In this in vitro study of the hip joint we examined which soft tissues act as primary and secondary passive rotational restraints when the hip joint is functionally loaded. A total of nine cadaveric left hips were mounted in a testing rig that allowed the application of forces, torques and rotations in all six degrees of freedom. The hip was rotated throughout a complete range of movement (ROM) and the contributions of the iliofemoral (medial and lateral arms), pubofemoral and ischiofemoral ligaments and the ligamentum teres to rotational restraint was determined by resecting a ligament and measuring the reduced torque required to achieve the same angular position as before resection. The contribution from the acetabular labrum was also measured. Each of the capsular ligaments acted as the primary hip rotation restraint somewhere within the complete ROM, and the ligamentum teres acted as a secondary restraint in high flexion, adduction and external rotation. The iliofemoral lateral arm and the ischiofemoral ligaments were primary restraints in two-thirds of the positions tested. Appreciation of the importance of these structures in preventing excessive hip rotation and subsequent impingement/instability may be relevant for surgeons undertaking both hip joint preserving surgery and hip arthroplasty. Cite this article: Bone Joint J 2015; 97-B:484–91

The acetabular labrum is a soft-tissue structure which lines the acetabular rim of the hip joint. Its role in hip joint biomechanics and joint health has been of particular interest over the past decade. In normal hip joint biomechanics, the labrum is crucial in retaining a layer of pressurised intra-articular fluid for joint lubrication and load support/distribution. Its seal around the femoral head is further regarded as a contributing to hip stability through its suction effect. The labrum itself is also important in increasing contact area thereby reducing contact stress. Given the labrum’s role in normal hip joint biomechanics, surgical techniques for managing labral damage are continuously evolving as our understanding of its anatomy and function continue to progress. The current paper aims to review the anatomy and biomechanical function of the labrum and how they are affected by differing surgical techniques. Take home message: The acetabular labrum plays a critical role in hip function and maintaining and restoring its function during surgical intervention remain an essential goal. Cite this article: Bone Joint J 2016;98-B:730–5

Aims. Research on hip biomechanics has analyzed femoroacetabular contact pressures and forces in distinct hip conditions, with different procedures, and used diverse loading and testing conditions. The aim of this scoping review was to identify and summarize the available evidence in the literature for hip contact pressures and force in cadaver and in vivo studies, and how joint loading, labral status, and femoral and acetabular morphology can affect these biomechanical parameters. Methods. We used the PRISMA extension for scoping reviews for this literature search in three databases. After screening, 16 studies were included for the final analysis. Results. The studies assessed different hip conditions like labrum status, the biomechanical effect of the cam, femoral version, acetabular coverage, and the effect of rim trimming. The testing and loading conditions were also quite diverse, and this disparity limits direct comparisons between the different researches. With normal anatomy the mean contact pressures ranged from 1.54 to 4.4 MPa, and the average peak contact pressures ranged from 2 to 9.3 MPa. Labral tear or resection showed an increase in contact pressures that diminished after repair or reconstruction of the labrum. Complete cam resection also decreased the contact pressure, and acetabular rim resection of 6 mm increased the contact pressure at the acetabular base. Conclusion. To date there is no standardized methodology to access hip contact biomechanics in hip arthroscopy, or with the preservation of the periarticular soft-tissues. A tendency towards improved biomechanics (lower contact pressures) was seen with labral repair and reconstruction techniques as well as with cam correction. Cite this article: Bone Joint Res 2023;12(12):712–721

