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. 2023 Jun 14;5(4):100742. doi: 10.1016/j.asmr.2023.04.025

Acetabular Rim Ossification Variants Are Found in Almost 20% of Patients Presenting With Hip Pain

Marc R Safran a, Adam J Money b,∗, Zach D Vaughn a, David A Brcka c, Rebecca Stone McGaver d, M Russell Giveans d, Christopher N Anderson e, Guillaume D Dumont f, Christopher M Larson d
PMCID: PMC10461137  PMID: 37645395

Abstract

Purpose

To determine the prevalence of 4 different types of acetabular rim ossifications, including partial labral ossification or punctate calcification, true os acetabuli, acetabular rim stress fracture, and complete labral ossification, and to determine whether different types of periacetabular ossifications are linked to demographic or radiological factors.

Methods

We retrospectively reviewed the medial records of patients presenting for hip-related complaints at 2 sports medicine practices from September 2007 to December 2009. An anteroposterior radiograph of both hips and a lateral radiograph of each hip was obtained for all patients and reviewed for findings of cam and pincer femoroacetabular impingement, degenerative changes (Tönnis grade), and periacetabular calcifications for both hips. These parameters were also evaluated with respect to symptoms, sex, and age.

Results

Four hundred ninety-one consecutive patients (982 hips) presented to 2 orthopaedic surgeons at 2 centers for “hip”-related complaints. There were 223 males and 268 females (age 39 ± 14 years). The overall prevalence of periacetabular calcifications in hips was 17.6%, with 56.6% of calcifications in the symptomatic hip and 43.4% in the contralateral hip. Four basic patterns of calcification were identified: punctuate calcifications within the labrum (8.0% hips), large rounded calcifications (os acetabuli) (4.2% hip), large fragments with a vertical line of the superior-lateral acetabular rim, consistent with healed or non-healed stress fracture (2.0% hips), and complete ossification of the labrum (3.4% hips). Overall, male sex (P = .002), increased lateral center-edge angle (P = .046), and higher Tönnis grade (P < .001) statistically predicted the presence of periacetabular ossification. Punctate calcifications were more prevalent in males (P = .002). Higher Tönnis grade (P = .029) and increased alpha angle (P = .046) were more prevalent with os acetabuli. Younger age (P = .001), male sex (P = .048), increased alpha angle (P = .012), and increased lateral center-edge angle (P < .001) were more prevalent in acetabular rim fractures. No factors were statistically significant at predicting the presence of an ossified labrum.

Conclusions

Periacetabular calcifications are not uncommon. Four particular patterns of calcification are identified: punctate labral calcifications (8%), larger rounded calcifications (i.e., os acetabuli) (4.2%), acetabular rim stress fractures (2%), and complete ossification of the labrum (3.4%) for a combined prevalence of 17.6% in patients presenting to an orthopaedic surgeon with “hip”-related complaints. Nearly half were in the asymptomatic hip. Male sex had a higher prevalence of periacetabular calcifications. An increased lateral center edge angle and higher Tönnis grade also had a higher prevalence of periacetabular calcifications. Younger male patients are more likely to have acetabular rim stress fractures. Patients with an increased alpha angle have a higher prevalence of os acetabuli and rim stress fractures.

Clinical Relevance

This study aims to identify, quantify, and categorize periacetabular calcifications about the hip. Their clinical relationships and relevance have been discussed, but no study has distinctly categorized the various types and their prevalence. This study provides a framework for identification and categorization.

The presence of ossifications adjacent to the acetabular rim have been recognized since the early eighteenth century. Several distinct forms of these ossifications have been described in the literature, including acetabular rim stress fractures, bone apposition of the acetabular rim, labral ossification, and persistence of secondary ossification centers of the acetabulum.1, 2, 3, 4, 5, 6, 7, 8, 9 Although their origin is not entirely certain, they have been linked to trauma, hip dysplasia, and, most commonly, femoroacetabular impingement (FAI).1,3, 4, 5, 6,9, 10, 11, 12

