Musculoskeletal System and Joints - MCG 4151 Fall 2024.pdf

Musculoskeletal System and Joints MCG 4151 Design of Artificial Joint Prostheses and Implants Fall 2024 Presented by Émélie Bowness Department of Mechanical Engineering Faculty of Engineering  The Skeletal System – Axial Skeleton...

Musculoskeletal System and Joints MCG 4151 Design of Artificial Joint Prostheses and Implants Fall 2024 Presented by Émélie Bowness Department of Mechanical Engineering Faculty of Engineering  The Skeletal System – Axial Skeleton Our Focus: Vertebral Column Thoracic Cage Dr. Marc Doumit 2  Vertebral Column Flexible curved structure containing 26 irregular bones (vertebrae) 7 cervical vertebrae, i.e., Vertebrae of the neck 12 thoracic vertebrae, i.e., Vertebrae of the thoracic cage 5 lumbar vertebrae, i.e., Vertebra of the lower back Sacrum, i.e., Bone inferior to the lumbar vertebrae Coccyx, i.e., Terminus of vertebral column Main functions of the vertebrae: Transfer the weight of the head, neck, and trunk to the lower limbs Provide a safe corridor for spinal nerves Dr. Marc Doumit 4  Vertebral Column – Humans vs. Giraffe Fun Fact creation.com Almost all mammals have 7 cervical vertebrae Regardless of body size Large variations in the size of cervical vertebrae 11” Dr. Marc Doumit 5  Vertebral Column - Curvatures Curvatures increase the resilience and flexibility of the spine. Two posteriorly concave curvatures Cervical and lumbar Secondary curves Two posteriorly convex curvatures Thoracic and sacral Primary curves Dr. Marc Doumit 6  Abnormal Spine Curvatures A. Scoliosis - an abnormal, lateral curvature, accompanied by twisting of the vertebral column B. Kyphosis - an excessive posterior curvature of the thoracic region C. Lordosis - an excessive anterior curvature of the lumbar region Dr. Marc Doumit 7  Vertebral Column Each vertebra is interconnected to another by ligaments and separated by the intervertebral disc. Ligaments Anterior and posterior longitudinal ligaments – From neck to sacrum Ligamentum flavum – Connects adjacent vertebrae – Short ligaments – Connect each vertebra to those above and below The intervertebral joint allows limited motions between the bones, but the combination of multiple intervertebral joints along the spine provides great flexibility Dr. Marc Doumit 8  Vertebral Column Intervertebral Discs This disk consists of a fibrocartilage structure. A healthy disc is analogous to an inflated tire. The outside is a set of concentric rings of collagen sheets called anulus fibrosis (“ring of fibres”) The center is filled with a highly viscous gel called nucleus pulposus (“pulp”) The nucleus pulposus gives the disk resiliency and acts as a shock absorber. Dr. Marc Doumit 9  Thoracic Cage Composed of: Thoracic vertebrae Sternum (Breastbone) Ribs and their costal cartilages Main functions: Protects vital organs of thoracic cavity Supports shoulder girdle and upper limbs Provides attachment sites for many muscles Dr. Marc Doumit 10  Thoracic Cage There are 12 pairs of ribs. All attach posteriorly to the thoracic vertebrae. True ribs (pairs 1–7) Attach directly to the sternum by individual costal cartilages False ribs (pairs 8–12) Pairs 8–10 are attached indirectly to sternum by joining costal cartilage of rib above Pairs 11–12 also called floating ribs (no attachment to sternum) Dr. Marc Doumit 11  The Skeletal System – Appendicular Skeleton Dr. Marc Doumit 12  Pectoral Girdle and Upper Limb Each arm articulates with the trunk at the pectoral girdle (i.e. shoulder girdle) which consists of two bones: Clavicle (“collar bone”) Scapula (“shoulder blade”) Attach the upper limbs to the axial skeleton and provide attachment sites for muscles that move the upper limbs. The scapula is supported and fixed by skeletal muscles and has no bone or ligament connection to the thoracic cage. The clavicle articulates with the manubrium of the sternum. Dr. Marc Doumit 14  Shoulder joint The shoulder joint is a loose and shallow type of joint (ball and socket). Great range of motion Great flexibility and precision in arms Frequently vulnerable dislocation Stability is sacrificed for greater freedom of movement. Dr. Marc Doumit 15  Bones of the Upper Limb The upper limb skeleton consists of: