**2. Main body**

#### **2.1. Definition of posture**

Alignment and postural control have long been fundamental to the clinical decision-making process of the physiotherapist. The Guide to Physical Therapy Practice lists "Posture" as a key test and measure to be included in a physiotherapist's objective examination [4]. Indeed, there exists no universal definition of posture and within postural control, alignment [5]. However, health-care practitioners from various backgrounds make similar statements when describing posture. Basmajian in 1965 understood posture to be the "upright, well-balanced stance of the human subject in a 'normal' position" [6]. The Posture Committee of the American Academy of Orthopedic Surgeons (AAOS) defines posture as "the state of muscular and skeletal balance which protects the supporting structures of the body against injury or progressive deformity, irrespective of the attitude in which the structures are working or resting. Under such conditions, the muscles will function most efficiently and the optimum positions are afforded for the thoracic and abdominal organs" [7].

#### **2.2. Evolutionary perspective on upright posture**

In evolutionary terms, it is upright stance and the ability of humans to achieve bipedalism that differentiates humans from the majority of the animal world. This ability was made  possible by the evolution of the structure of the pelvis and lumbar spine as well as their muscular attachments.

**3.** Define key sagittal parameters.

114 Innovations in Spinal Deformities and Postural Disorders

(physiotherapists/orthotists).

radiograph with the presence of vertebral rotation [2].

sagittal relationships.

**1. Introduction**

in clinical practice.

**2. Main body**

**2.1. Definition of posture**

for the thoracic and abdominal organs" [7].

**2.2. Evolutionary perspective on upright posture**

**4.** Explain the correlations between the various parameters that are key in understanding the

**5.** Describe how spinal deformity may lead to compensatory changes in sagittal alignment. **6.** State implications in terms of assessment strategies for the conservative care practitioner

Spinal Deformity may be defined as an abnormality in alignment, formation, or curvature of one or more portions of the spine [1]. Spine deformities can occur in one or a combination of the axial, coronal, and sagittal planes. Scoliosis is a spinal deformity defined by the Scoliosis Research Society (SRS) as a lateral curve measuring 10° or more on an anterior-posterior

In recent years, attention to the role of sagittal plane alignment in the overall health and function of adults with spine deformity has increased [3]. The purpose of this chapter is to shed light on the body of literature surrounding sagittal alignment variations and hypothesize about clinical implications for the conservative care practitioner managing spinal deformity

Alignment and postural control have long been fundamental to the clinical decision-making process of the physiotherapist. The Guide to Physical Therapy Practice lists "Posture" as a key test and measure to be included in a physiotherapist's objective examination [4]. Indeed, there exists no universal definition of posture and within postural control, alignment [5]. However, health-care practitioners from various backgrounds make similar statements when describing posture. Basmajian in 1965 understood posture to be the "upright, well-balanced stance of the human subject in a 'normal' position" [6]. The Posture Committee of the American Academy of Orthopedic Surgeons (AAOS) defines posture as "the state of muscular and skeletal balance which protects the supporting structures of the body against injury or progressive deformity, irrespective of the attitude in which the structures are working or resting. Under such conditions, the muscles will function most efficiently and the optimum positions are afforded

In evolutionary terms, it is upright stance and the ability of humans to achieve bipedalism that differentiates humans from the majority of the animal world. This ability was made Several changes have been critical to this evaluation. First, the human lumbar spine is exceedingly longer and more mobile, which has allowed for lumbar lordosis (LL)/extension to align the trunk over the pelvis from a lateral view [8].

Second, the sacrum in humans is broader/wider. It contributes to the mobility of the lower lumbar segments to form lordosis, where the narrowness of the sacrum and length of the ilia in other primates "lock" the lower lumbar segments [9]. In addition to the sacrum being shorter in length and broader in width, the ilia are also broader in width and more flared anteriorly [9]. This adaptation brings the anterior gluteal muscles (gluteus medius and minimus) from their former roles as hip extensors and migrates them laterally and anteriorly to perform their current roles as hip abductors and stabilizers of the pelvis during the single limb stance phase of gait. In partnership with a longer femoral neck, the gluteals create a longer lever arm, allowing the hip abductors to function more effectively in stabilizing the pelvis during the stance phase of gait.

Other muscular changes include hypertrophy of the gluteus maximus in humans, particularly during running, where it serves to keep the trunk from falling forward during heel strike [9]. Additionally, the hamstrings, while they played a "power" function in quadrupedal locomotion, play more of a stabilizing/control role in human bipedal locomotion. Furthermore, humans have smaller erector spinae muscles most likely owing to the center of mass being at the second sacral vertebrae, which creates a shorter lever arm in which the erector spinae have to work [9]. Therefore, the muscles do not need to be under such constant activation.

A general understanding of the evolution of spinopelvic alignment and upright stance helps us understand how the loss of this congruent relationship is potentially problematic in individuals with spinal deformity.
