Hip Joint Kinematic Pathomechanics 2024 Lecture Notes PDF

Kinematic pathomechanics of Hip joint Dr. Menna Ali  The two innominate bones together form the bony pelvis.. The orientation of the acetabulum influences the mobility of the hip and the location of weight-bearing forces on the femoral head...

Kinematic pathomechanics of Hip joint Dr. Menna Ali  The two innominate bones together form the bony pelvis.. The orientation of the acetabulum influences the mobility of the hip and the location of weight-bearing forces on the femoral head Lat and inf Orientation of acetabulum  The deepest portion of the acetabulum, known as the floor, or acetabular fossa, is rough and nonarticular. The articular, or lunate, surface of the acetabulum consists of a horseshoe- shaped rim ringing the acetabular fossa on its anterior, superior, and posterior aspects Transverse ligament What is Wolff’s law? Variations in bony thickness reflect Wolff’s law Example, Weight bearing at the hip joint involves the thicker superior and peripheral aspects of the acetabulum, while the thin, central, deepest part of the socket is unsuited for weight bearing  Types of Trabeculae in the Hip Joint: Primary Compressive Trabeculae: These are found in the superior acetabulum and are oriented to handle compressive loads from the weight of the body. They form strong vertical or arc-like patterns, designed to bear significant stress during weight-bearing movements. Secondary Tensile Trabeculae: These trabeculae are located more inferiorly and laterally in the acetabulum. They help resist tensile (stretching) forces and support the joint during movements that involve twisting or rotation. The primary compressive trabeculae are crucial in this superior part of the acetabulum, providing structural support and durability to maintain the health of the hip joint during daily activities. What is the more well organize arrays of trabecular bone surrounding the acetabulum? why? Well-organized arrays of trabecular bone surrounding the acetabulum, but particularly superior to it, reinforce the weight- bearing capacity of the socket labrum A fibrocartilaginous ring, or labrum, deepens the acetabulum, which helps to stabilize the hip joint, increase contact area, and decrease joint stress Labral tears may not only contribute directly to joint pain but also may destabilize the joint and allow increased stress on the articular surfaces, eventually leading to degenerative joint changes The labrum of Acetabulum The acetabular labrum provides significant stability to the hip by “gripping” the femoral head and by deepening the volume of the socket by approximately 30%. The seal formed around the joint by the labrum helps maintain a negative intra-articular pressure, thereby creating a modest suction that resists distraction of the joint surfaces A malshaped, dysplastic acetabulum that does not adequately cover the femoral head may lead to chronic dislocation and increased stress, often leading to osteoarthritis. ACETABULAR LABRAL TEARS Athletes participating in sports such as soccer or golf are particularly susceptible to labral tears. However, clinical diagnosis is difficult. Suggestive findings include pain with active or passive hip flexion, medial rotation and adduction, and clicking in the hip with these motions Femur The femoral head is covered with articular cartilage throughout its surface, with the exception of a small pit (fovea of the head of the femur) on its posteromedial aspect where the ligamentum teres attaches. The articular cartilage of the femoral head is thickest centrally and thins at the periphery of the head The bones of the hip joint are generally congruent with each other, and the congruency is improved even more by the articular cartilage This congruency provides two important benefits. First, the congruency allows larger areas of the joint to articulate with one another throughout the natural ROM of the hip. This means that the loads sustained during weight bearing can be spread across larger surface areas thus reducing the stress (force/area) the joint must withstand. Additionally, the congruency facilitates stability of the joint throughout the ROM  An anterior view of the femur reveals that the femoral head faces medially and superiorly in the acetabulum In the frontal plane, the angle of inclination refers to the approximately 125° angle between the neck of the femur and the shaft of the femur. A transverse plane view demonstrates that the head of the femur projects anteriorly. The neck forms an angle of approximately 15° with the plane of the femoral condyles.  Femoral neck The femoral neck sustains large bending moments as well as tensile and compressive forces during weight bearing and is reinforced by thickened cortical bone and organized arrays of cancellous, or trabecular, bone The arrangement of cancellous bone in the femur also provides another graphic example of Wolff’s law  2- Angles within the hip joint:- 1- Angle of inclination of the femur (Neck shaft angle) Plane Frontal Between 2 1- Axis of femoral neck. lines 2- Axis of femoral shaft Value 125° (140°- 150°) in infants 120° in elderly (2) Function Allows more degree of freedom. Medio-lateral stability. Abnormal ↑↑ Coxa valga change ↓↓ Coxa vara  2- Angles within the hip joint:- (1) 2- Angle of femoral torsion (Anteversion angle of the (2) femur) Plane Transverse Between 2 lines 1- Axis of femoral neck. 2- Axis of femoral condyles. Value 10°-15° (40° in newborn) Function Antero-posterior stability. Abnormal change ↑↑ Toe in gait ↓↓ Toe out gait The compensation  2- Angles within the hip joint:- 3- Acetabular Center edge (Angle of Wiberg) (2) (1) Plane Frontal Between 2 lines 1- Line between lateral rim of acetabulum and center of femoral head. 2- Vertical line passing through femoral head center. Value 22°-42° Function Lateral and superior stability of the hip joint.  2- Angles within the hip joint:- 4- Acetabular anteversion angle Plane Transverse Between 2 lines 1- Line passing through anterior and (1) (2) posterior rims of the acetabulum. 2- From posterior rim straight forward line. Value 20° Function Anterior stability of the hip joint.  Structure of the hip joint 2- Capsule of the hip joint Hip joint capsule is strong, dense and shaped like cylindrical sleeve. Cover femoral neck and attached to acetabular periphery. The four sets of fibers in the hip joint capsule; 1- longitudinal fibers (superficial), 2- oblique fibers, 3- arcuate fibers 4- circular fibers. (deep) – zona orbicularis.  