Aims

In computer simulations, the shape of the range of motion (ROM) of a stem with a cylindrical neck design will be a perfect cone. However, many modern stems have rectangular/oval-shaped necks. We hypothesized that the rectangular/oval stem neck will affect the shape of the ROM and the prosthetic impingement.

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. 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

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

The classical longitudinal incision used for the direct anterior approach (DAA) does not follow the relaxation tension lines of the skin and can lead to impaired wound healing and poor scar cosmesis. The purpose of this study was to determine patient functional and radiographic outcomes of a modified skin crease “bikini” incision used for the DAA in THR. 964 patients (51% female; 59% longitudinal, 41% bikini) completed 2 to 4 years after surgery a follow-up questionnaire including the Oxford Hip Score (OHS), the University of North Carolina 4P scar scale (UNC4P), and two items for assessing aesthetic appearance and symptoms of numbness. Implant position, rates of radiographic heterotopic ossification and required revision were assessed. UNC4P total (p<0.001) and OHS (p=0.013) scores were better in the bikini compared the longitudinal group. The proportion of aesthetically very satisfied patients was higher (p<0.001) in the bikini group. The proportion of patients reporting numbness in the scar was higher (p<0.001) in the longitudinal (14.5% versus 7.5%, respectively). Radiographic cup abduction angles, stem position and ectopic ossification rates did not differ between the groups. No differences in the revision rates of both groups being 2.1% in the longitudinal and 1.5% in the Bikini group. Although differences were not huge, Bikini incision resulted in better patient-related outcomes and satisfaction related to the scar. Our study showed that a short oblique “bikini” skin crease incision for the DAA can be performed safely without compromising implant positioning or increasing symptoms suggesting lateral femoral cutaneous nerve dysesthesia. As it is less extensile it should be used after having gained significant experience with the classic longitudinal incision

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. 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.

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

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

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

Management of pseudotumours associated with MoM THA can be difficult and complications are frequent. The functional outcome of patients after revision surgery may be suboptimal. The objective of this study was to assess our experience with revisions of failed MoM THA due to pseudotumours. 78 hips were diagnosed with pseudotumours in 70 patients following metal-on-metal hip replacements. Of these, 68 MoM THA were revised in 62 patients. Pre operative symptoms, radiographic analysis, metal ion levels, MRI results, intra-operative findings, WOMAC scores, the satisfaction level and the complication rate were recorded. Five patients had a resurfacing arthroplasty as their primary implants while the remaining 63 hips in 57 patients had MoM THA of different brands. The average time between the primary and revision surgery was 69 months (range 15–120). The average age at revision was 59 years (43–87). The mean follow-up was 24 months (range 2–73). 36 patients had minimal one year follow-up. Most lesions consisted of cystic changes and solid lesions were observed in 19 patients. In 57 hips, the pseudotumours were located posteriorly or postero-laterally around the greater trochanter. Intra operatively, muscle necrosis was observed in 15(22%) patients. Most THA cases demonstrated wear and corrosion at the head neck junction of the femoral implants. Thirty-five patients (44.9%) had greater than 50 degrees of cup abduction, including 10 patients (12.8%) with an abduction angle greater than 60 degrees. The average pre operative and postoperative Co ion levels were 27.46 ug/L (range 0.36–145.6) and 2.46 (range 0.4–12.48), respectively. Post revision, a total of 10 hips (14.7%) sustained a dislocation, with seven (10.3%) of them experiencing recurrent dislocations. In 8/10 hips, the femoral head size was 36mm or greater. Revision for dislocation occurred in seven(10.3%) patients. Three(4.4%) deep and one(1.47%) superficial infections occurred and deep infections were re-operated. One(1.47%) fracture of the greater trochanter and one (1.47%) psoas tendinitis did not need revision. Therefore, a total of 10 patients (14.7%) were reoperated. 6 revisions for instability were performed in the first 34 patients, while 1 were done in the last 34 patients. At one year post revision surgery, the mean WOMAC score was 19.68 (range 0–48). In comparison, the mean WOMAC score of the same patients one year after their primary surgery was 8.1 (0–63). Patient satisfaction level of patients one year post revision surgery was 7.61 (range 5–10) compared to 4.15 (range 0–7) pre-revision one. The complication rate after revision of pseudotumours is high. Most re revisions occurred secondary to instability despite the use of larger femoral heads. The functional outcome at one year post revision seems to be lower than that seen after primary THA but similar to other revisions in the literature. Experience in the management of these patients may reduce the complication rate

