Anterior Cervical Discectomy, Fusion and Stabilization by Plate and Screw–early Experience

Anterior cervical plating is commonly performed to stabilize anterior cervical fusion. The aim of the study was to evaluate the clinical and functional outcome, radiological fusion and operative complications in cases of cervical spondylotic myelopathy and radiculopathy who underwent Anterior Cervical Discectomy and Fusion (ACDF) by autograft and stabilized with plate and screw. We evaluated 16 consecutive patients (M: F=10:6) from January 2008 to December 2010 in Bangabandhu Sheikh Mujib Medical University (BSMMU) and different private hospitals in Dhaka, in cases where adequate conservative treatment failed. Single level ACDF by autograft and stabilization by plate and screw was done in 10 patients and 06 patients had two levels fusion. The mean follow up period was 18 months. The patients improved significantly (p<0.05) and the recovery rate was 87.50%. All patients showed radiological fusion (p<0.001). There was no hardware failure, graft extrusion or plate breakage. ACDF with plate and screw is fairly safe and effective therapy for cervical disc degeneration leading to myelo-radiculopathy where major post operative complications are uncommon.


Introduction
Cervical spondylotic myelo-radiculopathy (CSMR) is a spinal cord dysfunction (SCD) accompanying typical age related degeneration of the cervical spine 1 .Myelopathic or upper motor neuron lesion (UMNL) findings (e.g.hyperreflexia and gait disturbance) are the typical manifestations and the most common cause of SCD after 55 years 2 .Other manifestation is radiculopathy due to degenerative process that leads to loss of disc height; annulus bulge/tear and herniation of disc material to produce pressure effect over the cord and roots 3 .Instability by altered biomechanics of the cervical spinal column invites inflammatory reparative process which produces arthritic pain and facet hypertrophy leading to spur formation 2 .
Neck or shoulder pain with radiation to one or both upper limbs, tingling, numbness or weakness in the hand is common presenting symptoms of cervical radiculopathy.Features of myelopathy include, altered gait, muscle weakness, bladder/ bowel dysfunction, reduced fine motor skills, which all depends upon the location of compression.Myelopathic hand, Grip release sign (Patient is unable to make and release a fist more than 20 times in 10 seconds), Hoffman's sign, Romberg test along with gait disturbances (broad based and hesitant) are common in severe conditions.Changes in the pattern of bladder and bowel dysfunction are the key components of the history found in 20% -50% of the patients 4 .
Anterior cervical discectomy and fusion (ACDF) has first been introduced by Bailey and Badgley 5 , Smith and Robinson 6 and Cloward 7 in the 1950s and early 1960s for degenerative diseases of the cervical spine.To overcome the graft related complications (e.g., graft compression fracture, graft resorptions or dislocation and pseudoarthrosis) anterior plating to the treated segment is highly recommended 8 .Anterior plate and screw constructs provides enhanced stability and maintenance of deformity correction, lordotic curvature and increases the stability and probability of fusion, compared to no plates and it may eliminate the need for rigid collar immobilization postoperatively 9 .Though use of plate for single level ACDF is controversial but it is the most common operative technique for CSMR due to degenerative cervical disease 10 .
There had been few studies in our country where outcome of non-instrumented and instrumented ACDF in varieties of cervical disorders has been analyzed but there had been no study assessing the outcome of this technique in CSMR.The aim of this study was to analyze the clinical and functional outcome, fusion and overall complications of surgery in this common cervical disorder.

Materials and Methods
This study is a consecutive case review of 16 patients who underwent instrumentation at single and two level anterior cervical discectomy and fusion with autogenous tricortical iliac crest graft and plating in locking mode from January 2008 to December 2010 in Bangabandhu Sheikh Mujib Medical University and different other private clinics in Dhaka.Ten patients had single and 6 patients had two level fusion.All patients had clinical evidence of cervical radiculopathy or myelopathy or both, unresponsive to conservative treatment with MRI confirmation of nerve root impingement and cord compression in degenerative disease of the cervical spine.Listhesis, tumor and tuberculosis were excluded from history, clinical examinations and investigations.
Plain X-ray (taken in the upright position) in AP view showed joint space narrowing or sclerosis, lateral view showed disc space narrowing, end plate osteophytes, loss of lordosis or spondylolisthesis.Ossified Posterior Longitudinal ligament (OPLL), a solid line of bone immediately behind the vertebral bodies was also seen in lateral view.Flexion-extension views of the lateral x-ray showed increase motion at spondylosis or listhesis.MRI was done in all patients in severe unremitting neck pain with failed conservative treatment and or progressive neurological deficits.Radiographic determination of union and osseous incorporation based on, 1) continuity of the trabecular and/or complete osseous union at the graft/ bone interface 2) absence of luscencies or halo formation around the graft with the presence of bridging bone.We assessed pain status improvement by Visual Analogue Score (VAS) 11 , the clinical outcome (sensory, motor and reflex) by the clinical tests and overall functional outcome with modified Odom's criteria 8 (Table-I).We focused on operating room time, hospital stay, intra and postoperative complications, outcome and time to return to normal activities including work.No patient had previous cervical spine surgery.Patients were discharged with soft cervical collar for 1 month (average) and began range of motion exercise as shortly as pain subsided.Depending on the level of job activity patient were instructed to resume normal activities which was 6 weeks for moderate labor and 12 weeks for job required heavy labor and 3 weeks if the job required minimal labor.Postoperative evaluation included examinations and lateral cervical spine radiograph at 3, 6, 12 weeks, and 6 months and then annually to assess solid fusion and progressed bony incorporation at the graft vertebral interface.
The technique used was a modification of the procedure as originally described by Smith and Robinson 6 .Briefly, a transverse right sided cervical incision was used for exposure.All the disc material and posterior osteophytes were removed.Posterior longitudinal ligament was removed at the intervertebral space.Autogenous tricortical bone graft taken from the iliac crest, sized positioned and fixed with locking cervical plate.

