The impact of odontoid screw fixation techniques on screw-related complications and fusion rates: a systematic review and meta-analysis

Short-term and long-term results of odontoid screw fixation in patients with Type II and rostral Type III dens fractures

OBJECTIVES

To evaluate both the short-term and long-term outcomes of odontoid screw fixation (OSF), identifying potential risk factors for implant-related complications in patients with odontoid fractures.

METHODS

This is a retrospective observational cohort study. Inclusion criteria were as follows: 1) Type II fractures and rostral Type III fractures, according to the Anderson and D'Alonzo classification; 2) patients older than 15 years. Exclusion criteria were: 1) other Type III injuries; 2) osteoporosis confirmed by densitometry or a CT bone density score below 100 Hounsfield units; 3) odontoid fractures related to tumors or aneurysmal bone cysts.

RESULTS

In total, 56 patients were considered for the analysis of short-term results, and 26 patients were evaluated for long-term outcomes. No significant differences were observed in the preoperative imaging data and intraoperative features of OSF between patients with Type II and rostral Type III fractures. The mean operative duration was 63.9 ± 20.9 min, and the mean intraoperative blood loss was 22.1 ± 22.9 ml. Screw cut-out was identified in four patients with rostral Type III fractures (p = 0.04). The rate of screw cut-out was found to correlate with the degree of dens fragment displacement. The bone fusion rate was 95.7%. CT scans identified stable pseudarthrosis in two cases. We observed C2-C3 ankylosis in all cases following partial disc resection. One third of patients with screws placed through the anterior lip of C2 showed no C2-C3 ankylosis. A strong trend towards lateral joint ankylosis formation in patients with a median lateral mass dislocation of 11.9 mm was observed. Most SF-36 scores either matched or exceeded the corresponding normal median values in the published reference database.

CONCLUSIONS

OSF is a reliable treatment method of Type II and rostral Type III odontoid fractures with fragment displacement of 4 mm or less. The minimally invasive OSF through the anterior-inferior lip of C2, using monocortical screw placement and cannulated instruments, without rigid intraoperative head immobilization, is sufficient to achieve favorable clinical and fusion results. This technique reduces the risk of ankylosis in the C2-C3 segment. OSF restore the quality of life for patients with odontoid fractures to levels comparable to those of the general population norm.

Two-screw osteosynthesis is biomechanically superior to single-screw osteosynthesis for type II odontoid fractures

The data on the use of a one- or two-screw technique (1S, 2S) for ventral osteosynthesis of type II dens fractures are contradictory. The aim was to design an apparatus to mimic the physiological conditions and test stability with 1S, 2S, and a headless compression screw (HCS) for osteosynthesis of artificially created type II odontoid fractures. The apparatus was mounted on a Zwick materials testing machine. A total of 18 C1-2 specimens were stratified into three groups (1S, 2S, HCS). Odontoid fractures were artificially created, and osteosynthesis was performed. Each specimen was tested at loads increasing from 1 to 40 N. Screw loosening was observed visually, by fatigue data, and by a camera tracking system. Analysis of the Zwick data and the camera data revealed a significant higher stability after 2S compared to 1S and HCS treatment (Zwick data: p = 0.021, camera data: p < 0.001), while visible screw loosening showed a superiority of the 2S only over HCS (p = 0.038). The developed apparatus allowed the dynamic study of the atlantoaxial joint with a high approximation to physiological conditions. The results demonstrated superiority of the 2S over the 1S and HCS in biomechanical stability in the treatment of type II odontoid fractures.

Biomechanical comparison of two different compression screws for the treatment of odontoid fractures in human dens axis specimen

BACKGROUND

Lag screw osteosynthesis for odontoid fractures has a high rate of pseudoarthrosis, especially in elderly patients. Besides biomechanical properties of the different screw types, insufficient fragment compression or unnoticed screw stripping may be the main causing factors for this adverse event. The aim of the study was to compare two screws in clinical use with different design principles in terms of compression force and stability against screw stripping.

METHODS

Twelve human cadaveric C2 vertebral bodies were considered. Bone density was determined. The specimens were matched according to bone density and randomly assigned to two experimental groups. An odontoid fracture was induced, which were fixed either with a 3.5 mm standard compression screw or with a 5 mm sleeve nut screw. Both screws are certified for the treatment of odontoid fractures. The bone samples were fixed in a measuring device. The screwdriver was driven mechanically. The tests were analyzed for peak interfragmentary compression and screw-in torque with a frequency of 20 Hz.

