ORIGINAL ARTICLE
Prevalence of Femoroacetabular Impingement Morphology in Asymptomatic Adolescents Ying Li, MD,* Peter Helvie, BS,* Matthew Mead, BS, BA,* Joel Gagnier, MSc, PhD,* Matthew R. Hammer, MD,w and Nahbee Jong, BS*
Background: Femoroacetabular impingement (FAI) can lead to acetabular chondrolabral damage and has been theorized as a causative factor in the development of osteoarthritis. The pathogenesis of FAI is unknown. The purpose of this study was to determine the prevalence of FAI morphology in asymptomatic adolescents. Methods: We identified children 10 to 18 years of age who had undergone a pelvic CT between 2007 and 2012. Exclusion criteria included hip pain, any hip pathology, bone tumor, longterm steroid use, history of chemotherapy or radiation therapy, nonambulatory status, neuromuscular disorder, chromosomal abnormality, and metabolic bone disease. Multiplanar reformatted images were created from axial images to calculate a angles and lateral center-edge angles (LCEA). Cam morphology was defined as an a-angle Z55 degrees and pincer morphology as a LCEAZ40 degrees. Results: We analyzed 558 patients (1116 hips). There were 276 males and 282 females. The average age was 14.4 years (range, 10.0 to 18.2 y). The mean a-angle was 47.9 degrees (range, 25.7 to 78 degrees) and the mean LCEA was 34.4 degrees (range, 3.9 to 58.6 degrees). Males had a significantly higher mean a-angle (49.7 vs. 46.0 degrees) (P < 0.0005) and females had a significantly higher mean LCEA (35.7 vs. 33.0 degrees) (P < 0.0005). Ninety-four adolescents (16.8%) had an a-angle Z55 degrees. Cam morphology was significantly more common in males (23.9% vs. 9.9%) (P < 0.001). A total of 181 adolescents (32.4%) had a LCEAZ40 degrees. Pincer morphology was equally common in males and females (29.7% vs. 35.1%) (P = 0.17). Thirty-four adolescents (6.1%) had mixed morphologies. Mixed morphologies were found in 21 males (7.6%) and 13 females (4.6%) (P = 0.19). The prevalence of pincer morphology increased significantly with increased age in males (P < 0.001).
From the *Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, Ann Arbor, MI; and wDepartment of Radiology, Children’s Medical Center, Dallas, TX. Investigation performed at C.S. Mott Children’s Hospital, University of Michigan, Ann Arbor, MI. None of the authors received financial support for this study. There was no external funding source for this study. The authors declare no conflicts of interest. Reprints: Ying Li, MD, Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, 1540 E. Hospital Drive, SPC 4241, Ann Arbor, MI 48109-4241. E-mail: [email protected]. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 00, Number 00, ’’ 2015
Conclusions: The prevalence of cam-type FAI morphology in asymptomatic adolescents is similar to the reported prevalence in asymptomatic adults. Pincer morphology may be more common than cam morphology in adolescents. Cam morphology is more prevalent in males, whereas pincer and mixed morphologies are equally prevalent in both sexes. Level of Evidence: Level III—diagnostic. Key Words: femoroacetabular impingement, prevalence, adolescent, cam, pincer (J Pediatr Orthop 2015;00:000–000)
F
emoroacetabular impingement (FAI) occurs when aberrant morphology of the hip results in abnormal mechanical contact between the proximal femur and rim of the acetabulum during range of motion. FAI can lead to acetabular chondrolabral damage and has been theorized as a causative factor in the development of osteoarthritis.1,2 Two types of FAI have been described. Cam impingement is caused by an aspherical femoral head that abuts against the acetabular rim during terminal hip flexion. Pincer impingement occurs when global or focal acetabular overcoverage, or acetabular retroversion results in abutment of the acetabular rim against the femoral head-neck junction.2 Mixed-type impingement, in which both cam and pincer morphologies are present, also exists. Although individuals with FAI can experience groin pain that is commonly precipitated by activities that require hip flexion,3 the prevalence of cam-type FAI in asymptomatic adults has been reported to be as high as 24% in males.4–6 Few studies have examined the prevalence of FAI morphology in the asymptomatic pediatric population.7–9 While some studies reported cam morphology in children as young as 10 years and pincer morphology in children as early as 12 years of age,7 other studies demonstrated cam morphology exclusively in adolescents with closed physes.9 The pathogenesis of FAI is unclear. Pediatric hip conditions, such as slipped capital femoral epiphysis and Legg-Calve´-Perthes disease, can result in FAI.10,11 Intense sports participation in male adolescents has been correlated with an increased risk of developing cam-type FAI,12–15 possibly secondary to alterations in the proximal femoral physis resulting from high shear stresses.16–18 An www.pedorthopaedics.com |
1
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Li et al
Volume 00, Number 00, ’’ 2015
increase in the prevalence of cam deformities has been reported in preprofessional male youth athletes as they were followed throughout adolescence.15 The primary purpose of this study was to determine the prevalence of cam and pincer morphologies in asymptomatic adolescents. The secondary purpose was to evaluate whether FAI morphology becomes more prevalent throughout adolescence.
METHODS This retrospective cross-sectional study was approved by our institutional review board. We identified children 10 to 18 years of age who had undergone a pelvic computed tomography (CT) scan for disorders unrelated to the hip at our institution between January 2007 and December 2012. Exclusion criteria included hip pain, any hip pathology, bone tumor, long-term steroid use, history of chemotherapy or radiation therapy, nonambulatory status, neuromuscular disorder, chromosomal abnormality, and metabolic bone disease. An additional exclusion criterion was any subject with CT source images >0.625-mm-section thickness, as reconstructed images could not be created to accurately evaluate for FAI morphology.
Imaging Technique and Analysis The studies were obtained with one of 2 CT scanners (GE Lightspeed VCT or Discovery 750 CT HD; General Electric Healthcare, Milwaukee, WI). Various protocols were used due to the wide range of patient conditions. Some scans were performed after the administration of oral and intravenous contrast material. Dose parameters varied by CT scanner, the protocol used, and patient size. Tube current was adjusted for most studies to minimize radiation exposure to the patient. All CT scans were acquired with axial source images of 0.625-mm thickness, which were subsequently sent through the Picture Archiving and Communication System to a GE Advantage Workstation 4.6 (General Electric Healthcare). This station was used to create multiplanar reformatted images from the axial images to calculate a-angles and lateral center-edge angles (LCEA). For the a-angle measurement, radial reformatted images were obtained in a clock-face orientation around the center of the femoral neck. The a-angle was measured between the anterior and superior regions of the femoral head-neck junction, at the location at which the headneck offset was greatest.19,20 We used the method described by Notzli et al21 to measure the a-angle. A best-fit circle was first drawn around the margin of the femoral head. Next, a line was drawn along the long axis of the femoral neck and a second line was drawn from the center of the circle to the point at which the femoral head-neck junction extended beyond the circle. The angle between the 2 lines was the a-angle (Fig. 1). Cam morphology was defined as an a-angle Z55 degrees.21 To measure the LCEA, axial images were first reformatted to eliminate any pelvic tilt. The center of the femoral head was then identified using axial, coronal, and
2 | www.pedorthopaedics.com
FIGURE 1. Radial image demonstrating measurement of the a-angle.
