The material properties of the bovine acetabular labrum

Structure, composition and anisotropic swelling of the bovine acetabular labrum

The fibro-cartilaginous labrum surrounds the acetabular rim and is important for hip joint stability and sealing. Sealing may be enhanced by swelling pressure within the normal labrum. Swelling of the degenerated or torn labrum might occur and potentially contribute to the development of osteoarthritis, through altered load transmission. This study aimed to characterize the three-dimensional swelling behaviour, the collagen fiber orientation and spatial proteoglycan distribution of the bovine acetabular labrum. Specimens were harvested from bovine donors (192-652 days, male, n = 6 donors). Structure was analyzed by scanning electron microscopy, histology, and dimethylmethylene blue assay. Specimen dimensions were measured before and after incubation in phosphate buffered saline to assess the swelling. Results showed that the articulating surface is composed of a collagen mesh network. Collagen fiber bundles showed a low degree of alignment close to the surface and were circumferentially aligned in the deep tissue. Proteoglycans were identified clustered between the collagen bundles. Glycosaminoglycan content was 10 x lower than that of cartilage (23.1 ± 6.4 compared to 299.5 ± 19.1 μg/mg dry weight) with minor regional differences. Specimens swelled significantly more in the orthogonal direction (swelling ratio 124.7 ± 10.2%) compared to the swelling parallel to the articulating surface (108.8 ± 6.1% and 102.8 ± 4.1%). In the deep tissue, swelling was also restricted in the main collagen fiber bundle direction (circumferentially), with a swelling ratio of 109.5 ± 4.0% in the main fiber bundle direction compared to 126.8 ± 7.3 % and 122.3 ± 5.8% radially. The findings demonstrate that the labrum shows anisotropic swelling properties, which reflect the anisotropy in the tissue structure and inter-fiber localisation of proteoglycans.

Young Bovine Hip Model for Hip Arthroscopy Training

Hip arthroscopy is associated with risks for complications, especially for novice surgeons. The present article reports use of a young bovine hip as a valid educational tool for key components of arthroscopic treatment of femoroacetabular impingement syndrome, ie, labrum repair and cam excision. The purpose of this Technical Note is to describe the steps of arthroscopic femoroacetabular impingement treatment in the bovine hip.

Can the Acetabular Labrum Be Reconstructed With a Meniscal Allograft? An In Vivo Pig Model

BACKGROUND

No single graft type has been shown to have a benefit in acetabular labral reconstruction. The native labrum and lateral meniscus share many similarities, suggesting that the meniscus may be a promising source of graft material in labral reconstruction.

QUESTIONS/PURPOSES

Using a pig model, we sought to evaluate the healing process of fresh-frozen meniscus allograft for acetabular reconstruction by assessing (1) MRI and macroscopic observations of the meniscus allograft; (2) histologic appearance and immunohistologic evaluation of the meniscus allograft, native meniscus, and labrum; (3) microscopic assessment of the native labrum and meniscus via scanning electron microscopy; and (4) biomechanical assessment of tensile properties.

METHODS

Twelve skeletally mature male miniature Bama pigs (24 hips) were randomly divided into two groups: labral defect group (control) and lateral meniscus allograft group. The selection of Bama pig specimens was based on the similarity of their acetabular labrum to that of the human acetabular labrum, characterized by the presence of fibrocartilage-like tissue lacking blood vessels. The pigs underwent bilateral hip surgery. Briefly, a 1.5-cm-long section was resected in the anterior dorsal labrum, which was left untreated or reconstructed using an allogeneic lateral meniscus. The pigs were euthanized at 12 and 24 weeks postoperatively, and then evaluated by macroscopic observations and MRI measurement to assess the extent of coverage of the labral defect. We also performed a histologic analysis and immunohistologic evaluation to assess the composition and structure of meniscus allograft, native labrum, and meniscus, as well as scanning electron microscopy assessment of the microstructure of the native labrum and meniscus and biomechanical assessment of tensile properties.

RESULTS

Imaging measurement and macroscopic observations revealed that the resected area of the labrum was fully filled in the lateral meniscus allograft group, whereas in the control group, the labral defect remained at 24 weeks. The macroscopic scores of the meniscus allograft group (8.2 ± 0.8) were higher than those of the control groups (4.8 ± 1.0) (mean difference 3.3 [95% CI 1.6 to 5.0]; p < 0.001). Moreover, in the meniscus allograft group, histologic assessment identified fibrocartilage-like cell cluster formation at the interface between the graft and acetabulum; cells and fibers arranged perpendicularly to the acetabulum and tideline structure that were similar to those of native labrum could be observed at 24 weeks. Immunohistochemical results showed that the average optical density value of Type II collagen at the graft-acetabulum interface was increased in the meniscus allograft group at 24 weeks compared with at 12 weeks (0.259 ± 0.031 versus 0.228 ± 0.023, mean difference 0.032 [95% CI 0.003 to 0.061]; p = 0.013). Furthermore, the tensile modulus of the lateral meniscus allograft was near that of the native labrum at 24 weeks (54.7 ± 9.9 MPa versus 63.2 ± 11.3 MPa, mean difference -8.4 MPa [95% CI -38.3 to 21.4]; p = 0.212).

CONCLUSION

In a pig model, lateral meniscus allografts fully filled labral defects in labral reconstruction. Regeneration of a fibrocartilage transition zone at the graft-acetabulum interface was observed at 24 weeks.

CLINICAL RELEVANCE

The use of an autograft meniscus for labral reconstruction may be a viable option when labral tears are deemed irreparable. Before its clinical implementation, it is imperative to conduct a comparative study involving tendon grafts, which are extensively used in current clinical practice.

The acetabular labrum tissue shows unique transcriptome signatures compared to cartilage and responds to combined cyclic compression and surface shearing

The labrum is a fibrocartilaginous ring surrounding the acetabulum. Loss of labrum function contributes to the degeneration of the hip joint, leading to osteoarthritis. Successful labrum restoration requires profound knowledge about the tissue being replaced. The aim of this study was to characterize the transcriptome and the mechanobiological function of the labrum. RNA-seq was performed to compare the transcriptome of bovine labrum against articular cartilage tissue. Differential expression and gene ontology (GO) term pathway analysis were applied using the SUSHI framework. Bovine labrum explants were cultured for 5 days with / without mechanical loading and targeted gene expression was analyzed by real time quantitative polymerase chain reaction. More than 6'000 genes were significantly differentially expressed in the labrum compared to cartilage. Up- and downregulated genes were associated with the GO term extracellular matrix organization. The study established an extracellular matrix gene expression profile of healthy labrum tissue and identified significantly upregulated extracellular matrix related genes compared to cartilage tissue. Mechanical loading significantly upregulated aggrecan (ACAN), cartilage oligomeric matrix protein (COMP), fibronectin (FN1) and proteoglycan 4 (PRG4). MMP1/3/9 and IL6, which were upregulated by an inflammatory stimulus (IL-1b), were statistically unaffected by the loading, although IL6 was upregulated in each donor immediately after the loading. Unique ECM related features may guide the development of labrum tissue-engineering solutions. Despite the transcriptome differences between labrum and cartilage tissue, gene expression response to mechanical loading showed similarities with previously reported responses in cartilage, indicating a preserved tissue adaptation mechanism to mechanical loading. Running title: Acetabular Labrum Mechanobiology.

