OPERAMinimally invasive
open-door laminoplasty

The indication is the same as ordinary cervical laminoplasty for cervical spondylotic myelopathy and cervical ossification of the posterior longitudinal ligament. The authors previously required an incision of around 10 cm, but after shifting to ExLAP they use a 30-35 mm incision for C3-6 cases.

During the initial introduction, it is preferable to start with a larger incision and reduce the incision length according to the learning curve. When stenosis extends from C2/3 to C6/7, C3-6 laminoplasty combined with C2 or C7 domeplasty can address the lesion while completely preserving the semispinalis cervicis at C2 and C7.

Because the procedure is performed through a small incision while preserving soft tissue, the overall anatomy is difficult to grasp directly. Preoperative CT is used to confirm the thickness of each lamina, and 3D images are used to confirm spinous-process morphology and facet osteophytes so that the surgeon can plan spinous-process splitting and gutter creation in advance.

The authors use XR navigation as needed to understand cervical anatomy. For the procedure, they prepare a blunt right-angle Gelpi retractor, a compact high-speed burr, and a right-angle suction tube with appropriate strength and a non-sharp tip.

After carefully confirming alignment on a preoperative lateral radiograph, the head is fixed with a Mayfield skull clamp in a neutral to mildly flexed cervical position. Both shoulders are pulled downward with tape to make it easier to confirm the operative level.

Positioning is extremely important in small-incision surgery. In particular, when preoperative alignment is straight to kyphotic, ordinary positioning may create excessive kyphosis and make the operation difficult.

The surgeon stands on the patient's left side. The C2 and C7 spinous processes are palpated, and a two-fingerbreadth incision is designed. Usually, because the C3 lamina is prioritized, the incision is placed from the C3 spinous process toward the caudal side for two fingerbreadths. As a result, the incision is often placed approximately over the C3-5 spinous processes.

The midline over the nuchal ligament is accurately opened with electrocautery to reach the midline of the C3-6 spinous processes. At this point, the level is confirmed fluoroscopically. A blunt right-angle Gelpi retractor is then placed.

Using a 3 mm high-speed diamond burr, the tips of the C3-6 spinous processes are split from the midline to both sides while preserving the semispinalis cervicis attachment. The C3-6 laminae are exposed bilaterally with electrocautery. Exposure of the lateral masses is limited to the gutter position and kept as minimal as possible.

The semispinalis cervicis at C2 is completely preserved. The lower edge of the C2 lamina and the upper edge of the C3 lamina are exposed with a high-speed burr, and the C2/3 ligamentum flavum is exposed. If there is no stenosis at C2/3, the ligamentum flavum is detached from the C3 lamina using a curved curette from the upper edge of the C3 lamina.

If stenosis is present at C2/3, domeplasty of the lower edge of the C2 lamina is performed with a 3-4 mm high-speed burr until the ligamentum flavum can be detached, and the ligament is detached on the C2 laminar side. During C2/3 work, the exoscope camera is angled most cranially.

The gutters of the C3-5 laminae are created with a high-speed burr. The right side is used as the hinge side and the left side as the open side. On the open side, drilling is performed while cooling with saline as needed to avoid thermal injury. When the surgeon operates alone, a burr with a nozzle that drips saline is preferable.

For the C6 lamina, the gutter is created only on the hinge side, and the procedure then proceeds to the C6/7 interlaminar window. It is efficient to create the gutters with a continuous single-stroke concept.

At C6/7, the field is viewed downward toward the caudal side, so the lower edge of the C6 lamina obstructs the view and makes it difficult to reach the C6/7 ligamentum flavum. Removing a few millimeters of the distal C6 lamina with a high-speed burr makes the C6/7 ligamentum flavum easier to identify.

The upper edge of the C7 lamina is also exposed with a high-speed burr, and the ligamentum flavum is detached from the C7 lamina using a curved curette from the upper edge of C7. If stenosis is present at C6/7, the upper edge of the C7 lamina is removed as much as necessary with a high-speed burr or a 2 mm Kerrison rongeur.

After completing the C6/7 interlaminar window, the open side of the C6 lamina is cut. During C6/7 work, the exoscope camera is angled most caudally.

Because the visual field is limited in this technique, fixation with only sutures or fixation of an HA spacer with sutures or anchors is difficult. Various plate systems can be selected, but the author uses the OPERA SYSTEM from Symphony Medical Co. Ltd. because it is suited to minimally invasive techniques.

The plate has a very compact design that makes it easy to handle through a small incision. Because the screws achieve good purchase, the plate can be placed while preserving soft tissue. The laminar side of the plate can be bent easily so that it fits the shape and individual variation of the lamina.

Each lamina is lifted with a curved curette, and the plate is placed. The ligamentum flavum on the open side is generally not cut before lifting the lamina. If lamina elevation feels stiff, the hinge-side gutter is deepened, and it is important not to force the lamina upward.

Each screw hole is created with a 1-2 mm high-speed burr. The plate is fixed with two screws on the lateral-mass side and two screws on the laminar side. In small-incision surgery, postoperative activity tends to be high, and because the posterior cervical muscles are fully preserved, pressure from soft tissue can make reclosure of the opened lamina more likely.

After thorough irrigation, a 3.5 mm closed continuous suction drain is placed and the muscle layer is sutured. By having an assistant or scrub nurse retract the Gelpi retractor, the cranial and caudal ends of the muscle layer can be sutured under direct vision even through a small incision.

Because the author performs the operation alone, STRATAFIX, which allows tight continuous suturing, is used frequently. Subcutaneous suturing is performed, and Steri-Strips are applied at the end. In the authors' department, rehabilitation begins the day after surgery and early mobilization is started.

Because exoscope images are first converted into digital data, a new interface combining the exoscope with support devices such as XR is expected. CT navigation images can be displayed on the exoscope monitor as picture-in-picture.

By projecting the exoscope's 3D monitor image onto smart glasses, the operative field and the 3D image on the glasses can be checked with minimal eye movement, and the monitor installation space can be reduced. At present, however, smart glasses have lower resolution than flat monitors and are heavy, so issues remain for clinical use.

A head-mounted display is a wearable display with pass-through capability, and when linked with an exoscope it is expected to be useful in magnified-view surgery. For education, including surgical training and remote operative support or observation, practical use is possible if the internet environment is available.