Introduction. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the precision and accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. All surgeries were done by single surgeon (KD) using similar technique. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Precision, accuracy, sensitivity and specificity were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. A p value of <0.05 was considered significant for evaluation. Results. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76° (SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high precision and specificity for determining cup abduction and anteversion (precision >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46mm (SD, 5.68) and −1.07mm (SD, 5.75) on radiograph evaluation and 5.41mm (SD, 5.11) and −2.24mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value > 0.2). Radiograph and navigation had a mean difference of 1.01mm (SD, 2.83) for offset measurements and a mean difference of 1.05mm (SD, 4.37) for postop limb length assessment. Discussion. To the best of our knowledge this is the largest single surgeon study of navigated THA. We found that computer navigation assessment of acetabular cup abduction and anteversion and limb length and offset restoration has high probability of predicting correct placement of implants. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

Introduction:. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods:. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Sensitivity, specificity, accuracy and PPV were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. Results:. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76°(SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high PPV and specificity for determining cup abduction and anteversion (PPV >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46 mm (SD, 5.68) and −1.07 mm (SD, 5.75) on radiograph evaluation and 5.41 mm (SD, 5.11) and −2.24 mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value >0.2). Radiograph and navigation had a mean difference of 1.01 mm (SD, 2.83) for offset measurements and a mean difference of 1.05 mm (SD, 4.37) for postop limb length assessment. Discussion:. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

Introduction:. Acetabular cup position is an important factor in successful total hip arthroplasty (THA). Optimal cup placement requires surgeons to possess an accurate perception of pelvic orientation during cup impaction, however, varying pelvic anatomy and limited visual cues in the surgical field may interfere with this process. The purpose of this study was to evaluate the utility of an inertial measurement unit (IMU) in monitoring pelvic position during THA. Materials & Methods:. Ten patients scheduled to undergo THA were IRB-approved and consented by four surgeons. A small IMU was placed over the patient's sacrum pre-operatively and zeroed in standing position. Pelvic orientation data was streamed and captured wirelessly throughout the procedure. Surgeons were blinded to all data throughout the study period. Prior to cup impaction, the surgeon indicated his intended cup abduction angle and the degree to which the cup impactor was manipulated to compensate for perceived AP pelvic tilt. The degree of pelvic tilt as determined by the IMU (angle β) was then recorded (Figure 1). AP-pelvis radiographs were measured in Martell Hip Analysis Suite post-operatively to calculate the cup abduction angle, which was then compared to the surgeon's intended abduction angle to determine surgeon accuracy. To predict the final cup abduction angle, the degree of pelvic tilt recorded by the IMU (angle β) was subtracted from the abduction angle of the cup impactor (angle α) that was positioned using the OR table as a reference (Figure 1). This value was then compared to the measured post-operative cup abduction angle in order to assess the accuracy of the IMU in measuring pelvic tilt. Surgeon accuracy and IMU accuracy were compared to determine if the IMU was more or less effective than surgeon perception at determining pelvic tilt. Results:. The mean intended abduction angle indicated by the surgeons intraoperatively was 43.7° (range 40°–45°), while the mean measured post-operative abduction angle was 40.1° (range 25.9°–49.4°). In five of the cases, the surgeon's post-operative abduction angle fell within 2° of his intended abduction angle. One cup was placed at a higher than intended abduction angle (4.4°), and four cups were placed in lower than intended abduction angles by an average of 10.8° (range 3.9°–19.1°). Film analysis revealed that surgeons placed the acetabular cup on average 5.4 ± 6.0° from their intended abduction angle (range 0.3°–19.1°). Following analysis of the IMU offset data, it was observed that the IMU deviated on average 3.1 ± 2.6° (range 0.7°–7.2°) from its expected orientation value. The IMU deviated more than 2° from expected pelvic tilt in five cases. Discussion:. The IMU was able to ascertain AP pelvic tilt to a higher degree of accuracy than four surgeons using standard surgical techniques. A system in which the pelvis could be monitored and adjusted intraoperatively based on accurate IMU data would allow the surgeon to place the pelvis in optimal position prior to cup impaction, which could potentially increase overall cup positioning accuracy. More data is needed to confirm these results

