Download Gluteal Region, Posterior Thigh and Popliteal Fossa

GLUTEAL REGION, POSTERIOR THIGH AND POPLITEAL FOSSA Dr. Milton M. Sholley GLUTEAL REGION SELF­STUDY RESOURCES Essential Clinical Anatomy 3 rd ed. (ECA): 340­355 Grant's Atlas: 11 th Edition pp. 366­375 OR 12 th Edition pp. 384­393 Head to Toe Questions in Gross Anatomy: Finish questions #254­289; begin #542­606 OBJECTIVES The objectives of the first half of this lecture are to present the anatomy of the gluteal region, emphasizing muscle action and important neurovascular relationships. LECTURE OUTLINE I. Gluteal region A. B. Bony landmarks that are readily palpable 1. Iliac crest 2. Anterior superior iliac spine 3. Posterior superior iliac spine 4. Ischial tuberosity 5. Greater trochanter of femur Gluteus maximus muscle (see muscle chart) 1. Innervation­inferior gluteal nerve 2. Major origin­sacroiliac region 3. Insertions­iliotibial tract and gluteal tuberosity of femur 4. Actions­extension and external rotation at the hip. It is active when great extensor power is needed at the hip, as in lifting a load, rising from a chair, climbing stairs, or in gait at heel strike to prevent the trunk from pitching forward. (Ponder this: A person with weak gluteus maximus muscles will tend to stand with his/her hips in a position of hyperextension. Why?)
C. Gluteus medius and minimus muscles (gluteus medius/minimus muscle complex) 1. Innervation­superior gluteal nerve 2. Major origin­lateral aspect of ilium 3. Insertion­greater trochanter of femur 4. Actions­While they participate in rotation, particularly medial, and flexion­ extension, their major action is abduction at the hip. When standing on one foot, the gluteus medius/minimus complex of the supporting limb contracts to keep the pelvis from sagging to the opposite unsupported side. If the pelvis sags to the opposite side during standing on one foot, a TRENDELENBURG’S SIGN is said to be present. The Trendelenburg's Sign Is usually caused by paralysis or paresis of the gluteus medius/minimus muscle complex. Gluteus medius Gluteus minimus Lateral views of gluteal region­right side Fig. 1 D. Tensor fascia lata muscle 1. Innervation­superior gluteal nerve 2. Major origin­anterior superior iliac spine 3. Insertion­iliotibial tract 4. Action­weak flexor and medial rotator at the hip
E. F. Short rotator muscles­piriformis, obturator internus, superior and inferior gemelli, quadratus femoris 1. Innervation­by nerves named according to the muscles they supply 2. Action­all of the short rotator muscles are lateral rotators of the hip Neurovascular relationships 1. 2. G. After emerging from the greater sciatic foramen: a. The superior gluteal nerve and vessels run largely in the plane between the gluteus medius and minimus muscles. b. The inferior gluteal vessels and nerve run deep to the gluteus maximus. c. The nerves to the superior gemellus and obturator internus and to the inferior gemellus and quadratus femoris descend to their muscles. d. The sciatic nerve descends into the posterior thigh. e. The pudendal nerve and internal pudendal vessels exit the gluteal region by entering the lesser sciatic foramen, where they then run in the pudendal canal. Gluteal intramuscular injections should be given far away from the important neurovascular structures just mentioned. Hence, injections should be made in the upper outer quadrant of the gluteal region. The surface projection of the sciatic nerve in the gluteal region is along a curved line from midway between the posterior superior iliac spine and the ischial tuberosity to a point midway between the ischial tuberosity and the greater trochanter of the femur. Three bursae are associated with the gluteus maximus muscle (ECA, p. 343). A bursa is a closed sac lined with synovial membrane and containing fluid, usually found in an area subject to friction; e.g., where a tendon passes over a bone. A bursa normally plays an important role as as a lubricating mechanism, but can become inflamed, causing a painful condition known as bursitis. 1. The trochanteric bursa separates overlying muscle fibers of the gluteus maximus from the greater trochanter of the femur. 2. The ischial bursa separates overlying muscle fibers of the gluteus maximus from the ischial tuberosity. 3. The gluteofemoral bursa separates the iliotibial tract insertion of the gluteus maximus from the bony origin of the vastus lateralis muscle on the proximal femur.
