**2. Discussion**

To date a complete understanding of which factors independently affect patient pain, function and QoL in patients with ASD remains unclear. In the general population affected by back pain a number of factors are reported to affect pain, function and QoL, with most factors contributing a variable amount to the disability. Because of this multi-factorial affect a biopsychosocial approach to understand the interconnected importance of each factor is appropriate. Biologically, the more sinister the cause and the more severe the condition, the more likely the patients are to be symptomatic. Similarly, the greater the spinal load, particularly increased body mass index (BMI), but also physical workload, as well as the more medical conditions affecting the patient the more likely they are to experience back pain [5, 15–17].

Psychologically, the psychological profile and capacity to cope influence the degree of back pain and dysfunction experienced by patients as does the patient's locus of control. A patient with an intrinsic locus of control (a patient who takes

personal responsibility for their own outcome) as opposed to a patient with an extrinsic locus of control (a patient who relies on others for their outcome) is likely to experience less pain and dysfunction. From a social perspective, those with a higher socio-economic status, greater supports, current employment and non-smokers experience less pain and disability. It is also known that other factors including geographic, and genetic factors influence back pain, function and QoL in the general population [18–22].

Similar to that of the general population, it is likely that multiple factors affect the pain, function and QoL of patients with ASD. However, only relatively few of these factors have been analysed in depth. The most well recognised correlation is that of sagittal imbalance. Sagittal balance can be described clinically as one's sagittal position of the skull relative to the hips, however, it is most accurately defined

### *The Functional Effects of Adult Spinal Deformity and the Effectiveness of Surgery DOI: http://dx.doi.org/10.5772/intechopen.90054*

radiologically as the sagittal vertical axis (SVA) which is the distance from the posterior superior aspect of the first sacral vertebral body to a line drawn perpendicular to the floor that runs through the middle of the C7 vertebra (C7 plumb line) in a standing patient (**Figure 3**).

Glassman and colleagues were the first to study this parameter and its effect on functional outcomes and found that an increase in sagittal balance directly affects functional outcomes in patients with ASD [5]. This finding has been confirmed in a number of subsequent publications [6–8].

Obesity has also been studied and shown to affect pain, function and QoL in patients with ASD. Intuitively an increased load on a compromised spine would affect a patient's well-being, however, the exact mechanism by which obesity affects these patients remains unproven. Furthermore, the effect of weight loss on the improvement of symptoms is yet to be determined. That said, the fact that obesity negatively affects the pain, function and QoL in these patients is of significant concern considering the rate of obesity is increasing internationally [23, 24].

Despite the paucity of data on other factors affecting the disability profile of patients with ASD, it is likely that there are multifactorial contributors that are yet to be studied. These include the patient's baseline requirements and ADLs, often driven by age, occupation and social activities; the patient's locus of control; the location and cause of the spinal deformity as well as the severity and number of levels affected; the degree of stiffness of the spine and hips and capacity to compensate for the deformity, the degree of coronal imbalance and global tilt. The contribution that each plays towards the patient's disability is likely varied, but on-going research into this area is warranted.

Similarly, the specific functional limitations induced by ASD have a likely multifactorial basis, which makes specific treatments for specific functional deficits limited. However, it is recognised that severe ASD can affect all ADL and severely affect QoL [3, 6, 8]. Since Glassman's correlation between the ODI and SVA, the use of health-related quality of life scores (HRQLs) to assess the success of treatments in ASD has become routine [5, 25]. Unfortunately, there is a lack of published material on the specific disabilities induced by ASD. In contrast, some information is available on the specific functional benefits of the treatment of ASD.

The treatment of ASD is challenging. To date, non-operative treatment, although used extensively, has not been shown to improve long term outcomes for these patients, especially when significant anatomical abnormality and spinal imbalance is present [26, 27]. However, core strengthening, aerobic exercise and weight loss strategies are useful in the treatment of LBP in the general population and are relatively cheap, easy, safe with patients gaining a degree of self-control over their condition and gaining multiple other health benefits of such lifestyle modifications. Pain management offers symptom control to alleviate pain which may improve function, but often at the effect of sedation. Furthermore, long-term symptom control is required with the development of medication tolerance and reliance, with the associated expense and complications of long-term medical treatment. Injection therapy with epidurals, nerve blocks and facet injections may offer some temporary benefit. Bracing may offer short term benefit but defunctions the paraspinal musculature which often worsens symptoms when the brace is removed. Glassman and colleagues analysed the non-operative resource utilisation and cost benefit of non-operative treatment in ASD. They identified a large resource utilisation and cost for patients with ASD, particularly those with severe symptoms, but no improvement in the health status at 2-year follow-ups with non-operative treatment [26, 27].

