By: 19 September 2018
Tackling the learning curve of MIS surgery

Dr Parajón and Prof Thomé, two key opinion leaders in the field of MIS surgery, provide an overview of the challenges and inefficiencies associated with current MIS procedures and the impact they can have on patients and hospital costs.


SSN: Tell us a little about your background and education within the spinal surgery industry?

CT: During my residency (1995-2001) I pursued a clinical and research focus on spinal surgery and MIS procedures, which was followed by my professorial thesis on these studies in 2004. After board certification I spent time as a spine fellow with Prof Harms at the Klinikum, Karlsbad-Langensteinbach (Karlsbad, Germany), with Dr Sonntag at the BNI (Phoenix, AZ/US) and at the Mayfield Clinic (Cincinnati, OH/US).

As Vice-Chairman of the Dept of Neurosurgery at the University Hospital Mannheim (Germany, 2005-2009) and as Chairman of the Dept of Neurosurgery at the Medical University Innsbruck (Austria, since 2010), I have been responsible for in-hospital spine surgery training. For more than 15 years I have been involved in educational activities of scientific societies, such as the German Society of Neurosurgery; German Spine Society; Spine Society of Europe; and the Austrian Spine Society, and currently serve as Education Officer Europe for AOSpine and as Chair-elect of the Training Committee of the European Association of Neurosurgical Societies. In parallel, I serve numerous educational commitments for various spinal surgery companies.

AP: I completed my neurosurgical residency in Madrid, at Hospital Universitario Puerta de Hierro, and a research fellowship on minimally invasive spine surgery in New York, under the direction of Roger Härtl at Weill Cornell. I attended many courses sponsored by different companies, and I have had the opportunity to visit surgeons across Europe to see and practice different approaches and techniques.

For many years I attended AO Courses, and since 2006 I have been involved in teaching as a faculty member, and have also chaired a number of AOSpine courses. I am part of the AOTK expert groups for the AOFoundation, including the Computer and Imaged Guided Expert Group and the Lumbar Degenerative Expert Group.


SSN: Could you explain more about your work in the field of MIS surgery for spinal fusions?

CT: Although my initial focus was on MIS decompressions and resections, my department now also focuses on MIS instruments. This encompasses percutaneous pedicle screw instrumentation, MIS TLIF, and cortical trajectories for pedicle screws which often are studied in prospective controlled trials.

AP: My main interest in MIS spinal fusion is MIS TLIF. Currently I am performing MIS TLIF fusion through the tubular approach, mainly with 3D navigation systems, based on CT and non-CT.

My main area of interest is spondylolisthesis and improving fusion rates. In this field, we published a paper in Neurosurgery in December 2017 (Minimally Invasive Transforaminal Lumbar Interbody Fusion: Meta-analysis of the Fusion Rates. What is the Optimal Graft Material? Parajón A, and others. Neurosurgery. 2017 Dec 1;81(6):958-971. doi: 10.1093/neuros/nyx141)

We also recently developed an app with Touch Surgery, to help surgeons learn how to perform a MIS TLIF fusion through a tubular approach. It was a really interesting way to learn and to lay out the steps of the surgical technique.

Another field of interest in MIS fusion is transpsoas interbody fusion (“XLIF”, LLIF, DLIF). We are performing this technique mainly as part of the surgical treatment of degenerative deformities and for adjacent level disease.


SSN: How does this type of surgery compare to more conventional open spine surgery?

CT: Open and MIS surgery mainly differ in the size of the approach. MIS uses transmuscular or muscle-sparing approaches, but attempts to achieve the same surgical goals. Blood loss, length of hospital stay and recovery can be reduced, and infectious complications are dramatically reduced. It is, however, often more difficult to achieve the same result, for instance in lumbar lordosis and deformity correction. In combination with less visual control this can require additional technical support such as navigation or specialised surgical instruments.

AP: As previously mentioned, there is an increasing amount of research showing that MIS surgery is superior (for certain types of approaches, such as MIS TLIF) to conventional open surgery in terms of recovery time, less blood loss, less hospital stay, and less money spent at a global level.

For years, the main criticism of MIS was the absence of scientific evidence, but this is changing.

A question that must be asked is: “What have we been measuring?”. In the long term, functional and radiological outcomes can be similar for open and MIS, but it is clear that MIS has a lot of immediate and short-term advantages for patients. And there are some other questions to be answered, such as if MIS has a reduced risk of complications, or if MIS requires less instruments.


SSN: How should surgeons decide which type of surgery to perform?

CT: This depends on the training and experience of the surgeon, the technical equipment available, the intended goals of surgery (for example, simple fixation versus deformity correction) plus individual patient characteristics. There is a learning curve with MIS that has to be respected.

