Hip Flashcards
What are femur bony features?
- Head (convex). 2/3 of a sphere. Articular cartilage covering is thickest on medial central surface
- Neck (anatomical and surgical) - 135 degree to shaft. Angle of inclination (neck to shaft) and torsion angle (angle between axis through femoral head and axis through femoral condyles) are important
- Intertrochanteric line - continues as pectineal line posteriorly
- Intertrochanteric crest
- Greater trochanter - attachment for gluteus medius, gluteus minimum, piriformis, vastus lateralis
- Lesser trochanter - attachment to iliopsoas
- Fovea capitis (dimple on the head of femur) - attachment for ligamentum teres (2 bands that originate at ischial and pubic sides of acetabular notch). Provides stability to joint and prevents subluxation during flexion and abduction. Connection of femoral head to pelvis
What is the ligamentum teres?
- Intracapsular
- Serves as carrier for foveal artery which supplies femoral head in infant
- Injuries to the ligamentum teres can occur in dislocations which can cause lesions of foveal artery
What are pelvis bony features?
- Ilium
- Ischium
- pubis
- Ischial spine
- Ischial tuberosity
- Inferior pubic ramus
- Superior public ramus
- Pubic symphysis
- Obturator foreman
- Greater and lesser sciatic notch
- Greater and lesser foreman
- ASIS, AIIS
- PSIS (back dimples), PIIS
- Anterior gluteal line
- Posterior gluteal line
- Inferior gluteal line
- Articular cartilage covers the surface of the acetabulum and thickens laterally and peripherally
- Articulation only occurs on the horseshoe shaped articular cartilage located peripherally
- Acetabular labrum (a fibrocartilage lip that deepens acetabulum) blends with transverse acetabular ligament
-Transverse acetabular ligament spans acetabular notch to prevent inferior dislocation of femoral head
What is the hip joint?
- Ball and socket synovial joint
- Head of femur is 2/3 of a sphere
- Allows movement in triaxial joint (sagittal, frontal and transverse)
- Allows wide range of movement
- More stable than shoulder joint but reduced mobility. Reduced chances of dislocation
- Hip joint = socket is much deeper, and ligaments and muscles are bigger than in shoulder joint
- The socket (acetabulum) fully encompasses femoral head, making this joint stable, whereas humeral head is 4x larger than glenoid fossa
- The hip joint is controlled and protected by the acetabular labrum, the joint capsule and many powerful muscles
- Head of femur articulates with lunate surface of acetabulum. Covered by hyaline cartilage
What are the motions available?
-Transverse, sagittal and frontal
- Transverse= allow internal and external rotation
- Sagittal = allow flexion and extension
- Frontal = abduction and adduction
- Motion is greatest in the sagittal plane.
- Flexion = 0 to 140 degrees
- Extension = 0 to 15
- Abduction = 0 to 30
- Adduction = 0 to 25
- External rotation = 0 to 90
- Internal rotation = 0 to 70
Important point: range of motion is influenced by age, speed of movement
- As people age, they use a progressively smaller portion of the range of motion
- With ageing, comes changes loss in motor control and decrease in fast twitch fibres
- Ageing muscles are unable to produce as much force per time compared to younger muscles
- Large deficits have been shown in the plantar flexor groups
What is the acetabular labrum?
- Made up of fibrocartilage tissue
- Contains femoral head at extremes of motion, especially flexion
- Load bearing structure
- Blends with acetabular transverse ligament - provides support
- Increases stability of hip joint by deepening the acetabulum and increasing the area of articulation with head of femur
- Has a lot of vascular tissue in the internal articular surface within labrum so good healing
- sensitive shock absorber
- labrum helps stabilise and maintain congruence
- Labrum helps maintain a vacuum in the centre of the acetabulum fossa (depression at the centre created by peripheral cartilage thickening). Helps maintain stability
- Deficiency can lead to rotational instability and hypermobility which can cause abnormal load distribution
What is the angle of Wiberg and angle of anteversion?
- A malalagined acetabulum won’t adequately cover the femoral head, often leading to dislocation and osteoarthritis
- Angle of Wiberg (centre-edge angle) and angle of acetabular anteversion= describe the degree to which the acetabulum covers the femoral head
- Angle of Wiberg = extent to which the acetabulum covets femoral head in the frontal plane
- is usually 35-45 degrees. Provides a protective shelf over the femoral head
- A smaller angle contains less femoral head which increases the risk of dislocation
- Acetabular anteversion angle describes how much the acetabulum surrounds the femoral head within the horizontal plane
- Average value is 20 degrees
- Pathological increases in Acetabular anteversion decreases joint stability and liklihood of anterior dislocation
What is a pincer? What is a cam?
