Editor’s note: This text-based course is a transcript of the webinar, Orthopedic Conditions in Pediatrics: A Primer for Physical Therapy Professionals, presented by Alicia Fernandez-Fernandez, PT, DPT, PhD, CNT.
After this course, participants will be able to:
- List at least three developmental considerations of the musculoskeletal system in the pediatric patient.
- Accurately identify the five components of a pediatric rotational profile, and explain the clinical relevance of each component.
- Describe the presentation and management of diverse pediatric orthopedic conditions, such as developmental hip dysplasia, Legg-Calve-Perthes disease, and slipped capital femoral epiphysis.
- Describe at least three situations in pediatric orthopedics that would require referral to a physician.
Introduction and Overview
Thank you for joining me today to learn about some of the most common pediatric orthopedic conditions, as well as to gain more information and recent updates on these conditions. The idea here is not to go back to what you learned in school, but more to understand the latest updates in this field. What have we learned in the last couple of decades? There may be changes in how we understand certain pediatric orthopedic issues. There may have been changes in intervention and best evidence-based approaches to treating some of these. My goal today is to provide you with some of the latest updates so you can continue to apply that knowledge to your practice.
When your client population is not primarily orthopedic-related (e.g., if you work mostly with neurological issues) why should you care about orthopedics? Even if you work in an environment where you primarily see patients with neurological impairments, over time, many of those patients will develop musculoskeletal impairments that will need to be addressed. If you're not in pediatrics and you work primarily with adults, you may see individuals with cerebral palsy, for example, when they become adults. We don't often think about that transition from childhood to adulthood. These patients may have a lot of musculoskeletal complications that go along with neurological complications. It's important for everyone working in PT to be aware of that and to understand how the musculoskeletal system develops and how pathology affects that development. Of course, if you work in orthopedics, you care about this population and you want to optimize your patient outcomes, as well as refer patients who may require care out of your scope of practice. I wanted to make this presentation about big-picture thinking. This information can help any of you even if you don't work in pediatrics. Hopefully, after this course, you will have a better understanding of some of those adult patients that come with a history of childhood disease.
Many times, we see patients with musculoskeletal diagnoses or patients with a secondary condition in addition to a musculoskeletal problem. Our tendency as PTs and as PTAs is to jump right into the diagnosis and issues we need to address. Let's treat it, let's think about some goals. It's particularly important as we see patients over time, that we have a good grasp of what happens during musculoskeletal development.
Most often when we think about musculoskeletal development, we think of motor milestones. A child sits at a specific age, they crawl or creep at a specific age, they walk at a specific age. We don't always think about how the tissues develop or look at growth at more of a microscopic level. The child's musculoskeletal system, just like any other system, is in flow and is growing. As a child grows, their musculoskeletal system can be affected by many things. It's not only the internal genetic predisposition or the pathology that the child may have but also what those children are exposed to. If the child, for example, is receiving PT, OT or other therapies, how are those therapies and those interventions impacting that musculoskeletal development? The child's environment and the opportunities they have also play a role in musculoskeletal development. Additionally, children with disabilities may not have as much opportunity to develop motor skills as children who are developing typically, because they may not be exposed to stairs or challenging tasks that would help them get better at solving those issues. If the child is not healthy, their musculoskeletal development is going to be impacted.
Facts About Growth and Change in Motor Units
The musculoskeletal system is comprised of bones, muscles, tendons, and motor units. When we think about how all that changes during childhood, there are some interesting and important facts to consider with regard to how your intervention will impact a child's development over time.
Early motor units are innervated by more than one axon. You have the motor neuron and then all the fibers are innervated by it. In the fetal period, you have several axons. Fetal movement in the third trimester is characterized by that, and as we grow, there is a process of synoptical elimination, or "trimming". As a child gets exposed to different motor experiences, there is a trimming process, or a process of refining that structure, which ultimately results in that final arrangement in which the child has one axon going to each motor unit. This process of synaptic elimination also occurs at the level of the central nervous system. You have many more synapses when you're born than at age two. The synapses that offer better results in terms of what strategies help you solve a certain task are going to prevail, and the synapses that lead you to more unsuccessful strategies are going to disappear. There is a lot of plasticity in the musculoskeletal system, and by extension in the neuromuscular system. Using this plasticity, there is a lot of potential to intervene early with children, to play a role in establishing the direction of that growth and the direction of those synapses and connections.
