The Biomechanical Study Of Acetabular Fracture With Secondary Congruence

Objective: Secondary congruence with respect to aboth-column acetabular fracture as described by Letournel is atheoretical condition that can by rotation of both the anterior andposterior columns around the femoral head while maintaining acongruent relationship of the head with the acetabular articularsurface. This state would allow hip joint contact stresses to bemore evenly distributed throughout the articular surfaces andthus result in lower peak articular contact pressures than thatseen in other displaced acetabular fractures affecting the roof.According to some reports, it may had good or excellentresults.It is well known, malreduction of interarticular fracturecan change the contact stresses distribution of the joint ,thusresults in increased wear on the articular cartilage andsubsequent posttraumatic arthritis. Although it maintain the stateof concentric circles, the both-column acetabular fracture withsecondary congruence create a larger acetabulum because of thegap between the fragment, which would likely react differenceto lord and speed up the occurred of posttraumatic arthritis. This study was to evaluate the biomechanical consequenceof acetabular fracture exhibiting secondary congruence withdifferent gap. using intact pelvis and fracture mode to determine 4英 文 摘 要the intraarticular loading characteristics present in simulatedsing-leg stance. Pressure-sensitive films were used to record thecontact characteristics between acetabular and femoral head–the load, the pressure and the distribution of the pressure. Method: Three embalmed cadaveric pelves and theirrespective proximal 1/3 femora were harvested. The pelves werecleaned of soft tissues and hip joint capsule. Two 2.0-mm holeswere drilled through the center of the acetabular surface atpoints 30 degrees on each side of the acetabular vertex markedA and B. The mold for the pressure-sensitive film cutting wereobtained by tailoring the seal gum covering the articular surfaceof famoral head into 12 equalarea parts. The pressure-sensitivefilms were fixed to the surface of femoral head. The specimenswere fixed in simulated single-leg stance by self-made fixture.the line between iliac crests parallelds to the floor. The planeformed of the anterior superior iliac spine and the pubic tuberclealigned vertically. Relative to the pelve , the femur was in theposition fifteen degrees adduction, zero degrees flexion, fivedegrees internal rotation. The specimens was loaded to 500Newtons at the rate of 10 Newtons/second and keep 120seconds using Biomechanical testing machine. During loading, apointless probe was used to mark the pressure-sensitive filmthrough the hole to establish a reference point of the film withthe acetabulum. After loading, the films were removed fromthe femoral head and adhered to a paperboard. The sequence is 5英 文 摘 要in turn by intact, both-column acetabular fracture anatomicreduction, has 2mm, 5mm gap between anterior and posteriorcolumn but exhibiting secondary congruence. Thepressure-sensitive film was divided into threeparts---dome ,anterior articular region ,posterior region by themarker .measure the loading area ,the pressure,and thedistribution of the press。 Results: About to the both-column acetabular fracture withsecondary congruence, when the gap about 2mm, it has a smalleffect to the contact characteristics between the acetabulum andfemoral head although there has a concentrated stress at the twosides of fracture line. But when the gap is 5mm, there has aremarkable change to the contact characteristics between theacetabulum and femoral head. Meanwhile it is decreased inanterior articular region. In posterior articular region, the contactarea decreased while mean and peak pressure increasedsignificantly. Conclusion: The both-column acetabular fracture wit...