Peter Mahieu

Three-Dimensional Assessment of Cam Engagement in Femoroacetabular Impingement

PURPOSE The purpose of our study was to 3-dimensionally assess cam engagement in male patients with symptomatic femoroacetabular impingement during motion. METHODS A total of 13 hips with cam-type impingement were investigated. Patient anatomy and clinical range of motion were determined. After 3-dimensional segmentation and reconstruction, the dynamic behavior of the cam lesion was investigated for the previously analyzed motions. RESULTS Important differences in the pattern of cam engagement were noticed. Abutment of the cam lesion and the acetabular cartilage was observed in flexion in 7 hips (54%) and in abduction in 11 hips (84%). Internal rotation with the hip in 90° of flexion caused intrusion of the cam lesion into the joint in 10 of the investigated cases (77%). Neutral rotation did not cause any conflict between the cam lesion and acetabulum for the measured range of motion. A similar area in the anterosuperior quadrant of the acetabulum appeared to be involved in the different motions that were analyzed. CONCLUSIONS Typically, during internal rotation in 90° of flexion, the centromedial portion of the cam lesion was found to abut against the anterosuperior quadrant of the acetabular cartilage. During abduction and flexion, this appeared to be the lateral and medial portions of the cam lesion, respectively. All motions causing cam intrusion appeared to focus on the same cartilage area of the acetabulum in its anterosuperior quadrant.

Reliability of a semi-automated 3D-CT measuring method for tunnel diameters after anterior cruciate ligament reconstruction: A comparison between soft-tissue single-bundle allograft vs. autograft☆

BACKGROUND Post-operative widening of tibial and/or femoral bone tunnels is a common observation after ACL reconstruction, especially with soft-tissue grafts. There are no studies comparing tunnel widening in hamstring autografts versus tibialis anterior allografts. The goal of this study was to observe the difference in tunnel widening after the use of allograft vs. autograft for ACL reconstruction, by measuring it with a novel 3-D computed tomography based method. METHODS Thirty-five ACL-deficient subjects were included, underwent anatomic single-bundle ACL reconstruction and were evaluated at one year after surgery with the use of 3-D CT imaging. Three independent observers semi-automatically delineated femoral and tibial tunnel outlines, after which a best-fit cylinder was derived and the tunnel diameter was determined. Finally, intra- and inter-observer reliability of this novel measurement protocol was defined. RESULTS In femoral tunnels, the intra-observer ICC was 0.973 (95% CI: 0.922-0.991) and the inter-observer ICC was 0.992 (95% CI: 0.982-0.996). In tibial tunnels, the intra-observer ICC was 0.955 (95% CI: 0.875-0.985). The combined inter-observer ICC was 0.970 (95% CI: 0.987-0.917). Tunnel widening was significantly higher in allografts compared to autografts, in the tibial tunnels (p=0.013) as well as in the femoral tunnels (p=0.007). CONCLUSIONS To our knowledge, this novel, semi-automated 3D-computed tomography image processing method has shown to yield highly reproducible results for the measurement of bone tunnel diameter and area. This series showed a significantly higher amount of tunnel widening observed in the allograft group at one-year follow-up. LEVEL OF EVIDENCE Level II, Prospective comparative study.

A statistical shape model of trochlear dysplasia of the knee

BACKGROUND Trochlear dysplasia is known as the primary predisposing factor for patellar dislocation. Current methods to describe trochlear dysplasia are mainly qualitative or based on a limited number of discrete measurements. The purpose of this study is to apply statistical shape analysis to take the full geometrical complexity of trochlear dysplasia into account. METHODS Statistical shape analysis was applied to 20 normal and 20 trochlear dysplastic distal femur models, including the cartilage. RESULTS This study showed that the trochlea was anteriorized, proximalized and lateralized and that the mediolateral width and the notch width were decreased in the trochlear dysplastic femur compared to the normal femur. The first three principal components of the trochlear dysplastic femurs, accounting for 79.7% of the total variation, were size, sulcus angle and notch width. Automated classification of the trochlear dysplastic and normal femora achieved a sensitivity of 85% and a specificity of 95%. CONCLUSIONS This study shows that shape analysis is an outstanding method to visualise the location and magnitude of shape abnormalities. Improvement of automated classification and subtyping within the trochlear dysplastic group are expected when larger training sets are used. CLINICAL RELEVANCE Classification of trochlear dysplasia, especially borderline cases may be facilitated by automated classification. Furthermore, the identification of a decreased notch width in association with an increased sulcus angle can also contribute to the diagnosis of trochlear dysplasia.

Soft Tissue Structure Modelling for Use in Orthopaedic Applications and Musculoskeletal Biomechanics

We present our methodology for the three-dimensional anatomical and geometrical description of soft tissues, relevant for orthopaedic surgical applications and musculoskeletal biomechanics. The technique involves the segmentation and geometrical description of muscles and neurovascular structures from high-resolution computer tomography scanning for the reconstruction of generic anatomical models. These models can be used for quantitative interpretation of anatomical and biomechanical aspects of different soft tissue structures. This approach should allow the use of these data in other application fields, such as musculoskeletal modelling, simulations for radiation therapy, and databases for use in minimally invasive, navigated and robotic surgery.

Estimating muscle fibre paths: a new method

The prevalence of omarthrosis, possible necessitating joint replacement, varies from 2.5% at the age of 50 years up to more than 10% at the age of 80 years. Due to individual variations in shoulder anatomy, the outcome of such surgery is often difficult to predict. To date optimum prosthetic configuration and technique are not yet defined. Moreover it is known that even small differences in operative prosthetic positioning importantly affect the final functionality (de Leest et al. 1996). As biomechanical models become more commonly used in pre operative planning there is a need to include detailed morphometric information including muscle pennation angles and 3 dimensional fibre paths accurately. To accomplish this some methods have been developed in the past, but these methods only captured a number of discrete points along the muscle fibre (Kaptein and van der Helm 2004). We propose a new technique that allows obtaining accurately origins, insertions and full paths of the muscle fibres. This information is to be used in conjunction with detailed 3D reconstructions of all bones involved in shoulder movement to create individualized shoulder models.

Motion capturing devices for assessment of upper limb kinematics: a comparative study

The influence of biomechanical research on orthopaedic practice has expanded in the last few years. Unlike the biomechanics of the lower limb, little is known yet about the biomechanics of the glenohumeral joint. Upper extremity kinematics can give insight into function after shoulder arthroplasty. Data on ranges of motion related to the performance of a selection of activities of daily living can aid the clinician in evaluating the outcome of the shoulder and elbow arthroplasties. For the assessment of complex movement of the glenohumeral joint, a 3D motion-capturing device is required. Several different types of devices are available; the most commonly used are optical systems. Alternative devices include electromagnetic systems, ultrasound systems, electrogoniometers. This study compares three different systems for assessment of upper limb kinematics.