Testing of cadaver ankle specimens was conducted to investigate the changes in kinematics with lateral ligament reconstructions. Testing included an intact condition, after injury at the ATFL and CFL sites, and separately a Brostrom repair and an anatomical gracil-lis graft reconstruction. Calcaneal range of motion was determined about the axis of applied moment in plantarflexion-dorsiflexion and in inversion-eversion directions. The injury and reconstructions were most sensitive during IE applied moment. Both reconstructions appeared to behave similar to intact motion. Failure of some Brostrom repairs however, suggest that the gracillis-graft reconstruction is initially a stronger repair. Limited research has biomechanically investigated lateral ankle ligament reconstruction procedures. The objective of this study was to determine the changes in ankle kinematics with a dual ligament Brostrom repair and an anatomical gracillis graft reconstruction. Seven cadaveric ankle specimens were tested independently in an intact condition, after an ATFL/CFL injury model, and two reconstructions. The anatomical graft reconstruction wove a gracillis tendon through the calcaneus and fibula to dually reconstruct the ATFL and CFL, and anchored to the talus. Moments were applied to the calcaneus for three cycles in plantarflexion-dorsiflexion (PD) and inversion-eversion (IE) while allowing unconstrained motion. Three dimensional motions of the calcaneus and tibia were optoelectronically tracked. Range of motion (ROM) was calculated about the axis of applied moment for the calcaneus with respect to the tibia. The ROM increase from the intact condition with the injury model was only significant for IE (p=0.001). No significant differences were found between intact and any treatments in the PD configuration. In IE, both the graft reconstruction and the Brostrom repair were significantly different from the injury model (p=0.002 and p=0.015 respectively), where the gracillis reconstruction appears more similar to the intact condition. For two specimens the Brostrom repaired ATFL failed during applied inversion moment. The injury and reconstructions were most sensitive during IE applied moment. Both reconstructions appeared to behave similar to the intact condition. Failure of some Brostrom repairs however, suggest that the gracillis-graft reconstruction is initially a stronger repair. Funding: Workers Compensation Board of British Columbia
The purpose of this study was to investigate the strength profile of the thoracolumbar endplate. Indentation testing was performed on the T9, T12, and L2 endplates of six fresh-frozen human cadaver vertebrae. Indentations were performed in a standardized rectangular grid pattern of seven columns and five rows. There was an incremental increase in the strength of each row moving anterior and posterior from the central row. The relative strength of the anterior regions of the endplate increased with rostral ascent into the thoracic spine. The purpose of this study was to map the strength profile of the thoracolumbar endplates using indentation testing. Indentation testing was performed on the T9, T12, and L2 endplates of six fresh-frozen human cadaver spines using a materials testing machine (Dynamight, Instrom Corporation, Canton, MA). A minimum of twenty-five indentations was performed in a rectangular grid (seven columns by five rows). A 3mm hemispherical indendor was lowered at 0.2mm/s to a depth of 3mm producing endplate failure. The failure load significantly varied with the AP and LAT positions (p<
.0001). Each row was significantly stronger than the rows anterior to it (p <
0.04), except for the most row. The most lateral columns were stronger than the central (range: p = .04 – .0002). The mean strength of the L2 posterior row was greater than that for the thoracic endplates (p<
.01), while no difference existed between levels within the two anterior rows. The ratio of the mean strength for the posterior row compared to that of the anterior row was significantly different across level (P<
0.036). The ratios for L2, T12, and T9 were 1.35, 0.97, and 0.91 respectively. The periphery of the thoracolumbar endplate is stronger than the centre. The interaction identified between position and level suggests a relative strength increase in the anterior aspect of the endplate with rostral ascent into the thoracic spine. This knowledge may assist in preventing intervertebral inplant subsidence by influencing implant positioning and design.