FAI is a common cause of hip pain and pathology that results from abnormal contact between the proximal femur and the acetabular rim during terminal range-of-motion.13,14 The 2 most common osseous abnormalities that lead to FAI are a loss of the normal femoral head-neck offset—resulting in cam impingement—and acetabular over coverage—resulting in pincer impingement.10,14,15 A third type of FAI has components of both cam and pincer and is referred to as mixed or combined impingement.10,14 Repetitive abutment of a morphologically abnormal proximal femur or acetabulum may potentially induce heterotopic bone formation between the native acetabular rim and labrum or within the labral substance.1,9,14 These abnormal forces can also produce rim stresses that either (1) outpace the remodeling capacity of acetabular bone, resulting in a rim stress fracture, or (2) prevent the fusion of secondary ossification centers, resulting in a residual bony nucleus.5,6,12

The reported radiographic prevalence of acetabular rim ossicles ranges from 4% to 41% in patients with symptomatic FAI and 7% to 13% in asymptomatic volunteers.6,16, 17, 18, 19, 20, 21, 22 Radiographically, these distinct types of acetabular rim ossicles are oftentimes collectively referred to as “os acetabuli,” a term originally used to describe the secondary ossification center of the acetabulum.4,8,16,18,20,22, 23, 24 Because this collective term has been used to describe many types of ossifications, the true prevalence of each distinct form has been difficult to determine. The purposes of this study are to determine the prevalence of 4 different types of acetabular rim ossifications, including partial labral ossification or punctate calcification, true os acetabuli, acetabular rim stress fracture, and complete labral ossification, and to determine whether different types of periacetabular ossifications are linked to demographic or radiological factors. The authors hypothesize that periacetabular ossifications can be radiographically categorized into 4 distinct categories and demonstrate a higher prevalence in patients with increased lateral center edge angle and alpha angle.

Material and Methods

Patients

Institutional review board approval was obtained prior to data collection. We retrospectively reviewed the medial records of patients presenting to 2 orthopaedic surgeons (M.R.S. and C.M.L.) at 2 centers for “hip” related complaints from 2008 to 2009. The exclusion criteria were a history of previous hip surgery, patients without radiographs, or patients with bilateral hip complaints. Patients were not excluded on the basis of age. An anteroposterior radiograph of both hips and a lateral radiograph of each hip was obtained for all patients and reviewed for findings of cam and pincer FAI, as well as degenerative changes (Tönnis grade) and periacetabular calcifications for both hips. These parameters were also evaluated with respect to symptoms, sex, and age.

Radiographic Analysis

Anteroposterior (AP) and cross-table lateral radiographs were obtained in all patients and assessed by 2 fellowship-trained orthopaedic surgeons (Z.D.V. and D.A.B.) for the presence of radiodense nuclei of the acetabular rim, pincer and cam FAI, dysplasia, and degenerative changes. AP radiographs with excessive tilt or rotation were excluded from the final analysis of acetabular retroversion.25 Pelvic tilt was determined to be acceptable if the distance between the coccyx and pubic symphysis was 10 to 30 mm.26 Pelvic rotation was acceptable if the distance from the center sacral line to the center of the pubic symphysis was less than 16 mm.25 Cross-table lateral radiographs were acceptable if the anterior and posterior femoral head-neck junctions were clearly definable.27

Pincer impingement was assessed using AP pelvis radiographs and was defined as a lateral center edge angle >40°. A lateral center edge angle (CEA) of Wiberg was measured on all AP pelvis radiographs.28 Hip dysplasia was determined if the CEA was less than 25° on AP pelvis radiograph.26 The CEA was determined by drawing a line through the center of the femoral head, perpendicular to the transverse axis of the pelvis, then drawing a second line from the center of the femoral head to the superolateral point of the sclerotic weightbearing zone of the acetabulum.26

Cam impingement was confirmed if the alpha angle was greater than 50° on the cross-table lateral radiograph or by the presence of an osseous protrusion or loss of offset at the femoral head-neck junction on either the AP pelvis or cross-table lateral radiographs.10,13,29,30 The alpha angle was determined by first placing a best-fit circle around the perimeter of the femoral head. A line was then drawn from the center of the circle through the central portion of the long axis of the femoral neck. A second line was extended from center of the circle anteriorly to the first point where the femoral head-neck junction extends beyond the circle. Osteoarthritis was graded on AP pelvis radiographs according to the classification system described by Tönnis.31

Periacetabular rim ossifications were classified into 4 types based on radiographic appearance: (1) partial labral ossifications or punctate calcifications, noted by a small radiodense nucleus adjacent to the lateral edge of the acetabular sourcil (Fig 1)1,3,9; (2) true os acetabuli, indicated by large size, rounded shape, and oblique or horizontal radiolucent line relative to acetabular roof (Fig 2)6,8; (3) acetabular rim stress fractures, denoted by their large size and perpendicular fracture line relative to the acetabular roof (Fig 3)5,6,12; and (4) complete labral ossification, defined as circumferential ossification of the labrum that is contiguous with the lateral edge of the acetabular rim (Fig 4).7

Fig 1.

