A CT-based method (''HipMotion'') for the noninvasive three-dimensional assessment of femoroacetabular impingement (FAI) was developed, validated, and applied in a clinical pilot study. The method allows for the anatomically based calculation of hip range of motion (ROM), the exact location of the impingement zone, and the simulation of quantified surgical maneuvers for FAI. The accuracy of HipMotion was 0.7 AE 3.18 in a plastic bone setup and À5.0 AE 5.68 in a cadaver setup. Reliability and reproducibility were excellent [intraclass correlation coefficient (ICC) > 0.87] for all measures except external rotation (ICC ¼ 0.48). The normal ROM was determined from a cohort of 150 patients and was compared to 31 consecutive hips with FAI. Patients with FAI had a significantly decreased flexion, internal rotation, and abduction in comparison to normal hips ( p < 0.001). Normal hip flexion and internal rotation are generally overestimated in a number of orthopedic textbooks. HipMotion is a useful tool for further assessment of impinging hips and for appropriate planning of the necessary amount of surgical intervention, which represents the basis for future computerassisted treatment of FAI with less invasive surgical approaches, such as hip arthroscopy. ß

Introduction: A novel computerized algorithm for hip joint motion simulation and collision detection, called the Equidistant Method, has been developed. This was compared to three pre-existing methods having different properties regarding definition of the hip joint center and behavior after collision detection. It was proposed that the Equidistant Method would be most accurate in detecting the location and extent of femoroacetabular impingement. Materials and Methods: Five plastic pelves and ten plastic femora with modified acetabula and head-neck junctions, allowing for 50 different morphologic combinations, were examined, along with six cadaver hips. First, motions along anatomically relevant paths were performed. These motions were tracked by a navigation system and impingement locations were digitized with a pointer. Subsequently, previously generated 3D models of all the specimens, together with the recorded anatomic motion paths, were applied to all four simulation algorithms implemented in a diagnostic computer application. Collisions were detected within the motion paths, and the linear and angular differences regarding the location as well as the size of the detected impingement areas were compared and analyzed. Results: The Equidistant Method detected impingement with significantly higher linear and angular accuracy compared to the other methods ( p 5 0.05). The size of the detected impingement area was smaller than that detected with the other methods, but this difference was not statistically significant. Conclusions: The increased accuracy of the Equidistant Method is achieved by implementing a dynamic hip joint center, more closely resembling the natural characteristics of the hip joint. Clinical application of this algorithm might serve as a diagnostic adjunct and support in the planning of joint-preserving surgery in patients with femoroacetabular impingement.

Background Legg-Calvé-Perthes disease (LCPD) often results in a deformity that can be considered as a complex form of femoroacetabular impingement (FAI). Improved preoperative characterization of the FAI problem based on a noninvasive three-dimensional computer analysis may help to plan the appropriate operative treatment. Questions/purposes We asked whether the location of impingement zones, the presence of additional extraarticular impingement, and the resulting ROM differ between hips with LCPD and normal hips or hips with FAI. Methods We used a CT-based virtual dynamic motion analysis based on a motion algorithm to simulate the individual motion for 13 hips with LCPD, 22 hips with FAI, and 27 normal hips. We then determined the motion and impingement pattern of each hip for the anterior (flexion, adduction, internal rotation) and the posterior impingement tests (extension, adduction, external rotation). Results The location of impingement zones in hips with LCPD differed compared with the FAI/normal groups. Intra-and extraarticular impingement was more frequent in LCPD (79% and 86%, respectively) compared with normal (15%, 15%) and FAI hips (36%, 14%). Hips with LCPD had decreased amplitude for all hip motions (flexion, extension, abduction, adduction, internal and external rotation) compared with FAI or normal. Conclusions Hips with LCPD show a decreased ROM as a result of a higher prevalence of intra-and extraarticular FAI. Noninvasive assessment of impingement characteristics in hips with LCPD may be helpful in the future for establishment of a surgical plan.

Size and shape of the lunate surface differs substantially among different types of pincer impingement. In contrast to hips with protrusio acetabuli, retroverted and deep hips do not have an increased size of the lunate surface. Acetabular rim trimming in retroverted and deep hips should be performed with caution. Based on our results, acetabular reorientation would theoretically be the treatment of choice in retroverted hips.

Background Residual acetabular dysplasia is seen in combination with femoral pathomorphologies including an aspherical femoral head and valgus neck-shaft angle with high antetorsion. It is unclear how these femoral pathomorphologies affect range of motion (ROM) and impingement zones after periacetabular osteotomy. Questions/purposes (1) Does periacetabular osteotomy (PAO) restore the typically excessive ROM in dysplastic hips compared with normal hips; (2) how do impingement locations differ in dysplastic hips before and after PAO compared with normal hips; (3) does a concomitant camtype morphology adversely affect internal rotation; and (4) does a concomitant varus-derotation intertrochanteric osteotomy (IO) affect external rotation? Methods Between January 1999 and March 2002, we performed 200 PAOs for dysplasia; of those, 27 hips (14%) met prespecified study inclusion criteria, including availability of a pre-and postoperative CT scan that included the hip and the distal femur. In general, we obtained those scans to evaluate the pre-and postoperative acetabular and femoral morphology, the degree of acetabular reorientation, and healing of the osteotomies. Three-dimensional surface models based on CT scans of 27 hips before and after PAO and 19 normal hips were created. Normal hips were obtained from a population of CT-based computerassisted THAs using the contralateral hip after exclusion of symptomatic hips or hips with abnormal radiographic anatomy. Using validated and computerized methods, we then determined ROM (flexion/extension, internal-[IR]/ external rotation [ER], adduction/abduction) and two motion patterns including the anterior (IR in flexion) and posterior (ER in extension) impingement tests. The computed impingement locations were assigned to anatomical locations of the pelvis and the femur. ROM was calculated separately for hips with (n = 13) and without (n = 14) a cam-type morphology and PAOs with (n = 9) and without (n = 18) a concomitant IO. A post hoc power analysis based on the primary research question with an alpha of 0.05 and a beta error of 0.20 revealed a minimal detectable difference of 4.6°of flexion. Results After PAO, flexion, IR, and adduction/abduction did not differ from the nondysplastic control hips with the numbers available (p ranging from 0.061 to 0.867). Extension was decreased (19°± 15°; range, À18°to 30°versus 28°± 3°; range, 19°-30°; p = 0.017) and ER in 0°flexion was increased (25°± 18°; range, À10°to 41°versus 38°± 7°; range, 17°-41°; p = 0.002). Dysplastic hips had a One author (MT) has received funding from the Swiss National Science Foundation (SNSF). All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research 1 editors and board members are on file with the publication and can be viewed on request. Clinical Orthopaedics and Related Research1 neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDAapproval status, of any drug or ...

No abstract

No abstract

No abstract