AMTA > Anatomical and Biochemical considerations related to assessment of Pelvic Dysfunction

Anatomical and Biochemical considerations related to assessment of Pelvic Dysfunction

Presented by Barbara Hungerford B. App Sci. Phys. MAPA., SMA
Director, Advanced Manual Therapy Associates P/L
To the Women's Health Group, Australian Physiotherapy Association, South Australian Branch, 2000

Introduction

The pelvis provides the bony link between the flexible spinal column and the lower limbs, producing a stable platform from which these levers can act. The pelvis function to transmit and absorb forces between the spine and lower limbs ( Vleeming et al,1995), as well as providing attachment sites for 35 separate muscles and protection for abdominal viscera. Approximately 60% of body weight is transferred onto the sacral base (S1) from the L5 vertebral body during stance. The joints of the pelvis, i.e. the pubic symphysis and the sacroiliac joints, must efficiently transmit these forces for normal function of the spine and lower limbs ( Snijders et al 1993). An understanding of the structure of these joints provides insight into their function, and possibilities for dysfunction.

Anantomy/Biomechanics

A. The Pubic Symphysis

The pubic symphysis is a planar cartilaginous joint interposed with a fibrocartilaginous disc. It is supported by the superior pubic, inferior (arcuate), and anterior ligaments. The pubic symphysis is considered to be the most stable joint in the pelvis, and moves in reaction to forces placed across the joint, rather than by direct muscle action. However, muscles attaching close to the pubic symphysis still have their affect on the joint and must be considered when there is injury in this region.

Superiorly, consider the attachment site of rectus abdominus from the pubic tubercle along the superior pubic ramus, pyramidalis' attachment close to the pubic tubercle, pectineus, and the conjoint tendon. Inferiorly, adductor longus originates from a flat tendon attaching to the pubic body, gracilis and adductor brevis originate from the inferior pubic body and inferior pubic ramus, and adductor magnus from the inferior pubic and ischeal ramus plus the ischeal tuberosity. It is interesting to note the fascial connections occurring between the adductors and contralateral abdominal muscles, and the resultant cross pattern of fascial support anterior to the pubic symphysis. Such fascial connections may assist transmission of forces across the joint.

The physiological movements of the pubic symphysis are :-

superior / inferior shear of the ramus. In double leg stance the pubic rami should be symmetrically aligned. With single- leg support, e.g. on the right, the left pubic symphysis will glide inferiorly a maximum of 1-3 mm.
anterior /posterior rotation of the pubic rami occurs as a response to innominate anterior and posterior rotation e.g. during walking. The range of rotational movement is small (0.5 - 2.5°) (Walheim & Selvik, 1984).

B. The Sacroiliac Joint

The sacroiliac joint (SIJ) is classified as a diarthrodial joint (synovial) surrounded anteriorly and posteriorly by a joint capsule with inner synovial membranes and hyaline cartilage on both joint surfaces. Only a superficial layer of hyaline cartilage covers the iliac surface, and its roughened surface is suggested to increase the friction coefficient of the joint thus increasing joint stability ( Bowen & Cassidy,1981). The SIJ is roughly L- shaped with a short superiorly orientated joint, arm and a longer A-P orientated arm, which intersect at approximately S2 level.

The shape of a joint will affect its form closure, weight transference, and mobility. Snijders et al (1993) described form closure as a stable situation with closely fitting joint surfaces, where no extra forces are required to maintain joint stability. As a planar joint the SIJ is well suited for its primary function of transference of weight between the spine and hips, however its orientation makes it susceptible to vertically orientated shearing forces. At birth the joint is planar, but in the second decade, as body weight increases, complimentary ridges and grooves develop within the bony and cartilaginous structure of both articular surfaces (Vleeming et al, 1990). This inter-digitation of surfaces increases the SIJ's form closure, and stability.. The wedge shape of the sacrum and angulation of the SIJ's also improve form closure.

