1,721,129 research outputs found
Reverse shoulder arthroplasty leads to significant biomechanical changes in the remaining rotator cuff
Full text linkObjective: after reverse shoulder arthroplasty (RSA) external and internal rotation will often remain restricted. A postoperative alteration of the biomechanics in the remaining cuff is discussed as a contributing factor to these functional deficits.Methods: in this study, muscle moment arms as well as origin-to-insertion distance (OID) were calculated using three-dimensional models of the shoulder derived from CT scans of seven cadaveric specimens.Results: moment arms for humeral rotation are significantly smaller for the cranial segments of SSC and all segments of TMIN in abduction angles of 30 degrees and above (p ≤ 0.05). Abduction moment arms were significantly decreased for all segments (p ≤ 0.002). OID was significantly smaller for all muscles at the 15 degree position (p ≤ 0.005), apart from the cranial SSC segment.Conclusions: reduced rotational moment arms in conjunction with the decrease of OID may be a possible explanation for the clinically observed impaired external and internal rotation
Validation of CT image-based software for three-dimensional measurement of acetabular coverage profile
No full textBackground: plain radiography, 2-dimensional (2D) magnetic resonance imaging (MRI), and computed tomography (CT) do not precisely display morphology and acetabular coverage in developmental dysplasia of the hip or pincer-type femoroacetabular impingement. Pelvic position and pelvic tilt affect assessment of the acetabular parameters, leading to misinterpretation.Objective: we tested a 3-dimensional (3D) CT evaluation script to calculate the crossover sign (COS), acetabular coverage and morphology.Methods: to test the method, we constructed a phantom pelvic model, in which the acetabulum was mounted at different coverages of the femoral head, and simulated a COS and the acetabular morphology. Additionally we examined the reliability and objectivity of this method in ten patients with CT scans of the pelvis for conditions unrelated to hip disorders.Results: we obtained an average accuracy of the 3D CT evaluation script of -0.37∘ (range -3.84 to 3.88; SD ± 1.43) for morphology, and 0.002% (range -7.28% to 6.90%; SD ± 1.60%) for coverage of the femoral head. Significant correlation between the expected and calculated COS (p= 0.01) was found.Conclusions: our 3D CT evaluation script permits precise evaluation of the acetabular coverage profile, the presence or absence of a COS and acetabular morphology, independent of patient positioning or pelvic tilt.</p
Validation of a CT image based software for three-dimensional measurement of acetabular cup orientation
No full textThe purpose of our study was to develop a simple and reproducible method for calculating post-operative acetabular cup position based upon computed tomographic images. Next, we sought to examine the reliability, objectivity and accuracy of this method. We developed a 3D CT evaluation software based upon Amira(R) (data visualisation, analysis and modelling software) to calculate the abduction and anteversion of the acetabular cup relative to the APP (anterior pelvic plane). To test the accuracy of the method, we constructed a special phantom pelvic model as the gold standard, in which the acetabulum was mounted at various abduction and anteversion angles that had previously been measured digitally. This phantom was then CT scanned in 12 different cup positions (30 degrees to 50 degrees abduction, 0 degrees to 30 degrees anteversion) and then evaluated using the 3D CT evaluation software. In addition, we also examined the reliability and objectivity of this method in 10 patients following implantation of a hip prosthesis, as a clinical trial. We observed an average accuracy of the 3D CT evaluation software of -0.3 degrees (range -1.4 degrees to 1.3 degrees ; SD 0.6 degrees ) for abduction and 0.2 degrees (range -1.4 degrees to 1.4 degrees ; SD 0.6 degrees ) for anteversion compared with the gold standard. Moreover, a high intra -and interindividual agreement in the resulting ICC well above 0.8 for abduction and abduction values in the phantom study and the clinical trial were observed. This study found that the 3D CT evaluation software provides high reliability, objectivity and accuracy. Thus, the 3D CT software is a method that permits very precise evaluation of the post-operative cup position independent of patient positioning or pelvic til
The direct lateral approach: impact on gait patterns, foot progression angle and pain in comparison with a minimally invasive anterolateral approach
No full textINTRODUCTION: Minimally invasive total hip arthroplasty has been successfully introduced in the past decade. Nevertheless, standard approaches such as the direct lateral approach are still commonly used in orthopaedic surgery due to easy handling, good intra-operative overview and low complication rates. However, a frequent occurrence of fatty atrophy within the anterior third of the gluteus medius muscle has been demonstrated when using the modified direct-lateral approach (mDL), which may be associated with a reduction in function, limitation of internal leg rotation, gait disorders and pain. The question addressed in this study is whether mDL-approach leads to unfavourable changes in foot progression angle (FPA), gait and to more postoperative pain compared with a minimally invasive anterolateral approach (ALMI). METHODS: Thirty patients with primary osteoarthritis of the hip were recruited for this study. All subjects received an uncemented THA (Alloclassic((R))-Zweymuller stem, Allofit((R)) Cup, FA Zimmer((R))), 15 through an ALMI-approach and 15 via the mDL-approach. Gait analyses were performed both preoperatively and 3 months after surgery to measure FPA, step length, stance duration, cadence and walking speed. Additionally, the Harris-Hip Score, pain according to the visual analogue scale and the Trendelenburg sign were evaluated. RESULTS: No influence of the surgical approach could be observed on the gait patterns or FPA. Furthermore, neither increased external rotation of the limb nor restriction of internal rotation during walking could be established. Pain and Harris-Hip Score did not differ significantly between the two groups. CONCLUSION: In comparison with an ALMI approach, the mDL approach did not lead to a change in FPA postoperatively. No detrimental effect could be found on the gait pattern or pain after surgery. Based on these measurements, the minimally invasive anterolateral approach did not appear to provide functional benefits in outcome over the mDL approach. Consequently, both surgical approaches seem to be equally applicable approaches with good to very good functional results
