Pediatric orthopedic surgeon Michael M. Chau, MD, PhD, allows that differentiating causes of hip pain in patients ages 10 to 19 can be a challenge, so his presentation guides primary care providers through workup steps (including which X-rays are needed) and initial treatment strategies. He discusses serious disorders requiring a prompt rule-out, offers pearls of wisdom for a more efficient diagnostic process, dispels myths about pediatric orthopedic problems, and clarifies when to consider surgery.
Well, good afternoon, everyone. Excited to be here on this webinar. Thank you for inviting me. I appreciate your time. Uh And for the opportunity to share with you my approach to managing hip pain in Children and adolescence. So for this talk, I will cover some basic concepts that um I hope you will find both interesting and helpful for taking care of patients in the primary care setting. I have no relevant disclosures. I am new to the San Francisco, Oakland and Walnut Creek communities and I started my practice at U CS F this past September. I grew up in Beaverton, Oregon, uh the headquarters of Nike Town, I did my undergraduate at Northwestern, followed by medical school at Penn State. I then uh spent about three years abroad in Sweden, uh completing a phd in cartilage Biology. I then came back to the States to uh twin cities, Minneapolis, Saint Paul, uh for my orthopedic surgery residency. I did two fellowships first in pediatric orthopedics at UT Southwester in Dallas, followed by a sports fellowship in um at C Sinai in L A and now I'm here. Uh So today, uh our learning objectives are to recognize common causes of hip pain in the pediatric population to be able to initiate appropriate work up and management in the primary care setting and to know how to keep out of trouble when dealing with pediatric hip pain. So initially, pediatric hip pain can seem like a black box because there are so many different causes and confounding diagnoses. There are intra-articular and Ticar causes but also referred pain, particularly from the lumbar spine. Then there are causes we never want to miss including infection and tumor that have wider implications and consequences beyond the hip joint. One way of narrowing, the diagnosis of pediatric hip pain is to categorize. Common causes based on age of the patient for Children between the ages of one and 12. Common causes include developmental hip dysplasia, septic arthritis, transient synovitis and Perthes disease. Older patients between the ages of 10 and 19 can present with sequela of these conditions but also have a different spectrum of diagnoses altogether including slipped capital femoral epiphysis, adolescent hip dysplasia, and femoral acetabular impingement for this talk. Um Oh and then there are a host of other causes um that can occur despite age including avascular necrosis such as from sickle cell disease, juvenile opic arthritis, neuromuscular conditions such as cerebral palsy skeletal dysplasia, sports related hip con conditions, trauma, and tumor. For this talk. Uh And for the sake of time, we will only focus on the adolescent age group. So starting basic the hip is the largest ball and socket and weight bearing joint in the body. Normally, the femoral head receives about 170 degrees of coverage from the acetabulum, which approximates a hemispherical containment when we walk or run. The body prefers to have a horizontal platform to distribute axial forces. Therefore, the upper aspect of the acetabulum together with the labrum is normally at least parallel to the ground. There are conditions where this is not the case and these conditions can lead to pain from edge floating as well as premature osteoarthritis. So, expanding on anatomy, the labrum and transverse acetabular ligament provide further stability to the hip by increasing acetabular volume by about 20% and creating a negative pressure suction seal. Additionally, uh the ligamentum teres um is believed to function as a check rein for the femoral head. The ileo the mal ligament uh highlighted in red here, which is the strongest ligament in the body along with other ligaments of the joint capsule. Further contribute to the static stability of the hip. In general, orthopedists consider 17 muscles to span and move the hip joint. This supports the rationale that physical therapy can be an effective first line treatment option for many hip conditions to strengthen the major muscle groups that dynamically stabilize the hip. While on this topic, it is also important to keep in mind that Children and adolescents rarely if ever get groin poles or strains because tendons are stronger than growth cartilage in the hypotheses. Instead, apophysitis or apothesil bogen fractures are more common in this age group in general. It is advised that when young patients complain about groin pain, it should be considered originating from the hip joint until proven otherwise, moving on to nerves. The two nerves that most likely cause pain around the hip are the lateral formal cutaneous nerve that gets compressed under the inguinal ligament and the sciatic nerve that gets compressed by the piriformis muscle. The operator nerve is another nerve that can become entrapped as it passes through the operator foramen. And this presents as needle thigh pain of clinical relevance. It is also important to note that the articular branches of the operator nerve supply both hip and knee and thus pain produced in one joint can be experienced as