Characteristics of Screw Perforation and Screw Loosening in Atlantoaxial Transarticular Fixation Using a Preoperative Computed Tomography-Based Navigation System.

BACKGROUND: Atlantoaxial transarticular fixation, also called the Magerl technique, is said to be the most robust biomechanical method of fixation of the atlantoaxial vertebrae. However, the procedure carries a risk of spinal cord and vertebral artery injury during the insertion process, especially in patients with a high-riding vertebral artery. In this study, a computed tomography (CT)-based navigation system was used for preoperative planning and insertion. This investigation sought to determine the rate and direction of screw perforation as well as the incidence of screw loosening in computer-assisted atlantoaxial transarticular fixation. METHODS: Sixty patients (31 men and 29 women; mean ± SD age: 65.3 ± 19.6 years) who received atlantoaxial transarticular screw insertion with preoperative CT navigation were analyzed. We investigated screw position and loosening by CT at the final follow-up. RESULTS: Of the 108 screws inserted, the rate of Grade 2 or higher perforation was 4.6% (5/108). Nine of 81 (11.1%) screws inserted into the 44 patients who were followed for at least 6 months showed loosening. Logistic regression analysis revealed that unilateral insertion (odds ratio: 8.50, 95% confidence interval: 1.53-47.2, P = 0.014) was significantly associated with the incidence of screw loosening. CONCLUSIONS: The screw perforation rate of Grade 2 or higher in computer-assisted atlantoaxial transarticular screw fixation was 4.6%, with comparable frequencies of perforation direction. Unilateral insertion was a significant independent factor associated with screw loosening, which occurred in 11.1% of insertions. CLINICAL RELEVANCE: Spine surgeons should follow up with patients with caution because screws with unilateral insertion are prone to loosening.

Atlantoaxial Anterior Transarticular Screw Fixation: Indications and Surgical Technique.

Posterior atlantoaxial screw fixation is a widely adopted therapeutic option for C1-C2 instability secondary to fractures or dislocation, degenerative diseases, or tumors at this level. Anterior transarticular screw fixation (ATSF) is an effective alternative to the posterior approaches, presenting several advantages despite being scarcely known and rarely chosen.In this chapter, we describe the ATSF step by step, illustrating its variations reported in literature, and we critically analyze the several advantages and contraindications of this technique. Moreover, we provide a list of tips and tricks on the surgical procedure, including critical operating room settings-the result of more than 10 years of experience in the field by a senior author.ATSF is a valid strategy for the treatment of different diseases occurring at the level of the atlantoaxial complex that needs consideration. Given the significant learning curve of this strategy, some hints may be essential to begin introducing this technique in the personal armamentarium of a spine surgeon so that they can perform ATSF safely and effectively.

Simulated Weightbearing and Articular Injury From Transarticular Screws in a Ligamentous Lisfranc Injury Model.

BACKGROUND: Transarticular screw fixation is a common surgical treatment for tarsometatarsal ligamentous (Lisfranc) injuries. Iatrogenic damage to articular cartilage from screw placement, however, has been thought to potentially lead to increased risk of tarsometatarsal (TMT) joint arthritis after initial injury. To date, no study has evaluated the effect of weightbearing on articular cartilage after screw fixation. The aim of this study was to create a Lisfranc injury and quantify and compare articular damage due to screw fixation before and after simulated weightbearing. METHODS: A ligamentous Lisfranc injury was created in 10 cadaveric specimens and treated with transarticular screws. Specimens were cycled for 1000 cycles at 250 N to simulate 2 weeks of physiologic weightbearing. Rotation and diastasis across the Lisfranc complex were measured. Articular injury as a percentage of total articular surface was measured using digital imaging of the first and second TMT joint before and after simulated weightbearing. Comparisons between articular damage were made and statistical analysis was performed. RESULTS: Simulated partial weightbearing increased articular injury 1.44-fold (P < .001). The second metatarsal (M2) showed the greatest increase (1.54-fold, P = .0047), whereas the first (M1) showed the least (1.35-fold, P = .0083). Increases seen at the medial (1.43-fold, P = .0387) and middle cuneiform (1.44-fold, P = .0292) were intermediate between the values seen at M2 and M1. CONCLUSION: Articular damage from transarticular screw fixation significantly increased after simulated partial weightbearing. This may increase the risk of arthritis and future morbidity when using transarticular screws for the treatment of ligamentous Lisfranc injuries. CLINICAL RELEVANCE: Iatrogenic damage to articular cartilage due to screw fixation of ligamentous Lisfranc injuries may be increased with weightbearing.

