Research Progress on the Application of Goel Technique in Craniovertebral Junction Anomalies / 中国医学科学院学报

Craniovertebral junction anomalies are a group of diseases characterized by the pathological changes of occipital bone,atlantoaxial bone,cerebellar tonsil,surrounding soft tissue,and nervous system,which are caused by a variety of factors.Chiari malformation is a common type of craniovertebral junction anomalies,the conventional surgical therapy of which is posterior fossa decompression.Currently,scholars represented by Goel have proposed a new theory on the classification,pathogenesis,and treatment of Chiari malformation based on posterior atlantoaxial fixation (Goel technique).This article introduces the progress in Goel technique,aiming to provide reference for the clinical work.

Autogenic Rib Graft for Atlantoaxial and Occipitocervical Fixation in Pediatric Patients

STUDY DESIGN: Retrospective case series. PURPOSE: To evaluate surgical outcomes and effectiveness of an autogenic rib graft for upper cervical fixation in pediatric patients. OVERVIEW OF LITERATURE: Autogenic bone grafts have long been considered the ‘gold standard’ bone source for posterior cervical fusion in pediatric patients. However, there are some unsolved problems associated with donor-site morbidity and amount of bone grafting. METHODS: We studied five consecutive pediatric patients who underwent atlantoaxial fixation or occipitocervical fixation (OCF) using an autogenic rib graft with at least 2 years of follow-up (mean age, 9.8 years; mean follow-up period, 73.0 months). Two patients underwent OCF without screw-rod constructs and three patients with screw-rod constructs. Autogenic rib grafts were used in all patients. We evaluated the surgical outcomes including radiographic parameter, bony union, and perioperative complications. RESULTS: The atlantoaxial interval (ADI) was corrected from 11.6 to 6.0 mm, and the C1–2 angle was corrected −14.8° to 7.8°. The C2–7 angle was reduced from 31° to 9° spontaneously. Two patients with OCF required revision surgery due to loss of correction. Patients did not experience any complication associated with the donor sites (rib bone grafts). Six months postoperation X-rays clearly showed regeneration of the rib at the donor sites. Bony fusion was achieved in all patients; however, bony fusion occurred more slowly in patients without screw-rod constructs compared with patients with screw-rod constructs. Bone regeneration of the rib was observed in all patients with no complications at the donor site. CONCLUSIONS: Autogenic rib grafts have advantages of potential bone regeneration, high fusion rate, and low donor-site morbidity. In addition, a screw-rod construct provides better bony fusion in pediatric patients with OCF and atlantoaxial fixation.

Morphometric Study of C1 Pedicle and Feasibility Evaluation of C1 Pedicle Screw Placement with a Novel Clinically Relevant Radiological Classification in an Indian Population

STUDY DESIGN: A retrospective computed tomography (CT)-based morphometric study of 84 C1pedicles in an Indian population focusing on critical morphometric dimensions vis-a-vis C1 pedicle screw placement. PURPOSE: To determine the feasibility of C1 pedicle screw placement in an Indian population and propose a novel classification system for the same. OVERVIEW OF LITERATURE: At present, C1 pedicle screws are rarely used, and very few studies have focused on the feasibility of pedicle screw placement in terms of racial, gender, and ethnic variations in anatomical structures. There are no CT-based data on C1 pedicles that assess the feasibility of pedicle screw placement in the Indian population. METHODS: We measured C1 pedicle diameter on CT coronal scan images of 42 adult patients. Extramedullary height (EMH) and intramedullary height (IMH) were measured. We examined the differences between the right and left atlas pedicles and compared measures between males and females. These data were analyzed using significance tests. Based on the results, we propose a novel classification system, which we believe will help in determining the feasibility of C1 pedicle screw placement. RESULTS: Forty-two adult patients (84 pedicles) were examined. Average EMH and IMH were 4.48±0.91 and 0.86±0.77, respectively. Approximately, 32% of the C1 pedicles had bone thicknesses of <4 mm, 49% had IMH of <1 mm, and 38% had no pedicles. The average thickness in women was 4.21±0.93 mm, which was significantly thinner than that in men (4.73±0.81 mm, p=0.004). Right and left pedicles were not significantly different. CONCLUSIONS: Our data indicate that approximately one-third of the Indian population may not be suitable candidates for C1 pedicle screw placement. Caution should be exercised while placing type 1B and type 2 pedicles based on our proposed classification system.

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.

Inferolateral Entry Point for C2 Pedicle Screw Fixation in High Cervical Lesions

OBJECTIVE: The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. METHODS: Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle 30degrees to 45degrees toward the midline in the transverse plane and 40degrees to 50degrees cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. RESULTS: There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). CONCLUSION: Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

Rod Migration into the Posterior Fossa after Harms Operation : Case Report and Review of Literatures

C1 lateral mass and C2 pedicle (C1LM-C2P) fixation is a relatively new technique for atlantoaxial stabilization. Complications from C1LM-C2P fixation have been rarely reported. The authors report unilateral rod migration into the posterior fossa as a rare complication after this posterior C1-C2 stabilization technique. A 23-year-old man suffered severe head trauma and cervical spine injury after vehicle accident. He was unconscious for 2 months and regained consciousness. He underwent C1LM-C2P fixation for stabilization of type II odontoid process fracture described by Harms. The patient recovered without a major complication. Twenty months after operation, brain computed tomogram performed at psychology department for disability evaluation showed rod migration into the right cerebellar hemisphere. The patient had mild occipital headache and dizziness only regarding the misplaced rod. He refused further operation for rod removal. To our knowledge, this complication is the first report regarding rod migration after Harms method. We should be kept in mind the possibility of rod migration, and C1LM-C2P fixation should be performed with meticulous technique and long-term follow-up.

