The influence of the acetabular labrum seal, intact articular superficial zone and synovial fluid thixotropy on squeeze-film lubrication of a spherical synovial joint

Bibliometric analysis of the acetabular labrum

The acetabular labrum (AL) plays a crucial role in the normal physiological functioning of the hip joint. This study aims to present an overview of the current status and research hotspots concerning the AL and to explore the field from a bibliometric perspective. A total of 1918 AL-related records published between January 1, 2000 and November 8, 2023 were gathered from the Web of Science Core Collection database. By utilizing tools such as HisCite, CiteSpace, VOSviewer, and the R package "bibliometrix," the regions, institutions, journals, authors, and keywords were analyzed to predict the latest trends in AL research. Global research interest and publication output related to this topic continues to escalate. The United States leads in international collaborations, number of publications, and citation frequency, underscoring its preeminent position in this field. The American Hip Institute emerged as the most prolific institution, making the greatest contribution to publications. Notably, Arthroscopy and the American Journal of Sports Medicine are the 2 most popular journals in this domain, accounting for 13.29% and 10.1% of publications, respectively, and were also found to be the most co-cited journals. Amongst authors, Benjamin G. Domb leads with 160 articles (8.35%), while Marc J. Philippon is the most frequently cited author. The keyword co-occurrence network showed 3 hot clusters, including "AL," "femoral acetabular impingement (FAI)," and "osteoarthritis." In addition, "survivorship," "FAI," and "patient-reported outcomes" were identified as trending topics for future exploration. This study represents the first comprehensive bibliometric analysis, summarizing the present state and future trends in AL research. The findings serve as a valuable resource for scholars, offering practical insights into key information within the field and identifying potential research frontiers and emerging directions in the near future.

Mechanical stretching induces calcification and cartilage matrix metabolism, causing degeneration of the acetabular labrum

PURPOSE

The acetabular labrum plays an important role in joint lubrication, and damage to this structure leads to osteoarthritis. This study aimed to histologically classify the degree of degeneration of the acetabular labrum and to investigate the changes in gene expression induced by mechanical stretching.

METHODS

We obtained acetabular labrum cells from patients with hip osteoarthritis during total hip arthroplasty (n = 25). The labrum was stained with safranin O, and images were histologically evaluated using a new parameter, the red/blue (R/B) value. The samples were divided into the degenerated group (D group: n = 18) and the healthy group (H group: n = 7) in accordance with the Kellgren-Lawrence (KL) grade. The cultured acetabular labral cells were subjected to loaded uniaxial cyclic tensile strain (CTS). After CTS, changes in gene expression were examined in both groups.

RESULTS

Spearman's correlation analysis revealed that the R/B value was significantly correlated with the KL grade and the Krenn score. The expression levels of genes related to cartilage metabolism, osteogenesis and angiogenesis significantly increased after CTS in the H group, while gene expression in the D group showed weaker changes after CTS than that in the H group compared to the nonstretched control group.

CONCLUSIONS

The degree of labral degeneration could be classified histologically using the R/B value and the KL grade. Mechanical stretching caused changes in gene expression that support the pathological features of labral degeneration.

Squeeze-film properties of synovial fluid and hyaluronate-based viscosupplements

The rheological properties of synovial fluid and hyaluronate (HA) solutions have been studied using a variety of viscometers and rheometers. These devices measure the viscosity of the fluid's resistance to shearing forces, which is useful when studying the lubrication and frictional properties of movable joints. Less commonly used is a squeeze-film fluid test, mechanistically similar to when two joint surfaces squeeze interposed fluid. In our study, we used squeeze-film tests to determine the rheological response of normal bovine synovial fluid and 10 mg/ml HA-based solutions, Hyalgan/Hyalovet, commercially available 500-700 kDa HA viscosupplements, and a 1000 kDa sodium hyaluronate (NaHy) solution. We found similar rheological responses (fluid thickness, viscosity, viscosity-pressure relationship) for all three fluids, though synovial fluid's minimum squeeze-film thickness was slightly thicker. Squeeze-film loading speed did not affect these results. Different HA concentrations and molecular weights also did not have a significant or consistent effect on the squeeze-film responses. An unexpected result for the HA-solutions was a linear increase in minimum fluid-film thickness with increasing initial fluid-film thickness. This result was attributed to faster gelling of thicker HA-solutions, which formed at a lower squeeze-film strain and higher squeeze-film strain rate compared to thinner layers. Also included is a review of the literature on viscosity measurements of synovial fluid and HA solutions.

