Hip - Anatomy and Biomechanics
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Hip Anatomy and Biomechanics
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Hip - Anatomy and Biomechanics
- 1. Hip Anatomy and Biomechanics Dr Asish Rajak Fellow Sports Medicine and Arthroplasty
- 2. Anatomy • true ball-and-socket joint
- 3. BONY ANATOMY
- 5. skeletally immature – Triradiate cartilage
- 7. Anteversion
- 8. Dorr’s Types
- 9. Trabecular pattern of Hip
- 11. LIGAMENTS AND CAPSULAR ANATOMY • Iliofemoral ligament • Pubofemoral ligament • Ischiofemoral ligament • Ligament of Teres • Zona orbicularis / Angular ligament
- 12. The iliofemoral ligament can be seen anterior to the hip in the form of an inverted ‘Y’ or a modified ‘Δ’.
- 16. MUSCULAR ANATOMY
- 19. • providing stability and motion for the hip • prevent undue bending stresses on the femur
- 21. Biomechanics
- 22. • Joint reaction force defined as force generated within a joint in response to forces acting on the joint.
- 23. Lever arms acting on hip joint. A, Moment produced by body weight applied at body’s center of gravity, X, acting on lever arm, B-X, must be counterbalanced by moment produced by abductors, A, acting on shorter lever arm, A-B. Lever arm A-B may be shorter than normal in arthritic hip
- 27. Use of cane in opposite hip
- 28. Single-leg stance with a 100 N load in the opposite hand
- 29. Safe zone of orientation of femoral and acetabular components
- 30. Johnston JD, Noble PC, Hurwitz DE, Andriacchi TP. Biomechanics of the hip. In: Callaghan J, Rosenberg AG, Rubas HE, Eds. The Adult Hip. Philidalphia: Lippincott Williams & Wilkins 1998; pp. 81-90.
- 32. Medialization of acetabulum shortens lever arm B-X, and use of high offset neck lengthens lever arm A-B.
- 33. Lateral and distal reattachment of osteotomized greater trochanter lengthens lever arm A-B further and tightens abductor musculature.
- 35. References • Campbell’s Textbook of Orthopedics -12th Edition • Basic biomechanics of the hip. David E Lunn,Anastasios Lampropoulos,Todd D Stewart • Anatomy & Biomechanics of the Hip Damien P. Byrne*, Kevin J. Mulhall and Joseph F. Baker The Open Sports Medicine Journal, 2010, 4, 51-57
- 36. Thank you
Notas do Editor
- - It meets the four characteristics of a synovial or diarthrodial joint: it has a joint cavity; joint surfaces are covered with articular cartilage; it has a synovial membrane producing synovial fluid, and; it is surrounded by a ligamentous capsule.
- labral tears are most likely to occur at the junction of labrum and articular cartilage - this area has been termed the ‘watershed region’. The labrum receives a vascular supply from the obturator and the superior and inferior gluteal arteries.
- In the skeletally immature these three bones are separated by the triradiate cartilage – fusion of this starts to occur around the age of 14 – 16 years and is complete usually by the age of 23. The cup-shaped acetabulum is formed by the innominate bone with contributions from the ilium (approximately 40% of the acetabulum), ischium (40%) and the pubis (20%).
- The head of the femur is attached to the femoral shaft by the femoral neck, which varies in length depending on body size. The neck-shaft angle is usually 125±5° in the normal adult, with coxa valga being the condition when this value exceeds 130° and coxa vara when the inclination is less than 120° .
- The angle of anteversion is measured as the angle between a mediolateral line through the knee and a line through the femoral head and shaft. The average range for femoral anteversion is from 15 to 20°.
- Radiographic categorization of proximal femurs according to shape; correlation with cortical thickness and canal dimension . - Type A femurs have thick cortices on the anteroposterior view and a large posterior cortex seen on the lateral view. The narrow distal canal gives the proximal femur a pronounced funnel shape or “champagne flute” appearance. The type A femur is more commonly found in men and younger patients and permits good fixation of either cemented or cementless stems. Type B femurs exhibit bone loss from the medial and posterior cortices, resulting in increased width of the intramedullary canal. The shape of the femur is not compromised, and implant fixation is not a problem. Type C femurs have lost much of the medial and posterior cortex. The intramedullary canal diameter is very wide, particularly on the lateral radiograph. The “stovepipe”-shaped type C bone is typically found in older postmenopausal women and creates a less favorable environment for implant fixation .
