Correção de fratura Salter-Harris tipo I em porquinho-da-índia (Cavia porcellus) - relato de caso / [Correction of Salter-Harris type 1 fracture in guinea pig (Cavia porcellus) - case report]

Um filhote de porquinho-da-índia (Cavia porcellus) foi recebido para atendimento após histórico de ataque por cão. Na avaliação física, observou-se edema, dor e crepitação em membro pélvico direito, sugestivo de fratura. Na avaliação radiográfica, confirmou-se fratura Salter-Harris tipo I em epífise distal da tíbia. A resolução cirúrgica escolhida foi a associação de pino transarticular e coaptação externa com tala de Altman. O paciente teve acompanhamento radiográfico semanal e obteve alta médica no 35o dia de pós-cirúrgico, quando se observou consolidação com completo remodelamento ósseo.(AU)

A guinea pig (Cavia porcellus) cub presented edema, pain, and crepitus in the right pelvic limb after being attacked by a dog. Radiographic examination revealed Salter-Harris type 1 fracture on the distal region of the tibia. The surgery technique to correct the fracture involved an association of transarticular pinning and external coaptation with Altman splint. After surgery, radiographs of the patient were performed weekly and on the 35th post-surgery day, the bone was completely remodeled and healed, and the animal was dismissed.(AU)

Anatomic Considerations of Anterior Transarticular Screw Fixation for Atlantoaxial Instability

STUDY DESIGN: Cadaveric, observational study.PURPOSE: Atlantoaxial instability (AAI) is characterized by excessive movement at the C1–C2 junction between the atlas and axis. An anterior surgical approach to expose the upper cervical spine for internal fixation and bone grafting has been developed to fix AAI. Currently, no anatomic information exists on the anterior transarticular atlantoaxial screw or screw and plate fixation between C1 and C2 in the Indian population. The objective of this study is to assess the anatomic landmarks of C1–C2 vertebrae: entry point, trajectory, screw length, and safety of the procedure.OVERVIEW OF LITERATURE: Methods outlined by Magerl and Harms are the optimal approaches among the dorsal techniques. Contraindications for these techniques include aberrant location of vertebral arteries, fractures of C1–C2 posterior structures. In these cases, anterior transarticular fixation is an alternative. Several available screw insertion trajectories have been reported. Biomechanical studies have demonstrated that adequate rigidity of this fixation is comparable with posterior fusion techniques.METHODS: Direct measurements using Vernier calipers and a goniometer were recorded from 30 embalmed human cadavers. The primary parameters measured were the minimum and maximum lateral and posterior angulations of the screw in the sagittal and coronal planes, respectively, and optimum screw length, if it was placed accurately.RESULTS: The posterior and lateral angles of screw placement in the coronal and sagittal planes ranged from 16° to 30° (mean±standard deviation [SD], 23.93°±3.93°) and 8° to 17° (mean±SD, 13.3°±2.26°), respectively. The optimum screw length was 25–38 mm (mean±SD, 28.76±3.69 mm).CONCLUSIONS: If the screw was inserted without lateral angulation, the spinal canal or cord could be violated. If a longer screw was inserted with greater posterior angulation, the vertebral artery at the posterior or posterolateral aspect of the C1 superior facet could be violated. Thus, 26° and 30° of lateral and posterior angulations, respectively, are the maximum angles permissible to avoid injury of the vertebral artery and violations of the spinal canal or atlanto-occipital joint.

Posterior Sublaminar Wiring and/or Transarticular Screw Fixation for Reducible Atlantoaxial Instability Secondary to Symptomatic Os Odontoideum: A Neglected Technique?

