Anatomic Relationship of the Femoral Neurovascular Bundle in Patients With Congenital Femoral Deficiency.

BACKGROUND: Congenital femoral deficiency (CFD) is a rare condition that affects the morphology of the hip and surrounding soft tissues. Bony deformity and distorted muscular anatomy are well known, but no studies have described the relationship of the femoral neurovascular (NV) bundle to surgically relevant anatomic landmarks. The authors compared the location of the femoral NV bundle on the affected side in patients with CFD with the unaffected side. The authors hypothesized that the bundle on the pathologic side would be in an abnormal position relative to the unaffected side. METHODS: Thirty-three patients diagnosed with unilateral CFD who had undergone preoperative magnetic resonance imaging of the pelvis were included in our study. The authors identified the femoral NV bundle on the axial cuts and measured its distance from the anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS), and lesser trochanter (LT). Anatomic percent change and absolute measurements were then compared and correlated with associated boney deformities and the Paley classification. RESULTS: The distance from the femoral NV bundle to the ASIS, AIIS, and LT was significantly different compared with the unaffected side. The AIIS absolute distance and AIIS percent change significantly correlated with the neck-shaft angle of the proximal femur. CONCLUSIONS: In patients with CFD, the femoral NV bundle seems to be further from the LT and closer to the AIIS on the affected side when compared with the unaffected side. magnetic resonance imaging may be helpful to understand the course of the femoral NV bundle before reconstruction in patients with CFD; however, the authors recommend identification of the femoral NV bundle before transection of the proximal rectus femoris tendon to provide safe surgical care. LEVEL OF EVIDENCE: Level IV-case-control study of diagnostic studies.

Cement arteriovenogram after hip arthroplasty. / Arteriovenograma de cemento óseo en artroplastia de cadera.

Modern cement implantation techniques during hip arthroplasty rely on high intramedullary pressures which can result in cement extrusion towards femoral nutrient vessels, and thus, the occurrence of a particular image in postoperative radiographs (bone cement arterio-venogram). We report a case series of 14 patients in whom a bone cement arterio-venogram was observed after undergoing a cemented hip arthroplasty. No local or systemic complications developed after cementing nor during a mean follow-up of three years. Bone cement arterio-venogram is a radiologic sign that indicates a good cement pressurisation during surgery and is not associated to medical complications or periprosthetic femoral fractures.

The short external rotators dissection during the posterior approach in total hip arthroplasty did not change the blood flow.

OBJECTIVES: The posterior approach in total hip arthroplasty (THA) often requires dissection of the short external rotators (SERs), which could increase the postoperative dislocation rate. The reattachment of the dissected SERs has been reported to reduce the dislocation rate, while such repair generally causes progression of muscle atrophy. 1 of the suggested causes of atrophy is reduced blood flow to the repaired SERs. The present study aimed to measure the blood flow of the SERs before dissection (pre-tenotomy) and after reattachment (post-reattachment) during the posterior approach in THA. METHODS: This prospective study included 26 patients who underwent THA via the posterior approach. A laser-Doppler rheometer was used to measure the blood flow in the following SERs at the time of pre-tenotomy and post-reattachment: the piriformis muscle (PM), superior gemellus (SG), inferior gemellus (IG), obturator internus (OI), and subcutaneous tissue as a control. RESULTS: The average pre-tenotomy and post-reattachment blood flows (mL/minutes/100 g) were: 1.90 ± 0.28 and 1.92 ± 0.40 in the PM, 1.94 ± 0.20 and 1.99 ± 0.39 in the SG, 1.91 ± 0.21 and 1.94 ± 0.30 in the IG, 1.93 ± 0.22 and 1.98 ± 0.36 in the OI, and 1.94 ± 0.24 and 1.87 ± 0.38 in the subcutaneous tissue. The pre-tenotomy and post-reattachment blood flows did not show significant difference in any muscle. CONCLUSIONS: Laser-Doppler blood flow measurements showed that the blood flow is preserved, even when the SERs are dissected and reattached in THA via the posterior approach.

Where and what arteries are most likely injured with pelvic fractures?: The Influence of Localization, Shape, and Fracture Dislocation on the Arterial Injury During Pelvic Fractures.