Results
Sixteen consecutive patients of cervical spondylosis were treated.Mean age of the patients was 45 years (range 35-55yrs).There were 10(62.50%)male and 06(37.50%)female (Table-II).Mean duration of symptoms was 1.5 years and follow up was 18 months (range 12-30 months).Average operating room time was 2.5 hours and average hospital stay was 3 days and average time to return to normal activities was 3 weeks.Neck and arm pain improved significantly (p<0.001)post operatively as well as the sensory, motor and reflex status (p<0.05).
As described in Table-V, complications were donor site morbidity in 03(18.75%)patients, which improved at 4 months; causes were fracture of the ilium, infection, haematoma.Dysphagia was found in 02(12.50%)patients which was mild and self limited.There was no dysphonia, pseudoarthrosis or deformity due to graft subsidence, graft dislodgement, plate loosening or breakage, screw migration or misdisplacment, and CSF leakage.There was no deterioration of neurological symptoms and adjacent segment disease.

Discussion
The natural history of CSMR has not been thoroughly defined and documented.Almost all patients worsen if left untreated and most studies report significant numbers (over 50%) of patients progressing to severe disability 12 .Indications for instrumentation in these patients are less clear 13 , but the excellent outcome of rigid internal fixation and theoretical advantages of decreasing graft migration have made plating an attractive option 14 .We underwent the same technique and the demographic variables of this series were comparable to Ali 15 , where male patients were predominant and C 5/6 level was the commonest involved site.The significant (p<0.05)clinical improvement (Neck pain, arm pain, motor, sensory and reflex) improvement was comparable to Wang 16 .
According to Epstein 17 Anterior Cervical Plating (ACP) can maintain lordosis and addition of a ventral cervical plate may add to the security of fixation 18 .Several reports have suggested that rigid internal fixation may be superior to conventional ACDF in patients with CSMR 19 .Dynamic plate designs provided a faster fusion compared with rigid plate design with lower rate of implant related complications 20 .Hardware failure ranged from 2-44% in unrestricted back out system whereas only 0-18% in locking system with unicortical screws that provided greater screw pullout protection 21 .Although we did not have any hardware failure, an overall screw loosening rate of 24% has been reported in the literatures 22 .
Connolly 23 reported fusion rates with autografts ranging from 87-97%, and Emery The literature shows 03% complication of postoperative dysphonia due to recurrent laryngeal nerve palsy, more on the right side 26 but we did not face such problem in any patient.Wound hematoma with airway compromise was found 02%-07.30% in some literatures 30 but it was also not found in our small series.Incidence of adjacent segment disease was found 02.90%, predicted at 10 years follow up in the literature 20 but in our short term follow up these complications could not be assessed.
The limitation of the study is that the sample size was small and follow up period was also short to comment largely.
It can be concluded that one or two level ACDF with anterior plating for cervical spondylotic radiculopathy and myelopathy is a safe, effective procedure which provides shorter convalescence and rapid return to activity.

Table I :
Assessment criteria for overall functional outcome Modified Odom's criteria Excellent No complaints related to cervical lesion, with a smooth return to daily activities and work

Table III :
Clinical follow up and operative outcome (n=16)

Table IV :
Level of fusion (n=16)

Table V :
Complications (n=16) 23reported 20-27% consistent rate of pseudoarthrosis for anterior discectomy and autogenous bone fusion.The risk of pseudoarthrosis increases with each additional level of surgery23. Alhough we had 100% fusion and no pseudoarthrosis, the results might have varied with longer follow up and larger study population.
29 most reviews, bone graft donor site pain in autogenous bone grafting was reported25mostly due to infection, hematoma, iliac crest fracture and meralgia parasthetica 26 but we faced it only in 03(18.75%)patients.Deformity owing to graft subsidence, graft dislodgement, or plate loosening 27 can occur and it is more problematic with multilevel corpectomy (3 or more levels), but it was absent in our series.Casper and Piltzen 28 reported that graft migration was decreased in multilevel fusions and eliminated in single level fusions.Graft collapse was reported in 20-30% of multilevel fusion operation29.