Introduction. This study reports outcomes of primary and revision total hip arthroplasties of a recalled metal-on-metal (MOM) monoblock prosthesis performed by a single surgeon. Methods. We performed a retrospective review of all patients who underwent both primary and revision total hip arthroplasties at our institution between 2006 and 2014. Only those patients who underwent primary recalled MOM monoblock prosthesis placement and/or revision of the recalled prosthesis were included. We evaluated revision group versus non-revision group for age, BMI, gender, existence of medical comorbidities, primary cup abduction and anteversion, primary combined angle, post-operative complications, cobalt and chromium ion levels, and Harris Hip Scores. Student t-test was used to compare groups. Results. During the study period, 105 patients underwent 115 primary total hip arthroplasties with the recalled system. Thirty-six patients underwent 40 revisions surgeries for pain, high metal ions, infection, aseptic loosening, failure of ingrowth, and/or pseudotumor. The revision rate was 34.8%. Except for a higher percentage of women undergoing revision (17.4% vs 50%, p=0.0002), there were no significant differences in patient demographics, medical comorbidities, or pre-operative Harris Hip Scores (Table 1). Revision group showed higher cup abduction angles (47.8 vs 42.4, p = 0.005), smaller average cup size (53.3 vs. 55.2, p = 0.003), smaller average femoral component size (4.7 vs 5.6, p = 0.02, respectively), and lower post-operative Harris Hip Scores (87.9 vs 93.8, p = 0.0007). The revision group had higher cobalt levels (34.5 vs 5.8, p = 0.00003) and higher chromium levels (14.0 vs 1.3, p = 0.00003). There were five post-operative complications in the revision group (2 infections, 2 dislocations, and one DVT) versus one DVT in the non-revision group (p=0.01). Harris Hip Scores for revision surgeries increased from a mean of 44.2 pre-operatively to 74.9 post-operatively (p=1.45×10. −5. ). Conclusion. This study presents 115 primary total hip arthroplasties and 40 revisions performed by a single surgeon at our institution. To our knowledge, this is the largest single-surgeon study reported in the literature. Hips requiring revision had significantly higher cup abduction angles, smaller cup and femoral component sizes, lower post-operative Harris Hip scores, and higher metal ion levels. Age, BMI and comorbidities did not contribute to revision in our study; however, there was a higher chance of undergoing revision if you are a woman (p=0.0002). There was a 30.7 mean improvement in Harris Hip Score after revision

Purpose. Ceramic-on-ceramic bearings in total hip arthroplasty (CoC THA) have theoretical advantages of wear resistance and favorable biocompatibility of ceramic particles to the surrounding bony and soft tissue. Long-time durability of CoC THA has been expected, however, clinical results over 10 years after operation were scarcely reported. In the present study, clinical results at follow of 10 years were examined for CoC THAs with a changeable femoral neck which allowed correction of anteversion of the femoral component in cases with abnormal femoral anteversion in dysplastic hips. Methods. During 1997 and 2000, 203 cementless CoC THAs in 158 patients were conducted in our hospital. Six patients died because of unrelated causes and 5 patients were lost to followup, and the remaining 188 hips in 147 patients were analyzed at the mean followup period of 10.8 years (3.7 to 13.5). There were 24 men and 123 women, and the average age at operation was 54 years (26 to 73). The hip diseases for operation were osteoarthritis in 165 hips, osteonecrosis of the femoral head in 21 hips and failure of hemiarthroplasty in 2 hips. The operation was performed in the lateral position through the posterior approach without trochanteric osteotomy. The articulation was composed of Biolox forte alumina liner fitted into beads-coated hiemispherical titanium shell, and a 28-mm Biolox forte alumina femoral head (Cremascoli). The femoral component was either AnCA stem or custom-designed stem, coupled with a modular neck allowing selection of 5 variable offsets and anteversions (Cremascoli). Clinical and radiological findings, and complications during the followup period were analyzed. Results. During the follow-up, 8 hips were revised, due to repeated dislocation (2 hips), periprosthetic fracture (1 hips), cup loosening (1 hip), fracture of ceramic liner rim (2 hips), and cup loosening along with ceramic liner rim fracture (2 hips). Cup abduction angle of the 4 cases with ceramic liner rim fracture were high at 49 degrees or more, as compared with the mean cup abduction angle of 41 degrees in the other hips without ceramic fracture. The survival rate at 10 years was 96.0 % when failure was revision. In the hips other than the revised cases, 6 hips showed cup loosening and no hip showed stem loosening on radiographs. Osteolysis was seen in 3 hips around the cup and 4 hips around the stem. Nineteen patients (10%) complained of abnormal noises around the hip, but most of the noises were click sound. Discussion. The 10-year results of cementless CoC THAs with a modular neck were favorable with few cases of osteolysis. However, relatively high frequency of cup loosening may be a concern, since increased cup abduction angle associated with cup loosening may cause ceramic liner fracture