The fibrocartilaginous labrum acetabulare enlarges the acetabular socket and contributes to the stability of the femoral head. In DDH the labrum is everted and pushed upward by the femoral head. In the dislocated hip the labrum is often inverted into the acetabular cavity and obstructs anatomic reduction. In the past, excision of the labrum was performed to allow the reduction of the femoral head. The aim of this study was to evaluate the position of the labrum in early detected decentered hips and its role in the early treatment of DDH. During the eleven-year period from 1992–2002, 21,709 neonates (43,418 hips) were examined both by ultrasound and by Ortolanis test to establish the diagnosis of DDH. According to Grafs classification the following hips were present: 298 type D-hips, 252 type IIIa, 4 type IIIb and 20 type IV. Therefore 431 of the patients (356 females and 75 males) showed 574 sonographically unstable hips affected by DDH (1.32%). Due to its echogenic structure, the fibrocartilaginous labrum is clearly visible by ultrasound. In type D, type IIIa, and type IIIb it was always located cranially to the femoral head; in type IV it was located medially to the femoral head. The average age of the children at the time of the diagnosis was 42 33 days (mean value SD). Ortolanis test was positive in 61 hips (10.63%) and negative in the remainder of the hips (89.37%). 21.5 % of the cases were diagnosed within the second week of life, 52.9 % between the third and the eighth week, and 25.5 % after the eighth week. The labrum was not inverted in any of these cases, nor was an open reduction necessary in order to remove it as an obstacle to the closed reduction. Only the ultrasound examination allowed the early diagnosis of the unstable decentered hips. The importance of the labrum decreases when an early diagnosis can be made and an early treatment can be performed

Coxarthrosis is a common problem. Changes in all articular structures during coxarthrosis were described extensively, besides labrum. This study was designed to:. describe histological changes in the labrum during coxarthrosis, and correlate them with radiographic changes. compare changes in various portions of the labrum. assess labrum status in main etiological types of coxarthrosis. Methods: Consecutive patients scheduled for THR were analyzed. Cases of systemic disorders, septic arthritis of the hip, previous hip surgeries were excluded. All hips were assessed radiographically, and staged according to Hip Osteoarthrosis Radiographic Grading System (HORGS) and for etiology to: dysplastic, idiopathic and avascular necrosis (AVN) groups. From the group of 90 patients in 77 hips we were able to harvest hip labrum during THR. All labra were examined by histological techniques for the presence of: labral matrix degeneration of, granular matrix breakdown, pseudocysts formation, matrix calcifications, chondrocyte apoptosis, macrophage and lymphocyte infiltration, vascular ephiteliar cell and blood vessel formation. After analysis labral histological degeneration score (LHDS) (0–11 points) was designed and computed. Results: Degeneration of the labral matrix was found in all specimens, granular matrix breakdown in 98%, pseudocysts in 91%, calcifications in 22 %, apoptosis in 19%, macrophage infiltration in 30%, lymphocyte infiltration in 19 %, vascular ephiteliar cell in 39 % and blood vessel formation in 35 % of specimens. Average LHDS for all cases was 5.4, and was the highest (6.1) in dysplastic coxarthrosis, followed by idiopathic changes (LHDS 5.7). Significantly lower (p=0.02) values were found in AVN group (LDHS 3.7). In 35 randomly selected patients anterior, middle and posterior portion of labrum was evaluated separately. The highest LDHS was found in middle portion 5.9, comparing to anterior (LDHS 3.5) and posterior (LDHS 4.25) portion, and this difference was significant (p=0.002). Radiographic assessment showed that 10 % of patients had grade 1 changes according to HORGS, 28 % grade 2, and 62% grade 3 changes. Strong correlation (p=0.0002) was found between LDHS and radiographic HORGS scores. Labra of the patients with severe coxathrosis showed more degeneration changes. Conclusions: Hip labrum shows various degenerative changes in the course of coxarthrosis like other structures in the joint. Degree of histological degeneration correlates well with radiographic changes. Small labral changes were found in AVN group with no destruction of acetabulum, the highest labral degeneration was found in cases of dysplastic coxarthrosis. The biggest changes were noted in the middle portion of the labrum. The results of this study proved that degeneration of the labrum is simultaneous with other articular structures and labral degeneration itself promotes coxarthrosis

