Labral Reconstruction with Iliotibial Band Autograft and Semitendinosus Allograft Improves Hip Joint Contact Area and Contact Pressure: An In-Vitro Analysis

Objectives: Labral reconstruction using iliotibial band (ITB) autograft and semitendinosus (Semi-T) allograft have recently been described in cases of labral deficiency. The current study seeks to understand the biomechanical effects of an intact labrum, segmental labral resection, and labral reconstruction on joint contact area, contact pressure, and peak force. Methods: Ten fresh-frozen human cadaver hips were analyzed utilizing thin-film piezoresistive load sensors to measure contact area, contact pressure, and peak force 1) with the native intact labrum, 2) after segmental labral resection and 3) after graft labral reconstruction with either ITB autograft or Semi-T allograft. Each specimen was examined at 20° extension and 60° flexion. Statistical analysis was conducted through one-way ANOVA with post-hoc Games-Howell tests. Results: For the ITB group, labral resection significantly decreased contact area (20°: 73.2%±5.38, P=0.0010; 60°: 78.5%±6.93, P=0.0063) and increased contact pressures (20°: 106.7%±4.15, P=0.0387; 60°: 103.9%±1.15, P=0.0428). ITB reconstruction improved contact area (20°: 87.2%±12.3, P=0.0130; 60°: 90.5%±8.81, P=0.0079) and contact pressures (20°: 98.5%±5.71, P=0.0476; 60°: 96.6%±1.13, P=0.0056) from the resected state. Contact pressure at 60° flexion was significantly lower compared to the native labrum (P = 0.0420). For the Semi-T group, labral resection significantly decreased contact area (20°: 68.1±12.57, P=0.0002; 60°: 67.5%±6.70, P=0.0002) and increased contact pressures (20°: 105.3%±3.73, P=0.0304; 60°: 106.8%±4.04, P=0.0231). Semi-T reconstruction improved contact area (20°: 87.9%±7.95, P=0.0087; 60°: 92.9%±13.2, P=0.0014) and contact pressures (20°: 97.1%±3.18, P=0.0017; 60°: 97.4%±4.39, P=0.0027) from the resected state. Comparative analysis demonstrated no statistically significant differences between either graft reconstruction in relation to contact area, contact pressure, or peak forces. (Figure 1). Conclusion: Segmental anterosuperior labral resection results in significantly decreased contact area and increased contact pressures, while labral reconstruction partially restores time-zero acetabular contact areas and pressures as compared to the resected state. Although labral reconstruction improved the measured biomechanical properties as compared to the resected state, some of these properties remained significantly different compared to the native intact labrum

3-Dimensional Physiologic Postural Range of the Mandible: A Computerized-Assisted Technique—A Case Study

Previous studies demonstrated that while the mandible assumes its resting position in space, antagonistic muscles should assume minimal muscle activity within a spatial range. This zone of mandibular rest has been mapped using physiologic parameters of muscle activity and incisal spatial kinematics. This case study expands on previous research by monitoring incisal and posterior jaw position and includes lateral pterygoid muscle activity, thus allowing for determining the spatial range including additional relevant coordinates and muscle activity. Four positions were evaluated: a maximum physiologic open position, a maximum physiologic closed position, physiologic rest position, and maximum physiologic protrusion position. Within the physiologic zone of rest formed by these 4 positions, the vertical and anterior borders of the envelope of function may be documented for the incisal and posterior mandible in true 3-dimensional fashion to assist the clinician in determining a physiologic interocclusal freeway space and vertical dimension of occlusion. Advantages and limitations are discussed

Pentlandite phase relations in the Fe-Ni-S system and the stability of the pyrite-pentlandite assemblage.

In the last decade geologists have made increasing use of phase equilibrium studies in synthetic systems to provide the fundamental data for the interpretation and understanding of the occurrence of minerals and mineral assemblages. The economic geologist has directed considerable study into the phase relations of the Fe-Ni-S system as a large number of the phases are found as minerals, which in some cases constitute important sources of nickel, iron and related metals. [...