Blood vessels passing through pelvic region come into intimate contact with pelvic bone and can be injured by the sharp edges of the dislocated fracture fragments. The aim of the study was to evaluate the influence of localization, shape, and dislocation of individual pelvic ring bones' fractures on arterial injuries. The study group consisted of 474 patients enrolled in a 1-year prospective multicenter study. The pattern of pelvic fracture lines was characterized and recorded on a planar diagram of the subjected side of the pelvis. The diagram was subdivided into 11 designated areas. Frequency of injury at each 11 areas was recorded. The course of individual arteries in the 11 areas was also recorded in relation to each type of pelvic fractures. Out of the 474 investigated patients, the highest proportion of fractures occurred in the areas of the superior (62%) and inferior (59%) ramus of the pubis as well as in the lateral part of the sacrum (19%). These locations can be associated with injuries of the external iliac, obturator, internal iliac, and aberrant obturator arteries. The highest risk of arterial injuries was associated with vertically displaced fractures in the middle part of the superior and inferior pubic rami, along the ischial ramus, in the apex of the greater sciatic notch and in the vicinity of the ventral part of the sacroiliac joint, where the artery runs at a distance of less than 1 cm from the bone. Clin. Anat. 32:682-688, 2019. © 2019 Wiley Periodicals, Inc.

The origin of the medial femoral circumflex artery, lateral femoral circumflex artery and obturator artery.

INTRODUCTION: The most significant blood vessel supplying the hip joint is the medial femoral circumflex artery (MFCA). MFCA with lateral femoral circumflex artery (LFCA) are the first branches of the deep femoral artery (DFA) or they originate directly from the common femoral artery (CFA) or superficial femoral artery (SFA). PURPOSE AND METHODS: We analyzed 100 CT angiogram of the hip region [72 men, 28 women; mean age 46.4 (14-80)] to assess the frequency of each type of division of the MFCA and LFCA from either the DFA or directly from the CFA or SFA. To assess the variations on each side in one individual we analyzed both hips in 73 patients [mean age 46.6 (14-80)]. RESULTS: Many different types of division have been described. The most frequent one in which both the MFCA and LFCA originate from the DFA, was observed in 50% of patients. In 31% of hips the MFCA originates from the CFA. In our study, a normal origin of the obturator artery from the internal iliac artery was observed in 67% of patients and an atypical origin, called corona mortis was observed in 33% of patients. CONCLUSIONS: The deep branch of the MFCA is the main artery supplying the femoral head, it is at risk during surgical approach to the hip joint. The atypical anastomosis called corona mortis is also at risk while performing the approach to pubic bone. Therefore, knowledge of their topography is very important.

Surgical anatomy of the pelvic vasculature, with particular reference to acetabular screw fixation in cementless total hip arthroplasty in Asian population.

PURPOSE: Pelvic vascular injury is a serious complication associated with acetabular component setting with screw fixation in cementless total hip arthroplasty (THA). In this study, we investigated the safety zone for acetabular component setting with screw fixation in cementless THA as a means to prevent pelvic vascular injury. METHODS: Thirty left hip joints of Japanese cadavers (11 males and 19 females) were analyzed. We used a hemispherical measuring cup with 52 guide holes designed to allow vertical insertion of a Kirschner wire. After the measuring cup was placed on the acetabulum, the Kirschner wire was inserted from each guide hole to examine the anatomical relationship between the acetabulum and the pelvic vessels. We calculated the frequency of pelvic vessel punctures and measured the distance from the acetabular surface to the pelvic vessels at each guide hole. RESULTS: Our findings revealed that pelvic vessels do not exist in certain parts of the posterior area of the acetabulum. Furthermore, in this area, intrapelvic vessels are either lacking or located at a distance ≥31 mm from the surface of the acetabulum. CONCLUSION: The posterior area of the acetabulum, excluding its central portion, appeared to be the safety zone for acetabular screw fixation in Japanese cadavers.

Variations in the obturator artery around the obturator foramen assessed by three-dimensional computed tomographic angiography and prevention of vascular-related complications in rotational acetabular osteotomy.

PURPOSE: The aims of this study were (1) to evaluate the anatomical variations and locations of the obturator artery at the obturator foramen using computed tomographic (CT) angiography images and (2) to evaluate the pubic osteotomy site in rotational acetabular osteotomy using postoperative CT images in order to assess the relationship between the obturator artery and the pubic osteotomy site. METHODS: We examined a total of 196 hips in 98 consecutive Japanese patients for aim (1), and 38 consecutive patients who underwent rotational acetabular osteotomy for aim (2). RESULTS: The prevalence of arterial anastomosis of the obturator artery (corona mortis) was 14.3 %, with the obturator artery being located closer to the superior pubic ramus and the osteotomy site in these subjects. CONCLUSIONS: Extensive care should be taken during rotational acetabular osteotomy in patients showing variations of the obturator artery with corona mortis.

