*2.4.1. Pelvic incidence*

what he termed faulty postural types in children [13]. Roussouly in 2005 identified lordotic types, which will be discussed in further detail later in this chapter [14]. Mac-Thiong in 2010

Our evolution in understanding the relationship of the pelvis to the spine can be traced to the early 1960s. Joanne Bullock-Saxton, in her narrative review in 1988, citied work by Hollinshead in 1962 observing a relationship between the position of the pelvis and the amount of lumbar lordosis [16]. Indeed, others also discussed the interaction between pelvic obliquity or pelvic inclination and its role in determining the degree of lumbar lordosis. Additionally, the obliquity of the sacrum was determined to be related to the degree of lumbar lordosis [16]. During et al. explained the relationship between the position of the sacrum and the depth of lumbar lordosis as functional. The steeper the slope of the upper portion of the sacrum, the deeper the lumbar lordosis needs to be in order to maintain optimal position of the upper part of the

The advent of instrumentation with spinal fusion in the surgical management of scoliosis and spinal deformity has led to a greater push to understand sagittal alignment. Although early surgical instrumentation was effective in addressing the frontal plane aspect of the scoliotic alignment, follow-up revealed often deleterious effects on the sagittal plane [18]. Doherty, in 1973, described what was later coined by Moe and Denis as "flatback syndrome," characterized by a fixed forward inclination of the trunk due to the loss of normal lumbar lordosis [18]. The early instrumentation combined the use of a straight rod with distractive forces and, when intervention extended to lower lumbar levels, the combination of these forces led to a loss of lumbar lordosis [18]. Recognition of this postoperative outcome led to advancements in surgical technique, which is beyond the scope of this text, as well as the understanding of the need to not only preserve but also enhance lumbar lordosis in order to minimize the risk of postoperative flatback syndrome. The identification of pelvic incidence, a morphological parameter that describes the relationship of the sacrum to the femur, represented a turning point in the movement to better address the sagittal plane from an operative perspective [19]. These parameters and their clinical implications may also be useful, as we will see, for the physiotherapist working with the older adult with spine deformity, as it gives us parameters within which we can better prognosticate the type of client we may be able to work with successfully.

Assess a patient's sagittal alignment allows the practitioner to objectively understand its potential role in contributing to a patient's pain and dysfunction. In 2006, the Scoliosis Research Society published the first classification system to develop a common language around adult spinal deformity (ASD). This classification grew out of an understanding that the existing adolescent scoliosis classifications were not entirely applicable to the adult population when making clinical decisions around operative management. The most recent update on this classification emphasizes the importance the sagittal plane plays in maintaining healthy upright spinal postures. Their work is valuable for the conservative care practitioner to help make clinical predictions as to the contribution of alignment to pain in our patients with spinal

described six postural types [15].

116 Innovations in Spinal Deformities and Postural Disorders

body over the lower along the line of gravity [17].

**2.4. Measuring spinopelvic alignment**

deformity [20].

Pelvic incidence is an anatomical or morphological measurement that is unique to each individual and is independent to the spatial orientation of the pelvis (**Figure 1**). It is specific to each individual and remains constant throughout the life span. The steps in measuring PI are as follows: (1) Draw a line across S1 superior end plate. (2) Find the midpoint from #1 and draw a downward perpendicular line. (3) Draw a line from the center of the femoral head line to the center of the center sacrum line. Often in the presence of pelvic obliquity you will need to find the midpoint of both femoral heads. (4) The angle between these lines is the pelvic incidence.

**Figure 1.** Pelvic incidence measurement. (1) Draw a line across S1 superior end plate. (2) Find the midpoint from #1 and draw a downward perpendicular line. (3) Draw a line from the center of the femoral head line to the center of the center sacrum line.

#### *2.4.2. Lumbar lordosis*

Lumbar lordosis is measured by the angulation from the inferior angle of T12 and the superior end plate of S1 (**Figure 2**).