Introduction. Total hip replacement (THR) is one of the most widely used and most successful orthopedic procedures performed in developed countries. The burden of revision surgery, however, has become a major issue in terms of both volume and cost. Technical errors at the time of the index operation are known to be associated with an increased rate of revision. Statistical methods, such as the CUSUM test, which have been developed for the manufacturing industry to monitor the quality of products, have come to the attention of health-care workers as a result of centers with protracted periods of inadequate performance. In orthopedics, these methods have been used to monitor the quality of total hip replacement in a tertiary care department using conventional imaging techniques. Biplane low-dose X-ray imaging (EOS) may allow an easy, patient-friendly, way to retrieve data on the position of implants immediately postoperatively. Therefore real-time feedback is provided to surgeons and performance adjusted accordingly. Objectives. To assess the usefullness of EOS imaging in providing the position of implants immediately postoperatively. Methods. Thirty-six patients who underwent a primary hip replacement at a tertiary care department had a standing EOS acquisition before discharge (around day 5). The following parameters were collected: cup abduction, cup anteversion, leg length, stem anteversion, stem inclination. Cup inclination was considered inadequate if more than 55 degrees or less than 35 degrees; cup abduction was considered inadequate if more than 30 degrees or less than 0 degrees; leg length was considered inadequate if more than 1cm; stem anteversion was considered inadequate if more than 30 degrees of less than 0 degrees; stem inclination was considered inadequate if more than 4 degrees varus or valgus. A procedure was considered inadequate if any criterion was outside the appropriate range. A CUSUM test was used to detect inadequate performance for each criterion and for the whole procedure (more than 20% of the implants poorly positioned). Results. On this preliminary sample of 36 patients only cup inclination demonstrated to be inadequate. Other parameters were within the expected limits. The acquisition of images proved to be easy, without interrupting the flow of patient care and physician work. Conclusions. Biplane low-dose X-ray imaging (EOS) provides an easy way to continuously evaluate the quality of THR implant positioning at a tertiary care department

Introduction. Orientation of the acetabular component in total hip arthroplasty has been shown to influence component wear, stability, and impingement. Freehand placement of the component can lead to widely variable radiographic outcomes. Accurate abduction, in particular, can be difficult in the lateral decubitus position due to limited ability to appreciate and control positional obliquity of the pelvis. A CT-based mechanical navigation device has been shown to decrease cup placement error. This is an independent report of a single-surgeon's radiographic results using the device to control cup abduction. Patients and Methods. Sixty-four (64) consecutive elective THRs in 58 patients were performed via a supercapsular percutaneously-assisted (SuperPATH) surgical approach. Intraoperatively, the acetabular components were aligned with the aid of the CT-based mechanical navigation device (HipXpert; Surgical Planning Associates, Medford, MA). The cup orientation was then further adjusted to ensure that the anterior rim of the acetabular component was not prominent to avoid psoas impingement. Postoperatively, radiographic abduction was measured on standing postoperative radiographs. Results. Measured on standing postoperative radiographs, the cup radiographic abduction angle averaged 42.7° with a standard deviation of ± 3.9° and a range of 35° to 51°. Conclusions. Total hip arthroplasty using a CT-based navigation device as a guide for abduction led to cup implantation within a very narrow abduction range. This navigation device deserves more widespread interest and study, as acetabular component malposition remains a major concern in THR

Purpose. Placement of the acetabular cup in accurate and optimal position is important in total hip arthroplasty (THA) to obtain satisfactory result. On the other hand, inaccurate manual cup placement with conventional cup placement guide was reported. We therefore have been applied the mechanical acetabular alignment guide for accurate cup placement. The purpose of this study was to validate the accuracy of the acetabular alignment guide for total hip arthroplasty. Materials and methods. Between 2003 and 2014, 52 primary THAs were performed in 48 patients with using the acetabular alignment guide by one surgeon (HT). There were 42 female and 6 male with a mean age at operation of 71.1 years old (47 to 91). The original diagnosis were osteoarthritis in 43 patients (46 hips), and avascular necrosis of femoral head in 5 patients (6 hips). Used acetabular implants were Stryker® Trident AD HA cup in 24 hips and Wright medical® Acetabular Cup System in 28 hips. After completion of anesthesia, half pins were inserted at the both anterior superior iliac spine vertically and the frame was attached to the pins horizontally in supine position. Then, the patients were placed in lateral decubitus position. Finally, the alignment rod, which indicated the optimal direction of the cup (abduction angle 40°, ante-version angle 20°), was connected to the frame. All operations were done by postero-lateral approach. Assessment of the cup abduction angle and ante-version angle was performed by Lewinnek's method using postoperative AP radiograph in supine position. Results. The average cup abduction angle was 41.9±6.1° and ante-version angle was 15.2±4.1° (corrected ante-version angle was 20.2±4.1°). In 49 hips (94%) out of 52 hips, cup was placed within safe zone which was described by Lewinnek (from 30° to 50° of abduction angle, from 5° to 25° of ante-version angle). We had only 3 outliers which abduction angles were 25, 27, and 52 degrees. In terms of the ante-version angle, there was no outlier. Discussion. Our study showed that acetabular alignment guide could help accurate cup placement in THA. To hold the patients in true lateral decubitus position during THA is quite difficult and pelvis can tilt intraoperatively, sometimes resulting in malposition of the cup. The acetabular alignment guide used in this study was stabilized firmly to both iliac crests with two half pins of external fixator. Once we attach a cup angle guide to the acetabular guide frame in supine position, we can know the exact direction for cup placement without being affected by change of the pelvic orientation. We conclude that the acetabular alignment guide is useful tool in case of lateral decubitus position for THA