Distal Extension of the Direct Anterior Approach to the Hip: A Cadaveric Feasibility Study.

BACKGROUND: The direct anterior approach (DAA) is becoming more popular as the standard surgical approach for primary total hip arthroplasty. However, femoral complications of up to 2.8% have been reported. Therefore, it is important for surgeons to understand the periarticular neurovascular anatomy in order to safely deal with intraoperative complications. METHODS: Anatomic dissections were performed on 20 cadaveric hips. The neurovascular structures anterior to the femur and distal to the intertrochanteric line were dissected and its position was described in relation to anatomic landmarks easily identified through the DAA: anterior superior iliac spine (ASIS), the insertion of the gluteus minimus (GM), and the lesser trochanter (LT). RESULTS: Two clearly distinguishable neurovascular bundles running to the vastus lateralis were seen in 17 of 20 specimens. The average distances to the landmarks were as follows: ASIS-1st bundle = 12.3 cm (range, 9.7-14.5); GM-1st bundle = 3.2 cm (range, 2.2-4); LT-1st bundle = 1.6 cm (range, 0.7-2.8); 1st bundle-2nd bundle = 3.3 cm (range, 1.8-6.1). CONCLUSION: A consistent pattern of 2 clearly distinguishable neurovascular bundles was seen in 85% of the specimens. Knowledge of the position of these neurovascular bundles in relation to the anatomic landmarks makes distal femoral extension of the DAA feasible. Further clinical studies are needed to confirm the safety of the extensile anterior approach.

The Use of Superselective Arteriography in the Evaluation of the Influence of Intracapsular Hip Joint Pressure on the Blood Flow of the Femoral Head.

OBJECTIVE: We aimed to analyze the intracapsular pressure of the hip joint following femoral neck fracture and its relationship to the position of the hip or to traction and (using superselective arteriography) to evaluate the blood supply to the femoral head and the influence of traction and hip position on the blood supply. SUBJECTS AND METHODS: Twenty-six cases of fresh Garden type I-III femoral neck fractures were enrolled. After being placed in the neutral position, in internal rotation or with traction of 3 and 5 kg, respectively, intracapsular manometric changes were measured. Eight cases underwent superselective arteriography of the medial circumflex femoral artery and its branches under the manometric changes of the hip joint capsule. RESULTS: Twenty-four to 48 h after the injury, the intracapsular pressure was significantly higher on the fractured side than on the normal side. The mean pressure was 28.41 ± 9.339 mm Hg in fully extended hips in the neutral position, 79.92 ± 12.80 mm Hg in internally rotated hips, 51.39 ± 15.41 mm Hg in hips with 3 kg of traction and 64.81 ± 13.56 mm Hg in hips with 5 kg of traction. The arteriographic findings revealed that traction and internal rotation reduced the perfusion of the femoral head at the medial circumflex femoral artery and its branches, and also negatively influenced venous reflux. CONCLUSION: Traction and internal rotation both caused the intracapsular pressure of the hip joint to rise considerably, which reduced the femoral head perfusion and impeded venous reflux. This could lead to avascular necrosis of the femoral head.

POSSIBILITIES OF MODERN TECHNOLOGIES OF VISUALIZATION AND MODELING IN ORTHOPEDICS AND THEIR ROLE IN DEVELOPMENT OF INDIVIDUAL CONSTRUCTIONS IN HIP ARTHROPLASTY.

The article presents the authors' experience. Medical visualization is applied in orthopedics on all stages such as diagnostics, treatment planning and control of the results. Modern approaches in instrumental diagnostics and specialized application-dependent software allowed a new qualitative level of orthopedics and medical care in different areas of medicine. Modern technologies gave a lot of opportunities to doctors in order to improve diagnostics at higher level, make an individual planning of operations and built individual implants, when it wasn't possible to use standard constructions.

Anatomy, classification and treatment of intracapsular hip fractures.

Hip fractures are increasingly common, given the increasing ageing, osteoporotic population with significant medical comorbidities. This review summarizes the anatomy of the proximal femur, reviews classification systems and gives recommendations for use of each treatment modality.

