm. The lateral articular surface area was (166.53 ± 7.69) and (174.48 ± 6.73) mm2 and the curvature was (164.03 ± 5.27) and (153.23 ± 9.03)°, respectively. The joint space height was 3.05 ± 0.11mm, respectively. There is an irregular articular space in the lateral mass of atlantoaxial, and both upper and lower surfaces of the articular space are concave. A sagittal plane view shows that the inferior articular surface of the atlas is mainly concave above; however, the superior articular surface of the axis is mainly convex above. In the coronal plane, the inferior articular surface of the atlas is mostly concave above, with most concave vertices located in the medial region, and the superior articular surface of the axis is mainly concave below, with most convex vertices located centrally and laterally.

CONCLUSION

A differential manifold algorithm can effectively process atlantoaxial imaging data, fit and control mesh topology, and reconstruct curved surfaces to meet clinical measurement applications with high accuracy and efficiency; the articular surface of the lateral mass of atlantoaxial mass in normal adults has relatively constant sagittal diameter, transverse diameter and area. The distance difference between joint spaces is small, but the shape difference of articular surfaces differs greatly.

Two-Stage Approach for Unstable Pediatric Craniocervical Junction Anomalies with a Halo Vest and Delayed Occipitocervical Fusion: Technical Note, Case Series, and Literature Review

OBJECTIVE

Malformations in the craniocervical junction (CCJ) are rare in the pediatric population but often need surgical treatment. We present a pediatric case series of patients treated with a 2-stage surgical approach with a halo vest and occipitocervical fusion and review complications and outcomes.

METHODS

A retrospective analysis of a single-center case series was performed. Pediatric patients affected by congenital craniocervical junction anomalies and treated with a 2-stage approach were included. A halo vest was implanted in the first surgery, and ambulatory progressive reduction was performed. When a favorable anatomic situation was observed, arthrodesis was performed. Safety analysis was undertaken by analyzing the incidence of complications in both procedures. Effectivity analysis was carried out analyzing radiologic and clinical outcome (Goel grade and modified Japanese Orthopaedic Association score). Student t test was used for statistical analysis.

RESULTS

Sixteen cases were included. Mean age of patients was 9.38 years. Safety analysis showed 2 halo loosenings, 1 pin infection, 2 wound infections, 1 cerebrospinal fluid leak, and 2 delayed broken rods. No major complications were observed. Radiologic analysis showed an improvement in the tip of the odontoid process to the McRae line distance (from -3.26 mm to -6.16 mm), atlantodental interval (from 3.05 mm to 1.88 mm), clival-canal angle (from 134.61° to 144.38°), and cervical kyphosis (from 6.39° to 1.54°). Clinical analysis also showed improvement in mean Goel grade (from 1.75 to 1.44) and modified Japanese Orthopaedic Association score (from 15.12 to 16.41).

CONCLUSIONS

The 2-stage approach was a suitable and effective treatment for craniocervical junction anomalies in pediatric patients.

Intraoperative Doppler ultrasound as a means of preventing vertebral artery injury during Goel and Harms C1-C2 posterior arthrodesis: technical note

Vertebral artery injury (VAI) is a potential catastrophic complication of Goel and Harms C1-C2 posterior arthrodesis. Meticulous study of preoperative spinal CT angiography together with neuronavigation plays a fundamental role in avoiding VAI. Doppler ultrasonography may be an additional intraoperative tool, providing real-time identification of the vertebral artery (VA) and thus helping its preservation.Thirty-three consecutive patients with unstable odontoid fractures underwent Goel and Harms C1-C2 posterior arthrodesis. Surgery was performed with the aid of lateral fluoroscopic control in 16 cases (control group) that was supplemented by Doppler ultrasonography in 17 cases (Doppler group). Two patients in each group had a C1 ponticulus posticus. In the Doppler group, Doppler probing was performed during lateral subperiosteal muscle dissection, stepwise drilling, and tapping. Blood flow velocity in the V3 segment of the VA was recorded before and after posterior arthrodesis. All patients had a 12-month outpatient follow-up, and outcome was assessed using the Smiley-Webster Pain Scale. Neither VAI nor postoperative neurological impairments were observed in the Doppler group. In the control group, VAIs occurred in the 2 patients with C1 ponticulus posticus. In the Doppler group, 1 patient needed intra- and postoperative blood transfusions, and no difference in terms of Doppler signal or VA blood flow velocity was detected before and after C1-C2 posterior arthrodesis. In the control group, 3 patients needed intra- and postoperative blood transfusions.Useful in supporting fluoroscopy-assisted procedures, intraoperative Doppler may play a significant role even during surgeries in which neuronavigation is used, reducing the chance of a mismatch between the view on the neuronavigation screen and the actual course of the VA in the operative field and supplying the additional data of blood flow velocity.