STUDY DESIGN: Retrospective case analysis. PURPOSE: We retrospectively evaluated the clinical and radiological outcomes of posterior sublaminar wiring (PSLW) and/or transarticular screw fixation (TASF) for reducible atlantoaxial instability (AAI) secondary to os odontoideum. OVERVIEW OF LITERATURE: Limited information is available about the surgical outcomes of symptomatic os odontoideum with AAI. METHODS: We examined 23 patients (12 women and 11 men) with os odontoideum and reducible AAI. The average age of the patients at the time of the operation was 44.2 years. The average follow-up duration was 4.5 years. Thirteen patients with anterior AAI underwent PSLW alone, while 10 patients with combined (anterior+posterior) AAI underwent PSLW and TASF. An autogenous iliac bone graft was used for all patients. Nine patients complained of neck or suboccipital pain, and 14 complained of myelopathy. RESULTS: Angulational instability (preoperative 18.7°±8.9° vs. postoperative 2.1°±4.6°, p<0.001), translational instability (16.3±4.9 mm vs. 1.8±2.2 mm, p<0.001), and segmental angle of the C1–C2 joint (23.7°±7.2° vs. 28.4°±3.8°, p<0.05) showed significant improvement postoperatively. Neck Visual Analog Scale score (6.2±2.4 vs. 2.5±1.8, p<0.05) and the modified Japanese Orthopedic Association (9.1±3.1 vs. 13.2±2.6, p<0.05) score also improved, with a recovery rate of 51.8%. Among the three patients who developed nonunion and/or wire breakage, one underwent revision surgery with repeat PSLW and was finally able to achieve fusion. The final fusion rate was 91.3%. CONCLUSIONS: PSLW and/or TASF provided satisfactory clinical and radiological outcomes in reducible AAI secondary to os odontoideum without significant neurological complications. Our results suggest that PSLW and/or TASF can be considered a viable surgical option over segmental fixation in highly selected cases of os odontoideum with reducible AAI.

Axis Screw Fixation ­ A Step-by-Step Review of the Surgical Techniques

In this article, we present the techniques of axis screw fixation (laminar, pars, pedicle and transarticular screws), discussing the indications and contraindications of each one, as well as surgical tips and anatomical landmarks.

No presente artigo, apresentamos as técnicas de fixação do áxis com parafusos (lamina, parafusos de pars, pedículo e transarticular), discutindos as indicações e contraindicações das mesmas, assim como dicas cirúrgicas e parâmetros anatômicos relevantes.

Caudoventral hip luxation in a miniature pig / Luxação caudoventral de quadril em um mini-pig

ABSTRACT: A miniature pig was examined because of left pelvic limb lameness after falling from a short height. Clinical examination and radiographs of the pelvic region revealed a left caudoventral hip luxation. Surgical reduction of luxation was performed on the patient under general anesthesia using a transarticular pinning technique. Postoperative radiographs confirmed that the luxation was reduced, the joint was aligned, and the transarticular pinning was correct. The transarticular pin was removed 21 days after it was surgically inserted. The limb was fully functional in the immediate postoperative period. Nine months after the surgery, the patient could use the limb properly, but mild degenerative joint disease was observed via radiographic follow-up. This technique may be a viable treatment option for the repair of caudoventral hip luxation in miniature pigs.

RESUMO: Um mini-pig foi atendido devido à claudicação do membro pélvico esquerdo após pequena queda. O exame clínico e radiografias da região pélvica revelaram uma luxação caudoventral de quadril no lado esquerdo. A redução cirúrgica da luxação foi realizada, com o paciente sob anestesia geral, usando um pino transarticular. As radiografias pós-operatórias confirmaram que a luxação foi reduzida, com alinhamento e fixação transarticular corretos. O pino transarticular foi removido cirurgicamente 21 dias após de ter sido inserido. O membro se tornou totalmente funcional já no período pós-operatório imediato. Nove meses após a cirurgia, o paciente utilizava o membro corretamente, porém foi detectada doença articular degenerativa leve através de acompanhamento radiográfico. A técnica empregada foi uma opção viável de tratamento para a reparação da luxação caudoventral de quadril em mini-pig.

Challenges of Transarticular Screw Fixation in Young Children: Report of Surgical Treatment of a 5-Year-Old Patient's Unstable Os-Odontoideum

Surgical procedures for atlantoaxial (C1–C2) fusion in young children are relatively uncommon. The purpose of this study was to report on a surgical treatment for a case of atlantoaxial instability caused by os-odontoideum in association with quadriparesis and respiratory paralysis in a 5-year-old girl. We present the patient's history, physical examination, and radiographic findings, describe the surgical treatment and a five year follow-up, and provide a literature review. The instability was treated by halo immobilization, followed by C1–C2 transarticular screw fixation using a computed tomography-based navigation system. At the five year follow-up, the patient had made a complete recovery with solid union. The authors conclude that C1–2 transarticular screw fixation is technically possible as in a case of atlantoaxial instability in a five-year-old child.