Background. High cup abduction angles generate increased contact stresses, higher wear rates and increased revision rates. However, there is no reported study about the influence of cup abduction on stresses under head lateralisation conditions for ceramic-on-Ceramic THA. Material and method. A finite elements model of a ceramic-on-ceramic THA was developed in order to predict the contact area and the contact pressure, first under an ideal regime and then under lateralised conditions. A 32 mm head diameter with a 30 microns radial clearance was used. The cup was positioned with a 0°anteversion angle and the abduction angle was varied from 45° to 90°. The medial-lateral lateralisation was varied from 0 to 500 microns. A load of 2500 N was applied through the head center. Results. For 45° abduction angle, edge loading appeared above a medial-lateral separation of 30 μm. Complete edge loading was obtained above 60 μm medial-lateral separation. For 45 degrees inclination angle, as the lateralisation increased, the maximal contact pressure increased from 66 MPa and converged to an asymptotic value of 205 MPa. A higher inclination angle resulted in a higher maximum contact pressure. However, this increase in contact pressure induced by higher inclination angle, became negligible as the lateral separation increased. Discussion Both inclination angle and lateral displacement induced a large increase in the stresses in Ceramic-on-Ceramic THA. Edge loading appeared for a small lateralisation. The influence of acetabular inclination angle became negligible for a lateral displacement above 240 μm, as the stresses reached an asymptotic value

Introduction. Uncemented components necessitate accurate intraoperative assessment of size to avoid complications such as calcar fracture and subsidence whilst maintaining bone stock on the acetabular side. Potential problems can be anticipated pre-operatively with the use of a templating system. We proposed that pre-operative digital templating could accurately assess femoral and acetabular component size. Methods. Pre-operative templating data from 100 consecutive patients who received uncemented implants (Trident cup, Accolade stem) and who were operated on by the senior author were included in the study. Calibrated pelvis anterior-posterior X-rays were templated with Orthoview™ software. Demographic data, templating data (stem and cup size, femoral neck cut), operative records (actual stem and cup size, head size) and post-operative data (femoral stem alignment, radiographic leg length, acetabular cup abduction angle) were collected. Results. There were 51 males and 49 females with a mean age of 60 yrs (SD = 7.3 yrs). Seventy five percent of stems were templated to within 0.5 size and 98% to within 1 size. A total of 80% of cups were templated to within 2mm and 98% to within 4mm. 62% of head length was accurately template. Seven patients were converted from a templated 132° to a 127° femoral prosthesis neck angle. The acetabulum cup abduction angle was 45° (SD = 4.81) and stem alignment was 1.5° (SD = 1.13). The mean lower limb length discrepancy was +0.05mm (SD = 5.1 mm) post-operatively. Conclusion. Digital templating is a accurate method of assessing femoral and acetabular component sizes. This allows surgeons to foresee potential problems and also recognize an intra-operative error when a large discrepancy exists between a trial component and the templated size

