Prevalence and Locations of Acetabular Labral Sulcus in Patients Undergoing Arthroplasty for Hip Fracture

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1 Original Article With Video Illustration Prevalence and Locations of Acetabular Labral Sulcus in Patients Undergoing Arthroplasty for Hip Fracture Kyoung-Woon Kim, M.D., Ji-Hoon Baek, M.D., and Yong-Chan Ha, M.D. Purpose: This study was performed to determine the prevalence, type, and location of acetabular sulcus, which is known as a normal variant, by intraoperative observation in patients undergoing arthroplasty for a femoral neck or intertrochanteric fracture. Methods: The study enrolled 98 patients (98 hips) (mean patient age, 79.1 years; age range, 51 to 92 years) who underwent total hip arthroplasty or hemiarthroplasty because of a femoral neck or intertrochanteric fracture. All patients underwent an arthroscopic examination during surgery to determine the prevalence of acetabular labral tears or sulci. Acetabular labral lesions were classified by type and location. The accuracy of the anatomic analysis was assessed by determining intraobserver and interobserver reproducibilities in 20 patients. Results: A labral sulcus was present in 45 of 98 patients (46%), and 2 of these 45 had both anterosuperior and posteroinferior sulci. Of the 47 sulci, 18 were due to simple folding, 28 were due to incomplete separation, and 1 was due to complete separation. A labral tear was observed in 72 patients (73%), and 4 patients had 2 unassociated tears of different types. Of the 76 tears, 45 were of the longitudinal type. The most common location for labral sulci and tears was within the 12- to 3-o clock quadrant (48% and 68%, respectively). There were only a few sulci without labral tears in the 7- to 9-o clock region. Intraobserver and interobserver correlations were found to be reproducible and reliable. Conclusions: Labral sulci were relatively common in this study (46% of patients), and labral sulci and tears were most commonly found in the anterosuperior area. Therefore acetabular labral lesions in the anterosuperior area should be inspected closely to allow for differentiation between labral tears and labral sulci. Level of Evidence: Level IV, therapeutic case series. Acetabular labral tears are known to cause sharp groin pain and painful acetabular impingement. The most common cause of these tears is dysplasia of the hip, followed by lateral acetabular rim syndrome, trauma, and femoroacetabular impingement. 1,2 Furthermore, labral tears may lead to nonsymmetric force From the Department of Orthopaedic Surgery, Chung-Ang University College of Medicine, Seoul, South Korea. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received May 30, 2011; accepted March 14, Address correspondence to Yong-Chan Ha, M.D., Department of Orthopaedic Surgery, Chung-Ang University College of Medicine, Heukseok-dong, Dongjak-ku, Seoul , South Korea. hayongch@naver.com 2012 by the Arthroscopy Association of North America /11343/$ distributions on the acetabulum and femoral head, which implies that labral tears predispose patients to osteoarthritis of the hip joint. 3,4 Therefore the early diagnosis of labral tears might be important not only for symptom relief but also for altering the progression of osteoarthritis. During the diagnostic evaluation of a labral tear, an important potential pitfall is a labral sulcus, which is a normal anatomic variation. Treatment of the labral sulcus is usually not necessary. Saddik et al. 5 pointed out the importance of differential diagnosis in cases of labral lesions in the anterior quadrants of the acetabulum. Magnetic resonance arthrography (MRA) is considered the most accurate way of imaging labral abnormalities. 6-8 However, although MRA has shown high sensitivity and accuracy, 6,9-11 several MRA studies have raised the possibility of potential pitfalls in the diagnosis of acetabular labral abnormalities, such as sublabral sulci and a normal anatomic variation in the Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 28, No 10 (October), 2012: pp

2 1374 K-W. KIM ET AL. shape of normal sulci between labra and acetabular cartilage. 12 Recently, a few arthroscopic studies have reported prevalences and locations of sulci in patients with clinical suspicion of a labral tear and sought to provide magnetic resonance (MR) correlations. 5,13 These study designs have substantial advantages in terms of determining direct anatomic correlations. However, they also have several possible disadvantages. First, the studies were performed in symptomatic patients with mechanical symptoms and a clinical suspicion of a labral tear. Second, it is often difficult to record all portions of the labrum during arthroscopy. Third, the numbers of subjects examined arthroscopically were relatively small, and results of reported studies regarding the prevalence and location of sulci have been inconsistent. 