C2-3 Fusion, C3-4 Cord Compression and C1-2 Posterior Facetal Instability: An Evaluation of Treatment Strategy Based on Four Surgically Treated Cases

STUDY DESIGN: Four patients had C2-3 vertebral fusion and radiologically demonstrated cord compression at C3-4 level related to disc bulge with or without association of osteophytes and C1-2 posterior facetal dislocation. The outcome of treatment by atlantoaxial and subaxial facetal fixation is discussed. PURPOSE: The article evaluates the significance of atlantoaxial facetal instability in cases having C2-3 vertebral fusion and cord compression at the level of C3-4 disc. OVERVIEW OF LITERATURE: C2-3 vertebral fusions are frequently encountered in association with basilar invagination and chornic atlantoaxial dislocations. Even when basilar invagination and atlantoaxial dislocation are not identified by conventional parameters, atlantoaxial instability can be the nodal point of pathogenesis in cases with C2-3 vertebral fusion. METHODS: Between June 2013 and November 2014 four patients having C2-3 fusion presented with progressive symptoms of myelopathy that were related to cord compression at the level opposite the C3-4 disc space. Further investigations revealed C1-2 posterior facetal dislocation. RESULTS: All patients were males. Ages ranged from 18 to 50 years (average, 36 years). All patients were treated by atlantoaxial facetal plate and screw, and subaxial single or multi-segmental transarticular screw fixation. Follow-up (average, 15 months) using a recently described clinical grading system and the Japanese Orthopaedic Association scoring system confirmed marked improvement of symptoms. CONCLUSIONS: Identification and treatment of atlantoaxial facetal instability may be crucial for a successful outcome in cases having C2-3 fusion and high cervical (C3-4) disc related cord compression.

C2-3 Fusion, C3-4 Cord Compression and C1-2 Posterior Facetal Instability: An Evaluation of Treatment Strategy Based on Four Surgically Treated Cases

STUDY DESIGN: Four patients had C2-3 vertebral fusion and radiologically demonstrated cord compression at C3-4 level related to disc bulge with or without association of osteophytes and C1-2 posterior facetal dislocation. The outcome of treatment by atlantoaxial and subaxial facetal fixation is discussed. PURPOSE: The article evaluates the significance of atlantoaxial facetal instability in cases having C2-3 vertebral fusion and cord compression at the level of C3-4 disc. OVERVIEW OF LITERATURE: C2-3 vertebral fusions are frequently encountered in association with basilar invagination and chornic atlantoaxial dislocations. Even when basilar invagination and atlantoaxial dislocation are not identified by conventional parameters, atlantoaxial instability can be the nodal point of pathogenesis in cases with C2-3 vertebral fusion. METHODS: Between June 2013 and November 2014 four patients having C2-3 fusion presented with progressive symptoms of myelopathy that were related to cord compression at the level opposite the C3-4 disc space. Further investigations revealed C1-2 posterior facetal dislocation. RESULTS: All patients were males. Ages ranged from 18 to 50 years (average, 36 years). All patients were treated by atlantoaxial facetal plate and screw, and subaxial single or multi-segmental transarticular screw fixation. Follow-up (average, 15 months) using a recently described clinical grading system and the Japanese Orthopaedic Association scoring system confirmed marked improvement of symptoms. CONCLUSIONS: Identification and treatment of atlantoaxial facetal instability may be crucial for a successful outcome in cases having C2-3 fusion and high cervical (C3-4) disc related cord compression.

Comparison of Outcomes after Atlantoaxial Fusion with Transarticular Screws and Screw-Rod Constructs

