A method to calculate the acetabular cup anteversion after total hip replacement based on 3D coordinate system

The acetabular cup positioning is one of the most crucial steps affecting stability and wear rates in total hip arthroplasty. Different methods have been described for determining the anteversion of the acetabular cup in the literature. But there is still not a widely accepted method to assess the acetabular anteversion radiography. The aim of this study is to measure the acetabular anteversion angle on a single pelvis AP radiography with our method which was proven with an experimental study before. A total of 15 patients (8 males, 7 females) who underwent total hip arthroplasty and have had a pelvis computed tomography scans in our outpatient clinic were evaluated retrospectively. The anteversion angle was calculated in all of pelvis CT scans. For radiological measurement, the formula defined by the authors in an experimental model previously was used. Statistically significant difference was not determined between radiographic and CT-based measurements (p = 0.207; p > 0.05). A statistically significant agreement was observed at a level of 98.8% between radiographic and CT-based measurements (ICC = 0.988; 95% CI 0.966-0.996; p < 0.01). Assessment of the acetabular cup anteversion is very important to predict the possible complications after total hip arthroplasty. Although many methods have been defined for this purpose, each of these has advantages and disadvantages. In particular, with computed tomography method, the patient is exposed to excessive radiation, whereas we think that our method is a preferred method due to features not requiring additional equipment, low radiation exposure, being simple, cost-effectiveness, easily applicable and almost 100% accurate.

The purpose of this study is to define the normal range of acetabular abduction and anteversion in relation to pelvic anatomy as depicted on conventional CT scan. We retrospectively reviewed 100 pelvic CT scans performed on patients presenting for evaluation of non-orthopaedic pathology. The study group consisted of 58 women and 42 men, aged between 18 and 88 years. Standard imaging protocol included an anteroposterior (AP) topogram with contiguous 5-mm thick axial images from the superior margin of the iliac crest to the lesser trochanter of the femur. The acetabular abduction was measured from the AP topogram by obtaining the angle between a line drawn from the acetabular teardrop to the lateral acetabular margin and a horizontal line between the ischial tuberosities. Acetabular anteversion was measured on axial images at the level of the mid-femoral head. We found the mean acetabular abduction to be 39 degrees (standard deviation 4 degrees, range 27 to 51 degrees) and the mean acetabular anteversion to be 23 degrees (standard deviation 5 degrees, range 12 to 39 degrees). Data suggests that acetabular anteversion may average 2.7 degrees lower in males than females and increase slightly with age, while abduction may tend to decrease with age. Ninety percent of patients had acetabular abduction between 31 and 46 degrees; the 90% central range for acetabular anteversion was estimated to be from 14 to 31 degrees. CT scanning is useful in accurately defining the normal range of acetabular abduction and antiversion. Knowledge of this normal anatomy will allow accurate assessment of acetabular component position as delineated on conventional CT scanning.

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AimsDebate continues as to the optimal orientation of the acetabular component in total hip arthroplasty (THA) and how to reliably achieve this. The primary objective of this study was to compare functional CT-based planning and patient-specific instruments with conventional THA using 2D templating.MethodsA pragmatic single-center, patient-assessor blinded, randomized control trial of patients undergoing THA was performed. 54 patients (aged 18–70) were recruited to either Corin Optimized Positioning System (OPS) or conventional THA. All patients received a cementless acetabular component. All patients underwent pre- and postoperative CT scans, and four functional X-rays. Patients in the OPS group had a 3D surgical plan and bespoke guides made. Patients in the conventional group had a surgical plan based on 2D templating X-rays. The primary outcome measure was the mean error in acetabular anteversion as determined by postoperative CT scan.ResultsThere was no statistically significant difference in the mean error in angle of acetabular anteversion when comparing OPS and conventional THA. In the OPS group, the achieved acetabular anteversion was within 10° of the planned anteversion in 96% of cases, compared with only 76% in the conventional group. The clinical outcomes were comparable between the groups.ConclusionLarge errors in acetabular orientation appear to be reduced when CT-based planning and patient-specific instruments are used compared to the standard technique but no significant differences were seen in the mean error.

