Paper 2: Biomechanical Alterations in Patients With Femoroacetabular Impingement

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ABSTRACTS

the acetabulum and the femoral head, with the underlying hypothesis that both the articular surfaces were spherical. Next, the distances between the centers of the spheres that approximate the acetabulum and the femoral head during the described motions were computed. In order to quantify the reliability of the performed movements, we evaluated the correlation functions for the joint clinical angles (flexion / extension, abduction / adduction, internal / external rotation) and the centers of displacements (anterior / posterior, medial / lateral, proximal / distal), among the three subsets of data. Moreover, the minimum distances between the approximated spheres of the acetabulum and of the femoral head during the pivoting motion, i.e. a passive movement in the hip physiological range-of-motion were determined. In order to clearly define the contact area within the acetabulum, we used the “clockface representation” of the acetabulum, which divides the acetabular surface into 12 sectors, like hours on a clockface. Using previously published standards, 12 o’clock is lateral, 6 o’clock is in the middle of the inferior transverse ligament, 3 o’clock is always anterior, and 9 o’clock is always posterior Results: The evaluation of the correlation function, relatively to joint clinical angles, suggested an excellent repeatability of the pivoting movement even manually performed; the corresponding maximum value of correlation function ranged from 0.71 to 0.99. The analysis of the correlation for joint displacements also confirmed these results. The location of the contact areas was mainly concentrated between 7 o’clock and 10 o’clock in the clock scheme (primarily posterior). The analysis of the displacements between the acetabulum and femoral head centers underlined a predominant motion in the medial - lateral direction; specifically the mean(⫾SD) motion was 3.4 ⫾ 0.2 mm in medial / lateral direction, 1.5 ⫾ 0.2 mm in antero / posterior direction and 1.5 ⫾ 0.2 mm in proximal/distal direction. Conclusion: In conclusion this study confirms that the hip joint is not a perfect ball-and-socket joint with motion of the femoral head center relative to the acetabular center during a pivoting motion. The greatest motion is in the medial – lateral direction, however, motion occurs in the antero-posterior and proximal-distal direction as well. Further, this study demonstrates that the contact area of the hip is mainly in the posterior acetabulum during a pivoting motion.

Paper 2: Biomechanical Alterations in Patients With Femoroacetabular Impingement BRIAN D. GIORDANO, MD, USA, PRESENTING AUTHOR AND JASON SNIBBE, MD, USA · Kerlan Jobe Orthopaedic Clinic

SUMMARY Biomechanical testing of the pelvis, hip, and distal kinetic chain was carried out in patients with femoroacetabular impingement and compared with normal control subjects. DATA Introduction: Femoroacetabular impingement (FAI) is a recently proposed pathomechanical process that has been implicated in the development of acetabular labral tears, articular cartilage injury, and early onset osteoarthritis. The spectrum of pathology among FAI patients is diverse. While some patients experience only subtle pain or functional deficiencies, others may have difficulty executing even simple tasks of daily living. A great deal of clinical and benchtop research has been devoted to improving surgical techniques and fostering a better understanding of the underlying morphologic conflict in patients with FAI. Despite advancements in such areas of study, biomechanical alterations in patients with FAI remain poorly understood. Furthermore, we are not aware of any studies that have examined the influence of FAI on biomechanics of the distal kinetic chain. Materials and Methods: In this biomechanical study, 20 patients were recruited (10 age, sex, BMI matched control and 10 patients with unilateral FAI) to undergo biomechanical testing. A 5-task biomechanical analysis was conducted with a 3-D computer aided motion analysis system and high speed video monitoring. For each biomechanical task, motions at the pelvis, thigh, knee and foot were captured in the sagittal, frontal, and transverse planes. Kinematic and kinetic data was recorded using reflective markers and force plates. Results: Patients with FAI demonstrated a statistically significant increase in pelvic contralateral rotation during running as well significant side-to-side differences in the frontal and sagittal planes at the hip. In addition, patients with FAI exhibited a significant increase in side-to-side knee valgus and tibial external rotation. When patients with FAI were compared with control subjects, variations were again observed at the pelvis, hip, and knee. These alterations were in concert with findings observed between the symptomatic and asymptomatic limbs of FAI patients. Conclusions: This study uncovered a number of significant alterations in pelvic and hip kinematics. In addition, variations in knee kinematics were observed that reflect known risk factors for specific injury patterns. Changes in pelvis, hip, and knee kinematics were observed in a direct side-to-side comparison of involved and uninvolved limbs of FAI patients, as well as between FAI patients and control subjects. A global disynchrony in