Bursa ­ A closed sac lined with synovial membrane and containing fluid, usually found in an area subject to friction; e.g., where a tendon passes over a bone. Ischial bursa (Gluteus maximus slides over ischial tuberosity) Trochanteric bursa (Gluteus maximus slides over greater trochanter) Fig. 2 II. The Trendelenburg’s Sign and demonstration of the associated gait defect A. Explanation of the Trendelenburg’s Sign 1. When a person stands on one foot, the force of gravity tends to lower the opposite (i.e. unsupported) side of the pelvis. In a normal person, the gluteus medius/minimus muscle complex on the side of support reflexly contracts and therefore prevents the pelvis from dropping on the unsupported side. In fact, there may be an over­compensation, so that the pelvis actually elevates slightly on the unsupported side. We can say that the gluteus medius/minimus complex maintains the “lateral balance” of the pelvis during unilateral stance (i.e. standing on one foot). If you ask a patient to stand on one foot and observe that the lateral balance of the pelvis is maintained, then the Trendelenburg’s Sign is said to be negative. 2. The Trendelenburg’s Sign is positive when the pelvis tilts inferiorly (i.e. drops) on the opposite side of the body during unilateral stance.
3. B. III. The direct causes of a positive Trendelenburg’s Sign are usually paralysis or severe paresis (weakness) of the gluteus medius/minimus muscle complex on the side of the supporting foot. a. For our purposes, the simplest example of a circumstance that can cause a positive Trendelenburg’s Sign is a mechanical injury (e.g. knife wound) that severs the superior gluteal nerve. b. Injury to central pathways that control the superior gluteal nerve also can cause a positive Trendelenburg’s Sign. c. Muscular weakness due to intrinsic nerve diseases (e.g. multiple sclerosis) also can cause a positive Trendelenburg’s Sign (among many other signs and symptoms). d. Muscular weakness due to intrinsic muscular diseases (e.g. muscular dystrophy) also can cause a positive Trendelenburg’s Sign (among many other signs and symptoms). e. A positive Trendelenburg’s Sign less commonly may be caused by conditions not related to defects in activity of the gluteus medius/minimus complex, such as; (1) Dislocation of the hip joint (2) An abnormal angle of inclination between the neck and shaft of the femur Demonstration of the gait defect associated with the Trendelenburg’s Sign 1. During gait (i.e. walking), a person is supported on one foot, on both feet, and then on the other foot. Each gait cycle includes a stance period and a swing period. The foot in the stance period during one gait cycle will alternate to the swing period during the next gait cycle. 2. The paralysis or weakness of the gluteus medius/minimus complex that leads to a positive Trendelenburg’s Sign will also result in a dropping of the pelvis to the unsupported side during the stance period of each gait cycle. The pelvis will drop to the opposide side because that limb is off the ground and the pelvis is not being stabilized by the defective muscles on the side of support. 3. The gait defects characteristic of unilateral lesions as well as of bilateral lesions of the gluteus medius/minimus complex will be demonstrated during the lecture. Muscle Chart (charts are printed in syllabus) Gluteal Region
POSTERIOR THIGH AND POPLITEAL FOSSA SUGGESTED SELF­STUDY RESOURCES Essential Clinical Anatomy 3 rd ed. (ECA): 352­356 Grant's Atlas (11 th Edition): Figs 5.19, 5.22, 5.23B, 5.23C, 5.36 ­ 5.39, and 5.48 OR Grant's Atlas (12 th Edition): Figs 5.21, 5.24, 5.25B, 5.25C, 5.36 ­ 5.39, and 5.48 Head to Toe Questions in Gross Anatomy: Continue questions #542­606 OBJECTIVES The objectives of the second half of this lecture are: 1. 2. 3. 4. to present the anatomy of the posterior compartment of the thigh. to present the anatomy of the popliteal fossa. to present concepts of segmental motor innervation of the lower extremity. to present concepts of collateral circulation around the hip and knee joints. OUTLINE I. Posterior compartment of the thigh (hamstring muscle group) A. B. Innervation 1. The muscles of this compartment are innervated by the tibial of the sciatic nerve, except for the short head of the biceps femoris, which is innervated by the common peroneal portion of the sciatic nerve. (NOTE: Fibular is a synonym for peroneal.) 2. The hamstring (posterior) part of the adductor magnus is also innervated by the tibial portion of the sciatic nerve. Common origin 1. All of the hamstrings, including the hamstring part of the adductor magnus, have an origin from the ischial tuberosity, except for the short head of the biceps femoris. 2. The short head of the biceps femoris arises from the linea aspera of the femur; thus, this muscle has a different origin as well as a different innervation than the other muscles of the hamstring group.