FINDINGS

The maximum fragment compression was significantly higher with screw with sleeve nut at 346.13(SD ±72.35) N compared with classic compression screw at 162.68(SD ±114.13) N (p = 0.025). Screw stripping occurred significantly earlier in classic compression screw at 255.5(SD ±192.0)° rotation after reaching maximum compression than in screw with sleeve nut at 1005.2(SD ±341.1)° (p = 0.0039).

INTERPRETATION

Screw with sleeve nut achieves greater fragment compression and is more robust to screw stripping compared to classic compression screw. Whether the better biomechanical properties lead to a reduction of pseudoarthrosis has to be proven in clinical studies.

Does the Surgical Approach Matter in Treating Odontoid Fractures? A Comparison of Mechanical Complication Rates Between Anterior Versus Posterior Surgical Approaches: A Meta-Analysis and Systematic Review

Objective

Odontoid fractures are treated surgically through the anterior or posterior approach. Each surgical approach has its advantages and disadvantages, so the preferred approach remains debatable. There are few meta-analyses or systemic reviews on the mechanical complications of surgical treatment for odontoid fractures. This meta-analysis aimed to compare the operation-related morbidity, including mechanical complications, and mortality of patients with odontoid fractures, treated via the anterior or posterior approach.

Methods

A systematic search was performed on PubMed/Medline, Embase, and the Cochrane Library for the studies up to October 2023 on the complication rate of the surgical treatment of odontoid fractures, related to the surgical approach. The risk ratios (RR) with the 95% confidence intervals (CIs) were pooled to assess the mechanical complication rates, other complications, revision surgery, and mortality, depending on the surgical approach.

Results

A total of 1,519 studies were retrieved using the search strategy, and 782 patients from 15 articles were included in this meta-analysis. Mechanical complications were significantly more frequent in the anterior surgical group with low heterogeneity. The incidences of fracture nonunion and revision surgery were also higher in the anterior surgery group. However, there was no significant difference in systemic complications and mortality rates between the two groups.

Conclusion

The posterior approach was more advantageous than the anterior approach in terms of mechanical complications, fusion rates, and incidence of revision surgery. However, further studies, should be performed to strengthen these results.

A True Percutaneous Anterior Odontoid Screw Fixation: The Results of 42 Cases by a Single Surgeon

OBJECTIVE

This study aimed to analyze a clinical series of odontoid fractures treated with true percutaneous anterior odontoid screws. The technique we used is different from the traditional approach of using blunt dissection to arrive at the anterior surface of the vertebral body.

METHODS

Between 2004 and 2021, forty-two patients underwent anterior screw fixation of the odontoid process using the true percutaneous technique without dissection among the fascial planes. Instead, we pressed from the medial border of the sternocleidomastoideus muscle with our second and third fingers to feel the vertebrae under the skin. Thus, the carotid artery is pushed laterally, the trachea-esophageal complex is moved medially, and when no esophagus, great vessels, etc., can be felt under our fingers; we have reached the anterior surface of the spine. Advancing the Jamshidi needle between the fingers causes it to pass only through the fascial layers. The absence of a gap between the dilatation tubes prevents any tissue from escaping into the tubes.

RESULTS

We had no intraoperative complications, such as esophageal, tracheal, or carotid injury. One patient required screw revision. In total, 5 patients died during the follow-up period, and 3 were lost to follow-up. There was no residual neck pain in our cohort, and no instability was noted on flexion-extension radiographs, even in ten patients without solid bone fusion.

CONCLUSIONS

True percutaneous anterior odontoid screw fixation is a safe and reliable procedure for treating odontoid fractures. The fibrous union of odontoid fractures provides as much stability as a solid bone fusion.

Full-Endoscopic Anterior Odontoid Screw Fixation: A Novel Surgical Technique

OBJECTIVE

First, to propose a novel minimally invasive technique of full-endoscopic anterior odontoid fixation (FEAOF) that aims to reduce the risk of retropharyngeal approach (both open and percutaneous techniques) to anterior odontoid screw fixation. Second, to describe steps of the procedure and, lastly, to report the initial outcomes in patients treated with this novel technique.