ABSTRACTS pelvi-femoral rhythm was also evident in patients with symptomatic FAI. It is unclear whether this finding is due to the characteristic morphologic abnormalities of FAI, or an overall deconditioning of the symptomatic limb that often accompanies this condition. As predicted, FAI patients sometimes utilized specific adaptive strategies to overcome abnormal morphology. Paper 3: Four Dimensional Computer Tomograpic Video Evaluation in Hip Arthroscopy CHRISTOPH GEORG GEBHART, AUSTRIA, PRESENTING AUTHOR · Landesklinikum St Pölten, St Poelten, Austria SUMMARY 4D Hip CT video evaluation reveals exactly impingent mechanism, joint kinematics and bone contact points. DATA Evidence for femoroacetabular impingement (FAI) as underlying mechanism for hip osteoarthritis is established. Conventional x ray images cannot determine the exact impingement mechanism. Even high end three dimensional computer tomographic video animation analysis with digital bone reassembling is unable to simulate real joint kinematics because lacking of coacting soft tissue. The purpose of our study was to develop an investigation method to reveal and exactly demonstrate location and time of bone contact during natural joint motion. Based on a real time resolved 3D CT examination of both hip joints, we visualize clinical impingement, motion and bone contact points with all interacting soft tissue structures of labrum acetabulare, teres ligament and joint capsule in place. Simultaneously coacting adjacent bone movements of the pelvis and contralateral femur are recorded with three and four dimensional computed animations (x-y-z and time axis) in a single 17,5 seconds movie from all directions. We proved that the complete pelvic bone lifts up the base and starts likewise internal rotation following the examined joint direction once it passed the zero rotation position (neutral zero method). The control video of asymptomatic hips shows no dislocation with absence of cam deformity or FAI contact points during 120° full range of active rotatory motion (maximum 70° external to 50° internal rotation) at zero degrees of hip flexion. FAI mechanism lead to 25 degrees relative internal rotation of the contra lateral hip joint where the leg stayed fixed to the base in supine position. Due to the growing use of arthroscopic and open

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procedures for FAI treatment our findings may have important implications on the general planning of individual bone resection. Paper 4: Cross-Sectional Analysis of Iliopsoas MuscleTendon Units at the Three Sites of Arthroscopic Tenotomies: An Anatomic Study BENJAMIN S. ZELLNER, MD, USA, PRESENTING AUTHOR JOSH R. BLOMBERG, MD, USA AND JAMES STEPHEN KEENE, USA · University of Wisconsin SUMMARY Cutting the iliopsoas tendon at the lesser trochanteric and transcapsular levels leaves 40 to 47% of the muscular portion of the muscle-tendon unit intact, and does not result in a complete release of the MTU. In contrast, releasing the tendon at the labrum leaves 60% of the MTU intact, and may result in similar high rates of recurrent snapping (⬃51%) seen with open proximal tendon releases. DATA Introduction: Arthroscopic iliopsoas tenotomies currently are performed at the level of the labrum, the femoral neck, and the lesser trochanter. To date, the composition of the iliopsoas muscle-tendon unit (MTU) has only been described at the level of the labrum.1 The purpose of this study was to determine the cross-sectional anatomy of the iliopsoas MTU at all three sites of arthroscopic iliopsoas tenotomies. Methods: Forty iliopsoas MTU dissections were performed on 20 embalmed cadavers. Each iliopsoas MTU was isolated at the level of the hip joint, freed from all surrounding soft tissues, and released from its insertion on the lesser trochanter. An 0-silk suture ligature was then used as described in a prior study,1 to make 6 circumferential measurements of the ilioposas MTU at: 1) its insertion on the lesser trochanter; 2) Ilizaturri’s site of transcapsular tendon release; and 3) Alpert et al’s release site at the level of the labrum.1 After the muscle was removed from the MTU, the circumference of the remaining tendon was measured at the same three locations. Results: Average circumference of the MTU at the level of the labrum (LB), the transcapsular release site (TC), and the lesser trochanter (LT) was 68.3 ⫾ 10.7 mm, 58 ⫾ 4.9 mm, and 45.7 ⫾ 5.5 mm, respectively. Average circumference of the iliopsoas tendon at these same levels was 27.1 ⫾ 4.0 mm, 31 ⫾ 2.4 mm, and 27.5 ⫾ 3.3 mm, respectively. Thus, at the level of the labrum, the transcapsular release site, and the lesser trochanter, the iliopsoas MTU was composed of 40% tendon/60% mus-