The Cartilage Protective Effect of Labrum Reconstruction Using Meniscus Allograft Compared with Labrum Resection in a Porcine Model

PURPOSE

This study aimed to verify the femoral head cartilage protective effect of labral reconstruction in a porcine model.

METHODS

Twelve pigs (24 hips) were divided into 3 groups: labrum defect group, lateral meniscus (LM) allograft group, and LM allograft wrapped with acellular peritoneum matrix (LM-APM) group before undergoing bilateral hip surgery. The pigs were sacrificed at 12 and 24 weeks postoperatively, while the femoral head cartilage was retrieved and then subjected to imaging measurement, macroscopic observations, and biomechanical and histological assessment.

RESULTS

Imaging measurement and macroscopic observations revealed that the defect area of the labrum was filled in LM and LM-APM allograft groups after 24 weeks, whereas the labrum defect remained at 24 weeks in the control group. The femoral head cartilage corresponding to the area of labral resection in the labral defect group had worse macroscopic Osteoarthritis Research Society International (OARSI) scores, uneven and discontinuous cartilage on hematoxylin and eosin (H&E) staining and Safranin O staining, decreased histopathology OARSI Osteoarthritis Cartilage Histopathology Assessment System (OOCHAS) scores, and decreased elastic modulus and hardness at 12 and 24 weeks after surgery compared with the meniscus allograft groups.

CONCLUSION

This study demonstrated that the LM allograft with or without APM for labral reconstruction had a chondroprotective effect on the femoral head in a porcine model.

Magnetic Resonance Arthrographic Findings After Hip Labrum Resection Versus Refixation

The aim of this study was to evaluate whether new tissue formation occurs after labral debridement/excision, and, if so, which morphological features are typical for a neo-labrum. The authors further compared the findings after labrum resection with those seen after labrum refixation. Patients with femoroacetabular impingement who underwent hip arthroscopy or surgical hip dislocation to address a labrum pathology were retrospectively included, and postoperative magnetic resonance arthrography studies were assessed. Forty-two patients had undergone either labrum resection (n=25) or refixation (n=17), performed arthroscopically (47.6%) or via surgical hip dislocation (52.4%). In the subgroup of patients after debridement/resection, there was anterosuperior/superior scar tissue in 83.5%, with amorphous configuration in 92%, irregular surface in approximately two-thirds of the cases, and a mean±SD thickness of 7.0±2.7 mm. A labrum-like shape of the scar plate was seen in 7.7%. Regarding the subgroup of patients who had undergone labral refixation, an irregular or rounded labrum shape was noted in 26.5% and 51.3% of cases, respectively, with a triangular shape in less than one-fourth of cases. Labrum re-tears (35.7%) were mainly observed at the base (71.7%), rather than within the labral substance (28.4%). New tissue formation can be observed in the majority of cases after excision of the hip labrum, with amorphous and irregular surface configuration compared with a native labrum. This new tissue should therefore be referred to as scar tissue rather than as neo-labrum. Whether scar tissue is inferior to a refixed labrum needs to be further elucidated in follow-up studies. [Orthopedics. 2021;44(4):e607-e613.].

Acetabular labral reconstruction with medial meniscal allograft: preliminary results of a new surgical technique

PURPOSE

Reconstruction of the acetabular labrum during femoroacetabular impingement (FAI) surgery is accepted when the labrum is deficient and irreparable. Here we describe a novel technique using fresh-frozen medial meniscal allograft for labral reconstruction during surgical hip dislocation for correction of pincer FAI due to acetabular overcoverage.

METHODS

The results from seven hips (six patients) that underwent this procedure with 1 year minimum follow-up, and radiographs are presented.

RESULTS

Six of the seven hips had improvements in pain, hip flexion, hip abduction, and Merle d'Aubigné-Postel scores. Only one patient with pre-existing osteoarthritis underwent reoperation with conversion to total hip arthroplasty. All digastric trochanteric osteotomies healed, and there were no cases of femoral head osteonecrosis or progression of Tönnis grades.

CONCLUSIONS

The medial meniscus is a morphologically and clinically suitable option for labral reconstruction and effectively restores the hip fluid seal.

Architecture of the Short External Rotator Muscles of the Hip

Background

Muscle architecture, or the arrangement of sarcomeres and fibers within muscles, defines functional capacity. There are limited data that provide an understanding of hip short external rotator muscle architecture. The purpose of this study was thus to characterize the architecture of these small hip muscles.

Methods

Eight muscles from 10 independent human cadaver hips were used in this study (n = 80 muscles). Architectural measurements were made on pectineus, piriformis, gemelli, obturators, quadratus femoris, and gluteus minimus. Muscle mass, fiber length, sarcomere length, and pennation angle were used to calculate the normalized muscle fiber length, which defines excursion, and physiological cross-sectional area (PCSA), which defines force-producing capacity.

Results

Gluteus minimus had the largest PCSA (8.29 cm²) followed by obturator externus (4.54 cm²), whereas superior gemellus had the smallest PCSA (0.68 cm²). Fiber lengths clustered into long (pectineus - 10.38 cm and gluteus minimus - 10.30 cm), moderate (obturator internus - 8.77 cm and externus - 8.04 cm), or short (inferior gemellus - 5.64 and superior gemellus - 4.85). There were no significant differences among muscles in pennation angle which were all nearly zero. When the gemelli and obturators were considered as a single functional unit, their collective PCSA (10.00 cm²) exceeded that of gluteus minimus as a substantial force-producing group.

Conclusions

The key findings are that these muscles have relatively small individual PCSAs, short fiber lengths, and low pennation angles. The large collective PCSA and short fiber lengths of the gemelli and obturators suggest that they primarily play a stabilizing role rather than a joint rotating role.

The role of the labrum in early treatment of unstable developmental dysplasia of the hip

The objective of the paper is to analyse the role of the labrum with particular attention to its morphological changes in unstable dysplastic hips during treatment.

Between January 2013 and December 2015, data were collected on 86 unstable, dysplastic hips, which were divided into type D (n = 13), type III (n = 49) and type IV (n = 24). The labrum was evaluated with ultrasound examination (US) for echogenicity and dimensions with inter-/intra-observer tests comparing the US images at diagnosis and at the end of treatment. Statistical analysis was performed.

At the end of treatment of unstable, dysplastic hips, the labrum was more echogenic with a frequency of 97% and was larger with a frequency of 96%.

The labrum has an active stabilizing role in unstable dysplastic hips and it undergoes a statistically significant increase of echogenicity and dimensions after treatment.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180053

Hip chondrolabral mechanics during activities of daily living: Role of the labrum and interstitial fluid pressurization

Osteoarthritis of the hip can result from mechanical factors, which can be studied using finite element (FE) analysis. FE studies of the hip often assume there is no significant loss of fluid pressurization in the articular cartilage during simulated activities and approximate the material as incompressible and elastic. This study examined the conditions under which interstitial fluid load support remains sustained during physiological motions, as well as the role of the labrum in maintaining fluid load support and the effect of its presence on the solid phase of the surrounding cartilage. We found that dynamic motions of gait and squatting maintained consistent fluid load support between cycles, while static single-leg stance experienced slight fluid depressurization with significant reduction of solid phase stress and strain. Presence of the labrum did not significantly influence fluid load support within the articular cartilage, but prevented deformation at the cartilage edge, leading to lower stress and strain conditions in the cartilage. A morphologically accurate representation of collagen fibril orientation through the thickness of the articular cartilage was not necessary to predict fluid load support. However, comparison with simplified fibril reinforcement underscored the physiological importance. The results of this study demonstrate that an elastic incompressible material approximation is reasonable for modeling a limited number of cyclic motions of gait and squatting without significant loss of accuracy, but is not appropriate for static motions or numerous repeated motions. Additionally, effects seen from removal of the labrum motivate evaluation of labral reattachment strategies in the context of labral repair.

