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Surgical Anatomy of the Hip

The hip joint plays a vital role in both static and dynamic actions of the lower limb. This extremely stable joint is subject to large forces both from loading weight and strong muscular contraction. Despite its stability it retains an extensive range of movement.

 

A number of aspects of the hip are important not only surgically but in clinical practice. The following outlines the main anatomy of the hip and surrounding structures and the implications some of this anatomy has in clinical practice.

 

Surface landmarks of the Hip

There are only a few landmarks present on the skin surface however they are useful when one is orientating themselves with the hip:

 

  • Fold of the Groin

-          Crosses the femoral head below the inguinal ligament

 

  • Posterior superior iliac spine

-          overlies the sacro-iliac joint

-          Located by the dimple in the skin of the lower back

 

  • Gluteal fold

-          Disappears on flexion of the hip

-          Crosses in a horizontal path over the oblique lower boarder of the gluteus maximus

-          At the level of the ischial tuberosity

-          Formed by attachment of the skin to the underlying deep fascia

-          Runs at right angles to the pull of the hamstrings

 

  • Tendon of adductor longus

-          Can be felt at the pubic crest

 

  • Femoral Artery

-          Pulse felt below the mid point of the inguinal ligament

-          Vessel situated directly anterior to the head of the femur

-          Separated from head of femur by the underlying joint capsule and iliopsoas

 

  • Iliac crest                                      
  • Anterior superior iliac spine
  • Greater trochanter of femur
  • Ischial tuberosity

 

Bones of the hip

  • The hip bone is formed by three fused bones, the Ilium, Ischium and Pubis
  • All three bones meet at the acetabulum
  • Ilium and ischium form around 40% of the acetabulum each
  • Pubis forms remaining 20%

 

Bones of the hip

Ilium 

–         Forms superior part of hip bone

–         Large fan-shaped bone

–         Extended superiorly to form the ala

–         Ala has medial pelvic surface and lateral gluteal surface

–         Gluteal surface is a point of attachment for may muscles that act on the hip

 

Ischium

–         Forms posterior-inferior part of hip bone

–         Inferior expansion forms the ischeal tuberosity

–         Posteriorly located ischeal spine separates the greater and lesser sciatic notches

–         Ischeal ramus projects anteriorly from the ischeal tuberosity

–         Ischeal ramus forms inferior boarder of obturator foramen

 

Pubis

–         Forms anterior part of hip bone

–         Flat body

–         Superior and inferior pubic rami form the respective boarders of the obturator foramen

–         Lateral aspect of superior boarder has the pubic tubercle 

 

Acetabulum

–         Has incomplete crescent shaped articular surface

–         Surface is deficient inferiorly

–         Area of deficiency spanned by the acetabular ligament

–         Central non-articular acetabular fossa contains a fat pad covered in synovial membrane

–         Lip of acetabulum surrounded by acetabular labrum

–         Labrum deepens the socket into which head of femur sits

 

The hip joint

  • Synovial ball and socket type
  • Head of femur articulates with the acetabulum
  • Fibrous capsule covers lateral aspect of head of femur and most of the femoral neck
  • Capsule extends to the intertrochanteric line anteriorly
  • Posteriorly capsule is deficient and lateral third of the neck is extracapsular
  • Capsule attaches to the hip bone supero-posteriorly at the margins of the acetabular labrum
  • Capsule attaches to the hip bone antero-inferiorly at the outer surface of the labrum and to the transverse ligament of the acetbulum
  • Iliofemoral, pubofemoral and ischiofemoral ligaments reinforce capsule
  • Full extension of the hip pulls the fibers of the capsule tight, impacting the femoral head into the acetabulum
  • Femoral aspect of joint capsule has extensions into the vascular foramina at the base of the femoral neck
  • These extensions are folded to form the retinacula of Weitbrecht which provide folds that allow passage of major blood vessels to the femoral head

 

Hip joint

Neurovascular supply of the hip

 

Vascular Supply

 

The head of the femur is commonly affected by vascular disorders. This is due partly to the intra-articular position of this structure. The nature of the femoral head results in it depending on retinacular blood supply. This supply is derived from anastomoses of some larger vessels supplying the hip. These larger vessels also supply the surrounding structures of the hip.

