**1. Introduction**

Spinal conditions are some of the most common health conditions affecting adults [1]. Many spinal conditions do not affect spinal alignment, whilst others induce spinal deformity. Adult spinal deformity (ASD) is an umbrella term for a complex spectrum of spinal conditions causing spinal deformity [2]. The most common causes of ASD are degenerative disease and idiopathic (**Figure 1**). Other causes of ASD include oncologic, traumatic, neuromuscular and iatrogenic. Whilst the exact incidence of ASD is unknown, the rate of ASD increases with age with a reported prevalence of 32% of patients aged over 50 years and 68% of patients aged over 70 years [3].

Despite this prevalence, many patients have mild deformities and little or no symptoms. Conversely some patients have marked spinal deformity with global spinal imbalance causing severe disability [4]. The predominant reason for this disability is that spinal imbalance prevents the normal economic resting posture of the spine, whereby the centre of gravity runs in close proximity to the spine and the head is centred over the hips. This therefore requires an increase in the physiological demands of the spine and peri-spinal musculature which subsequently causes pain, fatigue and disability. It is therefore perhaps unsurprising that the extent of spinal imbalance directly relates to the degree of disability [5–8].

It is now recognised that the consequences of an imbalanced spine on a patient's function and quality of life (QoL) can be devastating [3, 5, 6, 8, 9]. In fact, compared to all other common long-term disorders, such as arthritis, chronic lung disease, congestive heart failure, diabetes and ischaemic heart disease, ASD has the worst patient reported QoL [10] (**Figure 2**). Furthermore, because of its increasing

### **Figure 1.**

*Lateral (a) and postero-anterior (b) standing X-rays of a 70-year old male with adult spinal deformity predominantly affecting the sagittal plane. Note the compensatory mechanisms for his lack of lumbar lordosis, notably thoracic hypokyphosis and pelvic retroversion, which results in a typical flat-back deformity.*

### **Figure 2.**

*Lateral (a) and postero-anterior (b) standing X-rays of a 55-year old female previous athlete who is now house-bound due to severe axial pain caused by her degenerative thoraco-lumbar spine, causing severe local kyphosis. Note her attempted spinal compensation for the thoraco-lumbar kyphosis, notably pelvic retroversion, lower lumbar hyperlordosis, thoracic hypokyphosis and cervical hyperlordosis.*

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

incidence, driven by multiple factors, ASD is the highest ranked disorder in estimates of global disease burden [10].

In order to quantify the degree of disability and effect on a patient's well-being from ASD, multiple functional scores have been employed [11]. Some scores have been specifically developed to assess spinal conditions, whilst others have been developed for other conditions but offer a proxy for "well-being" in patients with ASD. The most useful parameters available to understand the effect of ASD on a patient's well-being are pain, function and QoL. Thus, scores assessing these factors are commonly used to report outcomes in patients with ASD.

In general, pain scores numerically rate a patient's degree of pain (numeric rating scale (NRS)) in specific anatomical locations through a visual analogue score (VAS). For ASD, pain is usually separated into back and leg pain. In contrast, functional outcome scores attempt to understand what specific functions or activities are inhibited by a condition. In ASD, the most commonly used functional outcome score is the Oswestry Disability Index (ODI) [12]. This score was initially described to evaluate low back pain in a general population rather than evaluate the functional outcome of patients with ASD [12]. However, it is now widely used to evaluate the functional deficits induced by ASD and the response to treatment.

The ODI is a questionnaire that evaluates activities of daily living (ADL) that offers a subjective score of the respondent's level of disability. This index specifically assesses pain, personal care, lifting, walking, sitting, standing, sleeping, sexual life, social life and travelling [12]. For each domain the total achievable score is 5, with zero being no disability and 5 being severe disability. The scores for each domain are then summed and an overall percentage of disability is calculated. Whilst the overall disability value is one of the most commonly reported values in the literature, within each domain of the ODI the degree of disability can be scored and used to determine the effect of ASD treatment on specific ADLs.

QoL scores attempt to quantify the global effect that a condition has on the patient's life. The two most commonly reported QoL scores in ASD are the Scoliosis Research Society 22 (SRS-22) and Short Form 36 (SF36). The SRS-22 is a composite questionnaire of 22 questions developed specifically to determine the pain, function, self-image, mental health, and satisfaction of patients with spinal deformity [13]. In contrast, the SF36, which comprises 36 questions, was not specifically developed for spinal conditions, but does determine a patient's physical function, pain, vitality, social function, emotional effect, mental health and general health [14].