The vascular supply of hip joint and its clinical significant / Suministro vascular de la articulación de la cadera y su significado clínico

The hip joint gains its vascular supply from the superior gluteal arteries as well as from the medial and lateral circumflex femoral arteries with the first perforating artery. In gluteal trauma, the superior and inferior gluteal artery may be affected which may end with vascular insult of hip joint. The current study includes a dissection of 171 cadavers to examine the vascular supply of hip joint. In 99.3% of articular branch arises from the superior gluteal artery either directly or indirectly (95.4% or in 3.9%, respectively). In 81% of articular branch arises from the inferior gluteal artery either directly or indirectly in 78% or in 3%. In 20.3% of articular branch arises from the coexistence of sciatic artery either directly or indirectly (17.7% or in 2.6%, respectively). Infrequently, the internal pudendal artery gives articular branch in 0.4%. Further, there is no difference between male and female in hip joint supply in current study. Based on current study's result, the dominant articular branch of vascular supply of the hip joint comes from the superior gluteal artery whereas the inferior gluteal artery comes beyond due its congenital absence. The coexistence sciatic artery is a replacement artery for superior or inferior gluteal artery in case of congenital absence. Due to aneurysm of the three previous arteries after trauma, it is important to study their course and articular branches to avoid iatrogenic fault of joint vascular insult during surgical management of either true or false aneurysm.

La articulación de la cadera obtiene su suministro vascular desde las arterias glúteas superiores, así como desde las arterias circunflejas femorales lateral y medial y la primera arteria perforante. En el trauma glúteo, las arteria glúteas superior e inferior pueden verse afectadas, lo que puede terminar con una lesión vascular de la articulación de la cadera. Este estudio incluyó la disección de 171 cadáveres con el fin de examinar el suministro vascular de la articulación de la cadera. El 99,3% de las ramas articulares se originan de la arteria glútea superior, ya sea directa o indirectamente (95,4% o en 3,9%, respectivamente). En 81% de los casos, la rama articular sse origina de la arteria glútea inferior, directa o indirectamente (78% y 3%, respectivamente). El 20,3% de la rama articular se origina de la conexistencia de la arteria ciática, ya sea directa o indirectamente (17,7% y 2,6%, respectivamente), y con poca frecuencia, la arteria pudenda interna origina una rama articular (0,4%). Además, los resultados no mostraron diferencia en el suministro de articulación de la cadera entre hombres y mujeres. En base a nuestros resultados, podemos señalar que la rama articular dominante de suministro vascular de la articulación de la cadera proviene de la arteria glútea superior, mientras que la arteria glútea inferior aporta de manera escasa debido a su ausencia congénita. La coexistencia de una arteria ciática, constituye un reemplazo de las arterias glútea superior o inferior en caso de ausencia congénita. En caso de un aneurisma de alguna de las tres arterias anteriores, posterior a un trauma, resulta importante estudiar su curso y ramas articulares para evitar una lesión vascular iatrogénica conjunta durante el tratamiento quirúrgico de aneurisma de tipo verdadero o falso.

Human fetal topographical anatomy of the femoral triangle in relation with change in the hip joint position.

Fetal hip joint is characterized by its highly flexion and lateral rotation although adult anatomy of the femoral nerve and iliofemoral ligament suggested the medial rotation. To investigate topographical anatomy of the femoral nerve, artery and vein in the femoral triangle, we histologically examined 11 fetuses (15-37 weeks). The nerve-vessel topographical relation was basically similar to that in adults, but the fan-like nerve division was seen in the horizontal plane in the smaller specimens in contrast to that included in the sagittal plane in the larger specimens. The medial or internal rotation of the nerve division seemed to occur in late stage fetuses, at birth and at infancy. Blood supply to the head of the femur might be also accelerated by changes in the hip joint position.

Dynamic gadolinium-enhanced MRI of the proximal femur: preliminary experience in healthy children.