The utility of hip arthroscopy for patients with painful borderline hip dysplasia

PURPOSE

We measured the width of the acetabular labra in, and the clinical outcomes of, patients with borderline hip dysplasia (HD) who underwent arthroscopy.

METHODS

A total of 1436 patients who underwent hip arthroscopy to treat symptomatic, acetabular labral tears were enrolled. From this cohort, we extracted a borderline HD group (162 cases). Lateral labral widths were evaluated using preoperative magnetic resonance imaging scans. Clinical data including the modified Harris hip score (mHHS), non-arthritic hip score (NAHS), hip outcome score-activity of daily living (HOS-ADL) score, visual analog scale (VAS) pain score, and Tönnis grade were collected. In addition, patient satisfaction with arthroscopy outcomes was rated. All complications and reoperations were noted.

RESULTS

The mean follow-up time was 87.4 months. The lateral labral width was 7.64 mm in those with normal hips and 7.73 mm in borderline HD patients, respectively (p = 0.870). The Tönnis grade progressed mildly from 0.46 to 0.76 (p = 0.227). At the last follow-up, clinical outcome scores (mHHS, NAHS, and HOS-ADL scores) and the VAS score were improved (p < 0.001). The mean patient satisfaction was scored at 8.2. The reoperation rate was higher in those who underwent labral debridement (25.6%) than labral repair (4.1%).

CONCLUSIONS

The lateral labral width did not differ significantly between the borderline HD group and the nondysplastic control group. Arthroscopy relieved the symptoms of painful borderline HD and did not accelerate osteoarthritis. Therefore, if such patients do not respond to conservative treatment, hip arthroscopy can be considered for further treatment.

Femoroacetabular Impingement and Management of Labral Tears in the Athlete

Femoroacetabular impingement and associated labral tearing is a common source of hip pain in athletes. This article reviews the hip joint anatomy and complex interplay between alterations on the femoral and acetabular sides, in addition to evaluation of soft tissue stabilizers and spinopelvic parameters. Symptom management with a focus on arthroscopic treatment of abnormal bony morphology and labral repair or reconstruction is discussed. In select patients with persistent pain who have failed conservative measures, hip arthroscopy with correction of bony impingement and labral repair or reconstruction has yielded good to excellent results in recreational and professional athletes.

Femoroacetabular impingement: question-driven review of hip joint pathophysiology from asymptomatic skeletal deformity to end-stage osteoarthritis

Femoroacetabular impingement (FAI), together with its two main pathomechanisms, cam and pincer, has become a trending topic since the end of the 1990s. Despite massive academic research, this hip disorder still conceals obscure aspects and unanswered questions that only a question-driven approach may settle. The pathway that leads a FAI asymptomatic morphology through a FAI syndrome to a FAI-related osteoarthritis is little known. Contact mechanics provides a shareable and persuasive perspective: cam FAI is based on shear contact stress at joint level with consequent cartilage wear; pincer FAI, contrariwise, determines normal contact stress between acetabular rim and femoral neck and squeezes the labrum in between, with no cartilage wear for many years from the onset. Pincer prognosis is then far better than cam. As a matter of fact, cartilage wear releases fragments of extracellular matrix which in turn trigger joint inflammation, with consequently worsening lubrication and further enhanced wear. Inflammation pathobiology feeds pathotribology through a vicious loop, finally leading to hip osteoarthritis. The association of cam and pincer, possibly overdiagnosed, is a synergic combination that may damage the joint rapidly and severely. The expectations after FAI surgical correction depend strictly on chondral layer imaging, on time elapsed from the onset of symptoms and on clinic-functional preoperative level. However, preemptive surgical correction is not recommended yet in asymptomatic FAI morphology. LEVEL OF EVIDENCE: V.