AP: Ideally, the only criteria to make that decision should be what is better for a certain patient with a certain disease. In practical everyday situations, surgeons typically make the decision according to some other factors like the experience they have in a surgical technique, the availability of the tools needed for the procedure and, of course, the economic validity of the procedure.


SSN: How important is it that an experienced, well-trained surgeon undertakes the surgery?

CT: It is always important how well trained and experienced a surgeon is. A very experienced “open surgeon” who knows the general (critical) steps of a procedure well may get acquainted with MIS quickly, but is often reluctant to do so. Training is crucial to overcome these obstacles. Younger surgeons usually are more open-minded about novel techniques like MIS, but often require more technical support. I am personally convinced that training must involve a combination of basic principles (which do not differ between open and MIS surgery) and novel techniques. It is of utmost importance to follow a step-wise approach by starting with simple MIS procedures, mastering these and thereafter continuously increasing the difficulty of the procedures in a responsible manner.

AP: MIS surgeries are complex and require specific training. They also necessitate the use of tools and instruments that need further training.

There are some papers that have shown the impact of experience with these tools in reducing the rate of complications in MIS and the length of the surgery. Therefore, MIS surgeries must be performed or supervised by an experienced MIS surgeon. Training for MIS approaches is mandatory and one big disadvantage is that in the past those techniques were not included in the residency programmes of neurosurgery or orthopaedic surgeons. Surgeons then needed to attend courses (theoretical and practical) or participate in surgeon-to-surgeon programmes to upskill. Nowadays, MIS surgical techniques are becoming part of the programme in many University hospitals; practising with cadavers and simulators is an essential part of the learning experience.


SSN: What are the main challenges and inefficiencies associated with current MIS procedures?

CT: The main challenges are to tackle the learning curve, to integrate novel technologies like navigation in the set-up, and to achieve the same results as in open surgery. The OR team must be persuaded to follow this new path and the team members need to be coordinated. Moreover, MIS can be a financial burden as it may not be adequately reimbursed, further compounding the issues posed by the high prices of MIS implants.

Re-establishing lordosis and deformity correction can still be difficult and intraoperative radiation exposure in cases without spinal navigation is problematic.

AP: One of the main challenges in MIS is the heterogeneity in the surgical techniques. As many of them have been developed by implants companies, they have been built around particular types of retractors or implants and there is no general consensus around, for instance, how to perform MIS TLIF – it can be done with tubular retractor, blade retractor, Williams retractor, through a Wiltse paramedian approach, or through a transmultiphidus tubular secuential dilators approach.

The economic impact is something that hinders the implementation of MIS in many places, and the cost of new surgical instruments, implants, endoscopes, microscopes and robotic guidance devices is still high.


SSN: How can these be improved?

CT: Training of not only the surgeon but the whole team is crucial. Appropriate use of supporting technology like navigation, intraoperative imaging, and distractible devices needs to be implemented. MIS procedures need to be simplified to limit costs.

AP: The development of a MIS curriculum that outlines the surgical steps for main MIS approaches and techniques would help the expansion of those by making learning and feedback retrieval easier. It will also help in developing surgical implants and instruments for specific tasks.

The research on the economic aspects of MIS surgery, proving that MIS is cost effective, and the price reduction of implants and technology will definitely allow its implementation even in developing countries.


SSN: How do you think the future looks in the field of MIS procedures?

CT: I am convinced that MIS is the future of spinal surgery. New developments and supporting technologies will render these procedures more effective and more affordable. Training – particularly of young surgeons – will further increase its use.

It is crucial, however, that MIS is always done responsibly. Particularly for already small procedures, reducing the size of the approach by a few millimetres more will not make much of a difference, if at all. Currently, there are still procedures better suited for open surgery and there is also a reasonable limit to MIS.

AP: I believe MIS will eventually replace open surgery in most places for some pathologies and certain types of surgeries (one or two level lumbar stenosis, disc herniation, lumbar spondylolisthesis, lumbar adjacent level disease, cervical foraminal stenosis, thoracolumbar trauma, some oncologic patients), and hybrid surgeries will be the gold standard for complex problems like degenerative deformities.

The increasing affordability of the technology and the system of the procedures, as well as more scientific evidence, will help over the coming years to further advocate and spread MIS.

And of course, there will be a great increase in the use of navigation and robotics, as software becomes more user-friendly and systems are less bulky and more cost effective.



Dr Avelino Parajon: Head of Spine, Neurosurgical department, Hospital University Ramón y Cajal, Madrid; and Head of Neurosurgery, Hospital La Milagrosa.


Prof. Claudius Thomé, Education Officer Europe of AOSpine, Chair Elect of the Training Committee of the EANS, and President of the Austrian Society of Surgery.