OBJECTIVE: The purpose of this study is to use dynamic contrast-enhanced MRI to evaluate the perfusion characteristics of the proximal femur in the growing skeleton. MATERIALS AND METHODS: We evaluated 159 subjects (mean age, 5.67 years) who underwent a well-controlled protocol of contrast-enhanced MRI of the abdomen and hips. Perfusion and permeability parameters (enhancement ratio peak, AUC, time to peak, and rate of extraction) for six regions of the proximal femur were calculated. RESULTS: A decrease with age was found for all contrast kinetics parameters in all regions (p < 0.001). Perfusion parameters differed between the regions (p < 0.001). The highest perfusion and permeability parameters were found in the metaphyseal spongiosa, metaphyseal marrow, and periosteum. The metaphyseal spongiosa had a highly vascular pattern of enhancement and showed the highest enhancement ratio peak, AUC, and rate of extraction and the lowest time to peak. The metaphyseal marrow showed a vascular pattern of enhancement with a lower peak compared with the metaphyseal spongiosa. The periosteum showed prompt nonvascular contrast enhancement that reached a plateau that remained elevated. CONCLUSION: The highest enhancement was seen in areas involved with growth: the metaphyseal spongiosa, which is related to endochondral ossification, and the periosteal cambium, which is related to membranous ossification. The enhancement characteristics are radically different: in the spongiosa; enhancement is brisk and declines, with a vascular pattern, whereas contrast uptake increases with time in the periosteum. Recognition of normal enhancement patterns of the proximal femur is important for distinguishing normal development from pathologic processes.

Laboratory-monitored fondaparinux and coagulation activity in association with total hip replacement.

Fondaparinux, indirect factor Xa (FXa) inhibitor, is recommended for thromboprophylaxis for high-risk patients undergoing major orthopedic surgery. We evaluated the prothrombotic state and anticoagulant intensity of fondaparinux (2.5 mg daily) after total hip replacement (THR). Twenty patients underwent THR - seven bilateral and 13 unilateral. Blood samples were collected preoperatively and at 6 h, 8 h (2 h after fondaparinux), 1 day (12-14 h after fondaparinux), and 4 weeks (12-14 h after fondaparinux) postoperatively. Antithrombin (AT), fibrinogen, factor VIII activity, coagulation times, thrombin-AT (TAT) complex, D-dimer, C-reactive protein, prothrombinase-induced clotting time (PiCT) and anti-Xa activity were measured. The latter two were also tested after plasma spiking with fondaparinux 0-1.25 µg/ml. In spiked prophylactic fondaparinux samples (0-0.25 µg/ml), PiCT and anti-Xa activity correlated (r = 0.84) better than in the patient samples (r = 0.35). On the first day, anti-Xa activity and PiCT dissociated, and PiCT lost sensitivity for fondaparinux. AT decreased but stayed within the normal range, whereas TAT complex and D-dimer peaked at 6 h as signs of thrombin generation. On the first postoperative day, TAT and D-dimer halved. Bilateral THR associated with higher TAT and D-dimer levels up to 4 weeks. Perioperative FVIII levels were not affected, but were elevated in both groups (range 191-211%) after 4 weeks. Anti-Xa activity detected prophylactic fondaparinux with higher sensitivity than PiCT in vitro, but even more so in vivo. Thus, PiCT is not the method of choice to assess fondaparinux at least in association with THR. THR, bilateral more than unilateral, increased thrombin generation and D-dimer 7-11-fold early after surgery. Factor VIII activity and D-dimer remained elevated even after 4 weeks despite the compliant thromboprophylaxis with fondaparinux.

Anatomical details of neurogenic heterotopic ossification anterior to the ankylotic hip.

Neurogenic heterotopic ossification (NHO) is a common complication in patients with spinal cord injury (SCI) and traumatic brain injury (TBI). Although there are many reports regarding the etiology, pathophysiology, and medical management, few studies elaborate the anatomical details of NHO, which leads to ankylosis of the hip joint. A prospective study on surgical resection of NHO in patients with hip ankylosis was conducted. Radiography and magnetic resonance imaging (MRI) were used to assess the relationship of the NHO block with the blood vessels, peripheral nerve, and surrounding muscles and bones. The anatomical relationships were also assessed and documented during the surgical procedures. NHO, which is anterior to the hip and causes hip ankylosis, settles into tissue planes without involving the tissue itself and does not disrupt the femoral neurovascular structures. The NHO bone block can then fuse to the cortex of adjacent bone. During resection, the normal bony contour should be exposed as a marker to guide the resection in order to avoid iatrogenic fracture.

Does dynamic immobilization reduce chondrocyte apoptosis and disturbance to the femoral head perfusion?

