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A Dual-Plane Fluoroscopy Study for Hip Femoracetabular Impingement
  • Department: Department of Biomedical Engineering

A Dual-Plane Fluoroscopy Study for Hip Femoracetabular Impingement

Femoroacetabular impingement is one common cause of hip pain and osteoarthritis. Three recognized patterns of lesion (cam, pincer, and mixed) have been recently described. In cam deformity, increased volume of bone in the head/neck junction and decreased head off-set to promote pathological contact of the femur to the anterior rim of the acetabulum, leading to intra-articular soft tissue damage (labral tears, chondral lesion). In pincer deformity, the acetabulum is prominent in its anterior portion. The conflict between bone structures occurs in extreme range of motions such as flexion, abduction, and/or internal rotation. Direct correlation between the zone of conflict and articular damage has been demonstrated by some studies. In the presence of that conflict with repetitive movements and load, the cartilage and the labrum, which are weaker than bone, will eventually fail. That explains why those lesions are more often diagnosed earlier in physically active people.

The treatment of this condition is based on the resection of the bone deformities in order to allow the most congruent range of articular motion, without the occurrence of further conflict. This treatment approach has been proved to be effective to relieve pain and resume function in short- and mid-term follow-up times both after arthroscopic and open surgeries. However, whether the treatment of this condition will be able to prevent the progression to articular degeneration is a question still to be answered. While long-term results (15 to 20 years) are not readily available, other indirect methods to evaluate the efficacy of that procedure can be performed immediately. Assessing whether the treatment is able to modify positively the joint biomechanics is feasible.

Our hypothesis is that, for painful range of motion, femoral head deformities cause a measurable decrease in the joint space and therefore increased articular pressure and shear forces. We believe that surgical treatment of FAI is able to increase range of motion and solve the conflict between the femur and the acetabulum, providing a measurable improvement of the articular space during the previously painful range of motion.

In a prospective study, patients with cam impingement will be enrolled and evaluated preoperatively and eight weeks after surgery. Computed tomographies will be obtained for each patient in order to provide a model to the computer software. The articular space of the hip will be then assessed in rest position and at painful range of motion during squat exercises by a dual-plane fluoroscopy system. Additionally, electromyography and 3-D motion analysis using retro-reflective markers and synchronized cameras will be obtained to provide additional information on the musculoskeletal dynamics of those patients. Computer analysis will be carried on to determine the possible differences in articular space for determined ranges of motion between pre- and postoperative status.

The importance of this original study is to determine the dynamics of the articular space in painful hip range of motion on FAI patients. This will allow better understanding of the injury mechanism of softtissues within the joint. Additionally, it will provide biomechanical evidence of the potential long-term benefits of treatment of patients with FAI, indicating the advantages of early treatment of patients with such deformities.

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