Paediatric Musculoskeletal Development

Intro

And it really is all about this muscle pull and the movement patterns that we participate in throughout growth and development that cause these changes to happen. e expect these muscles to activate in appropriate ways that cause us to have the alignment we do as adults. epending on if it's a genetic condition that is causing different activation of their muscles, that's causing abnormal bony alignment then their form and their function can both be directly impacted. This is also really important because whenever these babies have atypical alignment, they're going to practise an atypical alignment thousands of times a day. So if we don't have good alignment, you're going to get potentially an exacerbation of this malformation. It's also really important because again, as they start to stand and weight shift and have these ground reaction forces, if they're placed in the incorrect locations, then again you can get bony deposition in the wrong areas. And it's also really important because it can directly affect how our brain is wired and how much our body is actually mapped in our brain. And we'll go into that a little bit more.scoliosis, muscular dystrophies, trisomy 21, CP (cerebral palsy) if they have decreased tone. All of these things can cause abnormal muscle pull and abnormal alignment of your joints, which directly affects their functional participation.

trunk

Infant:

• rigid
• barrel-shaped
• elevated ribs
• ribs perpendicular to spine

2 years:

• ribs depress
• ribs angle in relation to spine
• oval-shaped
• lateral expansion due to intercostal muscles
• diaphragm pulls ribs down
• sitting, standing and walking cause ribcage depression
• oblong-shaped rib cage

** abnormal development: persistence of barrel-shaped

upper trunk:

• prone push-up and sitting activates posterior chain musculature
• crawling: co-contraction of anterior and posterior muscles
• begin in kyphotic posture moving into a more neutral spine

** Abnormal: abnormal muscle pull can change spine position

Pelvis

• over time increased lumbar and hip extension
• begin with rounded pelvis and posterior titl
• sit and stand: activate posterior chain and core muscles and anterior pelvic tilt
• 12 months: 12 degrees of anterior pelvic tilt
• 30 months: 15 degrees of anterior tilt
• increased gluteal activity, anterior tilt decreases slightly until age 8
• adult: 10 degrees of anterior pelvic tilt

lower extremity:

lower extremity. So here, what you'll see are some norms. So at birth, we expect that infants should have around a 34 degree hip extension limitation. . As they spend time in prone and they're moving and they're activating their posterior chain and they're in this prone press position, they're going to stretch out that anterior capsule. So by six weeks we'll see that that decreases to 19 degrees of a hip extension limitation. And then really, we're at about seven degrees throughout toddlerhood.

You'll also see that they have a hip adduction limitation at the time of birth. And then as they grow and mature and start to ambulate, we'll see that they're able to bring their leg in and across their body much more. Normalising into the thirties and 20 degrees as they continue to grow and develop through toddlerhood. We see that when infants are born, they have a lot more external rotation and this decreases over time. And that they have this slight limitation in their knee flexion at time of birth with a popliteal angle of 27. And then by five years they should be able to get their knee straight when their hip is flexed at 90 degrees

LE norm: hip: flexion, abduction and lateral rotation, knee: flexion, genu varum, medial rotation of tibia; ankle: dorsiflexion, slight pronation

hip

o in the newborn we expect to see an increased angulation of the hip where it goes in the socket. So increased coxa valga between 140 and 160 degrees in the newborn. That decreases some in the adult to around 126 degrees as an average. We also see a change in the way that the femoral shaft is twisted. o that hip flexion contracture that we have at time of birth we talked a little bit about this. So this iliofemoral and ischiofemoral ligament on the anterior aspects of the hip are tighthis prone position and they continue to kind of push we will actually see those structures start to stretch out.

knee

So that knee flexion contracture as they can get hands to feet and stretch out is really going to allow them to reduce that knee flexion contracture over time. So at birth we would expect to see when it comes to knee flexion now, so that they would have about a 30 degree knee flexion contracture. This often resolves in the first few months of life. We really see this resolve with a lot of hands to feet activity. Gravity that's pulling down on their legs to be able to stretch out that posterior capsule of the knee.

f you have too much lateral tibial torsion, what we'll often see is crouched posture. The other thing that we can see is too much medial tibial torsion. And so this is when we don't have a resolution of the torsion and it stays in that internal twist. This is really not as common to see. A lot of times when we think about our kids that toe inward most of the time that medial rotation is happening a little higher up and not so much at the tibia.

Muscle pull over time

already, you have this greater trochanter as weight shifts happen, there is increased pull on the greater trochanter because there's so many muscle attachment points in that region. And as those muscles pull and attach, what we get is both compression and a laydown of bone on the uppermost border of the femoral neck. And this can actually change the angle of inclination over time. So you have these muscles like the piriformis which does a lot of external rotation and abduction. The gluteus medius that's going to do abduction, external rotation and internal rotation depending on its angle. And then the gluteus minimus it's going to be doing abduction and internal rotation. So as these muscles are all firing, as they're activating, as infants are starting to stand, as they're starting to do weight shifts, we get this compression on. So you think about all these muscles pulling in on the greater trochanter so that's going to cause laydown of more bony tissue. And as that does that we're going to see changes in the angle of inclination.

Next, let's look at those torsional forces on the femur. So we know that originally there's this medial twist on the femoral shaft. In newborns it's around 40 degrees. This decreases over time into adulthood to around 10 to 16 degrees. And what we're really looking at when we measure this is drawing a line that goes through the femoral head. And then another line that is going to go along the condyles of the femur distally. And we're looking at the angle between those two. So if you look at this change here, so what we're really looking at is we have that femoral head, that femoral neck, how much that is rotated on the shaft is really what is causing that change between the positioning of the femoral head and then that twist downwards to where the condyles are at. This changes over time due to, again, function. So this form is directly related to function and vice versa. So all of these activities that require stabilisation by the glute med will help to resolve not only the coxa valga, but also this antetorsion, this anteverion. This also helps to resolve the hip flexion contracture. So as babies are starting to crawl, as they're extending their hips, as they're using their glute max all of these things will cause different muscle pulls on the femur, on the femoral head. And then also we'll start to see some activation of the adductors along the thigh. And all of these loading forces will actually help to extend and laterally rotate the hip.

As that is done, what we will see is that twist decreases over time. Now, what happens if this doesn't go right? This is really looking at femoral anteversion. So they're looking at this femoral neck angle, axis of the femoral neck in relation to that trans condylar line. And so typically we would expect to see that this anteversion is changing and decreasing over time. But what we see is that for infants who have cerebral palsy so this is looking at the GMFCS (Gross Motor Function Classification System) which is a scale that we use to be able to classify level of involvement of individuals who have cerebral palsy. So a GMFCS level of one is the most independent, and a GMFCS level of five is the least independent when we're talking about our children with cerebral palsy. So you can see that those children who are more ambulatory, more independent will have a mean femoral neck angle that is lower than those who are more involved and less ambulatory. So their femoral neck angle remains quite high, so they remain with this femoral anteversion. And this is a really big deal because what this can do is it can actually increase risk of hip dislocation.