Comparison of two treatments for atlantoaxial instability injury: C1-C2 transarticular screw fixation versus C1 lateral mass-C2 pedicle screw fixation.

Objective: This study evaluated the effectiveness and safety of C1-C2 transarticular screw fixation (transarticular screw fixation com-bined with bone grafting) and C1 lateral mass-C2 pedicle screw fixation (modified Harms technique) in patients with C1-C2 instability. Materials and methods: This prospective, self-controlled, single-center study evaluated two fixation techniques for the treatment of atlantoaxial instability injury. From June 2006 to February 2017, 118 patients were admitted to our hospital because of atlantoaxial instability injury. These patients were divided into two groups: group 1, including 52 patients who underwent C1-C2 transarticular screw fixation (C1C2-TAS group), and group 2, including 66 patients who underwent C1 lateral mass-C2 pedicle screw fixation (C1LM-C2PS group). Results: There were significant differences in the operation time, blood loss amount, and hospital stay length between the groups (p<0.001). The mean operation time (78.94 vs. 110.91 min; p=0.0003) and hospital stay length (5.31 vs. 8.34 days; p=0.0003) were shorter, and the mean blood loss amount during surgery (122.31 vs. 258.33 mL; p<0.0001) was smaller in the C1C2-TAS group than in the C1LM-C2PS group. The surgical complication rate was low and no vertebral artery injury was observed. After surgery, the clinical presentations were significantly reduced in both groups. The patients showed sati-sfactory internal fixation on postoperative radiography and computed tomography. Conclusion: Both C1-C2 transarticular screw fixation and C1 lateral mass-C2 pedicle screw fixation are effective and safe in treat-ing atlantoaxial instability injury. Notably, C1-C2 transarticular screw fixation yields a shorter operation time and hospital stay length and a smaller intraoperative blood loss amount than does C1 lateral mass-C2 pedicle screw fixation.

Transarticular Fixation Using Bioabsorptive Screws for Cervical Lesions.

Transarticular screw fixation is a method for posterior cervical fixation. It is ergonomic because neither connectors nor rods are needed. Biomechanical studies have shown that its fixation force is not inferior to that of lateral mass screws. More information is needed on the surgical outcome of procedures using bioabsorptive screws. We investigated the long-term surgical and radiological outcomes of posterior cervical decompression and fusion using bioabsorptive screws for transarticular fixation.Of 10 patients who underwent cervical spine transarticular fixation using bioabsorptive screws, nine presented with cervical degenerative spondylosis and one with a traumatic cervical spine injury. The mean postoperative follow-up period was 57.1 months. Transarticular screw fixation was successful in all 10 patients; no intraoperative complications were encountered. Bilateral screw breakage was discovered in a patient with cervical spine instability and associated dystonia due to cerebral palsy; there was no symptom deterioration, facet joint breakage, or instability exacerbation. Facet fusion was obtained in the nine other patients. At the patients' last visit, their clinical symptoms were significantly improved. Whole cervical spine alignment (-4.21 ± 7.2 to -5.2 ± 8.7) and the fused segment angle (mean, -0.1 ± 9.9 to -1.2 ± 13.7) did not significantly worsen postoperatively (mean: -0.1 ± 9.9 to -1.2 ± 13.7). Transarticular fixation using bioabsorptive screws is safe and associated with good long-term outcomes. In patients with exacerbation of local instability after posterior decompression, additional transarticular fixation using bioabsorbable screws is a treatment option.

Anterior atlanto-occipital transarticular screw fixation: a biomechanical comparison with posterior fixation techniques.

