C2 Translaminar Screw Fixation Research Articles

C2 translaminar screw fixation in pediatric occipitocervical fusion

PurposeRigid occipitocervical (O-C) instrumentation can reduce the anterior pathology and has a high fusion rate in children with craniovertebral instability. Typically, axis (C2) screw fixation utilizes C1–C2 transarticular screws or C2 pars screws. However, anatomic variation may preclude these screw types due to the size of fixation elements or by placing the vertebral artery at risk for injury. Pediatric C2 translaminar screw fixation has low risk of vertebral artery injury and may be used when the anatomy is otherwise unsuitable for C1–C2 transarticular screws or C2 pars screws.MethodsWe retrospectively reviewed a neurosurgical database at UCSF Benioff Children’s Hospital Oakland for patients who had undergone a cervical spinal fusion that utilized translaminar screws for occipitocervical instrumentation between 2002 and 2020. We then reviewed the operative records to determine the parameters of C2 screw fixations performed. Demographic and all other relevant clinical data were then recorded.ResultsTwenty-five patients ranging from 2 to 18 years of age underwent O-C fusion, with a total of 43 translaminar screws at C2 placed. Twenty-three patients were fused (92%) after initial surgery with a mean follow-up of 43 months. Two patients, both with Down syndrome, had a nonunion. Another 2 patients had a superficial wound dehiscence that required wound revision. One patient died of unknown cause 7 months after surgery. One patient developed an adjacent-level kyphosis.ConclusionWhen performing occipitocervical instrumentation in the pediatric population, C2 translaminar screw fixation is an effective option to other methods of C2 screw fixation dependent on anatomic feasibility.

Bicortical Short C2 Pars Screw Fixation for High-Riding Vertebral Artery Provided Sufficient Biomechanical Stability: A Finite Element Study.

Finite element analysis. To determine and compare the biomechanical stability of the bicortical short C2 pars screw fixation for high-riding vertebral artery (HRVA) with the C2 pedicle screw and C2 translaminar screw fixation in finite element models. Fixation of C2 is technically demanding in the case of HRVA. However, there is no consensus on the alternative technique for the C2 screw fixation for HRVA in the literature. A finite element model of the upper cervical spine (C0-C2) with HRVA had been developed. C1 pedicle screw was applied at C1 by using notching technique. Bicortical short C2 pars screws, C2 pedicle screws, and C2 translaminar screws were used in each model. Then a vertical load of 50 N and a 1.5 Nm torque were applied to the C0 to simulate flexion, extension, lateral bending, and axial rotation respectively. Compared with C2 pedicle screw fixation, the bicortical short C2 pars screw fixation increased the range of motion by -1.45%, 2.13%, 62.0%, and 22.0% under flexion, extension, lateral bending, and axial rotation, respectively. However, the C2 translaminar screw fixation increased the range of motion by 43.6%, 17.8%, 423.4%, and 19.9%, respectively. In terms of the peak von Mises stress, compared with C2 pedicle screw fixation, bicortical short C2 pars screw decreased 46.1%, 41.6%, 71.3%, and -12.5% under flexion, extension, lateral bending, and axial rotation, respectively; C2 translaminar screw decreased -2.66%, -4.87%, 73.0%, and -10.1%, respectively. For a patient with HRVA, bicortical short C2 pars screw fixation provides sufficient stability and exhibited a smaller von Mises distribution on the screw-rod construct, indicating it could be an effective C2 internal fixation method for HRVA to promote C1-C2 stability and avoid the vertebral artery injury.Level of Evidence: N/A.

Lamina Measurements with Computed Tomography for C2 Translaminar Screw Fixation in Pediatric and Adult Cases.