To compare the early effectiveness between by anterior approach via Bikini incision and by OCM approach in the primary total hip arthroplasty (THA). Between June 2015 and March 2016, 60 patients with ischemic necrosis of the femoral head who accorded with the inclusion criteria were chosen in the study, who were divided into 2 groups according to different surgical approaches. THA was performed on 30 patients by anterior approach via Bikini incision (group A), and on 30 patients by OCM approach (group B). There was no significant difference in age, gender, body mass index, side of affected hip, Steinberg stage of ischemic necrosis of femoral head, preoperative hemoglobin, preoperative Harris score, and preoperative visual analogue scale (VAS) between 2 groups ( P>0.05). The operation time, length of incision, intraoperative blood loss, transfusion rate, starting time of straight leg raising exercise, starting time of active abduction of hip, hospitalization time, the incidence of limb length discrepancy, postoperative Harris score and VAS score were recorded and compared between 2 groups. Anteroposterior pelvic X-ray films were taken to measure acetabular abduction and acetabular anteversion. Primary healing of incision was obtained in all patients of 2 groups, and there was no significant difference in complication between 2 groups ( χ2=0.144， P=0.704). All the patients of 2 groups were followed up 3 to 12 months, averaged 6 months. There was no significant difference in operation time, length of incision, intraoperative blood loss, transfusion rate, hospitalization time, and starting time of straight leg raising exercise between 2 groups ( P>0.05). Group A was significantly shorter than group B in starting time of active abduction of hip ( t=-4.591, P=0.000), and was significantly lower than group B in the incidence of limb length discrepancy ( χ2=5.455, P=0.020). After operation, neither Harris score at 2 weeks, 6 weeks, 3 months, and 6 months nor VSA score at 24 hours and 6 weeks showed significant difference between 2 groups ( P>0.05). The anteroposterior pelvic X-ray films showed that all the prostheses were in good position, and there was no femoral prosthesis subsidence, acetabular cup displacement or dislocation. No significant difference was found in acetabular abduction and acetabular anteversion at 2 days after operation between 2 groups ( t=0.887, P=0.379; t=0.652, P=0.517). Both of two approaches in THA can avoid muscle damage and achieve favorable short-term effectiveness. But, anterior approach via Bikini incision is superior to OCM approach in starting time of active abduction of hip and the incidence of limb length discrepancy.

To evaluate whether acetabular orientation (abduction and anteversion) can be restored by lumbar pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis. A total of 33 consecutive AS patients with thoracolumbar kyphosis undergoing one-level lumbar PSO were retrospectively reviewed. Radiographical measurements included sagittal vertical axis, global kyphosis, thoracic kyphosis, local kyphosis, lumbar lordosis, pelvic incidence, sacral slope, and pelvic tilt. Acetabular abduction and anteversion were measured on CT scans of the pelvis before and after lumbar PSO. The preoperative and postoperative parameters were compared by the paired samples t test. Pearson's correlation analysis was conducted to determine the correlations between the changes in acetabular abduction and anteversion and the changes in sagittal spinopelvic parameters. After lumbar PSO, sagittal vertical axis, global kyphosis, and pelvic tilt were corrected from 15.7±6.7cm, 66.8°±17.5°, and 38.6°±9.0° to 2.9±4.9cm, 21.3°±8.2°, and 23.2°±8.2°, respectively (p<0.001). Of note, acetabular abduction and anteversion decreased from 59.6°±4.6° to 31.4°±6.5° before surgery to 51.4°±6.5° and 20.2°±4.4° after surgery, respectively (p<0.001). Moreover, the changes in acetabular abduction and anteversion were observed significantly correlated with the change in pelvic tilt (r=0.527, p=0.002; r=0.586, p<0.001). Abnormal acetabular abduction and anteversion could be corrected by lumbar PSO in AS patients with thoracolumbar kyphosis. Consequently, a relatively normal acetabular orientation could be achieved after lumbar PSO, which might decrease the potential risk of dislocation in AS patients with spine and hip deformities requiring subsequent THR surgery.

Advances in technology, implant design, and surgical technique have lowered the dislocation rate in primary total hip arthroplasty (THA). Despite these advances, there remain a large number of instability episodes without a known etiology. Recent research suggests that the pelvic and lumbar spine interrelationship may be the explanation in prosthetic dislocations without a known cause. In this review, we describe the biomechanics, measurements, diagnoses, classification, management, and outcomes of total hip and revision total hip instability as it relates to spinopelvic alignment. As a person goes from standing to sitting, lumbar lordosis decreases, and the sacrum and entire pelvis tilts posteriorly with sacrum and coccyx rotating posterior-inferiorly, resulting in increased acetabular cup anteversion to accommodate femoral flexion. A fused spine and associated fixed acetabulum can result in abnormal pelvic femoral motion, impingement, and dislocation. Classifying the spinopelvic mechanics by sacral motion based on sitting and standing lateral radiographs provides an understanding of how the acetabulum behaves in space. This information helps appropriate cup positioning, reducing the risk of femoral side impingement and subsequent dislocation. Surgical techniques to consider in the spinopelvic at-risk patient are positioning considerations in acetabular cup inclination and anteversion, high offset femoral stems, high offset acetabular liners, dual mobility articulations, and removal of impinging structures. Future research is needed to define the safest order of operation in concomitant hip and spine pathology, the effects on pelvic femoral biomechanics in spine surgery, and whether preoperative and intraoperative management strategies have a long-term beneficial effect on the dislocation rate.

