Making adult spinal surgery safer: strategies and limitations

Jwalant S. Mehta

Consultant Spinal Surgeon, Birmingham

Spinal deformities in adults are more common than reported. Most patients can compensate for the spinal column malalignment and carry on with little or no functional disability. However, a longer lifespan and a desire to stay active can prompt some to seek medical attention. While a substantial number of adults with spinal deformities can be treated by non-operative methods, a small, though notable proportion will require surgery. The magnitude of the surgical intervention is based on the patients’ symptoms, functional demands, and expectations. The spectrum of the operations ranges from decompressions to long fusions into the pelvis with three column osteotomies with anterior surgery. This end of the spectrum of complex spinal column reconstructive surgery bears the maximum risk of complications and adverse events, some of which are potentially life changing.

Surgical re-alignment operations in adults pose unique challenges within healthcare. A successful outcome is borne out of a holistic assessment of the patients’ problems rather than the focus on the technical success of the surgical reconstruction. Although the technical aspects form the primary basis of discussion between the patients and the surgeon, an appraisal of the general health and functional disability are far more relevant in the surgeons’ decision to offer an operation.

Patients’ expectations and symptoms are central to the formulation of the individualised surgical plan. Pre-operative assessments are done by specialised spinal deformity anaesthetists who are well versed with high-risk patients. Although the surgical procedures may be within the abilities and the comfort zone of the surgeon, the risks of such procedures can be considerably high. Some reports mention that the risks can range from 20 to 80%. The complications are considered on the lines of the extent of morbidity as major or minor or based on the time of onset as during the operation, early (under 90 days) and late (over 90 days). A large proportion of the complications are systemic – ie, stroke, myocardial infection, wound problems, infections, thromboembolic disease, and, rarely, death. However, a proportion of the complications are linked to the actual operation and are mechanical in nature. These can occur because of sub-optimum bone health, technical issues with the screws and rods, or surgeon judgment error.

Bone health is frequently underestimated. A sedentary lifestyle with poor mobility, certain medications, and smoking contribute to osteoporosis. DEXA scanning (Dual Energy X-ray Absorptiometry) provides an objective measure of bone mineral density. Results of this scan guide the surgeon towards specific treatment to increase bone mass. This treatment may be initiated by the GP but may need specialist input. Delaying the operation to achieve this target is desirable because it prevents complications related to the implants and problems with fusion across the operated segments. This lack of fusion is called pseudarthrosis and commonly presents as broken rods, requiring further surgery. The rod fracture can present innocuously as pain, clicks in the back not previously noted, or a loss of posture.

Surgery for spinal problems in adults requires fusion of several levels, often with osteotomies to allow for the re-alignment and additional anterior surgery. If the implant placement is sub-optimum, it could result in a neurological injury requiring revision surgery. The use of imaging during the operation is critical. Most major spinal units in the UK use two-dimensional C-arm image intensifiers in the operating theatre. Newer three-dimensional imaging in the theatres allows for a safer surgery with earlier identification and rectification of mal-placed implants. However, this type of technology is expensive and not freely available. The other downside of this technology is the potential for exposing patients and healthcare personnel to higher levels of radiation. The use of navigation and robotics is being developed and is a work in progress in some centres.

Spinal cord injury is a potential life-changing complication of a major spinal re-alignment operation. This type of procedure necessitates the use of multi-modal spinal cord monitoring to reduce the risk of spinal cord injury during correction of the spinal curvature. It is a mandatory requirement for most complex spinal procedures.

Erect X-rays allow the surgeon to plan the optimum alignment of the spine and set the surgical goals. Much research has been done on what constitutes optimum alignment. Several objective measures involving the spine and the pelvis have been described. Several software applications allow measurements and surgical simulation to be made. Achieving the optimum goals with surgery improves quality of life. Recent studies have shown that alignment goals should be age matched. Although these may appear to under-correct the spinal alignment, studies have shown that this strategy results in fewer mechanical complications. One of the common problems closely linked to over-zealous surgical correction is a loss of alignment in the normal spine above the operated spine. This junctional problem can be avoided with a well-tempered surgical judgment. When it does occur, it can be disabling and requires more surgery to rectify the problem.