Patient-specific chondrolabral contact mechanics in patients with acetabular dysplasia following treatment with peri-acetabular osteotomy

OBJECTIVE

Using a validated, patient-specific finite element (FE) modeling protocol, we evaluated cartilage and labrum (i.e., chondrolabral) mechanics before and after peri-acetabular osteotomy (PAO) to provide insight into the ability of this procedure to improve mechanics in dysplastic hips.

DESIGN

Five patients with acetabular dysplasia were recruited in this case-controlled, prospective study. Models, which included anatomy for bone, cartilage, and labrum, were generated from computed tomography (CT) arthrography scans acquired before and after PAO. Cartilage and labrum contact stress and contact area were quantified overall and regionally. Load supported by the labrum, expressed as a percentage of the total hip force, was analyzed.

RESULTS

Percent cartilage contact area increased post-operatively overall, medially, and superiorly. Peak acetabular contact stress decreased overall, laterally, anteriorly, and superiorly. Average contact stress decreased overall, laterally, anteriorly, and posteriorly. Only average contact stress on the superior labrum and peak labrum stress overall decreased. Load supported by the labrum did not change significantly.

CONCLUSIONS

PAO was efficacious at medializing cartilage contact and reducing cartilage contact stresses, and therefore may minimize deleterious loading to focal cartilage lesions, subchondral cysts, and cartilage delaminations often observed in the lateral acetabulum of dysplastic hips. However, the excessively prominent, hypertrophied labrum of dysplastic hips remains in contact with the femoral head, which continues to load the labrum following PAO. The clinical ramifications of continued labral loading following PAO are not known. However, it is plausible that failure to reduce the load experienced by the labrum could result in end-stage hip OA following PAO.

The Human Pelvis: Variation in Structure and Function During Gait

The shift to habitual bipedalism 4-6 million years ago in the hominin lineage created a morphologically and functionally different human pelvis compared to our closest living relatives, the chimpanzees. Evolutionary changes to the shape of the pelvis were necessary for the transition to habitual bipedalism in humans. These changes in the bony anatomy resulted in an altered role of muscle function, influencing bipedal gait. Additionally, there are normal sex-specific variations in the pelvis as well as abnormal variations in the acetabulum. During gait, the pelvis moves in the three planes to produce smooth and efficient motion. Subtle sex-specific differences in these motions may facilitate economical gait despite differences in pelvic structure. The motions of the pelvis and hip may also be altered in the presence of abnormal acetabular structure, especially with acetabular dysplasia. Anat Rec, 300:633-642, 2017. © 2017 Wiley Periodicals, Inc.

Histological changes of the acetabular labrum in coxarthrosis: labral degeneration and repair

INTRODUCTION

The current study was designed to describe types of histological changes within the acetabular labrum in the advanced stages of coxarthrosis, in patients requiring total hip arthroplasty (THA).

METHODS

77 consecutive patients without systemic disorders or prior hip surgery, scheduled for THA with 3 types of coxarthrosis: avascular necrosis (AVN), idiopathic, and dysplastic coxarthrosis were analysed. Patient's data: age, gender, side of the involvement, duration of the symptoms were recorded, and standard anteroposterior (AP) radiographic views of the pelvis were obtained. During THA procedure the acetabular labrum was harvested and examined histologically and immunohistochemically. The mean chondrocytes number and density were calculated using morphometric techniques.

RESULTS

In 77 analysed acetabular labra the following histological changes were found: heterogenic matrix, foci of granular matrix breakdown, pseudocysts, intralabral c alcifications, chondrocyte apoptosis, inflammatory reaction with lymphocytes infiltration and macrophages infiltration and vascular proliferation with 2 stages of maturation: endothelial cell formation and fully formed blood vessels. The average chondrocytes density was 478 cells in 1 mm2 and significantly decreased with age.