The purpose of the study was to describe the normal anatomy of glenoid labrum. Twenty dry bone scapulas and 19 cadaveric shoulders were examined. Light microscopy was performed on 12 radial slices through the glenoid. An external capsular circumferential ridge, 7–8mm medial to the glenoid rim marks the attachment of the capsule. A separate internal labral circumferential ridge 4mm central to the glenoid rim marks the interface for the labrum and articular cartilage. A superior-posterior articular facet contains the superior labrum. Two thirds of the long head of biceps arise from the supraglenoid tubercle, the remainder from the labrum. The superior labrum is concave and is loosely attached to the articular cartilage and glenoid rim. In contrast the anterior-inferior labrum is convex, attaches 4mm central to the glenoid rim and has a strong attachment to articular cartilage and bone. The anatomy of the superior and anteroinferior labrum are fundamentally different. Suture anchor repair of the superior labrum should be 7mm medial to the glenoid rim whereas the anterior-inferior labrum should be repaired to the face of the glenoid. By defining the normal anatomy of the superior labrum, pathological tears can be identified

Since January 1993 we have carried out MR arthrography on 23 patients with clinical symptoms and signs of abnormality of the acetabular labrum. Most of the patients were young adults. Such symptoms are known precursors of osteoarthritis, and therefore early and accurate evaluation is required. We assessed the value of MR arthrography of the hip as a minimally-invasive diagnostic technique, in a prospective study and compared the findings with those at subsequent operations. All the patients complained of groin pain; 22 had a positive acetabular impingement test and 15 had radiological evidence of hip dysplasia. In 21 of the patients, MR arthrography suggested either degeneration or a tear of the labrum or both. These findings were confirmed at operation in 18 patients, but there was no abnormality of the labrum in the other three. In two of the patients, MR arthrography erroneously suggested an intact labrum. Both MR arthrography and intraoperative inspection located lesions of the superior labrum most often, and these appeared slightly larger on arthrography than at operation. We consider that MR arthrography is a promising diagnostic technique for the evaluation of abnormalities of the acetabular labrum

The purpose of the study was to describe the normal anatomy of glenoid labrum. 20 dry bone scapulas and 19 cadaveric shoulders were examined. Light microscopy was performed on 12 radial slices through the glenoid. An external capsular circumferential ridge, 7–8mm medial to the glenoid rim marks the attachment of the capsule. A separate internal labral circumferential ridge 4mm central to the glenoid rim marks the interface for the labrum and articular cartilage. A superior-posterior articular facet contains the superior labrum. Two thirds of the long head of biceps arise from the supraglenoid tubercle, the remainder from the labrum. The superior labrum is concave and is loosely attached to the articular cartilage and glenoid rim. In contrast the anterior-inferior labrum is convex, attaches 4mm central to the glenoid rim and has a strong attachment to articular cartilage and bone. The anatomy of the superior and anterior-inferior labrum are fundamentally different

