Hip

Question 1

Where does the AOR for the hip joint pass through for the sagittal plane? Frontal plane? Transverse plane?

Answer 1

• All three axes pass through the center of the femoral head.
• Sagittal: Medial-lateral
• Frontal: Anterior-Posterior
• Transverse: Superior-Inferior

Question 2

What are some potential benefits of THA?

Answer 2

Can relieve pain, restore function, and improve quality of life.

Question 3

THA. What is the most common condition affecting the hip via deterioration of the joint?

Answer 3

Osteoarthritis.

Question 4

THA. What is the total degree of anteversion at the hip joint? Why? What are some pathologies that increases or decreases in this angle could be associated with? Which angle configuration is likely to result in the development of OA?

Answer 4

Both the acetabulum and the femur have 15˚-20˚ of anteversion, this results in 30˚-40˚ of total anteversion at the hip joint.

Increases or decreases in the anteversion angle (primarily femur) are associated with degenerative hip joint disease, and labrum damage or hip dysplasia (due to decreased hip congruency).

Retroversion is more likely to result in the development of OA.

Question 5

THA. What patients is THA indicative for? What are the two approaches?

Answer 5

THA is indicated for patients who have failed conservative or previous surgical treament options for a deteriorated hip joint and who continue to have persistent, debilitating pain and a significant decrease in the activities of daily living or those with limited motion even in the absense of pain.

Posterolateral Approach & Anterior Approach.

Question 6

Describe the posterolateral approach for THA.

Answer 6

• Most common approach
• Modified to be less invasive
• Hip precautions: Flexion limited to 90˚, 45˚ of hip IR and ER, avoid adduction. WB may be restricted.
• Incision made on posterolateral spect of leg to expose an area from greater trochanter (around PSIS) to level of glute max insertion.
• Tissues cut: IT band, glute max, glute med.
• Piriformis, gemelli, obturators and posterior capsule released as a single flap for the lateral attachment via superior and inferior capsuolotomies.
• Tissues to watch for: Sciatic nerve and first perforator off the profunda femoris artery. Superior and inferior gluteal nerves and arteries (they are retracting and splitting the gluteal musculature.
• Femur repair: Femur dislocated posteriorly and femur neck is cut (around junction of femoral neck with greater trochanter)
• Acetabular repair: Femur translated anteriorly (often requires release of the anterioinferior capsule from teh femur and possibly the RF). Superior capsule maintained to prevent anteiror instability. In severe osteoporosis, may also need to release the quadratus femoris. Labrum is removed but the transverse acetabulur ligament is preserved as a landmark.

Question 7

THA Anterior Approach.

Answer 7

• Not recommended for large patients or those with osteoporiss due to both limited and difficult exposure.
• This approach requires specialized equipment and training.
• Incision made just slightly distal and posterior of the ASIS to just anterior of the greater trochanter
• Tissues cut: NO mm cut; they are retracted. Anteiror and lateral capsule may either be incised and preserved for later repair or completely removed.
• Tissues to watch for: Lateral femoral circumflex arteries and lateral femoral cutaneous nerve. Important to be cautious of TFL; can be damaged during resection of femur or just experience too much tensile force from all of the manipulation.
• Femur repair: Femur dislocated anteriorly often with help of a traction table to remove capsule from medial neck. Cut of femur neck occurs with hip joint reduced.
• Acetabular repair: Femur ER and a transverse release of the inferior capsule is performed.
• Post-op: Patients encouraged to WB immediately and often have no anti-dislocation precautions.

Question 8

What are some features of both THA procedures?

Answer 8

• Acetabulum is bored out (surface for the prosthetic while stimulating bone bleeding for healing) and replaced with the acetabulur component. Screws or coment are sometimes used to hold the socket in place.
• Femur head is replaced with a metal stem that is placed into the hollow center of the femur. Femoral stem can be either cemeted or “press fit” into the bone.
• Metal or ceramic ball placed on the uppert part of the stem. Ball replaces the damaged femoral head.
• Plastic, ceramic or metal spcaer inserted between the new ball and the socket to allow for a smooth gliding surface.

Question 9

Describe the angle of inclination for the femoral neck. What is the average for adults? Infants? Elderly? What does aging due to the inclination and why?

Answer 9

• Angle of inclination is the frontal plane angle between the femoral neck and shaft.
• Adults: 125˚
• Infants: 150˚
• Elderly: 120˚
• Aging decreases the angle of inclination because of the duration of weight bearing/compression

Question 10

What would change (theoretically) in terms of LE alignment if the angle of inclination increases?

Answer 10

Increased femoral neck angle of inclination…

*Hip Abduction

Knee varus

Foot supination

*Femur abducts to increase congruency of the hip joint.

Question 11

What would change (theoretically) in terms of LE alignment if the angle of inclination decreases?

Answer 11

Decreased femoral neck angle of inclination…

*Hip Adduction

Knee Valgus

Foot pronation

*Femur adducts to increase congruency of the hip joint

Question 12

Compare the PCSA of the TFL, glute med, and glute min. Which mm has the largest PCSA?

Answer 12

Glute med > TFL > Glute min

Question 13

Compare the moment arms for hip abduction for TFL, glute med, and glute min. Which mm has the longest moment arm?

Answer 13

Glute med > TFL > Glute min

Question 14

Which mm of glute med, TFL and glute min is best suited for hip abduction?

Answer 14

Glute med and TFL are best suited for hip abduction; both primarily contribute to the hip abduction moment.

