Orientation of the acetabular component influences wear, range of movement and the incidence of dislocation after total hip replacement (THR). During surgery, such orientation is often referenced to the anterior pelvic plane (APP), but APP inclination relative to the coronal plane (pelvic tilt) varies substantially between individuals. In contrast, the change in pelvic tilt from supine to standing (dPT) is small for nearly all individuals. Therefore, in THR performed with the patient supine and the patient's coronal plane parallel to the operating table, we propose that freehand placement of the acetabular component placement is reliable and reflects standing (functional) cup position. We examined this hypothesis in 56 hips in 56 patients (19 men) with a mean age of 61 years (29 to 80) using three-dimensional CT pelvic reconstructions and standing lateral pelvic radiographs. We found a low variability of acetabular component placement, with 46 implants (82%) placed within a combined range of 30° to 50° inclination and 5° to 25° anteversion. Changing from the supine to the standing position (analysed in 47 patients) was associated with an anteversion change < 10° in 45 patients (96%). dPT was < 10° in 41 patients (87%). In conclusion, supine THR appears to provide reliable freehand acetabular component placement. In most patients a small reclination of the pelvis going from supine to standing causes a small increase in anteversion of the acetabular component.
We performed a systematic literature review of mechanical and genetic factors of hip ontogeny. We focused on three fields that in recent years have advanced our knowledge of adult hip morphology: imaging, evolution, and genetics. WHERE ARE WE NOW?: Mechanical factors can be understood in view of human evolutionary peculiarities and may summate to load histories conducive to DHD. Genetic factors most likely act through multiple genes, each with modest effect sizes. Single genes that explain a DHD are therefore unlikely to be found. Apparently, the interplay between genes and load history not only determines hip morphotype, but also joint cartilage robustness ("cartilotype") and resistance to symptomatic OA. WHERE DO WE NEED TO GO?: We need therapies that can improve both morphotype and cartilotype. HOW DO WE GET THERE?: Better phenotyping, improving classification systems of hip morphology, and comparative population studies can be done with existing methods. Quantifying load histories likely requires new tools, but proof of principle of modifying morphotype in treatment of DDH and of cartilotype with exercise is available.
The surgical approach for total hip replacement (THR) depends on surgeon preference or the preference and experience of the surgeon with a specific approach. The aim of this study was to analyze the learning curve of the direct anterior approach (DAA) using the cumulative summation test for learning curve (LC-CUSUM). A retrospectively collected database of 400 THRs using the DAA (January 2010–September 2014) at a single center by a single surgeon. The learning curve was analyzed by determining the duration of surgery, blood loss, and number of complications. All 400 primary THRs were reviewed. Based on the LC-CUSUM, duration of surgery, and surgical failure, the learning curve plateau was achieved after the 19th surgery and the curve follows a substantially negative trend. The average duration of surgery changed significantly for the first hundred (78 minutes) to the last hundred (61 minutes). A significant decrease in blood loss was observed as well. A total of 17 (4.25%) complications occurred, with reduction of the complication rate as surgeons' experience increases. The authors' study did not show the long learning curve as previously described in the literature. The number of complications was small, and there was a significant decrease in duration of surgery, blood loss, and number of complications as surgeon's experience increases. The authors suggest that the educational environment of a teaching hospital, combined with the use of the DAA as a standard approach for all primary THRs and supervision of experienced surgeons, contribute to the favorable learning curve with a low complication rate.
Introduction: Release of some of the short external rotator tendons may be needed in the direct anterior approach (DAA) for Total Hip Arthroplasty (THA). It is unknown if these tendons heal. The purpose of this prospective study is to examine short external rotator tendon healing after release and the associated effect on muscle volume. In addition, we examined the relation with external rotation force and patient reported outcome measures (PROMs). Methods: In 21 DAA THA patients, preoperative MRI was compared with postoperative MRI at 6 weeks and 12 months. PROMs and rotation force of both hips were assessed. Tendon integrity and muscle volume of the obturator internus and piriformis were assessed on MRI using dedicated software. Results: In 5 patients all tendons remained intact, in 4 patients only the conjoined tendon was released and in 12 patients both the conjoined and piriformis were released. Obturator externus remained intact in all patients. In patients with tendon release, mean volume of obturator internus and piriformis muscle decreased 27% (SD 11) and 23% (SD 16) 6 weeks after surgery, respectively. Released tendons and muscle volume loss did not recover 12 months after surgery. We found no relation between tendon release and hip rotation force or PROMs. Conclusions: We found absent tendon healing and muscle volume loss when the conjoined or piriformis tendons were released. Although we found no relation between tendon detachment and hip force or PROMs, we have adapted our operative technique to make it more preserving for the piriformis.
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