OBJECTIVE: Atlanto-occipital instability is commonly treated with posterior fixation. However, in patients with congenital or acquired factors, posterior fixation may not be possible. For these situations, a novel anterior atlanto-occipital transarticular screw (AATS) fixation technique has been introduced recently. However, biomechanical study of this technique is lacking. This study was designed to evaluate the biomechanical stability of AATS fixation for the atlanto-occipital joint and compare it with conventional posterior occipitocervical fixation (POCF). METHODS: Six cadaveric specimens (occiput-C4) were tested in four conditions, including intact, injury, injury + AATS, and injury + POCF states. A pure moment of 1.5 Nm was applied to specimens in flexion, extension, lateral bending, and axial rotation. The range of motion (ROM) and neutral zone (NZ) were calculated and compared from the occiput to C1. RESULTS: The AATS fixation constrained ROMs to 0.4° in flexion (p < 0.001), 0.4° in extension (p < 0.001), 1.0° in lateral bending (p < 0.001), and 0.7° in axial rotation (p < 0.001) when compared with the injury state. In all directions, there was no statistically significant difference observed in ROMs and NZs between AATS fixation and POCF (p > 0.05). CONCLUSIONS: This study identified that the novel AATS fixation, as stand-alone anterior fixation, was equivalent to POCF in all directions. The results suggest that anterior transarticular screw fixation is a biomechanically effective salvage technique for posterior atlanto-occipital fixation, and may also serve as supplemental fixation.

Robot-assisted atlantoaxial fixation: illustrative cases.

BACKGROUND: Placing screws in the high cervical spine can be challenging because of the vital anatomical structures located in that region. Precision and accuracy with screw placement is needed. The use of robotics in the cervical spine has been described before; however, here the authors describe the use of a new robotic setup. OBSERVATIONS: The authors describe 2 cases of robot-assisted placement of C2 pars screws and C1-2 transarticular screws. The operative plans for each patient were as follows: placement of C2 pars screws with C2-4 fusion for hangman's fracture and placement of C1-2 transarticular screws for degenerative disease. Intraoperative computed tomography (CT) was used to plan and navigate the screws. Postoperative CT showed excellent placement of hardware. Both patients presented for initial postoperative clinic visits with no recurrence of prior symptoms. LESSONS: Intraoperative robotic assistance with instrumentation of the high cervical spine, particularly C2 pars and C1-2 transarticular screws, may ensure proper screw placement and help avoid injury.

The Comparison Between Transarticular Screw Fixation and Segmental Screw-Rod Fixation for Posterior Fusion of the C1-2 Segment: A Systematic Review and Meta-Analysis.

OBJECTIVE: Both transarticular screw fixation (TAS) and segmental screw-rod fixation (SF) have been widely performed for C1-2 fusion; however, just only small clinical studies and a few meta-analyses comparing the 2 surgical techniques for C1-2 posterior fusion have been reported. METHODS: We searched the Cochrane, Embase, and Medline databases for articles comparing the intraoperative and postoperative outcomes of TAS and SF for C1-2 posterior fusion with April 14, 2022, as the publication cutoff date. The odds ratio (OR) and standardized mean difference were used to analyze differences in outcomes between the 2 abovementioned surgical techniques. A P value < 0.05 was considered statistically significant. RESULTS: A total of 5101 publications were assessed, and 6 studies were finally included in the study. In terms of the fusion rate, SF produced significantly better outcomes than TAS did (OR = 2.96, P = 0.02). With respect to surgical outcomes, blood loss and operation times were significantly lower in the TAS group than those in the SF group (P = 0.008 and P < 0.00001, respectively). The rate of vertebral artery injury was significantly lower in the SF group than that in the TAS group (OR = 3.95, P = 0.04). However, other complications, such as screw malposition, infection, hardware failure, and nonunion, were not significantly different between the 2 groups. CONCLUSIONS: SF showed a greater fusion rate and lower risk of vertebral artery injury than TAS did, but TAS showed less blood loss and lower operation times than SF.

Biomechanical Study on Three Screw-Based Atlantoaxial Fixation Techniques: A Finite Element Study.