METHODS

Four non-consecutive patients who were diagnosed with a displaced odontoid fracture (Anderson-D'Alonzo classification type II and Grauer subclassification type A or B) from 2019 to 2020 underwent surgical fixation by our novel technique for anterior odontoid screw fixation. A detailed technical approach of FEAOF for the surgical treatment of type II odontoid fractures was described, and the patients' outcomes based on postoperative radiographic results including computed tomography (CT), clinical outcome parameters including visual analogue scale (VAS) for neck pain both preoperatively and at postoperative follow-up, and range of neck motion at the final follow-up were reported.

RESULTS

The mean age was 33.5 years (24-41), three patients were male. The mean operative time was 93.75 min, and the mean blood loss was 7.5 ml. An immediate post-operative thin-sliced CT showed that all patients achieved satisfactory reduction and proper screw position. No screw malposition or penetration was found. At a 6-month follow-up, a thin-sliced CT demonstrated solid bony union in every case. The mean VAS for neck pain was reduced from 6.5 to 0.6 at the 6-months follow-up. At the final follow-up, all patients showed improvement in ranges of motion without any complications; however, one patient was lost to follow-up.

CONCLUSIONS

FEAOF is a feasible and effective option for treating type II odontoid fractures. The procedure is less invasive than other techniques and provides clear direct visualization of the involved structures.

Anterior Odontoid Screw Fixation for C2 Fractures: Surgical Nuances, Complications, and Factors Affecting Fracture Union

OBJECTIVE

Type II odontoid fractures are the commonest C2 fractures. The management of dens fractures remains controversial with various radiological and fracture morphological factors affecting the approach and outcomes.

METHODS

All cases of anterior odontoid screw fixation between 2010 and 2020 were retrospectively analyzed. Patients' clinical, radiological (type of fracture, orientation, displacement, and diastasis), operative (single vs. double screw) and follow-up records were documented. The postoperative imaging findings were classified into grades I (excellent), II (good), and III (poor) based on the anatomical alignment with the screw. Follow-up cervical computed tomography was reviewed for fracture union.

RESULTS

A total of 49 patients with a mean age of 37.3 ± 13.8 years were included in the study. The average time from injury to surgery was 23.1 ± 22.2 days. The bicortical screw purchase and superoposterior odontoid tip breach significantly affected the postoperative alignment (P = 0.035 each). Fracture union was noted in 41 (83.7%) patients. The horizontal fracture displacement ≥2.5 mm (P = 0.02) and poor postoperative fracture alignment (P < 0.001) resulted in worse fracture union rates. Transient dysphagia was the commonest complication (n = 12), whereas screw breakout (n = 2) and pullout (n = 2) were other hardware-related complications. One patient underwent re-exploration for screw readjustment and 2 underwent posterior instrumentation.

CONCLUSIONS

Anterior odontoid screw fixation is technically straightforward, less morbid, and preserves biomechanical cervical mobility, when compared with the posterior instrumentation. With careful patient selection, meticulous surgical planning, and intraoperative image-guided screw insertion, good fracture union outcomes can be obtained. In the current study, we were able to achieve stable fracture union in 83.7% patients.

Determination and optimization of ideal patient candidacy for anterior odontoid screw fixation

Background:

Odontoid process fractures are one of the most common spine fractures, especially in patients over age 70. There is still much controversy over the ideal candidate for anterior odontoid screw fixation (AOSF), with outcomes affected by characteristics such as fracture morphology, nonideal body habitus, and osteoporosis. Therefore, this systematic review seeks to discuss the optimal criteria, indications, and adverse postoperative considerations when deciding to pursue AOSF.

Methods:

This investigation was conducted from experiential recall and article selection performed using the PubMed electronic bibliographic databases. The search yielded 124 articles that were assessed and filtered for relevance. Following the screening of titles and abstracts, 48 articles were deemed significant for final selection.

Results:

AOSF is often utilized to treat Type IIB odontoid fractures, which has been shown to preserve atlantoaxial motion, limit soft-tissue injuries/blood loss/vertebral artery injury/reduce operative time, provide adequate osteosynthesis, incur immediate spinal stabilization, and allow motion preservation of C1 and C2. However, this technique is limited by patient characteristics such as fracture morphology, transverse ligament rupture, remote injuries, short neck or inability to extend neck, barrel chested, and severe spinal kyphosis, in addition to adverse postoperative outcomes such as dysphagia and vocal cord paralysis.

Conclusion:

Due to the fact that odontoid fractures have a significant morbidity in elderly population, treatment with AOSF is generally recommended for this population with higher risk for nonoperative fusion. Considerations should be made to achieve fracture stability and fusion, while lowering the risk for operative and postoperative complications.