referred pain in the other joint development of hip uh during infancy and throughout childhood occurs by proliferation of growth cartilage at in the acetabulum and proximal femur. The acetabulum grows apposition through growth of the articular cartilage and interstitial through growth of the TRD cartilage. At the other end, the proximal uh femur enlarges by appositional growth. It is interesting to know that growth plate fractures most commonly occur through the zone of prof provisional ossification because it is the most brittle layer of the growth plate. In normal hip development, the fal head is closely associated with the acetabulum to yield a concurrent joint. The analogy is just like pouring jelly into a mold where the femoral head should be the same shape as the acetabular cup when this relationship is lost. However, uh different ace type of deformities result. So with hip subluxation depicted by pathway A. In this schematic, the acetabulum becomes shallow with gross hip dislocation depicted by pathway B, the joint becomes incongruent. And pathway C shows that early closure of the triad cartilage prevents the acetabulum from growing together with the femoral head. The spectrum of acetabular development can range from being undercovered in borderline or dysplastic hips to having abnormal coverage in acetabular retro version to being overcovered in conditions such as Coxa profunda and aab protrusion in Children and adolescents. A misshapen acetabulum can actually be asymptomatic until they seemingly and spontaneously become painful with increasing activity in sports as Children. And Aleon get older when asked by parents, why the hip was not painful sooner or why the one hip is symptomatic while both hips look similar on X ray. Um I sometimes use the analogy of an ice cube that is that even with increasing temperature, uh one degree at a time, an ice cube does not begin to melt until suddenly when the temperature rises above 32 °F similarly, until cartilage thins past a critical threshold of thickness or either a cartilage or laboral tear develops, the patient will not complain about hip pain. Adaptive changes of the hip can occur with activity as Children and adolescents grow older. This was a study done in Switzerland that looked at basketball players and found that compared to non athletes, they had a greater incidence of hip impingement as well as decreased hip internal rotation. Similarly, multiple studies have been performed on professional athletes, people who have presumably invested the so-called 10,000 hours to their sport, whether in the NFL, the major league, soccer or the National hockey league. These studies found a high incidence of hip impingement just on the screening x-rays. However, it's important to note that most of the people screened or most of the athletes screened were as thematic and thus, these were incidental findings. This study here looked at elite bass ballet dancers and found a high prevalence of hip impingement as well as Astasia. The picture on the top shows a dancer performing the splits causing a vacuum sign which signifies breaking of the negative pressure suction seal as well as lateral hip subluxation. The picture on the bottom shows a dancer performing the splits with impingement of the greater tranter against the acetabulum. It is possible although difficult to prove that activities requiring extreme flexibility, contribute to hip dysplasia versus that it is a self selection process of those who are more successful in the activity benefiting from having hip dysplasia in the first place. So a lingering perhaps philosophical question is whether we should regulate childhood participation in high level activities and or disallow early sports specialization. I think the answer is probably somewhere in the middle. So now I'm going to switch gears a little bit and we're going to cover several big nets. So first, this is a 10 year old female who presented with a traumatic left knee pain for three months. It is worse with weight bearing. And on exam, she demonstrates an intelligent gait. She has pain with hip flexion and internal rotation and she demonstrates obligate external rotation. What's that? That is when the hip is flexed, the hip then is forced into external rotation. X rays of the knee are normal and fortunately at this time, no one has performed surgery on her knee, x rays of the pelvis demonstrate an abnormal relationship between the femoral head and neck. So the diagnosis slipped capital femoral epiphysis or Skiffy. Skiffy is defined as slippage of the proximal femoral metaphysis with respect to the epiphysis through the hypertrophic zone of the growth plate and is similar to but different from growth plate fractures. It is the most common hip disorder in adolescence and the risk factors include obesity, uh male sex, certain ethnicities and endocrine disorders. Skiffy can be categorized according to its chronicity severity as well as stability. Stability has the most relevance to clinical prognosis because it relates to the risk of femoral head, avascular necrosis, stable slips are those who are able to weight bear essentially have zero risk of avascular necrosis. Whereas unstable slips or those who are not able to weight, bear, not even with assist devices have up to about 50% of risk regardless of the treatment in the clinic. After making a diagnosis of skiffy, especially those that are unstable. It is important to have the patient be nonweightbearing on