 

Inferior gluteal artery

  • Branch of anterior trunk of internal iliac artery
  • Supplies number of structures within the pelvis as well as a number of muscles in the

buttocks and posterior thigh including:

 

- Gluteus maximus

- Obturator internus

- The gamelli

- Quadratus femoris

- Upper hamstrings

 

  • Artery runs postero-laterally
  • Passes through the greater sciatic foramen below the piriformis before entering the   gluteal region
  • Descends at postero-medial aspect of sciatic nerve before reaching the proximal thigh

 

Femoral artery

  • Branches from the external iliac artery as it traverses the inguinal ligament
  • Femoral artery passes behind the inguinal ligament at the point halfway between the anterior superior iliac spine and pubic symphysis
  • Passes down the antero-medial aspect of the thigh
  • Terminates at the adductor hiatus becoming the popliteal artery
  • First part of the artery is enclosed in the femoral sheath
  • Posterior to the artery lie the tendons of:

-          Psoas major

-          Pectineus

-          Adductor Longus

-          Adductor Magnus

  •  Medial to the artery is the femoral vein
  •  Lateral to the artery is the femoral nerve
  •  Gives rise to a number of superficial branches:

 

  1. Superficial epigastric
  2. Superficial external iliac
  3. Superficial external pudendal
  4. Medial circumflex femoral

 

 

Profunda Femoris (Deep femoral) artery

  • Largest branch of femoral artery
  • Arises within the femoral triangle from the lateral aspect of the femoral artery about 3.5cm below the inguinal ligament
  • Initially runs lateral to the femoral artery
  • Later it sits posterior to the femoral artery
  • The part of the femoral artery after this bifurcation is known as the superficial femoral artery
  • May also give rise to the medial circumflex femoral artery, an important artery involved in supply to the femoral head

 

The trochanteric anastomosis of the hip joint is formed from a number of branches of the arteries above. It is this anastomosis that supplies the femoral head. The main vessels involved in this anastomosis are:

 

  • Ascending branches of medial circumflex femoral artery
  • Ascending branches of lateral circumflex femoral artery
  • Gluteal arteries
  • Obturator artery

 

This anastomosis supplies the retinacular vessels which in turn provide blood supply to the femoral head.

 

It is important to remember that in some cases blood supply to the femoral head may also persist via the artery of the round ligament of the femoral head, however, this is not sufficient to sustain the femoral head alone.

 

Nervous Supply

 

Femoral nerve

  • Arises from the posterior divisions of the ventral rami of the 2nd-4th lumbar nerves
  • Runs an infero-lateral course through the psoas major
  • Sits in the grove between the psoas major and iliacus muscles below the iliac crest
  • Passes posterior to the inguinal ligament
  • Is situated laterally to the femoral artery
  • Supplies all the muscles in the anterior compartment of the thigh
  • Articular branches supplying the hip joint arise from the nerve to the rectus femoris

 

Sciatic nerve

  • Formed from the ventral rami of L4-S3
  • Exits the pelvis via the greater sciatic foramen inferior to the piriformis
  • Descends between the greater trochanter of the femur and ischeal tuberosity
  • Initially runs infero-laterally behind the ischium and crosses the nerve to the quaudratus femoris
  • After this it lies deep to gluteus maximus
  • As it passes inferiorly it traverses obturator internus, the gamelli and the quadratus femoris muscles
  • Medial to the nerve are the posterior cutaneous nerve of the thigh and inferior gluteal artery
  • Enters the thigh at the lower boarder of the gluteus maximus
  • As it passes through the thigh it gives rise to nerves to the hamstring muscles
  • Bifurcates at the upper aspect of the popliteal fossa into the tibial and common peroneal nerves
  • Supplies a number of structures including:     
  1. Biceps femoris
  2. Semitendinosus
  3. Semimembranosus
  4. Ischeal head of adductor magnus
  5. Hip joint

     

    • During hip flexion the nerve is stretched over the posterior joint capsule
    • Is vulnerable to trauma in posterior dislocation of the hip

     

    Anterior neurovascular structures

    Relationship of the anterior retractor to the anterior neurovasculature of the hip

    Muscles of the hip

    Many muscles act upon the hip providing the wide range of movement at this joint. Table 1 summarizes some of the main muscles which act on the hip.

     

    Table 1

    Muscles acting on the hip

    Surgical approach to the hip

    All of the structures mentioned previously must be considered when carrying out a surgical approach to the hip. Certain structures hold greater importance in different approaches to the hip. Considering the structures that are encountered during different approaches helps visualize the relationship the various structures have to one another.