CONCLUSIONS

The acetabular labrum is an important part of the process of degeneration of the hip in osteoarthritis (OA). Vascular formation and cellular infiltration found in the damaged fibrocartilage may represent a labral response to degenerative changes.

Hip Osteoarthritis: Etiopathogenesis and Implications for Management

Highly prevalent among the elderly, hip osteoarthritis (OA) carries a heavy burden of disease. Guidelines for the management of hip OA are often extrapolated from knee OA research, despite clear differences in the etiopathogenesis and response to treatments of OA at these sites. We propose that hip OA requires specific attention separate from other OA phenotypes. Our understanding of the etiopathogenesis of hip OA has seen significant advance over the last 15 years, since Ganz and colleagues proposed femoroacetabular impingement (FAI) as an important etiological factor. This narrative review summarizes the current understanding of the etiopathogenesis of hip OA and identifies areas requiring further research. Therapeutic approaches for hip OA are considered in light of the condition’s etiopathogenesis. The evidence for currently adopted management strategies is considered, especially those approaches that may have disease-modifying potential. We propose that shifting the focus of hip OA research and public health intervention to primary prevention and early detection may greatly improve the current management paradigm.

The influence of cartilage surface topography on fluid flow in the intra-articular gap

Self-lubrication of a diarthrodial joint is largely attributed to interstitial fluid pressurisation. However, the retention of synovial fluid within the intra-articular gap may also contribute to lubrication. Fluid flow in the intra-articular gap between two micro-rough cartilage surfaces was simulated with a three-dimensional numerical model. Representative surface roughness parameters were incorporated and their relative influence on gap flow resistance was quantified. Resistance changes with decreasing gap height were explored. Cartilage surface micro-topography improves the retention of viscous synovial fluid in the gap, through increased resistance to tangential flow. Local asperity contact greatly increases resistance through tortuosity of the flow path.

The contribution of the acetabular labrum to hip joint stability: a quantitative analysis using a dynamic three-dimensional robot model

The acetabular labrum provides mechanical stability to the hip joint in extreme positions where the femoral head is disposed to subluxation. We aimed to quantify the isolated labrum's stabilizing value. Five human cadaveric hips were mounted to a robotic manipulator, and subluxation potential tests were run with and without labrum. Three-dimensional (3D) kinematic data were quantified using the stability index (Colbrunn et al., 2013, "Impingement and Stability of Total Hip Arthroplasty Versus Femoral Head Resurfacing Using a Cadaveric Robotics Model," J. Orthop. Res., 31(7), pp. 1108-1115). Global and regional stability indices were significantly greater with labrum intact than after total labrectomy for both anterior and posterior provocative positions. In extreme positions, the labrum imparts significant overall mechanical resistance to hip subluxation. Regional stability contributions vary with joint orientation.

No regeneration of the human acetabular labrum after excision to bone

BACKGROUND

Treatment options for a symptomatic, torn, irreparable, or completely ossified acetabular labrum are limited to either excision and/or reconstruction with grafts. In a previous animal model, regeneration of the acetabular labrum after excision to the bony rim has been shown. In humans, less is known about the potential of regeneration of the labrum. Recent studies seem to confirm labral regrowth, but it is still unclear if wide excision might be a surgical option in cases where repair is not possible.

QUESTIONS/PURPOSES

The purposes of this study were (1) to determine the extent of acetabular labrum regeneration after excision to the bony rim; and (2) to determine whether this procedure results in higher hip scores.