OBJECTIVE: The purpose of this study was to compare the radiological and neurological outcomes between two atlantoaxial fusion method for atlantoaxial stabilization; C1 lateral mass-C2 pedicle screws (screw-rod constructs, SRC) versus C1-2 transarticular screws (TAS). METHODS: Forty-one patients in whom atlantoaxial instability was treated with atlantoaxial fixation by SRC group (27 patients, from March 2005 to May 2011) or TAS group (14 patients, from May 2000 to December 2005) were retrospectively reviewed. Numeric rating scale (NRS) for pain assessment, Oswestry disability index (ODI), and Frankel grade were also checked for neurological outcome. In radiologic outcome assessment, proper screw position and fusion rate were checked. Perioperative parameters such as blood loss during operation, operation time, and radiation exposure time were also reviewed. RESULTS: The improvement of NRS and ODI were not different between both groups significantly. Good to excellent response in Frankel grade is shown similarly in both groups. Proper screw position and fusion rate were also observed similarly between two groups. Total bleeding amount during operation is lesser in SRC group than TAS group, but not significantly (p=0.06). Operation time and X-ray exposure time were shorter in SRC group than in TAS group (all p<0.001). CONCLUSION: Both TAS and SRC could be selected as safe and effective treatment options for C1-2 instability. But the perioperative result, which is technical demanding and X-ray exposure might be expected better in SRC group compared to TAS group.

Removal of irretrievable segmentally broken femur nail by an innovative technique – Case Report.

Extraction of broken implant is a challenging task for orthopaedic surgeons. Many times it requires innovative ideas or some unusual methods, all of which has not been listed in literature. We hereby report such a case of 40-year-old male who presented with severe limping and history of previously treated right femur fracture. The radiographs showed an intramedullary nail which was segmentally broken. Femur nail was broken at the non-united fracture and below the fracture at the level of distal interlocking screw. We successfully removed a broken implant by using such one innovative -close retrograde method. The segments of broken nail were removed through knee arthrotomy without opening the fracture site. Non-union was treated by exchange nailing without bone grafting and patient recovered well on follow up. To our best of knowledge very few cases of extraction of segmentally fractured nail have been reported in literature until now.

Deviation factors of posterior atlantoaxial transarticular screw placement assisted by rapid prototyping drill templates / 中华创伤杂志

Objective To validate the safety and accuracy of a rapid prototyping drill template (RPDT) for posterior atlantoaxial transarticular screw placement and analyze factors for screw deviation.Methods Twelve normal cadaveric cervical spines were examined using 64 slice CT with 1-mm thick scan and data in Dicom format were recorded.After data was processed using software Mimics 10.01 for three-dimensional (3-D) model reconstruction,computer-assisted design of optimum trajactory for atlantoaxial transarticular screw placement was worked out and made into a drill template,where the surface was created as the inverse of axial posterior surface.The drill template was materialized in a rapid prototyping machine and used to place the screws.After surgery,the position of posterior atlantoaxial transarticular screw was evaluated by X-ray and CT scan.Screw entry point,angle and orientation of the optimal and actual trajactory were determined after fitting the position of the pre-operative and post-operative specimen in computer software and the redefining the 3-D coordinate axis.Results Twenty-four screws were implanted with no cortex perforation.Depth of the optimum save screw trajectory for atlantoaxial transarticular fixation was (37.34 ± 2.31) mm on the left side and (37.11 ± 2.21) mm on the right side.Introversion angles of the optimum save screw trajectory was 0° in both sides,but the actual angle was (0.15 ±0.58)°on the left side and (0.11 ±0.46)°on the right side.Elevation angle of the optimum save screw trajectory was (49.35 ± 1.62) °on the left side and (48.83 ± 1.83) ° on the right side,but the actual angle was (49.29 ± 1.68) °and (49.10 ± 1.45) °respectively.Average displacement of screw entry point in the x,y and z axis was respective (0.21 ±0.65) mm,(0.69 ± 1.48) mm and (0.39 ±0.11) mm on the right side,while (0.19 ± 0.66) mm,(0.53 ± 1.45) mm and (0.38 ± 0.13) mm on the left side.There were no statistically significant differences in deviation levels of entry point and orientation between the optimum and actual screw trajectory (P ＞ 0.05).Conclusions Causes for deviation in RPDT-assisted placement of atlantoaxial transarticular screw are mainly intrinsic factors of the hardware and software and human factors in the operation.RPDT is easy in operation and has individualized design,which greatly improves the accuracy of screw placement and reduces screw deviation.RPDT can be widely used in clinical practice.