Introduction. To control implant alignments (anteversion and abduction angle of the acetabular cup and antetorsion of the femoral stem) within an appropriate angle range is essentially important in total hip arthroplasty to avoid implant impingement. A navigation system is necessary for accurate intraoperative evaluation of implant alignments but is too expensive and time-consuming to be commonly used. Therefore, a cheaper and easier tool for intraoperative evaluation of the alignments is desired in the clinical field. I presented an idea of marking ruler-like scales on a trial femoral head in the last ISTA Congress. The purpose of this study is to introduce an idea further improved in evaluating the combined implant alignment intraoperatively. Materials and Methods. We can evaluate the combined anteversion (sum of cup anteversion and stem antetorsion) and cup abduction angle by reading the scales at the most proximal point of inner edge of the liner when horizontal and vertical scales are marked on the femoral head appropriately and the hip joint is kept at the neutral position after implant settings and trial reduction. Whether the impingement occurred within the target ROM (Flx 130, IR40@Flx90, Ext 40, ER 40) was judged under specific conditions of the oscillation angle (139), neck-shaft angle of the stem (130), stem adduction angle (7), stem antetorsion (20 or 30), and cup anteversion and abduction angles. Cup anteversion and abduction angles were changed from 0 to 40 and 30 to 50 degrees in 1-degree increments, respectively. Impingement judgment was performed mathematically for each combination of implant alignment based on matrix transformations and trigonometric formulas. Results. Impingement-free combinations of implant alignments were identified using spreadsheet software. Points which indicated impingement-free when they matched with the most proximal point of the inner edge of the liner when the hip joint was kept neutral were plotted on the surface of the head on a 3-dimensional computer graphic software. Thus, the safe zone could be indicated visually on the trial head by a collection of these points. Discussion. We can easily judge whether the implant impingement occurs or not by using this trial head intraoperatively. However, there are several factors which make the judgment inaccurate. First, the safe zone varies according to the stem antetorsion. Second, the position at which the hip is kept intraoperatively is not necessarily neutral. Third, stem adduction angle varies according to the length of the femur. Conclusion. Safe zone mapping on the trial femoral head is low cost and easy method to be introduced in the clinical practice for the purpose of a rough judgment of implant impingement

Background. Supine positioning during direct anterior approach total hip arthroplasty (DAA THA) facilitates use of fluoroscopy, which has been shown to improve acetabular component positioning on plane radiograph. This study aims to compare 2- dimensional intraoperative radiographic measurements of acetabular component position with RadLink to postoperative 3- dimensional SterEOS measurements. Methods. Intraoperative fluoroscopy and RadLink (El Segundo, CA) were used to measure acetabular cup position intraoperatively in 48 patients undergoing DAA THA. Cup position was measured on 6-week postoperative standing EOS images using 3D SterEOS software and compared to RadLink findings using Student's t-test. Safe-zone outliers were identified. We evaluated for measurement difference of > +/− 5 degrees. Results. RadLink acetabular cup abduction measurement (mean 43.0°) was not significantly different than 3D SterEOS in the anatomic plane (mean 42.6°, p = 0.50) or in the functional plane (mean 42.7°, p = 0.61) (Fig. 1–2). RadLink acetabular cup anteversion measurement (mean 17.9°) was significantly different than 3D SterEOS in both the anatomic plane (mean 20.6°, p = 0.022) and the functional plane (mean 21.2°, p = 0.002) (Fig. 3–4). RadLink identified two cups outside of the safe-zone. However, SterEOS identified 12 (anatomic plane) and 10 (functional plane) outside of the safe-zone (Fig. 5–7). In the functional plane, 58% of anteversion and 92% of abduction RadLink measurements were within +/− 5° of 3D SterEOS. Conclusion. Intraoperative fluoroscopic RadLink acetabular anteversion measurements are significantly different than 3D SterEOS measurements, while abduction measurements are similar. Significantly more acetabular cups are placed outside of the safe- zone when evaluated with 3D SterEOS versus RadLink