Introduction. Acetabular fixation is one of the major factors affecting long-term longevity and durability of total hip arthroplasty (THA). Limited data exist regarding mid-term performance of modern non-cemented rim-fit cups with HA coating. The aim of this study was to assess the minimum 5 year clinical and radiographic performance of PSL cups. Therefore we retrospectively analyzed results of this component in patients that had adequate followup from a prospective institutional database. Materials and Methods. A retrospective analysis of a prospective database was performed to identify patients that underwent non-cemented THA between 2003 and 2007. 223 primary THA (210 patients) were performed by single surgeon via posterolaeral approach using a grit-blasted, HA coated rim-fit design and highly cross-linked polyethylene and were followed with minimum 5 years. The mean age was 62.5 years ± 10.8. The majority of the stems were non-cemented (87%) and the majority of the femoral heads were metal (75%), 22- or 28-mm diameter. 72% of the cups were solid and 28% were multi-hole. Clinical assessment included the Hospital for Special Surgery (HSS) hip score [18] at final follow-up, and Kaplan-Meier survivorship. All patients received pre- and post-operative anteroposterior (AP) weight bearing pelvis radiograph as well as a false profile view of the hip. Cup positioning was analyzed using the EBRA software (Einzel-Bild-Roentgen-Analysis; University of Innsbruck, Innsbruck, Austria) for functional abduction angle, anteversion, and cup migration. Osseointegration was assessed on the DeLee and Charnley's zones on both AP and false profile views. Osseointegration was defined based on the following characteristics:. presence of Stress Induced Reactive Cancellous Bone (SIRCaB), where new bone condensation (not apparent on preoperative radiographs) was present at the load bearing area of the cup (Figure 1). presence of radial trabeculae that project in continuum from the shell into the pelvis, suggesting integration of the trabecular bone onto the metal surface at the load bearing area, (Figure 2). absence of radiolucency. Radiolucency was determined by radiolucent lines that were at least 1–2 mm wide and were seen in sequential radiographs, not apparent on the initial postoperative radiograph. Linear and rotational migration was defined as > 3 mm or > 5°change in the cup position, respectively, as measured on serial radiographs. Any changes in cup position or presence of circumferential radiolucencies were considered as loosening. Results. The average duration of follow-up was 6.2 ± 1.1 years (5 – 10 years). The mean HSS score was 34.8 ± 5.0 (19 – 40). There was an overall revision rate of 3.6% (8 cases) with Kaplan-Meier survivorship for all causes of 96.4% (95% CI: 0.92 – 0.98). There was one periprosthetic femur fracture. One stem was revised for fracture at the truniun/neck junction. There were 2 dislocation (0.9%); in one hip the cup was revised and the other was treated with a constrained liner. In 3 THAs (1.3%), stems were revised for loosening/failure of osseointegration (2 non-cemented stems, 0.9%) and osteolysis (one cemented stem, 0.4%). One THA (0.45%) underwent two stage revision for treatment of periprosthetic infection. There were no revisions for cup loosening or osteolysis or ceramic head fractures. The Kaplan-Meier survivorship for cup revision for any failure was 99% (95% CI: 0.96 – 0.99) and for mechanical failure was 100% (95% CI: 0.97 – 1). In radiographic analysis, the average functional cup abduction angle and anteversion were 41.7° ± 5.2 (range, 30 – 52) and 16.8° ± 6.1 (range, 4 – 30). 96% of the cups were within the safezone of Lewinnek. There were no migration or change in cup position in any cases. Presence of SIRCaB and radial trabeculae in all 3 zones were seen in 47% and 93% of cups, respectively; both were most prevalent in Zone 1. The absence of radiolucent line was observed in 96% of cases. In 161 THAs (72%), no screws were used due to excellent initial stability. Detail radiographic osseointegration assessment in the non-screw fixation group (as compared to the THAs with screw fixation) showed significantly higher incidence of SIRCaB (49% versus 39.7%, p=0.05) and radial trabeculae (97.5% versus 94.7%, p=0.001). There was also significantly less radiolucent lines in the non-screw fixation group (p=0.001). Discussion. No evidence of radiographic failure to osseointegrate was found in this study as evidenced by absence of radiolucency, evidence of radial trabeculae, and a reactive condensation of new bone to the well-fixed acetabular shell. Interestingly, we found that the solid designs had significantly better osseointegration when compared to multi-hole designs. In this single surgeon series with mid-term follow-up reiterates that the HA-coated hemispherical rim-fit acetabular component has excellent radiographic osseointegration, clinical outcomes and high survivorship for mechanical failures

