INTRODUCTION. Poor
Introduction. Appropriate
Optimal alignment of the acetabular cup component is crucial for good outcome of total hip arthroplasty [THA]. Increased accuracy of implant positioning may improve clinical outcome. To achieve this, patient specific instrumentation was developed. A patient-specific guide manufactured by 3D printing was designed to aid in positioning of the cup component with a pre-operatively defined anteversion and inclination angle. The guide fits perfectly on the acetabular rim. An alignment K-wire in a pre-operatively planned orientation is used as visual reference during cup implantation. Accuracy of the device was tested on 6 cadaveric specimens. During the experiment, cadavers were positioned for a THA procedure using a posterolateral approach. A normal-sized incision was made and approach used as in the conventional surgical procedure. The PSI was subsequently fitted onto the acetabular rim and secured into its unique position due to its patient specific design. The metallic pin was placed in a drill hole of the PSI. Post-operative CT image data of each acetabulum with the placed pin were transferred to Mimics and the 3D model was registered to the pre-operative one. The anteversion and inclination of the placed pin was calculated and compared to the pre-operatively planned orientation. The absolute difference in degrees was evaluated. A secondary test was carried out to assess the error during impaction while observing the alignment K-wire as a visual reference. In a laboratory setting, error during impaction with a visual reference of the K-wire was measured. Deviation from planning showed to be on average 1.04° for anteversion and 2.19° for inclination. By visually aligning the impactor with this alignment K-wire, the surgeon may achieve cup placement as pre-operatively planned. The effect of the visual alignment itself was also evaluated in a separate test-rig showing minimal deviations in the same range. The alignment validation test resulted in an average deviation of 1.2° for inclination and 1.4° for anteversion between the metallic alignment K-wire used as visual reference and the metallic K-wire impacted by the test subjects. The inter-user variability was 0.9° and 0.8° for anteversion and inclination respectively. The intra-user variability was 1.6° and 1.0° for anteversion and inclination respectively. Tests per test subject were conducted in a consecutive manner. We investigated the accuracy of two factors affecting accuracy in the cup insertion with PSI, i.e. accuracies of the errors of bony fitting and cup impaction. Since the accuracy of the major contributing factors to the overall accuracy of PSI for cup insertion with linear visual reference of a metallic K-wire was within the acceptable range of 2 to 3 degrees, we state that the PSI we have designed assists to achieve the preoperatively planned orientation of the cup and as such leads to the reduction of outliers in
Obtaining consistently an optimal cup orientation in THA is vital to obtain adequate head coverage and maximum impingement free range of motion and thus reduce the incidence of polyethylene wear, cup loosening, and dislocation rates associated with a limited range of motion. It is clear that THA instability, the most frequent cause of early failure, is a complex problem related to a wide range of causes. However cup orientation is one of the surgeon dependant potentially modifiable variables that continue to have an important influence due to the lack of reliable means of assuring an adequate orientation of the components, particularly the cup anteversion. Standard mechanical guides like Muller’s have been shown to be inaccurate and imprecise. Not surprisingly, dislocation is the most frequent short term complication after a THA.
Achieving optimal
Iliopsoas tendonitis after total hip arthroplasty (THA) can be a considerable cause of pain and patient dissatisfaction. The optimal cup position to avoid iliopsoas tendonitis has not been clearly established. Implant designs have also been developed with an anterior recess to avoid iliopsoas impingement. The purpose of this cadaveric study was to determine the effect of cup position and implant design on iliopsoas impingement. Bilateral THA was performed on three fresh frozen cadavers using oversized (jumbo) offset head center revision acetabular cups with an anterior recess (60, 62 and 66 mm diameter) and tapered wedge primary stems through a posterior approach. A 2mm diameter flexible stainless steel cable was inserted into the psoas tendon sheath between the muscle and the surrounding membrane to identify the location of the psoas muscle radiographically. CT scans of each cadaver were imported in an imaging software. The acetabular shells, cables as well as pelvis were segmented to create separate solid models of each. The offset head center shell was virtually replaced with an equivalent diameter hemispherical shell by overlaying the outer shell surfaces of both designs and keeping the faces of shells parallel. The shortest distance between each shell and cable was measured. To determine the influence of cup inclination and anteversion on psoas impingement, we virtually varied the inclination (30°/40°/50°) and anteversion (10°/20°/30°) angles for both shell designs. The CT analysis revealed that the original orientation (inclination/anteversion) of the shells implanted in 3 cadavers were as follows: Left1: 44.7°/23.3°, Right1: 41.7°/33.8°, Left2: 40/17, Right2: 31.7/23.5, Left3: 33/2908, Right3: 46.7/6.3. For the offset center shells, the shell to cable distance in all the above cases were positive indicating that there was clearance between the shells and psoas. For the hemispherical shells, in 3 out of 6 cases, the distance was negative indicating impingement of psoas. With the virtual implantation of both shell designs at orientations 40°/10°, 40°/20°, 40°/30° we found that greater anteversion helped decrease psoas impingement in both shell designs. When we analyzed the influence of inclination angle on psoas impingement by comparing wire distances for three orientations (30°/20°, 40°/20°, 50°/20°), we found that the effect was less pronounced. Further analysis comparing the offset head center shell to the conventional hemispherical shell revealed that the offset design was favored (greater clearance between the shell and the wire) in 17 out of 18 cases when the effect of anteversion was considered and in 15 out of 18 cases when the effect of inclinations was considered. Our results indicate that psoas impingement is related to both cup position and implant geometry. For an oversized jumbo cup, psoas impingement is reduced by greater anteversion while cup inclination has little effect. An offset head center cup with an anterior recess was effective in reducing psoas impingement in comparison to a conventional hemispherical geometry. In conclusion, adequate anteversion is important to avoid psoas impingement with jumbo acetabular shells and an implant with an anterior recess may further mitigate the risk of psoas impingement.