METHODS

We reviewed all patients treated with surgical dislocation for symptomatic femoroacetabular impingement by a single surgeon at one institution between 2003 and 2008, of whom 14 underwent wide labral excision (of at least 60°) down to bone; we used this approach when there was an absence of reparable tissue. Of these 14, nine were available for voluntary reexamination. The mean age at surgery was 38 ± 9 SD years and the mean followup was 4 ± 1 SD years. All patients consented to a physical examination and an MRI arthrogram, which was evaluated for evidence of new tissue formation by four observers. A modified Harris hip score and the UCLA were recorded.

RESULTS

Regrowth of a structure equivalent to normal labrum was not observed on the MRI arthrograms. Six of nine hips had segmental defects, bone formation was found in five, and the capsule was confluent with the new tissue in six. The mean Harris hip score at latest followup was 83 ± 14, and the mean UCLA score was 6 ± 2.

CONCLUSIONS

Resection of a nonreparable acetabular labrum down to a bleeding bony surface does not stimulate regrowth of tissue that appears to be capable of normal function by MR arthrography, and patients who underwent this procedure had lower hip scores at midterm than previously reported from the same institution for patients undergoing labral repair or sparse débridement. Based on these results, we believe that future studies should evaluate alternatives to reconstructing the labrum, perhaps using ligamentum teres, because resection seems neither to result in regrowth nor the restoration of consistently high hip scores.

Ultrasound imaging of the trapeziometacarpal articular cavity to investigate the presence of intraarticular gas bubbles after chiropractic manipulation

OBJECTIVE

The purpose of this study was to investigate the presence of intraarticular gas bubbles in the trapeziometacarpal joint cavity after chiropractic manipulation with audible cavitation and to assess the state of the gas bubbles after a 20-minute refractory period.

METHODS

This investigation included 18 asymptomatic male and female participants between the ages of 21 and 26 years. High-resolution (15 MHz) sonograms of the trapeziometacarpal articular cavity were obtained by an experienced musculoskeletal ultrasonographer at 3 intervals: premanipulation, within 30 seconds postmanipulation, and at 20 minutes postmanipulation. The sonograms were saved as digital copies for subsequent reports that were correlated with reports compiled during dynamic visualization of the articular cavity. Data were extracted from the reports for analysis.

RESULTS

The premanipulative sonograms showed that 27.78% of joints contained minute gas bubbles, also known as microcavities, within the synovial fluid before the joint was manipulated. The remaining 72.22% of joints contained no intraarticular microcavities. All of the postmanipulative sonograms revealed numerous large conspicuous gas bubbles within the synovial fluid. The postrefractory sonograms showed that, in 66.66% of the synovial fluid, gas bubbles were still visible, whereas the remaining 33.34% had no presence of gas bubbles or microcavities, and the synovial fluid had returned to its premanipulative state.

CONCLUSION

The findings of this study suggest that synovial fluid may contain intraarticular microcavities even before a manipulation is performed. Numerous large intraarticular gas bubbles are formed during manipulation due to cavitation of the synovial fluid and were observed in the absence of an axial distractive load at the time of imaging. In most cases, these gas bubbles remained within the joint for longer than 20 minutes.

The biomechanical case for labral débridement

BACKGROUND

Labral repair is increasingly performed in conjunction with open and arthroscopic surgical procedures used to treat patients with mechanically related hip pain. The current rationale for labral repair is based on restoring the suction-seal function and clinical reports suggesting improved clinical outcome scores when acetabular rim trimming is accompanied by labral repair. However, it is unclear whether available scientific evidence supports routine labral repair.

QUESTIONS/PURPOSES

The questions raised in this review were: (1) does labral repair restore normal histologic structure, tissue permeability, hip hydrodynamics, load transfer, and in vivo kinematics; and (2) does labral repair favorably alter the natural course of femoroacetabular impingement (FAI) treatment or age-related degeneration of the acetabular labrum?

METHODS

An electronic literature search for the keywords acetabular labrum was performed. Three hundred fifty-five abstracts were reviewed and 52 selected for full-text review that described information concerning pertinent aspects of labral formation, development, degeneration, biomechanics, and clinical results of labral repair or resection.