Objective To compare the early clinical effect of posterolateral approach(PLA) and direct anterior approach(DAA) for total hip arthroplasty. Methods Retrospective cohort study was conducted. A total of 153 patients, including 64 males and 89 females, aged between 21 and 81 years old, who were treated with total hip replacement in the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine from April 2017 to June 2018. They were divided into the DAA group (79 cases) and the PLA group (74 cases) according to different surgical approaches. The operative time, incision length, visual analog score(VAS), Harris score, postoperative hospitalization time, independent walking time without walker and complications rate were compared and analyzed between the two groups. On the first postoperative day, the pelvic anterior radiograph was taken, and the PACS image processing system was used to measure the prosthetic angle . Then the position of the femoral prosthesis was determined according to the Nakata method ( the femoral false body curl over 3°- 3° for fixed prosthesis was centricity fixed). and the acetabular abduction angle and anteversion angle were measured according to the Pradhan method ( the acetabulum abduction angle of 30°-50°, the anteversion angle of 5°- 25°, which was the safe range of acetabular prostheses). Results Compared with the PLA group, the DAA group had longer operative time [(68.61±7.15)min vs (63.45±8.82)min], shorter incision length[(10.47±0.88)cm vs (12.06±0.91)cm], less intraoperative blood loss [(131.40±42.83)mL vs (155.70±48.09)mL], and shorter postoperative hospital stay[(3.94±0.92)d vs (4.79±0.95)d]. The walking time away from the walker was shorter[(3.91±1.09)d vs (6.34±1.35)d], and the postoperative VAS was lower at 1st and 3rd day after surgery(4.05±0.70 vs 4.38±0.75, 2.47±0.80 vs 2.82±0.88). The Harris scores were higher in the first and third month after operation (82.46±3.82 and 77.59±4.78, 89.11±3.61 and 85.82±3.18), and the differences were statistically significant (all P values 0.05). There was no significant difference in the incidence of complications between the two groups (P>0.05). Conclusions Compared with the PLA, the DAA with lateral decubitus is a safe and effective minimally invasive approach with less trauma, less postoperative pain and faster recovery . Key words: Arthroplasty, replacement, hip; Direct anterior approach; Posterolateral approach; Rehabilitation

Instability after total hip arthroplasty: Analysis of combined anteversion and patient-related clinical parameters.

To evaluate the 3D deformity of the acetabula and lower limbs in subjects with adolescent idiopathic scoliosis (AIS) and their relationship with spino-pelvic alignment. Two hundred and seventy-four subjects with AIS (frontal Cobb: 33.5° ± 18° [10°-110°]) and 84 controls were enrolled. All subjects underwent full-body biplanar X-rays with subsequent 3D reconstructions. Classic spino-pelvic and lower limb parameters were collected as well as acetabular parameters: acetabular orientation in the 3 planes (tilt, anteversion and abduction), center-edge angle (CEA) and anterior and posterior sector angles. Subjects with AIS were represented by both lower limb sides and classified by elevated (ES) or lowered (LS), depending on the frontal pelvic obliquity. Parameters were then compared between groups. Determinants of acetabular and lower limb alterations were investigated among spino-pelvic parameters. Acetabular abduction was higher on the ES in AIS (59.2° ± 6°) when compared to both LS (55.6° ± 6°) and controls (57.5° ± 3.9°, p < 0.001). CEA and acetabular anteversion were higher on the LS in AIS (32° ± 6.1°, 20.5° ± 5.7°) when compared to both ES (28.7° ± 5.1°, 19.8° ± 5.1°) and controls (29.8° ± 4.8°, 19.1° ± 4°, respectively, p < 0.001). Anterior sector angle was lower on both ES and LS in AIS when compared to controls. CEA, acetabular abduction and acetabular anteversion were found to be mostly determined (adjusted R2: 0.08-0.32) by pelvic tilt and less by frontal pelvic obliquity, frontal Cobb and T1T12. Subjects with AIS had a more abducted acetabulum at the lowered side, more anteverted acetabulum and a lack of anterior coverage of both acetabula. These alterations were strongly related to pelvic tilt.

Various methods have been described for measuring acetabular component anteversion. However, accurate measurement of anteversion is difficult. We herein propose a new method using cross-table lateral (CL) radiography performed with the contralateral hip flexed to 45° (45° flexed CL radiography). The main purpose of this study was to evaluate the reliability and validity of this new method. The study group included 93 patients who underwent total hip arthroplasty (THA). All hips were evaluated with computed tomography (CT) and both standard and 45° flexed CL radiographs to measure acetabular component anteversion the week after THA. The intraobserver and interobserver reliability of each measurement was assessed. Plain radiography measurements were compared with reference CT measurements to evaluate their validity. All measurements had excellent intraobserver and interobserver reliability, and plain radiography measurements correlated well with CT measurements. The mean measurements were 21.9° (3°-39°) with CT, 24.9° (7°-47°; p<0.001) with standard CL radiographs, and 22.5° (7°-43°; p = 0.112) with 45° flexed CL radiographs. The anteversion values measured with our new method were closer to the CT values used as a reference standard than those with standard CL radiographs. Our new method appears to be reliable and valid for measuring acetabular component anteversion.