sagittal plane imaging. Next, a line was drawn from the center of the femoral head to the most lateral aspect of the acetabulum and a second vertical line was drawn from the center of the femoral head on the coronal image. The angle between the 2 lines was the LCEA (Fig. 2). Pincer morphology was defined as a LCEAZ40 degrees.22
Statistical Analysis We calculated the counts and percentages of each FAI type, unilateral and bilateral, for male and female sex, as well as the odds ratios (OR) and relative risks (RR) with 95% confidence intervals (CI). We then performed w2 analyses for all categorical comparisons of FAI types
FIGURE 2. Coronal image demonstrating measurement of the lateral center-edge angle. Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Volume 00, Number 00, ’’ 2015
FAI Morphology in Asymptomatic Adolescents
TABLE 1. Mean a-Angles for Males and Females by Laterality Mean a-Angle (deg.) 95% Confidence Interval
Sex Males Right (hips = 276) Left (hips = 276) Females Right (hips = 282) Left (hips = 282)
49.9 49.7
49.3-50.5 49.0-50.5
46.1 46.1
45.4-46.7 45.4-46.7
between males and females. In addition, 4 models were conducted using logistic regression to identify predictive determinants of a-angle and LCEA. Two models examined the predictive effect of sex and age on a-angle and LCEA. The final 2 models examined the effect of age on a-angle and LCEA stratified by sex. SPSS v. 22.0 statistical package (IBM Corp., Armonk, NY) was used for all analyses and significance was set at P = 0.05. FIGURE 3. The percentage distribution of a-angles in males and females. The 95% confidence intervals are shown by the error bars.
RESULTS We included a total of 558 subjects (1116 hips). There were 276 males (49.5%) and 282 females (50.5%). The average age was 14.4 years (range, 10.0 to 18.2 y). The mean a-angle for the study group was 47.9 degrees (range, 25.7 to 78 degrees) and the mean LCEA was 34.4 degrees (range, 3.9 to 58.6 degrees). Mean a-angles and LCEA for males and females are presented in Tables 1 and 2. Males had a significantly higher mean a-angle (49.7 vs. 46.0 degrees) (P < 0.0005) and females had a significantly higher mean LCEA (35.7 vs. 33.0 degrees) (P < 0.0005). Ninety-four adolescents (16.8%) in the study population had an a-angle Z55 degrees (11.6% unilateral, 5.2% bilateral). Cam morphology was significantly more common in males (23.9%, 66 of 276) than in females (9.9%, 28 of 282) (P < 0.001, OR = 2.85, RR = 1.55). Unilateral cam morphology was found in 44 males (15.9%) and 21 females (7.4%). Bilateral cam morphology was noted in 29 males (8.0%) and 7 females (2.5%). Age and a-angles were similar between males and females in the cam group. The percentage distribution of a-angles for males and females is shown in Figure 3. A total of 181 adolescents (32.4%) had a LCEAZ40 degrees (21.5% unilateral, 10.9% bilateral). Pincer morphology was more common in females (35.1%, 99 of 282) than in males (29.7%, 82 of 276), but this was not statistically significant (P = 0.17). Unilateral pincer morphology was observed in 58 males (21.0%) and 62 females (22.0%). Bilateral pincer morphology was found
in 24 males (8.7%) and 37 females (13.1%). There was no significant difference in age and LCEA between males and females in the pincer group. Figure 4 shows the percentage distribution of LCEA for males and females. Thirty-four adolescents (6.1%) had mixed morphologies. Mixed morphologies were found in 21 males (7.6%) and 13 females (4.6%) (P = 0.19). Unilateral cam and pincer morphologies were seen in 14 males (5.1%) and 8 females (2.8%). Unilateral cam and contralateral pincer morphologies were noted in 6 males (2.2%) and 4 females (1.4%). Bilateral cam and pincer morphologies were observed in 1 male (0.4%) and 1 female (0.4%). Age, a-angles, and LCEA were similar between males and females in the mixed morphology group. Table 3 and Figure 5 present the frequency of cam and pincer morphologies by age and sex. The prevalence of a-angles Z55 degrees remained stable in males and females throughout adolescence. The prevalence of
TABLE 2. Mean Lateral Center-Edge Angles (LCEA) for Males and Females by Laterality Sex
Mean LCEA (deg.) 95% Confidence Interval
Males Right (hips = 276) Left (hips = 276) Females Right (hips = 282) Left (hips = 282)
Copyright
r
32.4 33.6
31.5-33.4 32.7-34.5
35.1 36.2
34.4-35.8 35.4-36.9
2015 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 4. The percentage distribution of lateral center-edge angles in males and females. The 95% confidence intervals are shown by the error bars. www.pedorthopaedics.com |
3
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Li et al
Volume 00, Number 00, ’’ 2015
TABLE 3. Prevalence of Abnormal a-Angles and Lateral Center-Edge Angles (LCEA) by Age and Sex n (%) Hips With a-Angle Z55 Degrees
Hips (n) Male
Female
Male
10.0-10.9 11.0-11.9 12.0-12.9 13.0-13.9 14.0-14.9 15.0-15.9 16.0-16.9 17.0-17.9 18.0-18.9
Age Range (y)
28 40 26 45 23 39 45 29 1
24 16 19 22 44 54 49 51 3
9 (32.1) 8 (20.0) 6 (23.1) 10 (22.2) 6 (26.1) 11(28.2) 8 (17.8) 8 (27.6) 0 (0)
10.0-18.9
276
282
66 (23.9)
LCEAZ40 degrees increased significantly with increased age in males (P < 0.001; OR = 1.30; CI, 1.19-1.42) but remained stable in females.