Standardized AP radiographs do not provide reliable diagnostic measures for the assessment of acetabular retroversion
No full textDiagnosis of acetabular retroversion is essential in femoroacetabular impingement (FAI), but its assessment from radiographs is complicated by pelvic tilt and the two-dimensional nature of plain films. We performed a study to validate the diagnostic accuracy of the crossover sign (COS) and the posterior wall sign (PWS) in identifying acetabular retroversion. COS and PWS were evaluated from radiographs and computed tomography (CT) scans as the standard of reference in 50 hips of subjects with symptoms of FAI. A CT-based method using 3-D models was developed to measure the COS, PWS, true acetabular version and pelvic tilt relative to the anterior pelvic plane. The new CT-based method aimed to eliminate errors resulting from variations in the position and orientation of the pelvis during imaging. A low level of agreement for COS and PWS was found between radiographs and CT scans. A positive COS strongly correlated with pelvic tilt. These results suggest that COS and PWS determined from anteroposterior (AP) radiographs are considerably limited by pelvic tilt and inherent limitations of radiographs. Their use as the sole basis for deciding whether or not surgical intervention is indicated seems questionabl
Real time visualization of femoroacetabular impingement and subluxation using 320-slice computed tomography
No full textWe visualized extreme ranges of motion of the hip and located femoroacetabular impingement (FAI) and subluxations using 4dimensional (D) volume computed tomography (CT). In dynamic 4D CT, 30 patients with hip pain (>3 months) and positive clinical and radiological signs of impingement were prospectively analyzed. The investigations were performed in flexion, abduction, and external rotation. The accuracy of the CT visualization of FAI was compared with the intraoperative findings during surgical dislocation, which served as the gold standard. Compared to the intraoperative visualization of FAI, the dynamic CT images showed a high degree of accuracy. 4D CT is a suitable method to dynamically visualize the functional consequences of anatomical FAI pathologies. The location of impingement can be accurately determined, and when combined with information about possible labral tears and chondral damage supplied by magnetic resonance arthrography, allows the surgeon to select the optimal surgical access and plan the required operation for minimal invasiveness
Ultrasound-based computer navigation of the acetabular component: a feasibility study
No full textThis feasibility study investigated the accuracy of anterior pelvic reference plane (APP) registration and acetabular cup orientation in two cadavers with different BMIs. Method Five observers each registered the APP five times in the 2 cadavers (BMIs: 32 kg/m² and 25 kg/m²) using an ultrasound-based navigation system. By comparison against the CT-derived reference landmarks, the errors in determining the individual landmarks defining the APP, as well as the resulting errors in the orientation of the APP and the acetabular cup orientation were determined. Results Across all measurements obtained with the ultrasound navigation system, the errors in rotation and version in determining the APP were 0.5° ± 1.0° and ?0.4° ± 2.0°, respectively. The cup abduction and anteversion errors determined from all measurements of the five investigators for both cadavers together were ?0.1° ± 1.0° and ?0.4° ± 2.7°, respectively. The data further demonstrated a high reproducibility of the measurements for the resulting cup adduction and anteversion angle. Conclusion Our preliminary results confirm that ultrasound navigation is a highly accurate tool that allows a reproducible registration of the APP and thereby enables accurate and precise intraoperative determination of the acetabular cup orientation also in patients with increased BMI
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Influence of prosthesis design and implantation technique on implant stresses after cementless revision THR
Full text linkBACKGROUND: Femoral offset influences the forces at the hip and the implant stresses after revision THR. For extended bone defects, these forces may cause considerable bending moments within the implant, possibly leading to implant failure. This study investigates the influences of femoral anteversion and offset on stresses in the Wagner SL revision stem implant under varying extents of bone defect conditions. METHODS: Wagner SL revision stems with standard (34 mm) and increased offset (44 mm) were virtually implanted in a model femur with bone defects of variable extent (Paprosky I to IIIb). Variations in surgical technique were simulated by implanting the stems each at 4 degrees or 14 degrees of anteversion. Muscle and joint contact forces were applied to the reconstruction and implant stresses were determined using finite element analyses. RESULTS: Whilst increasing the implant's offset by 10 mm led to increased implant stresses (16.7% in peak tensile stresses), altering anteversion played a lesser role (5%). Generally, larger stresses were observed with reduced bone support: implant stresses increased by as much as 59% for a type IIIb defect. With increased offset, the maximum tensile stress was 225 MPa. CONCLUSION: Although increased stresses were observed within the stem with larger offset and increased anteversion, these findings indicate that restoration of offset, key to restoring joint function, is unlikely to result in excessive implant stresses under routine activities if appropriate fixation can be achieved
- …