IntroductionDislocation remains a major complication in total hip arthroplasty (THA), in which femoral component orientation is considered a key parameter. New imaging modalities and definitions on femoral component orientation have been introduced, describing orientation in different planes. This study aims to systematically review the relevance of the different orientation parameters on implant stability.MethodsA systematic review was performed according to the PRISMA guidelines to identify articles in the PubMed and EMBASE databases that study the relation between any femoral component orientation parameters and implant stability in primary THA.ResultsAfter screening for inclusion and exclusion criteria and quality assessment, nine articles were included. Definitions to describe the femoral component orientation and methodologies to assess its relevance for implant stability differed greatly, with lack of consensus. Seven retrospective case–control studies reported on the relevance of the transversal plane orientation: Low femoral- or low combined femoral and acetabular anteversion was statistical significantly related with more posterior dislocations, and high femoral- or combined femoral and acetabular anteversion with anterior dislocations in two studies. There were insufficient data on sagittal and coronal component orientation in relation to implant stability.ConclusionBecause of incomparable definitions, limited quality and heterogeneity in methodology of the included studies, there is only weak evidence that the degree of transverse component version is related with implant stability in primary THA. Recommendations about the optimal orientation of the femoral component in all three anatomical planes cannot be provided. Future studies should uniformly define the three-dimensional orientation of the femoral component and systematically describe implant stability.

Accurate and reproducible acetabular component positioning is among the most important technical factors affecting outcomes of total hip arthroplasty. Although several studies have investigated the influence of pelvic tilt and obliquity on functional acetabular anteversion, the effect of pelvic axial rotation has not yet been established. We analyzed a generic simulated pelvis created using preoperative full-body standing and sitting radiographs. A virtual acetabulum was placed in 144 different scenarios of acetabular anteversion and abduction angles. In each scenario, the effects of pelvic tilt and pelvic axial rotation on different combinations of acetabular orientations were assessed. The change in acetabular anteversion was 0.75° for each 1° of pelvic tilt and was most linear in abduction angles of 40°±45°. The change in acetabular anteversion was 0.8° for each 1° of pelvic axial rotation. Surgeons may consider adjusting acetabular anteversion in fixed axial pelvic deformities when the degree of deformity affects functional acetabular positioning, assessed from preoperative standing and sitting weight-bearing radiographs. [Orthopedics. 2023;46(1):e27-e30.].

PurposeThe purposes of the present research were to assess the accuracy and usability of the inertial navigation system (INS).Materials and MethodsThe accuracy of the device navigation subsystem was assessed using benchtop testing. The usability was assessed through simulated use with surgeons. These results were compared to recent cadaveric results for the same system.ResultsThe navigation subsystem had an overall mean absolute error of 1.21° and a maximum absolute error across all devices of 4.79°. The device was found to be usable and to add an estimated 7 minutes to surgery time.ConclusionThe INS uses a novel approach to provide the surgeon with accurate and fast acetabular cup inclination and anteversion angles during THA.

BackgroundAccurate acetabular cup orientation is associated with decreased revision rates and improved outcomes of primary total hip arthroplasty. This study assesses surgeon’s ability to estimate both the acetabular component inclination and anteversion angles via intraoperative fluoroscopy (IF) images.MethodsWe surveyed orthopedic surgeons to estimate acetabular component inclination and anteversion based on 20 IF images of total hip arthroplasty through a direct anterior approach. Postoperative computed-tomography scans were used to calculate the true inclination and anteversion component angles. The absolute difference between the true and estimated values was calculated to determine the mean and standard deviation of the survey results. Interrater reliability was determined through interclass correlation coefficients.ResultsA majority of surgeons preferred the direct anterior approach (83.3%) and utilized IF during surgery (70%). Surgeons surveyed were on average 5.9° away from the true value of inclination (standard deviation = 4.7) and 8.8° away from the true value of anteversion (standard deviation = 6.0). Respondents were within 5° of both inclination and anteversion in 19.7% of cases, and within 10° in 57.3% of cases. All surgeons were determined to have poor reliability in estimating anteversion (interclass correlation coefficient < 0.5). Only 2 surgeons were determined to have moderate reliability when estimating inclination.ConclusionsSurgeons, when solely relying on IF for the estimation of anteversion and inclination, are unreliable. Utilization of other techniques in conjunction with IF would improve observer reliability.