Introduction:. Most cases of hip osteoarthritis (OA) are believed to be caused by alterations in joint contact mechanics resulting from pathomorphologies such as acetabular dysplasia and acetabular retroversion. Over the past 13 years, our research group has focused on developing approaches for patient-specific modeling of cartilage and labrum in the human hip, and applying these approaches to study hip pathomorphology. The long term objective is to improve the understanding of the etiology of OA related to hip pathomorphology, and to improve diagnosis and treatment. The objectives of this presentation are to provide a summary of our subject-specific modeling approach, and to describe the results of our analysis of hips from three populations of subjects: normal, traditional dysplastic, and retroverted. Methods:. A combined experimental and computational protocol was used to investigate contact mechanics in ten normal subjects (normal center edge angles (CEA), no history of hip pain), ten subjects with hip pain secondary to acetabular dysplasia (CEA less than 25°), and ten patients with a radiographic crossover sign, pain and clinical exams consistent with acetabular retroversion. CT arthrography was used to image cartilage and bone. Volumetric image data were segmented and discretized, and subject-specific finite element models were produced using validated methods [Fig. 1]. Boundary and loading conditions were obtained from instrumented implant and gait data. Contact mechanics were evaluated on the acetabular cartilage and labrum. Labrum contact area and peak contact stress were evaluated. Cartilage contact area, peak and average contact stress were evaluated in six anatomical regions in the acetabulum. Results:. Hip contact patterns were subject-specific, but distinct patterns emerged in the groups. Dysplastic hips had a larger contact area in the lateral region of the acetabulum, while normal hips demonstrated a more distributed contact pattern. The labrum in dysplastic hips supported significantly more load than the labrum in normal hips in all activities [Fig. 2]. Contact in retroverted hips tended to be focused medially and superiorly [Fig. 3]. Retroverted subjects had smaller contact stress and area in most regions. Discussion:. The differences in labrum mechanics between the normal and dysplastic groups provide clear support for the mechanical importance of the acetabular labrum in dysplastic hips. There were only minor differences in cartilage contact stress and area between normal and dysplastic groups, because of a lateral shift in the location of contact and subsequent loading on the acetabular labra in the dysplastic hips. The larger labrum load support and contact area in dysplastic hips indicates that the labrum compensates for the shallow acetabula. Clinically, this may account for the pattern of OA onset in dysplastic hips. The results for the retroverted group do not support the commonly held belief that concentrated posterior loading in retroverted hips leads OA because there were lower contact stresses and areas in the posterior regions of retroverted hips. Further, these results suggest that rim trimming may be appropriate for retroverted hips. The preferred surgery likely depends on subtle patient specific aspects of hip pathoanotomy in both retroverted and dysplastic hips

Introduction:. The sealing function of the acetabular labrum is central to the stability of the hip and the health of the joint. Disruption of the labrum has been shown to reduce intra-articular pressure and increase the rate of cartilage consolidation during static loading. Functional activities require movement of the hip through wide ranges of joint motion which disrupt joint congruency, and thus may alter the seal. This study was performed to test the hypothesis that the sealing function of the labrum varies with the position of the hip during functional activities. Methods:. Six fresh cadaveric hip joint specimens were obtained from donors of average age 45.5 ± 16.1 years (range 25–63 years). Each specimen was dissected free of soft tissue, leaving the capsule and labrum intact, potted in mounting fixtures, and placed in a loading apparatus. Catheters were inserted into the central and peripheral compartments of each hip to allow infusion of fluid and monitoring of compartment pressures via miniature transducers (OMEGA Engineering, Inc). After application of a joint load of 0.50 BW, fluid was introduced into the central compartment at a constant rate until transport was indicated by a rise in pressure within the peripheral compartment. These measurements were performed with each hip placed in 10 functional positions ranging from −5 to 105 degrees of flexion, −5 to 13 degrees of abduction, and −25 to 35 degrees of external rotation simulating the sequential stages of gait, stooping, and pivoting. Motion analysis was performed via reflective marker arrays attached to the femur and pelvis to allow computer visualization of the position of the pelvis and femur using CT reconstructions. In each hip position, we measured the peak pressure (kPA) developed within the central compartment prior to fluid transfer to the peripheral compartment. Results:. The sealing capacity of the labrum varied wit hip joint position (p = 0.003). Peak pressures were greatest during pivoting (average peak central compartment pressure: 33.9 ± 5.0 kPa; p = 0.001), compared to both gait (22.5 ± 4.1 kPa; p = 0.047) and stoop (9.6 ± 3.6 kPa; p = 0.004). During the pivoting maneuver, peak pressures increased in a linear fashion with increasing hip extension and external rotation. Conversely, the sealing capacity of the labrum was reduced during stooping once hip flexion exceeded 70° and internal rotation was greater than 15°. The positions simulating gait consisted of minimal to no joint rotation, and peak pressures varied little between the four positions. Discussion:. The sealing ability of the labral seal increases with external rotation of the hip joint, and decreases with increased flexion combined with internal rotation. Changes in joint congruency that occur when the hip is placed in high flexion and internal rotation may be responsible for the loss of sealing function of the labrum during stooping. Our results reveal the importance of joint position during functional activities on the ability of the labrum to seal the central compartment of the hip. Future research will further assess the relationship between these positions and joint injury

