Posterior screw fixation in the subaxial cervical spine: a technique and literature review

Evaluating laminar and lateral mass screw techniques in cervical injury management: A case series

INTRODUCTION AND IMPORTANCE

The cervical spine is a dynamic structure that protects adjacent nervous innervation and maintains the range of motion (ROM) of the head and neck. Fractures in this area can lead to high mortality and morbidity, with bone fractures accounting for 56 % of cervical spinal cord injuries. This case series presents a series of cervical pathologies treated with posterior decompression and stabilization using laminar and lateral mass screw fixation.

METHODS

This research is a case series of four patients treated with laminar and lateral mass screw technique. All patients received a surgical procedure, including posterior compression and stabilization, which included the use of a laminar and lateral mass screw. We followed the patient for 12 months. During follow up, outcome measures consisting of VAS, range of motion, neurological status, ODI Score, SF-12 Score and any complications related to the surgical procedure was recorded and calculated every 3 months.

OUTCOMES

This series examines four distinct cases. The initial case pertained to a female patient, aged 72, who exhibited tetraparesis resulting from a burst fracture occurring in the C3-C5 vertebrae. The underlying etiology of this pathology is considered to be mineral bone disease associated with thyroid hormone imbalance due to thyroid cancer. The second instance was a 14-year-old child experiencing neck pain due to spondylitis tuberculosis in the C1-C2 region, accompanied by a retropharyngeal abscess and occipitocervical dissociation (OCD) with basilar invagination. The third example pertained to a patient who is 9 years old and presented with weakness in all extremities due to C1 fracture-dislocation. The fourth case was a 14-year-old patient who experienced a fall from a bunk bed. This patient was diagnosed with Traumatic Atlantoaxial dislocation with odontoid fracture Type II. All patients showed improved cervical curvature and range of motion with the advantages of reduction of intraoperative haemorrhage, as well as a decrease in postoperative rehabilitation duration. Overall, the data shows a general trend of improvement in VAS and ODI scores over time, with SF-12 scores stabilizing or slightly decreasing by 12 months post-operation.

CONCLUSION

The use of a lateral mass screw for subaxial cervical injuries can be employed to manage cervical spine pathologies like fractures and infections, including spondylitis TB. However, more research is required to evaluate the long-term complications and success rates of this technique.

The Attallah screw: Where safety meets robustness in posterior subaxial cervical instrumentation

Posterior fixation of the subaxial cervical spine (SCS) commonly relies on the application of lateral mass screws (LMS), with pedicle screws being a less prevalent alternative. The present study provides another option: A recently introduced novel approach, the Attallah screw, intended to ensure a safety profile comparable to that of LMS, combined with a strength profile similar to that of pedicle screws. The focus of the present study is the comparative analysis of peak insertion torques for these three screw types. Employing standard surgical techniques and instruments, Attallah screws were scheduled for insertion on the right side of the SCS in 15 cadavers, pedicle screws on the left side in 8 cadavers, and LMS on the left side in the remaining 7 cadavers. The peak insertion torque was recorded using an electronic torque screwdriver. The results revealed that the peak insertion torques were similar in the pedicle and the Attallah screw at C3, C4 and C7, but differed at C5 (mean ± SD; pedicle, 79.5±19.6 cNm; Attallah, 56.7±18.5 cNm; P=0.029) and C6 (pedicle, 85.4±28.7 cNm; Attallah, 49.8±17.9 cNm; P=0.004) in favor of the superior pedicle screw measurements. The peak insertion torques of the pedicle screw were superior to the corresponding data from the LMS from C4 to C7. By contrast, the peak insertion torques of the Attallah screw were only superior to those of the LMS at C7 (Attallah, 69.5±24.5 cNm; lateral mass, 40.5±21.4 cNm; P=0.030), although similar trends were observed at the other cervical levels. On the whole, the findings presented herein indicate the level-dependent superior robustness of the Attallah screw as a posterior cervical fixation method compared to the LMS. However, from a biomechanical perspective, the pedicle screw remains the preeminent choice for fixation within the C5-C6 range.

Traumatic Cervical Facet Fractures and Dislocations

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Flexion-distraction, axial loading, and rotational forces can cause various degrees of osseoligamentous disruption of the cervical spine, leading to traumatic cervical facet fractures and dislocations.

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Low-energy forces lead to minimally displaced facet fractures that often can be treated with immobilization only. High-energy forces are more likely to cause unstable injuries with or without neurologic compromise, which may require surgical intervention.

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The initial treatment of cervical facet injuries requires patient evaluation and management through the Advanced Trauma Life Support (ATLS) protocols, while definitive management varies based on the biomechanical components of the injury, the neurologic status of the patient, and additional patient factors.