     

    Anterior approach

    The main muscles encountered in this approach include:

     

    Sartorius

    • Runs from lateral to medial across the anterior aspect of the thigh
    • Nerve supply from the femoral nerve enters the muscle on the medial aspect
    • Can be detached from its proximal insertion and retracted medially

       

      Rectus Femoris

        • Situated over the anterior aspect of the joint capsule
        • Nerve supply from the femoral nerve also enters the muscle medially
        • Can be detached from its proximal attachment and reflected distally and medially

         

         

        Iliopsoas

          • Traverses the pelvic brim across the antero-medial aspect of the hip
          • The femoral nerve, femoral artery and femoral vein sit on top of the iliopsoas
          • Nerve supply enters medially
          • Can be retracted medially from directly in front of the hip joint together with the adjacent nerve, artery and vein

           

          Therefore it is generally considered that the hip flexors and associated neurovasculature are retracted medially during the anterior hip approach.

           

           

          Structures encountered in the anterior approach

          Lateral approach

          The main muscles encountered in this approach are:

           

          1. Tensor muscle

          • Traverses the lateral aspect of the hip and thigh
          • Nerve supply from the superior gluteal nerve enters the muscle posteriorly just below the iliac crest
          • Can be split vertically along its middle and the two halves retracted anteriorly and posteriorly

           

          2. Gluteus medius and gluteus minimus

          • The anterior edge of these abductors runs transversly across the front of the hip
          • Nerve and blood supply enters the muscles from posteriorly and superiorly
          • Can be detached from their distal attachment at the greater trochanter and be retracted in a supero-posterior direction
          • The hip may also be approached without detachment of the abductors by using postural changes of the hip

           

          3. Vastus lateralis

          • Covers the lateral aspect of the femur up to a point just inferior to the greater trochanter
          • Nerve supply from the femoral nerve enters the muscle antero-medially
          • Can be reflected antero-medially
          • Can also be split and retracted antero-posteriorly

           

          Therefore in a lateral approach to the hip it is important to preserve the abductors. The neurovasculature in this area should be protected by antero-medial retraction. The sciatic nerve must also be considered and will be protected if retracted postero-medially.

           

           

          Structures encountered in lateral approach

          Posterior approach

          The main muscles encountered in this approach are:

           

          1. Gluteus maximus

          • Provides superficial cover to the posterior aspect of the hip
          • Nerve and blood supply enter medially from its undersurface
          • Can be split in line with its fibers

           

          2. External rotators

          • Lie across the posterior aspect of the hip
          • Are in close relation to the posterior capsule
          • Cut at their insertion into the femur and greater trochanter
          • Retracted posteriorly and medially i.e towards their nerve and blood supply

           

          During the posterior approach the sciatic nerve is vulnerable to injury thus must be considered throughout.

           

          Sciatic nerve

          • Resides in the layer of fat between gluteus maximus and the external rotators of the hip
          • After penetrating the gluteus maximus the nerve can be felt with the examining finger
          • Retract the nerve posteriorly and medially away from the hip joint
          • Retraction in this direction reduces stretching forces on the nerve
          • Flexing the knee and extending the hip also release stretching forces on the nerve

           

           

          Structures encountered in posterior approach

          References

          Harty M. Some aspects of the surgical anatomy of the hip. J Bone Joint Surg 1966; 48: 197-202.

           

          http://famona.sezampro.rs/medifiles/anatomy/sclinics/dimon.pdf.  Accessed 28/12/11.

           

          http://naplestotaljoint.com/presentations/applied-surgical-anatomy.pdf.  Accessed 28/12/11.

           

          http://en.wikipedia.org/wiki/Hip_bone.  Accessed 4/3/12

           

          http://www.healthandphysicaleducationteacher.com/health-guide/musculoskeletal-disorders/diseases-of-hip-joint.html/attachment/diseases-of-hip-joint-1.  Accessed 4/3/12

           

          http://evertsmith.com/treatment/surgical-approaches/.  Accessed 25/7/12

           

          http://www.healio.com/orthopedics/journals/ORTHO/%7BD3A42600-E669-4B56-BF2B-55BD533B2898%7D/Current-Overview-of-Neurovascular-Structures-in-Hip-Arthroplasty-Anatomy-Preop.  Accessed 25/7/12

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