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

Hip Labral Reconstruction with Capsular Autograft Augmentation

Multiple treatment options are available for patients presenting with a torn or deficient acetabular labrum. Biomechanical studies have demonstrated that the acetabular labrum may play a role in decreasing the risk of osteoarthritis and in maintaining long-term hip kinematics and stability. As such, repair or reconstruction of the labrum is often preferred over resection or debridement. In instances of a hypoplastic labrum, labral reconstruction or augmentation may be necessary even in a primary setting. Although reconstruction is a technique that should be in any hip arthroscopist's toolkit, allografts can be expensive and may not always be available when needed. In this Technical Note, we describe a labral augmentation with capsular autograft that diminishes donor-site morbidity associated with fascia lata autografts. This technique enables incorporation of healthy capsular tissue that allows for the recreation of the suction seal while avoiding some of the technically challenging aspects and costs of the conventional allograft labral reconstruction.

An Approach to Robotic Testing of the Wrist Using Three-Dimensional Imaging and a Hybrid Testing Methodology

Robotic technology is increasingly used for sophisticated in vitro testing designed to understand the subtleties of joint biomechanics. Typically, the joint coordinate systems in these studies are established via palpation and digitization of anatomic landmarks. We are interested in wrist mechanics in which overlying soft tissues and indistinct bony features can introduce considerable variation in landmark localization, leading to descriptions of kinematics and kinetics that may not appropriately align with the bony anatomy. In the wrist, testing is often performed using either load or displacement control with standard material testers. However, these control modes either do not consider all six degrees-of-freedom (DOF) or reflect the nonlinear mechanical properties of the wrist joint. The development of an appropriate protocol to investigate complexities of wrist mechanics would potentially advance our understanding of normal, pathological, and artificial wrist function. In this study, we report a novel methodology for using CT imaging to generate anatomically aligned coordinate systems and a new methodology for robotic testing of wrist. The methodology is demonstrated with the testing of 9 intact cadaver specimens in 24 unique directions of wrist motion to a resultant torque of 2.0 N·m. The mean orientation of the major principal axis of range of motion (ROM) envelope was oriented 12.1 ± 2.7 deg toward ulnar flexion, which was significantly different (p < 0.001) from the anatomical flexion/extension axis. The largest wrist ROM was 98 ± 9.3 deg in the direction of ulnar flexion, 15 deg ulnar from pure flexion, consistent with previous studies [1,2]. Interestingly, the radial and ulnar components of the resultant torque were the most dominant across all directions of wrist motion. The results of this study showed that we can efficiently register anatomical coordinate systems from CT imaging space to robotic test space adaptable to any cadaveric joint experiments and demonstrated a combined load-position strategy for robotic testing of wrist.

Robotic hip joint testing: Development and experimental protocols

The use of robotic systems combined with force sensing is emerging as the gold standard for in vitro biomechanical joint testing, due to the advantage of controlling all six degrees of freedom independently of one another. This paper describes a novel robotic platform and the experimental protocol used for hip joint testing. An experimental protocol implemented optical tracking and registration techniques in order to define the position of the hip joint centre of rotation (COR) in the coordinate system of the robot's end effector. The COR coordinates defined the origin of the task-related coordinate system used to control the robot, with a hybrid force/position law to simulate standard clinical tests. The axes of this frame were defined using the International Society of Biomechanics (ISB) anatomical coordinate system. Experiments were carried out on two cadaveric hip joint specimens using the robotic testing platform and a mechanical testing rig previously developed and described by our group. Simulated internal-external and adduction/abduction laxity tests were carried out with both systems and the resulting peak range of motion (ROM) was measured. Similarities and differences were observed in these experiments, which were used to highlight some of the limitations of conventional systems and the corresponding advantages of robotics, further emphasising their added value in vitro testing.

Biomechanics, anatomy, pathology, imaging and clinical evaluation of the acetabular labrum: current concepts

The labrum has been recognised to play an important role in the hip in regard to stability, fluid regulation, decreasing contact forces, proprioception and nociception. These functions are all important for normal joint homeostasis in a well-functioning hip and can be responsible for increasing joint pain, damage, instability and dysfunction when compromised. The labrum has been studied intently in the last few decades to better understand its role in the normal and the pathologic hip and how best to treat pathology that causes debilitating hip pain and dysfunction. This current concept review discusses and summarises the current literature on labral anatomy, biomechanics, pathology, clinical exam and imaging.

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.