RESULTS

Several clinical studies support labral repair when performed in conjunction with acetabular rim trimming. Little data support or refute the use of routine labral repair for all patients with symptomatic labral damage associated with FAI. It is not known whether or how labral repair affects the natural course of FAI.

CONCLUSIONS

Based on the current understanding of labral degenerative changes associated with mechanical hip abnormalities, the low biologic likelihood of restoring normal tissue characteristics, and mechanical data suggesting minimal consequence from small labral resections, routine labral repair over labral débridement is not supported.

Articular cartilage friction increases in hip joints after the removal of acetabular labrum

The acetabular labrum is believed to have a sealing function. However, a torn labrum may not effectively prevent joint fluid from escaping a compressed joint, resulting in impaired lubrication. We aimed to understand the role of the acetabular labrum in maintaining a low friction environment in the hip joint. We did this by measuring the resistance to rotation (RTR) of the hip, which reflects the friction of the articular cartilage surface, following focal and complete labrectomy. Five cadaveric hips without evidence of osteoarthritis and impingement were tested. We measured resistance to rotation of the hip joint during 0.5, 1, 2, and 3 times body weight (BW) cyclic loading in the intact hip, and after focal and complete labrectomy. Resistance to rotation, which reflects articular cartilage friction in an intact hip was significantly increased following focal labrectomy at 1-3 BW loading, and following complete labrectomy at all load levels. The acetabular labrum appears to maintain a low friction environment, possibly by sealing the joint from fluid exudation. Even focal labrectomy may result in increased joint friction, a condition that may be detrimental to articular cartilage and lead to osteoarthritis.

Role of the acetabular labrum in load support across the hip joint

The relatively high incidence of labral tears among patients presenting with hip pain suggests that the acetabular labrum is often subjected to injurious loading in vivo. However, it is unclear whether the labrum participates in load transfer across the joint during activities of daily living. This study examined the role of the acetabular labrum in load transfer for hips with normal acetabular geometry and acetabular dysplasia using subject-specific finite element analysis. Models were generated from volumetric CT data and analyzed with and without the labrum during activities of daily living. The labrum in the dysplastic model supported 4-11% of the total load transferred across the joint, while the labrum in the normal model supported only 1-2% of the total load. Despite the increased load transferred to the acetabular cartilage in simulations without the labrum, there were minimal differences in cartilage contact stresses. This was because the load supported by the cartilage correlated with the cartilage contact area. A higher percentage of load was transferred to the labrum in the dysplastic model because the femoral head achieved equilibrium near the lateral edge of the acetabulum. The results of this study suggest that the labrum plays a larger role in load transfer and joint stability in hips with acetabular dysplasia than in hips with normal acetabular geometry.

A comprehensive review of hip labral tears

The hip labrum has many functions, including shock absorption, joint lubrication, pressure distribution, and aiding in stability, with damage to the labrum associated with osteoarthritis. The etiology of labral tears includes trauma, femoroacetabular impingement (FAI), capsular laxity/hip hypermobility, dysplasia, and degeneration. Labral tears present with anterior hip or groin pain, and less commonly buttock pain. Frequently, there are also mechanical symptoms including clicking, locking, and giving way. The most consistent physical examination finding is a positive anterior hip impingement test. Because of the vast differential diagnosis and the need for specialized diagnostic tools, labral tears frequently go undiagnosed during an extended period of time. Evaluation usually begins with plain radiographs to assess for dysplasia, degeneration, and other causes of pain. While magnetic resonance imaging (MRI) and computed tomography scans are unreliable for diagnosis, magnetic resonance arthrography (MRA) is the diagnostic test of choice, with arthroscopy being the gold standard. Typically, treatment begins conservatively with relative rest and non-steroid anti-inflammatory agents, with physical therapy (PT) being controversial. Often, surgical treatment is necessary, which entails, arthroscopic debridement of labral tears and surgical repair of associated structural problems.