The purpose of this study is to investigate whether the dynamic hip immobilization is more favourable for lessening ischemic injury to the immature femoral head than a static immobilization. 152 Japanese white rabbits were divided into four groups randomly, and the hips were immobilized into "human" position (group A), "frog leg" position (group B) and "dynamic frog leg" position (group C). Group D was used as control. Ten rabbits in each group were killed, and the hip specimens were harvested at 1, 2, and 3 weeks after immobilization. Bcl-2/Bax expression balance and chondrocytes apoptosis were analyzed. The remaining eight rabbits in each group were used to measure the blood supply of capital femoral epiphysis by selective vascular perfusion with Indian ink. The Bcl-2/Bax expression ratio in group C was significantly increased than that in group A and B (p<0.001), while that was not significantly different from control group (p=0.0592). At three weeks after immobilization, the average apoptotic ratio was 36.7%, 45.8%, and 26.7% in group A, B and C, respectively (p<0.01). There was no significant difference between group C and normal control (p=0.0597). The perfusion ratio was 0.03±0.03, 0.03±0.02, and 0.08±0.03 in group A, B and C respectively, and 0.12±0.04 in control group (p<0.05). Thus, the dynamic immobilization model exhibited a relatively less chondrocytes apoptosis and disturbance to the femoral head perfusion than other immobilizations in vivo, which therefore may be useful for reducing avascular necrosis following the treatment of developmental dysplasia of the hip.

Differences in regional bone metabolism at the spine and hip: a quantitative study using (18)F-fluoride positron emission tomography.

SUMMARY: This study showed that regional bone blood flow and (18)F-fluoride bone plasma clearance measured by positron emission tomography are three times lower at the hip than the lumbar spine. INTRODUCTION: Measurements of effective bone plasma flow (K (1)), bone plasma clearance (K ( i )) and standardised uptake values (SUV) using (18)F-fluoride positron emission tomography ((18)F-PET) provide a useful means of studying regional bone metabolism at different sites in the skeleton. This study compares the regional (18)F-fluoride kinetics and SUV at the hip and lumbar spine (LS). METHODS: Twelve healthy postmenopausal women with no history of metabolic bone disease apart from two with untreated osteoporosis were recruited. Each subject underwent 60-min dynamic (18)F-PET scans at the LS and proximal femur two weeks apart. K (1), K ( i ) and SUV were measured at the LS (mean of L(1)-L(4)), femoral neck (FN), total hip (TH) and femoral shaft (FS). Differences between sites were assessed using the nonparametric Kruskal-Wallis test with a Bonferroni correction for multiple comparisons. RESULTS: Values of K (1), K ( i ) and SUV at the FN, TH and FS were three times lower than at the LS (p = 0.003). Amongst the proximal femur sites, K ( i ) and SUV were lower at the FS compared with the FN and TH, and SUV was lower at the TH compared with the FN (all p < 0.05). The volume of distribution was lower at the TH and FS compared with the LS (p < 0.05). CONCLUSION: The lower values of K (1), K ( i ) and SUV at the hip suggest that lower bone blood flow in the proximal femur is an important factor explaining the principal reason for the differences in bone fluoride kinetics between the LS and hip sites.

Vascularity and histology of fetal labrum and chondrolabral junction: its relevance to chondrolabral detachment tears.

PURPOSE: Recently, acetabular labral tears were recognized as a source of hip pain. Most of these tears were found to be localized at the chondrolabral junction. The purpose of this study was to evaluate the chondrolabral junction in reference to its collagen fiber orientation and its vascularity, which might be used to explain the preponderance of labral tears. METHODS: Eighteen formalinized fetuses with a mean gestational age of 17 weeks (range: 11-24 weeks) were examined. The acetabuli were removed en bloc with the proximal femur for ease of orientation. The acetabuli were prepared and examined in four quadrants, namely, anterior, superior, posterior, and inferior. RESULTS: The staining pattern of the posteroinferior labrum was more dense than the anterosuperior labrum, due to its high collagen content. Collagen fibers in the posteroinferior quadrants were oriented perpendicularly to the chondrolabral junction, while those in the anterosuperior quadrants had a parallel oriented. Perpendicular collagen orientation and high collagen content may explain the stronger anchorage of the labrum to the bony acetabulum in posteroinferior quadrants. All of the vessels supplying the labrum originate from the capsular connective tissue and traverse the body of the labrum to reach the articular side. None of these vessels traverse the chondrolabral junction to reach the bony acetabulum. The total number of blood vessels was significantly higher in the capsular zone than in the articular zones. The number of blood vessels did not differ between the acetabular quadrants. CONCLUSIONS: In an effort to understand the chondrolabral junction tears, we can conclude that collagen content and fiber orientation may represent the histological basis for the predominance of tears at the anterosuperior region.