Cerebral Palsy: Setting the Pace in Movement Recovery
As an international authority in neuromuscular diseases and leading expert in gait analysis and movement, orthopedic surgeon Paulo R. Selber, MD, has led the establishment of gait analysis laboratories at the Association for Assistance of the Disabled Child in Sao Paulo, Brazil, and Children’s Hospital at Westmead, in Sydney, Australia. Since beginning his fellowship training, he has been trained by and collaborated with seven gait analysis laboratories throughout these countries and in the United States. In 2018, the Department of Orthopedic Surgery at NewYork-Presbyterian/Columbia University Irving Medical Center welcomed Dr. Selber as Director of Gait Recovery for the Weinberg Family Cerebral Palsy Center, where a priority in his new role is to care for the orthopedic needs of children and adults with cerebral palsy and other neuromuscular disorders and to lead and assist with the establishment of a movement analysis laboratory at Columbia.
“Having been involved with movement analysis for at least 25 years, one of my jobs is to bring the knowledge and eventually the technology of a movement laboratory to Columbia and share the expertise that I have in this area,” says Dr. Selber. “Movement analysis allows us to evaluate the pathological gait frequently observed in patients with cerebral palsy gait and to treat those patients more accurately and predictably. My passion is to enable children to walk better based on facts. And facts to me in this field come from a detailed medical history, appropriate imaging like radiographs, and three-dimensional gait analysis, which is a very precise way of measuring the way children and adults with CP walk. With 3-D movement analysis, we can measure how their muscles are being activated, the force patterns across the joints, and the movements they are using to walk through the space. This gives us way more precise insight with regard to the biomechanical problems that are presented by each patient and how we can possibly improve those alterations.”
Gait analysis reveals the patient’s cadence, velocity, length of step, and swing time. Information gathered from this analysis is provided in a series of graphs and plots that show the actual movement of the different parts of the body, muscle activity, and force production. Dr. Selber emphasizes that gait analysis is an essential tool in the preoperative assessment of a patient’s specific pathologies. It provides objective and dependable data for the identification of inefficient gait patterns, often confirming a diagnosis and guiding treatment selection. Employed postoperatively, it is the state-of-the-art methodology for the accurate assessment of outcomes.
“With 3-D movement analysis, we can measure how a patient’s muscles are being activated, the force patterns across the joints and the movements they are using to walk through the space. This gives us way more precise insight with regard to the biomechanical problems that are presented by each patient and how we can possibly improve those alterations.”
— Dr. Paulo R. Selber
“Without three-dimensional movement analysis, we can only assume a patient has actually benefitted from an intervention. Most often what we see is a different gait pattern not necessarily a better and more efficient one,” notes Dr. Selber. “The process has been validated and used extensively throughout the world and a countless number of scientific publications are now available. It is now possible to measure and study any movements in any condition, including sports. In cerebral palsy patients, for instance, we are able to identify primary problems and the compensations that these patients adopt to overcome the difficulties of the primary problem. Then we try to develop ways to treat the primary problem.”
Diagnostic Matrix: Integral to Formulating a Treatment Plan
According to Dr. Selber, an appropriate treatment plan must include what Dr. Jon Davids et al called “the diagnostic matrix” — a thorough medical history, a physical examination, imaging, and finally 3-D gait or movement analysis. “If the patient is going to have surgery, we then take them to the OR and under anesthesia, we conduct another physical exam,” explains Dr. Selber. “Patients with cerebral palsy have spasticity and dystonia. When they are awake, their brains are constantly sending atypical messages to the muscles and activating them inappropriately. Under anesthesia, they relax and that gives us another source of information as to how short or compromised a muscle really is now that it is not under the brain’s influence. An example would be a knee that could not be fully extended when the patient is awake can now be fully extended under anesthesia.”
