Acetabular Rim Disorders: Epidemiology, Etiology, Management, and Outcomes.

¼ Anatomic disorders of the acetabular rim are a common, correctable source of hip pain in younger patients.¼ Some common conditions of involving abnormal acetabular rim morphology include developmental dysplasia of the hip, pincer-type femoroacetabular impingement, acetabular protrusion, and acetabular retroversion.¼ Treatment option for these conditions were historically limited to open osteotomy and osteoplasty procedures; however, there is increasing use of arthroscopic intervention for these patients.¼ Arthroscopic intervention has demonstrated short-term success in a variety of focal acetabular rim disorders; however, further research is needed to determine the long-term outcomes of these procedures and their utility in more global pathology.

[Impingement Free Motion in Total Hip Arthroplasty - How Can We Implement It?]. / Impingementfreie Bewegung nach Hüft-TEP - wie realisieren?

INTRODUCTION: Prosthetic impingement and insufficient soft tissue tension are still the most important factors responsible for early dislocation after total hip arthroplasty. Optimal positioning of both prosthetic components, the stem and the socket, optimising their design and restoring individual hip biomechanics, are of the upmost importance in reducing the risk of impingement. This study describes the concept of the combined safe zone (cSafe-Zone) that provides guidelines for the optimal positioning of both components. MATERIAL AND METHODS: A computerised CAD model of a total hip prosthesis was used to systematically investigate the effect of design parameters, such as head-to-neck ratio, CCD shaft angle, as well as positioning parameters, such as cup inclination and cup anteversion and stem antetorsion, on the range of motion. We looked for all positioning combinations that allow the predefined range of movement (= iROM, intended range of movement) and thus define the combined safe zone. The analysis was carried out with straight stems, anatomical and short stems. The size of the cSafe-Zone was chosen as the optimising criterion and the largest cSafe-Zone was considered to define the optimal component positions. These optimal relative orientations of cup and stem were engraved onto the surface of the navigation trial head and used to position the cup during surgery. RESULTS: This new combined safe zone is not static but dynamic; it varies in size and position and is specific for each prosthesis system. High stem antetorsion should be combined with lower cup anteversion and vice versa. Thus, cup anteversion and stem antetorsion are complementary. CCD shaft angles above 135° reduce the size of the cSafe-Zone and are therefore not recommended. Larger head sizes allow lower cup inclinations, i.e. the recommended cup inclination for a 28 mm head is 40 to 45°, for 32 mm 38 to 42° and for 36 mm 35 to 40°. This also increases the so-called jumping distance. Anatomical stems require less cup anteversion than straight stems. CONCLUSION: The concept of combined safe-zone delivers clear guidelines how to position both components of a total hip prosthesis in order to maximise range of movement and to reduce the risk of prosthetic impingement. It is the basis of the stem-first surgical technique. Computer-based navigation or mechanical instruments can be used to implement this new concept in surgical practice.

Assessment of congruence and impingement of the hip joint in professional ballet dancers: a motion capture study.

BACKGROUND: Early hip osteoarthritis in dancers could be explained by femoroacetabular impingements. However, there is a lack of validated noninvasive methods and dynamic studies to ascertain impingement during motion. Moreover, it is unknown whether the femoral head and acetabulum are congruent in typical dancing positions. HYPOTHESIS: The practice of some dancing movements could cause a loss of hip joint congruence and recurrent impingements, which could lead to early osteoarthritis. STUDY DESIGN: Descriptive laboratory study. METHODS: Eleven pairs of female dancer's hips were motion captured with an optical tracking system while performing 6 different dancing movements. The resulting computed motions were applied to patient-specific hip joint 3-dimensional models based on magnetic resonance images. While visualizing the dancer's hip in motion, the authors detected impingements using computer-assisted techniques. The range of motion and congruence of the hip joint were also quantified in those 6 recorded dancing movements. RESULTS: The frequency of impingement and subluxation varied with the type of movement. Four dancing movements (développé à la seconde, grand écart facial, grand écart latéral, and grand plié) seem to induce significant stress in the hip joint, according to the observed high frequency of impingement and amount of subluxation. The femoroacetabular translations were high (range, 0.93 to 6.35 mm). For almost all movements, the computed zones of impingement were mainly located in the superior or posterosuperior quadrant of the acetabulum, which was relevant with respect to radiologically diagnosed damaged zones in the labrum. All dancers' hips were morphologically normal. CONCLUSION: Impingements and subluxations are frequently observed in typical ballet movements, causing cartilage hypercompression. These movements should be limited in frequency. CLINICAL RELEVANCE: The present study indicates that some dancing movements could damage the hip joint, which could lead to early osteoarthritis.