5,8,13 Accordingly, we considered that a specialized study design was required to evaluate the prevalence and location of sulci using patients with hip fracture. The purpose of this prospective study was to determine the prevalence, type, and location of acetabular sulci by intraoperative observation in patients undergoing arthroplasty for a femoral neck or intertrochanteric fracture. Our hypothesis was that this anatomic study could provide more exact information regarding the prevalence and location of acetabular labral sulci using patients with hip fracture and contribute to minimize misinterpretation and overtreatment through differential diagnosis between labral tears and labral sulci. METHODS FIGURE 1. Device with a bar attached to a translucent hemisphere with clock-face gradations. The design and protocol of this prospective study were approved by the institutional review board of our hospital. All patients were informed that their medical data could be used in a scientific study and provided consent. The inclusion criteria were patients who had a diagnosis of displaced femoral neck fracture or comminuted and/or unstable intertrochanteric fracture and the mental ability to provide informed consent and cooperate. The exclusion criteria applied were severe degenerative arthritic change of the fractured hip joint, acetabular dysplasia, history of operative treatment of the hip joint, internal fixation for a hip fracture, and severely incapacitated patients. Between September 2009 and April 2011, 98 patients (98 hips) who underwent total hip arthroplasty or hemiarthroplasty because of a femoral neck or intertrochanteric fracture at our institution were enrolled. There were 29 men and 70 women with a mean age at operation of 79.1 years (range, 51 to 92 years). Surgical Approach and Arthroscopic Evaluation The operative procedure was performed through a standard posterior approach. All patients underwent an arthroscopic examination for acetabular labral abnormality during hip arthroplasty. First, gross observation was performed using a dental mirror. Second, a hip arthroscope was used for detailed and magnified examination of the labrum and recorded the entire arthroscopic evaluation procedure. Third, the location of any labral abnormality was recorded using the clock-face system with a specialized device that provided objective records of lesion locations (Fig 1). Anatomic Assessments of Labral Abnormalities and Locations A labral sulcus was defined as a smooth, welldefined cleft separating the hyaline cartilage and labrum without accompanying evidence of tissue trauma and with a normal, stable labral base in response to probing. 13 Labral tears were defined as abnormal displacement and laxity or friability in response to probing. 13 Lesion locations were described using a clock-face system, whereby 12 o clock pointed slightly posterior to the patient s head, 3 o clock was directed anteriorly (for both right and left hips), 6 o clock was directed toward the middle of the transverse ligament, and 9 o clock was directed posteriorly (for right and left hips). 14 To localize abnormalities with respect to the

3 ACETABULAR LABRAL SULCUS 1375 acetabulum, twelve 30 zones were used. When a labral lesion was located between the 11- and 2-o clock zones, we described it as 3 zones (11- to 12-o clock zone, 12- to 1-o clock zone, and 1- to 2-o clock zone). Labral sulci were classified into 3 types, using our own description: type 1 was defined as simple folding, type 2 was defined as incomplete separation with a cleft, and type 3 was defined as complete separation between the labrum and acetabular bone (Fig 2). Labral tears or detachments were classified as Lage type 1, 2, 3, or 4 15 (Fig 3). A type 1 tear (radial flap tear) was defined as having disruption of the free margin of the labrum with consequent formation of a discrete flap. A type 2 tear (radial fibrillated tear) was defined as having the appearance of a shaving brush. A type 3 tear (longitudinal peripheral tear) was defined as a tear of variable length along the acetabular insertion of the labrum. Finally, a type 4 tear (unstable tear) was defined based on abnormal labral function rather than shape. Statistical Analysis The reliability of the evaluation of the labral status (location and type of labral tear and sulcus) was assessed by determining the interobserver and intraobserver reproducibility in 20 patients. Evaluations of the labral status (location and type of labral tear and sulcus) during operative treatment were initially always made by the first examiner (Y-C.H., 7 years experience in arthroscopic surgery, with national certification). Next, a second examiner (K-W.K., 3 years experience in arthroscopic surgery, with national certification), previously informed about the nature of the study, took the same measurements in the same operative field with no knowledge of the previous results. Finally, the first examiner repeated the measurements using recorded video at 2 weeks postoperatively according to the criteria established earlier (Video 1, available at All measurements were independently recorded. We assessed the interobserver reliabilities with respect to diagnoses of a labral sulcus or tear and pathology locations using coefficients. Coefficients were interpreted as follows: less than 0.00, poor agreement; 0.00 to 0.20, slight agreement; 0.21 to 0.40, fair agreement; 0.41 to 0.60, moderate agreement; 0.61 to 0.80, substantial agreement; and greater than 0.80, almost perfect agreement. 16 FIGURE 2. Labral sulcus classification. (A) Type 1: a simple fold. (B) Type 2: incomplete separation with a cleft. (C) Type 3: complete separation between labrum and acetabulum.