In contrast to non-operative care, operative intervention has shown long-term improvements in pain, function and QoL in symptomatic patients, and this has

fuelled the increased number of complex ASD surgeries being performed worldwide [2, 28–31]. In the last decade the number of complex operations being performed for ASD has doubled in many countries, including the USA and UK, which contrasts with the 20% increase in all other spinal surgeries [2, 29].

The surgery for this condition can vary from a single level neural decompression to global deformity correction. However, there is growing evidence that most patients with symptomatic ASD benefit from a restoration of their spinal balance [7, 32, 33]. But, procedures to restore spinal balance are far more complex than simple decompressive procedures. Furthermore, spinal realignment surgery is expensive with the demands of a single case and impact on health services being disproportionately greater than those of other elective procedures, such as total hip joint replacement [28, 30, 31]. The average total hospital cost for a primary procedure is estimated at US\$103,143, and therefore the improvement in pain, function and QoL needs to be justified [34].

Furthermore, despite the evidence that spino-pelvic fusion is associated with excellent patient satisfaction and improvements in overall function, patients increasingly require information on the specific functional benefits and limitations induced by ASD treatment in order to make informed decisions and avoid inaccurate patient expectations [14]. Kieser and colleagues reviewed the effect of primary spino-pelvic fusion on the specific functional outcomes of ASD in a retrospective review of 45 consecutive patients enrolled in the European Spine Study Group database with a minimum 2-year follow-up [35]. Their study confirms that spinopelvic fusion significantly improves the overall ODI score at a 2-year follow-up for patients with ASD. They identified a mean 13.5% overall improvement in disability, with a reduction in pain and improvement in function and QoL.

When assessing the effect of ASD surgery on specific ADLs, Kieser and colleagues reported a variable degree of benefit for each ODI domain. Large improvements were found for pain and sexual function, moderate improvements for walking, sitting, standing, social life and travelling and minimal improvements for sleeping, personal care and lifting [35]. No domains were found to worsen after surgery at a 2-year follow-up. These results suggest that the pain relief, spinal stability and balance offered by these procedures improve ADLs such as walking, sitting, standing, travelling, social life and sexual function. However, the rigidity imparted by the fusion limits the improvement in personal care and lifting, which often relies on spinal mobility.

Conceptually, long-segment fusions should worsen certain ADLs such as personal care. Yet the study by Kieser and colleagues revealed an improvement in these functions but commented that this improvement was not statistically or clinically significant [35]. They suggested that the pre-operative spinal mobility of patients with ASD is usually poor, either from stiffness or pain, and therefore fusion carries a less significant functional effect in this condition than in conditions with normal spinal mobility. In addition, the minimal improvement in sleep has been postulated to be due to the effect of gravity driving disability in the upright position being non-influential when lying down [35]. However, the study was limited by only assessing the ODI without including other outcome scores and by the variance in underlying cause, curve type, extent of deformity and preoperative symptoms of included patients.

Recognising that spino-pelvic fusion reduces the overall level of disability in patients with ASD allows the surgeon to advocate for such procedures, but understanding the large improvement in pain and sexual function, moderate improvement in walking, sitting, standing, social life and travelling and limited improvement in sleeping, personal care and lifting allows patients to make informed decisions with clear expectations, that empowers them to make the right personal decision.

### *The Functional Effects of Adult Spinal Deformity and the Effectiveness of Surgery DOI: http://dx.doi.org/10.5772/intechopen.90054*

Although the only study assessing the effect of ASD surgery on specific ADLs, the study by Kieser and colleagues only assessed primary procedures [35]. To date, no comparable study has been undertaken on revision procedures. However, Scheer and colleagues previously identified that patients requiring revision deformity correction have a worse longer-term outcome than those who do not require revision [36]. This is important to recognise because ASD surgery carries a high complication rate, with a reported major complication rate of 20% and 30-day mortality of 2.4% [25, 37]. Therefore, when contemplating the first procedure, despite the potential increased initial expense and risk involved in a comprehensive deformity correction, it is in a patient's and institution's best interests to optimise the first procedure, to optimise outcome and reduce the longer-term costs associated with revision surgery. An approach to "getting it right first time" is therefore warranted [38].