Acetabular labral tears

Acetabular labral tears rarely occur in the absence of a structural osseous abnormality. Labral tears are frequently associated with lesions of acetabular cartilage such as delamination. Hip arthroscopy is the preferred operative approach in the treatment of labral injuries in the absence of substantial structural osseous abnormalities.

Acetabular labral tears of the hip in women

Acetabular labral tears are a major cause of hip dysfunction in young patients and a primary precursor to hip osteoarthritis. In addition, labral disease more commonly occurs in women and can present with nonspecific symptoms. It is possible to diagnose, quantify, and treat labral tears before the onset of secondary joint deterioration. However, the diagnosis requires a high index of suspicion, special attention to subtle patterns of presentation, and timely consideration for imaging studies. Treatment options are still evolving and include a wide array of nonsurgical and surgical techniques. Treatment should also address secondary dysfunction that can be associated with hip pathology. An initial trial of conservative management is recommended and failure to progress is an indication for surgical consultation.

Quality of life following femoral head-neck osteochondroplasty for femoroacetabular impingement

BACKGROUND

Femoroacetabular impingement has been recently described as a common cause of hip pain and labral tears in young adults. We evaluated the early clinical results and quality of life after osteochondroplasty of the femoral head-neck junction for the treatment of femoroacetabular impingement.

METHODS

Thirty-seven hips in thirty-four patients with persistent hip pain and a mean age of 40.5 years underwent surgical dislocation of the hip and osteochondroplasty of the femoral head-neck junction for the treatment of camtype femoroacetabular impingement. All of the patients had had preoperative evidence of pathological changes in the labrum on imaging. The clinical course and the quality of life were assessed postoperatively.

RESULTS

The mean score on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) increased from 61.2 points preoperatively to 81.4 points at a mean of 3.1 years postoperatively (p < 0.001), the mean University of California at Los Angeles (UCLA) activity score increased from 4.8 to 7.5 points (p < 0.001), the mean Short Form-12 (SF-12) physical component score increased from 37.3 to 45.6 points (p < 0.001), and the mean SF-12 mental component score increased from 46.4 to 51.2 points (p = 0.031). None of the hips underwent additional reconstructive surgery. There were no cases of osteonecrosis. Nine patients underwent screw removal from the greater trochanter because of persistent bursitis. Six of the thirty-four patients were dissatisfied with the outcome.

CONCLUSIONS

Cam-type femoroacetabular impingement is associated with insufficient concavity at the anterolateral head-neck junction and with pathological changes in the labrum. Osteochondroplasty of the femoral head-neck junction following surgical dislocation of the hip joint is safe and effective and can provide a significant improvement in the overall quality of life of most patients.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Disorders of acetabular labrum and articular cartilage in hip dysplasia: evaluation using isotropic high-resolutional CT arthrography with sequential radial reformation

OBJECTIVE

Acetabular labral tear may predispose to adjacent articular cartilage disorder and hip osteoarthritis in patients with hip dysplasia. We evaluated the diagnostic ability of isotropic computed tomography (CT) arthrography with radial reformation technique for detection of acetabular labral and articular cartilage disorders, and evaluate those interactions in hip dysplasia.

METHODS

Forty-one hips in 29 patients with hip dysplasia received CT arthrography with isotropic spatial resolution of 0.5mm. After processing of multiplanar radial reformation over the whole acetabular circumference, frequencies of labral tear and acetabular cartilage disorder were evaluated at six divided zones of the weight-bearing areas. Of the 41 hips, 20 hips underwent arthroscopic examinations, and sensitivity, specificity and accuracy for detecting labral tear and acetabular cartilage disorder by CT arthrography were calculated using the arthroscopic findings as the standard of reference.

RESULTS

The sensitivity, specificity and accuracy of CT arthrography were 97%/87%/92% for labral tear and 88%/82%/85% for acetabular cartilage disorder, respectively, using arthroscopic findings as the reference. The CT arthrography showed significantly higher frequency of labral and acetabular cartilage disorders at the anterior zones. Those zones with labral tear had significantly higher frequency of adjacent cartilage disorder than zones without labral tear.