To measure C2-related morphometric parameters in a Turkish population. The computed tomography (CT) images of three groups (Group 1: paediatric cases aged 1-6 years, Group 2: age7-16 years, and Group 3: adult cases), who had cervical spine CT were used to measure some morphometric parameters for safe C2 translaminar screw fixation. The measured parameters included thickness, height and length of the C2 lamina on both sides and the C2 lamina-midline angle. C2 lamina thickness at the thinnest point on the right and left sides was found to be 4.4 ± 0.5 mm and 4.6 ± 0.5 mm in Group 1, 5.3 ± 0.8 mm and 5.6 ± 0.8 mm in Group 2, and 6.8 ± 1.4 mm and 7.0±1.5 mm in Group 3, respectively (p > 0.05). The height of the C2 lamina at the thinnest point on the right and left sides was found to be 5.8 ± 0.8 mm, and 5.8 ± 0.7 mm in Group 1,10.4 ± 1.4 mm and 10.6 ± 1.4 mm in Group 2, and 10.6 ± 1.8 mm, and 10.7 ± 1.5 mm in Group 3, respectively (p > 0.05). The mean length of the C2 lamina was found to be 20.6 ± 2.4 mm in Group 1, 31.4 ± 4.1 mm in Group 2, and 36.7 ± 3.3 mm in Group 3 (p < 0.05). There was no significant difference between Group 2 and Group 3 in respect of mean lamina angle (44&ordm; vs 45&ordm;) but it was lower in Group 1 (35&ordm;). This study revealed the appropriateness of C2 anatomy for safe C2 translaminar screw fixation.

C2 Translaminar Screw Fixation (Wright`s Technique) Applicability in Atlantoaxial Instability

Atlantoaxial instability often requires surgical treatment. Several techniques are available to perform antlantoaxial stabilization, and all of these have their different advantages and disadvantages. In 2004, Wright described the C2translaminar screw fixation, which offers rigid fixation but without the technical demands of C2 pars placement and eliminates the risk of vertebral artery injury. The aim of this study is to review the C2 translaminar screw fixation technique, emphasizing operative details, risks and benefits comparing with the others atlantoaxial fixation techniques.

Computed tomography morphometric analysis of C2 translaminar screw fixation of Wright’s technique and a modified technique in the pediatric cervical spine

To establish reference data on the dimensions of C2 lamina to guide the use of translaminar screws with Wright's technique and a modified technique for pediatric patients in different age groups. 113 pediatric patients were divided into six age groups, and their cervical vertebrae were studied on CT scans. Laminar height, width, length and screw angle were measured. Statistical analysis was performed using Student t tests, Pearson's correlation and linear regression analysis. Mean laminar height was 10.95 ± 2.81 mm, and mean width was 6.01 ± 0.90 mm. For Wright's technique, mean laminar length was 30.65 ± 3 mm, and the screw angle was 56.02° ± 3.62°. For the modified technique, mean laminar length was 22.07 ± 2.38 mm, and the screw angle was 67.40° ± 3.39°. 95.6% (108/113) of the children could insert a screw into the lamina (laminar width ≥ 4.5 mm), 72.6% (82/113) could accept bilateral translaminar screws (laminar width ≥ 4.5 mm and laminar height ≥ 9 mm). Our investigation provides insight into the anatomy of C2 lamina in six pediatric age groups. Compared to adults, the benefits of C2 translaminar screws fixation are more obvious in the pediatric spine which has a large C2 lamina. Compared to Wright's technique, the modified technique should insert a screw with bigger insert angle and shorter screw length.