- Singh index grade 1: only thin principal compression trabeculae visible grade 2: principle compression trabeculae present, other trabeculae nearly resorbed grade 3: principle tensile trabeculae thinned and breakage in continuity present grade 4: principal tensile trabeculae thinned without loss of continuity grade 5: principle tensile and compression trabeculae readily visible with prominence of Ward triangle grade 6: all trabeculae visible and of normal thickness Grade 3 and below indicate definite osteoporosis.
- - The extracapsular ligaments comprise the iliofemoral (IF) pubofemoral (PF) and ischiofemoral (ISF) ligaments. The iliofemoral ligament is a Yshaped ligament which extends anteriorly from the ilium, attaching to the intertrochanteric line of the femur; the IF ligament prevents hyperextension of the hip. The PF ligament attaches to the obturator crest and superior ramus of the pubis and blends with the articular capsule; the PF ligament prevents excessive abduction and extension of the hip. The ISF ligament is located on the posterior aspect of the hip, originating from the ischium and inserting on the intertrochanteric line of the femur; the ISF ligament resists hip hyperextension and excessive internal rotation.
- strongest ligament in the body While the ligamentous capsule is very strong, two weak points can be noted - the first anteriorly between the iliofemoral and pubofemoral ligaments, and the second posteriorly between the iliofemoral and ischiofemoral ligaments. Although dislocation is rare in the native hip, with extreme external trauma the hip can dislocate through either of these weak points.
- - The anterior and posterior portions of the hip have separate innervations. Anteromedially the joint is supplied by articular braches of the obturator nerve. The anterior aspect is contributed to by branches of the femoral nerve. The posterior aspect is innervated laterally by branches off the superior gluteal nerve. Medially contributions come from articular branches from the nerves to quadratus femoris and also articular branches from the sciatic nerve.
- Three sources are noted: a small vessel found within the ligamentum teres (present in about 80% of the population), a supply from the medullary canal and an anastamosis of vessels creeping around the femoral neck. This later supply is perhaps the most important. - These vessels arise posteriorly, chiefly from the medial circumflex femoral artery that braches off the deep femoral artery. The lateral circumflex artery makes less of a contribution. - Bleeding can be encountered during the posterior approach to the hip when the rich vascular anastamosis at the lower border of quadratus femoris is encountered . This consists of the ascending branch of the first perforating artery, branches of the medial and lateral circumflex femoral arteries and the descending branch of the inferior gluteal artery.
- The 22 muscles acting on the hip joint not only contribute to stability but also provide the forces required for movement of the hip .
- An example is the Trendelenburg gait, noted by the pelvis sagging to the contra-lateral side secondary to weakness of the abductor muscle group on the weight-bearing side. This is countered by the individual shifting their centre of gravity towards the affected joint by leaning over. This tilting reduces the force required by the abductors.
- - The hip allows for a large ROM in all three planes allowing for 120 flexion/10 extension, 70 abduction/adduction and 50 rotation .
- The alignments of the anatomical and mechanical axes of the lower limbs. The anatomical axis of the femur is 6° valgus to its mechanical axis. The anatomical axis of the tibia is 2–3° varus to its mechanical axis, but the two tibial axes are considered to be identical for practical purposes, as the difference between them falls within the acceptable margin of error (<3°) in mechanical axis realignment during lower limb procedures, e.g. total knee replacement or deformity correction.
- - Joint reaction force defined as force generated within a joint in response to forces acting on the joint. In the hip, it is the result of the need to balance the moment arms of the body weight and abductor tension. It maintains a level pelvis. center of gravity of human is just anterior to S2
- Because the ratio of the length of the lever arm of the body weight to that of the abductor musculature is about 2.5 : 1, the force of the abductor muscles must approximate 2.5 times the body weight to maintain the pelvis level when standing on one leg.
