Introduction:. The lateral radiographs are useful in evaluation of the acetabular
Several radiological methods of measuring anteversion
of the acetabular component after total hip replacement (THR) have
been described. These studies used different definitions and reference
planes to compare methods, allowing for misinterpretation of the
results. We compared the reliability and accuracy of five current
methods using plain radiographs (those of Lewinnek, Widmer, Liaw,
Pradhan, and Woo and Morrey) with CT measurements, using the same
definition and reference plane. We retrospectively studied the plain
radiographs and CT scans in 84 hips of 84 patients who underwent
primary THR. Intra- and inter-observer reliability were high for
the measurement of inclination and anteversion with all methods
on plain radiographs and CT scans. The measurements of inclination on
plain radiographs were similar to the measurements using CT (p =
0.043). The mean difference between CT measurements was 0.6° (-5.9°
to 6.8°). Measurements using Widmer’s method were the most similar to those
using CT (p = 0.088), with a mean difference between CT measurements
of -0.9° (-10.4° to 9.1°), whereas the other four methods differed
significantly from those using CT (p <
0.001). This study has shown that Widmer’s method is the best for evaluating
the anteversion of the acetabular component on plain radiographs. Cite this article:
In 2021, Vigdorchik et al. published a large multicentre study validating their simple Hip-Spine Classification for determining patient-specific acetabular component positioning in total hip arthroplasty (THA). The purpose of our study was to apply this Hip-Spine Classification to a sample of Australian patients undergoing THA surgery to determine the local acetabular component positioning requirements. Additionally, we propose a modified algorithm for adjusting
Aims. The aim of this study was to identify the optimal lip position for total hip arthroplasties (THAs) using a lipped liner. There is a lack of consensus on the optimal position, with substantial variability in surgeon practice. Methods. A model of a THA was developed using a 20° lipped liner. Kinematic analyses included a physiological range of motion (ROM) analysis and a provocative dislocation manoeuvre analysis. ROM prior to impingement was calculated and, in impingement scenarios, the travel distance prior to dislocation was assessed. The combinations analyzed included nine cup positions (inclination 30-40-50°, anteversion 5-15-25°), three stem positions (anteversion 0-15-30°), and five lip orientations (right hip 7 to 11 o’clock). Results. The position of the lip changes the ROM prior to impingement, with certain combinations leading to impingement within the physiological ROM. Inferior lip positions (7 to 8 o’clock) performed best with cup inclinations of 30° and 40°. Superior lip positions performed best with cup inclination of 50°. When impingement occurs in the plane of the lip, the lip increases the travel distance prior to dislocation. Inferior lip positions led to the largest increase in jump distance in a posterior dislocation provocation manoeuvre. Conclusion. The lip orientation that provides optimal physiological ROM depends on the orientation of the cup and stem. For a THA with stem
Dislocation is a serious complication to be avoided in total hip arthroplasty (THA) and its incidence risk increases in revision surgery. Combined anteversion (CA) of the cup and stem is a concept for appropriate implant positioning; however, the effect of functional changes in femoral rotation has not been well investigated. The aim of this study was to investigate whether functional CA, considering femoral rotation, is associated with dislocation in patients undergoing revision THA. Seventy-three patients who underwent revision THA and had at least one year of follow-up with pre- and postoperative supine CT imaging were included. Cup and stem were placed with a target combined angle of 37.3° using Widmer's formula. Anatomical and functional CA was calculated postoperatively using the following formula: Anatomical CA:
Aims. Spinopelvic mobility plays an important role in functional acetabular component position following total hip arthroplasty (THA). The primary aim of this study was to determine if spinopelvic hypermobility persists or resolves following THA. Our second aim was to identify patient demographic or radiological factors associated with hypermobility and resolution of hypermobility after THA. Methods. This study investigated patients with preoperative posterior hypermobility, defined as a change in sacral slope (SS) from standing to sitting (ΔSS. stand-sit. ) ≥ 30°. Radiological spinopelvic parameters, including SS, pelvic incidence (PI), lumbar lordosis (LL), PI-LL mismatch, anterior pelvic plane tilt (APPt), and spinopelvic tilt (SPT), were measured on preoperative imaging, and at
six weeks and a minimum of
