77 and 78 - Pediatric Hip, Knee and Leg Flashcards
Angle of Inclination of Femur
- Angle of Inclination of Femur: angle in the frontal plane formed by the axis of the head and neck of the femur and shaft of the femur
- Infant-150°
- Adult-125°
Coxa vara
- Coxa vara: a decrease in the angle of inclination so that the distal femur is directed towards the midline and the knees are closer together (causes genu valgum)
Coxa valga
- Coxa valga: an increase in the angle of inclination so that the distal femur is directed away from the midline and the knees are farther apart (causes genu varum)
Purpose of normal inclination angle
- The inclination angle allows abductors to function with a mechanical advantage as they counterbalance body weight in one-legged stance
- If you didn’t have this, you would develop a Trendelenburg gait (unaffected side would tilt down when standing on the affected side)
- Hip abductors should be as far laterally from the hip as possible to achieve muscle stability which is greatest when the child begins to stand
Deformities of inclination angle
- Coxa vara: caused by overgrowth of the femoral epiphysis (femoral head) which leads to limb shortening and limitation of passive hip abduction*** - causes GENU VALGUM
- Coxa valgum: very uncommon
- An abnormal angle of inclination will cause a child to:
o Stand with the pelvis tilting down on the contralateral side
o Stand with the pelvis tilting down on the ipsilateral side
o Stand with the pelvis tilting down on the contralateral side
Angle of declination of femur
- Angle of Declination of Femur: angle in the transverse plane formed by the axis of the neck of the femur and the transcondylar axis of the knee with the apex of the angle lateral when looking from proximal to distal through the femur
- Infant: 30° (up to 60°) of internal rotation
- Adult: 8° to 12° of internal rotation
- Therefore, angle decreases about 20° (up to 50°) by rotating
externally, but still remains internally rotated by about 10° in the adult - NOTES: the femur at birth is naturally twisted internally, but not in the shaft, but in the NECK of the femur – as you age the internal twist of the femur will gradually externally rotate, but will stop at 10 degrees of internal rotation – This can be measured by CAT SCAN
Normal fetal position
- Normal fetal position is sitting like “Buddha”; hips and knees flexed, hips externally rotated, legs and feet internally rotated
- When the HIP is flexed in utero, it is also externally rotated
- When the LOWER LIMB is flexed in utero, it is also internally rotated
- BOTH are flexed, but hip is EXTERNALLY rotated and lower limb is INTERNALLY rotated
- NOTES: in order for the child to sit comfortably in the womb, they sit in “Buddha” but you will need to change in order to eventually stand upward
Version vs Torsion
- 1979 Subcommittee on Torsional Deformity of the Pediatric Orthopedic Society
- Standardized the terms “version” and “torsion” as it relates to rotational problems of lower limb
- Version means NORMAL – the amount of twist you see in the bone is NORMAL
- Torsion means ABNORMAL – the amount of twist in the bone is ABNORMAL
- BOTH refer to how much TWIST is in the bone
Version
- Version: angular difference between the transverse axis of motion of each end of a long bone (does NOT mean soft tissue position) – PROXIMAL joint vs DISTAL joint comparison
- Normal version is present when the angular difference is within 2 standard deviations of the mean
Torsion
- Torsion: present when the version is excessive (abnormal) or greater than 2 standard deviations outside of the mean
Femoral torsion
- Femoral torsion (abnormal) = increase in femoral version (normal)
- ANTEtorsion: medial femoral or internal femoral torsion = abnormal increase in femoral anteversion
- RETROtorsion: lateral femoral or external femoral torsion = abnormal increase in femoral retroversion
Femoral version
- Femoral version: NORMAL angular difference between the transcondylar axis of the knee and the neck of the femur
Tibial version
- Tibial version: NORMAL angular difference between the transcondylar axis of the knee and the transmalleolar axis of the ankle
Femoral anteversion
- Femoral anteversion: the NORMAL angle of femoral version
made when the axis of the neck is directed forward or
anterior from the femoral shaft - When looking at our diagram, the axis of the neck makes
a larger angle with the transcondylar axis of the knee
Femoral anteversion image
- NOTE: as the anteverted hip articulates with the normal acetabulum,
the knee will be internally rotated when femoral anteversion is present - In infants, the knee position is internally rotated, in adults, the patella
is pointed forward so that the knee is pointed forward on the shaft
Femoral retroversion
- Femoral retroversion: the angle of femoral version made when the axis of the neck is directed backward or posterior from the femoral shaft
- When looking at our diagram, the axis of the neck makes a
smaller angle with the transcondylar axis of the knee
- A femur which exhibits an internal rotation less than 2 standard deviations from normal is called o Femoral retroversion o Femoral retrotorsion o Femoral anteversion o Femoral antetorsion