The aim of this work was to define the tensile material properties of the glenoid labrum. Previous SEM studies of the labrum have observed three definitive layers, with a densely packed circumferentially orientated collagen core layer. The glenoid labrum from ten cadaveric shoulders were dissected out and divided into eight equal sections. Each section was cut to produce specimens from the core layer using a microtome and a specifically designed cryo-clamp resulting in uniform specimens with dimensions of 1mm x 1mm x 8mm. All of the tensile testing was performed within a controlled-environment unit of 38°C and 100% relative humidity. Each specimen was precycled to a quasi-static state to alleviate the effects of deep-freezing, prior to final testing. The elastic modulus was calculated for each specimen before and after a 5-minute period of stress relaxation and before failure initiation. The mean age of the specimens was 61 years (range 47–70). Load to failure was 2.7N (1.0–7.0). The mean modulus was 10.2MPa (3.0–22.3) before stress relaxation, 18.0MPa (5.8–36.7) immediately after stress relaxation and 22.3MPa (8.4–66.4) before failure initiation. The 1 and 2 o’clock specimens had lower moduli than the 4 and 5 o’clock specimens (p=0.01). These results can aid in explaining the differing pathologies encountered around the circumference of the labrum. The high moduli at the 4 and 5 o’clock positions may reflect the ability of this portion of the labrum to accommodate forces and thus resist anteroinferior subluxation. The lower moduli at the 1 and 2 o’clock positions suggest that this portion of the labrum is less apt to accommodate tension; this might explain the higher incidence of labral foramen observed in this area and the anatomical variant of the Buford complex

We studied the sensitivity and specificity of magnetic resonance arthrography (MRa) for the diagnosis of lesions of the acetabular labrum in 20 cadaver hips. The MRa results were compared with macroscopic and histological findings. We found that the labrum could be satisfactorily delineated by MRa and that large detachments could be identified satisfactorily. The diagnosis of small detachments and degeneration of the labrum was less reliable

In a 41-year-old man, right-sided infraspinatus muscle weakness was associated with compression of the suprascapular nerve caused by a spinoglenoid ganglion cyst. The lesion was confirmed using electromyography and MRI. In addition, arthroscopy showed an incomplete discoid labrum. The free inner edge of the labrum was removed as in a meniscectomy of a discoid meniscus in the knee joint. Arthroscopic decompression of the cyst was performed through a juxtaglenoid capsulotomy which was left open. Neurological function recovered completely

To the best of our knowledge, this prospective study is the first to investigate the prevalence of acetabular labrum tears in athletes presenting with groin pain. Eighteen consecutive athletes who presented to our sports clinic with groin pain, underwent Magnetic Resonance Arthrography (MRA). Presence or absence of acetabular labrum tears, were reported on by a Consultant Radiologist, who has an interest in musculoskeletal radiology. In 4 out of 18 athletes with groin pain (22.2%), the Magnetic Resonance Arthrography demonstrated the presence of acetabular labrum tear. Two underwent hip arthroscopy and treatment. Acetabular labrum tears can be a common cause of groin pain in athletes. Sports clinicians have to be well aware of the condition. Magnetic resonance arthrography of the hip can be a valuable tool in diagnosing this pathology