one year postoperatively. The severity of bilateral hip osteoarthritis (OA) was graded using Kellgren-Lawrence criteria. Results. A total of 136 patients were identified as having preoperative spinopelvic hypermobility. At one year after THA, 95% (129/136) of patients were no longer categorized as hypermobile on standing and sitting radiographs (ΔSS. stand-sit. < 30°). Mean ΔSS. stand-sit. decreased from 36.4° (SD 5.1°) at baseline to 21.4° (SD 6.6°) at one year (p < 0.001). Mean SS. seated. increased from baseline (11.4° (SD 8.8°)) to one year after THA by 11.5° (SD 7.4°) (p < 0.001), which correlates to an 8.5° (SD 5.5°) mean decrease in seated functional
Introduction. Lumbar spine fusion in patients undergoing THA (total hip arthroplasty) is a known risk factor for hip dislocation with some studies showing a 400% increased incidence compared to the overall THA population. Reduced spine flexibility can effectively narrow the
Introduction. Many authors have described component position and leg length discrepancy (LLD) after total hip arthroplasty (THA) as the most important factors for good postoperative outcomes. However, regarding the relationships between component position and different approaches for THA, the optimal approach for component position and LLD remains unknown. The aims of this study were to compare these factors among the direct anterior, posterolateral, and direct lateral approaches on postoperative radiographs retrospectively, and determine which approach leads to good orientation in THA. Methods. We retrospectively evaluated 150 patients who underwent unilateral primary THA in our department between January 2009 and December 2014, with the direct anterior, posterolateral, or direct lateral approach used in 50 patients each. Patients with significant hip dysplasia (Crowe 3 or 4), advanced erosive arthritis, prevented osteotomy of the contralateral hip, and body mass index (BMI) of more than 30 were excluded. The mean age, sex, and preoperative diagnosis of the affected hip were equally distributed in patients who underwent THA with the different approaches. The mean BMI did not differ significantly among the groups. The radiographic measurements included cup inclination angle, dispersion of cup inclination from 40°, and LLD on an anteroposterior pelvic radiograph, and
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
Dual mobility cups (DMC) reduce the risk of dislocation in femoral neck fractures (FNF). Direct anterior approach (DAA), historically promoted for better stability, has been developed in recent years for better functional results. The aim of this study was to compare the early functional results of DMC in FNF by DAA versus posterolateral approach (PLA). A prospective study was conducted on a continuous series of patients who received DMC for FNF by DAA or PLA. The primary endpoint was Harris Hip Score and Parker score assessed at the first follow-up visit. Intraoperative complications were collected during hospitalization. One year clinical results and all cause revision rate were also collected. Radiographic data of cup positioning and limb length were evaluated. Fifty-two patients were included in the DAA group and 54 in the PLA group. Two patients were lost to follow-up. The mean age was 72.8 years. There was no significant difference in HHS or Parker score at 3 and 12 months follow up (p=0.6, p= 0.75). DAA was associated with more intraoperative complications with 4 fractures and 1 femoral nerve deficit (p=0.018). There were 3 revisions in the DAA group (1 infection, 1 dislocation, 1 peri prosthetic fracture) and 1 in the PLA group (infection), which was not statistically significant (p=0.34).
We have previously reported on the improved all-cause revision and improved revision for instability risk in lipped liner THAs using the NJR dataset. These findings corroborate studies from the Australian (AOANJRR) and New Zealand (NZOA) joint registries. The optimal orientation of the lip in THAs utilising a lipped liner remains unclear to many surgeons. The aim of this study was to identify impingement-free optimal liner orientations whilst considering femoral stem version, cup inclination and cup version. A cementless THA kinematic model was developed using a 20 degree XLPE liner. Physiological ROM and provocative dislocation manoeuvre analyses were performed. A total of 9 cup positions were analysed (inclination 30–40–50 degrees, anteversion 5-15-25 degrees) and combined with 3 stem positions (anteversion 0-15-30 degrees) and 5 lip orientations (right hip 11 to 7 o'clock). Some lip orientation/component position combinations lead to impingement within the physiological ROM range. Using a lipped liner increases the femoral head travel distance prior to dislocation when impingement occurs in the plane of the lip. In THAs with a cup inclination of 30 and 40 degrees, inferior lip orientations (7–8 o'clock for a right hip) performed best. Superior lip orientation performed best with a cup inclination of 50 degrees. Femoral stem version has a significant effect on the range of movement prior to impingement and hence the preferred lip orientation. The optimal orientation of the lip in lipped liner THA is dependent on the position of both the acetabular and femoral components. In the common component orientation combination of stem
