Advantages

Conventional open operating procedures are indispensable today and will remain so in the future. The possible complications of and injuries from such procedures are known [12–19]. At the least, new techniques must be as capable of attaining the operative goals as the established procedures [4].

The fully endoscopic uniportal interlaminar operation, as a truly minimally invasive procedure, offers advantages over conventional procedures, listed later. They correspond largely to the advantages of microscopically assisted surgery, cited in each case, over conventional open surgery. The fully endoscopic interlaminar operation can thus be classified as the next step in technical advances in surgical techniques. There is, as yet, no unequivocal scientific proof of this assertion, but such proof is also lacking for microscopically assisted operating and arthroscopic techniques.

The advantages of the fully endoscopic uniportal interlaminar operation over a conventional open procedure are as follows:

Good presentation of structures, excellent visual conditions, improved illumination

Expanded field of vision thanks to 25-degree-angle optics

Sufficient working space within the spinal canal and its adjacent structures

Sparing of epidural lubricant tissue, with reduced epidural scarring

Minimized bony and ligamentous resection, according to current knowledge, resulting in reduction of operation-induced instabilities

No greater difficulty of subsequent operations

No operation-related increase in back pain

Reduced traumatization of the surrounding tissue

Lower rate of complications, such as dural injury, bleeding, and infections

Short hospitalization, rapid rehabilitation, high rate of return to athletic and occupational activity levels

No increase in morbidity of concurrent diseases or advanced age

High patient acceptance

Can be used in technically inoperable transforaminal pathologies

Good visibility for assistants

Disadvantages

With complete omission of bony resection in the fully endoscopic uniportal interlaminar operation, the mobility within the spinal canal is limited by the size of the interlaminar window. At spinal levels L5 through S1, the dimensions of the window often hinder access if no bone is removed. Greater bony resections with high-speed drills or larger punches are technically more demanding in minimally invasive procedures than in conventional procedures.

Unlike the transforaminal access, the interlaminar procedure requires a defect in the ligamentum flavum and a potential resection of bony structures, despite being minimally invasive. Thus,the fully endoscopic uniportal transforaminal operation can be rated as less traumatizing and may offer advantages in appropriate indications and when its clear limits are taken into account.

Indications

The indications for the operation correspond to today’s valid standards [20]. Most experience has been gained in the therapy of disc herniations and lateral spinal canal stenosis. Extensive central spinal canal stenosis has been operated on for only a short time, and the procedure is still under development. Existing concurrent pathologies, such as instabilities, must be treated at the same time as appropriate. The following indications are currently clearly defined:

Sequestered or nonsequestered disc herniations within the spinal canal: In the case of extensive dislocation to the next level, a two-level procedure may be performed; in the case of a herniation in combination with intraforaminal-extraforaminal prolapses, an additional fully endoscopic transforaminal operation may be performed.

Recurrent disc herniations after conventional or fully endoscopic operations.

Lateral bony and ligamentous spinal canal stenosis.

Cysts of the zygapophyseal joint.

Intervertebral monosegmental fusions in combination with percutaneous dorsal stabilization: An interlaminar procedure is performed instead of a transforaminal only when decompression within the spinal canal is necessary or when a transforaminal procedure is not technically possible.

Contraindications

In addition to general surgical contraindications, the following conditions are currently considered contraindications to the fully endoscopic interlaminar procedure because of a lack of experience or technical limitations:

Compressing intraforminal or extraforaminal pathologies: In this case a fully endoscopic transforaminal or extraforaminal procedure with posterolateral to lateral access is indicated.

Extensive central spinal canal stenosis.

Fusions in instabilities that cannot be reduced by positioning or in spondylolysis; conventional systems must be used in such cases.

Multisegmental fusions.

Cauda equina syndrome, for which a conventional procedure should be considered, especially for legal reasons.

Preoperative preparation

Examination

The decision for surgery must be made according to today’s standard on the basis of radicular pain symptoms and existing neurologic deficits [20]. Isolated back pains cannot usually be improved by decompressing operations.

Diagnostically, depending on the findings, the entire operative and clinical considerations must be taken into account, as in conventional procedures.

Conventional two-plane radiographs of the lumbar spine and magnetic resonance imaging with sagittal and transverse reconstructions are obligatory.

Informed Consent

Patients must be informed about their disease and its possible long-term course and consequences. Despite the minimal invasiveness and attendant advantages of the surgical procedure, all known side effects, complications, and therapeutic possibilities must be explained, as would be done for conventional procedures [21].

With reference to the fully endoscopic procedure, it must be pointed out that even with minimally invasive interventions, scarring cannot be completely avoided, and the extent of scarring will depend on the possible need to expand the surgical procedure.

With long operating times and in cases in which the lavage fluid outflow is overlooked, the consequences of elevated pressure within the spinal canal and its connected and adjacent structures theoretically cannot be completely ruled out as a possible risk.

