Firstly, to reduce the extent of the surgical dissection such as the traditional “stripping” of the spine for posterior fusion in which erector spinae musculature is dissected off the vertebrae to be fused (Fig 1a), and, secondly, to reduce blood loss therefore reducing the physiological insult of the surgery and the length of recovery.
The reduced physiological insult of MISS has made surgical treatment suitable to some candidates not deemed fit for traditional open approaches.
Early development saw sequential muscle dilating probes used with tubular table-mounted retractors allowing access to many parts of typically the posterior spine throughout its length without substantial dissection. Using an operating microscope and typically custom-designed instrumentation to reduce visual obstruction, lumbar and cervical discectomy, lumbar central canal stenosis decompression procedures were offered, typically through a 16mm or 18mm diameter tube retractor.
Placing pedicle screw instrumentation into the spine was traditionally performed ‘open’. Techniques using cannulated equipment to deliver screws percutaneously (essentially using a Seldinger technique of wire placement into a pedicle and then placing a screw over that wire) began the treatment of some fractures and tumours with pure percutaneous rod and screw placement, and, along with the use of tubular retractors, began the development all MIS lumbar fusion techniques.
Over the past decade, many techniques have developed, some good, some bad. A method of fusing L5/S1 by making a small incision close to the anus, dissecting the pre-sacral fascia and reaming the disc through the sacral promontory has largely been abandoned due to unfavourable outcomes.
Techniques to instrument the anterior lumbar and thoracic spine, which are able to restore disc height and angle, maximise fusion potential, correct deformity and maximise load sharing across a large implant interface. These have proved very successful.
The discipline is a world of acronyms, but the XLIF, ATP, and OLIF (to name a few!) approaches have proven worthwhile and remain widely used. Such techniques allow the treatment of conditions such as adult degenerative deformities in a wider range of patients.
New areas of development currently led by South Korean and some US centres focus on the development of spinal endoscopy. Discectomy in the neck and low back, decompression surgeries and more are now routinely being performed. These procedures are entirely dependent on custom endoscopes, irrigation delivery systems and shavers but may offer the promise of “ambulatory spine surgery” (local anaesthetic and sedation only and same-day discharge possible).
There is a long learning curve requiring the surgeon to develop a completely new set of skills and so uptake is currently (rightly) limited.
The procedures are almost always highly technology dependent, so equipment costs are significant. Research on the “return on investment” of these procedures due to reduced morbidity and length of stay has shown benefit.
However, some of the studies have been equipment company funded with sponsored surgeons. Hence bias potential must be acknowledged. In keeping with the published international results, local experience is demonstrating a patient benefit with accelerated recoveries, reduced hospital length of stay and reduced post-operative analgesic requirements.
Complications on this learning curve, however, can be significant and dealing with relatively simple problems such as a dural tear through a tubular retractor becoming more difficult than in open surgery. Furthermore, surgeons having learned new skills must avoid the temptation to apply them to cases inappropriately.
In adult spinal deformity, for instance, the MISS techniques have limitations and often severe deformities require a traditional open surgical approach to perform necessary bony corrections.
With new medical technology being offered at an accelerating rate, we must not only fully assess the incremental improvement offered to patients, but also consider the limited health care budget.
MISS is currently delivering both cost effective improvements in patient outcomes and expanding our treatment abilities. The future challenge will be continuing to implement available advances to optimise outcomes while delivering maximum economic value for those funding it.
- MISS aims to reduce tissue damage and blood loss, thereby shortening recovery.
- It comprises a suite of techniques with technology dependent procedures and significant learning curves to address spinal pathology.
- Not all pathologies or patients are suitable for MISS techniques.
References available on request.
Questions? Contact the editor.
Author competing interests: None to disclose.
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