Iliopsoas tendonitis after total hip arthroplasty (THA) can be a considerable cause of pain and patient dissatisfaction. The optimal cup position to avoid iliopsoas tendonitis has not been clearly established. Implant designs have also been developed with an anterior recess to avoid iliopsoas impingement. The purpose of this cadaveric study was to determine the effect of cup position and implant design on iliopsoas impingement. Bilateral THA was performed on three fresh frozen cadavers using oversized (jumbo) offset head center revision acetabular cups with an anterior recess (60, 62 and 66 mm diameter) and tapered wedge primary stems through a posterior approach. The relatively large shell sizes were chosen to simulate THA revision cases. At least one fixation screw was used with each shell. A 2mm diameter flexible stainless steel cable was inserted into the psoas tendon sheath between the muscle and the surrounding membrane to identify the location of the psoas muscle radiographically. Following the procedure, CT scans were performed on each cadaver. The CT images were imported in an imaging software for further analysis. The acetabular shells, cables as well as pelvis were segmented to create separate solid models of each. To compare the offset head center shell to a conventional hemispherical shell in the same orientation, the offset head center shell was virtually replaced with an equivalent diameter hemispherical shell by overlaying the outer shell surfaces of both designs and keeping the faces of shells parallel. enabled us to assess the relationship between the conventional shells and the cable. The shortest distance between each shell and cable was measured. To determine the influence of cup inclination and anteversion on psoas impingement, we virtually varied the inclination (30°/40°/50°) and anteversion (10°/20°/30°) angles for both shell designs.Introduction
Materials
Background. Trust in the validity of a measurement tool is critical to its function in both clinical and educational settings. Acetabular cup malposition within total hip arthroplasty (THA) can lead to increased dislocation rates, impingement and increased wear as a result of edge loading. We have developed a THA simulator incorporating a foam/Sawbone pelvis model with a modified Microsoft HoloLens® augmented reality (AR) headset. We aimed to measure the trueness, precision, reliability and reproducibility of this platform for translating spatial measurements of
*Index; Synchronized Inclination = arctan [tan (Operative AV) ÷ tan (Anatomic AV)] Synchronized AV = arctan[tan (Anatomic AV) x sin (synchronized Inclination)] or arctan[tan (Operative AV) x cos (Synchronized Inclination
Background. Complications such as dislocations, impingement and early wear following total hip arthroplasty (THA) increase with acetabular cup implant malorientation. These errors are more common with low-volume centres or in novice hands. Currently, this skill is most commonly taught during real surgery with an expert trainer, but simulated training may offer a safer and more accessible solution. This study investigated if a novel MicronTracker® enhanced Microsoft HoloLens® augmented reality (EAR) headset was as effective as one-on-one expert surgeon (ES) training for teaching novice surgeons hip cup orientation skill. Methods. Twenty-four medical students were randomly assigned to EAR or ES training groups. Participants used a modified sawbone/foam pelvis model for hip cup orientation simulation. A validated EAR headset measured the
Achieving accurate implant positioning and restoring native hip biomechanics are key surgeon-controlled technical objectives in total hip arthroplasty (THA). The primary objective of this study was to compare the reproducibility of the planned preoperative centre of hip rotation (COR) in patients undergoing robotic arm-assisted THA versus conventional THA. This prospective randomized controlled trial (RCT) included 60 patients with symptomatic hip osteoarthritis undergoing conventional THA (CO THA) versus robotic arm-assisted THA (RO THA). Patients in both arms underwent pre- and postoperative CT scans, and a patient-specific plan was created using the robotic software. The COR, combined offset, acetabular orientation, and leg length discrepancy were measured on the pre- and postoperative CT scanogram at six weeks following surgery.Aims
Methods
Ideal placement of the acetabular component remains
elusive both in terms of defining and achieving a target. Our aim
is to help restore original anatomy by using the transverse acetabular
ligament (TAL) to control the height, depth and version of the component.
