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. I'm 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 adolescents. 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 UCSF 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 spent about 3 years abroad in Sweden, uh, completing a PhD in cartilage biology. I then came back to the States to Twin Cities, Minneapolis-S Saint Paul for my orthopedic surgery residency. I did 2 fellowships, first in pediatric orthopedics at UT Southwestern in Dallas, followed by a sports fellowship in um at Cedars-Sinai in LA 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 workup 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 extra-articular 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 1 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 sequelae 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 idiopathic arthritis, neuromuscular conditions such as cerebral palsy, skeletal dysplasias, sports-related hip 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 is believed to function as a check rein for the femoral head. The iliofemoral 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 pulls or strains because tendons are stronger than growth cartilage in the epophyses. Instead, apophysitis or apophysal bulging 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 femoral 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 medial thigh pain. Of clinical relevance, it is also important to know 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 appositionally through growth of the articular cartilage and interstitially through growth of the triradiate cartilage. At the other end, the proximal femur enlarges by positional growth. It's interesting to know that growth plate fractures most commonly occur through the zone of provisional ossification because it is the most brittle layer of the growth plate. In normal hip development, the frontal head is closely associated with the acetabulum to yield a congruent 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 acety 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 triradiate cartilage prevents the acetabulum from growing together with the femoral head. The spectrum of acetabular development can range from being under coverage in borderline or dysplastic hips. To having abnormal coverage in acetabular retroversion to being overcovered in conditions such as coxa profunda and acetabular protrugio. In children and adolescents, a misshapen acetabulum can actually be asymptomatic until they seemingly and spontaneously become painful with increasing activity and sports as children and adolescents 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 labral 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 asymptomatic and thus these were incidental findings. This study here looked at elite ballet dancers and found a high prevalence of hip impingement as well as acetavodysplasia. 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 trochanter 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 3 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 assistive 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 non-weight bearing. On the affected 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 gait or a Trendelberg gait that is due not to weakness of the muscles but to mechanical disadvantage of a slipped femoral 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 AP pelvis and frog-like lateral of the hip. However, if the patient is very painful or has an unstable slip, then a cross-table 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 a 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 skiffy, 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, workup 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 in situ screw fixation and initially did well. However, 2.5 years later, she presented again and again complained about groin 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 that diagnosis is therefore Post skithy femoral acetabular 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, thermo osteochondroplasty, and screw removal. And if I can play this video, This demonstrates how obligated external rotation occurs. Is that with flexion, The metaphysal bump hits the rim of the acetabulum. 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 metaphseal bump, there was no longer impingement with flexion, and the hip could then be internally rotated with flexion to 30 degrees. All right, so here's our second big net. This is a 17-year-old male water polo player. He presented with bilateral groin pain, left greater than right. It has been going on for 5 years, and there is no specific event that he could recall. His pain is worse with hip flexion and when performing the eggbeater kick. On exam, he is tender to palpation over the anterior groin. He had pain with hip flexion, a deduction, and internal rotation. Which indicates anterior 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. AP and lateral X-rays of both hips were obtained. And revealed excess bone at the head neck junction. These are called can lesions. Named after camshafts in engineering that convert rotational movement into linear movement. So this confirms the diagnosis as Femoral acetabular impingement or FAI. FAI 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 labral tears, cartilage degeneration, and premature osteoarthritis. There are in general 3 types of FAI lesions CAM, pincer, and a combination. CAM, as we have talked about, occurs when a non-spherical femoral head jams into the acetabulum. Pincer impingement occurs when there is an overcoverage of the femoral head by the acetabulum, resulting in abnormal contact and levering. FAI 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 signs of FAI 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 FAI 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 positioning their hip in flexion and internal rotation. The most sensitive findings on clinical exam has been shown to be groin 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, 3 views are usually sufficient. We typically will want an AP 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 CAM lesions. They are the AP and lateral alpha angles and also the head-neck offset ratio. The pathological values are shown below. Intra lesions. are classified by the lateral and anterior center