Fig 1

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Anteroposterior view of right hip demonstrates punctate calcification within the labrum (red circle).

Fig 2.

Fig 2

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Anteroposterior view of right hip demonstrates os acetabuli (red circle).

Fig 3.

Fig 3

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Anteroposterior view of right hip demonstrates a rim stress fracture (red circle).

Fig 4.

Fig 4

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Anteroposterior view of the right hip demonstrates complete ossification of the labrum (red circle).

Statistical Analysis

Multiple linear regression analysis was performed to identify which of the studied variables were predictive of the presence of any radiopaque density, rim fractures, os acetabuli, amorphous labral calcifications. Statistical analysis was performed using SPSS Statistics, (Version 27; Armonk, NY).

Results

Four hundred ninety-one consecutive patients (982 hips) presented to 2 orthopaedic surgeons at 2 centers for “hip”-related complaints. There were 223 males and 268 females (age 39 ± 14 years). The overall prevalence of periacetabular calcifications in hips was 17.6%, with 56.6% of calcifications in the symptomatic hip and 43.4% in the contralateral hip. Patients with bilateral hip pain were not included. Four basic patterns of calcification were identified: punctuate calcifications within the labrum (8.0% hips), large rounded calcifications (os acetabuli) (4.2% hip), large fragments with a vertical line of the superior-lateral acetabular rim, consistent with healed or non-healed stress fracture (2.0% hips), and complete ossification of the labrum (3.4% hips). Table 1 lists the prevalence, as well as the relationships to sex, bony morphology, and symptoms.

Table 1.

Prevalence of the Four Distinct Ossifications and Their Relationship to Sex, Bony Morphology, and Symptomatic Hip

Prevalence Male Female Cam (Alpha Angle >50°) Pincer (LCEA >40°) Symptomatic Hip
Punctate calcification 77 hips (8.0%) 49 hips (63.6%) 28 hips (36.4%) 79.2% 19.4% 58.4%
Os acetabuli 41 hips (4.2%) 25 hips (61%) 17 hips (39%) 90.2% 29.2% 53.7%
Rim fracture 20 hips (2.0%) 16 hips (80%) 4 hips (20%) 100% 50% 70%
Ossified labrum 33 hips (3.4%) 17 hips (51.5%) 16 hips (48.5%) 75.8% 33.3% 54.5%
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LCEA, lateral center-edge angle.

Multiple linear regression with age, sex, alpha angle, lateral center edge angle, Tönnis grade, and presence of symptoms as independent variables statistically significantly predicted the presence of any radiopaque density (F(6, 981) = 9.06, P < .001, R2 = 0.05). Adding to the analysis of male sex (P = .001), lateral center edge angle (P = .046), and Tönnis grade (P < .001) further improved the statistical significance to the prediction.

Furthermore, multiple linear regression with age, sex, alpha angle, lateral center edge angle, Tönnis grade, and presence of symptoms as independent variables statistically significantly predicted the presence of amorphous labral calcifications (F(6, 981) = 2.98, P = .007, R2 = 0.02). Sex (male) (P = .002) was the only variable to statistically significantly contribute to the model.

In evaluation of the presence of os acetabuli, multiple linear regression with age, sex, alpha angle, lateral center edge angle, Tönnis grade, and presence of symptoms as independent variables statistically significantly predicted their presence (F(6, 981) = 2.86, P = .009, R2 = 0.02). Further still, Tönnis grade (P = .029) and alpha angle (P = .046) added statistically significantly to the prediction.