C. D. E. II. Blood supply 1. Four perforating branches of the deep femoral (produnda femoris) artery and vein provide the major supply to the posterior compartment. 2. The superior end of the posterior compartment receives some supply from branches of the medial and lateral femoral circumflex vessels. Biceps femoris muscle 1. The long and short heads of the biceps femoris muscle join in the lower part of the thigh. 2. Both muscle heads have a common insertion on the head of the fibula. 3. The long head is primarily an extensor at the hip, but it also may adduct and laterally rotate the thigh. 4. By virtue of their common insertion, both long and short heads flex and laterally rotate at the knee. Semimembranosus and semitendinosus muscles 1. Semimembranosus inserts on the posteromedial aspect of the upper tibia. 2. Semitendinosus inserts on the anteromedial aspect of the upper tibia (its tendon is a component of the pes anserinus). 3. At the hip, both muscles are primarily extensors, but they may assist in adduction and medial rotation. 4. At the knee, both muscles are flexors and medial rotators. Popliteal fossa A. The popliteal fossa is bounded by the hamstring tendons above and the two heads of the gastrocnemius muscle below. Its floor is the posterior aspect of the lower femoral shaft, the posterior capsule of the knee joint, and the popliteus muscle. B. At the superior angle of the popliteal fossa the sciatic nerve usually splits into separate tibial and common peroneal branches. 1. The tibial nerve continues the course of the sciatic nerve down the midline of the popliteal fossa into the calf as the most superficial midline structure in the fossa. Deep to the tibial nerve is the popliteal vein, and deep to that, almost against the femur, is the popliteal artery. The adjacent location of bone and
artery deep within the popliteal fossa explains the occasional association of supracondylar femoral fractures and rupture of the popliteal artery. 2. III. Cutaneous nerves arising in the popliteal fossa A. Study the illustrations in Grant’s Atlas (11 th Edition) Figs. 5.3, 5.36B, and 5.37 OR in Grant’s Atlas (12 th Edition) Figs. 5.5, 5.36B, and 5.37 B. Note the skin areas innervated by and in the laboratory find the: 1. 2. 3. 4. IV. After becoming separate, the common peroneal nerve follows the biceps femoris tendon to its insertion and then spirals around the neck of the fibula within the substance of the peroneus longus muscle. In the muscle, the common peroneal nerve divides into its superficial and deep peroneal branches. Medial sural cutaneous nerve Lateral sural cutaneous nerve Peroneal communicating nerve Sural nerve Segmental motor innervation of lower extremity muscles A. Exact lists of spinal cord segments innervating each muscle need not be memorized, although this information can be important to diagnosis of neurological disorders. B. The scheme shown in the table below allows one to deduce the probable major spinal cord segments that innervate the muscles which cross each major joint of the lower extremity and produce the major movements, i.e. flexion or extension, at these joints. Major Segmental Innervation of Muscles Crossing Lower Extremity Joints Joint Muscles crossing joint Anteriorly Muscles crossing joint Posteriorly Action Segments Action Segments Hip: Flexion L2, L3 Extension L4, L5 Knee: Extension L3, L4 Flexion L5, S1 Ankle: Dorsiflexion L4, L5 Plantar flexion S1, S2
V. Concepts of collateral circulation across the hip and knee joints A. If the major arterial channel crossing a joint is occluded, blood supply to the tissues of the extremity distal to the blockage will depend on flow through the anastomoses of smaller collateral branches of the major arteries. 1. The collateral circulation across the hip joint is usually well­developed because there are numerous anastomosing arteries from several sources which can carry blood around blockages of the major arterial channel. 2. The collateral circulation across the knee joint is less well­developed because many of the anastomosing vessels (i.e. the genicular arteries) both originate and functionally connect to the same major artery (i.e. the popliteal artery). Total loss of blood flow across the knee will result in gangrene of the leg and foot. This is a serious complication that is often seen in patients with severe and long­standing diabetes. B. To understand arterial blood flow through collateral channels, realize that arteries have no valves and blood will flow in either direction depending on the location of the pressure head. C. Study the diagrams that follow and try to reason out whether and how blood could flow to the more distal parts of the lower extremity given occlusion of the major arteries in various locations.
Fig. 1
Fig. 2 VI. Muscle Chart (charts are printed in syllabus) Posterior Compartments of Thigh