Hip Joint

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Hip Joint

• The connection between the lower extremity and
  the pelvic girdle, a strong, stable ball socket
  synovial joint. (oxymoron?)
• When standing the entire body weight is
  transmitted through the hips to the femoral head
  neck.

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Articular surfaces

• Femoral head- approximately 2/3rds of a sphere
  except for the pit of the fovea. The head is
  covered by articular cartilage, thicker over the
  weight nearing areas.
• Fovea
• Ligament of the head

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• Acetabulum the hollow cup for the femoral head
  located on the lateral aspect of the hip.
• Acetabular rim fibrocatrilagenous lip with an
  inferior defect in the rim segment (acetabular
  notch).
• Lunate surface of the acetabulum is the weight
  bearing surface covered by articular cartilage,
• Acetabular labrum a lip of fibrocatilage that
  increases the depth of the acetabulum, it allows
  the acetabulum to grip the femoral head beyond
  the equator.
• Transverse acetabular ligament bridges the
  acetabular notch

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• Acetabular fossa the non-articular part of the
  acetabulum formed by the ischium
• The articular surface of the acetabulum femoral
  head are most congruent when the hip is flexed at
  90, abducted 5 and laterally rotated 10. This
  is the quadruped position.

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Joint capsule

• Formed by a strong loose external fibrous layer
  and an internal synovial membrane.
• External fibrous layer
• Attaches proximally on the hip bone to the rim of
  the acetabulum transverse acetabular ligament.
• Distally attaches to the femoral neck only
  anteriorly at the intertrochanteric line the
  root of the greater trochanter, posteriorly the
  fibrous layer has an arched border that crosses
  the neck proximal to the intertrochanteric crest
  it is not attached to the neck.
• Posteriorly the synovial membrane extends beyond
  the free posterior margin of the joint capsule on
  the femoral neck, it forms a bursa for the
  obturator externus.

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• 4. Fibers of the fibrous layer take a spiral
  course from the hip bone to the intertrochanteric
  line.
• 5. Orbicular zone deep fibers present on the
  posterior capsule wind circularly around the
  femoral neck.
• 6. Thickened parts of the fibrous layer form
  ligaments which pass a spiral fashion from the
  pelvis to the femur.
• 7. Extension tightens the spiral ligaments
  fibers, constricts the capsule pulls the
  femoral head into the acetabulum. This limits
  extension to 10-20 beyond vertical. Flexion
  unwinds the ligaments allows increasing hip
  mobility

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Hip Joint Reinforcement

• Anteriorly superiorly Strengthened by a
  Y-shaped iliofemoral ligament, attaches from the
  AIIS rim anteriorly and intertrochanteric line
  distally, this is the strongest ligament in the
  body. The iliofemoral ligament specifically
  prevents hyperextension of the hip while
  standing.
• Anteriorly inferiorly The pubofemoral ligament
  arises from the obturator crest of the pubic bone
  passes laterally inferiorly to merge with the
  fibrous layer of the joint capsule. The ligament
  blends with the medial part of the iliofemoral
  ligament. It tightens during extension
  abduction of the hip, it prevents over abduction
  of the hip joint.
• Posteriorly The weak ischiofemoral ligament
  arises from the ischial part of the acetabular
  rim spirals superiolaterly to the neck of the
  femur, medial to the base of the greater
  trochanter.

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• Figure 5-52B depicts the location and strength of
  hip muscles and ligaments. The muscles and
  ligaments pull the femoral head medially into the
  acetabulum.
• Medial lateral rotators of the thigh function
  to pull the femoral head into the acetabulum.
• Medial flexors (located anteriorly) are weaker
  and have poor mechanical advantage but associated
  ligaments are stronger.
• Medial extensors (located posteriorly) are
  stronger with more mechanical advantage but
  associated ligaments are weaker.

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Synovial membrane of the Hip Joint

• The synovial membrane lines the fibrous joint
  capsule intercapsular bony surfaces not lined
  by articular cartilage.
• The membrane reflects proximally along the
  femoral neck
• Synovial folds (retincaula) reflect superiorly
  along the femoral neck as longitudinal bands.
  These contain subsynovial retinacular arteries
  (consist of medial and a few lateral circumflex
  artery branches) that supply the femoral head
  neck

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• Ligament of the head of the Femur A synovial
  fold conducting a vessel to the head of the
  femur, this forms a weak ligament. The artery is
  important developmentally but is unable to
  adequately supply the mature femoral head. The
  wide end attaches to the acetabular margins the
  transverse acetabular ligament. The narrow end
  attaches to the fovea for the ligament of the
  femoral head.
• A fat pad fills in the acetabular fossa not
  filled by the ligament of the head, the pad
  changes shape to accommodate head movements. The
  fat pad ligament of the head are covered by a
  synovial membrane.