CONCLUSIONS

Isotropic CT arthrography with radial reformation technique allowed simultaneous, accurate assessment of labral and cartilage disorders in the whole acetabular circumference. Our findings indicated that labral tear is closely associated with adjacent cartilage disorder in hip dysplasia.

Acetabular labral tears

Anterior hip or groin pain is a common complaint for which people are referred for physical therapy, with the hip region being involved in approximately 5% to 9% of injuries in high school athletes.1 Although anterior hip pain is known to result from a number of musculoskeletal and systemic pathologies, a tear of the acetabular labrum is a recent addition to the list that is of particular interest to physical therapists. This mechanically induced pathology is thought to result from excessive forces at the hip joint2,3 and has been proposed as part of a continuum of hip joint disease that may result in articular cartilage degeneration.2 Although the number of recent articles in the orthopedic literature identifying acetabular labral tears as a source of hip pain is increasing, labral tears often evade detection, resulting in a long duration of symptoms, greater than 2 years on average, before diagnosis.4–8 Studies have shown that 22% of athletes with groin pain9 and 55% of patients with mechanical hip pain of unknown etiology2 were found to have a labral tear upon further evaluation. In order to provide the most appropriate intervention for patients with anterior hip or groin pain, physical therapists should be knowledgeable about all of the possible sources and causes of this pain, including a tear of the acetabular labrum and the possible factors contributing to these tears. Therefore, the purpose of this article is to review the anatomy and function of the acetabular labrum and present current concepts on the etiology, clinical characteristics, diagnosis, and treatment of labral tears.

Effects of removal of the acetabular labrum in a sheep hip model

OBJECTIVE

The aim of this study was to learn whether partial resection of the acetabular labrum would lead to degenerative arthritis in an ovine model.

METHODS

A 2 cm segment of labrum was removed from one hip in 18 mature Swiss Alpine sheep and a sham procedure was performed on the opposite side. Animals were permitted ad lib activity until sacrifice at 6, 12 or 24 weeks. The hip joint was removed en bloc, and loaded with a force of one body weight, using a custom device designed to recreate a physiologic joint reaction force. While under load, the joint was plunge frozen, and then fixed by freeze substitution using aldehydes in methanol/acetone solvents. The entire joint was embedded in methacrylate and sectioned in a standardized frontal plane following the reaction force and including the femoral neck and the acetabular fossa. The sections were evaluated for concentricity and evidence of arthrosis. Six hip joints of three sheep with no surgical procedure were loaded with high or low loads and served as non-surgical controls.

RESULTS

Degenerative changes were present in all surgical hips, but the changes were symmetrical and mild. In 16 of 18 hips, the labrum regenerated to the extent that dense fibrous scar extending from the surgically denuded origin filled the defect.

CONCLUSION

Resection of the labrum does not cause rapid degeneration or altered stability of the sheep hip.

Hydrostatic pressurization and depletion of trapped lubricant pool during creep contact of a rippled indenter against a biphasic articular cartilage layer

This study presents an analysis of the contact of a rippled rigid impermeable indenter against a cartilage layer, which represents a first simulation of the contact of rough cartilage surfaces with lubricant entrapment. Cartilage was modeled with the biphasic theory for hydrated soft tissues, to account for fluid flow into or out of the lubricant pool. The findings of this study demonstrate that under contact creep, the trapped lubricant pool gets depleted within a time period on the order of seconds or minutes as a result of lubricant flow into the articular cartilage. Prior to depletion, hydrostatic fluid load support across the contact interface may be enhanced by the presence of the trapped lubricant pool, depending on the initial geometry of the lubricant pool. According to friction models based on the biphasic nature of the tissue, this enhancement in fluid load support produces a smaller minimum friction coefficient than would otherwise be predicted without a lubricant pool. The results of this study support the hypothesis that trapped lubricant decreases the initial friction coefficient following load application, independently of squeeze-film lubrication effects.