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Orthopaedic Clinic

Anterior cervical Discectomy and Fusion (ACDF)
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Indications:
 
Cervical spondylosis affecting a single or two levels of cervical vertebraes C 3 -T1.
Cervical disk herniations.
 
Contraindications:
 
Adjacent segment stiffness secondary to pathology like Ankylosing spondylitis.
 
Special Instrument Required: Caspar distractor which has pins that can be screwed into the vertebral bodies.
 
 
Graft Bed prepration:
 
The level of fusion is confirmed by taking intraoperative radiographs after the placement of bent needle in the desired disc space. Once the level is confirmed the anterior longitudnal ligament is incised in an H shaped fashion. The annulus fibrosus of the intended disc space is cut with a no 15 scalpel blade. The disc material is removed using a pituitary rongeuer. The endplate of superior and inferior vertebrae are curreted out. A small lamina spreader is used to spread apart the intervertebral space. The disc material is curreted out to expose the posterior longitudinal ligament (PLL). If there appears to be a rent in the PLL, it may suggest that a part of disc may have herniated or sequestered into the cannal. A patient attempt at removal of all the herniated disc material is rewarding in terms of clinical outrcomes of relief of symptoms. Anterior osteophytes are removed using a rongeur. The anterior surface of the vertebral body is levelled out or squarred off for optimal placement of the implant. The end plated can be perforated to permit nutrition of the graft and better fusion rates. Alternatively a burr may be used to prepare the end plates. The various types of graft are described below, the graft is placed using a forcep and the compression removed to ensure a tight fit.
 
Bone graft:
 
Autologus bone graft is considered as the gold standard. Four techniques are most commonly employed for arthrodesis: Smith-Robinson, Bailey- Badgley, Simmons and Bhalla and  Cloward methods. Smith - Robinson graft is a horse shoe shaped graft that is placed with cortex facing anteriorly. In Bailey- Badgley technique a graft trough 1/2 inch wide and 3/16th inch wide is prepared and a unicortical corticocancellous graft is  inserted in the space. The Simmons and Bhalla technique uses  a graft that is prepared by a creating a bevel from anterior to posterior both above and below to give the bicortical graft a shape of Key stone. Cloward and Dowel technique uses a bicortical plug grfat that is tamped into the space created in between the vertebral body using a set of guarded drill bits.
 
Allograft: Its use remain contoversial in view of high non union rates of upto 50% reported with its use. Its use is associated with advanatges of avoiding the harvest of auto graft which is not without signifiacnt morbidity.
 
Bone Graft substitutes and Graft extenders: Newer substitutes like BMP are currently being evaluated for the use in anterior cervical procedures, their current status in the feild today remains at best experimental.
 
Wound Closure and Postoperative treatment: The H shaped incision over the anterior longitudnal ligament is attempted to be approximated. A deep suction is placed to prevent postoperative hematoma which can be life threatening. The subcut and skin are closed in routine fashion. The patient may be allowed to ambulate in cervical orthosis over next 2-3 days. The cervical orthosis may be continued for 6- 8 weeks.
 
Pitfalls and Complications:
 
Potential Complications associated with approach are described in the approach section.
 
Operation of a drill without the protection of the drill guard, may lead to drill entering the spinal canal,
 
Displacement of a dowel bone graft into the spinal canal, either during surgery or postoperatively, may cause cord injury.
 
Transient postoperative transverse myelitis may occur secondary to the use of electrocoagulation on the posterior longitudinal ligament.
 
There always remains of risk of graft failure, implant failure and non union with any arthrodesis procedure.
 

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