the effective extremity. Many orthopedic providers including myself would recommend admitting patients to the hospital until their surgery. So on physical exam, patients may demonstrate a painful antalgic gate or a trend LBG gate that is due not to weakness of the muscles but to mechanical disadvantage of a slipped thermal head. You will also notice obligate external rotation with hip flexion and an external foot progression angle with ambulation. Patients will also have limited range of motion particularly in internal rotation and they will also be painful sometimes at the knee or the knee and the thigh as well. Standard imaging which can be obtained in the office include a P pelvis and frog like a lateral of the hip. However, if the patient is very painful or has an unstable slip, then a crosstable lateral is the preferred alternative. There are various radiographic signs. The most obvious is called Klein's line where a line drawn on the upper border of the femoral neck normally would intersect the femoral head. This is the so called ice cream falling off of the cone analogy. The goals of treatment are to prevent further slipping and minimize femoral head. Avascular necrosis treatment is usually percutaneous screw fixation and then we should also consider risk factors for contralateral stiffy, which include young age, obesity, male sex and endocrine disorders, which would indicate to us that contralateral surgery should be done at the same time. Thus, work up of these conditions such as hypothyroidism and renal osteodystrophy is recommended either in the clinic or in the emergency department, particularly if the child is young, less than 10 years old. So returning to our vignet, our patient underwent unilateral insight to screw fixation and initially did well. However, 2.5 years later, she presented again and again, complained about growing pain and demonstrated obligate external rotation. So as you can see, she developed what is called a cam lesion at the head neck junction. And so the diagnosis is therefore post skiffy thermal a tabular impingement. Since this is a bony structural problem, surgery is often indicated. And there are various techniques. This patient was treated with surgical hip dislocation, thermal osteochondral plasty and screw removal. And if I can play this video, this demonstrates how obligate external rotation occurs. It is that with reflection, the mesial bump hits the rim of the acetone and then the bump follows the shape of the rim and then it drives the hip into external rotation as the bump follows the rim posteriorly. And this is why patients will have an externally rotated resting position and also an external foot progression angle with ambulation. This video at the end here shows that after removal of the screw and after resection of the meta seal bump, it was no longer impingement with flexion and the hip could then be internally rotated with flexion to 30 degrees. All right. So here is our second V net. This is a 17 year old male water polo player. He presented with bilateral groin pain left greater than right has been going on for five years and there is no specific event that he could recall. His pain is worse with hip flexion. And when performing the egg beater kick on exam, he is tender to palpation over the interior groin. He had pain with hip flexion, a deduction and internal rotation which indicates an interior hip impingement. He also had pain with log roll and resisted straight leg flexion. These are exams that would indicate intra-articular irritation of the hip A P and lateral X rays of both hips were obtained and revealed excess bone at the head, neck junction. These are called cam lesions named after camshafts and engineering that convert rotational movement into linear movement. So this confirms the diagnosis as femoral acetabular impingement or FA I fa I is defined as hip pain resulting in uh from structural mismatch between the bony anatomy of the femoral head, neck junction and the acetabulum. If untreated. This can gradually lead to laboral tears, cartilage, degeneration and premature osteoarthritis. There are in general three types of A I lesions, cam pincer and A combination C A as we have talked about occurs when a nonshedding occurs when there is an over coverage of the femoral head by the acetabulum resulting in abnormal contact and levering fa I is a clinical diagnosis that can be made in the office. It is a clinical diagnosis because a significant proportion of patients will have radiographic sign of FA I but no symptoms. And there are many other diagnoses that can mask as hip pain. There was a recent international consensus statement devised by people who have made a career in taking care of hips that define fa I as a triad of symptoms. Clinical signs and imaging findings, patients typically present in a delayed fashion, complaining about insidious hip pain in a classic C shaped distribution around their hip that's worse with activity and pre positioning, their hip inflection and internal rotation. The most sensitive findings on clinical exam has been shown to be growing pain and a positive anterior impingement test which is performed by positioning the hip in flexion abduction and internal rotation. Patients typically also have decreased range of motion especially in flexion and internal rotation in terms of x-rays that can be obtained in the clinic. Three views are usually sufficient. We typically will want an A P pelvis, a 45 degree done lateral