Changes in chondrolabral mechanics, coverage, and congruency following peri-acetabular osteotomy for treatment of acetabular retroversion: A patient-specific finite element study

Using a validated finite element (FE) protocol, we quantified cartilage and labrum mechanics, congruency, and femoral coverage in five male patients before and after they were treated for acetabular retroversion with peri-acetabular osteotomy (PAO). Three-dimensional models of bone, cartilage, and labrum were generated from computed tomography (CT) arthrography images, acquired before and after PAO. Walking, stair-ascent, stair-descent, and rising from a chair were simulated. Cartilage and labrum contact stress, contact area, and femoral coverage were calculated overall and regionally. Mean congruency (average of local congruency values for FE nodes in contact) and peak congruency (most incongruent node in contact) were calculated overall and regionally. Load supported by the labrum was represented as a raw change in the ratio of the applied force transferred through the labrum and percent change following surgery (calculated overall only). Considering all activities, following PAO, mean acetabular cartilage contact stress increased medially, superiorly, and posteriorly; peak stress increased medially and posteriorly. Peak labrum stresses decreased overall and superiorly. Acetabular contact area decreased overall and laterally, and increased medially. Labral contact area decreased overall, but not regionally. Load to the labrum decreased. Femoral head coverage increased overall, anterolaterally, and posterolaterally, but decreased anteromedially. Mean congruency indicated the hip became less congruent overall, anteriorly, and posteriorly; peak congruency indicated a less congruent joint posteriorly.

CLINICAL RELEVANCE

Medialization of contact and reductions in labral loading following PAO may prevent osteoarthritis, but this procedure increases cartilage stresses, decreases contact area, and makes the hip less congruent, which may overload cartilage. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2567-2576, 2017.

Does duration of symptoms affect clinical outcome after hip arthroscopy for labral tears? Analysis of prospectively collected outcomes with minimum 2-year follow-up

Limited research exists on the possible association between duration of symptoms and clinical outcomes following hip arthroscopy for labral tears. The purpose of this study was to evaluate whether duration of symptoms affected clinical and patient-reported outcome (PRO) scores following hip arthroscopy for labral tears. From 2008 to 2011, data were collected prospectively on all patients undergoing primary hip arthroscopy for labral tears. Workers' compensation cases, dysplasia cases and patients with previous ipsilateral hip surgeries were excluded. A total of 738 patients were identified with a minimum of 2-year follow-up, and clinical and PRO data were available for 680 patients. Uni- and multivariate analyses were performed to determine the relationship between duration of symptoms along with other variables and PROs. Overall, patients experienced significant improvements in all clinical and PRO scores. Results of univariate analysis revealed that all PROs were negatively associated with increasing Log₁₀ months of symptoms as were pain and satisfaction scores. During multivariate analyses, increasing Log₁₀ months of symptoms, age, body mass index and trauma were all negatively associated with PROs (P  < 0.05). Our study demonstrates that clinical and PRO scores were negatively associated with increasing duration of symptoms prior to hip arthroscopy for treatment of labral tears. Although this implies that delay in treatment may adversely affect outcome, conservative treatment remains the gold standard first line of treatment. Surgeons should incorporate this information into their treatment algorithm to maximize patient outcomes following treatment for labral tears. Level of evidence: Level IV, prospective case series.

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.

Finite element analysis of mechanical behavior of human dysplastic hip joints: a systematic review

Developmental dysplasia of the hip (DDH) is a common condition predisposing to osteoarthritis (OA). Especially since DDH is best identified and treated in infancy before bones ossify, there is surprisingly a near-complete absence of literature examining mechanical behavior of infant dysplastic hips. We sought to identify current practice in finite element modeling (FEM) of DDH, to inform future modeling of infant dysplastic hips. We performed multi-database systematic review using PRISMA criteria. Abstracts (n = 126) fulfilling inclusion criteria were screened for methodological quality, and results were analyzed and summarized for eligible articles (n = 12). The majority of the studies modeled human adult dysplastic hips. Two studies focused on etiology of DDH through simulating mechanobiological growth of prenatal hips; we found no FEM-based studies in infants or children. Finite element models used either patient-specific geometry or idealized average geometry. Diversities in choice of material properties, boundary conditions, and loading scenarios were found in the finite-element models. FEM of adult dysplastic hips demonstrated generally smaller cartilage contact area in dysplastic hips than in normal joints. Contact pressure (CP) may be higher or lower in dysplastic hips depending on joint geometry and mechanical contribution of labrum (Lb). FEM of mechanobiological growth of prenatal hip joints revealed evidence for effects of the joint mechanical environment on formation of coxa valga, asymmetrically shallow acetabulum and malformed femoral head associated with DDH. Future modeling informed by the results of this review may yield valuable insights into optimal treatment of DDH, and into how and why OA develops early in DDH.

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.

Modelling the failure precursor mechanism of lamellar fibrous tissues, example of the annulus fibrosus

The aims of this study were to assess the damage and failure strengths of lamellar fibrous tissues, such as the anterior annulus fibrosus (AF), and to develop a mathematical model of damage propagation of the lamellae and inter-lamellar connections. This level of modelling is needed to accurately predict the effect of damage and failure induced by trauma or clinical interventions. 26 ovine anterior AF cuboid specimens from 11 lumbar intervertebral discs were tested in radial tension and mechanical parameters defining damage and failure were extracted from the in-vitro data. Equivalent 1D analytical models were developed to represent the specimen strength and the damage propagation, accounting for the specimen dimensions and number of lamellae. Model parameters were calibrated on the in-vitro data. Similar to stiffness values reported for other orientations, the outer annulus was found stronger than the inner annulus in the radial direction, with failure at higher stress values. The inner annulus failed more progressively, showing macroscopic failure at a higher strain value. The 1D analytical model of damage showed that lamellar damage is predominant in the failure mechanism of the AF. The analytical model of the connections between lamellae allowed us to represent separately damage processes in the lamellae and the inter-lamellar connections, which cannot be experimentally tested individually.

Biomechanical Performance of Hip Labral Repair Techniques

PURPOSE

To determine the strength of various suture techniques and the impact of suture passer size on cyclically loaded hip labra.

METHODS

We assigned 63 bovine hip labra to 9 simple knotless suture technique groups using OrthoCord suture: (1) penetrating grasper (2.6 mm)-placed horizontal mattress, (2) penetrating grasper-placed vertical mattress, (3) SutureLasso (1.8 mm)-placed vertical mattress, (4) penetrating grasper-placed oblique repair, (5) penetrating grasper-placed vertical mattress plus radiofrequency, (6) SutureLasso-placed horizontal mattress, (7) SutureLasso-placed oblique mattress, (8) SutureLasso-placed horizontal mattress plus radiofrequency, and (9) SutureLasso-placed oblique mattress plus radiofrequency. After 20 cycles of uniaxial tensile loading (5 to 80 N), destructive testing was performed.