The question then becomes how aggressive does one need to be treating the dynamic deformity that is not seen under anesthesia? Earlier in his career, Dr. Selber introduced the concept of surgical dose in CP — whereby the surgical intervention on soft tissues and bones should match the severity of the dysfunction. “To accurately define the surgical dose, one needs the diagnostic matrix,” he says.
Guiding Principles for CP Surgery
Dr. Selber has outlined four principles that should guide surgery for patients with CP, with a focus on preserving muscle power and improving biomechanical levers. “The first principle is that underlying muscle weakness is almost universal in patients with cerebral palsy from mild to significant degrees. Secondly, we know that spasticity and/or dystonia will sooner or later lead to joint and bone deformities,” says Dr. Selber. “The third principle is that if you have weak muscles trying to propel a deformed skeleton, these muscles will fail. There’s not a lot that we can do about the weak muscles, other than lots of stretching and strengthening exercises. However, we know that we can do quite a bit to try and improve and correct some of the skeletal deformities that are often seen in patients with cerebral palsy who are able to walk.”
The fourth principle, maintains Dr. Selber, is that even the most prudent conservative muscle or tendon lengthening procedure leads to further weakness, which can often be permanent. “Once you’ve lengthened the muscle, it’s weaker than it was before and this weakness may last for a long time,” he says.
Based on these four principles, Dr. Selber recommends avoiding muscle surgery as much as possible. “Sometimes surgery is inevitable because if the muscles are too contracted and shortened, the joints can’t move. In these situations, I believe we should use the smallest possible surgical dose when lengthening muscles, which should not be confused with performing minimally invasive percutaneous uncontrolled muscle lengthenings. In those cases, the incisions may be ‘small’ but the actual lengthening of the muscles lying just under the skin is often irreparable. While we know that children improve in the first year or two because those procedures temporarily decrease the spasticity, at the same time, as they grow and become heavier and taller, many of those muscles are no longer powerful as they have been over-lengthened. The real result of those interventions is actually only perceived after five, seven, 10 years, when the children’s gait becomes compromised.”
Dr. Selber understands the attraction of the percutaneous lengthening procedure to parents who are so anxious to help their children. “The muscles are cut through small incisions with little or no complications and the children look better immediately because their knees or hip are extending fully, or they are no longer walking on tippy-toes,” says Dr. Selber. “Unfortunately, many of these patients eventually come to us several years later, and they are walking very poorly. They need help and we are unable to help them. We cannot give them back the wasted muscles.”
In place of percutaneous muscle lengthening, Dr. Selber advocates for alternate lengthening techniques, which he learned under the tutelage of Jim Gage, MD, who played a pivotal role in advancing treatment for cerebral palsy by introducing gait analysis into clinical practice. Dr. Selber credits Dr. Gage for teaching him techniques that he went on to use in his own career and has encouraged other orthopedic surgeons around the world to do so as well. They include patellar tendon shortening, used to alleviate the crouch position, and semitendinosus transfer, in which the semitendinosus hamstring is taken from the seat of the shinbone and reattached above the knee so that it doesn't aggravate the knee anymore, but is useful in extending the pelvis, which is what the hamstrings do better.
Dr. Selber also recommends a lengthening technique in which the surgeon cuts the fascia around the calf muscle leaving the muscle fibers intact. “The only way this can be done appropriately is to open a small incision and visualize the procedure to make sure you are cutting the fascia and not the muscle fibers,” he says. “When it is performed through the skin, you have no control of what you’re lengthening. If we don’t want to do too much to the muscles and we know that the levers are deficient, then we can try and improve the levers. For example, if a knee flexion deformity is present, instead of lengthening the hamstrings, we can make the femurs grow into extension. We can also perform osteotomies to realign the skeleton making it easier for those weak muscles to act upon the skeleton.”
“Can we improve everybody through the right dose and the right amount of surgery? Unfortunately, there is no panacea and there is still much to be researched,” adds Dr. Selber. “But thanks to gait analysis, we are learning more and more on how to minimize long-term complications and maximize surgical outcomes.”