STUDY DESIGN: This is a finite element study. PURPOSE: This study is aimed to compare the biomechanical behaviors of three screw-based atlantoaxial fixation techniques. OVERVIEW OF LITERATURE: Screw-based constructs that are widely used to stabilize the atlantoaxial joint come with their own challenges in surgery. Clinical and in vitro studies have compared the effectiveness of screw-based constructs in joint fixation. Nevertheless, there is limited information regarding the biomechanical behavior of these constructs, such as the stresses and strains they experience. METHODS: A finite element model of the upper cervical spine was developed. A type II dens fracture was induced in the intact model to produce the injured model. The following three constructs were simulated on the intact and injured models: transarticular screw (C1- C2TA), lateral mass screw in C1 and pedicle screw in C2 (C1LM1-C2PD), and lateral mass screw in C1 and translaminar screw in C2 (C1LM1-C2TL). RESULTS: In the intact model, flexion-extension range of motion (ROM) was reduced by up to 99% with C11-C2TA and 98% with C1LM1-C2PD and C1LM1-C2TL. The lateral bending ROM in the intact model was reduced by 100%, 95%, and 75% with C11-C2TA, C1LM1-C2PD, and C1LM1-C2TL, respectively. The axial rotation ROM in the intact model was reduced by 99%, 98%, and 99% with C11-C2TA, C1LM1-C2PD, and C1LM1-C2TL, respectively. The largest maximum von Mises stress was predicted for C1LM1-C2TL (332 MPa) followed by C1LM1-C2PD (307 MPa) and C11-C2TA (133 MPa). Maximum stress was predicted to be at the lateral mass screw head of the C1LM1-C2TL construct. CONCLUSIONS: Our model indicates that the biomechanical stability of the atlantoaxial joint in lateral bending with translaminar screws is not as reliable as that with transarticular and pedicle screws. Translaminar screws experience large stresses that may lead to failure of the construct before the required bony fusion occurs.

Posterior percutaneous transarticular stand-alone screw instrumentation of C1-C2 with endoscopic assistance: A report of two cases / Exploración instrumental percutánea posterior con tornillo independiente transarticular en C1-C2 mediante endoscopia: informe de dos casos

We present two cases of minimally invasive posterior transarticular screw fixation of C1-C2. The points for screw insertion were visualized by endoscopy via the instrumental port. A patient with a type III odontoid fracture with subluxation underwent a minimally invasive posterior stand-alone transarticular screw fixation. Despite the application of compression screws, for technical reasons, only minimal compression on the anterior third of the C1-C2 lateral joint was achieved. However, complete fracture fusion was achieved with stable fibrous C1-C2 fusion 2.5 years postoperatively. A second patient with a chronic type II odontoid fracture underwent percutaneous C1-C2 fixation by the same method. After 2 years, fracture fusion and C1-C2 lateral mass ankylosis were achieved. The use of a tubular retractor and endoscopy in stand-alone screw fixation of C1-C2 allows direct visualization of the screw entry point and decreases surgical trauma. This procedure might be an alternative to other methods of transarticular instrumentation (AU)

Presentamos dos casos de fijación posterior artroscópica con tornillo transarticular en C1-C2. Las ubicaciones para la inserción del tornillo se visualizaron mediante un trocar para el endoscopio. Un paciente con una fractura de apófisis odontoides de tipo III con luxación parcial se sometió a fijación posterior artroscópica con tornillo independiente transarticular. A pesar de la aplicación de tornillos de compresión y, por motivos técnicos, solo se logró una compresión mínima del tercio anterior de la articulación lateral C1-C2. Sin embargo, se logró la artrodesis completa de la fractura, con una artrodesis en C1-C2 fibrosa estable después de dos años y medio de la intervención quirúrgica. Un segundo paciente con una fractura de apófisis odontoides de tipo II crónica se sometió a fijación percutánea en C1-C2 con el mismo método. Después de dos años, se logró la artrodesis de la fractura y de la masa lateral en C1-C2. El uso de un separador tubular y de la endoscopia en la fijación con tornillo independiente en C1-C2 permite la visualización directa del punto de entrada del tornillo y disminuye el traumatismo quirúrgico. Este procedimiento puede ser una alternativa a otros métodos de exploración instrumental transarticular (AU)

Safety, efficacy, surgical, and radiological outcomes of short segment occipital plate and C2 transarticular screw construct for occipito-cervical instability.