4 1376 K-W. KIM ET AL. FIGURE 3. Labral tear classification. (A) Type 1: radial flap tear, with disruption of the free margin of the labrum with the consequent formation of a discrete flap, in the 1- to 2-o clock area (arrowhead). (B) Type 2: radial fibrillated tear, with a hairy appearance at the free margin of the labrum, in the 11- to 1-o clock area (arrowhead). (C) Type 3: longitudinal peripheral tear, along the acetabular insertion of the labrum, in the 12- to 3-o clock area (arrowhead). (D) Type 4: unstable tear, with subluxating labra, in the 1- to 3-o clock area (arrowhead). RESULTS Labral sulci were present in 45 of the 98 patients. Two of the 45 patients had both anterosuperior and posteroinferior sulci. Of the 47 sulci (47 of 98 hips [48%]), morphologically, 18 were type 1, 28 were type 2, and 1 was type 3 (Table 1). Sulci were located in 137 clock-face zones. Expressed as a percentage of all zones, 24 sulci (18%) were located in the 1- to 2-o clock zone, 21 (15%) in the 2- to 3-o clock zone, 21 (15%) in the 12- to 1-o clock zone, 16 (12%) in the 11- to 12-o clock zone, 15 (11%) in the 3- to 4-o clock zone, 11 (8%) in the 10- to 11-o clock zone, 10 (8%) in the 9- to 10-o clock zone, 9 (7%) in the 8- to 9-o clock zone, 6 (4%) in the 7- to 8-o clock zone, and 4 (3%) in the 4- to 5-o clock zone (Fig 4). Labral tears were present in 72 of 98 patients. Four of the 72 patients had 2 unconnected tears of different types. Of the 76 tears (76 of 98 hips [76%]), arthroscopically, 7 were Lage type 1, 18 were type 2, 45 were type 3, and 1 was type 4, whereas 5 lesions were combined type and included both type 3 and type 1 (Table 1). Labral tears were discovered in 170 clock zones. Tear frequencies were as follows: 50 (29%) in the 12- to 1-o clock zone, 36 (21%) in the 1- to 2-o clock zone, 28 (16%) in the 2- to 3-o clock zone, 25 (15%) in the 11- to 12-o clock zone, 11 (6%) in the 10- to 11-o clock zone, 10 (6%) in the 3- to 4-o clock zone, 9 (5%) in the 9- to 10-o clock zone, and 1 (1%) in the 4- to 5-o clock zone (Fig 5). Lesions with both labral sulci and labral tears were

5 ACETABULAR LABRAL SULCUS 1377 TABLE 1. Interobserver and Intraobserver Reliabilities of Labral Lesion Prevalences and Types (Determined on 2 Separate Occasions) No. (%) Interobserver Reproducibility Intraobserver Repeatability Labral sulcus Prevalence 47 of 98 (48%) Type of 47 (38%) 2 28 of 47 (60%) 3 1 of 47 (1%) Labral tear Prevalence 76 of 98 (78%) Type of 76 (9%) 2 18 of 76 (24%) 3 45 of 76 (59%) 4 1 of 76 (1%) of 76 (7%) FIGURE 5. Distribution of labral tears. found in 31 hips. Of these, 16 lesions were located on the anterosuperior quadrant (12- to 3-o clock zones). The most common location for labral sulci and tears was within the 12- to 3-o clock quadrant (48% and 68%, respectively). No labral abnormality was found in the 5- to 7-o clock regions, and only a few sulci were found in the 7- to 9-o clock regions (Fig 6). Intraobserver and interobserver agreements for the presence of a labral sulcus or a labral tear and for sulcus and tear type were found to be reproducible and reliable (Table 1). FIGURE 4. Distribution of labral sulci. DISCUSSION Although several studies of acetabular labral sulci have been performed using comparison between MRA and arthroscopic findings and cadaveric studies, they have several limitations, such as indirect examination, impairment of visualization, and inherent stiffness of labral structures. In contrast, our study design, using direct probing of the acetabular labrum without visual limitation, as well as arthroscopic visualization and records, could provide more exact information regarding the prevalence and location of acetabular labral sulci using the general population with hip fractures. The acetabular labral sulcus has also been called the sublabral recess, 8 sublabral groove, 10,13 