RESULTS

Penetrating grasper-placed horizontal mattress sutures showed lower ultimate failure loads than vertical and oblique mattress sutures (P < .05). Penetrating grasper-placed vertical mattress sutures had higher peak-to-peak displacement than SutureLasso-placed vertical mattress sutures (P = .04). SutureLasso-placed oblique mattress sutures had a higher ultimate load (P < .01) and stiffness (P = .04) than SutureLasso-placed horizontal mattress sutures. SutureLasso-placed horizontal mattress sutures had lower cyclic elongation than penetrating grasper-placed horizontal mattress sutures (P = .01) and lower ultimate load (P < .01) and stiffness than SutureLasso-placed vertical mattress sutures (P < .01). Horizontal mattress sutures with radiofrequency had a higher ultimate load (P = .02), stiffness, and cyclic elongation (P < .01) than without radiofrequency.

CONCLUSIONS

A horizontal mattress hip labrum stitch shows a lower ultimate failure load than vertical or oblique mattress stitches. Smaller-diameter suture-passing devices show less cyclic displacement and elongation than larger-diameter devices. Radiofrequency labral treatment does not alter vertical stitch strength but does alter horizontal mattress stitch strength.

CLINICAL RELEVANCE

Vertical and oblique stitches are stronger than horizontal stitches. A 1.8-mm passing device shows a better cyclic loading performance than a 2.6-mm device.

Clinical and radiographical results of labral reconstruction

Treatment of femoroacetabular impingement (FAI) includes correction of underlying bony deformities. Labrum preservation is recommended whenever possible. In hips, where the labrum is missing or damaged beyond preservation, labral reconstruction is an option to restore labral seal. Between 2008 and 2011, 84 hips underwent treatment for FAI by means of a surgical hip dislocation. In 13 of these hips (11 patients), the severely damaged or missing labrum was reconstructed with ligamentum capitis femoris. Pre- and postoperative radiographic and clinical data were analysed with a mean follow-up of 38 months (range: 19–65 months). Clinical outcome was determined with Oxford hip score (OHS) and overall satisfaction, rest and load pain with a visual analogue scale (VAS; 0–100). Clinical outcome was compared with a control group where labral refixation was performed. Mean OHS improved significantly (P ≤ 0.001) from 29 (SD 8) to 44 (SD 4). Overall satisfaction with the hip increased significantly (P = 0.002) from 44 (SD 35) to 87 (SD 15). Mean VAS for rest pain decreased significantly (P = 0.0004) from 45 (SD 35) to 5 (SD 7) as well as for load pain (P = 0.0007) from 59 (SD 26) to 16 (SD 19). There were no significant differences between the two groups. Reconstruction of the acetabular labrum with ligamentum capitis femoris yields good clinical results. Technical superiority of open labral reconstruction may explain the unexpected, excellent outcome.

Assessment of cartilage contact pressure and loading in the hip joint during split posture

PURPOSE

Given the crucial role of the mechanical behavior in the degenerative process of the hip joint, analyzing the contact mechanics in the articular layers during physical activities could contribute to understanding the pathology. Indeed, the development process of hip osteoarthritis generally evolves over a long time period, and therefore analyzing the mechanical behavior of the hip joint during extreme repetitive movements will be helpful to analyze degeneration causes. The aim of the study was to investigate the link between the excessive movements and the development of hip osteoarthritis.

METHODS

To individualize the analysis, we used a subject-specific and noninvasive approach based on finite element analysis and magnetic resonance imaging (MRI) data. The contact pressure distribution and loading conditions on the acetabular cartilage were assessed on eleven professional dancer subjects performing a split movement. This movement is frequently practiced (repetitive) by dancers during their daily exercises. Moreover, split postures are mostly characterized by high anatomical angles with subluxation (excessive). To ensure the motion accuracy, MRI data of the subjects were acquired in neutral and split positions performed inside the MRI scanner. Based on the reconstructed bone models from the MRI data, a motion tracking approach was used to compute the transformation between the two poses. To evaluate the contact during the split movement and to quantify the role of the labrum in the hip joint mechanics, additional simulations of two daily activities (walking and stand-up) were performed. Finally, a clinical study based on morphological and radiological analysis of the subjects was performed and validated by orthopedic surgeons and radiological experts to evaluate the proposed approach.

RESULTS

The reconstructed split movement was characterized by high anatomical angles with a subluxation on the left hip. Consequently, strong deformations and pressures were observed during the simulation. The comparison of the simulation results of split posture and daily activities showed higher pressure and lower contact area during extreme movements. Moreover, the presence of labrum absorbed part of load and consequently decreased the predicted contact pressure and contact area on the acetabular cartilage.

CONCLUSION

The comparison of the simulation results of the split posture and daily activities, as well as the correlation between the results of the analysis on extreme movement results and the clinical analysis performed by medical experts, strongly suggests that repetitive extreme movement could lead to early hip osteoarthritis.

Arthroscopic treatment of femoroacetabular impingement: minimum five-year follow-up

PURPOSE

To evaluate the clinical outcomes of an arthroscopic treatment of femoroacetabular impingement at a minimum of a five-year follow-up.

METHODS

A case series with 24 subjects (26 hips) was conducted. Subjects that were submitted to an arthroscopic procedure for the treatment of femoroacetabular impingement, at a minimum of five years, were evaluated. Subjects completed the modified Harris Hip Score (mHHS), the pain numeric rating scale and a general questionnaire accessing sports practice and satisfaction.

RESULTS

Twenty-one of the 24 subjects (87.5%) were male and the average age at the time of surgery was 34.6 ± 9.5 years old (range 13-51). Of the 27 subjects submitted to hip arthroscopy, three (11.1%) could not be contacted. Follow-up was 6.1 ± 0.8 years, and at this time the average mHHS was 90.6 ± 11.6. Pain numeric rating scale was 2.6 ± 1.9 and 11 hips (42.3%) reported no pain. Of the 14 subjects that complained of hip pain during sports activities prior to surgery, 10 (71.4%) returned to normal sports activities while four (28.6%) subjects could not return to preoperative activities. Three patients had to be submitted to a new surgical procedure. All 24 subjects were satisfied with their procedure and would repeat it if necessary.

CONCLUSIONS

Arthroscopic treatment of femoroacetabular impingement, at five years follow-up, revealed good results in terms of improved function, pain relief and satisfaction.

Tensile properties of the human acetabular labrum and hip labral reconstruction grafts

BACKGROUND

In cases where the acetabular labrum is severely damaged and irreparable, labral reconstructions are becoming an increasingly preferred means of preserving the fluid seal effect of the labrum. However, the graft that most closely replicates the biomechanical properties of the native labrum remains undetermined.

PURPOSE

To characterize the tensile properties and geometry of the labrum, as well as iliotibial band, semitendinosus, gracilis, and anterior tibialis grafts.

STUDY DESIGN

Controlled laboratory study.

