Chronic Atlantoaxial Instability Research Articles

Independent Correlation of the C1-2 Cobb Angle With Patient-Reported Outcomes After Correcting Chronic Atlantoaxial Instability.

ObjectiveTo investigate three-planar radiographic results and patient-reported outcomes (PROs) after correcting chronic atlantoaxial instability (AAI) by translaminar screw (TLS) and pedicle screw (PS) fixation, and to explore the potential association of atlantoaxial realignment with PRO improvements. MethodsTwenty-three patients who underwent C1 lateral mass screw (LMS)-C2 TLS and 29 who underwent C1 LMS-C2 PS with ≥ 2 years of follow-up were retrospectively analyzed. Three-planar (sagittal, coronal, and axial) radiographic parameters were measured. PROs including the Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) score and the Short Form 36 Physical Component Summary (SF-36 PCS) were documented. Factors potentially associated with PROs were identified. ResultsThe radiographic parameters significantly changed postoperatively except the C1–2 midlines’ intersection angle in the TLS group (p = 0.073) and posterior atlanto-dens interval in both groups (p = 0.283, p = 0.271, respectively). The difference in bilateral odontoid lateral mass interspaces at last follow-up was better corrected in the TLS group than in the PS group (p = 0.010). Postoperative PROs had significantly improved in both groups (all p < 0.05). Thereinto, NDI at last follow-up was significantly lower in the TLS group compared with PS group (p = 0.013). In addition, blood loss and operative time were obviously lesser in TLS group compared with PS group (p = 0.010, p = 0.004, respectively). Multivariable regression analysis revealed that a change in C1–2 Cobb angle was independently correlated to PROs improvement (NDI: β = -0.435, p = 0.003; JOA score: β = 0.111, p = 0.033; SF-36 PCS: β = 1.013, p = 0.024, respectively), also age ≤ 40 years was independently associated with NDI (β = 5.40, p = 0.002). ConclusionThree-planar AAI should be reconstructed by C1 LMS-C2 PS fixation, while sagittal or coronal AAI could be corrected by C1 LMS-C2 TLS fixation. PROs may improve after atlantoaxial reconstruction in patients with chronic AAI. The C1–2 Cobb angle is an independent predictor of PROs after correcting chronic AAI, as is age ≤ 40 years for postoperative NDI.

Retro-Odontoid Pseudotumor with Cervical Medullary Compression: A Case Report

A retro odontoid pseudo tumor is a mass lesion lying posterior to the odontoid process along the dura. It is a disease process seen in inflammatory and non-inflammatory conditions causing chronic atlanto-axial instability. This type of mass has the potential to enlarge causing cervicomedullary compression and symptoms of myelopathy. In the past, authors have relied on a more invasive, direct approach to decompress the mass including an anterior trans oral odontoidectomy and a posterior trans-dural resection. The objective of this case report is to describe the use of an indirect approach, cervical fusion with decompressive laminectomy, to successfully treat a retro odontoid pseudo tumor in a geriatric patient. A male patient in his late 90’s presented with inability to ambulate, global paresis, and long tract signs in the upper extremities. He was found to have a large odontoid mass with compression at the cranio-cervical junction. He underwent cervical fusion with instrumented fixation from C1-6 and decompressive laminectomy from C4-6. Over a follow-up period of two years, there was improvement in the patient’s motor weakness and ambulation. Radiographic evaluation at the two-year mark showed marked reduction in pannus size. Indirect approaches to decompression in patients with retro odontoid pseudo tumor using techniques such as cervical fusion may be a safe for effective treatment in patients of advanced age, with multiple co-morbidities, and inability to tolerate lengthy surgical procedures.