- Answer: 3 – less than 2 standard deviations means NORMAL, so we say “version” and if it is internal rotation, it is “anteversion”
Femoral torsion
- Femoral torsion: ABNORMAL increase in femoral version
Antetorsion
- Antetorsion: medial or internal femoral torsion-ABNORMAL increase in femoral anteversion
Retrotorsion
- Retrotorsion: lateral or external femoral torsion-abnormal increase in femoral retroversion
Clinical vs classic biomechanics
- In classic biomechanics, torsion means a force tending to rotate an object about its long axis
- CLINICALLY, it implies deformity or abnormality – WE ARE USING THE CLINICAL DEFINITION***
Femur at birth
- At birth the femur is rotated internally to about 30°
- At the same time, the soft tissue of the hip externally rotates the thigh to about 50°
Development of femur
- The angle of declination decreases from 30° internal to about 10° internal (or femur externally rotates 20°)
- Subsequently, the soft tissue changes around the hip, internally rotate thigh from 50° external to 10° external (or internally rotates thigh 40°)
- The 8 to 12° of femoral anteversion is balanced by the external rotation of about 10° caused by normal soft tissue contraction at the hip
Summary of rotational changes
- The end result is that the knee is eventually pointed straight ahead in gait
Normal hip rotational development
- Infants: 60-90° external; 0-30° internal (3:1)
- Up to 1 year: 50-60° external; 30° internal (2:1)
- 4 years to adult: 45° external; 45° internal (1:1)
- ***NOTE: KNOW THE RATIOS ** - This is how much the hip moves total (can’t tell how much of it is from a boney cause unless you take a CT scan)
Problems with normal hip rotational development
- When this normal hip rotational development does not occur, we will have either an externally rotated or internally rotated leg and foot
- Here we are talking about how much the hip joint moves - incorporates soft tissue and bone
Result of abnormal hip rotational development – BONEY problem
- Antetorsion will cause an in-toe gait, retrotorsion an out-toe gait*
- We are talking about torsion in the BONE – twist in the BONE
Calculation of Neutral Femoral Position (NFP) = MAIN POINT
- This compares the amount of internal and external rotation sitting and then laying
- If values for internal/external rotation are the SAME in both positions, BONEY problem (torsion)
- If they are DIFFERENT, it is likely a SOFT TISSUE problem
- NEED to understand how we determine if the problem is due to soft tissue or bone
In-toe gait due to SOFT tissue
- An in-toe gait can also be caused by tightness of the internal rotators of the hip or a tight iliofemoral, pubofemoral, or ligamentum teres ligament
Out-toe gait due to SOFT tissue
- An out-toe gait can be caused by tightness of the external rotators of the hip or a tight ischiofemoral ligament
External hip rotators
External hip rotators (Notre Dame theme song: “Go Out And Get Some Quality Players”) o Gluteus maximus o Obdurators o Adductors o Gemelli o Sartorius o Quadratus femoris o Piriformis
Internal hip rotators
- Gluteus medius
- Gluteus minimus
How do we determine if the rotational deformity is due to femoral torsion or a soft tissue contracture (or laxity)?
- Need to determine neutral femoral position of the hip with the hip extended and with the hip flexed
- A difference between NFP readings with the HF and HE suggests that there is a soft tissue cause of the rotational deformity
- The same reading for NFP with the HF and HE suggests it is solely femoral torsion
- A 2 year old child presents with an out-toe gait. You measure 60° of external hip rotation and 40° of internal hip rotation with the hip flexed and extended. This is:
o Normal
o A sign of femoral retrotorsion
o A sign of femoral retroversion
- Answer: NORMAL, 1 and 3 – KNOW THE VALUES ***
- If this was for a 6 year old, 2 would be the correct answer
Uterine position leads to…
- An increase in external rotation and flexion of the hip
- Femoral anteversion caused by femoral head and neck rotating inward against the shaft-allows maximal rotation of hip in flexed position
Anteverted hip
- The anteverted hip fits well into the acetabulum in utero while the hip is hyperflexed (walking on all fours is the true physiologic position of the hip), but as soon as the hip extension begins after birth, anterversion angle must be reduced or there will be an unstable, ANTERIOR dislocatable hip or an in-toe gait - These are the TWO THINGS that could happen – KNOW THIS***
- Anteverted position increases leverage of the gluteus maximus which allows it to better maintain the body in an upright position
- However, the upright position on an anteverted leg causes the anterio-superior portion of the femoral head to be exposed
- The anteverted position of the femur is important because:
o It is the most stable position of the hip in utero
o It allows the child to walk in-toed which is more stable
o It increases the leverage of the gluteus maximus
o It increases the leverage of gluteus medius and minimus
1 = It is the most stable position of the hip in utero
3 = It increases the leverage of the gluteus maximus