Background. Between 1999 and August 2005, we performed Direct Lateral Approach (DLA) in lateral decubitus position as the main approach for primary total hip arthroplasty (THA). After August 2005, we introduced Direct Anterior Approach(DAA) in supine position. Intraoperative target orientation in primary THA was planned in 40–45°cup abduction, 10–20°cup anteversion, and 10–20° stem anteversion. Precice implant positioning has been considered to be very important for postoperative function and stability. The purpose of this study was to compare the DLA and DAA for implant positioning accuracy. Methods. From 1999 to July 2009, we performed 566 primary THAs(78 male, 488 female). The subjects were divided into two groups of 224 DLA and 342 DAA (72 in early stage and 270 in late stage) The difference of the mean age at surgery and preoperative diagnosis among the groups were not significant. We planned to set the cup anteversion at 20°in DAA early stage and 12.5°in late stage DAA due to the development of postoperative dislocation in several cases with early stage DAA. We measured the cup and stem alignment postoperatively using radiography and computed tomography, and measured the combined anteversion angle by Widmer. Statistical analysis was done using the Bartlett Statistical Test and F-test. The results were expressed as median and interquartile range, with an alpha level set at less than 0.05. Results. Cup abduction angle with DLA was 42.7±6.25 °(average±standard deviation), 42.1±4.1°with early stage DAA and 41.9±5.3°with late stage DAA. There was no significant difference between the approaches with average and standard deviation (SD) of cup abduction. The mean cup anteversion with DLA (17.3±10.0°) was significantly smaller than that with early stage DAA(26.6±8.1°) and late stage DAA(21.0±8.0°). SD of cup anteversion with DLA was significantly larger than that with both DAA groups. The mean stem anteversion was significantly smaller with DLA (18.9±14.3) and late stage DAA (16.7±11.1°) than that with early stage DAA (23.5±11.9°). SD of stem anteversion with DLA was significantly larger than that with both DAA groups. There were 9 hips of dislocation: 5 hips in DLA, 3 in early DAA and one in late DAA. SD of combined anteversion Value with DLA(30.5±13.7) was significantly larger than that with early DAA (40.3±12.2) and late DAA (32.7±11.1.∗∗∗∗∗. Conclusion. Significantly less SD for anteversion of stem and cup was demonstrated with DAA compared with DLA. Stable operative positioning with DAA could yield a more accurate and reliable implantation compared with DLA in lateral position. DAA in supine position was a superior approach for primary THA

As a generic technology, intentionally crosslinked polyethylene has improved the durability of total hip replacement. Regardless of the manufacturing method, the wear rates have been reduced on the order of 90% compared to historical materials, with a substantial reduction in the occurrence of osteolysis. Most of the data is with 28 and 32 mm bearings. Larger diameter bearings have been shown to reduce the occurrence of dislocation. However, there is clinical evidence that volumetric wear is increased with larger diameter crosslinked polyethylene bearings, and this may increase the occurrence of osteolysis. Further, modular liner fracture is more likely with larger diameter bearings (thinner liners), which is generally associated with increased cup abduction angle and/or increased anteversion. Contemporary polymers are better than their predecessors, but there is always opportunity for improvement

Background. Failed ingrowth and subsequent separation of revision acetabular components from the inferior hemi-pelvis constitutes a primary mode of failure in revision total hip arthroplasty (THA). Few studies have highlighted other techniques than multiple screws and an ischial flange or hook of cages to reinforce the ischiopubic fixation of the acetabular components, nor did any authors report the use of porous metal augments in the ischium and/or pubis to reinforce ischiopubic fixation of the acetabular cup. The aims of this study were to introduce the concept of extended ischiopubic fixation into the ischium and/or pubis during revision total hip arthroplasty [Fig. 2], and to determine the early clinical outcomes and the radiographic outcomes of hips revised with inferior extended fixation. Methods. Patients who underwent revision THA utilizing the surgical technique of extended ischiopubic fixation with porous metal augments secured in the ischium and/or pubis in a single institution from 2014 to 2016 were reviewed. 16 patients were included based on the criteria of minimum 24 months clinical and radiographic follow-up. No patients were lost to follow-up. The median duration of follow-up for the overall population was 37.43 months. The patients' clinical results were assessed using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index and Short form (SF)-12 score and satisfaction level based on a scale with five levels at each office visit. All inpatient and outpatient records were examined for complications, including infection, intraoperative fracture, dislocation, postoperative nerve palsy, hematoma, wound complication and/or any subsequent reoperation(s). The vertical and horizontal distances of the center of rotation to the anatomic femoral head and the inclination and anteversion angle of the cup were measured on the preoperative and postoperative radiographs. All the postoperative plain radiographs were reviewed to assess the stability of the components. Results. At the most recent follow-up, 11 (68.8%) patients rated their satisfaction level as “very satisfied” and 4 (25.0%) were “satisfied.” The median HHS improved significantly and the WOMAC global score decreased significantly at the latest follow-up (? 0.001). No intraoperative or postoperative complications were identified. All constructs were considered to have obtained bone ingrowth fixation. The median vertical distance between the latest postoperative center of rotation to the anatomic center of the femoral head improved from 14.7±10.05 mm preoperatively to 6.77±9.14 mm at final follow-up (p=0.002). The median horizontal distance between the latest postoperative center of rotation to the anatomic center of femoral head improved from 6.3±12.07 mm laterally preoperatively to 2.18±6.98 mm medially at the most recent follow-up (p=0.013) postoperatively. The median acetabular cup abduction angle improved from 55.04°±10.11° preoperatively to 44.43°± 5.73° at the most recent follow-up postoperatively (p=0.001). However, there was no difference in the median cup anteversion angles preoperatively (9.15°±5.36°) to postoperatively (9.66°±3.97°) (P=0.535). Conclusions. Early follow-up of patients reconstructed with the technique of extended ischiopubic fixation with porous metal augments demonstrated satisfactory clinical outcomes, restoration of the center of rotation and adequate biological fixation. For any figures or tables, please contact the authors directly

