Posterior occipito cervical decompression with fixation and fusion in Cranio vertebral junction compression

Objective: To find out the clinical outcome of posterior decompression with occipitocervical fixation and fusion in patients with Craniovertebral junction instability. Methods: Eighty consecutive patients of cranio vertebral junction (CVJ) compression were treated in the department of neurosurgery, Jinnah Postgraduate Medical Centre (JPMC), Karachi over a period of 05 years from 1st January 2012 till 31st August 2016. All patients underwent posterior decompression with occipitocervical fusion (OCF) and fixation. The clinical outcome was assessed by Japanese Orthopedic Association (JOA) score and grading. Results: Out of 80 patients with CVJ instability, 64 (80%) were due to non traumatic causes, while 16 (20%) were secondary to trauma. All 80 patients(100%) showed post operative relief in pain. Sixty four (80%) patients showed improvement in power post operatively while six (7.5%) had no change, four (5%) showed deterioration and six (7.5%) patients expired. Sixty four (80%) patients had improvement of the JOA scores at last follow-up. According to etiology, the JOA score for patients with trauma improved in 12(75%) patients and 52(81.25%) for non traumatic causes while six patients (7.5%) expired. Fusion was achieved in 64 (80%) patients at last follow-up. Conclusion: Posterior decompression with occipitocervical fusion and fixation is safe and can be recommended in cases of CVJ compression.


INTRODUCTION
The craniovertebral junction surrounds key neurological structures in a complex arrangement, making instability associated with it, a diagnostic and therapeutic challenge. 1,2 Majority of these cases are associated with non traumatic etiologies like Down's syndrome, osteogenesis imperfecta, and connective tissue disorders such as Ehlers-Danlos, therefore, special attention should be paid to any member of this cohort exhibiting one or more symptoms. 3 These injuries may cause immediate fatality or delayed deterioration of neurological function; therefore they require a sound stabilization to be performed as soon as possible. 4 The exact operative procedure is directed by nature of lesion and degree of compression. The OCF procedure is a technically demanding and severely invalidating surgical procedure, compromising axial rotation of the head above the trunk but also limits flexion-extension. This multi-joint complex allows for >50% of all head and neck movements. 5 Indication to OCF can only be an instability causing neurologic impairment or a potential neurologic damage. In addition, the sharp angle at which the occiput meets the upper cervical spine creates a significant lever arm that works against surgical fixation devices. Therefore, the most rigid fixation device possible is required to promote fusion. 6 There has been a lookout for one such surgical procedure which is inherently safe, easily reproducible and biomechanically sound. Thus, this study was done to see the clinical improvements after posterior decompression with occipitocervical fixation and fusion in patients with Craniovertebral junction instability. Hence, this method can be used in patients with this challenging disease entity to reduce its associated morbidity and mortality.

METHODS
The study was conducted in the department of neurosurgery at Jinnah Postgraduate Medical Centre, Karachi from 1 st January 2012 till 31 st August 2016, after obtaining Institutional Review Board (IRB) approval. Eighty consecutively admitted patients with CVJ compression, 51(63.75%) males and 29 (36.25%) females) were included in the study, secondary to traumatic and non traumatic etiologies as well as neurologically intact patients but with pain or instability on radiology. Patients with malignancy, previous surgery or where only decompression was required were excluded. The specific treatment modality was chosen considering the general medical condition of the patient, severity and location of the fracture, compression of the spinal cord, degree of instability and the neurological status. Pre operative assessment was done via plain x-rays, MRI and 3D CT scans.
All patients were initially given traction and observed clinically and radiologically. In all patients OCF was done either with DCP plates and sublaminar wires of C2 and C3 with occipital bone or occipital plates with C2 pedicle and C3 lateral mass screws where financially feasible. The posterior arch of C1 was resected in all cases. Bone graft was placed between occipital bone and C2 lamina.
X-ray cervical spine and 3D CT scans were done post operatively and on follow-up. The clinical outcome was assessed by JOA score and grading [ Table-I]. A hard cervical collar was worn for three months post operatively. The total JOA score and grading assesses motor and sensory functions of four extremities and sphincter, amounting to a total of seventeen points. The lower the score, the more severe the deficits. The JOA score was assessed before the operation, at discharge, one month and finally at six months follow up.
Data was collected with help of performa including history, examination, relevant pre and postoperative radiology (X ray, 3D CT and MRI) and post op clinical findings. Statistical analysis was
All 80 (100%) patients showed post operative relief in pain. Out of 80 patients, 64(80%) had improvement of the JOA scores at last follow-up. According to etiology, the JOA score for patients with trauma improved in 12(75%) patients as shown in [  Table-IV]. Six (7.5%) patients expired, four due to respiratory compromise and two due to pneumonia and sepsis.