Finally, when evaluating those at risk of acetabular rim fracture, multiple linear regression analysis with age, sex, alpha angle, lateral center edge angle, Tönnis grade, and presence of symptoms were individual variables that predicted the presence of an acetabular rim fracture (F(6, 981) = 7.97, P < .001, R2 = 0.05). Additionally, age (P = .001), male sex (P = .048), alpha angle (P = .012), lateral center edge angle (P < .001), and Tönnis grade (P = .034) further added statistically significantly to the prediction. Using multiple linear regression analysis evaluating age, sex, alpha angle, lateral center edge angle, Tönnis grade, and presence of symptoms as independent variables did not statistically significantly predict the presence of ossified labrum (P = .18).

Discussion

Overall, 17.6% of 982 hips had periarticular calcifications. Four distinct patterns of periacetabular calcifications were identified—punctate labral ossification (8%), os acetabuli (4.2%), rim stress fracture (2%) and complete labral ossification (3.4%). Overall, male sex (P = .002), increased lateral center edge angle (P = .046), and higher Tönnis grade (P < .001) statistically predicted the presence of a periacetabular ossification. Punctate calcifications were more prevalent in males (P = .002). Higher Tönnis grade (P = .029) and increased alpha angle (P = .046) were more prevalent in the os acetabuli. Younger age (P = .001), male sex (P = .048), increased alpha angle (P = .012), and increased lateral center edge angle (P < .001) were more prevalent in acetabular rim fractures. No factors were statistically significant at predicting the presence of an ossified labrum.

The authors suggest that the 4 types of periarticular calcifications are unique in appearance and location. In the authors’ experience, the os acetabuli is predominantly anterolateral and rounded in appearance. The punctate calcifications are just that—small, punctate, often multiple calcifications that can be anywhere. They may also represent calcified labra or chondrocalcinosis. Rim stress fractures are often centered slightly posterior of mid lateral acetabulum. These may be “hot” on bone scan (unpublished data) because they may represent an acute bony injury or healing. In the authors’ experience, the medial portion of the stress fracture fragment is a vertical line as opposed to the rounded os acetabuli. Also in the authors’ experience, the ossified labrum is often anterolateral and less rounded in appearance. It has no medial radiolucent line as opposed to the other 3 periarticular calcifications (Fig 1, Fig 2, Fig 3, Fig 4).

These data are similar to other recently published articles. Dumont et al.19 had a prevalence of 16.2% of “radiopaque densities” in patients undergoing surgical treatment for FAI. The “radiopaque densities” were most often visualized between the 12- and 3-o’clock positions on the acetabulum, and only 66.7% of them were visible on plain radiograph as compared to computed tomography. Interestingly, 15% of the patient’s with “radiopaque densities” on imaging did not have identifiable densities during surgery. They did not find any correlation to presence of “radiopaque densities” with age, sex, lateral central edge angle, or alpha angle, which differed from the current studies results.19 Register et al.21 found acetabular rim fractures in 11% of their patients with FAI, Clohisy et al.17 noted “labral ossification” in 7.5% of their patients undergoing FAI treatment, labral calcifications or os acetabuli were also found in 13% of asymptomatic individuals in the study by Cotten et al.,18 and Martinez et al.6 reported a much lower prevalence of only 3.6% of ossicles located at the acetabular rim in patients with FAI.8 These studies demonstrated a lower prevalence of calcific densities as compared to the current studies results.

The clinical relevance of periacetabular ossifications has been evaluated in the literature. Byrd et al.32 evaluated outcomes in patients undergoing hip arthroscopy in a cohort of patients with labral ossifications versus patients without labral ossification. They reported that patients with labral ossifications were often older and female, and, despite having similar improvements, patients with labral ossifications had overall lower preoperative and postoperative outcome scores.32 Giordano et al.33 reported a case-control series of patients treated for FAI and removal of an acetabular rim fragment. However, they noted no difference in outcome scores for patients with or without an acetabular rim fragment.33 Soriano et al.34 recently demonstrated that patients with FAI and labral calcifications have improved outcomes similar to patient without labral calcifications after excision. The role of periacetabular ossifications in the clinical evaluation and outcome in patients with FAI warrants further investigation.

Corten et al.1 defined a natural progression of rim ossification in patients with FAI. In a histologic study of 20 hips, they described that labral tissue displacement leads to appositional bone formation that is distinctly separate from osteophyte formation.1 Others have suggested that ossification about the acetabulum occurs as part of early osteoarthritis of the hip and leads to worse clinical pain and poorer hip function.35 Several studies evaluate the rectus insertion as a potential cause for os formation and pain within the joint.36, 37, 38 These lesions are often extra-articular on radiography, and the authors believe they represent a separate pathology than the topic discussed in this article. Further research is needed to determine whether periacetabular ossifications are an early sign of osteoarthritis in the patient with FAI.