Glute med may contribute more than TFL because of a slightly greater moment arm and larger PCSA.

*Muscles with largest PCSA and moment arm would be best suited to produce the greatest amount of hip abduction torque.

Question 15

What is the transverse plane function of the piriformis muscle with the hip in full extension? With the hip in >90˚ flexion? Why?

Answer 15

Full hip extension: External Rotation

>90˚ flexion: Internal Rotation

The piriformis (anterior sacrum -> greater trochanter) is posterior to the AOR of the hip when the hip is in full extension. When the hip is in >90˚ of flexion, the piriformis becomes anterior to the AOR. (May depend on individual’s bony structures).

Question 16

Which side should a patient use a pain to decrease joint loading on a painful hip - contralateral or ipsilateral. Why?

Answer 16

Use the cane on the contralateral side of the injured limb to reduce the hip joint loading. The torque generated by the cane is in the same direction as the torque generated by the hip abductors; it therefore helps to decrease the force that the hip abductors need to generate.

If the cane were used on the ipsilateral side of the injured limb (not suggested), the torque generated by the cane is in the same direction as the torque generated by the body weight; the hip abductors would need to generate more force to counter balance the extra torque generated by the ipsilateral side, reuslting in an increase in joint loading.

Question 17

Which side should a patient carry a load relative to an injured hip - ipsilateral or contralateral side? Why?

Answer 17

The load needs to be carried at the ipsilateral side of the injured limb. Torque generated by teh load is in the same direction as the torque generated by the hip abductors. It therefore helps to decrease the force the hip abductor needs to generate to achieve this equilibrium.

Question 18

SKILL: Craig’s exam for femoral anteversion. How might the soft tissues surrounding the greater trochanter affect your clinical examination?

Answer 18

Angle of anteversion or inclination are structural abnormalities and not synonymous with their compensatory motions. Therefore, excessive angle of femoral anteversion is a condition where the angle between the neck and posterior condyles is abnormally large. The compensation is the hip internal rotation.

Excessive anteversion of the femur does not equal hip internal rotation. It is the compensation from the abnormality.

Question 19

What are some compensations in LE alignment to adjust for…

1) Excessive femoral anteversion
2) Femoral retroversion
3) Coxa vara
4) Coxa Valga

Answer 19

1) Excessive Femoral Anteversion -> Hip IR
2) Femoral retroversion -> Hip ER
3) Coxa Vara -> Genu Valgum
4) Coxa Valga -> Genu Varum

Question 20

SKILL: Craig’s exam. How might excessive femoral anteversion impact LE alignment? Which abnormality (retroversion or excessive anteversion) would result in a greater Q-angle? Name two injuries that would be at risk for increasing the Q-Angle.

Answer 20

Excessive anteversion of the femur results in two deficiencies: decreased hip abductor moment arm and decreased hip joint congruency.* *Compensatory hip IR of the hip will address these problems.

Excessive Anteversion will result in an increase the Q-angle which has been linked to patellofemoral pain and ACL tears.

Question 21

Which ligaments make up the anterior joint capsule? When are these ligaments used? What position must the hip be in to utilize these structures? What are the consequences of not being able to achieve this position?

Answer 21

• Ilifemoral and pubofemoral ligaments are the primary ligaments that comprise the anterior joint capsule.
  
  • Iliofemoral: resists ER and potentially AB/AD
  • Pubefemoral: resists AB, slight ER
• Ischiofemoral ligament wraps around from the posterior joint to contribute as well
  
  • Ischiofemoral: resists IR and AD
• All three ligaments check hip extension.
• All 3 used functionally in late stance of gait & quiet standing. Able to see “recoil force” from these passive structures (stretched and store energy at terminal stance for following swing phases).
  
  • Shifting COM posterior to anterior joint capsule, able to rely on passive ability by capsule.
    
    • Inability to achieve this poition has significant effects on energy expenditure and may lead to increased fatigue in older adults with hip flexor contractures.

Question 22

What determines the action of the a muscle (i.e. flexion/extension)?

Answer 22

The line of pull relative to the axis of rotation.

Question 23

Interpret this figure to describe muscle action.

Answer 23

This figure shows the line of pull of the hip flexors (solid lines) and the hip extensors (dotted line) when the hip is in anatomical position.

Question 24

Interpret the figure to describe muscle action.

Answer 24

The figure shows the line of pull of the hip adductors (solid lines) and hip abductors (dotted lines) when the hip is in anatomical position.

Question 25

Interpret the figure to describe muscle action.

Answer 25

The figure shows the line of pull of the hip external rotators (solid lines) and hip internal rotators (dotted lines) when the hip is in anatomical position.

Question 26

At the hip, numerous muscles’ muscle line of pull change as a function of the hip sagittal plane position. Using your knowledge of anatomy, what mm are positioned to contribute to the hip sagittal plane motion during early swing phase of the right leg? Are there any muscles that can contribute to both movements?

Answer 26

• R hip wil be flexing as leg progresses through swing phase (primiarly hip flexors). Hip adductors such as add longus and brevis can also assist in hip flexion.
• L hip will be extending as it progresses through stance phase; primarily controlled by hip extensors (glute max, BFLH, ST, SM). Posterior fibers of add magnus contribute too.
• When hip is in flexed position (>70˚ of flexion), line of pull of add longus passes posterior to mediolateral axis of rotation of hip and therefore, acts as a hip extensors.
  
  • When hip is flexed beyond 100˚, add longus is able to create an extensor torque similar to add magnus.
  • Add longus can work both as a flexor and extensor during a spring.