DISCUSSION Murray23 first described the tilt deformity as an abnormal relationship between the femoral head and neck that was a likely etiology for osteoarthritis of the hip. Nearly 4 decades later, Ganz and colleagues coined the term “femoroacetabular impingement” based on their inspection of chondrolabral damage patterns during surgical dislocation of the hip. These authors classified FAI into cam and pincer types based on the location of the abnormal morphology.2 Subsequently, multiple studies have examined the prevalence of FAI in asymptomatic adults.4–6,24–27 Hack and colleagues performed magnetic resonance imaging (MRI) evaluations of 200 adult volunteers and found cam morphology in 14% of the study group. Cam morphology was more common in men, with 24.7% of males and 5.4% of females demonstrating elevated a-angles.4 Similarly, the Copenhagen Osteoarthritis Study reported that 17% of male and 4% of female adults had cam morphology on anteroposterior (AP) pelvis xrays.26 Chakraverty et al25 found that 66% of asymptomatic adults demonstrated at least 1 abnormal parameter associated with cam-type or pincer-type FAI on CT evaluation. Few studies have examined the prevalence of FAI in asymptomatic pediatric patients.7–9 Monazzam and colleagues reported cam morphology in 10.2% of males and 2.5% of females on CT evaluation. Cam and pincer morphologies were seen in children as early as 10 and 12 years of age, respectively. Males were over 4 times more likely to have an a-angle Z55 degrees.7 Schmitz and colleagues compared AP pelvic radiographs made with EOS imaging in asymptomatic adolescents with and without scoliosis. The authors found that 92.8% of the study group demonstrated at least 1 parameter suggesting impingement morphology. An abnormal AP a-angle was noted in 5.6% of males and 6.7% of females, and was significantly more common in the adolescents without scoliosis.8 Carsen and colleagues reported cam morpho-
4 | www.pedorthopaedics.com
Female 4 1 1 2 2 8 3 7 0
(16.7) (6.3) (5.3) (9.1) (4.5) (14.8) (6.1) (13.7) (0)
28 (9.9)
Hips With LCEAZ40 Degrees Male 1 2 1 12 10 16 19 21 0
(3.6) (5.0) (3.8) (26.7) (43.5) (41.0) (42.2) (72.4) (0)
82 (29.7)
Female 7 6 8 4 11 18 18 25 2
(29.2) (37.5) (42.1) (18.2) (25.0) (33.3) (36.7) (49.0) (66.7)
99 (35.1)
logy exclusively in adolescents with closed physes. None of the subjects in their prephyseal closure group had elevated a-angles on MRI, whereas 14% of their closed physeal group had elevated a-angles and all were male.9 Our study is the largest published series to date on the prevalence of FAI morphology in asymptomatic adolescents. We found a 16.8% overall prevalence of cam-type FAI morphology and this was nearly 3 times more common in males. These results are comparable with previous reports on asymptomatic adolescents and adults.4–9,24–27 We noted a higher prevalence of cam morphology than Monazzam et al7 and Schmitz et al.8 This may be secondary to the use of different measurement techniques for the a-angle. We measured the a-angle on radial reformatted images. Monazzam et al7 measured the a-angle on an axial oblique CT image and Schmitz et al8 measured the a-angle on an AP pelvic radiograph. Cam morphology is most commonly found at the anterosuperior aspect of the femoral head. Rakhra et al20 showed that axial oblique imaging missed a substantial percentage of cam deformities that were detected on radial plane imaging as the axial oblique image can only detect cam lesions that are at the anterior aspect of the femoral head. Likewise, the AP a-angle can only detect a cam deformity that is at the superior aspect of the femoral head. Similar to Monazzam et al’s7 findings, we observed cam morphology in children as young as 10 years. These results are in contrast to Carsen et al’s9 study, in which cam lesions were only noted in adolescents with closed physes. The prevalence of cam morphology remained stable throughout adolescence in our study population. The appropriate threshold for the determination of an abnormal a-angle is still controversial. Although some prevalence studies have defined cam morphology as an a-angle Z50.5 degrees,4,9 several authors have shown that this likely yields many false-positive results.28,29 We chose to use an aangle cutoff Z55 degrees based on Notzli et al’s21 original description of the a-angle in symptomatic adults. This threshold seems to be the most widely used in the literature.7,13,14,17,20,25 Some authors have suggested even higher aangle thresholds5,26,29,30 and different cutoffs based on sex.4,26 One third of our study population had a LCEAZ40 degrees, which is higher than the prevalence in symptom-free Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Volume 00, Number 00, ’’ 2015
FAI Morphology in Asymptomatic Adolescents
FIGURE 5. Frequency of abnormal parameters associated with femoroacetabular impingement by age among (A) males and (B) females.
adolescents reported by Monazzam et al7 and Schmitz et al.8 Fewer studies have examined the prevalence of pincer FAI in asymptomatic adults.24,25,27 Chakraverty et al25 observed at least 1 pincer-type characteristic in 36.7% of men and 42.5% of women. Pincer morphology was more common in our female subjects as well (35.1% vs. 29.7%), but this was not statistically significant. We observed a significant increase in prevalence of pincer morphology in males with increased age. Monazzam et al7 noted a similar trend in their study, in which a LCEAZ40 degrees was found in 4.8% of males 12 to 13 years of age and 37.5% of males 16 to 19 years of age. We agree with these authors that progressive ossification of the acetabulum with increasing age may explain the increase in LCEA. Cam and pincer morphologies commonly coexist.25,27 We noted mixed morphologies in 6.1% of our subjects. The pathogenesis of FAI is still unknown. The prevalence of hip osteoarthritis has been reported to be 3 to 8.5 times higher in athletes than in nonathletes.31–33 Male athletes, especially those involved in running and jumping sports, have been found to develop osteoarthritis of the hip at an earlier age.31–37 Murray and Duncan36 noted an increased prevalence of the tilt deformity of the proximal femur and increased hip pain in adolescents engaged in a higher level of athletic activity. Several recent studies on elite male adolescent athletes involved in basketball, soccer, and ice hockey have demonstrated increased prevalence of cam-type FAI compared with controls, supporting a developmental etiology for the deformity.12–15,17 Agricola and colleagues followed 63 preprofessional male soccer players during adolescence and reported a significant increase in the prevalence of cam morphology over time, particularly in the boys with an open proximal femoral physis at baseline. After physeal closure, the overall prevalence and severity of the cam deformity remained stable.15 Siebenrock et al14 and Philippon et al13 also found a significant correlation between increased age and increased a-angles in male adolescents participating in high-impact sports. One possible explanation is that repetitive high stresses on the proximal femoral physis result in growth modulation and development of the cam deformity, similar to the pathologic skeletal growth alterations in gymnasts and baseball players.14 This theory is Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