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Cervical facet injuries often require a multidisciplinary approach to optimize long-term functional outcomes and minimize serious complications.

A new posterior stabilization technique in pediatric subaxial cervical vertebrae: Stabilization of spinous processes with the microplate/screw system: A radiological anatomy study

BACKGROUND

There are limited options for posterior stabilization techniques in cases of cervical subaxial instability in children. We designed this study to investigate whether the spinous process (SP) stabilization, which was previously used in adults, can also be used in children.

METHODS

Children aged 4-12 years who were admitted to our hospital between 2012 and 2020 and underwent 3D cervical computed tomography (CT) were retrospectively screened. Children without cervical spine fractures, tumors, deformities, or any ab-normalities and motion artifacts on CT were included in the study. Eight hundred seventy children were identified. Then, 360 children randomly selected from the patient pool were divided into nine different age groups or 3 different age groups (4-6 years, 7-9 years, and 10-12 years). The length, height, thickness, and anomalies of subaxial SPs were studied on CT images of children. The suitability of the SPs for the microplate/screw stabilization system was investigated.

RESULTS

The suitability rate for screw insertion was 57.6% and the suitability rate for the stabilization in at least one segmental unit was 74.7%. The eligibility rate for stabilization involving C3, 4, 5, 6, and 7 vertebrae was 16.1%. There were nine different stabilization combinations and C6-7 segmental unit (71.9%) were the most common in those combinations. Bifidity prevented screw insertion in 21% of children. We found that the screw acceptance rate of SP started to increase statistically around 8 years of age and the number of segmental units that could be stabilized was at the age of 10-12 at most.

CONCLUSION

According to the results of this study, we believe that the SP stabilization method recommended for children can be used as a salvage method, to support anterior stabilization or alone in a small number of selected cases.

Is it Better to Stop at C2 or C3/4 in Elective Posterior Cervical Decompression and Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

(a) Compare operative variables, complications, and patient-reported outcomes (PROs) in patients with an upper instrumented vertebrae (UIV) of C2 versus C3/4, and (b) assess outcomes based on C2 screw type.

SUMMARY OF BACKGROUND DATA

When performing elective posterior cervical laminectomy and fusion (PCLF), spine surgeons must choose the upper instrumented vertebrae (UIV) at the subaxial cervical spine (C3/4) versus C2. Differences in long-term complications and PROs remain unknown.

METHODS

A single-institution, retrospective cohort study from a prospective registry was conducted. All patients undergoing elective, degenerative PCLF from December 2010 to June 2018 were included. Patients were divided into a UIV of C2 versus C3/4. Groups were 2:1 propensity matched for fusion extending to the thoracic spine. Demographics, operative, perioperative, complications, and 1-year PRO data were collected.

RESULTS

One hundred seventeen patients underwent elective PCLF and were successfully propensity matched (39 C2 vs. 78 C3/4). Groups were similar in fusion extending to the thoracic spine (P = 0.588). Expectedly, the C2 group had more levels fused (5.63 ± 1.89) compared with the C3/4 group (4.50 ± 0.91) (P = 0.001). The C2 group had significantly longer operative time (P < 0.001), yet no differences were seen in estimated blood loss (EBL) (P = 0.494) or length of stay (LOS) (P = 0.424). Both groups significantly improved all PROs at 1-year (EQ-5D; NRS-NP/AP; NDI). Both groups had the same percentage of surgical adverse events at 6.8% (P = 1.00). Between C2 screw type, no differences were seen in operative time, EBL, LOS, complications, or PROs.

CONCLUSION

In patients undergoing elective PCLF, those instrumented to C2 had only longer operative times compared with those stopping at C3/4. No differences were seen in EBL, LOS, 1-year PROs, and complications. Type of C2 screw had no impact on outcomes. Besides increased operative time, instrumenting to C2 had no detectable difference on surgical outcomes or adverse event rates.Level of Evidence: 3.

Ultrasound image guided and mixed reality-based surgical system with real-time soft tissue deformation computing for robotic cervical pedicle screw placement

Cervical pedicle screw (CPS) placement surgery remains technically demanding due to the complicated anatomy with neurovascular structures. State-of-the-art surgical navigation or robotic systems still suffer from the problem of hand-eye coordination and soft tissue deformation. In this study, we aim at tracking the intraoperative soft tissue deformation and constructing a virtual physical fusion surgical scene, and integrating them into the robotic system for CPS placement surgery. Firstly, we propose a real-time deformation computation method based on the prior shape model and intraoperative partial information acquired from ultrasound images. According to the generated posterior shape, the structure representation of deformed target tissue gets updated continuously. Secondly, a hand tremble compensation method is proposed to improve the accuracy and robustness of the virtual-physical calibration procedure, and a mixed reality based surgical scene is further constructed for CPS placement surgery. Thirdly, we integrate the soft tissue deformation method and virtual-physical fusion method into our previously proposed surgical robotic system, and the surgical workflow for CPS placement surgery is introduced. We conducted phantom and animal experiments to evaluate the feasibility and accuracy of the proposed system. Our system yielded a mean surface distance error of 1.52 ± 0.43 mm for soft tissue deformation computing, and an average distance deviation of 1.04 ± 0.27 mm for CPS placement. Results demonstrated that our system involves tremendous clinical application potential. Our proposed system promotes the efficiency and safety of the CPS placement surgery.