Upper arm Humerus – Longest bone of upper limb – Articulates superiorly with scapula – Articulates inferiorly with radius and ulna Forearm Radius – Medial bone in forearm – Forms the major portion of the elbow joint Ulna – Lateral bone in forearm Hand 8 carpal bones in the wrist 5 metacarpal bones in the palm 14 phalanges in the fingers Dr. Marc Doumit 16  Pelvic Girdle and Lower Limbs The lower limbs articulate with the axial skeleton at the trunk through the pelvic girdle. The pelvis is a composite structure: 2 hip bones (coxal bones) sacrum coccyx of the axial skeleton. Main functions of the pelvic girdle: Attach the lower limbs to the axial skeleton with strong ligaments Transmit weight of upper body to lower limbs Support pelvic organs Dr. Marc Doumit 17  Pelvis Comparison of the Male and Female Pelvis Dr. Marc Doumit 18  Acetabulum The acetabulum is found on the lateral surface of the hip bone: Articulates with the femur Consists of a concave smooth curved surface Grasps about half of the femoral head Surrounded by a fibrocartilaginous lip (i.e. acetabular labrum). Viscoelastically deforms when the joint is loaded An unloaded acetabulum has a smaller diameter than the femoral head. Dr. Marc Doumit 19  Acetabulum Anatomic Considerations A typical internal diameter of an acetabulum is approximately 5 cm. Center-edge angle Acetabulum coverage in frontal plane. Averages 35o to 40o Prevents dislocation (protective shelf) Smaller angle (more vertical) ↑ dislocation risk Acetabular anteversion angle Acetabulum coverage in transverse plane Average 20o > 20o ↑ anterior dislocation risk Dr. Marc Doumit 20  Bones of the Lower Limb The main function of the pelvic girdle and lower limbs is to carry and transfer the body weight to the ground The bones and muscles of the pelvic girdle and lower limb are larger and more robust than the pectoral girdle and upper limb. There are 3 segments of the lower limb Thigh: femur Shank: tibia and fibula Foot: tarsal bones (ankle), metatarsal bones (metatarsus), and phalanges (toes) Dr. Marc Doumit 21  Femur Largest and strongest bone in the body Articulates proximally with the acetabulum of the hip and distally with the tibia and patella The femoral head is a convex component that is connected by a ligament at the fovea The shaft of the femur is strong and curves along the longitudinal axis The lateral bow of the femur facilitates weight-bearing and balancing Dr. Marc Doumit 22  Femur Femoral Head is the convex component of the ball and socket configuration of the hip Thick articular cartilages cover the medial-center of the head Thin articular cartilage covers the periphery of the head Smaller loads are sustained by the periphery, and higher loads are sustained by the center/anterior of head Dr. Marc Doumit 23  Femur Anatomic Considerations The femoral neck joins the shaft at an angle of about 125° A smaller neck-to-shaft angle is a coxa vara A larger next-to-shaft angle is a coxa valga An abnormal angle disrupts the hip joint’s functioning Dr. Marc Doumit 24  Hip joint The hip joint is a multiaxial synovial ball-and-socket joint that permits relative motion between the femur and the hip bone. Articular cartilage – fibrous cartilage that covers the articular surface Fat pad – acts as a shock absorber – covers the central portion of the acetabulum Acetabular labrum – rim of fibrous cartilage – binds the acetabulum and increases its depth Synovial membrane – seals the synovial fluid between the bearing surfaces Articular capsule – extremely dense and strong which contributes to joint stability – encloses both the femoral head and neck Dr. Marc Doumit 25  Hip joint Reinforced by five ligaments: 4 extracapsular ligaments: Iliofemoral ligament Pubofemoral ligament Ischiofemoral ligament Ligamentum teres 1 intracapsular ligament: Transverse acetabular ligament Muscles associated with the hip joint are larger (compared to the shoulder joint) and are adopted for strength over precision. Dr. Marc Doumit 26  Hip joint These muscles fit into 3 categories: 1) anterior muscles iliopsoas group (psoas major and iliacus) primarily for hip flexion 2) medial muscles adductors (adductor longus, brevis, magnus, pectineus, and gracilis) primarily for thigh adduction 