Introduction. This study reports outcomes of 35 revisions of a recalled metal-on-metal (MOM) monoblock prosthesis performed by a single surgeon. Methods. We prospectively collected data on all patients who underwent revision of a recalled metal-on-metal monoblock prosthesis between 2010 and 2015. Average follow-up was 2.5 years post-revision and 6.9 years post-primary procedure. We evaluated the cohort for age, BMI, gender, existence of medical comorbidities, and post-op complications. We compared pre and post-revision cup abduction angles, anteversion angles, combined angles, cup sizes, and Harris Hip Scores. Cobalt and chromium levels were followed throughout the study period for each patient. Results. Thirty-one patients underwent 35 revisions surgeries for pain, high metal ions, infection, aseptic loosening, failure of ingrowth, leg length discrepancy and/or pseudotumor. Two of these revisions were subsequently re-revised – one for continued pain and one for failure involving multiple dislocations, breakage of screws, and acetabular fracture. The survival rate for our revisions to date is 94.3%. Female patients comprised a majority of revisions (54%) despite comprising a minority (28%) of primary hip replacements using the studied prosthesis. Revised patients were an average of 51.8 years of age with a BMI of 31.07. Demographics are included on Table 1. There were five post-operative complications, including 2 infections, 2 dislocations, and one DVT. Cups were revised from a mean abduction angle of 47.5° in primary hips to 42.3° in revisions. Cups were revised from a mean of 53.4 to 57.8. Cobalt and chromium levels were followed in all patients and showed significant decrease after revision (Graph 1). Cobalt levels decreased from an average of 33.7 to 13.1 ng/mL while Chromium levels decreased from an average of 12.4 to 9.2 ng/mL. Harris Hip Scores increased significantly after revision (45.8 to 72.1). Conclusion. This study presents 35 revisions of a recalled monoblock hip prosthesis performed by a single surgeon at our institution from 2010 to 2015. To our knowledge, this is the largest single-surgeon study reported in the literature. Acetabular cups were revised to a lower average abduction angle. Patients have had significant improvements in Harris Hip Scores and significant decreases in Cobalt and Chromium levels after revisions. Our revision survival rate to date is 94.3% at an average of 2.5 years (range 2 weeks – 4.3 years). To view tables/figures, please contact authors directly

