Laminoplasty

General

Laminoplasty aimed at reconstructing the vertebral lamina to expand the spinal canal, specifically by creating hinges on which the lamina is lifted rather than removed entirely.

Reconstructive laminoplasty:

Lamina is completely removed and then reattached
Used for paediatric intradural procedures.

It was initially developed to address unsatisfactory outcomes observed with laminectomy for multilevel cervical myelopathy.

Cervical Alignment:

While a lordotic alignment is not a strict prerequisite, laminoplasty is most effective when the cervical spine maintains lordosis. Patients with lordotic or straight spines, or even up to 13 degrees or less of kyphosis (without cord signal change on T2-weighted MRI), are considered ideal candidates.
If there is cord signal hyperintensity, the upper limit of acceptable preoperative kyphosis is 5 degrees or less.
Laminoplasty can still improve myelopathy even in the presence of kyphosis, particularly if decompression of more than three levels is required, as extensive anterior decompression and fusion carries a higher risk of complications.

Indication

Multilevel Cervical Spondylotic Myelopathy:

>2 motion segments.

Ossified Posterior Longitudinal Ligament (OPLL):

A positive K-line (where the OPLL lesion does not cross the line connecting the midpoints of the spinal canal at C2 and C7) is a crucial tool for determining the success of laminoplasty in OPLL cases, as it correlates with significantly higher neurological recovery rates.
However, if the OPLL thickness exceeds this K-line, clinical improvement may be unsatisfactory.

Developmentally Narrow Spinal Canals:

It is particularly well-indicated for patients with a developmentally narrow spinal canal, defined by a midbody anterior-posterior (AP) diameter of less than 12 mm.

Salvaging Failed Anterior Cervical Decompression and Fusion (ACDF)

Recurrent Myelopathy due to Adjacent Segment Disease:

It is indicated for recurrent myelopathy that arises from adjacent segment disease after a previous ACDF.

Patients at Increased Risk for Nonunions:

It serves as a primary treatment for myelopathy in individuals who are at an increased risk for nonunions, such as smokers and patients with metabolic bone disease.

Pros of Cervical Laminoplasty

Avoids Morbidity and Graft Complications of Anterior Surgery:

Preserves Cervical Motion:

Potential Lower Risk of Adjacent Segment Degeneration: Theoretically, as a motion-preserving procedure, laminoplasty may lower the risk of adjacent segment degeneration, which is commonly seen in anterior cervical fusion surgery.

Direct Neural Decompression

Indirect Neural Decompression:

By allowing the spinal cord to drift dorsally away from retrodiscal and/or retrovertebral disease.

Prevents Scar Compression:

Prevent the "postlaminectomy membrane" or scar from compressing the spinal cord.

Protection Against Future Traumatic Injury:

Good Neurologic Recovery Rates:

Reported neurologic recovery rates 10 years following laminoplasty range from 50% to 72%.

Generally Successful with Low Complication Rate:

Laminoplasty is generally successful and considered a safe and effective treatment for symptomatic cervical myelopathy with a relatively low complication rate.

Low Revision Rates:

Ranging from 0% to 8% over 5 to 10 years.

Cons of Cervical Laminoplasty

Potential Need for Revision Surgery

Although generally successful, failures can occur due to disease progression, technique-related factors, and inadequate symptomatic relief, potentially requiring revision surgery.
In a 10-year study, 9.2% (12 out of 130 patients) required revision surgery.
The mean time interval between the initial laminoplasty and revision surgery was 16.6 months (range, 4–43 months).

Common Drawbacks and Complications:

Postoperative Axial Symptoms/Pain: Patients may experience postoperative axial symptoms or neck pain. The decision for revision surgery for axial pain is controversial due to uncertainty of its origin.
Reduced Range of Motion (ROM): A reduced range of motion is a known drawback. Cervical ROM can decrease over time.
C5 Motor Palsy:

This is another noted complication.
C5 motor palsy

is often self-limiting, making revision surgery for it controversial.
Due to drifting of the spinal cord backwards after decompression → traction of the C5 nerve root (shortest therefore greatest tension)

Technique

Oyama and Hattori's Expansive Z-Laminoplasty (1972)

Old technique less used

This was the initial technique developed to counter unsatisfactory outcomes of laminectomy for multilevel cervical myelopathy.

It involved thinning the laminae and then making z-shaped cuts in each lamina.

These split laminae were then lifted from the spinal canal and fixed with sutures to reconstruct and expand the spinal canal. Early reports indicated neurological improvement in all treated cases.

Hirabayashi's Open-Door Laminoplasty (1977)

Drilling bony gutters bilaterally at the lateral borders of the laminae, near the pedicles.

On one side, the bone at the lamina border is completely excised, while on the other side, a thinned inner cortex is preserved to act as a hinge.