Figure 1- An example of the risk stratification for a patient with a list of medical conditions and for a defined operation. The output form details the individuals risk comparing to the average risk for different conditions. It also predicts the length of stay in the hospital, the possibility of requiring rehabilitation and the percent risk of morbidity and mortality.

A detailed assessment of medical co-morbidities and general health requires input from different medical sub-specialities. This effort is led by the specialised spinal deformity anaesthetist and the pre-operative assessment team. Investigations to assess the heart, lungs, liver, kidneys, and blood clotting profile help to create granularity, which in turn allows for a detailed risk assessment. The assessments should ideally be on the lines of physiological age rather than chronological age. Frailty is a medical condition that is characterised by strength, endurance, and physiological function that increases the individuals’ vulnerability for developing an increased dependency and/or death.

There are several indices reported to measure frailty, one of which is the ACS-NSQIP

(https://riskcalculator.facs.org/RiskCalculator/PatientInfo.jsp). (figure 1)

This type of objective assessment assists the anaesthetic and surgical teams to predict adverse events. The assessments are done on the basis of the planned operation. The risks for the patient will vary depending on the operation complexity. Consequently, reducing the complexity can improve the risk profile for the patient. This can help the surgeon discuss the risk-benefit equation and allow for realistic expectations from the operation. The surgical plan can be modified if the risks are perceived to be unacceptable.

A strategy from the car manufacturing industry has reduced the complication profile and improve surgical outcomes. The Toyota philosophy is based on lean methodology. It was developed by Taiichi Ohno, a Toyota engineer. It is based on his observation that a particular workflow that is variable, unpredictable, and ambiguous is inefficient. It is difficult to identify value from the waste within the workflow. If the workflow is standardised, the variables can be controlled and refined to improve efficiency. This concept when applied to surgery in adults allows the ‘workflow’ to be stream-lined as pre-operative, intra-operative, and post-operative.

This system has been refined by a team of spinal deformity surgeons led by Dr Rajiv Sethi from Virginia Mason in Seattle as the Seattle Spine Team Protocol (figure 2) They describe a three-pronged systematic approach to risk management that addresses the complication profile and makes the surgery safer. This includes a multidisciplinary pre-operative complex spine conference, a collaborative team approach, and a rigorous intra-operative monitoring protocol.

Figure 2: The schematic outline of the Seattle Spine Team Protocol

One of the important features of this protocol is the multidisciplinary team meeting, which provides an opportunity for the treating team of professionals to discuss the various nuances of the individual patient. This is invaluable in complex problems, from both the medical and surgical perspective. This concept is based on the understanding that increased sub-specialisation allows for a more in-depth involvement of different teams to identify, mitigate, and hence avoid complications. A dispassionate discussion is likely to provide a more balanced range of opinions than a surgeon working in isolation. This mechanism can be used in deciding whether to operate or not; deciding on alternatives to the operation; creating clarity around the technicalities of the operation; or planning the details of the operation. This equal voice inclusivity has been reported as producing fewer complications and improves patient outcomes.

A collaborative intra-operative surgical team focussed on increasing the efficiency and working as a dual Consultant surgical team and a specialised complex spinal surgical anaesthetic team. Rigorous intra- operative spinal cord and anaesthetic monitoring protocols that include blood conservation strategies and enhanced recovery protocols are in use in several units. The nature of the rehabilitation requirement can be planned well in advance. Hospital stay should be minimised, and early commencement of physiotherapy is encouraged. Recovery times vary according to the operations. However, a positive outlook by the patients and the healthcare teams should be encouraged.

These approaches have reduced but not eliminated risks and the high rate of complications, which is inherent to this surgical group. The risk of stroke, myocardial infarctions, wound infections, thromboembolic diseases, and rarely death can be stratified to allow for a better-informed patient when consenting to the operation. The presence of some conditions such as previous malignancies, chronic diseases, and blood disorders allows for more robust strategies to counter possible complications.

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