Development of a Patient-specific Guide for High Cervical Spine Fixation

Objective

High cervical spine fixation represents a challenge for spine surgeons due to the complex anatomy and the risks of vascular and medullar injury. The recent advances in 3-D printing have unfolded a whole new range of options for these surgeons.

Methods

In the present study, a guide for the placement of the lateral mass screw in the C1 vertebra was developed using 3-D printing. Eight real-size models of the high cervical spine and their respective screw guides were built using computed tomography (CT) scan images. The guidewires were inserted with the help of the printed guides and then the models were analyzed with the help of CT scan images.

Results

All of the guidewires in the present study obtained a safe placement in the models, avoiding the superior and inferior articular surfaces, the vertebral foramen, and the vertebral artery.

Conclusion

The present study demonstrated the efficiency of the guide, a reliable tool for aiding the insertion of guidewires for screws in lateral masses of the C1.

Quantitative Assessment of the Anatomical Footprint of the C1 Pedicle Relative to the Lateral Mass: A Guide for C1 Lateral Mass Fixation

STUDY DESIGN

Anatomic study.

OBJECTIVES

To determine the relationship of the anatomical footprint of the C1 pedicle relative to the lateral mass (LM).

METHODS

Anatomic measurements were made on fresh frozen human cadaveric C1 specimens: pedicle width/height, LM width/height (minimum/maximum), LM depth, distance between LM's medial aspect and pedicle's medial border, distance between LM's lateral aspect to pedicle's lateral border, distance between pedicle's inferior aspect and LM's inferior border, distance between arch's midline and pedicle's medial border. The percentage of LM medial to the pedicle and the distance from the center of the LM to the pedicle's medial wall were calculated.

RESULTS

A total of 42 LM were analyzed. The C1 pedicle's lateral aspect was nearly confluent with the LM's lateral border. Average pedicle width was 9.0 ± 1.1 mm, and average pedicle height was 5.0 ± 1.1 mm. Average LM width and depth were 17.0 ± 1.6 and 17.2 ± 1.6 mm, respectively. There was 6.9 ± 1.5 mm of bone medial to the medial C1 pedicle, which constituted 41% ± 9% of the LM's width. The distance from C1 arch's midline to the medial pedicle was 13.5 ± 2.0 mm. The LM's center was 1.6 ± 1 mm lateral to the medial pedicle wall. There was on average 3.5 ± 0.6 mm of the LM inferior to the pedicle inferior border.

CONCLUSIONS

The center of the lateral mass is 1.6 ± 1 mm lateral to the medial wall of the C1 pedicle and approximately 15 mm from the midline. There is 6.9 ± 1.5 mm of bone medial to the medial C1 pedicle. Thus, the medial aspect of C1 pedicle may be used as an anatomic reference for locating the center of the C1 LM for screw fixation.

Occipitocervical Fusion Surgery: Review of Operative Techniques and Results

Objective Varying types of clinicoradiologic presentations at the craniovertebral junction (CVJ) influence the decision process for occipitocervical fusion (OCF) surgery. We discuss the operative techniques and decision-making process in OCF surgery based on our clinical experience and a literature review. Material and Methods A total of 49 consecutive patients who underwent OCF participated in the study. Sagittal computed tomography images were used to illustrate and measure radiologic parameters. We measured Wackenheim clivus baseline (WCB), clivus-canal angle (CCA), atlantodental distance (ADD), and Powers ratio (PR) in all the patients. Results Clinical improvement on Nurick grading was recorded in 36 patients. Patients with better preoperative status (Nurick grades 1-3) had better functional outcomes after the surgery (p = 0.077). Restoration of WCB, CCA, ADD, and PR parameters following the surgery was noted in 39.2%, 34.6%, 77.4%, and 63.3% of the patients, respectively. Complications included deep wound infections (n = 2), pseudoarthrosis (n = 2), and deaths (n = 4). Conclusion Conventional wire-based constructs are superseded by more rigid screw-based designs. Odontoidectomy is associated with a high incidence of perioperative complications. The advent of newer implants and reduction techniques around the CVJ has obviated the need for this procedure in most patients.