OBJECTIVE: Our study aims to assess the safety, efficacy, clinicoradiological, functional, neurological outcomes, and complications of posterior occipitocervical fixation using an occipital plate and C1-2 transarticular screw (TAS) construct. STUDY DESIGN: This was a retrospective analysis of prospectively collected data. METHODS: Data of 27 patients who underwent occipital plate and C1-2 TAS construct at a single institute from 2010 to 2015 were collected and analyzed. Demographics, clinical parameters (Visual Analog Score, Oswestry Disability Index, and modified JOA score), radiological parameters - mean atlantodens interval, posterior occipitocervical angle, occipitocervical-2 angle, surgical parameters (operative time, blood loss, hospital stay, and fusion), and complications were evaluated. RESULTS: The mean age of the patients was 54.074 ± 16.52 years (18-81 years), the mean operative time was 116.29 ± 12.23 min, and the mean blood loss was 196.29 ± 38.94 ml. The mean hospital stay was 5.22 ± 1.28 days. The mean ± standard deviation follow-up duration was 62.52 ± 2.27 months. There was a significant improvement in clinical parameters and radiological parameters postoperatively. One patient with implant failure, one patient with pseudoarthrosis, one with neurological deterioration, two wound complications, and two dural tears were noted. CONCLUSION: Posterior occipitocervical reconstruction with O-C1-2 TAS construct provided excellent clinical outcomes, radiological outcomes, optimal correction of malalignment in the occipitocervical region, and with biomechanically sound fixation. Extending the instrumentation into the subaxial spine will lead to a decrease in the range of motion, increased surgical time, blood loss, more extensive muscle damage, and also increase the costs.

Posterior percutaneous transarticular stand-alone screw instrumentation of C1-C2 with endoscopic assistance: A report of two cases.

We present two cases of minimally invasive posterior transarticular screw fixation of C1-C2. The points for screw insertion were visualized by endoscopy via the instrumental port. A patient with a type III odontoid fracture with subluxation underwent a minimally invasive posterior stand-alone transarticular screw fixation. Despite the application of compression screws, for technical reasons, only minimal compression on the anterior third of the C1-C2 lateral joint was achieved. However, complete fracture fusion was achieved with stable fibrous C1-C2 fusion 2.5 years postoperatively. A second patient with a chronic type II odontoid fracture underwent percutaneous C1-C2 fixation by the same method. After 2 years, fracture fusion and C1-C2 lateral mass ankylosis were achieved. The use of a tubular retractor and endoscopy in stand-alone screw fixation of C1-C2 allows direct visualization of the screw entry point and decreases surgical trauma. This procedure might be an alternative to other methods of transarticular instrumentation.

Transarticular Screw Fixation in the Treatment of Severe C1-C2 Dislocation: A Case Series Report.

BACKGROUND: To aim of the present paper was to evaluate the results of halo traction and transarticular screw fixation combined with bone autoplasty in patients with severe atlantoaxial dislocation. CASE PRESENTATION: This is a retrospective study of severe cases of atlantoaxial dislocation in nine patients (six men and three women) treated with preoperative halo traction and posterior C1-C2 transarticular screw fixation combined with bone autoplasty from June 2006 to June 2011 at the Saint Paul Hospital (Hanoi). The mean age of patients was 37.48 ± 13.753 years (range, 26-50 years). The possibility of fixing dislocation using a halo apparatus was investigated through a series of preoperative halo corrections performed within a span of 1-2 weeks. For transarticular screw fixation, two transarticular screws were used that were positioned according to the Magerl technique. For bone autoplasty, an iliac crest bone graft approximately 3 × 2 cm in size was used. The postoperative assessment of clinical improvement was performed using the neck disability index (NDI), the American Spinal Injury Association (ASIA) impairment scale, and the visual analog scale (VAS) measurement instruments, through the gradation of atlantoaxial dislocation, and via the clivoaxial angle(CAA) index and the space available for cord (SAC) index after 6 months. The image diagnosis demonstrates that all the cases of atlantoaxial dislocations are unstable and correspond to the Fielding and Hawkins type III dislocation. Eight patients underwent complete reduction using the halo fixation device. In one patient, the C1-C2 displacement was manually reduced during surgery. CT scanning revealed that the accuracy of screw placement was 94.4%. The bone fusion rate was 100% after 6 months. Based on the ASIA impairment scale, the preoperative examination of patients revealed grade C injuries in seven patients and grade D injuries in two patients. After surgery, all patients had grade D injuries. Six months after surgery, four patients had moderate self-reported neck disability (30%-48%) and five patients reported mild disability (10%-28%); that is, the patient perception of the neck problem improved. In the postoperative phase, all patients showed an improvement in VAS pain scores and the SAC score returned to the normal range in all patients. The CAA returned to normal in only seven patients; in the other two patients, the CAA returned to a value that was close to normal (145° and 149°). CONCLUSION: Through halo traction combined with transarticular screw fixation and bone autoplasty, noticeable postoperative improvements were attained based on the clinical scores for NDI, ASIA, and VAS, as well as SAC and CAA.

Axis vertebral dimensions for safe screw placement: A CT normative data analysis.