Intraoperative Vertebral Artery Angiography to Guide C1-2 Transarticular Screw Fixation in a Patient with Athetoid Cerebral Palsy

We present a case of an athetoid cerebral palsy with quadriparesis caused by kyphotic deformity of the cervical spine, severe spinal stenosis at the cervicomedullary junction, and atlantoaxial instability. The patient improved after the first surgery, which included a C1 total laminectomy and C-arm guided righ side unilateral C1-2 transarticular screw fixation. C1-2 fixation was not performed on the other side because of an aberrant and dominant vertebral artery (VA). Eight months after the first operation, the patient required revision surgery for persistent neck pain and screw malposition. We used intraoperative VA angiography with simultaneous fluoroscopy for precise image guidance during bilateral C1-2 transarticular screw fixation. Intraoperative VA angiography allowed the accurate insertion of screws, and can therefore be used to avoid VA injury during C1-2 transarticular screw fixation in comorbid patients with atlantoaxial deformities.

Computer-assisted C1-C2 Transarticular Screw Fixation "Magerl Technique" for Atlantoaxial Instability

STUDY DESIGN: A retrospective study. PURPOSE: To evaluate the surgical results of computer-assisted C1-C2 transarticular screw fixation for atlantoaxial instability and the usefulness of the navigation system. OVERVIEW OF LITERATURE: We used a computed tomography (CT)-based computer navigation system in planning and screw insertion in Magerl's procedure, which provides the most rigid atlantoaxial fusion, to avoid risk of vertebral artery (VA) tear by avoiding high-riding VA during screw insertion. METHODS: Twenty patients who underwent atlantoaxial fusion under the CT-based navigation system were studied. The mean observation period was 33.5 months. The evaluated items included the existence of VA stenosis by preoperative magnetic resonance angiography, surgical time, blood loss volume, Japanese Orthopaedic Association (JOA) score and Ranawat's pain criteria before surgery and at final follow-up, postoperative screw position evaluated by CT, and bony fusion. RESULTS: The mean operation time was 205 minutes, with the mean blood loss volume of 242 ml. The mean JOA score was 11.6 points before surgery and 13.7 at final follow-up. Occipital and/or cervical pain presented before operation was remitted or resolved in all patients. Evaluation of screw insertion by CT revealed correct penetration to atlantoaxial joints, with a perforation rate of 2.6%. There was no complication, including VA tear, and all patients who were followed-up during one year or more after surgery achieved bony fusion. Some subjects who appeared inappropriate for surgery from CT images were assessed as eligible for surgery based on the evaluation results obtained using the navigation system. CONCLUSIONS: It was demonstrated that the CT-based navigation system is an effective support device for Magerl's procedure.

Ewing sarcoma of the left big toe with trans-articular skip lesion: A case report.

We report the case of the patient who had Ewing Sarcoma in whom radiological and hystopathological appearances revealed a tumor mass in the left big toe along with trans-artikular skip lesion on the left diaphysis of tibia. In Cipto Mangunkusomo Hospital since 1995 until 2004 we have found 20 Ewing sarcoma cases, but only one skip lesion Ewing sarcoma was found. The diagnosis of transarticular skip lesion in association of Ewing sarcoma was confirmed in clinicopathological conferrence. The initial evaluation of all patients included the recording of the medical history, physical examination, and hematological studies. Radiographs of the chest and the site of the primary tumor were made routinely. Systemic staging was performed with use of total-body bone scan. Ray amputation of left big toe and open biopsy from mass of mid-shaft of tibia had been done to confirm the diagnosis. The patient underwent induction chemotherapy and above knee amputation. Ten months after diagnosis, he died because of advanced-distant metastasis.

Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability : Comparison with Bilateral Method

OBJECTIVE: Bilateral C1-2 transarticular screw fixation (TAF) with interspinous wiring has been the best treatment for atlantoaxial instability (AAI). However, several factors may disturb satisfactory placement of bilateral screws. This study evaluates the usefulness of unilateral TAF when bilateral TAF is not available. METHODS: Between January 2003 and December 2007, TAF was performed in 54 patients with AAI. Preoperative studies including cervical x-ray, three dimensional computed tomogram, CT angiogram, and magnetic resonance image were checked. The atlanto-dental interval (ADI) was measured in preoperative period, immediate postoperatively, and postoperative 1, 3 and 6 months. RESULTS: Unilateral TAF was performed in 27 patients (50%). The causes of unilateral TAF were anomalous course of vertebral artery in 20 patients (74%), severe degenerative arthritis in 3 (11%), fracture of C1 in 2, hemangioblastoma in one, and screw malposition in one. The mean ADI in unilateral group was measured as 2.63 mm in immediate postoperatively, 2.61 mm in 1 month, 2.64 mm in 3 months and 2.61 mm in 6 months postoperatively. The mean ADI of bilateral group was also measured as following; 2.76 mm in immediate postoperative, 2.71 mm in 1 month, 2.73 mm in 3 months, 2.73 mm in 6 months postoperatively. Comparison of ADI measurement showed no significant difference in both groups, and moreover fusion rate was 100% in bilateral and 96.3% in unilateral group (p=0.317). CONCLUSION: Even though bilateral TAF is best option for AAI in biomechanical perspectives, unilateral screw fixation also can be a useful alternative in otherwise dangerous or infeasible cases through bilateral screw placement.

