Cervical disc arthroplasty

View Details

Parent item

Anterior cervical procedure

Indications

• FDA:
• Patients must be skeletally mature.
• The device is approved for use at single or two contiguous levels between C3 and C7.
• Indications include symptomatic cervical radiculopathy or myelopathy caused by disc herniation or spondylosis that is unresponsive to conservative treatment.
• Patients typically must have failed at least six weeks of conservative nonoperative treatment including pain management and physical therapy.
• The condition is documented by imaging (MRI, CT, or X-rays) showing disc herniation, osteophyte formation, or visible loss of disc height.
• The patient must have intractable radicular pain or myelopathy with nerve root or spinal cord compression symptoms.
• Devices are approved for reconstruction of cervical discs following discectomy.

Contraindications

• FDA
• More than two diseased levels,
• Segmental instability
• Severe spondylosis or facet joint degeneration
• Significant kyphotic deformity
• Osteoporosis
• Prior cervical surgery at the index level
• Disc height less than 3 mm

Implant

• Articulation
• Articulating (3 components, 2 components)
• Non-articulating

• Bearing designs
• Constrained: Physical stop device within physiological range of motion, greater stability
• Semi-constrained: Physical stops outside physiological range of motion
• Unconstrained: Without physical stop, greater mobility at expense of stability

• Bearing types
• Metal on polymer
• Metal on metal
• Polymer on ceramic

• Material
• Stainless steel: Rarely used, not MRI compatible
• Cobalt Chrome
• Titanium

• Implant-bone interface
• Keels, spikes, wire mesh
• Increased porosity, specific coating, screws

• Articulating design
• Ball & Socket: Allows rotation around one point
• Saddle: Allows >1 center of rotation

Surgical technique

Makhni 2019.pdf

4041.3KB

• Patient Positioning:
• Ensure proper patient positioning to enable perfect intra-operative AP and lateral X-rays, which are vital for optimal implant function.
• Ensure perfect facet overlap is achieved on lateral X-ray
• Compare patient positioning to standing pre-operative images and confirm with AP and lateral fluoroscopy to achieve correct alignment and rotation, ensuring the level of interest is neutral.
• Secure the patient's head with tape over the forehead, chin, and above the lips to maintain the position throughout the procedure.
• Perform imaging at multiple times during the case: Rotate the bed as needed to ensure the patient is perpendicular to the floor.
• At level confirmation
• Trial implantation
• Implant implantation
 


 

• Surgical Approach:
• For implants that may be prominent ventrally, avoid fully removing the ventral overhang from the cephalad vertebrae to help contain the implant and prevent it from being ventrally prominent or necessitating a smaller implant.

• Caspar Pin Insertion:
• After inserting Caspar pins just a few threads, confirm their centering and correct trajectories with AP and lateral X-rays.
• Centred pins serve as a midline reference.
• Between the uncinates
• Get assistant to stand end of bed to check for midline and also midline rotation
• Insert Caspar pins straight perpendicularly to the vertebrae in the coronal plane.
• In the sagittal plane,
• Caudal pin should have a standard ~15° cephalad angulation to match the endplate angle,
• Cephalad pin should be inserted more directly without as much cephalad angulation to avoid obstructing implant insertion.
• Insert pins as far as possible from the disc space without violating the adjacent disc space to ensure adequate room for arthroplasty jigs.
• For two-level procedures, (C4/5 and C5/6)
• The placement of Caspar pins for the second arthroplasty can be clinically referenced off the first implant after confirming its good position.
• Place the first pin in C5 and C6 then move the C5 pin to C6.

• Endplate Preparation:
• Prepare endplates to "artistic perfection" so they are microscopically flush and parallel, which is imperative for optimal biomechanics and centered, flush implant placement.
• After preparing the disc space with distracted Caspar pins, release the distraction and inspect for parallelism, as even a millimeter off-centre can lead to uneven distraction.
• Size the arthroplasty to fill the disc space as large as possible from anterior to posterior to optimise biomechanics.