METHODS

Five graft groups--(1) acetabular labrum, (2) iliotibial band, (3) semitendinosus, (4) gracilis, and (5) anterior tibialis--with 8 specimens per group were tested. Grafts were tested using a materials testing system in response to a stepwise sinusoidal cyclic loading protocol. Uniaxial tensile loads were initially applied from 20 to 50 N for 100 cycles at 0.5 Hz, followed by incremental increases of 50 N in the upper force every 100 cycles until failure or successful completion of 100 cycles at 300 N. This protocol was designed to be representative of progressive loading experienced during rehabilitation. Cyclic displacement was recorded after 100 (50 N), 200 (100 N), 300 (150 N), 400 (200 N), 500 (250 N), and 600 (300 N) cycles.

RESULTS

The mean elongation (95% CI) after 100 cycles from 20 to 50 N was similar for all groups: acetabular labrum, 0.68 mm (0.57-0.78 mm); iliotibial band, 0.68 mm (0.47-0.89 mm); semitendinosus, 0.68 mm (0.51-0.84 mm); gracilis, 0.62 mm (0.46-0.79 mm); and anterior tibialis, 0.66 mm (0.58-0.73 mm). After 100 cycles from 20 to 300 N (600 cycles total), the mean elongation of the labrum was 4.53 mm (3.71-5.35 mm), and the mean elongations of the iliotibial band, semitendinosus, gracilis, and anterior tibialis were 4.65 mm (3.23-6.07 mm), 4.41 mm (3.45-5.36 mm), 5.12 mm (3.09-7.16 mm), and 5.33 mm (4.40-6.25 mm), respectively.

CONCLUSION

All tested grafts and the acetabular labrum exhibited similar cyclic elongation behavior in response to simulated physiologic forces. In addition, differences in variability in both elongation and geometry existed for all graft types.

CLINICAL RELEVANCE

All tested grafts can be considered viable acetabular labrum reconstruction graft options.

Finite element prediction of transchondral stress and strain in the human hip

Cartilage fissures, surface fibrillation, and delamination represent early signs of hip osteoarthritis (OA). This damage may be caused by elevated first principal (most tensile) strain and maximum shear stress. The objectives of this study were to use a population of validated finite element (FE) models of normal human hips to evaluate the required mesh for converged predictions of cartilage tensile strain and shear stress, to assess the sensitivity to cartilage constitutive assumptions, and to determine the patterns of transchondral stress and strain that occur during activities of daily living. Five specimen-specific FE models were evaluated using three constitutive models for articular cartilage: quasilinear neo-Hookean, nonlinear Veronda Westmann, and tension-compression nonlinear ellipsoidal fiber distribution (EFD). Transchondral predictions of maximum shear stress and first principal strain were determined. Mesh convergence analysis demonstrated that five trilinear elements were adequate through the depth of the cartilage for precise predictions. The EFD model had the stiffest response with increasing strains, predicting the largest peak stresses and smallest peak strains. Conversely, the neo-Hookean model predicted the smallest peak stresses and largest peak strains. Models with neo-Hookean cartilage predicted smaller transchondral gradients of maximum shear stress than those with Veronda Westmann and EFD models. For FE models with EFD cartilage, the anterolateral region of the acetabulum had larger peak maximum shear stress and first principal strain than all other anatomical regions, consistent with observations of cartilage damage in disease. Results demonstrate that tension-compression nonlinearity of a continuous fiber distribution exhibiting strain induced anisotropy incorporates important features that have large effects on predictions of transchondral stress and strain. This population of normal hips provides baseline data for future comparisons to pathomorphologic hips. This approach can be used to evaluate these and other mechanical variables in the human hip and their potential role in the pathogenesis of osteoarthritis (OA).

The state of the art in arthroscopic hip surgery

Hip arthroscopy is among the most rapidly evolving arthroscopic techniques in the last decade and offers the benefits of being both a minimally invasive procedure and an excellent diagnostic tool. Improvements in instrumentation and surgical skills have advanced our ability to accurately diagnose and treat various conditions of the hip joint, and hip arthroscopy has elucidated several pathologies that cause disabling symptoms. Many of these conditions were previously unrecognized and left untreated. The indications for hip arthroscopy include the management of early osteoarthritis, synovial disorders (e. g., synovial osteochondromatosis), labral tears, chondral lesions, and femoroacetabular impingement (FAI), which is increasingly recognized as a disorder that can lead to the development of early cartilage and labral injury. A better understanding of hip arthroscopy, including the anatomy, improved surgical techniques, indications, and complications of the procedure, is essential for its success. This review article discusses the state of the art of arthroscopic hip surgery.

A three-dimensional finite element model for biomechanical analysis of the hip

The objective of this study was to construct a three-dimensional (3D) finite element model of the hip. The images of the hip were obtained from Chinese visible human dataset. The hip model includes acetabular bone, cartilage, labrum, and bone. The cartilage of femoral head was constructed using the AutoCAD and Solidworks software. The hip model was imported into ABAQUS analysis system. The contact surface of the hip joint was meshed. To verify the model, the single leg peak force was loaded, and contact area of the cartilage and labrum of the hip and pressure distribution in these structures were observed. The constructed 3D hip model reflected the real hip anatomy. Further, this model reflected biomechanical behavior similar to previous studies. In conclusion, this 3D finite element hip model avoids the disadvantages of other construction methods, such as imprecision of cartilage construction and the absence of labrum. Further, it provides basic data critical for accurately modeling normal and abnormal loads, and the effects of abnormal loads on the hip.

Patient-specific analysis of cartilage and labrum mechanics in human hips with acetabular dysplasia

BACKGROUND

Acetabular dysplasia is a major predisposing factor for development of hip osteoarthritis (OA), and may result from alterations to chondrolabral loading. Subject-specific finite element (FE) modeling can be used to evaluate chondrolabral mechanics in the dysplastic hip, thereby providing insight into mechanics that precede OA.

OBJECTIVE

To evaluate chondrolabral contact mechanics and congruency in dysplastic hips and normal hips using a validated approach to subject-specific FE modeling.

METHODS

FE models of ten subjects with normal acetabula and ten subjects with dysplasia were constructed using a previously validated protocol. Labrum load support, and labrum and acetabular cartilage contact stress and contact area were compared between groups. Local congruency was determined at the articular surface for two simulated activities.

RESULTS

The labrum in dysplastic hips supported 2.8-4.0 times more of the load transferred across the joint than in normal hips. Dysplastic hips did not have significantly different congruency in the primary load-bearing regions than normal hips, but were less congruent in some unloaded regions. Normal hips had larger cartilage contact stress than dysplastic hips in the few regions that had significant differences.

CONCLUSIONS

The labrum in dysplastic hips has a far more significant role in hip mechanics than it does in normal hips. The dysplastic hip is neither less congruent than the normal hip, nor subjected to elevated cartilage contact stresses. This study supports the concept of an outside-in pathogenesis of OA in dysplastic hips and that the labrum in dysplastic hips should be preserved during surgery.

Results of arthroscopic labral reconstruction of the hip in elite athletes

BACKGROUND

Femoroacetabular impingement (FAI) has been well characterized as a cause of hip pain and resultant damage to the acetabular labrum. It has become increasingly clear that an intact labrum is essential for normal joint mechanics, hip stability, and preservation of the articular cartilage. Elite athletes with a hypoplastic or irreparable labrum present a difficult clinical challenge.