or sublabral slit 17 ; these entities yield similar imaging findings, and the sulcus is described as a normal anatomic variant. Over the past decade, 3 comparison studies have examined MR imaging or MRA and arthroscopy with respect to these modalities abilities to determine the prevalence and location of labral sulci. Saddik et al. 5 evaluated 121 symptomatic patients with a mean age of 43 years and found labral sulci in 30 (25%). They reported that sulci were most common in the anterosuperior (44%) and posteroinferior (48%) regions. Dinauer et al. 13 reported a labral sulcus incidence of 17.4% (4 of 23 hips) and found that all were located posteroinferior to the acetabulum. Studler et al. 8 reported that the incidence of a labral recess was 18% (10 of 57 hips) and that sulci were present in the anteroinferior (7 of 10), anterior (2 of 10), and anterosuperior (1 of 10) regions. In contrast to these 3

6 1378 K-W. KIM ET AL. FIGURE 6. Labral sulci (dotted line) and tears (solid line) were commonly found in the 12- to 3-o clock regions; no labrum is observed in the 5- to 7-o clock area because of the presence of the transverse ligament. studies, our study showed an unexpectedly high prevalence of acetabular labral sulci (48% [47 of 98 hips]), and sulci were most common in the anterosuperior region (48%). However, in an anatomic cadaveric study conducted by Won et al. 17 in 32 adult cadavers with a mean age of 53 years, the prevalence of a sublabral slit was 61.1% (33 of 54 hips). Slit locations were anteroinferior in 39%, posterosuperior in 35.1%, anterosuperior in 24.7%, and posteroinferior in 1.2%. Studies differ regarding sulcus locations. 5,8,13,17 Two studies found that sulci were most commonly located in the anteroinferior region. 8,17 However, in our study only 14% were found in this region (3- to 5-o clock zones). Intraoperatively, we frequently found normal detachment in the anteroinferior quadrant (especially the 5- to 6-o clock zone), and this detachment should not be confused with a labral sulcus or tear 12,18 (Fig 7). In contrast to other studies, Dinauer et al. 13 found that the posteroinferior region was most common and emphasized that no sulci were found elsewhere. However, Saddik et al. 5 criticized this study and mentioned the possibilities of patient bias and of obscuring labral sulci. Our finding that labral sulci were most commonly found in the anterosuperior area of the acetabulum is consistent with the finding of Saddik et al. In our study, although the classification of labral sulci was performed using our own description, we developed a morphologic classification for labral sulci based on labral cleft depth. Labral sulci were classified into 3 different types, and the validity of this classification system was confirmed by intraobserver and interobserver agreements of sulcus type. We found that the incomplete separation type was the most common. Studler et al. 8 described 3 different sulcus types using MR imaging features: a sulcus of less than one-half the labral thickness (67% [4 of 10]), a sulcus of less than the entire thickness (33% [2 of 10]), and a full-thickness sulcus (0%). It is difficult to compare our findings with these because of the different classification methods used, but a full-thickness acetabular sulcus (type III in this study) was rare in the 2 studies. Labral tear locations in symptomatic patients are somewhat disputed. Ikeda et al., 19 in their arthroscopic investigation of 7 young patients, found that all tears were located in the posterior region, and Hase and Ueo 20 found that 70% of patients (7 of 10) had a posterior tear. However, Fitzgerald 21 retrospectively reviewed 55 active adult patients and reported a 92% incidence for anterior or anterosuperior tears. Seldes et al. 22 studied 55 embalmed and 12 fresh-frozen adult hips with a mean age of 78 