Fully endoscopic operations on the spine
In cases of spinal disc herniation and spinal canal stenosis, fully endoscopic techniques offer a safe alternative to conventional procedures says Sebastian Ruetten.
If conservative methods fail in the therapy of spinal disc herniations and spinal canal stenosis, conditions involving exacerbated pain or neurological deficits may require an operation to be performed. Despite good results from conventional operations, trauma may cause consecutive problems to occur. It is therefore important to continue to optimise these procedures, with the overall aim of minimising the trauma induced by the operation and negative long-term effects, while observing existing quality standards. Current research results and technical innovations must be assessed critically to permit the best treatment strategies.
Minimally invasive techniques allow tissue damage and its consequences to be reduced. Endoscopic operations under continuous fluid flow have become standard in many areas. The most common fully endoscopic procedure in the region of the lumbar spine has been the transforaminal or extraforaminal operation with posterolateral access and a primarily intradiscal or foraminal working area, but this operation can give rise to problems relating to pathologies within the spinal canal. The development of the lateral transforaminal approach (Figure 1) permits sufficient access to the spinal canal with direct and continuous visualisation; however, the diameter of the foramen, the pedicle and the exiting nerve may restrict mobility and hence indications. Furthermore, the pelvis may prevent access at the lower levels. The full-endoscopic interlaminar approach was therefore developed to permit surgery to be performed on pathologies that are inoperable transforaminally from a technical perspective (Figures 2 and 3).
The transforaminal approach also has more restrictions compared with the interlaminar approach, while at the same time exerting the least damaging effect on tissue. The anatomical and pathological requirements mean that the percentage relationship between the lateral transforaminal approach and the interlaminar approach are in the order of approximately 30 to 70. The posterolateral transforaminal passage is only used for the intradiscal approach.
Technical problems due to the small endoscopes and instruments were solved by newly developed rod-lens endoscopes with a large intraendoscopic working channel and specific new instruments, shavers and burrs. This permits resection of bones as in arthroscopic surgery.
In the area of the lumbar spine, the available study results – based on evidence-based medicine (EBM) criteria – show that in the case of spinal disc herniations and spinal canal stenosis, taking indication criteria into account, a fully endoscopic approach equivalent to conventional operations in vision is permitted.
A fully endoscopic approach also demonstrates the following advantages:
- relief of stress for the surgeon due to excellent visibility, good illumination and expanded field of view with 25° endoscope;
- cost-effective procedure with short operating times, fast rehabilitation and low post-operative follow-up costs, as well as reduced surgical trauma;
- easier revisions; and
- images can be monitored as the basis of training for assistants.There are a number of factors, however, that should be assessed as disadvantageous. These include:
- restricted options for expanding the operation if unforeseen difficulties occur;
- the theoretical risk of injury to the exiting nerves and restricted indications for transforaminal access; and
- the process entails a demanding learning curve.
In the area of the cervical spine, soft spinal disc herniations with radicular symptoms can be operated ventrally or dorsally using the fully endoscopic approach. The ventral approach may be restricted by anatomical requirements, while lateral pathologies provide an indication for the dorsal passage. Both procedures have specific advantages and disadvantages, although more than 95 per cent of the designated cases can be operated using the dorsal approach and this is therefore the technique of first choice (Figures 4 and 5). Thoracic interventions with transforaminal or interlaminar passage are technically possible but are only used for lateral spinal disc herniations with radicular symptoms resistant to therapy, and this means they are therefore seldom used overall.
Fully endoscopic techniques are adequate, safe supplements and alternatives as standard approaches to conventional procedures within the overall spectrum of spinal surgery. Open and maximally invasive operations are necessary today and will remain so in the future. Surgeons must be able to perform such operations, not simply so that they are in a position to offer patients the most appropriate procedure for their particular circumstances but also to enable them to deal safely with any problems and complications that emerge.
Sebastian Ruetten is head of spine surgery and pain at St Anna Hospital in Herne, Germany.