- Pincer = extra bone extends out over normal rim of acetabulum (over coverage of acetabulum)
- Cam = bony protrusion in neck of femur. So femoral head grinds on cartilage inside acetabulum
- You can have both cam and pincer
- Leads to stiffness in thigh, hip or groin
What is femoroacetabular impingement (FAI)?
- Abnormal inclination and torsion angles, as well as bony deformities can lead to FAIs
- This is a painful condition caused by the bone of the femoral neck bashing into or catching on the acetabulum during motion. Caused by bone overgrowth on femur or acetabulum
- Abnormal contact between the bony prominences leads to soft tissue damage in and around the joint
- This chronic repetitive trauma can lead to hip pain and decreased function
- Both Cam and pincer lesions can be present (seen on radiographs)
- this can cause labral and cartilage injury; hip osteoarthritis
- genetic factors may contribute to abnormal hip pathology e.g SNPs in HOX9
-Impingement test: doctor brings your knee up towards your chest and rotate it inwards towards your opposite shoulder. If this creates pain in the hip, it’s positive for impingement
Management:
- physical therapy and pain medication (NSAIDS)
- surgical: hip arthroscopy (minimises soft tissue disruption) use camera. Doctor can repair or clean out any damage to labrum or cartilage; correct FAI by trimming the bony rim of the acetabulum and also shaving down bump on femoral head
- pelvic osteotomies
For Cam lesion = cam resection or femoral osteoplasty is performed using a high speed burr to shave down excess bone
For pincer lesion = acetabular osteoplasty is performed
What is the angle of inclination and the angle of torsion?
Angle of inclination:
- neck to shaft angle
- inclination angle is 140-150 degrees at birth but decreases to 125 degrees in adults
- An angle of greater than 125 degrees produces coxa valga
- An angle less than 125 degrees produces coxa vara
- Both coxa valga and cox vara have benefits but the negatives outweigh them
- Coxa valga: increase moment of hip abductor force to increase joint stability but increase sheer forces across femoral neck
- Coxa vara: decreases sheer forces across femoral neck but can increase the risk of dislocation as there’s less joint stability
Angle of torsion
- medial rotatory migration of lower limb bud during fetal development
- Commonly 40 degrees in neonates but decreases after 2 years to 10-20 degrees
- Less than 12 degrees = anteversion which causes portion of femoral head to be uncovered which increases the tendency for internal rotation during gait cycle to keep femoral head in Acetabulum
- More than 12 = retroversion. Tendency for external rotation during gait cycle
Explain the gait cycle
- Joint is maximally flexed during the late swing phase of gait as limb moved forwards
- The joint extended as body moved forward at the beginning of stance phase
- Maximum extension is reached at heel off
- Abduction occurred during swing phase, reaching its maximum just after toe off
- At heel-strike, the hip joint reversed into adduction which is continued until late stance phase
- The hip joint was externally rotated throughout swing phase, rotating internally just before heel strike
- The joint remained internally rotated until late stance phase, at rotated externally
What is the trabecular structure of the proximal femur?
- The interior of the femoral head and neck are composed of spongey bone with trabecular organised into medial and lateral systems
- Lateral trabecular system resists compression of the femoral head produced when the abductor muscles contract (resists compression forces on femoral head)
- Medial system resists joint reaction forces
What are other joints of the pelvis?
Pubic symphysis:
- Secondary cartilaginous joint
- Made from fibrocartilage and hyaline cartilage
- Connects pubic bones
- Supported by anterior arcuate ligaments
Sacroiliac joints:
- Synovial joint between ala of sacrum and articular surface of ilium
- reinforced anterior, posterior, long and short sacroiliac ligaments
What are important pelvic ligaments?
- Anterior and posterior sacroiliac ligament (prevent anterior and inferior movement of sacrum)
- Sacrospinous ligament = assists external rotation of pelvis
- Sacrotuberous ligament = prevent sacrum tilting backwards
- Iliolumbar ligament = joints L4 and L5 to iliac bone crest. 5 bands
- Inguinal ligament = from ASIS to pubic tubercle. Attach oblique muscles to pelvis
What is the iliofemoral ligament?
- Capsular ligament
- High tensile strength
- Y shaped
- Twisted during standing
- keeps femoral head in contact with acetabulum
- limits external rotation, adduction and medial rotation
- prevents hyperextension of hip joint when standing