Limitations

There are several limitations to our study. Patients were all evaluated with plain radiographs. The measurements and evaluation were performed by fellowship-trained senior surgeons, but the possibility of intraobserver and interobserver error is present. Advanced imaging such as 3-dimensional computed tomography scanning could further define the location and type of ossification, which was not used in our study. The patients’ data were collected in 2010, which may affect readings, interpretation, and reliability of the reported measurements in general. Patients with osteoarthritis have been shown to develop periacetabular calcifications, which may affect the rates of periacetabular ossifications.

Conclusion

Periacetabular calcifications are not uncommon. Four particular patterns of calcification are identified: punctate labral calcifications (8%), larger rounded calcifications (i.e., true os acetabuli) (4.2%), acetabular rim stress fractures (2%), and complete ossification of the labrum (3.4%) for a combined prevalence of 17.6% in patients presenting to an orthopaedic surgeon with “hip”-related complaints. Nearly half were in the asymptomatic hip. Male sex had a higher prevalence of periacetabular calcifications. An increased lateral center edge angle and higher Tönnis grade also had a higher prevalence of periacetabular calcifications. Younger male patients are more likely to have acetabular rim stress fractures. Patients with an increased alpha angle have a higher prevalence of os acetabuli and rim stress fractures.

Footnotes

The authors report the following potential conflict of interest or source of funding: C.N.A. reports personal fees from the American Journal of Sports Medicine and Depuy Synthes Mitek; and other from U.S. patent nos. 9,924,939 B1, 10,085,740 B1, 10,299,784 B2, 10,993,711 B2, 11,266,400, and 11,272,921 and Japanese patent nos. 6928987 and 7025062. M.R. reports personal fees from Smith & Nephew, DJO, and Responsive Arthroscopy; and grants from Smith & Nephew. Full ICMJE author disclosure forms are available for this article online, as supplementary material.

Supplementary Data

ICMJE author disclosure forms
mmc1.pdf (797.9KB, pdf)