Objectives: During the past decade, acetabular labrum injury has been increasingly recognized as a cause of hip joint pain. Currently, T1-weited MR arthrography (MRa) with gadolinium is the most popular diagnostic imaging technique used for direct detection of acetabular labrum injury. However, the intra-articular injection of gadolinium is not a procedure approved in Japan. We have conducted radial MRa using T2*-weighted images with saline instead. The purpose of this report was to evaluate the sensitivity, specificity, and accuracy of T2*-weighted MRa with saline for the diagnosis of acetabular labrum injury. Methods: Between November 2005 and March 2007, thirty-two hip joints of 30 patients (8 joints of 7 males and 24 joints of 23 females) aged between 13 and 81 (mean; 58) years at the time of study, who underwent MR arthrogram and hip arthroscopy were studied. Prior to performing T2*-weighted MRa, a mixture of 5ml of 2% lidocaine chloride, 5ml of 64% iotrolan, and 15ml of saline was injected under fluoroscopy guidance injected into the hip joint. T2*-weighted MRa was conducted using a 1.5-tesla magnet and local surface coil in radial slices perpendicular to the labral rim, at 15-degree intervals. Radial sequences were operated at T2*-weighted images, Gradient echo method, TR of500ms, TE of 20ms, flip angle of 30 degrees, slice thickness of 5 mm, and FOV of 180 mm. On the MRa, acetabular labrum tear was diagnosed when inflow of contrast medium (high intensity) was observed continuous with the joint space at the base of acetabular labrum. Hip arthroscopy was conducted in the supine position by the standard three portal methods. The results of T2*-weighted MRa were compared with arthroscopic findings to calculate the sensitivity, specificity and accuracy of T2*-weighted MRa. Results: On T2*-weighted MRa, acetabular labrum tear was observed in 17 joints, and no abnormalities in 15 joints. From arthroscopic findings, acetabular labrum tear was observed in 20 joints, and no acetabular labrum abnormalities in 12 joints. Comparing the two methods, the T2*-weighted MRa results were true positive in 17 joints, true negative in 12 joints, and false negative in 3 joints. Therefore, MRa had a sensitivity of 85%, specificity of 100%, and accuracy of 90.6%. Discussion: MRa has become the standard imaging technique for the diagnosis of acetabular labrum tear. The sensitivity was reported to range from 63 to 100%, specificity from 44 to 75%, and precision from 63 to 94%. Our results showed that this method provides sensitivity, specificity and accuracy that approach conventional MRa, demonstrating that radial T2* weighted MRa is a useful imaging technique for the diagnosis of acetabular labrum pathology. Conclusions: We recommend T2*-weighted MRa with saline for the diagnosis of acetabular labrum injury

In this study, we evaluated the labrum tear using radial sequence 3D Multiple Echo Recombined Gradient Echo (MERGE) MRI without arthrography based on modified Czerny's classification, comparing with actual arthroscopic findings. A total of 61 hips including 27 hips of femoroacetabular impingement (FAI), 19 hips of borderline development dysplasia of the hip (BDDH) and 15 hips of early stage osteoarthritis (OA) were enrolled this retrospective study. MRI findings evaluated in each three regions of interest; anterior region, anterolateral region, and lateral region. The cases with severe degeneration that is not concordant with any original Czerny's classification is defined as stage4. We compared MRI findings with arthroscopic findings and calculated the sensitivity, specificity, and likelihood ratio in terms of the existence of labrum tear. MRI findings revealed labrum tear more frequently in anterolateral than lateral (p<0.001). Especially in FAI group, labrum tear was more frequently observed by MRI in anterolateral than lateral (p=0.006). In comparison with MRI findings and arthroscopic findings, the sensitivity was 97%, specificity was 79% and likelihood ratio was 4.59 as average of all regions in terms of the existence of labrum tear. In each region, sensitivity and specificity was 97% and 50% in anterior, 97% and 100% specificity in anterolateral, 94% and 81% in lateral, respectively. Thus, MERGE MRI revealed excellent sensitivity and specificity for diagnosis of labrum tear, especially in anterolateral region. The cases with severely degenerated labrum were classified as newly defined stage 4, which was recognized frequently in OA cases