INTRODUCTION: Morphometric evaluation of the pedicle and isthmus of second cervical vertebra (C2) (Axis) is extremely vital before contemplating any surgical stabilization involving the Craniovertebral region, in view of its proximity to the vertebral artery and the cervical nerve root. The dimensions of pedicles and isthmuses in C2 vary between individuals and there is paucity of data in the Indian population. This study strives to measure the average pedicle and isthmus dimensions in a sample of population, which would enable selection of screws with safest diameters to be used in C2; thereby avoiding injury to adjacent neurovascular structures. MATERIALS AND METHODS: One Hundred patients in the age group between 18 and 70 years who underwent CT scan of head and neck region were included in the study. The aim of this study was to assess the anatomic suitability of transarticular and pedicle screw placement in Axis vertebrae of Indian population and determine the maximum safe diameter for screw placement. The following parameters were measured in millimeters: Pedicle width, Pedicle angle, Internal height and Isthmic height. RESULTS: The Mean maximum diameter of potential pedicle screw was 4.99 ± 1.1 mm for the right side with the left side being slightly wider at 5.20 ± 1.16 mm. Twenty eight (28%; 56 out of 200 pedicles) had a measurement < 4.5 mm. The internal height in sagittal images representing the pedicle height was found to be 4.79 ± 0.96 mm on the right side and 4.75 ± 1.04 mm on the left side. Sixty five (65) out of 200 pedicles (32.5%) had measurements < 4.5 mm in sagittal plane. The Mean maximum diameter of potential Transarticular screw (outer diameter of isthmus) was 5.05 ± 0.78 mm for the right side and 5.18 ± 0.84 mm on the left side. DISCUSSION: Isthmic height < 4.5 mm could potentially violate the vertebral foramen when a 3.5 mm screw is used. In our study 22.5% isthmuses were narrow (<4.5 mm). The mean maximum safe diameter for a potential transarticular screw in the present study was 5.11 mm. Though our patients had smaller isthmus dimensions compared with literature, 77.5% of C2 could take a 4 mm transarticular screw quite comfortably considering the 0.5 mm margin on either side. In the present study, 28% of pedicles were found to be inappropriately sized (<4.5 mm) to accommodate the standard 3.5 mm screw. The mean maximum diameter of a potential pedicle screw in our study was 5.09 mm; and in 72% of patients a 4 mm screw could be placed with confidence. Though our patients on an average can accommodate a 4 mm screw comfortably, we suggest a protocol of obtaining CT measurements of C2 prior to operative intervention for identifying those individuals at risk of neurovascular injury; 22.5% for transarticular screw and 28% for pedicle screw.

Adult idiopathic de novo lumbar scoliosis: Analysis of surgical treatment in 14 patients by "only fixation".

OBJECTIVE: The authors report their experience with 14 cases having adult idiopathic de novo lumbar scoliosis (AIDLS) and presenting with the predominant symptoms of claudication pain in the low back and legs. The patients were treated by only multisegmental stabilization, and the surgical procedure aimed for arthrodesis without any form of bone or soft-tissue decompression. The clinical outcome of this novel form of surgical treatment is presented. MATERIALS AND METHODS: During the period of June 2014 to June 2019, 14 patients having AIDLS (degenerative scoliosis) were surgically treated. Apart from clinical and radiological guides, instability was diagnosed on the basis of direct physical observation of the status of articulation and by manual manipulation of bones of the region. The Camille transarticular facet screw fixation technique provided a quick, safe, and strong segmental spinal fixation. An additional inter-screw metal link plate provided intersegmental stability at selected levels. The Oswestry Disability index and visual analog scale were used to assess the patients before and after surgery and at follow-up. In addition, a personalized Patient Satisfaction Score was used to assess the outcome of surgery. RESULTS: Clinical symptomatic recovery was observed in all patients in the immediate postoperative period. During the average follow-up period, 100% patients had varying degrees of symptomatic relief. CONCLUSIONS: Spinal instability is the nodal point of pathogenesis of spinal degeneration-related AIDLS. Only fixation of the involved spinal segments is necessary, and decompression by bone or soft-tissue resection is not necessary.

Technical outcome of atlantoaxial transarticular screw fixation without supplementary posterior construct for rheumatoid arthritis.