supported by a study by Carter et al,16 who observed that the cam lesion occurs in close proximity to the proximal femoral physis in skeletally immature patients with symptomatic FAI. Similarly, Siebenrock et al18 reported increased lateral extension of the proximal femoral epiphysis in male adults with symptomatic cam-type FAI. There are several limitations to our study, mostly related to its retrospective design. Although we reviewed all of the subjects’ medical records to ensure that patients with hip pain, hip pathology, or any other condition that could be associated with hip problems were excluded, patients who had hip complaints that were not documented may have been inadvertently included. We were unable to interview patients regarding their activity level, such as participation in high-intensity sports. We also could not examine patients’ hip range of motion and perform an impingement test. We have no follow-up on these patients so we do not know if any of them developed hip complaints since their CT scan. Although there are many radiographic measurements that define FAI morphology, we only measured the a-angle and LCEA. We chose to use these 2 measurements in our study because the a-angle and LCEA are the most commonly used measurements in clinical practice to evaluate for cam and pincer morphology, respectively. A portion of the proximal femur and acetabulum is unossified in skeletally immature individuals, which cannot be evaluated on a CT scan. A similar MRI study would provide better visualization of the anatomy of the developing hip joint. However, it would be difficult to perform a prevalence study with a large study population that would satisfy our exclusion criteria as a MRI of the pelvis is not a commonly obtained study in asymptomatic adolescents. Lastly, FAI is a dynamic condition and should not be diagnosed solely on static radiographic imaging studies. In conclusion, our study demonstrates that the prevalence of cam-type FAI morphology in asymptomatic adolescents is similar to the reported prevalence in asymptomatic adults. Pincer morphology may be more common than cam morphology in adolescents. Cam www.pedorthopaedics.com |
5
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Li et al
morphology is more prevalent in males, whereas pincer and mixed morphologies are equally common in both sexes. The prevalence of cam morphology remained stable, whereas the prevalence of pincer morphology increased throughout adolescence in males. Our findings support a developmental etiology for FAI. Further studies are necessary to examine the prevalence of FAI morphology in younger children with long-term followup to determine which patients become symptomatic. REFERENCES 1. Beck M, Kalhor M, Leunig M, et al. Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br. 2005;87:1012–1018. 2. Ganz R, Parvizi J, Beck M, et al. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003; 417:112–120. 3. Clohisy JC, Knaus ER, Hunt DM, et al. Clinical presentation of patients with symptomatic anterior hip impingement. Clin Orthop Relat Res. 2009;467:638–644. 4. Hack K, Di Primio G, Rakhra K, et al. Prevalence of cam-type femoroacetabular impingement morphology in asymptomatic volunteers. J Bone Joint Surg Am. 2010;92:2436–2444. 5. Jung KA, Restrepo C, Hellman M, et al. The prevalence of cam-type femoroacetabular deformity in asymptomatic adults. J Bone Joint Surg Br. 2011;93:1303–1307. 6. Reichenbach S, Juni P, Werlen S, et al. Prevalence of cam-type deformity on hip magnetic resonance imaging in young males: a cross-sectional study. Arthritis Care Res (Hoboken). 2010;62: 1319–1327. 7. Monazzam S, Bomar JD, Dwek JR, et al. Development and prevalence of femoroacetabular impingement-associated morphology in a paediatric and adolescent population: a CT study of 225 patients. Bone Joint J. 2013;95-B:598–604. 8. Schmitz MR, Bittersohl B, Zaps D, et al. Spectrum of radiographic femoroacetabular impingement morphology in adolescents and young adults: an EOS-based double-cohort study. J Bone Joint Surg Am. 2013;95:e90. 9. Carsen S, Moroz PJ, Rakhra K, et al. The Otto Aufranc Award. On the etiology of the cam deformity: a cross-sectional pediatric MRI study. Clin Orthop Relat Res. 2014;472:430–436. 10. Leunig M, Casillas MM, Hamlet M, et al. Slipped capital femoral epiphysis: early mechanical damage to the acetabular cartilage by a prominent femoral metaphysis. Acta Orthop Scand. 2000;71:370–375. 11. Tannast M, Hanke M, Ecker TM, et al. LCPD: reduced range of motion resulting from extra- and intraarticular impingement. Clin Orthop Relat Res. 2012;470:2431–2440. 12. Agricola R, Bessems JH, Ginai AZ, et al. The development of Camtype deformity in adolescent and young male soccer players. Am J Sports Med. 2012;40:1099–1106. 13. Philippon MJ, Ho CP, Briggs KK, et al. Prevalence of increased alpha angles as a measure of cam-type femoroacetabular impingement in youth ice hockey players. Am J Sports Med. 2013;41: 1357–1362. 14. Siebenrock KA, Ferner F, Noble PC, et al. The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity. Clin Orthop Relat Res. 2011;469:3229–3240. 15. Agricola R, Heijboer MP, Ginai AZ, et al. A cam deformity is gradually acquired during skeletal maturation in adolescent and young male soccer players: a prospective study with minimum 2-year follow-up. Am J Sports Med. 2014;42:798–806. 16. Carter CW, Bixby S, Yen YM, et al. The relationship between cam lesion and physis in skeletally immature patients. J Pediatr Orthop. 2014;34:579–584.
6 | www.pedorthopaedics.com
Volume 00, Number 00, ’’ 2015
17. Siebenrock KA, Behning A, Mamisch TC, et al. Growth plate alteration precedes cam-type deformity in elite basketball players. Clin Orthop Relat Res. 2013;471:1084–1091. 18. Siebenrock KA, Wahab KH, Werlen S, et al. Abnormal extension of the femoral head epiphysis as a cause of cam impingement. Clin Orthop Relat Res. 2004;(418):54–60. 19. Pfirrmann CW, Mengiardi B, Dora C, et al. Cam and pincer femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients. Radiology. 2006;240:778–785. 20. Rakhra KS, Sheikh AM, Allen D, et al. Comparison of MRI alpha angle measurement planes in femoroacetabular impingement. Clin Orthop Relat Res. 2009;467:660–665. 21. Notzli HP, Wyss TF, Stoecklin CH, et al. The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement. J Bone Joint Surg Br. 2002;84:556–560. 22. Tonnis D, Heinecke A. Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 1999;81:1747–1770. 23. Murray RO. The aetiology of primary osteoarthritis of the hip. Br J Radiol. 1965;38:810–824. 24. Leunig M, Juni P, Werlen S, et al. Prevalence of cam and pincer-type deformities on hip MRI in an asymptomatic young Swiss female population: a cross-sectional study. Osteoarthritis Cartilage. 2013;21:544–550. 25. Chakraverty JK, Sullivan C, Gan C, et al. Cam and pincer femoroacetabular impingement: CT findings of features resembling femoroacetabular impingement in a young population without symptoms. AJR Am J Roentgenol. 2013;200:389–395. 26. Gosvig KK, Jacobsen S, Sonne-Holm S, et al. The prevalence of cam-type deformity of the hip joint: a survey of 4151 subjects of the Copenhagen Osteoarthritis Study. Acta Radiol. 2008;49:436–441. 27. Laborie LB, Lehmann TG, Engesaeter IO, et al. Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 2011;260:494–502. 28. Bixby SD, Kienle KP, Nasreddine A, et al. Reference values for proximal femoral anatomy in adolescents based on sex, physis, and imaging plane. Am J Sports Med. 2013;41:2074–2082. 29. Sutter R, Dietrich TJ, Zingg PO, et al. How useful is the alpha angle for discriminating between symptomatic patients with cam-type femoroacetabular impingement and asymptomatic volunteers? Radiology. 2012; 264:514–521. 30. Pollard TC, Villar RN, Norton MR, et al. Femoroacetabular impingement and classification of the cam deformity: the reference interval in normal hips. Acta Orthop. 2010;81:134–141. 31. L’Hermette M, Polle G, Tourny-Chollet C, et al. Hip passive range of motion and frequency of radiographic hip osteoarthritis in former elite handball players. Br J Sports Med. 2006;40:45–49. discussion 45-49. 32. Lindberg H, Roos H, Gardsell P. Prevalence of coxarthrosis in former soccer players. 286 players compared with matched controls. Acta Orthop Scand. 1993;64:165–167. 33. Vingard E, Alfredsson L, Goldie I, et al. Sports and osteoarthrosis of the hip. An epidemiologic study. Am J Sports Med. 1993;21: 195–200. 34. Drawer S, Fuller CW. Propensity for osteoarthritis and lower limb joint pain in retired professional soccer players. Br J Sports Med. 2001;35:402–408. 35. Kettunen JA, Kujala UM, Raty H, et al. Factors associated with hip joint rotation in former elite athletes. Br J Sports Med. 2000;34: 44–48. 36. Murray RO, Duncan C. Athletic activity in adolescence as an etiological factor in degenerative hip disease. J Bone Joint Surg Br. 1971;53:406–419. 37. Vingard E, Alfredsson L, Malchau H. Osteoarthrosis of the hip in women and its relationship to physical load from sports activities. Am J Sports Med. 1998;26:78–82.
Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Prevalence of Femoroacetabular Impingement Morphology in Asymptomatic Adolescents Ying Li, MD,* Peter Helvie, BS,* Matthew Mead, BS, BA,* Joel Gagnier, MSc, PhD,* Matthew R. Hammer, MD,w and Nahbee Jong, BS*
Background: Femoroacetabular impingement (FAI) can lead to acetabular chondrolabral damage and has been theorized as a causative factor in the development of osteoarthritis. The pathogenesis of FAI is unknown. The purpose of this study was to determine the prevalence of FAI morphology in asymptomatic adolescents. Methods: We identified children 10 to 18 years of age who had undergone a pelvic CT between 2007 and 2012. Exclusion criteria included hip pain, any hip pathology, bone tumor, longterm steroid use, history of chemotherapy or radiation therapy, nonambulatory status, neuromuscular disorder, chromosomal abnormality, and metabolic bone disease. Multiplanar reformatted images were created from axial images to calculate a angles and lateral center-edge angles (LCEA). Cam morphology was defined as an a-angle Z55 degrees and pincer morphology as a LCEAZ40 degrees. Results: We analyzed 558 patients (1116 hips). There were 276 males and 282 females. The average age was 14.4 years (range, 10.0 to 18.2 y). The mean a-angle was 47.9 degrees (range, 25.7 to 78 degrees) and the mean LCEA was 34.4 degrees (range, 3.9 to 58.6 degrees). Males had a significantly higher mean a-angle (49.7 vs. 46.0 degrees) (P < 0.0005) and females had a significantly higher mean LCEA (35.7 vs. 33.0 degrees) (P < 0.0005). Ninety-four adolescents (16.8%) had an a-angle Z55 degrees. Cam morphology was significantly more common in males (23.9% vs. 9.9%) (P < 0.001). A total of 181 adolescents (32.4%) had a LCEAZ40 degrees. Pincer morphology was equally common in males and females (29.7% vs. 35.1%) (P = 0.17). Thirty-four adolescents (6.1%) had mixed morphologies. Mixed morphologies were found in 21 males (7.6%) and 13 females (4.6%) (P = 0.19). The prevalence of pincer morphology increased significantly with increased age in males (P < 0.001).
From the *Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, Ann Arbor, MI; and wDepartment of Radiology, Children’s Medical Center, Dallas, TX. Investigation performed at C.S. Mott Children’s Hospital, University of Michigan, Ann Arbor, MI. None of the authors received financial support for this study. There was no external funding source for this study. The authors declare no conflicts of interest. Reprints: Ying Li, MD, Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, 1540 E. Hospital Drive, SPC 4241, Ann Arbor, MI 48109-4241. E-mail: [email protected]. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 00, Number 00, ’’ 2015
Conclusions: The prevalence of cam-type FAI morphology in asymptomatic adolescents is similar to the reported prevalence in asymptomatic adults. Pincer morphology may be more common than cam morphology in adolescents. Cam morphology is more prevalent in males, whereas pincer and mixed morphologies are equally prevalent in both sexes. Level of Evidence: Level III—diagnostic. Key Words: femoroacetabular impingement, prevalence, adolescent, cam, pincer (J Pediatr Orthop 2015;00:000–000)
F
emoroacetabular impingement (FAI) occurs when aberrant morphology of the hip results in abnormal mechanical contact between the proximal femur and rim of the acetabulum during range of motion. FAI can lead to acetabular chondrolabral damage and has been theorized as a causative factor in the development of osteoarthritis.1,2 Two types of FAI have been described. Cam impingement is caused by an aspherical femoral head that abuts against the acetabular rim during terminal hip flexion. Pincer impingement occurs when global or focal acetabular overcoverage, or acetabular retroversion results in abutment of the acetabular rim against the femoral head-neck junction.2 Mixed-type impingement, in which both cam and pincer morphologies are present, also exists. Although individuals with FAI can experience groin pain that is commonly precipitated by activities that require hip flexion,3 the prevalence of cam-type FAI in asymptomatic adults has been reported to be as high as 24% in males.4–6 Few studies have examined the prevalence of FAI morphology in the asymptomatic pediatric population.7–9 While some studies reported cam morphology in children as young as 10 years and pincer morphology in children as early as 12 years of age,7 other studies demonstrated cam morphology exclusively in adolescents with closed physes.9 The pathogenesis of FAI is unclear. Pediatric hip conditions, such as slipped capital femoral epiphysis and Legg-Calve´-Perthes disease, can result in FAI.10,11 Intense sports participation in male adolescents has been correlated with an increased risk of developing cam-type FAI,12–15 possibly secondary to alterations in the proximal femoral physis resulting from high shear stresses.16–18 An www.pedorthopaedics.com |
1
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Li et al
Volume 00, Number 00, ’’ 2015
increase in the prevalence of cam deformities has been reported in preprofessional male youth athletes as they were followed throughout adolescence.15 The primary purpose of this study was to determine the prevalence of cam and pincer morphologies in asymptomatic adolescents. The secondary purpose was to evaluate whether FAI morphology becomes more prevalent throughout adolescence.
METHODS This retrospective cross-sectional study was approved by our institutional review board. We identified children 10 to 18 years of age who had undergone a pelvic computed tomography (CT) scan for disorders unrelated to the hip at our institution between January 2007 and December 2012. Exclusion criteria included hip pain, any hip pathology, bone tumor, long-term steroid use, history of chemotherapy or radiation therapy, nonambulatory status, neuromuscular disorder, chromosomal abnormality, and metabolic bone disease. An additional exclusion criterion was any subject with CT source images >0.625-mm-section thickness, as reconstructed images could not be created to accurately evaluate for FAI morphology.
Imaging Technique and Analysis The studies were obtained with one of 2 CT scanners (GE Lightspeed VCT or Discovery 750 CT HD; General Electric Healthcare, Milwaukee, WI). Various protocols were used due to the wide range of patient conditions. Some scans were performed after the administration of oral and intravenous contrast material. Dose parameters varied by CT scanner, the protocol used, and patient size. Tube current was adjusted for most studies to minimize radiation exposure to the patient. All CT scans were acquired with axial source images of 0.625-mm thickness, which were subsequently sent through the Picture Archiving and Communication System to a GE Advantage Workstation 4.6 (General Electric Healthcare). This station was used to create multiplanar reformatted images from the axial images to calculate a-angles and lateral center-edge angles (LCEA). For the a-angle measurement, radial reformatted images were obtained in a clock-face orientation around the center of the femoral neck. The a-angle was measured between the anterior and superior regions of the femoral head-neck junction, at the location at which the headneck offset was greatest.19,20 We used the method described by Notzli et al21 to measure the a-angle. A best-fit circle was first drawn around the margin of the femoral head. Next, a line was drawn along the long axis of the femoral neck and a second line was drawn from the center of the circle to the point at which the femoral head-neck junction extended beyond the circle. The angle between the 2 lines was the a-angle (Fig. 1). Cam morphology was defined as an a-angle Z55 degrees.21 To measure the LCEA, axial images were first reformatted to eliminate any pelvic tilt. The center of the femoral head was then identified using axial, coronal, and
2 | www.pedorthopaedics.com
FIGURE 1. Radial image demonstrating measurement of the a-angle.