The laminae are then pushed laterally towards the hinge side, similar to opening a door, thereby enlarging the spinal canal.

Sutures are used to support the yellow ligaments and deep muscles around the facets of the hinge side to prevent the "laminar door" from closing.

This technique is noted for requiring only two troughs, making it potentially more time-efficient than the French-door procedure, and it is easier to perform supplemental foraminotomies on the open side.

Kurokawa's Spinous Process Splitting (Double-Door / French-Door) Laminoplasty (1980):

This method involves splitting the spinous processes and laminae down the midline.

Hinges are created bilaterally along the lateral borders of the laminae.

The laminae are then lifted bilaterally, like a "French-door" or "double-door," to expand the spinal canal.

A meta-analysis found no significant difference in clinical improvement between open-door and double-door laminoplasty techniques.

Variations and Modifications:

How the expanded lamina is held open:

Sutures or wire tethering the hinges open.

Early methods

Bone grafts (autologous) or other spacers like ceramic or polyethylene blocks
Plates and screws (e.g., titanium miniplates) to securely fix the laminae in place, which can help reduce the risk of laminar closure and hinge failure.

The use of plates without additional bone grafts has shown high hinge healing rates and maintenance of canal expansion.

‘‘C3 Dome-Hybrid Open-Door Laminoplasty and C7 reverse dome

General

Hybrid laminoplasty consists of a C3 dome-like osteotomy, C4–6 instrumented open-door laminoplasty, and C7 upper laminectomy or C7 dome-osteotomy.
This technique is generally not recommended for patients with contraindications to traditional laminoplasty, spinal cord compression exceeding 50% of the spinal canal, or lesions extending beyond C2/C3 cephalad or T1 caudal.

Achieve indirect decompression of the spinal cord from C3 to C7 spinal levels.

Pros

designed to preserve muscle attachments and reduce complications associated with conventional laminoplasty.

Anesthesia and Positioning:

Prone, GA
IOM: particular attention to deltoid electrode placement to detect C5 palsy.

C3 Dome-Osteotomy:

A midline posterior surgical incision is made.
Interspinous ligaments at C3/C4 and C6/C7 are removed.
1/3-1/2 of the caudal C3 spinous process and the cephalic part of the C7 spinous process are removed using a rongeur to improve exposure. Precaution is taken to avoid muscle detachment at the cephalic and caudal parts of the C3 and C7 spinous processes.
A Burr is used to thin out the lamina at C3 and C7 without completely burring through until a crack in the lamina is visible and the ligamentum can be felt.

This thin layer of lamina and flavum protects the spinal cord.

The burr is then used to create a dome-shape cut or ‘‘dome-osteotomy’’ along the undersurface of the remaining C3 spinous process onto the cephalad C3 lamina.

Copious irrigation is used to clear bone dust and reduce thermal injury.

A sharp nerve hook, followed by a ball tip nerve hook, is used to extend and widen the lamina crack, separating any dura adhesion from the lamina.
A 1 to 2 mm Kerrison is carefully used to remove the remaining lamina and flavum without exerting pressure on the spinal cord.
To ensure adequate C3 lamina removal, a short length angled ball tip nerve hook is used for confirmation. If the hook tip can be rotated easily cephalad to the remaining C3 lamina when placed perpendicularly to the dura surface and cannot be pulled back (blocked by the lamina), the C3 decompression is confirmed as complete.

C7 Partial Laminectomy or C7 Dome-Osteotomy:

A similar technique to C3 is used at the C6/C7 vertebral junction.
An upper C7 laminectomy can be performed if cord compression does not extend beyond the upper one-third of the C7 vertebral body.
Partial laminectomy (up to 25%) is performed at the end of the C7 lamina to minimise damage to the trapezius muscle.

Open Door Laminoplasty (C4-6):

Two gutters are created at each side of the lamina-facet junction at the C4, C5, and C6 laminae.
One side of the lamina is completely cut through, and the other side is partially cut to create a hinge.
Foraminotomy at C4/C5 is performed if C5 EMG signals are noted during surgery or if significant C4/C5 foraminal stenosis is present.
A laminoplasty plate is used to ensure adequate opening of the lamina, with large-sized 14 plates preferred at all spinal levels for sufficient canal decompression.
Seven-millimetre screws are used to prevent screw backout or facet joint penetration.
A postoperative drain is placed, and multilayer wound closure is performed, with 1g of vancomycin powder instilled locally.
A soft cervical collar is used for 1 week postoperatively.

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Outcome

Changes in Spinal Alignment Post-Laminoplasty:

Reduced Lordotic Alignments: Up to 80% of patients may have reduced lordotic alignments at the C2–C3 and C6–C7 junctions after a C3–C7 laminoplasty at 3-year follow-up.
C2–C3 Auto-Spinal Fusion: This has been noted to occur in up to 79% of patients.