years and found that 96% of the hips (53 of 55) had a labral tear and that 74% were located in the anterosuperior quadrant. However, in our study 68% of labral tears were in the anterosuperior quadrant (12 to 3 o clock), 27% were in the posterosuperior quadrant (9 to 12 o clock), and 0% were in the posteroinferior quadrant (5 to 9 o clock). These findings concur with previous reports, 5,13 but in our study, labral tears and labral sulci frequently overlapped in the 1- to 3-o clock and 10- to 12-o clock areas. Therefore labral lesions in the anterosuperior or posterosuperior quadrants might require additional attention to distinguish between a labral tear and labral sulcus. However, labral lesions in the posteroinferior quadrant (7 to 9 o clock) were considered not tears but labral sulci. This study has several limitations. First, it was performed in patients who had had trauma to their hip

7 ACETABULAR LABRAL SULCUS 1379 joints, and therefore we were unable to evaluate various predisposing factors known to be closely related to labral tears, especially femoral-side deformities. In addition, there is some possibility that subcapital fracture of the femoral neck might cause labral tearing and affect the prevalence of labral tears. Second, this study has a possible selection bias. The patients were relatively old and had trauma. These factors might be influential, possibly affecting the prevalence of labral tear and sulci. However, although fracture fragments might have torn the labrum and sulcus, they could not create the sulcus lesion, because the sulcus, which is considered a normal variation, is not associated with trauma. Therefore, the prevalence of labral tear might be overestimated whereas the prevalence of labral sulci was probably not influenced by our study design. Finally, it was difficult to compare lesion locations because these have been defined by authors in different ways. To allow comparisons with previous studies, we evaluated lesion locations using a specialized device that divided the locations of acetabular labra into 12 zones, which were easily converted into a quartered system. CONCLUSIONS Labral lesions that are found in the posteroinferior quadrant might be labral sulci, and both labral sulci and tears are most commonly found in the anterosuperior quadrant. Therefore acetabular labral lesions in the anterosuperior area should be inspected closely to allow the differentiation of labral tears and labral sulci and to avoid improper treatment. REFERENCES FIGURE 7. (A) Connection between transverse ligament (TL) and labrum (L). (B) Normal detachment in 5- to 6-o clock zone (arrowhead). This normal detachment in the anteroinferior area (asterisk) should not be confused with a labral sulcus or tear. (C) Complete attachment in 6- to 7-o clock zone (arrowhead). (C, cartilage.) 1. Klaue K, Durnin CW, Ganz R. The acetabular rim syndrome. A clinical presentation of dysplasia of the hip. J Bone Joint Surg Br 1991;73: Leunig M, Podeszwa D, Beck M, Werlen S, Ganz R. Magnetic resonance arthrography of labral disorders in hips with dysplasia and impingement. Clin Orthop Relat Res 2004: Schmerl M, Pollard H, Hoskins W. Labral injuries of the hip: A review of diagnosis and management. J Manipulative Physiol Ther 2005;28: Hickman JM, Peters CL. Hip pain in the young adult: Diagnosis and treatment of disorders of the acetabular labrum and acetabular dysplasia. Am J Orthop (Belle Mead NJ) 2001;30: Saddik D, Troupis J, Tirman P, O Donnell J, Howells R. Prevalence and location of acetabular sublabral sulci at hip arthroscopy with retrospective MRI review. AJR Am J Roentgenol 2006;187:W507-W Czerny C, Hofmann S, Neuhold A, et al. Lesions of the acetabular labrum: Accuracy of MR imaging and MR arthrography in detection and staging. Radiology 1996;200:

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