sagittal plane imaging. Next, a line was drawn from the center of the femoral head to the most lateral aspect of the acetabulum and a second vertical line was drawn from the center of the femoral head on the coronal image. The angle between the 2 lines was the LCEA (Fig. 2). Pincer morphology was defined as a LCEAZ40 degrees.22
Statistical Analysis We calculated the counts and percentages of each FAI type, unilateral and bilateral, for male and female sex, as well as the odds ratios (OR) and relative risks (RR) with 95% confidence intervals (CI). We then performed w2 analyses for all categorical comparisons of FAI types
FIGURE 2. Coronal image demonstrating measurement of the lateral center-edge angle. Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Volume 00, Number 00, ’’ 2015
FAI Morphology in Asymptomatic Adolescents
TABLE 1. Mean a-Angles for Males and Females by Laterality Mean a-Angle (deg.) 95% Confidence Interval
Sex Males Right (hips = 276) Left (hips = 276) Females Right (hips = 282) Left (hips = 282)
49.9 49.7
49.3-50.5 49.0-50.5
46.1 46.1
45.4-46.7 45.4-46.7
between males and females. In addition, 4 models were conducted using logistic regression to identify predictive determinants of a-angle and LCEA. Two models examined the predictive effect of sex and age on a-angle and LCEA. The final 2 models examined the effect of age on a-angle and LCEA stratified by sex. SPSS v. 22.0 statistical package (IBM Corp., Armonk, NY) was used for all analyses and significance was set at P = 0.05. FIGURE 3. The percentage distribution of a-angles in males and females. The 95% confidence intervals are shown by the error bars.
RESULTS We included a total of 558 subjects (1116 hips). There were 276 males (49.5%) and 282 females (50.5%). The average age was 14.4 years (range, 10.0 to 18.2 y). The mean a-angle for the study group was 47.9 degrees (range, 25.7 to 78 degrees) and the mean LCEA was 34.4 degrees (range, 3.9 to 58.6 degrees). Mean a-angles and LCEA for males and females are presented in Tables 1 and 2. Males had a significantly higher mean a-angle (49.7 vs. 46.0 degrees) (P < 0.0005) and females had a significantly higher mean LCEA (35.7 vs. 33.0 degrees) (P < 0.0005). Ninety-four adolescents (16.8%) in the study population had an a-angle Z55 degrees (11.6% unilateral, 5.2% bilateral). Cam morphology was significantly more common in males (23.9%, 66 of 276) than in females (9.9%, 28 of 282) (P < 0.001, OR = 2.85, RR = 1.55). Unilateral cam morphology was found in 44 males (15.9%) and 21 females (7.4%). Bilateral cam morphology was noted in 29 males (8.0%) and 7 females (2.5%). Age and a-angles were similar between males and females in the cam group. The percentage distribution of a-angles for males and females is shown in Figure 3. A total of 181 adolescents (32.4%) had a LCEAZ40 degrees (21.5% unilateral, 10.9% bilateral). Pincer morphology was more common in females (35.1%, 99 of 282) than in males (29.7%, 82 of 276), but this was not statistically significant (P = 0.17). Unilateral pincer morphology was observed in 58 males (21.0%) and 62 females (22.0%). Bilateral pincer morphology was found
in 24 males (8.7%) and 37 females (13.1%). There was no significant difference in age and LCEA between males and females in the pincer group. Figure 4 shows the percentage distribution of LCEA for males and females. Thirty-four adolescents (6.1%) had mixed morphologies. Mixed morphologies were found in 21 males (7.6%) and 13 females (4.6%) (P = 0.19). Unilateral cam and pincer morphologies were seen in 14 males (5.1%) and 8 females (2.8%). Unilateral cam and contralateral pincer morphologies were noted in 6 males (2.2%) and 4 females (1.4%). Bilateral cam and pincer morphologies were observed in 1 male (0.4%) and 1 female (0.4%). Age, a-angles, and LCEA were similar between males and females in the mixed morphology group. Table 3 and Figure 5 present the frequency of cam and pincer morphologies by age and sex. The prevalence of a-angles Z55 degrees remained stable in males and females throughout adolescence. The prevalence of
TABLE 2. Mean Lateral Center-Edge Angles (LCEA) for Males and Females by Laterality Sex
Mean LCEA (deg.) 95% Confidence Interval
Males Right (hips = 276) Left (hips = 276) Females Right (hips = 282) Left (hips = 282)
Copyright
r
32.4 33.6
31.5-33.4 32.7-34.5
35.1 36.2
34.4-35.8 35.4-36.9
2015 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 4. The percentage distribution of lateral center-edge angles in males and females. The 95% confidence intervals are shown by the error bars. www.pedorthopaedics.com |
3
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Li et al
Volume 00, Number 00, ’’ 2015
TABLE 3. Prevalence of Abnormal a-Angles and Lateral Center-Edge Angles (LCEA) by Age and Sex n (%) Hips With a-Angle Z55 Degrees
Hips (n) Male
Female
Male
10.0-10.9 11.0-11.9 12.0-12.9 13.0-13.9 14.0-14.9 15.0-15.9 16.0-16.9 17.0-17.9 18.0-18.9
Age Range (y)
28 40 26 45 23 39 45 29 1
24 16 19 22 44 54 49 51 3
9 (32.1) 8 (20.0) 6 (23.1) 10 (22.2) 6 (26.1) 11(28.2) 8 (17.8) 8 (27.6) 0 (0)
10.0-18.9
276
282
66 (23.9)
LCEAZ40 degrees increased significantly with increased age in males (P < 0.001; OR = 1.30; CI, 1.19-1.42) but remained stable in females.