References

  • 1.Corten K., Ganz R., Chosa E., Leunig M. Bone apposition of the acetabular rim in deep hips: A distinct finding of global pincer impingement. J Bone Joint Surg Am. 2011;93(Suppl 2):10–16. doi: 10.2106/JBJS.J.01799. [DOI] [PubMed] [Google Scholar]
  • 2.Epstein N.J. Stress fracture of the acetabular rim: Arthroscopic reduction and internal fixation a case report. J Bone Joint Surg Am. 2009;91:1480. doi: 10.2106/JBJS.H.01499. [DOI] [PubMed] [Google Scholar]
  • 3.Ito K., Leunig M., Ganz R. Histopathologic features of the acetabular labrum in femoroacetabular impingement. Clin Orthop Relat Res. 2004;429(429):262–271. doi: 10.1097/01.blo.0000144861.11193.17. [DOI] [PubMed] [Google Scholar]
  • 4.Klaue K., Durnin C.W., Ganz R. The acetabular rim syndrome. A clinical presentation of dysplasia of the hip. J Bone Joint Surg Br. 1991;73:423–429. doi: 10.1302/0301-620X.73B3.1670443. [DOI] [PubMed] [Google Scholar]
  • 5.Larson C.M., Stone R.M. The rarely encountered rim fracture that contributes to both femoroacetabular impingement and hip stability: A report of 2 cases of arthroscopic partial excision and internal fixation. Arthroscopy. 2011;27:1018–1022. doi: 10.1016/j.arthro.2011.04.006. [DOI] [PubMed] [Google Scholar]
  • 6.Martinez A.E., Li S.M., Ganz R., Beck M. Os acetabuli in femoro-acetabular impingement: Atress fracture or unfused secondary ossification centre of the acetabular rim? Hip Int. 2006;16:281–286. doi: 10.1177/112070000601600407. [DOI] [PubMed] [Google Scholar]
  • 7.Ninomiya S., Shimabukuro A., Tanabe T., Kim Y.T., Tachibana Y. Ossification of the acetabular labrum. J Orthop Sci. 2000;5:511–514. doi: 10.1007/s007760070031. [DOI] [PubMed] [Google Scholar]
  • 8.Ponseti I.V. Growth and development of the acetabulum in the normal child. Anatomical, histological, and roentgenographic studies. J Bone Joint Surg Am. 1978;60:575–585. [PubMed] [Google Scholar]
  • 9.Seldes R.M., Tan V., Hunt J., et al. Anatomy, histologic features, and vascularity of the adult acetabular labrum. Clin Orthop Relat Res. 2001;(382):232–240. doi: 10.1097/00003086-200101000-00031. [DOI] [PubMed] [Google Scholar]
  • 10.Beck M., Kalhor M., Leunig M., Ganz R. 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. doi: 10.1302/0301-620X.87B7.15203. [DOI] [PubMed] [Google Scholar]
  • 11.Caudle R.J., Crawford A.H. Avulsion fracture of the lateral acetabular margin. A case report. J Bone Joint Surg Am. 1988;70:1568–1570. [PubMed] [Google Scholar]
  • 12.Epstein N.J., Safran M.R. Stress fracture of the acetabular rim: Rrthroscopic reduction and internal fixation. A case report. J Bone Joint Surg Am. 2009;91:1480–1486. doi: 10.2106/JBJS.H.01499. [DOI] [PubMed] [Google Scholar]
  • 13.Beck M., Leunig M., Parvizi J., et al. Anterior femoroacetabular impingement: Part II. Midterm results of surgical treatment. Clin Orthop Relat Res. 2004;418(418):67–73. [PubMed] [Google Scholar]
  • 14.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. doi: 10.1097/01.blo.0000096804.78689.c2. [DOI] [PubMed] [Google Scholar]
  • 15.Ito K., Minka M.A., 2nd, Leunig M., Werlen S., Ganz R. Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br. 2001;83:171–176. doi: 10.1302/0301-620x.83b2.11092. [DOI] [PubMed] [Google Scholar]
  • 16.Brunner A., Horisberger M., Herzog R.F. Sports and recreation activity of patients with femoroacetabular impingement before and after arthroscopic osteoplasty. Am J Sports Med. 2009;37:917–922. doi: 10.1177/0363546508330144. [DOI] [PubMed] [Google Scholar]
  • 17.Clohisy J.C., Baca G., Beaule P.E., et al. Descriptive epidemiology of femoroacetabular impingement: A North American cohort of patients undergoing surgery. Am J Sports Med. 2013;41:1348–1356. doi: 10.1177/0363546513488861. [DOI] [PubMed] [Google Scholar]
  • 18.Cotten A., Boutry N., Demondion X., et al. Acetabular labrum: MRI in asymptomatic volunteers. J Comput Assist Tomogr. 1998;22:1–7. doi: 10.1097/00004728-199801000-00001. [DOI] [PubMed] [Google Scholar]
  • 19.Dumont G.D., Menge T.J., Money A.J., Carmon P. Para-acetabular radiopaque densities in patients with femoroacetabular impingement: A retrospective assessment of prevalence and characteristics. Orthop J Sports Med. 2020;8(1) doi: 10.1177/2325967119892330. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Kassarjian A., Yoon L.S., Belzile E., et al. Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology. 2005;236:588–592. doi: 10.1148/radiol.2362041987. [DOI] [PubMed] [Google Scholar]