Posterior Atlantoaxial Transarticular Screw Fixation

OBJECTIVE: Posterior arthrodesis in atlantoaxial instability has been performed using various posterior C1-2 wiring techniques. Recently, transarticular screw fixation (TASF) technique was introduced to achieve significant immediate stability of the C1-2 joint complex. The purpose of this study is to assess the clinical outcomes associated with posterior C1-2 TASF for the patient of atlantoaxial instability. METHODS: We retrospectively reviewed data obtained from 17 patients who underwent C1-2 TASF and supplemented Posterior wiring technique (PWT) with graft between 1994 and 2005. There were 8 men and 9 women with a mean age of 43.5 years (range, 12-65 years). An average follow-up was 26 months (range, 15-108 months). RESULTS: Successful fusions were achieved in 16 of 17 (94%). The pain was improved markedly (3 patients) or resolved completely (14 patients). There was no case of neurological deterioration, hypoglossal nerve injury, or vertebral artery injury. Progression of spinal deformity, screw pullout or breakage, and neurological or vascular complications did not occur. CONCLUSION: The C1-2 TASF with supplemental wiring provided a high fusion rate. Our result demonstrates that C1-2 TASF supplemented by PWT is a safe and effective procedure for atlantoaxial instability. Preoperative evaluation and planning is mandatory for optimal safety.

Posterior Atlantoaxial Transarticular Screw Fixation

OBJECTIVE: Posterior arthrodesis in atlantoaxial instability has been performed using various posterior C1-2 wiring techniques. Recently, transarticular screw fixation (TASF) technique was introduced to achieve significant immediate stability of the C1-2 joint complex. The purpose of this study is to assess the clinical outcomes associated with posterior C1-2 TASF for the patient of atlantoaxial instability. METHODS: We retrospectively reviewed data obtained from 17 patients who underwent C1-2 TASF and supplemented Posterior wiring technique (PWT) with graft between 1994 and 2005. There were 8 men and 9 women with a mean age of 43.5 years (range, 12-65 years). An average follow-up was 26 months (range, 15-108 months). RESULTS: Successful fusions were achieved in 16 of 17 (94%). The pain was improved markedly (3 patients) or resolved completely (14 patients). There was no case of neurological deterioration, hypoglossal nerve injury, or vertebral artery injury. Progression of spinal deformity, screw pullout or breakage, and neurological or vascular complications did not occur. CONCLUSION: The C1-2 TASF with supplemental wiring provided a high fusion rate. Our result demonstrates that C1-2 TASF supplemented by PWT is a safe and effective procedure for atlantoaxial instability. Preoperative evaluation and planning is mandatory for optimal safety.

Measurement of the Axial Isthmus for Atlantoaxial Transarticular Screw Fixation / 대한해부학회지

