Cervical Laminoplasty

“Laminoplasty” refers to multiple surgical procedures that involve reconstruction of the vertebral lamina subsequent to the spinal canal being opened. Typically, the term “laminoplasty” refers to the creation of hinges that allow lifting of the lamina without its complete removal.

The purpose of cervical laminoplasty was to prevent issues that often arise from laminectomy, such as postoperative segmental instability, kyphosis, perineural adhesions, and delayed neurological deterioration.

The initial method of laminoplasty was a modification of Kirita’s laminectomy technique, involving the use of an air drill to thin and partially remove the laminae along the midline.

History

The edges of the laminae situated near the pedicles are additionally thinned until they become flexible enough to be bent and lifted. Swift lifting of multiple laminae is deemed crucial to facilitate decompression of multiple segments of the cord at once. Subsequently, the laminae were excised using scissors.

Subsequently, the z-plasty technique for laminoplasty was developed. Once the laminae were thinned, z-shaped incisions were made in each lamina. These laminae were then lifted and secured with sutures to reconstruct the widened spinal canal, resulting in observable neurological improvement following the procedure.

A modification of en bloc laminectomy, involving bilateral cutting of the laminae along the hypothetical line that separates the laminar arches and articular processes, resulting in their complete detachment from their bony connections, has been documented in the literature.

The laminae were reflected to create a flap and left to float on the cord without the use of fixation sutures or bone grafting. Expansive open-door laminoplasty involves the bilateral drilling of bony gutters along the laminae border that corresponds to the medial section of the pedicles.

The lamina border is removed on one side, and the laminae are then pushed laterally towards the other side in a manner that resembles 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.

According to another literature source, a modified laminoplasty technique has been developed that involves splitting the spinous processes and laminae along the midline. Bilateral hinges are then created along the lateral borders of the laminae, which are subsequently lifted.

While numerous “new methods” of laminoplasty have been described in the literature, the fundamental approach to expanding the spinal canal can be categorized into either the open-door technique, which involves a hinge on one side, or the double-door technique, which utilizes hinges on both sides.

Various modifications have been devised to prevent the expanded lamina from closing, such as the use of sutures, autologous bone grafts, hydroxyapatite or other ceramic materials, titanium miniplates or spacers, allograft and titanium plates, as well as hydroxyapatite and screws.

Postoperative kyphosis and neck pain can arise from the detachment of posterior cervical muscles during laminoplasty surgery. Initially, some authors suggested detaching and then reattaching the semispinalis cervicis muscle on the C2 spinous process.

However, later studies concluded that preservation of the attachment was a better option. It was noted that maintaining the muscle attachments on the spinous processes of C7 was also significant.

Various techniques were developed to preserve muscle attachment on the spinous processes, including one in which the spinous processes and laminae were exposed on one side via subperiosteal dissection, enabling preservation of the attachment of the semispinalis muscles on one side of the spinous processes.

A prospective randomized study found that the technique of preserving muscle attachment on the spinous processes resulted in a significant decrease in axial pain, when compared to open-door laminoplasty where muscle attachments were completely dissected.

Before this advancement, only the bony structures were reconstructed and the muscles that were responsible for maintaining both static and dynamic motor functions were not typically preserved.

Various techniques have been developed in the literature to protect crucial neck muscles’ attachments during laminoplasty, enabling efficient spinal canal enlargement while retaining the musculoskeletal elements of the posterior neck.

The implementation of myoarchitectonic spinolaminoplasty led to an increase in neurosurgical cervical spine scores, minimal loss of lordosis after surgery, and a low incidence of axial neck pain. Further clinical studies are required to validate whether this development can address the concerns about postoperative instability and reduced range of motion that were identified in previous posterior decompression procedures.

Indication for Laminoplasty

Laminoplasty is a method of decompressing the spinal cord through a dorsal approach that is particularly effective when the lordosis of the cervical spine is maintained.

Laminoplasty is recommended for patients who have cervical spinal canal stenosis, continuous OPLL, and multiple spondylotic lesions, particularly in the lordotic cervical spine. Laminoplasty is indicated for patients with cervical kyphosis who require decompression of more than three levels, as it can improve myelopathy even in the presence of kyphosis.

Clinical improvement after laminoplasty may not be satisfactory if the focal kyphosis angle is more than 13° or if the thickness of OPLL is beyond the K-line. In such cases, the most compressed segment can be subjected to anterior decompression with fusion after laminoplasty.

Postoperative Outcome

Various scales, including the Nurick grade, JOA scale, and Neurosurgical Cervical Spine Scale (NCSS), are used to assess the clinical status of cervical myelopathy. The recovery rate is determined by calculating the difference between the JOA scale score before and after surgery and expressing it as a percentage.

In one study, laminoplasty was found to have good results in improving neurological recovery in patients, with a reported recovery rate of 66%. Neurosurgical literature commonly employs NCSS to describe the status of patients due to its clear and simple nature.

Kyphosis Development

Literature has shown that laminoplasty may result in kyphosis development in some patients, although the incidence of this varies between studies. Preserving the functionality of the posterior musculature can prevent the loss of cervical lordosis.

Maintaining the functional preservation of the posterior musculature is crucial because it is responsible for the mechanical force that maintains cervical lordosis, with the semispinalis cervicis and capitis playing a significant role in this. Myoarchitectonic spinolaminoplasty has been observed to lead to the least loss of lordosis, presumably due to the preservation of all posterior muscle attachments.

Biomechanical Studies

According to biomechanical studies conducted on cadavers, the range of motion in response to physiological load increased after laminectomy with or without foraminotomy. However, open-door laminoplasty did not significantly differ from the intact spine in terms of range of movement.

Double-door laminoplasty demonstrated a higher level of stability in the cervical spine compared to laminectomy. However, the load to failure was lower in the spines after laminoplasty. Kyphotic deformity was observed in animal studies after laminectomy in goats and rabbits, while laminoplasty did not result in such deformities.

The results of clinical studies were inconsistent, with some studies demonstrating no significant difference between laminectomy and laminoplasty, while others showed that laminoplasty was associated with better outcomes. The inconsistent results between laminectomy and laminoplasty in clinical studies may be attributed to the failure of laminoplasty procedures to maintain or rebuild muscle attachments.