BACKGROUND: transarticular screw (TAS) fixation without a supplementary posterior construct, even in rheumatoid arthritis (RA) patients, provides sufficient stability with acceptable clinical results. Here, we present our experience with 15 RA patients who underwent atlantoaxial (AA) TAS fixation without utilizing a supplementary posterior fusion. METHODS: To treat AA instability, all 15 RA patients underwent C1-C2 TAS fixation without a supplementary posterior construct. Patients were followed for at least 24 months. Pre- and postoperative sagittal measures of C1- C2, C2-C7, and C1-C7 angles, atlanto-dens interval (ADI), posterior atlanto-dens interval (PADI), and adjacent segment (i.e., C2-C3) anterior disc height (ADH) were retrospectively recorded from lateral X-ray imaging. The presence or absence of superior migration of the odontoid (SMO), cervical subaxial subluxation, C1-C2 bony fusion, screw pull-out, and screw breakage were also noted. RESULTS: There was little difference between the pre- and postoperative studies regarding angles measured. Following TAS fixation, the mean ADI shortened, and mean PADI lengthened. There was no difference in the mean measures of C2-C3 ADH. There was no evidence of SMO pre- or postoperatively. Two patients developed anterior subluxation at C5-C6; one of the two also developed anterior subluxation at C2-C3. All patients subsequently showed C1-C2 bony fusion without screw pull-out or breakage. CONCLUSION: In RA patients who have undergone C1-C2 TAS fixation, eliminating a supplementary posterior fusion resulted in adequate stability.

Design a novel integrated screw for minimally invasive atlantoaxial anterior transarticular screw fixation: a finite element analysis.

PURPOSE: To design a new type of screw for minimally invasive atlantoaxial anterior transarticular screw (AATS) fixation with a diameter that is significantly thicker than that of traditional screws, threaded structures at both ends, and a porous metal structure in the middle. The use of a porous metal structure can effectively promote bone fusion and compensate for the disadvantages of traditional AATSs in terms of insufficient fixation strength and difficulty of bone fusion. The biomechanical stability of this screw was verified through finite element analysis. This instrument may provide a new surgical option for the treatment of atlantoaxial disorders. METHODS: According to the surgical procedure, the new type of AATS was placed in a three-dimensional atlantoaxial model to determine the setting of relevant parameters such as the diameter, length, and thread to porous metal ratio of the structure. According to the results of measurement, the feasibility and safety of the new AATS were verified, and a representative finite element model of the upper cervical vertebrae was chosen to establish, and the validity of the model was verified. Then, finite element-based biomechanical analysis was performed using three models, i.e., atlantoaxial posterior pedicle screw fixation, traditional atlantoaxial AATS fixation, and atlantoaxial AATS fixation with the new type of screw, and the biomechanical effectiveness of the novel AATS was verified. RESULTS: By measuring the atlantoaxial parameters, the atlantoaxial CT data of the representative 30-year-old normal adult male were selected to create a personalized 3D printing AATS screw. In this case, the design parameters of the new screw were determined as follows: diameter, 6 mm; length of the head thread structure, 10 mm; length of the middle porous metal structure, 8 mm (a middle porous structure containing an annular cylinder ); length of the tail thread structure, 8 mm; and total length, 26 mm. Applying the same load conditions to the atlantoaxial complex along different directions in the established finite element models of the three types of atlantoaxial fusion modes, the immediate stability of the new AATS is similar with Atlantoaxial posterior pedicle screw fixation.They are both superior to traditional atlantoaxial anterior screw fixation.The maximum local stress on the screw head in the atlantoaxial anterior surgery was less than those of traditional atlantoaxial anterior surgery. CONCLUSIONS: By measuring relevant atlantoaxial data, we found that screws with a larger diameter can be used in AATS surgery, and the new AATS can make full use of the atlantoaxial lateral mass space and increase the stability of fixation. The finite element analysis and verification revealed that the biomechanical stability of the new AATS was superior to the AATS used in traditional atlantoaxial AATS fixation. The porous metal structure of the new AATS may promote fusion between atlantoaxial joints and allow more effective bone fusion in the minimally invasive anterior approach surgery.

Dorsal bridge plating versus. Transarticular screw fixation for lisfranc injuries: A systematic review and meta-analysis.