The shape of the glenoid can vary between pear and oval, depending on the presence of a glenoid notch. We measured the glenoid notch angle (the angle between the superior and inferior part of the anterior glenoid rim) in 53 embalmed cadavers and investigated its relationship with the labral attachment to the glenoid at that point. The attachment of the anterosuperior labrum at the site of the glenoid notch was classified as tight or loose or, in some cases, there was a sublabral foramen. The anterior labrum was then removed and digital images perpendicular to the glenoid notch were taken. Using a digital image analysis program, the angle of the glenoid notch was measured. In 37 shoulders (70%) the attachment of the labrum at the site of the glenoid notch was assessed as tight and in eight (15%) as loose. In eight shoulders (15%) a sublabral foramen was found. The mean glenoid notch angle was 153° in the loosely attached group, 159° in the sublabral foramen group and 168° in the group with a tight attachment. The presence of a glenoid notch was noted only when the glenoid notch angle was less than 170°. The glenoid notch angle is related to the attachment of the labrum. In the presence of a glenoid notch, there is more likely to be a loosely attached labrum or sublabral foramen. The loose attachment of the anterosuperior labrum may be a predisposing factor in traumatic anterior instability

Purpose: The glenoid labrum is a significant passive stabiliser of the shoulder joint. However, its microstructural form remains largely unappreciated, particularly in the context of function. An understanding of the labral structure leads to mechanical hypotheses, and therefore functional role in stability and load distribution, will aid an educated approach to surgical timing and repair. Method: Fresh frozen cadaveric shoulders were grossly harvested via an extended Deltopectoral incision. The Glenohumeral joint was arthroscoped using a modification of Snyders (1989) routine in order to determine the specific anatomy of the capsulolabral complex. The glenoid fossa was then osteotomised before using micro-surgical loupes to section the labrum. Specimens were analysed using Scanning and Transmission Electron Microscopy and Confocal microscopy. Standard processing procedures were used to examine TEM specimens and the data was quantified by computational analysis. Specimens for SEM were cryofractured and Extracellular Matrix removed using a cell maceration technique to expose collagen fibre networks. Images were evaluated qualitatively. Sliced specimens for confocal were serially analysed along their z-axis, and post-processed to form 3-D reconstructions of collagen fibres. Results: Two distinct homogenous areas were identified: (1) a superficial tight meshwork of fibrils and (2) a deep layer with a densely packed fibrous braid which were circumferential in orientation. A third area showed varying distribution of loosely arranged collagen fibres ranging from small fibres apposing area 1 to larger interleaved groupings near area 2. In radial transverse section, both normal and abnormal (stellate and spiral) fibrils were identified. Conclusion: Contrary to published evidence, our results suggest the glenoid labrum is subjected a number of mechanical environments. Possibly distinct regions of the labrum contribute to load sharing; a well vascularised hydrated compressive zone and a tensile component distributing circumferential hoop stress, whilst both braiding and region interfaces suggest shear conditions

Osteonecrosis of the femoral head can be caused by a variety of disorders and affects the relatively young patient. Most studies have concentrated on the femoral changes; the sites of early lesions of the labrum and acetabular cartilage have not been recorded. We studied 17 hips with osteonecrosis and a wide congruent joint space on radiographs and by direct inspection of the femoral head, labrum and acetabular cartilage during surgery. All of the femoral heads had some anterosuperior flattening which reduced the head-neck ratio in this area. A consistent pattern of damage to the labrum and the acetabular cartilage was seen in all hips. Intraoperatively, impingement and the cam-effect with its spatial correlation with lesions of the labrum and acetabular cartilage were observed. These findings could be helpful when undertaking conservative surgery for osteonecrosis, since the recognition of early radiologically undetectable acetabular lesions may require modification of the surgical technique

Eleven patients with tears of the acetabular labrum are discussed and the syndrome of the torn labrum is defined. In all cases the lesion was associated with acetabular dysplasia, and a constant early radiological sign was a cyst in the lateral aspect of the acetabulum. The diagnosis was confirmed by arthrography. It is suggested that these tears are degenerative, occurring as a consequence of abnormal stresses imposed by the uncovered lateral portion of the femoral head. Once a tear is present a localised stress point occurs on the femoral head, leading rapidly to degenerative arthritis