- In a mathematical model, the joint reaction force was lower when the hip center was placed in the anatomical location compared with a superior and lateral or posterior position. Isolated superior displacement without lateralization produces relatively small increases in stresses in the periacetabular bone.
- Double-leg stance The force acting on the hip joint during double-leg stance can be estimated from the proportional distribution of body weight. The legs comprise about 1/3 total body weight (TBW), so the weight of the upper body supported by the hips is approximately 2/3 TBW. Therefore, during a simple double-leg stance, each hip is subjected to a compressive force of about 1/3 TBW
- The hip joint reaction force during single-leg stance. The joint reaction force is estimated to be about 1.5 TBW.
- Another strategy to reduce joint reaction force involves using a cane or walking stick in the opposite hand. The moment produced from both the cane and abductor muscles together produce a moment equal and opposite to that produced by the effective body weight . The two-dimensional static analysis indicates that the joint reaction force can be reduced by 50% (from 3 times body weight to 1.5 times body weight) when approximately 15% body weight is applied to the cane . The substantial reduction in the joint reaction force, predicted when a cane is used for support arises because the cane-ground reaction force acts at a much larger distance from the centre of the hip than the abductor muscles. Thus, even when a relatively small load is applied to the cane, the contribution it makes to the moment opposing body weight is large enough to significantly decrease the demand placed on the abductor muscles.
- Single-leg stance with a cane support in the opposite hand A cane support in the hand transmits force applied to it to the ground, and receives an equal and opposite ground reaction force, which it transmits back to the body. During a single-leg stance, when a cane is held in the opposite hand to the supporting hip, the class I lever system has an additional upwards-acting load, the ground reaction force, which has a longer lever arm than the supported upper body weight. This produces a moment in the same direction as the abductor muscles force. Therefore, the moments produced by abductor muscles force and ground reaction force both balance the moment produced by upper body weight, which reduces the force requirements of the abductor muscles. Therefore, the joint reaction force is reduced to about 1.3 x TBW during single-leg stance.
- Femoral offset is generally measured on a standard anterior/ posterior pelvis radiograph and is defined as the perpendicular distance from the femoral head centre of rotation to the long axis of the femur. This measurement should be accurately performed and varies according to the hip rotation . The acetabular offset is the horizontal distance from the centre of the femoral head to the midline of pubic symphysis. Some authors define acetabular offset as the distance from the centre of rotation of the femoral head to the inner wall of the quadrilateral plate also called true floor of the acetabulum. The global offset is the addition of the femoral and acetabular offsets, or by measuring CDE in Figure . Failure to accurately reconstruct the femoral and global offset may result in impingement, hip instability, polyethylene wear and trochanteric pain.
- The estimated load on the femoral head in the stance phase of gait is equal to the sum of the forces created by the abductors and the body weight and has been calculated to be three times the body weight; the load on the femoral head during straight-leg raising is estimated to be about the same.
- The lengths of the two lever arms can be surgically changed to make their ratio approach 1 : 1 (see Fig. 3-1). Theoretically, this reduces the total load on the hip by 30% .
- - Higher offset stems create a larger abductor moment arm and this may decrease the hip joint reaction force through a corresponding reduction in the abductor force. This may also be combined with the advantage of a decreased risk of impingement and the disadvantage of increased soft tissue tension, with the potential for trochanteric pain. - In contrast decreasing the femoral offset may lead to increased hip joint reaction forces, instability, abductor weakness and gluteus medius lurch .
- Historically there have been two popular preoperative methods for assessment of leg length, the Woolson, and Williamson techniques.
- - The Trendelenburg gait, named after Friedrich Trendelenburg, is an abnormal gait (as with walking) caused by weakness of the abductor muscles of the lower limb, gluteus medius and gluteus minimus. People with a lesion of superior gluteal nerve have weakness of abducting the thigh at the hip. This type of gait may also be seen in L5 radiculopathy and after poliomyelitis, but is then usually seen in combination with foot drop. During the stance phase, the weakened abductor muscles allow the pelvis to tilt down on the opposite side. To compensate, the trunk lurches to the weakened side to attempt to maintain a level pelvis throughout the gait cycle. The pelvis sags on the opposite side of the lesioned superior gluteal nerve.