As a generic technology, intentionally cross-linked polyethylene has improved the durability of total hip replacement. Regardless of the manufacturing method, the wear rates have been reduced on the order of 90% compared to historical materials, with a substantial reduction in the occurrence of osteolysis. Most of the data is with 28mm and 32mm bearings. Larger diameter bearings have been shown to reduce the occurrence of dislocation. However, there is clinical evidence that volumetric wear is increased with larger diameter cross-linked polyethylene bearings, and this may increase the occurrence of osteolysis. Further, modular liner fracture is more likely with larger diameter bearings (thinner liners), which is generally associated with increased cup abduction angle and/or increased anteversion. Contemporary polymers are better than their predecessors, but there is always opportunity for improvement

The transgluteal approach (TG) offers a user-friendly alternative to the heavily promoted anterior approach (DA) to total hip arthroplasty (THA). Our purpose is to illustrate the advantages and details of the technique, illustrate the surgical anatomy that differentiates TG from the “traditional posterior” technique, and point out the surprising similarities to the DA. Unlike the traditional posterior THA, the TG preserves ITB, quadratus, and obturator externus. The conjoined tendon is released, providing direct access to the femur via the piriformis fossa. Direct acetabular access is facilitated either by using a portal through which reaming and cup impaction are performed or offset instrumentation. Intra-operative digital radiography was used in all cases. We present the clinical and radiographic outcome of 850 consecutive primary THA using the TG. At 2–6 years follow-up, dislocation rate was 0.3%, cup abduction 35–50 degrees in 97%, 92% used a cane within 5 days, 61% reported driving within the first post-operative week. No intra-operative trochanteric fractures, nerve injuries, or wound problems were observed. Three calcar fractures were wired. Hospital stay averaged 1.5 days, no patient received a blood transfusion if their pre-operative hematocrit was normal, and 88% of patients were discharged on acetaminophen only. The TG is a reliable and highly successful alternative to commonly used soft tissue sparing approaches in THA. It permits accelerated recovery while assuring optimal component orientation. The surgeon familiar with the traditional posterior approach can embark on a gradual learning curve that can minimise the complication rate as the surgeon learns the technique

INTRODUCTION. Despite our best efforts, orthopaedic surgeons do not always achieve desired results in acetabular cup positioning in total hip arthroplasty. New advancements in digital radiography and image analysis software allow contemporaneous assessment of cup position in real-time during the surgical procedure. The purpose of this study was to describe and validate a technique in obtaining a true AP Pelvis radiograph in the lateral decubitus position to accurately assess cup position intra-operatively (Figure 1). METHODS. 350 consecutive patients undergoing THA through a soft-tissue sparing posterior approach were prospectively enrolled. Standard pre-operative supine radiographs were taken in the office to serve as a reference for intra-operative pelvic orientation and templating. Intra-operative AP Pelvis radiographs were obtained with the patient in the lateral decubitus position to appropriately match the pre-operative radiograph. Adjustments were made to correct for pelvic rotation by rotating the operating room table forward or backward. Radiographic beam angle adjustments allowed the surgeon to match pre-operative and intra-operative pelvic tilt (Figure 2). Two independent observers measured cup abduction angle. RESULTS. 95% of cups were placed within 30–50 degrees of abduction, with a mean angle of 38 degrees (STD +/− 5). 100% of cups measured post-operatively were placed within 3 degrees of their intra-operative measurement. Mean anteversion was 27.5 degrees (STD +/− 3.5). Intra-operative radiographs were repeated in 88% of cases in order to match to the pre-operative radiographs. The cup was repositioned in 28% of cases based on intra-operative measurements. Impingement during range of motion testing occurred in 3% of cases despite acceptable measurements, necessitating cup reposition. The intercross correlation coefficient between the two observers was 0.92. There was one dislocation reported in the 2-year follow-up. Changes in the pelvic inlet and outlet orientation changed the abduction angle measurement in a predictable way. We developed a formula and 3D model to predict the abudction angle based on the pelvic tilt, where a more outlet view would increase the abduction angle measurement (Figure 3). DISCUSSION AND CONCLUSION. Advancements in digital radiography allow for real-time cup position assessment, creating the opportunity for the surgeon to make the appropriate changes and confirm precise placement during the procedure. For figures/tables, please contact authors directly.