Soft tissue structures surrounding the SIJ affect the joint's stability while also allowing small amounts of movement to occur. Consider the following ligaments :-

interosseous ligament and posterior SI ligament - lie directly posterior to the SIJ and form a strong link between the sacrum and ilium that limits nutation and inferior shear of the sacrum. Note the interosseous lig. has an elastin component which will allow for small degrees of movement.
long dorsal SI ligament - from PSIS to S2 & S3 sacral crests. This ligament limits sacral counternutation and is commonly a source of pain in patients with SIJ symptoms (Vleeming et al,1996 ).
3. sacrotuberous ligament - attaches from the ischeal tuberosity to the inferior lateral angle (ILA) of sacrum. The sacrotuberous ligament limits sacral nutation, and will be tensioned by hamstrings contraction or stretch due to fascial linkage between biceps femoris and the lateral portion of the sacrotuberous ligament (Saunders et al, 1997). The sacrotuberous ligament has also been shown to have fascial connections to the posterior layer of thoraco-lumbar fascia, gluteus maximus, and piriformis (Vleeming et al, 1995). Thus, with extension of the hip, or during single leg support, activity of the gluteals will increase sacrotuberous ligament tension which increases force closure of the SIJ. Sacrospinous ligament also limits sacral nutation, and has fascial links to thoraco-lumbar fascia and coccygeus muscle.

The posterior layer thoracolumbar fascia has been considered in relation to its affect on the lumbar spine but its ability to increase force closure of the SIJs was only recently described by Vleeming et al (1995). Fascial connections between gluteus maximus and contralateral lattisimus dorsi via the posterior layer of thoracolumbar fascia are directed at 90° to the joint surface and so increase force closure. Multifidus and erector spinae muscles may also affect SIJ force closure via T-L fascia. Connections with internal oblique and transversus abdominis, erector spinae, plus biceps femoris via sacrotuberous ligament, as previously mentioned, are also important. It is reasonable to postulate that weakness in gluteus maximus, the deepest layer of abdominals, multifidus, or lattisimus dorsi could decrease the effect of thoracolumbar fascia on maintaining SIJ force closure, and increase its susceptibility to injury.

Affects of Pelvic Dysfunction

Instability or dysfunction in the pelvic joints may occur due to articular and / or myofascial factors. Joint dysfunction with, or without pain, will rapidly produce a pattern of muscle inhibition in the gluteal muscles similar to that seen in vastus medialis obliquus with knee joint injuries (Hungerford et al, 2001). Altered muscle recruitment decreases the ability to sustain a muscle contraction and thus decreases effective joint stabilisation in a variety of postures. Decreased muscle strength and posture control inevitably transfers the stress to other structures and may produce compensatory myofascial tightness or instability at the sacroiliac joints, the hip, or the lumbar spine.

At the SIJ the ipsilateral gluteus maximus activity is altered with joint dysfunction, which may decrease tension on the thoracolumbar fascia and sacrotuberous ligament. Decreased gluteal function, especially in sports involving hip extension motion, e.g. running, will produce a change in function of the hamstrings, as they now must increase activation to extend the hip. Resultant change in activity of the hamstrings may increase the chance of repetitive strains, knee extension dysfunction etc. Concurrent weakness of gluteus medius produces compensation at the hip with increased activity of TFL and adductors to maintain lateral stability.

Increased tension on the hamstrings may also occur as a direct result of pelvic injury e.g. when the innominate is forced into an upslip or anteriorly rotated position. A chronic upslip will often present with tightness in quadratus lumborum, psoas major, and sacrotuberous ligament.

The connection between joint dysfunction and myofascial changes are prevalent in the pelvic region. It is the therapists role to accurately diagnose between joint, muscle, fascia, nerve, inflammation, or other sources of pain. The assessment tests revised today allow for pelvic function to be diagnosed or ruled out. If pelvic dysfunction is diagnosed, muscle energy techniques provide one method of correcting the dysfunction as well as providing information on the myofascial and neural components that must be addressed for complete recovery. Specific exercise prescription to improve strength, length and coordination of muscles of the pelvis, lumbar spine, and lower limbs is imperative for complete rehabilitation.