Pre-operative evaluation of the anatomy of the axis, such as the size and angle of the axial isthmus, is very important to minimize complications in atlantoaxial transarticular screw fixation. To provide basic data useful for atlantoaxial transarticular screw fixation in Korean, the width and height of the axial isthmus as well as ideal insertion angle of the screw were measured in this study. Fifty seven (male, 36; female, 21) dried axes obtained from Korean adult cadavers, 60.5 years old in average, were used. The shortest distance in the width and height of the axial isthmus was measured at the level of transverse foramen by using Vernier calliper. The ideal screw insertion angle was set up as an angle between a parasagittal line and the line passing through the center of the isthmus and screw insertion point which is located 2 mm lateral to and 3 mm superior to the posteromedial end of the inferior articular surface of the axis. The mean width of the axial isthmus was 8.14 mm (8.42 mm in male; 7.86 mm in female) in the right and 8.46 mm (8.80 mm in male; 8.12 mm in female) in the left side, and 8.61 mm in male and 7.99 mm in female. Although the width of the axial isthmus was slightly greater in the left and in male, there was no significant difference between both sides or sexes. The mean height of the axial isthmus was 7.17 mm (7.49 mm in male; 6.84 mm in female) in the right and 7.43 mm (7.90 mm in male; 6.96 mm in female) in the left side, and 7.69 mm in male and 6.90 mm in female. However there was no significant difference between both sides or sexes, as like in the width. In the atlantoaxial transarticular screw fixation, the axis with isthmus lesser than 5 mm in its width or height is regarded as risk group in general. The frequency of the risk group in the width was 3.5% (2 cases) in the right and 1.8% (1 case) in the left, while that in the height was 8.8% (5 cases) in the right and 7.0% (4 cases) in the left. The mean ideal insertion angle of the screw was 5.6 degrees, 4.4 degrees in the right and left side of male, and 4.7 degrees, 5.5 degrees in the right and left side of female respectively. However the insertion angle dispersed over a wide range between 0 degree ~ 12 degrees. In conclusion, measurement of the isthmus height and insertion angle, besides the isthmus width, should be involved in the pre-operative examination, to minimize complications during the atlantoaxial transarticular screw fixation.

Biomechanical comparison between artificial atlanto-odontoid joint replacament and Magerl transarticular screw fixation / 中国矫形外科杂志

[Objective]To determine the initial stability and function of a new artificial joint in a cadaveric cervical spine model by comparing it with a conventional method. [Methods]Twelve fresh human cadaveric cervical spines(C0~3) were randomly divided into 2 groups: group 1,resection of the odontoid with artificial atlanto-odontoid joint(AAOJ),and group 2,resection of the odontoid with Magerl atlas and axis by transarticular screw fixation(Magerl).For each specimen,the intact and resection of the odontoid underwent a flexibility test firstly,followed by the instrumented construct.Rotational angles of the C0~3 segment were measured to study the immediate stability and function of resection of the odontoid and AAOJ,compared with the intact and resection of the odontoid and Magerl.[Results]Compared to the intact state,resection of the odontoid and AAOJ resulted in a significant decrease in the range of motion(ROM) and neutral zone(NZ) during flexion,extension,and lateral bending(P0.05).Compared to the intact state,resection of the odontoid and Magerl resulted in a significant decrease in the range of motion(ROM) and neutral zone(NZ) during all 6 degrees of freedom(P0.05).[Conclusion]A new type of artificial atlanto-odontoid joint has been designed for correcting atlantoaxial instability resulted from C1、2 anterior decompression procedures.It can restore,to a great extent,the C1、2 axial rotation that is lost during current stabilization procedures.

Anatomic relationship of vertebral artery and screw trajectory of posterior atalanto-axial transarticular screw fixation / 中国矫形外科杂志

[Objective]To study the screw trajectory in the posterior atalanto-axial transarticular screw fixation.[Methods](1)The anatomical parameters related to the screw fixation were measured on 30 paired dry atlantoaxial specimens;(2)The X ray and CT scan were taken after C1、2 was fixed by posterior transarticular screws on 6 cadavers.These iterms were used to explore the anatomical relation of the vertebral artery and the screw trajectory in the posterior C1、2 fixation.[Results]The depth of the vertebral artery groove on the inferior surface of the superior facet of the axial was(5.86 1.45)mm;the vertebral artery groove extented the superior facet up to its medial third in 15 sides,up to the middle third and its lateral third respective in 35 and 9 sides,and the ideal screw trajectory medial angle of these specimens were(26.4?3.44)?,(16.1?2.44)?,(15.1?2.24)? respectively。The shortest distance between the vertebral artery and the screw trajectory lied in the topmost point of the vertebral artery groove of the axial on CT images,and the interval was(2.75～5.78)mm.[Conclusion]The position of vertebral artery groove of the axial is the key to decide the angle of the screw trajectory.The shortest interval between screw trajectory and vertebral artery,safe for posterior atalanto-axial transarticular screw fixation,locates on the inferior surface of the superior facet of the axial.