  • 21.Register B., Pennock A.T., Ho C.P., et al. Prevalence of abnormal hip findings in asymptomatic participants: a prospective, blinded study. Am J Sports Med. 2012;40:2720–2724. doi: 10.1177/0363546512462124. [DOI] [PubMed] [Google Scholar]
  • 22.Singh P.J., O'Donnell J.M. The outcome of hip arthroscopy in Australian football league players: A review of 27 hips. Arthroscopy. 2010;26:743–749. doi: 10.1016/j.arthro.2009.10.010. [DOI] [PubMed] [Google Scholar]
  • 23.Pfirrmann C.W.A., Mengiardi B., Dora C., et al. Cam and pincer femoroacetabular impingement: Characteristic MR arthrographic findings in 50 patients. Radiology. 2006;240:778–785. doi: 10.1148/radiol.2403050767. [DOI] [PubMed] [Google Scholar]
  • 24.Plötz G.M.J., Prymka M., Knoch von M., et al. Spontaneous fusion of “os acetabuli” after triple pelvic osteotomy. Arch Orthop Trauma Surg. 2002;122(9-10):526–529. doi: 10.1007/s00402-002-0431-6. [DOI] [PubMed] [Google Scholar]
  • 25.Siebenrock K.A., Kalbermatten D.F., Ganz R. Effect of pelvic tilt on acetabular retroversion: A study of pelves from cadavers. Clin Orthop Relat Res. 2003;407(407):241–248. doi: 10.1097/00003086-200302000-00033. [DOI] [PubMed] [Google Scholar]
  • 26.Clohisy J.C. A Systematic Approach to the Plain Radiographic Evaluation of the Young Adult Hip. J Bone Joint Surg Am. 2008;90(Suppl 4):47. doi: 10.2106/JBJS.H.00756. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Gerhardt M.B., Romero A.A., Silvers H.J., et al. The prevalence of radiographic hip abnormalities in elite soccer players. Am J Sports Med. 2012;40:584–588. doi: 10.1177/0363546511432711. [DOI] [PubMed] [Google Scholar]
  • 28.Wiberg G. Studies on dysplastic acetabula and congenital subluxation of the hip joint. Acta Chir Scand. 1939;58:5–135. [Google Scholar]
  • 29.Gosvig K.K., Jacobsen S., Palm H., Sonne-Holm S., Magnusson E. A new radiological index for assessing asphericity of the femoral head in cam impingement. J Bone Joint Surg Br. 2007;89:1309–1316. doi: 10.1302/0301-620X.89B10.19405. [DOI] [PubMed] [Google Scholar]
  • 30.Notzli H.P., Wyss T.F., Stoecklin C.H., 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. doi: 10.1302/0301-620x.84b4.12014. [DOI] [PubMed] [Google Scholar]
  • 31.Tönnis D. Normal values of the hip joint for the evaluation of X-rays in children and adults. Clin Orthop Relat Res. 1976;119:39–47. [PubMed] [Google Scholar]
  • 32.Byrd J.W., Jones K.S., Freeman C.R. Surgical outcome of pincer femoroacetabular impingement with and without labral ossification. Arthroscopy. 2016;32:1022–1029. doi: 10.1016/j.arthro.2015.12.042. [DOI] [PubMed] [Google Scholar]
  • 33.Giordano B.D.S.-A.C., Gui C., Darwish N., Lodhia P., Domb B.G. Clinical outcomes of patients with symptomatic acetabular rim fractures after arthroscopic FAI treatment. J Hip Preserv Surg. 2018;5:66–72. doi: 10.1093/jhps/hnx031. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Soriano K.K.J., Flores S.E., Aung M.S., Nguyen T.Q., Zhang A.L. Treatment of labral calcification in the setting of femoroacetabular impingement syndrome with arthroscopic calcification excision, labral repair, and osteoplasty improves outcomes. Arthroscopy. 2021;37:554–563. doi: 10.1016/j.arthro.2020.10.033. [DOI] [PubMed] [Google Scholar]
  • 35.Hubert J., Hawellek T., Moe M., et al. Labral calcification in end-stage osteoarthritis of the hip correlates with pain and clinical function. J Orthop Res. 2018;36:1248–1255. doi: 10.1002/jor.23736. [DOI] [PubMed] [Google Scholar]
  • 36.Kim Y.S., Lee H.M., Kim J.P. Acute calcific tendinitis of the rectus femoris associated with intraosseous involvement: A case report with serial CT and MRI findings. Eur J Orthop Surg Traumatol. 2013;23(Suppl 2):S233–S239. doi: 10.1007/s00590-012-1156-z. [DOI] [PubMed] [Google Scholar]
  • 37.Zini R., Panasci M., Papalia R., et al. Rectus femoris tendon calcification: Arthroscopic excision in 6 top amateur athletes. Orthop J Sports Med. 2014;2(12) doi: 10.1177/2325967114561585. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 38.Jimenez C.L., Beebe M.J., Maak T.G., Aoki S.K. Acute severe hip pain associated with labral calcific deposition disease. Orthopedics. 2014;37(12):e1137–e1140. doi: 10.3928/01477447-20141124-93. [DOI] [PubMed] [Google Scholar]

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