Pregnancy and the Pelvis

By the third month of pregnancy the level of relaxin in the mothers body is reaching its first peak. The combined effect of relaxin and progesterone will be to increase the ground substance in ligaments with receptor sites for relaxin. The pubic symphysis and ligaments at the SIJ will both be affected. The increased ground substance gives the ligaments more flexibility, and it is expected that more motion will be able to occur at both these joints. Relaxin levels drop after the 4th month and then reach a second peak prior to labour. The amount of change in joint motion during pregnancy is unknown, but irritation of joint structures has been reported. As the abdominal muscles lengthen around the growing child, their line of action and torque production changes, which combined with increased joint motion, may be the precursor to decreased pelvic stability. Clinically, trochanteric, or SIJ belts may be useful to augment force closure mechanisms at the SIJ and pubic symphysis (these may be purchased from your local physiotherapist).

It is not uncommon for mothers to experience pubic pain during pregnancy, especially during weight bearing activities. Once the head is engaged, and during labour, a 10mm diastisis of the pubic symphysis is not uncommon. However a diastisis of 3-4cm will tear pubic ligaments and rupture the anterior SI ligaments, plus increase strain onto sacrotuberous ligament. This will produce pelvic instability, and the possibilty of pelvic dysfunction.

During labour the pubic symphysis moves through extreme ranges of motion to assist the passage of the childs' head. Discussions with midwives has lead to agreement that, if possible, birthing positions should be symmetrical, and not restrict the normal excursion of the pelvic joints. Squatting, knealing on all 4's, or birthing chairs are good options.

References

Bowen V & Cassidy JD (1981). Macroscopic & microscopic anatomy of the sacroiliac joint from embryonic life until the eighth decade. Spine: 6(6), 620-628.
Hungerford B, Gilleard W, Hodges P. Evidence of altered lumbo-pelvic muscle recruitment in the presence of Failed Load Transfer through the Pelvis. Submitted 2001.
Lee D (1989). The Pelvic Girdle. Churchill Livingstone: Edingburgh.
Lee D (1995). Contemporary positions of the Sacroiliac joint. Proceedings 9th biennial Conference MPAA. Gold Coast, Qld, 74-83.
Mens J, Vleeming A, Snijders C, Stam H (1995). Active straight leg raise test: a clinical approach to the load transfer function of the pelvic girdle. Proceedings 2nd Interdisciplinary World Congress on Low Back Pain. San Diego. 205-220.
Saunders J, Garlick D, D'Mello A, Schneir R (1997). The orthogonal plane of the sacrotuberous ligament as visualised by MRI. Australian Conference of Science & Sports Med. Canberra. 292.
Schwarzer A, April C, Bogduk N (1995). The sacroiliac joint in chronic low back pain. Spine: 20. 31-37.
Snijders C, Vleeming A, Stoeckart R (1993). Transfer of lumbosacral load to iliac bones & legs. 1:Biomechanics of self-bracing of the SIJ's and its significance for treatment & exercise. Clinical Biomechanics: 8, 285-294.
Vleeming A, Stoeckart R, Volkers A, Snijders C (1990). Relation between form & function in the sacroiliac joint. Spine: 15(2), 130-135.
Vleeming A, Snijders C, Stoeckart R, Mens J (1995). A new light on low back pain. Proceedings 2nd World Congress on Low Back Pain. San Diego.149-168.
Vleeming A, Pool-Goudzwaard A, Hammudoghlu D, Stoeckart R, Snijders C, Mens J (1996). The function of the long dorsal sacroiliac ligament. Spine: 21(5), 556-562.
Vleeming A. (1998). Biomechanics of the sacroiliac joint. Lecture notes from 5th International APA Congress. Hobart.
Walheim G & Selvik M (1984). Mobility of the pubic symphysis. Clinical Orthop. & Related Research: 191, 129-135.