Muscle-Tendon Unit Development
In terms of the muscle structure itself, it's also different as we grow. Infants born prematurely have different muscles than full-term babies. The muscle tissue of preterm babies contains fewer and smaller fibers, as well as a higher interstitial fluid content. The development of muscle tissue continues through childhood. As we grow, muscles increase in length and cross-sectional area. There is also plasticity in muscle that allows it the ability to repair. We have satellite cells that respond to stress or injury, trying to repair our muscles. This is true for all children, whether they are developing typically or atypically. There's a flow. There is a transition. There's a change as they grow in all of their musculoskeletal system components.
Pathologies That Affect Developing Muscles and Tendons
Specific pathologies can affect developing muscles and tendons, including (but not limited to):
- Cerebral palsy
- Genetic disorders
These pathologies can result in changes to the structure of muscle, tendon, and other parts of the musculoskeletal system. Depending on the issue, there may be atrophy or hypertrophy. There may be a decreased cross-sectional area, loss of muscle, changes in muscle thickness, changes in sarcomere length or changes in the proportion of fibers. For example, with a child that is hypotonic (with decreased muscle tone), think of how they use their postural muscles. They have a lot of trouble holding their posture. If they are sitting at a desk, it's not just their core that's activated, everything is activated. They may be holding their arms close to their trunk and trying to hold their posture with everything they have. They start using some of what we call action muscles, such as the muscles in their arms that are supposed to be used to reach for an object. A hypotonic child needs to use these action muscles to hold their posture. Over time, there are changes in the length of those sarcomeres. If the muscle is in a perpetual contracted state, those sarcomeres are going to get shorter and you're going to get a change in that length-tension relationship or a change in the proportion of fibers. If you're using your basic action muscles to hold your posture the whole day, what do you think is going to happen to your fiber mix in that muscle? That's going to get a lot more of type I versus type II.
When I teach kinesiology, I always talk to my students about how structure determines function. Your bone is made a specific way because it's designed to bear loads. Your muscles and your tendons are designed a specific way because they're built to be pulled on. Structure determines function. However, when you use your muscles, your tendons, and your bones in a way that they are not intended to be used, over time, that is going to cause changes in the structure and architecture of the tissue. Again, the outcomes are better when we intervene as early as possible. A child with cerebral palsy who starts receiving treatment at age two is going to have a completely different clinical picture than a child who didn't begin treatment until age 12. The 12-year-old will already have established contractures and established misalignment, whereas the two-year-old still has a lot of flexibility in how their body and their musculoskeletal system is going to develop.
In PT, when a patient is immobilized or cast in a position that is not the original resting position (whether shortened or lengthened), there are actual changes in the structure of the muscle. If you cast someone in a shortened position, the sarcomere length will get shorter. If you cast someone in a lengthened position, the sarcomere length will get longer. There may also be changes in the number of sarcomeres. Similarly, spasticity, muscular imbalances, and postural changes to adapt to the environment can have the same effect.
Think of a seven-month-old child that has low tone. The typical sitting posture you're going to see from this child is one that is slouched forward. Think about what's happening to the muscles in that child's trunk. You may be thinking of the anterior aspect of the trunk, speculating that those pectorals are going to be shortened due to the forward slouch. Conversely, the muscles on the posterior aspect of the trunk, the spine extensors, are going to be lengthened. Neither of them is going to be working properly because they don't have the proper length-tension relationship. For example, our spine extensors (e.g., the erector spinae) are so important in eccentric work in everything we do. Think about bending forward to pick up an object. You better have good eccentric control in that area of the posterior trunk because otherwise, that's going to be a problem. Over time, if that child keeps maintaining that posture where some muscles are shortened and some are lengthened, none of the muscles are going to work correctly because they don't have the proper length-tension relationship.