Although total hip arthroplasty is highly successful for treatment of osteoarthrosis of hip joint, it is skill demanding surgery to perform and even more challenging in case of revision with bone defects. There are many options available for reconstruction of acetabular bony defects. Here, we evaluate the outcome of acetabular bony defect reconstructed with trabecular metal augments in short term. We performed, 22 revision total hip arthroplasties and 6 primary total hip arthroplasties (total 28 in 28 patients) using trabecular metal augments to reconstruct acetabular defect between 2011 to 2015. Out of these 28 patients, 18 were males and 10 were females. Mean age of these patients was 61.2 years (range: 46 years to 79 years). Pre-operative templating was done for all cases and need for trabecular metal augments was anticipated in all cases. All cases were classified according to Paprosky classification for acetabular bone defects. Out of 28 patients, 3 had type 2B, 1 had type 2C, 18 had type 3A and 6 had type 3B acetabular defects. Post operatively, all patients were followed at regular interval for their clinical and radiological outcome. An average follow up was 20.1 months (range: 6 months to 42.5 months). We assessed clinical outcome in the form of Herris hip score (HHS) and radiological outcomes in form of osteolysis in acetabular zones and osseointegration, according to the criteria of Moore. The average Harris hip score (HHS) was improved from 58.0 preoperatively to 87.2 postoperatively. The average degree of cup abduction at the final follow up was 44.29. The centre of rotation of the hip joint was corrected from average 38.90mm (range: 22.15mm to 66.35mm) above the inter-teardrop line preoperatively to average 23.85mm (range: 11.82mm to 37.69mm) above the inter-teardrop line postoperatively. Out of 28 patients, 18 patients had three or more signs of osseointegration, according to the criteria of Moore, at the time of final follow up. Rest of patients, had one or two signs of osseointegration (5 patients had one sign and 5 patients had two signs). We had no patient with migration or loosening of acetabular components. No patient has osteolysis of acetabulum in any zone. Trabecular metal augments provide good initial stability to acetabular cup as well as helpful to bring down the centre of rotation of the hip joint within limit of 35mm above the inter-teardrop line. They also facilitate osseointegration. Our study showed that the results of the trabecular metal augments in reconstruction of acetabular bony defects were successful even in short term. However, long term study is required for better evaluation

INTRODUCTION. Femoral stem impingement can damage an acetabular liner, create polyethylene wear, and potentially lead to dislocation. To avoid component-to-component impingement, many surgeons aim to align acetabular cups based on the “Safe Zone” proposed by Lewinnek. However, a recent study indicates that the historical target values for cup inclination and anteversion defined by Lewinnek et al. may be useful but should not be considered a safe zone. The purpose of this study was to determine the effect of altering femoral head size on hip range-of-motion (ROM) to impingement. METHODS. Ten healthy subjects were instrumented and asked to perform six motions commonly associated with hip dislocation, including picking up an object, squatting, and low-chair rising. Femur-to-pelvis relative motions were recorded throughout for flexion/extension, abduction/adduction, and internal/external rotation. A previously reported custom, validated hip ROM three-dimensional simulator was utilized. The user imports implant models, and sets parameters for pelvic tilt, stem version, and specific motions as defined by the subjects. Acetabular cup orientations for abduction and anteversion combinations were chosen. The software was then used to compute minimum clearances or impingement between the components for any hip position. Graphs for acetabular cup abduction vs. anteversion were generated using a tapered wedge stem with a 132º neck angle, a stem version of 15°, and a pelvic tilt of 0°. The only variable changed was femoral head size. Head sizes reviewed were 32mm, 36mm, and a Dual-Mobility liner with an effective head size of 42mm. All femoral head sizes can be used with a 50mm acetabular cup. RESULTS. We found that the “Safe Zone” varies considerably depending on the size of the femoral head used for all subjects. A typical plot illustrating the ROM to impingement is presented in Figures 1a-1c. The area to the left of each curve represents an impingement zone for that motion, and to the right, a non-impingement zone. In all cases the non-impingement area is smaller than the Lewinnek safe zone. Motions like picking up an object and squatting had the greatest influence on impingement. CONCLUSIONS. The true acetabular target for impingement-avoidance motion is much smaller than previously believed and identifies the need to take into account the size of the femoral head to be used. This may explain why approximately 70% of dislocations have been reported to be found even when cups were placed within the Lewinnek safe zone. Certain activities, such as picking up an object and squatting reduce the size of the safe zone. This study supports the need for better patient planning and intraoperative execution for placement of the acetabular component