The purpose of this preliminary study was to evaluate the feasibility and accuracy of HipAlign (OrthAlign, Inc., USA) system for cup orientation in total hip arthroplasty (THA). The subjects of this study were 5 hips that underwent primary cementless THA via a posterior approach in the lateral decubitus position. Evaluation 1; after reaming acetabular bone, a trial cup was placed in the reamed acetabulum in an aimed alignment using HipAlign. Then, the trial cup alignment was measured using HipAlign and CT-based navigation system in the radiographic definition. Evaluation 2; a cementless cup was placed in the reamed acetabular in an aimed alignment using CT-based navigation and cup alignment was measured using both methods. After operation, we measured the cup alignment using postoperative CT in each patient. In the results, the average cup inclination measured with HipAlign was around 5 degrees of true cup inclination angles. The average
Iliopsoas impingement occurs in between 5–30% of patients after hip arthroplasty and has been thought to only be caused by an oversized cup, cup malpositioning, or the depth of the psoas valley. However, no study has associated the relationship between preoperative measurements with the risk of impingement. This study sought to assess impingement between the iliopsoas and acetabular cup using a novel validated model to determine the risk factors for iliopsoas impingement. 413 patients received lower limb CT scans and lateral x-rays that were segmented, landmarked, and measured using a validated preoperative planning protocol. Implants were positioned according to the preference of ten experienced surgeons. The segmented bones were transformed to the standing reference frame and simulated with a novel computational model that detects impingement between the iliopsoas and acetabular cup. Definitions of patients at-risk and not at-risk of impingement were defined from a previous validation study of the simulation. At-risk patients were propensity score matched to not at-risk patients. 21% of patients were assessed as being at-risk of iliopsoas impingement. Significant differences between at-risk patients and not at-risk patients were observed in standing pelvic tilt (p << 0.01), standing femoral internal rotation (p << 0.01), medio-lateral centre-of-rotation (COR) change (p << 0.01), supine
The purpose of this study was to assess the variability in implant position between sides in patients who underwent staged, bilateral THA and whether variation from one side to the other affected patient-reported outcomes. A retrospective review was conducted on 207 patients who underwent staged, bilateral THA by the same surgeon from 2017–2022. Leg length, acetabular height, cup version, and coronal and sagittal stem angles were assessed radiographically and compared to the contralateral THA. Surgical approach and technology utilization were further assessed for their impact on variability. Linear regression was used to model the relationship between side-to-side variability and patient-reported outcome measures (PROMS). Between sides, mean radiographic leg length varied by 4.6mm (0.0–21.2), acetabular height varied by 3.3mm (0.0–13.7), anteversion varied by 8.2° (0.0 to 28.7), coronal stem alignment varied by 1.1° (0.0 to 6.9), and sagittal angulation varied by 2.3° (0.0 to 10.5). The anterior approach resulted in more variability in stem angle position in both the coronal (1.3° vs. 1.0°, p=0.036) and sagittal planes (2.8° vs. 2.0° p=0.012) compared to the posterior approach. The posterior approach generally led to more anteversion than the anterior approach. Use of robotics or navigation for acetabular positioning did not increase side-to-side variability in cup-related position or leg length. Despite considerable side-to-side variability, Hip dysfunction and osteoarthritis outcome scores (HOOS JR) were not affected by higher levels of position inconsistency. Staged, bilateral THA results in considerable variability in component position between sides. The anterior approach leads to more side-to-side variability in sagittal stem angle and
Introduction. Pelvic flexion and extension in different body positions can affect acetabular orientation after total hip arthroplasty, and this may predispose patients to dislocation. The purpose of this study was to evaluate functional acetabular component position in total hip replacement patients during standing and sitting. We hypothesize that patients with degenerative lumbar disease will have less pelvic extension from standing to sitting, compared to patients with a normal lumbar spine or single level spine disease. Methods. A prospective cohort of 20 patients with primary unilateral THR underwent spine-to-ankle standing and sitting lateral radiographs that included the lumbar spine and pelvis using EOS imaging. Patients were an average age of 58 ± 12 years and 6 patients were female. Patients had (1) normal lumbar spines or single level degeneration, (2) multilevel degenerative disc disease or (3) scoliosis. We measured acetabular anteversion (cup relative to the horizontal), sacral slope angle (superior endplate of S1 relative to the horizontal), and lumbar lordosis angles (superior endplates of L1 and S1). We calculated the absolute difference in acetabular anteversion and the absolute difference in lumbar lordosis during standing and sitting (Figure 1). Results. Nine patients had normal lumbar spines or scoliosis, and 11 patients had multilevel disc disease. The median change in