Translaminar screws of the axis—an alternative technique for rigid screw fixation in upper cervical spine instability

C2 pedicle screws or transarticular atlantoaxial screws are technically demanding and carry an increased risk of vertebral artery injury. In up to 20% of cases, pedicle and transarticular screw placement is not possible due to a high-riding vertebral artery or very small C2 pedicles in addition to other anatomical variations. Translaminar screws have been reported to rigidly capture posterior elements of C2 and therefore appear to be a suitable alternative. We present our first experiences and clinical results with this new method in two neurosurgical spine centers. Twenty-seven adult patients were treated between 2007 and 2010 in two neurosurgical spine departments with C2 translaminar screw fixation for upper cervical spine instability of various origins (e.g., trauma, tumor, dens pseudarthrosis). Eight patients were men and 19 were women. Mean age was 68.9years. In most cases, translaminar screws were used because of contraindications for pedicle or transarticular screws as a salvage technique. All patients were clinically assessed and had CT scans postoperatively to verify correct screw placement. Follow-up was performed with reexamination on an ambulatory basis. Mean follow-up was 7.6months for all patients. In 27 patients, 52 translaminar screws were placed. There were no intraoperative complications. Postoperatively, we identified four screw malpositions using a new accuracy grading scale. One screw had to be revised because of violation of the spinal canal >4mm. None of the patients had additional neurological deficits postoperatively, and all showed stable cervical conditions at follow-up. Two patients died due to causes not associated with the stabilization technique. The fusion rate for patients with C1/C2 fixation is 92.9%. Translaminar screws can be used at least as an additional technique for cases of upper cervical spine instability when pedicle screw placement is contraindicated or not possible. The current data suggest comparable biomechanical stability and fusion rates of translaminar screws to other well-known posterior fixation procedures. In addition, translaminar screw placement is technically less demanding and reduces the risk of vertebral artery injury.

Seven Years of Experience With C2 Translaminar Screw Fixation: Clinical Series and Review of the Literature

C2 translaminar screws offer biomechanical stability similar to that of other C2 fixation methods but with minimal risk to neural and vascular structures. To report our experience with the technique since 2002 and to review the pertinent literature to advance the understanding of C2 translaminar screw fixation. Fifty-two consecutive adult patients with disorders requiring axis stabilization were treated with C2 translaminar screws by a single surgeon. All patients underwent preoperative computed tomography scans to confirm the feasibility of screw placement. Patients were followed up with serial flexion/extension radiographs and/or computed tomography scans. The average age in our series was 58.1 years. One hundred three C2 translaminar screws were placed (average length, 28.9 mm). No vascular or neurological injuries occurred. Of 41 patients with sufficient follow-up (average, 13.3 months) to evaluate fusion, 1 instrumentation failure/pseudoarthrosis was observed. Five patients (average age, 78.7 years) died of complications related to medical comorbidities. In the literature, 169 cases of C2 translaminar fixation have been reported, with a fusion rate of 95.3% and no vertebral artery injuries. In biomechanical studies, C2 translaminar screws perform similarly to C2 pedicle screws and may outperform C2 pars screws in intact spine models. With disrupted atlantoaxial ligaments, constructs with C2 translaminar screws may not resist lateral bending as well as those with other screws, although they have more stability than uninstrumented, intact spines. This study reports 103 C2 translaminar screws, the largest single-surgeon series to date. C2 translaminar screws are a technically feasible, low-risk option for C2 fixation, with a 97.6% fusion rate in this series.

C2 Anatomy and Dimensions Relative to Translaminar Screw Placement in an Asian Population

A cadaveric specimen study. To determine the applicability of a modified C2 translaminar screw placement in the general adult population and to provide pertinent clinical data for screw insertion. C2 intralaminar screw fixation has recently been popularized, but this technique carries a potential drawback that the screw may breakout ventrally into the spinal canal. For this reason, a modified C2 translaminar screw fixation technique was developed to intraoperatively verify screw position and thereby decrease the risk or canal compromise. To our knowledge, there has been not an anatomic study evaluating this modification of the translaminar screw technique. The tips of the modified screws were aimed such that they exited the dorsal cortex of the center of the contralateral lateral mass, achieving bicortical fixation. A total of 120 adult C2 vertebrae were evaluated bilaterally for the following: thickness of the cranial, midportion, and caudal edge of C2 lamina; the heights of the spinous process, lamina, and lateral mass; inclination angle of the laminae, screw projection length, and trajectory angle of cranial and caudal C2 translaminar screw. A total of 83.3% specimens had bilateral laminar thicknesses ≥4.0 mm and a spinous process height ≥9.0 mm; 5% had a laminar thickness less than 4.0-mm bilaterally; 9.2% had a laminar thickness less than 4.0 mm on one side; 2.5% had a spinous process height lower than 9.0 mm. A large percentages of C2 laminae are of sufficient size to safely accommodate a bicortical 3.5-mm diameter screw. The thickness of the lamina and the height of the spinous process are the 2 limiting factors for safe translaminar screws placement. Using a bicortical technique confirms the position of the screw and thereby helps to decrease the risk of neurologic injury from screw penetration of the inner cortex of the lamina.