Lisfranc injuries are relatively uncommon but carry devastating consequences if left untreated. Although many surgical techniques have been proposed for best operative management, there is an ongoing debate over which procedure is superior. We performed a systematic review and meta-analysis comparing the outcomes of transarticular screw fixation and dorsal bridge plating in management of Lisfranc injuries. Ovid MEDLINE, Ovid Embase and Cochrane Central Register of Controlled Trials (CENTRAL) were searched to identify randomised controlled trials (RCTs) and cohort studies comparing the outcomes between screw and dorsal plate fixation. The pooled outcome data were calculated by random and fixed effect models. One prospective cohort and three retrospective studies were identified with a total of 210 patients with mean follow up of 40.6 months. All papers were analysed for quality using the modified Newcastle Ottawa score. The results show that dorsal bridge plating is associated with better American Orthopaedic Foot and Ankle Society score (AOFAS) compared with transarticular screw fixation (OR - 0.71, 95% CI -1.31 to -0.10, p = 0.02). Dorsal plating may also be associated with fewer cases of arthritis, although this was not significant (OR 2.46, 95% CI 0.89 to 6.80, p = 0.08). We found no significant differences between the groups in terms of Foot Function Index (FFI), post traumatic arthritis and failure of hardware material. Although our results suggest dorsal bridge plating may provide superior functional outcomes, there is a scarcity of literature with little robustness to make definitive conclusions. High quality randomised trials are required.

Comparison of Atlantoaxial Fusion with Transarticular Screws and C1 Lateral Mass-C2 Screws Using Intraoperative O-Arm Navigation.

OBJECTIVE: This study compared the surgical outcomes of atlantoaxial fusion with transarticular screws (TASs) and C1 lateral mass-C2 screws (screw-rod constructs [SRCs]) using the intraoperative O-arm navigation system (O-arm). METHODS: Among a total of 28 patients who underwent atlantoaxial fixation, 13 underwent TAS fixation and 15 underwent SRC fixation using the O-arm. All patients underwent Brooks procedure with iliac bone graft in addition to screw fixation. TAS fixation was performed for cases without high-riding vertebral artery (hVA). In the SRC group, pars or lamina screws were inserted for the side with a C2 hVA. Operative time, intraoperative bleeding, perioperative complications, screw accuracy, and bone union were evaluated. RESULTS: There were statistically significant differences in mean operative time between the 2 procedures (166 minutes in the TAS group vs. 212 minutes in the SRC group, P < 0.05) and in mean blood loss (80 vs. 185 mL, respectively; P < 0.01). Two patients developed temporary postoperative occipital neuralgia probably related to C2 nerve root in the SRC group. No screws violated the cortex in either group. Complete bone union was observed in all cases. CONCLUSIONS: O-arm-assisted TAS fixation had less intraoperative blood loss, shorter operative time, and fewer screw insertion complications than O-arm-assisted SRC fixation. O-arm-assisted TAS fixation is preferable for atlantoaxial fusion in patients without hVA.

Recurrent traumatic atlantoaxial rotatory subluxation: Case report.

INTRODUCTION: Atlantoaxial rotatory subluxation (AARS) is not uncommon in paediatric emergencies, however, the complications might be fatal. Long onset before presentation is correlated with higher recurrence and persistent deformity. There is no consensus on the treatment of AARS yet. Selected patients may benefit from conservative approaches; however, retention might be difficult, and subluxation may recur. PRESENTATION OF CASE: A 6-year-old boy was admitted to our institution with AARS for three months before admission. Typical Cock-Robin position was observed. Computed tomography (CT) indicated AARS Fielding and Hawkins grade III. We treated the case conservatively by closed reduction and cervical traction using Gardner-Wells tongs. However, poor compliance resulted recurrence of subluxation, so we decided to fuse the atlantoaxial joint using transarticular screws, posterior wiring, and autologous bone grafting. Posterior fusion resulted in a satisfactory outcome, in which the wound healed accordingly. Six months of follow up examination revealed normal motoric and sensory function. The patient was able to perform daily activities with no significant issues. DISCUSSION: Patients with fixed deformity of more than three weeks have a higher rate for recurrence or persistent deformity, as reduction is harder and difficult to maintain. The use of posterior wiring alone is limited in maintaining reduction, while using transarticular screws alone is considered better in maintaining reduction; however, not providing it. CONCLUSION: The use of posterior cervical fusion using C-wire, transarticular screws, and autologous bone grafting may be applied in recurrent case of AARS to ensure adequate reduction and fixation of the atlantoaxial joint.