PURPOSE

To assess clinical outcomes and determine if elite athletes are able to return to a high level of function and sport after labral reconstruction.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective review of a prospectively collected registry identified 21 elite athletes (23 hips) with an average age of 28.0 years (range, 19-41 years) who underwent an arthroscopic iliotibial band labral reconstruction. Concomitant procedures included femoral and acetabular osteoplasty in all patients and microfracture in 9 of 23 hips. Clinical outcomes were assessed with the modified Harris Hip Score (MHHS), the Hip Outcome Score (HOS), the Short Form-12 (SF-12), and patient satisfaction (on a scale from 1-10). Return to play was determined, as well as level of return to play, based on sport-specific statistics.

RESULTS

Two patients progressed to arthroplasty. There were 2 revisions in this group of patients, both for lysis of capsulolabral adhesions in which the graft was found to be well integrated at the time of surgery. The rate of return to play was 85.7% (18/21), with 81% (17/21) returning to a similar level. Subjective follow-up was obtained from 17 of the remaining 19 patients (89%), with an average follow-up of 41.4 months (range, 20-74 months). The average MHHS improved from 67 to 84 (P = .026) and the average HOS Sport subscore from 56 to 77 (P = .009). The overall median patient satisfaction with outcome was 8.2 (range, 3-10).

CONCLUSION

Arthroscopic labral reconstruction using an ipsilateral iliotibial band autograft provides good short-term clinical outcomes, high patient satisfaction, and a satisfactory level of return to play in a select group of elite athletes.

In vitro analysis of peri-articular soft tissues passive constraining effect on hip kinematics and joint stability

PURPOSE

Aim of the study is to assess the contribution of peri-articular soft tissues to hip joint kinematics and their influence on hip stability.

METHODS

Four hemi-corpse specimens (3 males, average age 72 years) were studied using a custom navigation system. Hip kinematics (femoral head motion relative to the acetabulum and joint range of motion) were evaluated with the hip manually positioned in 36 different positions with (I) soft tissues intact, (II) after removal of the skin and muscles and (III) after partial capsulectomy. Each position was repeated 3 times in each state.

RESULTS

Excellent interclass correlation for each test was determined (ICC range, 0.84-0.96). Femoral head anatomical centre displacement relative to the acetabulum occurred in all 3 planes, even with all the soft tissue intact (average, 3.3 ± 2.8 mm lateral translation; 1.4 ± 1.8 mm posterior translation and 0.3 ± 1.5 mm distally). These translations increased as more soft tissue was removed, except medial-lateral displacement, with an average 4.6 ± 2.9 mm lateral translation, 0.7 ± 1.3 mm posterior translation and 1.5 ± 1.9 mm distal translation when partial capsulectomy was performed. Range of motion increased in all 3 planes with increasing removal of the soft tissues.

CONCLUSIONS

This study showed that femoral head anatomical centre displacement within the acetabulum occurs and increases with increasing removal of peri-articular soft tissues, confirming their influence on hip stability. Hip kinematics was also influenced by peri-articular soft tissues; specifically range of motion increases with increasing removal of those tissues. From clinicians' point of view, they have therefore to consider the influence of their surgeries on peri-articular soft tissues, since excessive translations may promote hip arthritis.

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.

Preliminary pain and function after labral reconstruction during femoroacetabular impingement surgery

BACKGROUND

Labral refixation rather than resection provides better pain relief and function after femoroacetabular impingement (FAI) surgery. When the labrum is absent, degenerated, or is irreparable, reconstruction may provide a favorable biomechanical environment for the hip. However, it is unclear whether labral reconstruction relieves pain and restores function.

QUESTION/PURPOSES

In patients undergoing FAI surgery with concomitant labral reconstruction, (1) Do they note subjective improvement in pain at latest followup? (2) What is their postoperative activity level? (3) What are the complications, reoperation rates, and reasons for failure?

METHODS

We retrospectively reviewed all 19 patients who underwent labral reconstruction in 20 hips at the time of surgical hip dislocation between August 2007 and February 2011. We assessed improvement in pain and function, complications, and subsequent surgery through a chart review and questionnaire. The minimum followup was 12 months (average, 26.4 months; range, 12-56 months).

RESULTS

Three hips in three patients were converted to THA within 36 months of their surgical hip dislocation for continued preoperative pain. Of the 17 hips not undergoing THA, 15 reported subjective improvement in preoperative pain and function. The average UCLA score was 8.5 (range, 5-10). We observed no complications associated with the labral reconstruction itself.

CONCLUSION

The majority of patients with reconstructed acetabular labra reported improvement in their hip pain and function after surgery. The causes of persistent symptoms and conversion to THA remain uncertain. The data and conclusions of this study are limited secondary to lack of objective outcome measures.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Labral Resection or Preservation During FAI Treatment? A Systematic Review

BACKGROUND

Open and arthroscopic treatment of femoroacetabular impingement and resultant labral pathology has increased significantly over the past decade. Although the functional importance of the labrum and the labral seal has been established in biomechanical studies, good clinical results have been reported for both labral debridement and labral refixation.

QUESTIONS/PURPOSES

The purpose of this paper is to summarize existing literature on the surgical treatment of labral pathology to provide treatment recommendations and direct future research. A systematic review was performed with the following research question in mind: Does preservation of the hip labrum improve outcomes as compared to labral debridement for the treatment of labral pathology?

METHODS

The MEDLINE database was searched for level I, II, or III articles in English or German comparing labral debridement to labral refixation. Five studies were included in the analysis.

RESULTS

Good short-term results were reported for both groups. Three out of five papers report improved outcomes after labral refixation as compared to labral debridement.

CONCLUSIONS

In short-term follow-up, labral refixation appears to have slightly better outcomes than labral debridement. Studies with prospectively defined cohorts and longer follow-up are, however, necessary to provide definitive recommendations for labral treatment.

Labral refixation: current techniques and indications

BACKGROUND

Labral tears have been associated with femoroacetabular impingement, instability, sports-related activity or trauma, capsular laxity or hypermobility, dysplasia, and degeneration. Disruption of the labrum increases the rate of acetabular cartilage compression and the contact stress between the femoral and acetabular cartilage. If left untreated, these lesions will alter normal hip joint function and may eventually lead to osteoarthritis.

METHODS

For the labrum with adequate tissue (>7 mm), the labrum is repaired if it is detached or torn. If the labrum is bruised, a rim reduction and repair is performed, especially in the presence of cartilage damage and the labral-chondral junction. Labri are debrided only if there is enough substance to maintain the function of the labrum. Care must be taken to fix the labrum so that it provides adequate seal with the femoral head.

RESULTS

Two-year outcome on 122 patients who underwent arthroscopic treatment for femoroacetabular impingement and chondrolabral dysfunction showed that, overall, most patients showed an improvement in symptoms and function and were satisfied with the results. Independent predictors of improved outcomes were joint space >2 mm and repair of labral pathology instead of debridement. Several other studies have shown excellent results following labral refixation and repair.

CONCLUSIONS

Labral tears have been associated with femoroacetabular impingement, instability, sports-related activity or trauma, capsular laxity or hypermobility, dysplasia, and degeneration. Untreated labral tears can result in premature osteoarthritis of the hip. Debridement only used to be the standard of care, but excellent results reveal arthroscopic labral repair and refixation are an option with good outcomes.