Modification of Wright’s technique for C2 translaminar screw fixation: technical note

To describe a modification of Wright's technique for C2 translaminar screw fixation. Bilateral crossing C2 laminar screws have recently become popular as an alternative technique for C2 fixation. This technique is particularly useful in patients with anomalous anatomy, as a salvage technique where other modes of fixation have failed or as a primary procedure. However, reported disadvantages of this technique include breach of the dorsal lamina and spinal canal, early hardware failure and difficulty in bone graft placement due to the position of the polyaxial screw heads. To address some of these issues, a modified technique was used in six patients. In this technique, the upper part of the spinous process of C2 was removed and the entry point of the screw was in the base of this removed spinous process. The screw position was satisfactory in all patients. There were no intraoperative or early postoperative complications. Our modification enables placement of a bone graft on the C2 lamina and is also less likely to cause inadvertent cortical breach. Because of these advantages, it is especially suitable for patients with advanced rheumatoid arthritis with destruction of the lateral masses of C2 or as part of a hybrid construct in patients with a unilateral high-riding vertebral artery. This technique is not suitable for bilateral translaminar screw placement.

C(2) trans-laminar screws for atlantoaxial instability: preliminary clinical report of nine cases

C(2) pedicle screw is the classic instrumentation for posterior C(2) fixation. But it could be dangerous in case of anatomical variation, such as high riding vertebral artery and small C(2) pedicle. C(2) trans-laminar screw could be an alternative choice. This retrospective study is to evaluate the feasibility of C(2) trans-laminar screw for atlantoaxial instability with anatomical variation. In our clinical work, we had nine atlantoaxial instability cases with C(2) pedicle malformation. If the malformation is unilateral, we inserted one C(2) trans-laminar screw and one C(2) pedicle screw in the normal pedicle; if the malformation is bilateral, bilateral trans-laminar screws were used. Then C(2) instrumentation could be connected with C(1) lateral mass screw or occipital screw in cases with C(1) occipitalization. Then atlantoaxial or occipitocervical fusion could be done with morselized autogenous cancellous iliac grafts. Nine cases had C(2) trans-laminar screw, including 2 atlantoaxial fusion and 7 occipitocervical fusion. Six cases had unilateral trans-laminar screw and 3 had bilateral trans-laminar screw. Radiographs demonstrated all the screws were placed satisfactorily except one. There was no neurological deterioration or vertebral artery injury. All the cases had an average follow-up of 9 months (4 - 13 months). All patients attained solid fusion without screw failure. In the 8 cases with neurological deficit, 3 were excellent, 1 was good, 2 were fair and 2 had no change. C(2) trans-laminar screw fixation could provide sufficient stability. This technique could be an alternative to standard C(2) pedicle screw in cases with pedicle malformation and high riding vertebral artery. It is safe and simple in experienced hands.