Radiographic Risk Factors and Surgical Outcomes for Retroodontoid Pseudotumors

Retrospective review. The aim of this study is to assess the radiographic characteristics of patients with a retroodontoid pseudotumor and to evaluate the efficacy of posterior fusion. Retroodontoid pseudotumors are usually caused by chronic atlantoaxial instability in patients with rheumatoid arthritis (RA). However, the pathomechanism and optimum treatment are unknown. We reviewed the charts and radiographs of 11 patients (5 RA and 6 non-RA) with a retroodontoid pseudotumor who underwent posterior fusion. Preoperative radiographs were evaluated for atlantodental interval; Redlund-Johnell criterion; O-C1, C1-2, C2-3, and C2-7 angles. The Japanese Orthopaedic Association (JOA) score was used to evaluate clinical outcomes. All RA patients and 1 non-RA patient displayed atlantoaxial subluxation. Three patients underwent occipitocervical fusion and 8 patients atlantoaxial fusion. The JOA score improved significantly from 10.0 to 12.8 at follow-up (P<0.01). The retroodontoid pseudotumor regressed in 10 patients. Maximal thickness of the pseudotumor decreased from 8.9 mm preoperatively to 5.3 mm (P<0.01) at follow-up. In non-RA patients, the mean differences (Δ) between flexion and extension were 7.8, 13.4, 3.5, and 18.5 degrees for ΔO-C1, ΔC1-2, ΔC2-3, and ΔC2-7, respectively. In RA patients, a retroodontoid pseudotumor may develop because of atlantoaxial subluxation. In non-RA patients, excessive atlantoaxial angular motion because of the limited range of motion of O-C1 and/or subaxial vertebra may cause a pseudotumor. Atlantoaxial fusion to suppress atlantoaxial instability is one of the optimum treatments.

Radiographic Analysis of the Cervical Spine in Patients With Retro-Odontoid Pseudotumors

A retrospective review of 10 consecutive patients with a noninflammatory retro-odontoid pseudotumor. To examine the radiographic characteristics in patients with a retro-odontoid pseudotumor and to evaluate the efficacy of posterior fusion. A retro-odontoid pseudotumor, a reactive fibrocartilaginous mass, is known to develop after chronic atlantoaxial instability; however, one-third of the reported cases showed no overt atlantoaxial instability. The pathomechanism for such "atypical" cases remains unclear, although altered cervical motion secondary to ossification of the anterior longitudinal ligament (OALL) or severe spondylosis has been implicated. We reviewed the charts and radiographs of 10 patients with a retro-odontoid pseudotumor who underwent surgery. Preoperative radiographs were evaluated for atlas-dens interval (ADI), presence of OALL, range of motion, and segmental motion adjacent to the atlantoaxial joint. Computed tomography was evaluated for degenerative changes of zygapophysial joints. There were 6 men and 4 women. Atlantoaxial instability (ADI >4 mm) was observed in 2 patients. ADI was less than 3 mm in 5 patients. Frequent association of OALL (6 patients) and marked decrease in C2 to C7 range of motion (mean, 17.6 degrees ; range, 3 degrees-36 degrees ) were noted. Ankylosis of O-C1 was observed in 4 patients and C2 to C3 in 6. Severe degenerative change of C2 to C3 zygapophysial joint was observed in 4 patients. The patients underwent occipito-cervical fusion (9 patients) or direct removal of the pseudotumor (1 patient). Postoperative magnetic resonance imaging invariably demonstrated the mass regression. Retro-odontoid pseudotumors were not always associated with radiographic atlantoaxial instability. Our data indicate that extensive OALL and ankylosis of the adjacent segments are risk factors for the formation of the pseudotumor. Retro-odontoid pseudotumors may develop as an "adjacent segment disease" after altered biomechanics of the cervical spine, especially those in the adjacent segments. Posterior fusion was effective even in cases without radiographic atlantoaxial instability.

Bilateral atlas laminar hook combined with transarticular screw fixation for an unstable bursting atlantal fracture