In addition, it must be pointed out that a switch to an open procedure may be required during the operation or later in an additional procedure if unforeseen complications arise.

Procedure

As with all microsurgical techniques, the intraoperative procedure must be planned on the basis of the imaging findings. The goal is to perform resection while sparing the spinal canal structures as much as possible, depending on the pathology. This applies especially to the selection of the access in relation to the size of the interlaminar window and the craniocaudal level of the interlaminar window in relation to the extent of the pathology.

The fully endoscopic interlaminar operation is usually performed with the use of general anesthesia.

2. The patient is in the prone position on an x-ray–permeable table under orthograde, two-plane radiologic control. To relieve the pressure on abdominal and thorax organs, the patient is placed on a thorax and hip rolls (Fig. 27-5).

Figure 27–5 The patient is placed in the prone position with use of thorax and hip rolls.

The operating table is lordotically or kyphotically adjustable intraoperatively at the lumbar level as needed, depending on the anatomy and pathology.

Figure 27–6 Marking the entry point on the skin under anteroposterior fluoroscopic control.

Figure 27–7 The skin incision should be as medial as possible to enable entry under the tilted zygapophyseal joints later in the procedure.

Figure 27–8 The stab incision may be extended to the muscle fascia if needed to facilitate insertion of the dilator.

Figure 27–9 The dilator is inserted to the ligamentum flavum or the bony boundary of the zygapophyseal joint.

Figure 27–10 The position of the dilators can be checked fluoroscopically.

Figure 27–11 Lateral fluoroscopic guidance shows the dilator in the second plane.

Figure 27–12 The operating sheath with beveled opening is inserted through the dilator toward the ligamentum flavum.

Figure 27–13 The position of the operating sheath can be checked in lateral fluoroscopic view.

Figure 27–14 The operating sheath is in its final position, with the opening turned medially, opposite the sheath grip.

Figure 27–15 After the endoscope is inserted, the rest of the operation is performed under fluoroscopic guidance and with continuous lavage flow.

Figure 27–16 The ligamentum flavum is incised as laterally as possible to keep the medial defect as small as possible.

Figure 27–17 The neural structures are exposed prior to decompression.

The further operative steps depend on the pathology, as follows:

Disc herniations, cysts of the zygapophyseal joint, and lateral spinal canal expansions can usually be corrected without further access-related resections.

In extended sequestered dislocations, the resection of segments of the lamina either cranial or caudal to the current segment may be necessary before the ligamentum flavum is opened, in accordance with preoperative planning (Fig. 27-18).

The defect in the ligament can be kept small because of the elasticity of the band.

Figure 27–18 If needed, it is possible to remove bone, as is being done here.

As in conventional surgery, the specific intraoperative procedure depends on the findings, as follows:

The operating sheath with beveled opening can be used as a second instrument and as a nerve hook. Turning the opening allows the neural structures to be held aside and protected (Fig. 27-19).

Mobility within the spinal canal is controlled with the use of the optics, on the joystick principle (Fig. 27-20).

Various rigid and flexible instruments of different sizes, as well as shavers and burs, are available for each working step (Fig. 27-21).

Radiofrequency bipolar current is used for preparation and hemostasis. Use of holmium:yttrium-aluminum-garnet (Ho:YAG) laser ablation is not necessary.

At the end of the operation, the instruments are removed and the incision closed. No drainage is required.

Figure 27–19 The operating sheath with beveled opening (A) can be used as a second instrument and as a nerve hook. Turning the opening (B) allows the neural structures to be held aside and protected. The operating sheath serves as a second instrument and shifts the neural structures medially by turning the opening (C). The white protruded intervertebral disc can be seen below the shifted neural structure in a 6 o’clock within the operating sheath with beveled opening (D).

Figure 27–20 Control of the entire optic system on the joystick principle provides the required mobility.

Figure 27–21 Various instruments are available for each working step; for example, the endoscopic forceps shown here.

In revision operations, the dilator is inserted further laterally until it makes contact with the bony segments of the zygapophyseal joint in order to avoid damage to neural structures due to an already existing defect in the ligamentum flavum. From this “safety zone,” preparation is made under fluoroscopic guidance as the operating sheath with beveled opening is inserted medially, then directly at the bone boundary toward ventral until the ventral boundary of the spinal canal is reached or the neural structures can be identified. Experience has shown that it is not possible to define clear guidelines; the precise procedure must be adapted to the findings in each case.

Complications

Possible complications during microsurgical procedures are known and have been described in numerous publications [2,21–23]. A minimally invasive procedure reduces the rate of complications [1,2], but statistically, they cannot be completely prevented. Basically, all of the complications known for conventional procedures can occur.