and a false profile view. So these views allow us to see orthogonal projections of both the femur and the acetabulum. Conventionally, there are several quantitative radiographic measurements for C am lesions. They are the A P and lateral alpha angles and also the head neck offset ratio. The pathological values are shown below. Hence, lesions are classified by the lateral and anterior center edge angles and the tonus angle and then a tabu dysplasia, which we haven't talked about yet can also be diagnosed using these measurements. There are also several qualitative radiographic signs that are commonly used but can't be subtle if you're not looking for them because the eye does not see what the mind does not know shown here are the subtypes of Pinter impingement, which can be further classified as focal versus global focal cepal retro version is the one we most commonly see in sports medicine and is characterized by a more superior crossover sign as shown here. Taler retro version also has a crossover site, but it is more global. It also has a posterior wall sign where the center of the femoral head is lateral to the posterior wall and the spine sign which we typically don't see on an A P pelvis x-ray with profunda, the floor of the acetabulum is medial to the ilo issue line and with protrusile, the thermal head is medial to that issue iliou line. After a diagnosis of fa I is made orthopedic providers typically will get some form of advanced imaging. MRI is beneficial for assessing soft tissue and labor pathology. Whereas CT is helpful for assessing bony detail as well as for surgical planning, although it does have more radiation exposure, initial treatment usually consists of rest, activity modification, nsaids and physical therapy. Now, although fa I is an anatomical problem, the logic for PT is that it treats any compensatory muscle weakness or injury such as to the rectus. So as a doctors and abductors that control the movement of the hip or dynamic stabilization, it should also be cautioned that range of motion and stretching, however, may be counterproductive and even worsen the symptoms because it is a bony problem. There is currently no consensus on specific duration of non operative treatment. What we currently do not have is evidence to support that physical therapy affects the long term natural history of FA I compared to controls. However, supervised physical therapy that focus on active and core strengthening has been shown to have improved outcomes and randomized controlled trials. Therefore, the literature continues to support non operative management as the initial treatment for FA I, the decision to proceed with surgery depends on a combination of factors. Failure of non operative management is probably the primary indication. Experts have also agreed that early surgical intervention uh may also be indicated for large cam lesions because of the risk of progression to laboral tears and also cartilage degeneration. The main contraindications to hip surgery, particularly arthroscopy are any significant signs of arthritis or hip dysplasia. Open surgery is an option for fem alar impingement but conventional techniques today is hip arthroscopy, p and C A impingement can be addressed with what's called osteochondrosis or shaving down of the bone with a burr and any associated laboral injuries can be either degraded, repaired, augmented with a graft or reconstructed with a full length graft. There are also various cartilage restoration strategies if needed. So these are videos illustrating cam impingement before and after Arthur's topic, thermoplastic. In this video on the left, you can see that with hip flexion and internal rotation, that the C A deformity impinges the acetabulum and creates a vacuum effect, which is a sign that the laboral suction seal has been violated after cam reception. As you can see, there is no longer impingement of the thermal head neck junction with the acetabulum and the labrum suction seal is maintained even with increased range of motion, particularly flexion and internal rotation. So returning to our V net, the course of treatment for our patient was bilateral hip arthroscopy with labor repair and resection of the bony cam lesion. Pre and post op x-rays are shown you can appreciate that the femoral head is more spherical in the post-operative x-rays compared to the preoperative x-rays postoperatively, we can tell our patients to expect to be toe touch, weight bearing with crutches for up to four weeks. Physical therapy is started at one week after their first follow up visit, recovery typically takes anywhere from 4 to 6 months and then return to sports if they. So choose typically occurs between 6 to 12 months, depending on the patient and depending on the sport that they choose to play. And here is our final vignette. This is a 15 year old female dancer. She presents with right anterior hip pain for the past six months and there is no associated injury. Her pain is worse with extremes of motion. On physical exam. She is tender to palpation over the groin. She has a positive favor and theater test which is pain with hip flexion abduction, external rotation and hip flexion abduction, internal rotation. She is also very flexible with a beating score of seven out of nine x-rays demonstrate that she has both a shallow acetabulum shown by these ankles as well as a cam lesion X's bone at the thermal head neck junction. In this case, ac T scan was also obtained and