DISCUSSION
Instability of the CVJ imposes diagnostic and therapeutic problems due to its complex anatomy and biomechanical characteristics. These   injuries may cause immediate fatality or delayed deterioration of neurological function. 7 Lesions of CVJ with cervicomedullary compression are associated with high morbidity and mortality rates. Thus, the aims of occipitocervical fusion surgery are to restore normal alignment, to ensure adequate decompression and to achieve structural stability. Presentation varies from progressive myelopathy, radiculopathy, lower cranial nerve dysfunction, or deformities of the craniocervical region. Operative stabilization of the craniocervical junction is the most common treatment described in the literature 8,9 and in similar manner, we have done fixation and stabilization in all our patients. In patients with such instability, the indication for fusion is an extensive posterior instrumentation fixation procedure that sacrifices the motion of the occipital and C 1, 2 complex and is still controversial. Several clinical measures of disease severity have been developed such as the Japanese Orthopaedic Association (JOA), Nurick, and Chile's modified Japanese Orthopaedic Association (mJOA) scoring systems. 10 These scales enable the clinician to quantify and assess the extent and progression of the disease. We used JOA grading system in our series. The goals of fixation were to achieve anatomic alignment, protect neural elements, stabilize the spine while preserving the normal motion of elements and to produce a "functional decompression". Significant (70.2% of patients) improvement of the JOA scores was noticed after surgery in our patients and the results are consistent with the 75% to 95% improvement rate reported in literature. [10][11][12] Based on existing literature, techniques using screw/rod constructs in occipitocervical fusion are associated with very favorable outcomes, 13 similar to our study where we have rods and screws construct.
Diverse OCF techniques such as screw-rod and occipito-cervical hook are currently available, and all are shown to have high fusion rates (89-100%). 14 Screw-rod fixation allows for strong biomechanical fixation, immediate stability after surgical fixation with no additional external fixation. Statistically significant neurologic improvement (recovery rate >50%) was demonstrated by 12(75%) of patients in trauma and 52(81.25%) in non traumatic cases, comparable to Galbraith et al. 15 who report a 30% to 40% significant improvement in myelopathy.
Many researchers have discussed postoperative fusion rates in CVJ patients undergoing occipitocervical or atlantoaxial arthrodesis. Fusion rate of the CVJ lesion is remarkably successful as reported from 75% to 100% and our results at 80% lie within this range. 16 Nearly all studies have demonstrated consistently high fusion rates with cervicovertebral junction fixation regardless of fusion methods and underlying pathology. 17 Modern case reports, however, have documented improved neurological outcomes, likely as a result of earlier diagnosis and surgical stabilization. 18 Extreme difficulties are encountered in paediatric age group because of less developed anatomy, fragile bones and more surgery related complications in children as compared to adult group. However, good outcome was observed in our series of patients as only one out of ten patients deteriorated neurologically in comparison to three adult patients in our study. Probably, advancements in emergency care and diagnostic methods have increased the number of children who survive atlanto-occipital dislocation. 19 It is further recommended that if there is neurological decline after fixation, obstructive hydrocephalus should be suspected. Four patients (one child and three adults) showed neurological deterioration. These were due to difficulties in intubation, failure to achieve adequate decompression and infection. Mortality in our series was 7.5% in which four were due to respiratory compromise and two due to pneumonia and sepsis. This was comparable with other studies like Song et al. 7  Recent biomechanical studies have shown that the screw-based construct is more rigid than the wirerod construct and reduced the need for external orthoses, but it is rather unclear whether it will result in a higher rate of fusion. Reports of fusion rate of 80% after wiring and of 94% after screwing do not appear to influence markedly in final clinical results. 20

CONCLUSION
Posterior decompression and occipitocervical fusion is safe with a high percentage of favorable outcomes and to be recommended in cases of CVJ compression. We recommend that the technique of CVJ fixation should be individualized based on the location and extent of the injury. However, for a successful outcome, careful patient selection and accurate imaging diagnosis are essential.

Grant Support & Financial Disclosures:
None.