With respect to the fully endoscopic procedure, it must be emphasized that a unilateral or bilateral switch to an open procedure may be necessary for therapy of a complication. In particular, endoscopic suture of a dural injury is not technically possible. With long operating times and in cases of unnoticed blockage of lavage fluid outflow, the consequences of increased pressure within the spinal canal and the connected and adjacent structures can theoretically not be completely ruled out as a risk. Long-lasting and uninterrupted excessive retraction of the neural structures toward medial with the operating sheath must be avoided or performed intermittently to avoid the risk of neurologic damage.

As with all new techniques, there is a higher risk of complications at first, especially during the surgeon’s “learning curve.”

Postprocedural management

The hospital stay required depends on the surgical intervention. Pure discectomies or simple decompressions are treated with brief hospitalization or, if patient care at home is adequate, on an outpatient basis. Mobilization is immediate, as soon as the narcotic effects have subsided. No operation-related pain medication is required. Except for patients with neurologic deficits, no rehabilitative measures are necessary. Isometric and coordinative exercises can be performed without supervision once they are learned. Wearing of a passive lumbar orthesis during the day is prescribed for about 6 weeks. The weight limits for lifting and carrying objects can be increased, depending on the pathology and subjective sense of well-being. Return of the patient to work and sports is possible after wound healing, with the same prerequisites. After more extensive operations, the postoperative treatment scheme is usually more restrictive and depends individually on the interventions performed.

Conclusion

The goal of operating on lumbar disc herniations or spinal canal stenosis is to provide sufficient decompression while minimize operation-induced traumatization and its later consequences. Results now available show that the fully endoscopic uniportal interlaminar operation achieves the goals of therapy for the indications cited.

Consistent reduction of leg pain, as one of the main therapeutic criteria, can be regarded as an indication of sufficient decompression under fluoroscopic guidance. The success rate for microscopically assisted operations is between 75% and 100% [9,24,25]. Operation times, tissue traumatization, and complications are minimized [2,22,23]. Corresponding to the published advantages of a minimally invasive intervertebral and epidural procedure [26–28], there is no progression of existing symptoms. According to today’s understanding, the possibility of reducing or eliminating ossary and ligamentary resection as well as the minimally traumatic extirpation of the intervertebral space serves to avoid operation-induced instabilities [27–31]. Operation-related rehabilitative measures are not necessary. There is a comparably high rate of return to patients’ professional and athletic activity levels [8], with no greater morbidity of concurrent problems [22,23].

The recurrence rate is comparable to that of conventional techniques [32,33]. Revisions can be performed with the same technique. The negative effects of total resection of a degenerated nucleus, of which the biomechanical value is questionable, have not yet been completely elucidated [28,34]. Minimization of the anular defect may have greater protective influence than nucleus preservation [34].

Epidural scarring, which must be expected in conventional techniques and may lead to clinical symptoms in up to 10% or more of cases, is less with this technique [14,18,19]. Repeated endoscopic or conventional interventions can be performed without difficulty, and no lengthening of operation time has been reported [35]. In addition, the epidural lubricating tissue is preserved. This preservation corresponds to descriptions of better results with reduced traumatization of the ligamentum flavum [36].

Total and safe resection of herniated discs and other pathologies within the spinal canal must be performed under fluoroscopic guidance. Within the fully endoscopic uniportal procedure, the transforaminal operation is rated less traumatizing than the interlaminar operation because of the less extensive bony and ligamentous resections required. At the same time, the transforaminal procedure does have clear technical limitations. Thus, interlaminar access is indicated for problems that are technically inoperable with a transforaminal procedure, with the appropriate criteria taken into account. Overall the surgical approach is determined by the anatomy and pathology. Newly developed endoscopes with a 4.2-mm work canal and corresponding instruments enable resections of hard tissue [10,11].

In summary, the available study results show the possibility of sufficient decompression equal to that of conventional procedures, which must be achieved as the minimum measure of a new procedure [4]. At the same time, the procedure has the advantages of a truly minimally invasive procedure. The technique described here offers a sufficient and safe alternative to open or microscope- or endoscope-assisted procedures (Figs. 27-22 and 27-24) that can be used to remove a herniated disc of any size. With the possibility of selecting an interlaminar or transforaminal, posterolateral to lateral procedure, pathologies outside and inside the lumbar spinal canal can be

Figure 27–22 There is no limitation from the size of the disc herniation.

Figure 27-24 There is a lavage fluid collection in the L5-S1 space 2 hours after full-endoscopic interlaminar discectomy.

Figure 27–23 With the new endoscopes and instruments such as the forceps shown here, it ispossible to achieve sufficient extirpation of the intervertebral space.

sufficiently operated with the fully endoscopic uniportal technique, with the appropriate criteria taken into account.

It must be emphasized that clear indications and thus also limits do exist for this procedure. Thus, open and maximally invasive procedures are needed today and will be in the future. The surgeon must master these procedures in order to deal with problems and complications of fully endoscopic interventions, which may occur as in any invasive procedure. The development of fully endoscopic techniques do not replace existing operative standards but rather are supplements and alternatives within the overall concept of spinal surgery.