DISCUSSION Murray23 first described the tilt deformity as an abnormal relationship between the femoral head and neck that was a likely etiology for osteoarthritis of the hip. Nearly 4 decades later, Ganz and colleagues coined the term “femoroacetabular impingement” based on their inspection of chondrolabral damage patterns during surgical dislocation of the hip. These authors classified FAI into cam and pincer types based on the location of the abnormal morphology.2 Subsequently, multiple studies have examined the prevalence of FAI in asymptomatic adults.4–6,24–27 Hack and colleagues performed magnetic resonance imaging (MRI) evaluations of 200 adult volunteers and found cam morphology in 14% of the study group. Cam morphology was more common in men, with 24.7% of males and 5.4% of females demonstrating elevated a-angles.4 Similarly, the Copenhagen Osteoarthritis Study reported that 17% of male and 4% of female adults had cam morphology on anteroposterior (AP) pelvis xrays.26 Chakraverty et al25 found that 66% of asymptomatic adults demonstrated at least 1 abnormal parameter associated with cam-type or pincer-type FAI on CT evaluation. Few studies have examined the prevalence of FAI in asymptomatic pediatric patients.7–9 Monazzam and colleagues reported cam morphology in 10.2% of males and 2.5% of females on CT evaluation. Cam and pincer morphologies were seen in children as early as 10 and 12 years of age, respectively. Males were over 4 times more likely to have an a-angle Z55 degrees.7 Schmitz and colleagues compared AP pelvic radiographs made with EOS imaging in asymptomatic adolescents with and without scoliosis. The authors found that 92.8% of the study group demonstrated at least 1 parameter suggesting impingement morphology. An abnormal AP a-angle was noted in 5.6% of males and 6.7% of females, and was significantly more common in the adolescents without scoliosis.8 Carsen and colleagues reported cam morpho-
4 | www.pedorthopaedics.com
Female 4 1 1 2 2 8 3 7 0
(16.7) (6.3) (5.3) (9.1) (4.5) (14.8) (6.1) (13.7) (0)
28 (9.9)
Hips With LCEAZ40 Degrees Male 1 2 1 12 10 16 19 21 0
(3.6) (5.0) (3.8) (26.7) (43.5) (41.0) (42.2) (72.4) (0)
82 (29.7)
Female 7 6 8 4 11 18 18 25 2
(29.2) (37.5) (42.1) (18.2) (25.0) (33.3) (36.7) (49.0) (66.7)
99 (35.1)
logy exclusively in adolescents with closed physes. None of the subjects in their prephyseal closure group had elevated a-angles on MRI, whereas 14% of their closed physeal group had elevated a-angles and all were male.9 Our study is the largest published series to date on the prevalence of FAI morphology in asymptomatic adolescents. We found a 16.8% overall prevalence of cam-type FAI morphology and this was nearly 3 times more common in males. These results are comparable with previous reports on asymptomatic adolescents and adults.4–9,24–27 We noted a higher prevalence of cam morphology than Monazzam et al7 and Schmitz et al.8 This may be secondary to the use of different measurement techniques for the a-angle. We measured the a-angle on radial reformatted images. Monazzam et al7 measured the a-angle on an axial oblique CT image and Schmitz et al8 measured the a-angle on an AP pelvic radiograph. Cam morphology is most commonly found at the anterosuperior aspect of the femoral head. Rakhra et al20 showed that axial oblique imaging missed a substantial percentage of cam deformities that were detected on radial plane imaging as the axial oblique image can only detect cam lesions that are at the anterior aspect of the femoral head. Likewise, the AP a-angle can only detect a cam deformity that is at the superior aspect of the femoral head. Similar to Monazzam et al’s7 findings, we observed cam morphology in children as young as 10 years. These results are in contrast to Carsen et al’s9 study, in which cam lesions were only noted in adolescents with closed physes. The prevalence of cam morphology remained stable throughout adolescence in our study population. The appropriate threshold for the determination of an abnormal a-angle is still controversial. Although some prevalence studies have defined cam morphology as an a-angle Z50.5 degrees,4,9 several authors have shown that this likely yields many false-positive results.28,29 We chose to use an aangle cutoff Z55 degrees based on Notzli et al’s21 original description of the a-angle in symptomatic adults. This threshold seems to be the most widely used in the literature.7,13,14,17,20,25 Some authors have suggested even higher aangle thresholds5,26,29,30 and different cutoffs based on sex.4,26 One third of our study population had a LCEAZ40 degrees, which is higher than the prevalence in symptom-free Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Volume 00, Number 00, ’’ 2015
FAI Morphology in Asymptomatic Adolescents
FIGURE 5. Frequency of abnormal parameters associated with femoroacetabular impingement by age among (A) males and (B) females.
adolescents reported by Monazzam et al7 and Schmitz et al.8 Fewer studies have examined the prevalence of pincer FAI in asymptomatic adults.24,25,27 Chakraverty et al25 observed at least 1 pincer-type characteristic in 36.7% of men and 42.5% of women. Pincer morphology was more common in our female subjects as well (35.1% vs. 29.7%), but this was not statistically significant. We observed a significant increase in prevalence of pincer morphology in males with increased age. Monazzam et al7 noted a similar trend in their study, in which a LCEAZ40 degrees was found in 4.8% of males 12 to 13 years of age and 37.5% of males 16 to 19 years of age. We agree with these authors that progressive ossification of the acetabulum with increasing age may explain the increase in LCEA. Cam and pincer morphologies commonly coexist.25,27 We noted mixed morphologies in 6.1% of our subjects. The pathogenesis of FAI is still unknown. The prevalence of hip osteoarthritis has been reported to be 3 to 8.5 times higher in athletes than in nonathletes.31–33 Male athletes, especially those involved in running and jumping sports, have been found to develop osteoarthritis of the hip at an earlier age.31–37 Murray and Duncan36 noted an increased prevalence of the tilt deformity of the proximal femur and increased hip pain in adolescents engaged in a higher level of athletic activity. Several recent studies on elite male adolescent athletes involved in basketball, soccer, and ice hockey have demonstrated increased prevalence of cam-type FAI compared with controls, supporting a developmental etiology for the deformity.12–15,17 Agricola and colleagues followed 63 preprofessional male soccer players during adolescence and reported a significant increase in the prevalence of cam morphology over time, particularly in the boys with an open proximal femoral physis at baseline. After physeal closure, the overall prevalence and severity of the cam deformity remained stable.15 Siebenrock et al14 and Philippon et al13 also found a significant correlation between increased age and increased a-angles in male adolescents participating in high-impact sports. One possible explanation is that repetitive high stresses on the proximal femoral physis result in growth modulation and development of the cam deformity, similar to the pathologic skeletal growth alterations in gymnasts and baseball players.14 This theory is Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