Patient-Matched 3-D-Printed Guides for the Insertion of Cervical Pedicle Screws in Tumor Surgery

Background

Pedicle screw fixation in the cervical spine provides biomechanical advantages compared to other stabilization techniques. However, pedicle screw insertion in this area is challenging due to the anatomical conditions with a high risk of breaching the small pedicles and violating the vertebral artery or neural structures. Today, several techniques to facilitate screw insertion and to make the procedure safer are used. 3-D-printed patient-matched guides based on a CT reconstruction are a helpful technique which allows to reduce operation time and to improve the safety of pedicle screw insertion at the cervical spine.

Cases

3-D-printed patient-matched drill guides based on a CT scan with a 3-D reconstruction of the spine were used in two challenging cervical spine surgical tumor cases to facilitate the implantation of the pedicle screws. The screw position was controlled postoperatively by means of the routinely performed CT scan.

Results

Postoperative imaging (conventional radiographs and CT scan) revealed the correct position of the pedicle screws. The time needed for screw insertion was short, and the need for intraoperative fluoroscopy could be reduced. There was no intra- or postoperative complication related to the pedicle screw implantation. Both tumors could be removed completely.

Conclusion

These preliminary results show that 3-D-printed patient-specific guides are a promising tool to support and facilitate the implantation of cervical pedicle screws. The time needed for insertion is short, and intraoperative fluoroscopy time can be reduced. This technique allows for both a meticulous preoperative planning and a correct and therefore safe intraoperative positioning of cervical spine pedicle screws.

Comparison of the maximum possible lengths of insertable screws in the Subaxial Cervical Spine

BACKGROUND

Lateral mass screws are the most commonly used fixation technique in the Subaxial Cervical Spine (SCS), their main advantages being that they are easy to insert and safe in their application. Pedicle screws are significantly longer, are quite challenging to insert in most settings and are accompanied by the risk of serious complications such as vascular and neural injuries. We have therefore developed a new technique, which permits safe insertion of long screws in the SCS.

METHODS

A radiological evaluation was carried out to determine the maximum possible insertable screw length in the SCS when using the following techniques: pedicle, lateral mass (Magerl's) and "Attallah" screws. Scans of 66 cervical spines were analyzed to determine the maximum possible screw lengths of all three screw insertion techniques, based on the standard description through the vertebrae from C3 to C7.

RESULTS

The maximum possible length of the Attallah screw of 20.7 ± 2.5 mm (mean value ± SD) is only 2.4 mm shorter than the pedicle screw (23.1 ± 1.8 mm) along the SCS. The lateral mass screw is with 10.2 ± 1.3 mm full 12.9 mm shorter than the pedicle screw.

CONCLUSIONS

The maximum possible length of the Attallah screw is close to that of the pedicle screw and significantly greater than that of the lateral mass screw. We provide a fixation method comparable to the pedicle screw in its strength and to the lateral mass screw in its safety.

Clinical efficiency of operating room-based sliding gantry CT as compared to mobile cone-beam CT-based navigated pedicle screw placement in 853 patients and 6733 screws

PURPOSE

Multiple solutions for navigation-guided pedicle screw placement are available. However, the efficiency with regard to clinical and resource implications has not yet been analyzed. The present study's aim was to analyze whether an operating room sliding gantry CT (ORCT)-based approach for spinal instrumentation is more efficient than a mobile cone-beam CT (CBCT)-based approach.

METHODS

This cohort study included a random sample of 853 patients who underwent spinal instrumentation using ORCT-based or CBCT-based pedicle screw placement due to tumor, degenerative, trauma, infection, or deformity disorders between November 2015 and January 2020.