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• The synovial membrane protrudes beyond the free
  margin of the joint capsule on the posterior
  aspect of the femoral neck forms a bursa for
  the obturator externus muscle

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Hip Movements

• Flexion/extension at the hip depends on knee
  position, knee flexion releases the hamstring and
  thigh flexion increases until it reaches the
  anterior abdominal wall.
• Extension The fibrous capsule of the joint
  especially the iliofemoral ligament is taut. Hip
  extension is limited by the iliofemoral ligament.
• Abduction is freer than adduction. It can reach
  60 with the thigh extended and increases when
  the thigh is flexed.
• Lateral rotation is more powerful than medial
  rotation

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Hip Movements

• Strongest flexor is the iliopsoas muscle
• Adduction flexion by the adductor magnus
  (adductor portion) brevis and longus, pectineus
  and gracillis
• Adduction extension by the hamstring part of
  the adductor magnus
• Abduction media rotation anterior portion of
  the gluteus medius minimus
• Primary extensor of the hip is the gluteus
  maximus particularly when extending the thigh
  from a flexed position, after the leg is straight
  the hamstrings become the primary extensors.

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Blood Supply to the Femoral head Neck

• Medial lateral circumflex arteries usually
  arise from the profunda femoris they may arise
  from the femoral artery
• The medial circumflex is usually the major
  supply it passes beneath the unattached
  posterior border of the joint capsule to supply
  the head neck via retinacular arteries.
• The artery to the femoral head is a branch of the
  obturator artery and travels to the head in the
  ligament of the head this is important
  developmentally but is inadequate to supply the
  mature head neck.

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Nerve Supply follows Hiltons Law

• Flexors are innervated by the femoral nerve and
  pass anteriorly to the hip joint and supply the
  anterior aspect of the hip joint.
• Lateral rotators pass inferiorly posteriorly to
  the joint, the obturator sends branches the
  inferior aspect and the nerve to the quadratus
  femoris supplies the posterior aspect of the
  joint.
• Adductors supplied by the superior gluteal nerve
  (glut. Medius minimis) pass superiorly to the
  joint so this area is supplied by the superior
  gluteal nerve

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Hip dislocations

• Dislocation of the femoral head is unusual due to
  the stability of the joint, this requires a
  significant force.
• This occurs most often when the hip is flexed and
  medially rotated the usual position of the lower
  limb when riding in an automobile. The dashboard
  compresses the knee which causes the femoral head
  to rupture through the weaker posterior margin of
  the joint capsule.
• Posterior dislocations are much more common than
  anterior dislocations. Given its proximity
  sciatic nerve injury is often associated with
  posterior dislocations.
• Anterior dislocation of the hip requires the
  application of force the hip in extension,
  abduction and lateral rotation (when catching a
  tip in snow skiing. Often these injuries are
  accompanied by fractures of the acetabular
  margins and disruption of the acetabular labrum.

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• The posteriorly dislocated hip is slightly flexed
  at the thigh knee with medial rotation.

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• Posterior hip dislocations are frequently
  accompanied by fractures of the acetabulum.

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• Although a true hip fracture involves the joint,
  the following four proximal femur fractures are
  commonly referred to as 'hip fractures'. The
  differences between them are important because
  each is treated differently.
• Femoral head fracture denotes a fracture
  involving the femoral head. This is usually the
  result of high energy trauma and a dislocation of
  the hip joint often accompanies this fracture.
• Femoral neck fracture (sometimes Neck of Femur
  (NOF), subcapital, or intracapsular fracture)
  denotes a fracture adjacent to the femoral head
  in the neck between the head and the greater
  trochanter. These fractures have a propensity to
  damage the blood supply to the femoral head,
  potentially causing avascular necrosis.
• Intertrochanteric fracture denotes a break in
  which the fracture line is between the greater
  and lesser trochanter on the intertrochanteric
  line. It is the most common type of 'hip
  fracture' and prognosis for bony healing is
  generally good if the patient is otherwise
  healthy.
• Subtrochanteric fracture actually involves the
  shaft of the femur immediately below the lesser
  trochanter and may extend down the shaft of the
  femur

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Acetabular Fractures
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hip replacement