Technical Strategies and Surgical Results of C1 Lateral Mass-C2 Pedicular Screw Fixation in Atlantoaxial Disorders

OBJECTIVE: There are various posterior fusion techniques in managing C1-2 instability. The aim of this study is to evaluate surgical techniques and clinical results including complications of the C1 lateral mass and C2 pedicle screw fixation (C1-2 LMPSF) in atlantoaxial disorders. METHODS: From February 1997 to July 2008, 24 patients were performed C1-2 LMPSF due to C1-2 instability. Pathway of vertebral artery was classified into three groups by 3D-angiogram. Diameter of C1 lateral mass and C2 isthmus on the plain X-ray and CT was measured before operation. Surgical method was divided into four groups according to fixation site (bilateral or unilateral) and bone graft (with or without graft). Stability of C1-2 fixation was postoperatively evaluated by flexion and extension cervical lateral films. We reviewed clinical data, imaging studies and old chart retrospectively as sources for analysis. RESULTS: Among 24 patients, os odontoideum was the most common cause (16 out of 24). Four patients had anomalous vertebral artery. Mean diameters of C1 lateral mass was 9.9(range 4.2~16.4) mm at right side, 10.3 (range 3.4~14.2) mm at left side. Mean diameter of C2 isthmus was 5.8 (range 1.0~10.1) mm at right side and 5.8(range 2.1~8.2) mm at left side. Two patients showed very narrow C2 isthmus. As a result, unilateral C1-2 LMPSF was performed on 6 patients (4 for anomalous vertebral arteries and 2 for narrow C2 isthmus). 12 of 18 patients were with C1-2 interlaminar bone graft and 6 patients without bone graft. All patients showed stable C1-2 fixation by flexion and extension cervical lateral X-ray films taken at least 6 months after surgery. Five out of 8 patients who had preoperative radiculopathy only showed improved symptoms. However, Seven out of 8 patients who had myelopathy showed little neurological improvement . CONCLUSION: For C1-2 LMPSF, preoperative 3D CT-angiogram study is mandatory to identify abnormal vertebral artery and narrow C2 isthmus. Bilateral C1-2 LMPSF without bone graft is enough to obtain stable C1-2 fixation. If there is an abnormal vertebral artery or narrow C2 isthmus, unilateral C1-2 LMPSF with bone graft and wiring is alternative successful method.

Posterior Atlantoaxial Fixation with a Combination of Pedicle Screws and a Laminar Screw in the Axis for a Unilateral High-riding Vertebral Artery

A vertebral artery (VA) injury presents a difficult problem in atlantoaxial fixation. Recent technical reports described posterior C2 fixation using bilateral, crossing C2 laminar screws. The translaminar screw technique has the advantages of producing little risk of VA injury and the unconstrained screw placement. In addition, biomechanical studies have demonstrated the potential of the translaminar screw technique to provide a firmer construct that is equivalent to methods currently used. We report the successful treatment of C1-2 instability with a left-side high-riding VA. Because of the potential risk of VA injury, we performed a posterior C1-2 fixation with a combination of pedicle screws and a laminar screw in C2. We first placed bilateral C1 lateral mass screws and a right-side C2 pedicle screw. However, placement of the left- side C2 pedicle screw was technically difficult due to a narrow isthmus and pedicle. A laminar screw was inserted instead and authors believe that this posterior C1-C2 fixation with a combination of pedicle screws and a laminar screw in C2 can be a useful alternative technique for the treatment of C1-C2 instability in the presence of a unilateral high-riding VA.

C1-2 Instability associated with Duplicated Vertebral Artery: A Case Report / 대한척추외과학회지

A vertebral artery injury is one of the most critical complications of atlantoaxial fixation. Abnormal courses or congenital anomalies of the vertebral artery increase its risk. The authors report a case of a patient who had an atlantoaxial subluxation associated with severe spinal cord compression and a duplicated vertebral artery. The atlantoaxial subluxation, which was not reduced satisfactorily by an intraoperative head position change or direct manipulation of the atlas and axis, precluded a transarticular screw fixation. The lack of free space around the spinal cord precluded a sublaminar wiring. The duplicated vertebral artery made it difficult to insert C1 lateral mass screws and C2 pedicle screws with Harms' technique.

Posterior Atlantoaxial Fixation with Lateral Mass Screw in the Atlas and Pedicle Screw in the Axis

OBJECTIVE: The authors report the successful use of a recently described technique of posterior fixation of the C1 lateral mass and the C2 pedicle with polyaxial screws and rods. METHODS: After posterior exposure of the C1-C2 complex, the polyaxial screws were inserted into the lateral mass of C1 and the pedicle of C2 with the guidance of anatomic landmarks and fluoroscopy. Then, the pedicle screws of each side were linked with a rod. Because the C1-C2 pedicle screw fixation was sufficiently rigid, an additional posterior wiring or structural bone graft is unnecessary. RESULTS: The early clinical and radiologic follow-up data indicated solid fusion of C1 and C2 vertebrae with no observed neural or vascular damage related to this technique. CONCLUSION: The posterior fixation of the C1-C2 complex using polyaxial screws and rods seems to be a reliable technique and an efficient alternative to the more commonly accepted procedures.