OPEN REDUCTION OF C1–C2 SUBLUXATION WITH THE USE OF C1 LATERAL MASS AND C2 TRANSLAMINAR SCREWS

Abstract Objective: Spinal cord compression secondary to a subluxation of one vertebral body over another can be achieved with reduction of the translational deformity. Intraoperative reduction of C1–C2 subluxations can be technically challenging when one uses traditional techniques (e.g., wiring and transarticular screw fixation). The popularization of C1 lateral mass and C2 pedicle screws has allowed surgeons to achieve a more complex realignment at this region of the spine. Control of both C1 and C2 with independent fixation can be used to obtain reduction. In certain instances, placement of C2 pedicle screws is not possible. The use of C2 translaminar screws (if the C2 lamina is present and suitable) is an alternative method of fixation in C2 and can be used for intraoperative reduction. Clinical Presentation: A 15-year-old boy with juvenile rheumatoid arthritis presented with spinal cord compression secondary to a C1–C2 subluxation. The C2 pedicle anatomy precluded safe placement of C2 pedicle screws. An alternative method of fixation with the use of C2 translaminar screws and reduction was performed to obtain proper alignment and decompress the spinal cord. Technique: C1 lateral mass screws and C2 translaminar screws are inserted in the usual fashion. Two contoured rods, two rod holders, and two distractors, combined with C1 lateral mass screws and C2 translaminar screws, were used to achieve reduction. Concomitant distraction between the C2 translaminar screw head and the rod holder resulted in ventral translation of C2 on C1, decompressing the spinal cord. The reduction was maintained by tightening the C2 locking nut onto the rod. Conclusion: The use of C2 translaminar screws (if the C2 lamina is present and suitable) is an alternative method of fixation in C2. C1 lateral mass and C2 translaminar screw fixation provide a powerful means of reducing C1–C2 subluxations and maintaining alignment, achieving indirect decompression of the spinal cord.

Fusions at the craniovertebral junction

The surgical management of craniovertebral junction instability in pediatric patients has unique challenges. While the indications for internal fixation in children are similar to those of adults, the data concerning techniques, complications, and outcomes of spinal instrumentation comes from experience with adult patients. Diminutive osseous and ligamentous structures and anatomical variations associated with syndromic craniovertebral abnormalities frequently complicates the approaches and limits the use of internal fixation in children. Cervical arthrodesis in the pediatric age group has the potential for limiting growth potential and causing secondary deformity. Recent advances in image analysis have enabled preoperative planning which is critical to evaluate the size of instrumentation and its relation to the patient's anatomy. Newer techniques have recently evolved and have been incorporated in the management of pediatric patients with requirement for craniocervical stabilization. Over 750 craniovertebral junction fusions have been reviewed in children. The indications for atlantoaxial arthrodesis were: (a) absent odontoid process, dystopic os odontoideum, absent posterior arch of C1; (b) Morquio's syndrome, Goldenhar's syndrome, Conradi's syndrome, and spondyloepiphyseal dysplasia. The acquired abnormalities of trauma, postinfectious instability, and Down's syndrome completed the indication in children. The indications for occipitocervical fusion were: (a) anterior and posterior bifid C1 arches with instability, absent occipital condyles; b) severe reducible basilar invagination, unstable dystopic os odontoideum, and unilateral atlas assimilation; (c) acquired phenomenon with traumatic occipitocervical dislocation, complex craniovertebral junction fractures of C1 and C2, after transoral craniovertebral junction decompression, cranial settling in Down's syndrome and inflammatory disease such as Grisel's syndrome. Instability was seen in children with clivus chordoma and osteoblastoma. Atlantoaxial fusions were performed mainly with interlaminar rib graft fusion and more recently with the transarticular screw fixation in the older patient. In the teenager, lateral mass screws at C1 and rod fixation were made; C2 pars interarticular screw fixation and C2 pedicle screw fixation. A C2 translaminar screw fixation is described. Occipitocervical fusions were made utilizing rib grafts below the age of 6. A contoured loop fixation was made in children above the age of 7, and recently, rod and screw fixation was also utilized. Abnormal cervical spine growth was not seen in children who underwent craniocervical stabilization below the age of 5. The authors have reserved rigid instrumentation for children above the age of 10 years and dependent on the anatomy.