edge angles and the tonus angle. And then acetabu 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 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 pincer impingement. Which can be further classified as focal versus global, focal cephalid retroversion. is the one we most commonly see in sports medicine. And is characterized by a more superior crossover sign as shown here. As tablet 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 ischial spine sign which we typically don't see on an AP pelvis X-ray. With profunda The floor of the acetabulum is medial to the iloischial line. And with protrugio, the femoral head is medial to that ileoischial line. After a diagnosis of FAI is made, orthopedic providers typically will get some form of advanced imaging. MRI is beneficial for assessing soft tissue and labral 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 FAI 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 adductors 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 FAI. Compared to controls, however, supervised physical therapy that focus on active and core strengthening has been shown to have improved outcomes in randomized controlled trials. Therefore, the literature continues to support non-operative management as the initial treatment for FAI. 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 labral 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 femoral ostabular impingement, but conventional techniques today is hip arthroscopy. Pincer and cam impingement can be addressed with what's called osteochondroplasty or shaving down of the bone with a burr. And any associated labral injuries can be either debrided, 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 arthroscopic. Thermoplasty In this video on the left, you can see that with hip flexion and internal rotation that the cam deformity impinges the acetabulum and creates a vacuum effect, which is a sign that the labral suction seal has been violated. After CAM recession, As you can see, there is no longer impingement of the femoral 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 vignette, the course of treatment for our patient was bilateral hip arthroscopy with labral repair and resection of the bony cam lesion. Pre and post-operative X-rays are shown. You can appreciate that the femoral head is more spherical in the postoperative 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 4 weeks. Physical therapy is started at 1 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 6 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 Faber and Fader test, which is pain with hip flexion abduction external rotation and hip flexion abduction internal rotation. She is also very flexible with a beaten score of 7 out of 9. X-rays demonstrate That she has both a shallow acetabulum. shown by these angles. As well as a cam lesion. Excess bone at the femoral head neck junction. In this case, a CT scan was also obtained and demonstrated abnormal rotational profiles, especially excessive acetablar antiversion, as well as femoral retroversion. So the prevailing diagnosis for this patient. is Alison hip dysplasia. Alison's hip dysplasia is defined by an acetabulum that is too shallow to support and cover the femoral head. And thus predisposes edge floating and such generation of pain and injury to the labrum and cartilage. Acetabular dysplasia in adolescents most likely results from subclinical developmental dysplasia. In children, that were essentially missed or or 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 F's 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 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 lateral center 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 developed 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 learned in physics, and that is that pressure is equal to force over area. So a well-covered femoral head distributes weight-bearing forces across a larger surface area, whereas a dysplastic acetabulum offers less surface area. And creates edge loading. 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 periacetabular osteotomy. To reorient the acetabulum to better cover the hip, uh, the femoral head. This can also be done sequentially or in a staged fashion with hip arthroscopy if there is any associated labral tear or cartilage injury. So returning to our vignette, our patient failed non-operative management and so proceeded with Surgery She was found to have a labral tear, and if you imagine the acetabulum to be a clock face, then the labral tear was between 12 and 2 o'clock. Additionally, Uh, she had acetabular hip dysplasia and therefore she underwent the periacetabular 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 periacetaroid osteotomy. Effectively reorienting the acetabulum so that it is horizontal. With better coverage of the femoral head. And I can fast forward to the end. Final image And then as you can see, um, the acetabular 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 6 months. But, uh, we have to warn them that sometimes they can develop painful hardware, particularly if they're slender over the crest of the Pelvis and that occurred in this case. So the patient underwent harder removal after one year from her surgery. You can also notice here that since FAI is a problem that occurred during growth and development of the femur, it typically does not recur after adequate resection has been performed. So you can still see after one year that she has a spherical femoral 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 etiologies, some of which are confounding or superimposed with one another. We did not have time to discuss all of them. On those that 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 femoral neck fractures. That can occur based on stress, um, and runners, particularly, uh, tumors and slipped capital femoral epiphysis, and this is because missing these can be life-threatening or can also destine 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 femoral neck fractures, tumor, and slipped capital femoral epiphysis. So in addition to this PowerPoint, Uh, Additional references for review, uh, for further information are listed here, including the websites of POSNA, which is the Pediatric Orthopedic Society of North America, and also our academy, the AAOS. So I thank you for your attention, uh, and I'm happy to answer any questions.