RESULTS

More screws had to be revised intraoperatively in the CBCT group due to insufficient placement (ORCT: 98, 2.8% vs. CBCT: 128, 4.0%; p = 0.0081). The mean time of patients inside the OR (Interval 5 Entry-Exit) was significantly shorter for the ORCT group (ORCT: mean, [95% CI] 256.0, [247.8, 264.3] min, CBCT: 283.0, [274.4, 291.5] min; p < 0.0001) based on shorter times for Interval 2 Positioning-Incision (ORCT: 18.8, [18.1, 19.9] min, CBCT: 33.6, [32.2, 35.5] min; p < 0.0001) and Interval 4 Suture-Exit (ORCT: 24.3, [23.6, 26.1] min, CBCT: 29.3, [27.5, 30.7] min; p < 0.0001).

CONCLUSIONS

The choice of imaging technology for navigated pedicle screw placement has significant impact on standard spine procedures even in a high-volume spine center with daily routine in such devices. Particularly with regard to the duration of surgeries, the shorter time needed for preparation and de-positioning in the ORCT group made the main difference, while the accuracy was even higher for the ORCT.

Simple Technique to Place the Lateral Mass Screws in the Revision Surgery after Cervical Laminoplasty for Ossification of the Posterior Longitudinal Ligament

A lateral mass screw (LMS) is one of the standard anchor screws in posterior cervical fixation. Although the advantage of cervical LMS is that it is easier and safer to place than pedicle screw, it is sometimes difficult for surgeons to confirm the exact point for screw entry and accurate angle in cases of revision surgery. When LMS fixation is performed as revision surgery after cervical laminoplasty or laminectomy, it might be complicated to secure safe placement of the LMSs. We present a simple but practical technique involving a caliper and angle device for revision surgery after cervical laminoplasty for ossification of the posterior longitudinal ligament. In this technique, the distance between the bilateral entry points is ascertained using preoperative CT. Insertion of the screw is guided using the angle device set to 25 degrees. The technique presented here is easy and allows accurate placement of the LMSs in the posterior cervical spine, and is practical even for revision surgery.

Radiological analyses of the dimensions of the pedicle and dorsal part of the transverse process of subaxial vertebrae in the context of cervical spine surgery

BACKGROUND

Knowledge of the anatomical dimensions of distinct areas of the vertebral bodies and vertebral arches of the subaxial cervical spine are indispensable in the planning of osteosynthesis. The minute dimensions and complex anatomical orientation of the posterior vertebral arch structures in the subaxial spine render the insertion of screws - where needed - a challenging procedure. The pedicle option carries the risk of serious complications while the alternative of lateral mass only permits the insertion of short screws.

OBJECTIVE

The transverse process of the subaxial vertebrae offers unique possibilities on all counts and seems quite comparable in its dimensions with the pedicle. To our knowledge it has not been used previously for the insertion of screws in the subaxial spine.

METHODS

Therefore, the scans of 66 cervical spines were analysed for distinct lines of both structures.

RESULTS

The widths and lengths of the dorsal part of the transverse processes and of the pedicles are similar between both sides. Clear differences between females and males could be observed. The widths of both structures were closer to each other in C3 than in C4 to C7, while the lengths derived the most in C7.

CONCLUSION

The dorsal part of the transverse process might be suitable for the insertion of screws to stabilize the vertebral arch of the subaxial cervical spine. Gender adaptation might be required.

Polyaxial pedicle screw external fixation to stabilize oblique mandibular fractures in three standing, sedated horses

OBJECTIVE

To report the radiographic, surgical and postoperative features in horses with unstable oblique mandibular fractures secured with polyaxial pedicle screws (PPS) external fixation construct and intraoral wiring.

ANIMALS

Three client-owned horses.

STUDY DESIGN

Short case series.

METHODS

Two horses each had a unilateral fracture, which did not improve after conservative management, and one horse had bilateral fractures. Clinical and radiographic features were documented. Polyaxial pedicle screw external fixators and intraoral tension band wiring were applied in standing horses after combining sedation and regional nerve anesthesia. Intraoral wires were implanted through a lateral buccotomy between teeth (two horses) or burred through exposed crown (one horse) and then secured around the incisors. The PPS were inserted under radiographic guidance to avoid tooth roots. Healing was assessed with radiographic examination. The PPS external fixator rod and intraoral wires were removed first. The mandible was manipulated, and, if it was stable, the PPS were removed.

RESULTS

Implants were removed at 6, 8, or 10 weeks after the mandibles were palpably stable. Complications included broken wires in one horse, bone sequestration in one horse, and infection in one horse. Follow-up communication with the owners 12 to 18 months later confirmed complete healing without further complications of the fractured mandibles or teeth.

CONCLUSION

Polyaxial pedicle screw external fixation led to fracture healing and a return to function in all three horses. The complications encountered did not preclude a successful outcome.

CLINICAL SIGNIFICANCE

Polyaxial pedicle screw external fixation coupled with intraoral wiring provides an alternative to treat unstable equine mandibular fractures without general anesthesia.