Neurological Improvement:

Early reports on Hirabayashi's open-door laminoplasty showed good results, with a recovery rate of 66% on the Japanese Orthopedic Association (JOA) scale. Other studies have reported similar neurological recovery rates, with improvements remaining stable for over 10 years in most patients.
Clinical improvement after laminoplasty for cervical myelopathy or radiculopathy has been found to be essentially the same as that achieved after laminectomy with or without fusion, or anterior cervical discectomy or corpectomy with fusion.
In cases of OPLL, a positive K-line (where the OPLL lesion does not cross the line connecting the midpoints of the spinal canal at C2 and C7) correlated with a significantly higher average neurological recovery rate of 66% after laminoplasty, compared to 19% in cases with a negative K-line.

However, if the OPLL thickness exceeds the K-line or the focal kyphosis angle is larger than 13°, clinical improvement may be unsatisfactory.

Range of Motion (ROM):

Shorter bed rest and cervical orthosis use, along with early neck ROM exercises, seem to result in less long-term restriction of ROM.
Early laminoplasty techniques, often involving prolonged postoperative immobilisation, led to a significant decrease in ROM, with reports of 53% loss at 1 year and 35% loss at 7 years post-surgery. For patients with OPLL, ROM decreased from 36° to 8° at a mean follow-up of 153 months.
However, modern practices, particularly muscle-preserving techniques and encouragement of early active ROM exercises, have shown better preservation of motion.

Studies have shown ROM decreases from 40.1° to 33.5° (87.9% preservation) at an average follow-up of 33.3 months.
Kim's myoarchitectonic spinolaminoplasty, which preserves all posterior muscle attachments, resulted in ROM being 67.7% of the preoperative value at 1 year post-operation.

Kyphosis Development:

Postoperative cervical kyphosis has been reported less frequently after laminoplasty compared to laminectomy alone, with an incidence of 0–22%.

Early studies showed no kyphosis development up to 2 years, but others found it in 28% of patients 5 years after laminoplasty, similar to laminectomy.

Risk factor

Prolonged immobilisation
Extensive muscle detachment

Loss of the semispinalis cervicis attachment at C2 is a possible cause.
Preserving muscle attachments to the C2 and C7 spinous processes plays an important role in preventing postoperative kyphosis and maintaining preoperative sagittal alignment.
Techniques like Kim's myoarchitectonic spinolaminoplasty have shown minimal loss of lordosis (0.71° at 1 year) due to preserving posterior muscle attachments.

Axial Neck Pain:

Historically, postoperative axial neck pain was reported in up to 40% of patients at 10-year follow-up.
Pain aetiology

Facet joint injury
Deep extensor muscle denervation
Detachment of C2 and/or C7 muscles

Preservation of muscle attachments at C2 and C7 has been consistently shown to reduce postoperative axial neck pain.
For instance, C3–6 laminoplasty, which avoids C7 detachment, reported a 5.4% incidence of axial neck pain compared to 29% for C3–7 laminoplasty.

Detachment of the nuchal ligament
Prolonged postoperative external immobilisation

Early active range of motion and muscle strengthening postoperatively are also strategies to reduce pain.

Laminar Closure / Re-stenosis:

Laminar closure has been reported with various techniques, including a 34% reclosure rate using the traditional Hirabayashi suture method with early active range of motion.

While short-term outcomes may not be significantly affected, long-term follow-up suggested a tendency for recovery rates to decline in the closure group.

The use of rigid laminar fixation methods, such as plates and screws (e.g., titanium miniplates), helps to reduce the risk of laminar closure.

Plate-only laminoplasty has reported a 93% hinge healing rate at 1 year, with no loss of fixation or premature closure.

Hinge Fracture / Displacement:

This complication can occur if not enough bone is removed (leading to fracture when opening) or too much is removed (resulting in a floppy hinge that can displace into the canal). Either failure can compromise the nerve root or spinal cord.
A diamond burr and careful assessment of hinge stiffness can minimise this risk. In case of fracture, a "hinge plate" or mini-fragment plate can be used for stabilisation.

Motor Root Palsy (e.g., C5 Palsy):

The incidence ranges from 5% to 12%, with the C5 nerve root being most commonly involved.
This complication is not unique to laminoplasty and occurs with similar frequency in other cervical myelopathy procedures, including laminectomy, laminectomy with fusion, and anterior decompression and fusion.
Patients typically present with painless weakness of the deltoid and biceps muscles, manifesting 2–3 days post-surgery, though it can appear up to 2 months later.

Recovery can range from 1 week to 2 years.

Wound Infections:

Reported rates are around 3–4%, similar to other posterior cervical procedures.
Perioperative antibiotics, good surgical technique, watertight fascial closure, and sometimes a separate drain, can minimise infection rates.