3) posterior muscles Gluteus maximus, hamstrings (biceps femoris, semitendinosus, and semimembranosus) primarily for hip extension Dr. Marc Doumit 26  Patella The patella is a sesamoid bone at the knee joint. Main functions: Protect knee joint Reinforce the quadriceps tendon Transmits the tensile force of the quadriceps muscle and tendon to the patellar ligament Increase the lever arm of the knee extension mechanism The posterior patellar surface presents two concave facets for articulation with the medial and lateral condyles of the femur. Dr. Marc Doumit 27  Shank The tibia is the medial leg bone Articulates with the femur Transfers the weight of the body that is received from the femur at the knee joint to the foot through the ankle joint The tibia is also parallel to a slender bone, the fibula Articulates with the tibia at the head of the fibula Excluded from the knee joint and does not transfer weight to the ankle and foot Site of muscle attachment Dr. Marc Doumit 28  Knee joint largest and most complex joint of body transfers substantial load allows an impressive relative motion between the femur and the tibia 3 joints surrounded by a single cavity: Femoropatellar joint: plane joint allows gliding motion during knee flexion Lateral and medial tibiofemoral joints: between the femoral condyles and the C-shaped lateral and medial menisci of the tibia allow flexion, extension, and some rotation when knee is partly flexed Dr. Marc Doumit 29  Knee joint Medial and lateral menisci Fibrous cartilage pads Act as cushions Conform to the shape of the articulating surfaces as the femoral and tibial surfaces’ position change Fat pads Provide padding around the joint Help reduce the friction The knee joint can achieve a locking position at full extension. This is achieved by an external rotation of the tibia (“screw home mechanism”). Dr. Marc Doumit 30  Knee joint 7 major ligaments stabilize the knee joint Extracapsular ligaments: Intracapsular ligaments: 1) Tibial collateral ligament 5) Anterior cruciate ligament (ACL) reinforces the medial surface of the knee joint 6) Posterior cruciate ligament (PCL) 2) Fibular collateral ligament reinforces the lateral surface of the knee joint 7) Patellar ligament 3,4) Two superficial popliteal ligaments provides support to the anterior surface of reinforce the back of the knee joint the knee joint Dr. Marc Doumit 31  Foot The foot supports the body weight and acts as a lever to propel the body forward during gait. The foot comprises: Tarsals Metatarsals Phalanges Talus transfers most of the weight from the tibia to the calcaneus Dr. Marc Doumit 32  Foot Arches of the foot are maintained by interlocking foot bones, ligaments, and tendons Arches allow the foot to bear weight Three arches: Lateral longitudinal Medial longitudinal Transverse Dr. Marc Doumit 33  Ankle joint The ankle joint (tibiotalar joint) is a hinge joint formed by the tibia, fibula and the talus. Motion: Dorsiflexion (ankle flexion) Plantar flexion (ankle extension) The primary weight-bearing surface is the distal surface of the tibia and the trochlea of the talus. Dr. Marc Doumit 34  Ankle joint The functioning of the tibiotalar joint depends on the medial and lateral stability of the joint. 2 joints provide this stability: Proximal tibiofibular joint Distal tibiofibular joint Dr. Marc Doumit 34  Ankle joint The ankle articular capsule extends over surfaces of the tibia, fibula, and talus. The anterior and posterior portions of the articular capsule are thin, but the lateral and medial surfaces are strong and reinforced by stout ligaments. Medial deltoid ligament 3 lateral ligaments Dr. Marc Doumit 35  References D.L. Bartel, D.T. Davy and T.M. Keaveney, Orthopaedic Biomechanics, Mechanics and Design in Musculoskeletal Systems, Prentice Hall, 2006. M. Nordin and V.H. Frankel, Basic Biomechanics of the Musculoskeletal System, 3rd edition, Lippincott Williams & Wilkins, 2001 J.D Humphrey and S.L. Delange, An Introduction to Biomechanics, Solids and Fluids, Analysis and Design, Springer- Verlag, 2004. Marieb, E., Hoehn, K., Human Anatomy & Physiology, 8th edition, Benjamin Cummings, 2010 Martini, Timmons, Tallitsch, Human Anatamy, 6th edition, Person Benjamin, 2009 Dr. Marc Doumit 36