supported by a study by Carter et al,16 who observed that the cam lesion occurs in close proximity to the proximal femoral physis in skeletally immature patients with symptomatic FAI. Similarly, Siebenrock et al18 reported increased lateral extension of the proximal femoral epiphysis in male adults with symptomatic cam-type FAI. There are several limitations to our study, mostly related to its retrospective design. Although we reviewed all of the subjects’ medical records to ensure that patients with hip pain, hip pathology, or any other condition that could be associated with hip problems were excluded, patients who had hip complaints that were not documented may have been inadvertently included. We were unable to interview patients regarding their activity level, such as participation in high-intensity sports. We also could not examine patients’ hip range of motion and perform an impingement test. We have no follow-up on these patients so we do not know if any of them developed hip complaints since their CT scan. Although there are many radiographic measurements that define FAI morphology, we only measured the a-angle and LCEA. We chose to use these 2 measurements in our study because the a-angle and LCEA are the most commonly used measurements in clinical practice to evaluate for cam and pincer morphology, respectively. A portion of the proximal femur and acetabulum is unossified in skeletally immature individuals, which cannot be evaluated on a CT scan. A similar MRI study would provide better visualization of the anatomy of the developing hip joint. However, it would be difficult to perform a prevalence study with a large study population that would satisfy our exclusion criteria as a MRI of the pelvis is not a commonly obtained study in asymptomatic adolescents. Lastly, FAI is a dynamic condition and should not be diagnosed solely on static radiographic imaging studies. In conclusion, our study demonstrates that the prevalence of cam-type FAI morphology in asymptomatic adolescents is similar to the reported prevalence in asymptomatic adults. Pincer morphology may be more common than cam morphology in adolescents. Cam www.pedorthopaedics.com |
5
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
J Pediatr Orthop
Li et al
morphology is more prevalent in males, whereas pincer and mixed morphologies are equally common in both sexes. The prevalence of cam morphology remained stable, whereas the prevalence of pincer morphology increased throughout adolescence in males. Our findings support a developmental etiology for FAI. Further studies are necessary to examine the prevalence of FAI morphology in younger children with long-term followup to determine which patients become symptomatic. REFERENCES 1. Beck M, Kalhor M, Leunig M, et al. Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br. 2005;87:1012–1018. 2. Ganz R, Parvizi J, Beck M, et al. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003; 417:112–120. 3. Clohisy JC, Knaus ER, Hunt DM, et al. Clinical presentation of patients with symptomatic anterior hip impingement. Clin Orthop Relat Res. 2009;467:638–644. 4. Hack K, Di Primio G, Rakhra K, et al. Prevalence of cam-type femoroacetabular impingement morphology in asymptomatic volunteers. J Bone Joint Surg Am. 2010;92:2436–2444. 5. Jung KA, Restrepo C, Hellman M, et al. The prevalence of cam-type femoroacetabular deformity in asymptomatic adults. J Bone Joint Surg Br. 2011;93:1303–1307. 6. Reichenbach S, Juni P, Werlen S, et al. Prevalence of cam-type deformity on hip magnetic resonance imaging in young males: a cross-sectional study. Arthritis Care Res (Hoboken). 2010;62: 1319–1327. 7. Monazzam S, Bomar JD, Dwek JR, et al. Development and prevalence of femoroacetabular impingement-associated morphology in a paediatric and adolescent population: a CT study of 225 patients. Bone Joint J. 2013;95-B:598–604. 8. Schmitz MR, Bittersohl B, Zaps D, et al. Spectrum of radiographic femoroacetabular impingement morphology in adolescents and young adults: an EOS-based double-cohort study. J Bone Joint Surg Am. 2013;95:e90. 9. Carsen S, Moroz PJ, Rakhra K, et al. The Otto Aufranc Award. On the etiology of the cam deformity: a cross-sectional pediatric MRI study. Clin Orthop Relat Res. 2014;472:430–436. 10. Leunig M, Casillas MM, Hamlet M, et al. Slipped capital femoral epiphysis: early mechanical damage to the acetabular cartilage by a prominent femoral metaphysis. Acta Orthop Scand. 2000;71:370–375. 11. Tannast M, Hanke M, Ecker TM, et al. LCPD: reduced range of motion resulting from extra- and intraarticular impingement. Clin Orthop Relat Res. 2012;470:2431–2440. 12. Agricola R, Bessems JH, Ginai AZ, et al. The development of Camtype deformity in adolescent and young male soccer players. Am J Sports Med. 2012;40:1099–1106. 13. Philippon MJ, Ho CP, Briggs KK, et al. Prevalence of increased alpha angles as a measure of cam-type femoroacetabular impingement in youth ice hockey players. Am J Sports Med. 2013;41: 1357–1362. 14. Siebenrock KA, Ferner F, Noble PC, et al. The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity. Clin Orthop Relat Res. 2011;469:3229–3240. 15. Agricola R, Heijboer MP, Ginai AZ, et al. A cam deformity is gradually acquired during skeletal maturation in adolescent and young male soccer players: a prospective study with minimum 2-year follow-up. Am J Sports Med. 2014;42:798–806. 16. Carter CW, Bixby S, Yen YM, et al. The relationship between cam lesion and physis in skeletally immature patients. J Pediatr Orthop. 2014;34:579–584.
6 | www.pedorthopaedics.com
Volume 00, Number 00, ’’ 2015
17. Siebenrock KA, Behning A, Mamisch TC, et al. Growth plate alteration precedes cam-type deformity in elite basketball players. Clin Orthop Relat Res. 2013;471:1084–1091. 18. Siebenrock KA, Wahab KH, Werlen S, et al. Abnormal extension of the femoral head epiphysis as a cause of cam impingement. Clin Orthop Relat Res. 2004;(418):54–60. 19. Pfirrmann CW, Mengiardi B, Dora C, et al. Cam and pincer femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients. Radiology. 2006;240:778–785. 20. Rakhra KS, Sheikh AM, Allen D, et al. Comparison of MRI alpha angle measurement planes in femoroacetabular impingement. Clin Orthop Relat Res. 2009;467:660–665. 21. Notzli HP, Wyss TF, Stoecklin CH, et al. The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement. J Bone Joint Surg Br. 2002;84:556–560. 22. Tonnis D, Heinecke A. Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 1999;81:1747–1770. 23. Murray RO. The aetiology of primary osteoarthritis of the hip. Br J Radiol. 1965;38:810–824. 24. Leunig M, Juni P, Werlen S, et al. Prevalence of cam and pincer-type deformities on hip MRI in an asymptomatic young Swiss female population: a cross-sectional study. Osteoarthritis Cartilage. 2013;21:544–550. 25. Chakraverty JK, Sullivan C, Gan C, et al. Cam and pincer femoroacetabular impingement: CT findings of features resembling femoroacetabular impingement in a young population without symptoms. AJR Am J Roentgenol. 2013;200:389–395. 26. Gosvig KK, Jacobsen S, Sonne-Holm S, et al. The prevalence of cam-type deformity of the hip joint: a survey of 4151 subjects of the Copenhagen Osteoarthritis Study. Acta Radiol. 2008;49:436–441. 27. Laborie LB, Lehmann TG, Engesaeter IO, et al. Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 2011;260:494–502. 28. Bixby SD, Kienle KP, Nasreddine A, et al. Reference values for proximal femoral anatomy in adolescents based on sex, physis, and imaging plane. Am J Sports Med. 2013;41:2074–2082. 29. Sutter R, Dietrich TJ, Zingg PO, et al. How useful is the alpha angle for discriminating between symptomatic patients with cam-type femoroacetabular impingement and asymptomatic volunteers? Radiology. 2012; 264:514–521. 30. Pollard TC, Villar RN, Norton MR, et al. Femoroacetabular impingement and classification of the cam deformity: the reference interval in normal hips. Acta Orthop. 2010;81:134–141. 31. L’Hermette M, Polle G, Tourny-Chollet C, et al. Hip passive range of motion and frequency of radiographic hip osteoarthritis in former elite handball players. Br J Sports Med. 2006;40:45–49. discussion 45-49. 32. Lindberg H, Roos H, Gardsell P. Prevalence of coxarthrosis in former soccer players. 286 players compared with matched controls. Acta Orthop Scand. 1993;64:165–167. 33. Vingard E, Alfredsson L, Goldie I, et al. Sports and osteoarthrosis of the hip. An epidemiologic study. Am J Sports Med. 1993;21: 195–200. 34. Drawer S, Fuller CW. Propensity for osteoarthritis and lower limb joint pain in retired professional soccer players. Br J Sports Med. 2001;35:402–408. 35. Kettunen JA, Kujala UM, Raty H, et al. Factors associated with hip joint rotation in former elite athletes. Br J Sports Med. 2000;34: 44–48. 36. Murray RO, Duncan C. Athletic activity in adolescence as an etiological factor in degenerative hip disease. J Bone Joint Surg Br. 1971;53:406–419. 37. Vingard E, Alfredsson L, Malchau H. Osteoarthrosis of the hip in women and its relationship to physical load from sports activities. Am J Sports Med. 1998;26:78–82.
Copyright
r
2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