Periacetabular osteotomy for hip preservation

The Bernese PAO has now been performed for nearly 30 years. In that time, it has proved itself a technically complex procedure with the potential to considerably improve the natural history of the dysplastic hip. Significant refinements in the surgical technique combined with the recognition of FAI, improvements in the understanding of hip biomechanics and acetabular orientation, and more discerning patient selection have improved the outcomes related to this procedure. Although the recovery can be demanding and the potential for complications exists, the results are reproducible and the technique has become the gold standard for acetabular reorientation.

Labral penetration rate in a consecutive series of 300 hip arthroscopies

BACKGROUND

Intraoperative labral injury during the establishment of the first portal in hip arthroscopy has been reported to be as high as 20%.

PURPOSE

The purpose of the study was to prospectively identify the incidence of acetabular labral injuries that occurred while using a current technique for the establishment of portals during hip arthroscopy.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between the years 2008 and 2010, data were prospectively collected for all patients undergoing hip arthroscopic surgery. Patients with previous labral resection or Tonnis grade greater than 1 were excluded. Patients were positioned supine, traction was applied, and portals were established. The anterolateral portal was created first by venting the joint with a spinal needle and then re-entering the joint with the same needle with the bevel side facing the labrum. Next, the midanterior portal was created under vision. A thorough examination of the acetabular labrum was conducted arthroscopically through multiple viewing portals, and labral injuries related to the establishment of portals were identified and noted.

RESULTS

A total of 300 patients were included in the study; only 2 patients (0.67%) suffered intraoperative labral injuries at the study period. One injury occurred during revision arthroscopy, while the second involved a hyperplastic labrum in a dysplastic hip. No patient with normal hip morphological characteristics undergoing a hip arthroscopy suffered a labral tear as a result of portal placement.

CONCLUSION

The incidence of iatrogenic labral injury during hip arthroscopy can be as low as 0.67% when using the described technique.

MR-based parameters as a supplement to radiographs in managing developmental hip dysplasia

BACKGROUND

Some dysplastic hips with favorable radiographic parameters fail to develop normally, suggesting that we should consider cartilaginous or soft tissue structures for further information regarding the condition of the hip. The purpose of this study was to provide a clear definition of concentric reduction in developmental dysplasia of the hip (DDH) based on magnetic resonance imaging (MRI), and to determine how radiographic and MR-based parameters could be used together to treat dysplastic hips.

METHODS

We studied range of motion (ROM)-MRI of 25 patients with unilateral hip dysplasia (mean age at the time of MR imaging, 44.1 months). Each ROM-MRI consisted of a set of bilateral hip scans in the following positions: neutral; abduction; abduction- internal rotation; abduction-internal rotation-flexion; and adduction. Before MR scanning, the 25 patients received the following primary treatments: closed reduction (n = 15; at a mean age of 14.5 months); and open reduction (n = 10; at a mean age of 10.0 months). The following new parameters appear to be useful in treating DDH: 1) the labral angle, the angle the labrum makes with the acetabulum; 2) the uncorrected labral deformity (ULD), the "residual deformity" (deflection of the labrum) when the affected labrum is freed from pressure in abduction; and 3) the zone of compressive force (ZCF), the region of the acetabulum through which the body weight acts on the femoral head.

RESULTS

A concentrically-reduced hip is one in which the labrum points downward in the neutral position, at the same angle as that of the normal side; and in which the ZCF is zone 3, the inner acetabular zone as defined herein. The ULD and the ZCF may be determined precisely as we have done, or the physician may simply observe the changes in the orientation of the labrum and compare the changes qualitatively to the unaffected side, and likewise for the medial joint space.

CONCLUSIONS

Detailed analysis of the labrum as permitted by ROM-MRI, together with acetabular index and other parameters measured from radiographs, provides important information for physicians treating childhood hip dysplasia.

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.

Concurrent criterion-related validity of physical examination tests for hip labral lesions: a systematic review

Hip injuries are prevalent, especially within the athletic population. Of the hip injuries in this population, some 18-55% are lesions to the labrum of the hip. Clinical diagnosis of hip labral lesions is difficult because data on prevalence are varied. In addition, data on the prevalence of internal and external risk factors are absent as are data on the correlation of these risk factors with labral lesions, making it difficult to gauge the diagnostic utility. The mechanism of injury is often unknown or not specific to labral lesions. Internal risk factors may remain hidden to physical therapists because in most jurisdictions, ordering imaging tests is not within their scope of practice. Anterior inguinal pain seems highly sensitive for the diagnosis of patients with labral lesions but can hardly be considered specific; data on other pain-related and mechanical symptoms clearly have little diagnostic utility, making these data collected during the patient history almost irrelevant to diagnosis. By way of a comprehensive literature review and narrative and systematic analysis of the methodological quality of the retrieved diagnostic utility studies, this paper aimed to determine a diagnostic physical examination test or test cluster based on current best evidence for the diagnosis of hip labral lesions. Current best evidence indicates that a negative finding for the flexion-adduction-internal rotation test, the flexion-internal rotation test, the impingement provocation test, the flexion-adduction-axial compression test, the Fitzgerald test, or a combination of these tests provides the clinician with the greatest evidence-based confidence that a hip labral lesion is absent. Currently, research has produced no tests with sufficient specificity to help confidently rule in a diagnosis of hip labral lesion. Suggestions for future research are provided.

Role of the acetabular labrum and the iliofemoral ligament in hip stability: an in vitro biplane fluoroscopy study

BACKGROUND

Recent biomechanical reports have described the function of the acetabular labrum and iliofemoral ligament in providing hip stability, but the relative stability provided by each structure has not been well described.

HYPOTHESIS

Both the iliofemoral ligament and acetabular labrum are important for hip stability by limiting external rotation and anterior translation, with increased stability provided by the iliofemoral ligament compared with the acetabular labrum.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifteen fresh-frozen male cadaveric hips were utilized for this study. Each specimen was selectively skeletonized down to the hip capsule. Four tantalum beads were embedded into each femur and pelvis to accurately measure hip translations and rotations using biplane fluoroscopy while either a standardized 5 N·m external or internal rotation torque was applied. The hips were tested in 4 hip flexion angles (10° of extension, neutral, and 10° and 40° of flexion) in the intact state and then by sectioning and later repairing the acetabular labrum and iliofemoral ligament in a randomized order.

RESULTS

External rotation significantly increased from the intact condition (41.5° ± 7.4°) to the sectioned iliofemoral ligament condition (54.4° ± 6.6°) and both-sectioned condition (61.5° ± 5.7°; P < .01), but there was no significant increase in external rotation when the labrum alone was sectioned (45.6° ± 5.9°). The intact and fully repaired conditions were not significantly different. External rotation and internal rotation significantly decreased when the hip flexion angle decreased from 40° of flexion to 10° of extension (P < .01) regardless of sectioned condition. Anterior translation varied significantly across sectioned conditions but not across flexion angles (P < .001). The ligament-sectioned (1.4 ± 0.5 mm), both-sectioned (2.2 ± 0.2 mm), and labrum-repaired (1.1 ± 0.2 mm) conditions all resulted in significantly greater anterior translation than the intact condition (-0.4 ± 0.1 mm) (P < .001).