Hip Joint Stability The hip is stabilized by its bony configuration and then by its strong capsular and reinforcing ligaments. These ligaments consist of longitudinal and circumferential fibers criss-crossing one another when stretched, clamps down on the structures within. As the hip is extended, the fibers of the capsule clamp down on the bony contents within, firmly holding the femoral head in the acetabulum. In contrast, hip flexion slackens the joint capsule  The blood supply to synovial joints is generally provided by a network of blood vessels, or anastomoses, at the attachment of the capsule and bone. The primary blood supply to the femoral head and neck arises from The medial and lateral circumflex femoral arteries at the base of the femoral neck that then travel proximally within synovial folds of the capsule reflected onto the femoral neck. Thus most of the vessels supplying the head of the femur must travel the length of the femoral neck to reach the femoral head The iliofemoral ligament appears to be the strongest ligament of the hip joint, sustaining larger tensile forces before rupturing  ALIGNMENT OF THE ARTICULATING SURFACES In the normal erect posture, the acetabulum and femoral head are aligned so that the head of the femur is directed slightly anteriorly and superiorly in the acetabulum. This orientation exposes the anterior aspect of the femoral head, leaving a large articular surface available for movement toward flexion The orientation of the femur and acetabulum facilitates advancement of the thigh in front of the trunk (flexion), while limiting the potential for backward movement of the thigh beyond the trunk. Flexion and abduction of the hip move the femoral head toward the deepest part of the acetabulum.  HIP JOINT CONTRACTURES Inflammation of the hip can occur for many reasons, including rheumatoid arthritis and infection. Whatever the reason, joint inflammation produces pain by causing swelling that stretches the joint capsule. To relieve pain, the patient often assumes a position of hip flexion, thereby putting the joint capsule on slack and reducing the stretch that produces pain. Yet prolonged hip flexion, particularly in the presence of inflammation, can result in a hip flexion contracture. Flexion contractures at the hip are a common finding in patients with arthritis. Instructing patients to stretch regularly into hip extension through exercise or static positioning can help prevent hip flexion contractures.  TREATMENT OF DEVELOPMENTAL DISPLACEMENT OF THE HIP (DDH) At birth Acetabulum shallow If the hip joint has excessive laxity The femoral head can easily slide out, subluxate or dislocate Especially with extension Due to wrapping the infant with blanket which keep the leg in extension The goal of treatment in care of DDH is to position and maintain the femoral head deep in the acetabulum to allow the supporting structures to tighten and to promote normal growth of the femoral head and acetabulum. Splints or casts position the infant’s hips in hip flexion beyond 90° and some abduction to obtain maximum joint contact and a stable hip position  How can bony alignment of the femur and acetabulum affects the loads applied to the hip joint and the rest of the lower extremity? Femoral necks with a wider superior to inferior diameter are better able to withstand the bending moments sustained during weight bearing. Men have wider femoral necks than women, which may help explain why the incidence of femoral neck fractures is much higher in women Clinical note; Clinicians must appreciate the role of joint alignment on the mechanics and pathomechanics of joint function to intervene effectively in the treatment and prevention of joint injuries.  joint reaction force on the femur is more parallel to the This puts the femoral neck in coxa valga hip abductors at a With decreased mechanical moment arms, advantage and the hip abductor may actually muscles must reduce the generate larger force they are contractile forces required to to support the hip exert during joint, resulting in stance, thus increased joint reducing the reaction forces joint reaction force. The joint reaction force is displaced laterally in the acetabulum and is applied over a smaller joint surface, leading to increased joint stress. Clinical note for coxa vara and valga coxa valga deformities are likely to increase the risk of degenerative joint disease within the hip by increasing the joint reaction force as well as the stress sustained by the femoral head. In coxa vara, Orthopaedic surgeons use the positive effect of altering the femoral neck alignment and improving the mechanical advantage of the abductor muscles in surgical osteotomies to reduce the loads on the hip for treatment of osteoarthritis and aseptic necrosis coxa vara tends to increase the medial pull on the femur into the acetabulum, which may contribute to erosion of the acetabulum an increased advantage for the abductor muscles may be accompanied by fatigue in the antagonist muscles SLIPPED CAPITAL FEMORAL EPIPHYSIS: Mechanics of a slipped capital epiphysis. A. In the young child, the femur exhibits a coxa valga alignment normally, and the capital epiphysis is approximately perpendicular to the joint reaction force (F). B. As the child grows, the coxa valga decreases and the epiphysis is no longer perpendicular to the joint reaction force. In this case, the joint reaction force consists of both a compressive force (FC ) and a shear (FS ) force. Contribution of the Pelvis to Hip Motion closed kinematic chain Hip Motion in Activities of Daily Living Normal walking utilizes approximately 20–30º of flexion, reaching a maximum at about initial contact. Stair climbing utilizes more, approximately 45–65º and slightly less for stair descent. Rising from a chair typically requires more than 100º of hip flexion, usually less than the amount of flexion used when bending to tie a shoe or squatting to pick up something from the floor PRECAUTIONS AFTER TOTAL HIP REPLACEMENT Impingement typically occurs with excessive hip flexion, adduction, or medial rotation. Surgeons and therapists carefully instruct the THR patient to avoid these motions, specifically avoiding flexion beyond 90º and any hip adduction or medial rotation  Thank u