The unstable atlas burst fracture ("Jefferson fracture") is a fracture of the anterior and posterior atlantal arch with rupture of the transverse atlantal ligament and an incongruence of the atlanto-occipital and the atlanto-axial joint facets. The posterior atlantoaxial fusion is frequently used to reconstruct the stability of atlantoaxial joint. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and chronic atlantoaxial instability. As a modified three-point fixation the bilateral C1-2 transarticular screws combined with C1 laminar hook and bone grafts can provide best biomechanical stability, but no standard protocol has been reported for the use of this fusion technique. A retrospective review of clinical series should be conducted to evaluate the clinical outcome of bilateral atlas laminar hook combined with transarticular screw fixation for unstable bursting atlantal fracture. From March 2002 to March 2006, there were total 12 cases of unstable atlantal bursting fractures, 10 males and 2 females, age ranging 18-54, with mean of 36 years old. All patients were operated on posterior atlantoaxial fusion using bilateral atlas laminar hook combined with transarticular screw fixation after atlantoaxial joint were reduced and followed up for 12-24 months. The medical records and radiographs of the 12 patients were reviewed. Each patient underwent a complete cervical radiograph series including lateral flexion-extension view and a computed topographic scan. The Frankel grades and ASIA scores were applied to assess the neurologic status. In all patients, a good bony fusion of the atlanto-axial segment was achieved. All patients showed significant improvement of the neurologic defect and no instability on their follow-up plain radiographs and computerized tomography in follow-up interval. For the patients who suffer from the unstable bursting atlantal fracture, the nonoperative methods could carry some clinical complications including infection, nerve injury, etc. and is frequently failure, Posterior atlantoaxial fusion using bilateral atlas laminar hook combined with transarticular screw fixation is an effective treatment.

Pannus resolution after occipitocervical fusion in a non-rheumatoid atlanto-axial instability

Periodontoid pseudotumor or pannus is considered to be an inflammatory mass most frequently associated with rheumatoid arthritis. Transoral resection of the pannus has been the treatment of choice for patients with associated myelopathy, followed in many instances by posterior stabilization. However, some authors have reported resolution of pannus associated with rheumatoid arthritis and other forms of chronic atlanto-axial instability only after posterior stabilization. We report a case of a 69-year-old man who presented with a rapidly progressing myelopathy due to a retro-odontoid mass produced by chronic atlanto-axial instability associated with an occipital assimilation of C1 and tight posterior fossa. An urgent posterior fossa craniectomy followed by occipitocervical fixation was performed. After surgery, the patient's clinical condition improved and 1 year after surgery was asymptomatic, walked without any help and had normal strength. Control MR showed complete resolution of the retro-odontoid pannus.

Atlantoaxial instability in Down's syndrome: a five year follow up study.

In 1986 all 90 children aged 4-19 years with Down's syndrome attending school in the area served by the Southern Derbyshire Health Authority underwent radiography to identify atlantoaxial instability (AAI). This study details repeat observations five years later. Full results were available on 67 (74%), information on health status was available on the remaining 19 (21%); four (4%) were untraced. There was an overall significant reduction in the atlanto-axial gap over five years. No one developed AAI on repeat testing who had not had it earlier. One child who had previously had normal neck radiography developed acute symptomatic AAI after ear, nose, and throat surgery. Radiographs were done on three occasions on the same day in 49 individuals, ensuring full flexion of the upper neck. There were no significant differences between the radiographs, even in five subjects with AAI. Management of AAI in Down's syndrome is discussed in the light of these findings. Radiography can reliably detect children with chronic AAI who may be at risk of gradually developing symptoms; this may justify a screening programme. This must be distinguished from those who develop symptoms after acute trauma or anaesthesia, for which specific precautions are needed, and previous screening radiographs are unhelpful.

Posterior Transarticular Screw Fixation of C1-C2

Posterior Transarticular Screw Fixation of C1-C2

Chronic atlanto-axial instability in Down syndrome.

We studied the radiographs of thirty-two patients with Down syndrome for evidence of atlanto-axial instability. One of the patients had instability in 1970 and seven had it in 1983. The interval between the atlas and the odontoid process in the patients who demonstrated motion at that interval radiographically averaged 2.78 millimeters in 1970 and 6.93 millimeters in 1983 (p less than 0.005). Four patients whose radiographs showed atlanto-axial motion in 1970 lost that motion by 1983, and in seven patients who did not show atlanto-axial instability in 1970 it developed by 1983. Atlanto-axial instability was more likely to develop in boys who were more than ten years old. Accessory upper-cervical ossicles became evident in three patients, none of whom had atlanto-axial motion. However, one of these three patients had an abnormally wide atlanto-axial interval.