CONCLUSION

The iliofemoral ligament had a significant role in limiting external rotation and anterior translation of the femur, while the acetabular labrum provided a secondary stabilizing role for these motions.

CLINICAL RELEVANCE

These results suggest that, if injured, both the acetabular labrum and iliofemoral ligament should be surgically repaired to restore native hip rotation and translation. In addition, a careful repair of an arthroscopic capsulotomy should be performed to avoid increased external hip rotation and anterior translation after arthroscopy.

Arthroscopic treatment for acetabular labral tears of the hip without bony dysmorphism

BACKGROUND

Surgical treatment for labral tears of the hip has shown good results in patients with bony impingement lesions; however, results are also affected by the correction of bony abnormalities. This study evaluates the outcome of arthroscopic treatment for acetabular labral tears without associated dysplasia or bony impingement lesions.

HYPOTHESIS

Based on the structural importance of the acetabular labrum, labral tear debridement or repair can relieve pain and improve function.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The study included 81 patients who were categorized according to 4 morphologic labral tear types. The tear type, degree of synovitis, and chondral damage were analyzed with the use of multivariate regression analysis and correlated to the clinical outcome. The outcome was assessed utilizing the modified Harris hip score (MHHS) and the nonarthritic hip score (NAHS).

RESULTS

There were 81 patients (81 hips), including 20 men and 61 women, with 41 right and 40 left hips. Their mean age was 44 years. Overall, at an average follow-up of 3 years the mean MHHS had improved by 18 points (95% confidence interval [CI], 13-23) and the mean NAHS by 17 points (95% CI, 12-22). An improvement after arthroscopic treatment was noticed in all types of labral tears of the hip. The level of synovitis and of chondral lesions was found to have a significant negative effect on the clinical outcome.

CONCLUSION

Arthroscopic treatment for acetabular labral tears of the hip without dysplasia or bony impingement lesions has good short- to midterm results. The best outcome is expected in the absence of synovitis and chondral lesions.

The Impact of Glenoid Labrum Thickness and Modulus on Labrum and Glenohumeral Capsule Function

The glenoid labrum is an integral component of the glenohumeral capsule’s insertion into the glenoid, and changes in labrum geometry and mechanical properties may lead to the development of glenohumeral joint pathology. The objective of this research was to determine the effect that changes in labrum thickness and modulus have on strains in the labrum and glenohumeral capsule during a simulated physical examination for anterior instability. A labrum was incorporated into a validated, subject-specific finite element model of the glenohumeral joint, and experimental kinematics were applied simulating application of an anterior load at 0 deg, 30 deg, and 60 deg of external rotation and 60 deg of glenohumeral abduction. The radial thickness of the labrum was varied to simulate thinning tissue, and the tensile modulus of the labrum was varied to simulate degenerating tissue. At 60 deg of external rotation, a thinning labrum increased the average and peak strains in the labrum, particularly in the labrum regions of the axillary pouch (increased 10.5% average strain) and anterior band (increased 7.5% average strain). These results suggest a cause-and-effect relationship between age-related decreases in labrum thickness and increases in labrum pathology. A degenerating labrum also increased the average and peak strains in the labrum, particularly in the labrum regions of the axillary pouch (increased 15.5% strain) and anterior band (increased 10.4% strain). This supports the concept that age-related labrum pathology may result from tissue degeneration. This work suggests that a shift in capsule reparative techniques may be needed in order to include the labrum, especially as activity levels in the aging population continue to increase. In the future validated, finite element models of the glenohumeral joint can be used to explore the efficacy of new repair techniques for glenoid labrum pathology.

Labral base refixation in the hip: rationale and technique for an anatomic approach to labral repair

Recent literature has defined the importance of anatomic repair in shoulder and knee arthroscopy. New advances in hip arthroscopy have created opportunities to apply the principle of anatomic repair to the hip. To address the obstacles in the restoration of labral anatomy, we describe an anatomic approach to labral refixation. We reviewed the literature on biomechanics of the labrum to identify the factors that are essential to the function of the labrum. Existing techniques for arthroscopic labral repair and potential challenges in restoration of labral anatomy were reviewed. A list of criteria for anatomic labral repair was created, and a technique for anatomic labral base refixation was developed. The technique incorporates the understanding of the function and biomechanical role of the labrum and builds on existing techniques to fulfill the criteria for restoration of anatomy. Our purpose was to review the anatomy, biomechanics, and existing repair techniques of the labrum, as well as to describe the rationale and surgical steps for anatomic labral base refixation in the hip.

Penetration depth method--novel real-time strategy for evaluating femoroacetabular impingement

We introduce a new method for computerized real-time evaluation of femoroacetabular impingement (FAI). In contrast to previously presented stress analyses, this method is based on two types of predictions of penetration depths for two rotating bodies: curvilinear and radial penetration depth. This intuitive method allows the analysis of both bony and soft tissue structures (such as cartilage and acetabular labrum) in real time. Characteristic penetration depth patterns were found for different subtypes of FAI, such as cam and pincer pathologies. In addition, correlation between the penetration depths (estimated by applying this method) and the existing contact stresses (estimated by applying the finite element method) of various hip morphologies were found. A strong correlation with predicted stress values existed, with a mean correlation coefficient of 0.91 for the curvilinear and 0.80 for the radial penetration method. The results show that the penetration depth method is a promising, fast, and accurate method for quantification and diagnosis of FAI.

Prognostic value of chondral defects on the outcome after arthroscopic treatment of acetabular labral tears

Pathology of the acetabular labrum plays an increasing role in the treatment of hip pain. Hip arthroscopy has proven its clinical value as a useful procedure for successful treatment of labral tears. Until today, only a few studies have investigated the influence of articular cartilage defects on the clinical outcome of partial arthroscopic labrum resection in a larger patient population. We prospectively evaluated patients with an intraoperatively proven labral lesion/tear without any radiological and arthroscopical sign of a concomitant bony femoroacetabular impingement or hip dysplasia for a minimum postoperative follow-up of 2 years. Cartilage defects were classified according to Outerbridge and divided into two subgroups: Outerbridge < or = 1 and Outerbridge > or = 2, respectively. To evaluate combined results, various established scoring systems (visual analogue scale, modified Harris Hip Score, Larson Hip Score) were used. Out of 54 originally enrolled patients, 50 individuals (29 female, 21 male) with a median age of 33 years (range 15-49) were available for follow-up after a mean of 34 (range 24-48) months. At follow-up, the total study population experienced significant improvement in pain and in the combined evaluation scales (Larson Hip Score/MHHS). When patients were categorized into two subgroups, either with intraoperatively present or absent articular cartilage defects, our data indicated that subjects with no degenerative changes of the articular cartilage surface significantly improved in the applied clinically scoring systems. In contrast, in patients with an articular cartilage lesion during hip arthroscopy score values had a tendency to be unimproved or even deteriorated at follow-up. Regression analysis revealed a significant negative correlation between postoperative outcome and the grading of the coexistent articular cartilage defect. On the basis of our investigation, we conclude that partial arthroscopic resection of a torn labrum without attending bone deformity (dysplasia or femoroacetabular impingement) can reveal good and satisfied results. Depending on the extent of a coexisting articular cartilage defect subjective clinical results are compromised.