demonstrated abnormal rotational profiles, especially excessive sr anti version as well as femoral retroversion. So the prevailing diagnosis for this patient, yes, Alice and hip dysplasia. Alison, hip dysplasia is defined by an ace that is too shallow to support and cover the thermal head and thus predisposes edge floating and thus generation of pain and injury to the labrum and cartilage. A tabular uh dysplasia and Allison most likely results from subclinical development of dysplasia in Children that were essentially missed or were subclinical before they were symptomatic as the kid grows older and becomes more active. It occurs in approximately 1% of the population and the risk factors are the four fs being female firstborn reach and having family history. The pain is typically um in the groin. So if there is pain on the side of the hip or the back of the hip, chances are that those are other diagnoses. The pain from a tabular hip, uh dysplasia is also worse with activity and towards the end of the day, based on natural history studies. Uh we know that there is an association between hip dysplasia and early osteoarthritis in Scandinavia. Doctor Weiberg first described hip dysplasia and measured it quantitatively using the laterals edge angle as shown in the illustration on the upper right. He followed 18 patients for 30 years and found that all patients with hip dysplasia develop osteoarthritis. And he also noted that the steeper or the more shallow the acetabulum is the faster the onset of osteoarthritis. Later, Doctor Cooperman did a follow up study and confirmed the findings that uh patients with hip dysplasia over time develop osteoarthritis. So the development of osteoarthritis at least premature osteoarthritis is suspected to occur due to mechanical reasons. With the most important factor being what we've learned in physics and that is that pressure is equal to force over area. So a well covered thermal head distributes weight bearing forces across a larger surface area. Whereas a dysplastic acetabulum offers less surface area and creates edge floating. So treatment begins with non operative uh options including skillful observation lifestyle modification, physical therapy to improve muscle strength and to support the hip joint dynamically and also nsaids when non operative treatment uh do not work, then patients are treated with surgery. Typically with what's called a peri acetabular osteotomy to reorient the acetabulum to better cover the hip, uh the fem head. This can also be done sequentially or in a stage fashion with hip arthroscopy if there is any associated laboral tear or cartilage injury. So returning to our vignet, our patient failed non operative management. And so proceeded with surgery. She was found to have a laboral tear. And if you imagine the acetabulum to be a clock face, then the laboral tear was between 12 and two o'clock. Additionally, uh she had a hip dysplasia and therefore, she underwent the per tear osteotomy and show you on this video. So in this case, uh it was done sequentially. So under the same anesthesia, she underwent hip arthroscopy and then was repositioned for a per aabid osteotomy, effectively reorienting acetabulum. So that is horizontal with better coverage of the thermal head. And I can fast forward to the end final image. And then as you can see, um the tabular roof is essentially horizontal with respect to the rest of the pelvis. So, postoperatively, the main goal is simply to allow the osteotomy and labor repair to heal patients can expect to return to activities around six months. But uh we have to warn them that sometimes they can develop painful hardware, particularly if they are slender over the crest of the Elvis and that occurred in this case. So the patients underwent harder removal after one year from her surgery. You can also notice here that since fa I is a problem that occurred during growth and development of the femur, it typically does not recur after adequate reception uh has been performed. So you can still see after one year that she has a spherical thermal head. All right. So I think I'm a little ahead of schedule. Um I hope that I have at least somewhat demystified pediatric hip pain. There are numerous possible ideologies, some of which are confounding or superimposed with one another. We do not have time to discuss all of them. Those are most common in the adolescent age group, the most acute and important diagnosis. However, to rule out when pediatric hip pain presents to the office are septic arthritis, occult, thermal neck fractures that can occur based on stress. Um and runners particularly uh tumors and slipped capital femoral phesis. And this is because missing these can be life threatening or can also Destin the patient to have chronic hip pain for the rest of their lives. So, in summary, uh hip pain in the pediatric population can be generally categorized based on age and the appropriate management for hip pain can be initiated in the primary care setting prior to an orthopedic referral. And we must rule out conditions such as septic arthritis, occult, fem of neck fractures, tumor, and slip capital femoral epiphysis. So, in addition to this powerpoint, uh additional references for review uh or for further information are listed here, including the websites of Pozna, which is the Pediatric Orthotic Society of North America and also our Academy, the A A OS. So I thank you for your attention. Uh And I'm happy to answer any questions.