Introduction. The direct anterior approach (DAA) for total hip arthroplasty continues to gain popularity. Consequently, more procedures are being performed with the patient supine. The approach often utilizes a special leg positioner to assist with femoral exposure. Although the supine position may seem to allow for a more reproducible pelvic position at the time of cup implantation, there is limited evidence as to the effects on pelvic tilt with such leg positioners. Furthermore, the DAA has led to increased popularity of specific softwares, ie. Radlink or JointPoint, that facilitate the intra-op analysis of component position from fluoroscopy images. The aim of this study was to assess the difference in cup orientation measurements between intra-op fluoroscopy and post-op CT. Methods. A consecutive series of 48 DAA THAs were performed by a single surgeon in June/July 2018. All patients received OPS. TM. pre-operative planning (Corin, UK), and the cases were performed with the patient supine on the operating table with the PURIST leg positioning system (IOT, Texas, USA). To account for variation in pelvic tilt on the table, a fluoroscopy image of the hemi-pelvis was taken prior to cup impaction, and the c-arm rotated to match the shape of the obturator foramen on the supine AP Xray. The final cup was then imaged using fluoroscopy, and the radiographic cup orientation measured manually using Radlink GPS software (Radlink, California, USA). Post-operatively, each patient received a low dose CT scan to measure the radiographic cup orientation in reference to the supine coronal plane. Results. Mean cup orientation from intra-op fluoro was 38° inclination (32° to 43°) and 24° anteversion (20° to 28°). Mean cup orientation from post-op CT was 40° inclination (29° to 47°) and 30° anteversion (22° to 38°). Cups were, on average, 6° more anteverted and 2° more inclined on post-op CT than intra-op. These differences were statistically significant, p<0.001. All 48 cups were more anteverted on CT than intra-op. There was no statistical difference between pre- and post-op supine pelvic tilt (4.1° and 5.1° respectively, p = 0.41). Discussion. We found significant differences in cup orientation measurements performed from intra-op fluoro to those from post-op CT. This is an important finding given the attempts to adjust for pelvic tilt during the procedure. We theorise two sources of error contributing to the measurement differences. Firstly, the under-compensation for the anterior pelvic tilt on the table. Although the c-arm was rotated to match the obturator foramen from the pre-op imaging, we believe the manual matching technique utilised in the Radlink software carries large potential errors. This would have consistently led to an under-appreciation of the adjustment angle required. Secondly, the manual nature of defining the cup ellipse on the fluoro image has previously been shown to underestimate the degree of
Introduction. To obtain a better range of motion and to reduce the risk of dislocation, neck and
Introduction. Although pelvic tilt does not significantly change after primary total hip arthroplasty (THA) at a short term, can vary over time due to aging and the possible appearence of sagittal spine disorders. Cup positioning relative to the stem can be influenced due to these changes. Purpose. We assessed the evolution of pelvic tilt and cup position after THA for a minimum follow-up of five years and the possible appearence of complications. Materials and methods. 47 patients underwent same single THA between 2008 and 2012. All were diagnosed with primary osteoarthritis and their mean age was 70.2 years (range, 63 to 75). There were 28 male patients, 19 had a contralateral THA, 17 were studied for lumbar pathology and three were operated for lumbo-sacral fusion. Radiological analysis included sacro- femoral-pubic and acetabular abduction angles on the anteroposterior pelvic view; and
Spinopelvic mobility describes the change in lumbar lordosis and pelvic tilt from standing to sitting position. For 1° of posterior pelvic tilt, functional
Navigation during the positioning of the acetabular component in total hip replacement is a promising tool to improve the prosthetic alignment. Correct placement of the cup will reduce the risk of mechanical complications such as dislocations and impingement. All navigation systems, be they CT or infra-red based, require exact determination of the symphysis and both anterior superior iliac spines, the landmarks of the patient’s pelvis. The accuracy of the intraoperative palpation of these landmarks influences the outcome of the cup-angulation more than any other factor. Our experience in over 700 infra-red based navigated total hip replacements since 2002, shows a wide variation of acetabular