Prosthetic Hip dislocations remain one of the most common major complications after total hip arthroplasty procedures, which has led to much debate and refinement geared to the optimization of implant and bearing options, surgical approaches, and technique. The implementation of larger femoral heads has afforded patients a larger excursion distance and primary arc range motion before impingement, leading to lowered risk of hip dislocation. However, studies suggest that while the above remains true, the use of larger heads may contribute to increased volumetric wear, trunnion related corrosion, and an overall higher prevalence of loosening, pain, and patient dissatisfaction, which may require revision hip arthroplasty. More novel designs such as the dual mobility hip have been introduced into the United States to optimize stability and range of motion, while possibly lowering the frictional torque and modes of failure associated with larger fixed bearing articulations. Therefore, the aim of this study is to compare the effect of bearing design and anatomic angles on frictional torque using a clinically relevant model8. Two bearing designs at various anatomical angles were used; a fixed and a mobile acetabular component at anatomical angles of 0°,20°,35°,50°, and 65°. The fixed design consisted of a 28/56mm inner diameter/outer diameter acetabular hip insert that articulated against a 28mm CoCr femoral head (n=6). The mobile design consisted of a 28mm CoCr femoral head into a 28/56mm inner diameter/outer diameter polyethylene insert that articulates against a 48mm metal shell (n=6). The study was conducted dynamically following a physiologically relevant frictional model8. A statistical difference was found only between the anatomical angles comparison of 0vs65 degrees in the mobile bearing design. In the fixed bearing design, a statistical difference was found between the anatomical angles comparison of 20vs35 degrees, 20vs50 degrees, and 35vs65 degrees. No anatomical angle effect on frictional torque between each respective angle or bearing design was identified. Frictional torque was found to decrease as a function of anatomical angle for the fixed bearing design (R2=0.7347), while no difference on frictional torque as a function of anatomical angle was identified for the mobile bearing design. (R2=0.0095). These results indicate that frictional torque for a 28mm femoral head is not affected by either anatomical angle or bearing design. This data suggests that mobile design, while similar to the 28mm fixed bearing, may provide lower frictional torque when compared to larger fixed bearings >or= 32mm8. Previous work by some of the authors [8] show that frictional torque increases as a function of femoral head size. Therefore, this option may afford surgeons the ability to achieve optimal hip range of motion and stability, while avoiding the reported complications associated with using larger fixed bearing heads8. It is important to understand that frictional behavior in hip bearings may be highly sensitive to many factors such as bearing clearance, polyethylene thickness/stiffness, polyethylene thickness/design, and host related factors, which may outweigh the effect of bearing design or cup abduction angle. These factors were not considered in this study

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

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. Total hip arthroplasty (THR) with non-cemented or hybrid fixation remains one of the most successful procedures performed today. The aim of this study was to assess the safety and efficacy of a hydroxyapatite (HA) coated, hemispherical cup. Material and Methods. Between 2003 and 2007, 223 THAs (210 patients) with peripheral self-locking (PSL) cup and highly cross-linked polyethylene (Crossfire, Stryker, Mahwah, NJ) with minimum 5 years clinical and radiographic follow-up (5–9 years) were analyzed. The mean age was 62.5 years ± 10.8 (range, 32.7 – 86.3) at the time of surgery and the predominant preoperative diagnoses was osteoarthritis (97.8%). 72% were solid cups without screw augmentation and 28% were multi-hole with screw. Clinical analysis included Hospital for Special Surgery (HSS) hip scores at latest follow-up. Detail radiographic analysis was carried out on anteroposterior and false profile views for evidence of osseointegration in all Charnley's zones. Osseointegration was assessed based on presence of Stress Induced Reactive Cancellous Bone (SIRCaB) with trabecular bone hypertrophy 5–15mm extending from the cup, and absence of radiolucency or demarcation. EBRA software was used to assess cup positioning. Results. At final follow up, clinical result were excellent with average HSS score of 34.8. 4% underwent revision for following reasons: dislocation (1.34%), loose stem (0.89%), stem fracture (0.89%), pain/bursitis (0.45%), and infection (0.45%). There were no revisions for failures of fixation. In radiographic analysis, the average functional cup abduction angle and functional anteversion were 41.7° ± 5.2 (range, 30 – 52) and 16.8° ± 6.1 (range, 4 – 30). 96% of the cups were within the safezone of Lewinnek. There was no progressive radiolucency, migration or change in the cup position at final follow-up. The average overall SIRCaB and radial trabeculae in all 3 zones were 47% and 93%, respectively; both were most prevalent in Zone 1. Conclusion. The hemispherical, peripheral press-fit, HA-coated PSL cup has excellent safety and efficacy, appropriate radiographic osseointegration with no mechanical failures at 5 – 9 years. PSL cup has 1 mm increase in the radius at the periphery of the shell to allow for an enhanced initial press fit. Based on our results, supplementary screw with this cup may not lead to better fixation

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

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

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