• Implant Preparation and Insertion:
• Ensure that each tool, such as rasps and trials, is inserted in a similar manner to prevent endplate violation and prepare the space identically to the desired implant position.
• Sizing
• Insert the largest possible implant in terms of both width and depth.
• Depth should be estimated on pre-operative imaging and confirmed with intra-operative radiographs using the trials
• The implant height should be nearly the same as the pre-operative disc height, or the smallest implant height close to it.
• For devices with rails, carefully cut channels into the endplates.
• If the endplates are sclerotic, the rails cannot cut channels in the endplates
• This can be noticed when
• The rails are not fully penetrating the endplates symmetrically and fully,
• The disc space is opening up while the tool is being inserted
• If rails are not fully penetrating,
• Release distraction from the Caspar pins once the jig is partially inserted.
• Rock the rail-cutting guide back and forth into the endplates for adequate penetration.
• Use a drill that is provided with the set
• Make sure the drill guide is fitted into place properly
• remove casper distraction so that drill do not skive off the bone
• After removing the guide, use a small, curved microcurette to remove any bone dust or particles stuck in the channels to ensure the final implant slides smoothly.

• Decreasing Likelihood of Fusion (The most common complication):
• Denude the vertebral body 1cm above and below the disc space with monopolar and covering it bone wax.
• Avoid violating the endplates during preparation as this exposes cancellous bone, causes bleeding, and increases fusion risk.
• After discectomy, remove the posterior longitudinal ligament (PLL) and bipolar cauterise its remaining ends to prevent traction spurs and ossification of the PLL (OPLL).
• Thoroughly irrigate out all bone dust from the site.
• Address all bleeding bone (except the endplate where the arthroplasty bonds) with bone wax throughout the procedure to decrease growth factors that promote fusion and minimise haematoma formation.
• Fill Caspar pin sites with bone wax.
• When an uncinatectomy is performed, use bone wax liberally in areas not in contact with the arthroplasty endplate to prevent fusion and osteophyte regrowth.
• Do not apply wax where the arthroplasty bonds to the endplate.
• After implanting the arthroplasty, strip the anterior periosteum approximately halfway to the adjacent discs and wax the bone and the front of the arthroplasty to prevent anterior bone spur formation.
• Maintain meticulous haemostasis to minimise haematoma risk and decrease circulating growth factors.
• Wrap the released edges of the longus colli muscles with a haemostatic agent (e.g., Surgicell).
• Use a Penrose drain in all cases instead of closed suction drainage to reduce the risk of clotting in smaller drain holes.
• For outpatient procedures, suture the drain to the dressing for easy patient removal at home.

• Irrigation (emphasised as crucial):
• Irrigate all bone dust from the site meticulously prior to disc implantation to significantly reduce the risk of undesirable ossification.
• Use at least 300–400 cc of irrigation with both a 20-cc syringe (with an 18-gauge angiocath for high-pressure spot irrigation) and a 60-cc bulb irrigation syringe.
• Continue irrigating until "every little speck of bone dust is gone".

Outcomes

• Sasso 2024: 20 year outcome of an RCT, for cervical radiculopathy
• Both CDA and ACDF are effective in treating cervical radiculopathy with sustained improvement in NDI (p=0.087), VAS neck (p=0.073) and VAS arm (p=0.095) pain at 20 years.
• CDA (10%) demonstrates lower reoperation rates than ACDF (42%).
• There were no failures of the arthroplasty device requiring reoperation at the index level.
• The symptomatic nonunion rate of ACDF was 4.2% at 20 years.
• There was a significant difference between CDA versus ACDF groups
• Change in VAS neck pain score between 10 and 20 years [respectively, -0.4 (SD 2.5) vs. 1.5 (SD 2.5), p=0.030].

• Quinto 2024: Meta-analysis of 10 year outcome:
• Significantly fewer secondary surgeries and adverse events were seen after CDA than after ACDF at 10-year follow-up.
• CDA had statistically, but not clinically, improved neck disability index and visual analog scale scores
• CDA had lower JOA Japanese Orthopaedic Association scores in comparison to ACDF.
• CDA was not significantly different from ACDF in terms of a successful neurological outcome.

Complications

Heterotropic ossiciation,

Bone lysis

Implant failure