In the normal hip the TAL and labrum extend beyond the equator of
the femoral head and therefore, if the definitive acetabular component
is positioned such that it is cradled by and just deep to the plane
of the TAL and labrum and is no more than 4mm larger than the original
femoral head, the centre of the hip should be restored. If the face
of the component is positioned parallel to the TAL and psoas groove
the patient specific version should be restored. We still use the
TAL for controlling version in the dysplastic hip because we believe
that the TAL and labrum compensate for any underlying bony abnormality. The TAL should not be used as an aid to inclination. Worldwide,
>
75% of surgeons operate with the patient in the lateral decubitus
position and we have shown that errors in post-operative radiographic
inclination (RI) of >
50° are generally caused by errors in patient positioning.
Consequently, great care needs to be taken when positioning the
patient. We also recommend 35° of apparent operative inclination
(AOI) during surgery, as opposed to the traditional 45°. Cite this article:
In order to avoid complications of hip arthroplasty such as dislocation, impingement and eccentric liner wear accurate acetabular orientation is essential. The three-dimensional assessment of
Aim: In order to avoid complications of hip arthroplasty such as dislocation, impingement and eccentric liner wear accurate acetabular orientation is essential. The three-dimensional assessment of
The goal of this study was to validate accuracy and reproducibility of a new 2D/3D reconstruction-based program called “HipRecon” for determining cup orientation after THA. “HipRecon” uses a statistical shape model based 2D/3D deformable registration technique that can reconstruct a patient-specific 3D model from a single standard AP pelvic X-ray radiograph. Required inputs include a digital radiograph, the pixel size, and the film-to-source distance. No specific calibration of the X-ray, or a CAD (computer-assisted design) model of the implant, or a CT-scan of the patient is required. Cup orientation is then calculated with respect to the anterior pelvic plane that is derived from the reconstructed 3D-model. The validation study was conducted on datasets of 29 patients (31 hips). Among them, there were 15 males and 14 females. Each dataset has one post-operative X-ray radiograph and one post-operative CT-scan. The post-operative CT scan for each patient was used to establish the ground truth for the cup orientation. Radiographs with deep centering (7 radiographs), or of pelvises with fractures (2 radiographs), or with both (1 radiograph), or of non-hemispherely shaped cup (1 radiograph) were assessed separately from the radiographs without above mentioned phenomena (18 radiographs) to estimate a potential influence on the 2D/3D reconstruction accuracy. To make the description easier, we denote those radiographs with above mentioned phenomena as non-normal cases and those without as normal cases. The cup anteversions and inclinations that were calculated by “HipRecon” were compared to the associated ground truth. To validate the reproducibility and the reliability, one observer conducted twice measurements for each dataset using “HipRecon”. The mean accuracy for the normal cases was 0.4° ± 1.8° (−2.6° to 3.3°) for inclination and 0.6° ± 1.5° (−2.0° to 3.9°) for anteversion, and the mean accuracy for the non-normal cases was 2.3° ± 2.4° (−2.1° to 6.3°) for inclination and 0.1° ± 2.8° (−4.6° to 5.1°) for anteversion. Comparing the measurement from the normal radiographs to those from the non-normal radiographs using the Mann-Whitney U-test, we found a significant difference in measuring cup inclination (p = 0.01) but not in measuring cup anteversion (p = 0.3). Bland-Altman analysis of those measurements from the normal cases indicated that no systematical error was detected for “HipRecon,” as the mean of the measurement pairs were spread evenly and randomly for both inclination and anteversion. “HipRecon” showed a very good reproducibility for both parameters with an intraclass correlation coefficient (ICC) for inclination of 0.98 (95% Confidence Limits (CL): 0.96–0.99) and for anteversion of 0.96 (95% CL: 0.91–0.98). Accurate assessment of the
Introduction.
Background. Acetabular cup malpositioning during total hip arthroplasty (THA) is known to lead to impingement, instability, wear-induced osteolysis, and increased rates of revision surgery. The purpose of this study was to independently evaluate the accuracy of
Component placement and the individual's functional posture play key roles in mechanical complications and hip dysfunction after total hip arthroplasty (THA). The challenge is how to measure these. X-rays lack accuracy and CT scans increase radiation dose. A newer imaging modality, EOSTM, acquires low-dose, simultaneous, perpendicular anteroposterior and lateral views while providing a global view of the patient in a functional standing or sitting position, leading to a 3D reconstruction for parameter calculation. The purpose of the present study was to develop an approach using the EOS system to compare patients with good versus poor results after THA and to report our preliminary experiences using this technique. A total of 35 patients were studied: 17 with good results after THA (G-THA), 18 with poor results (P-THA). The patients were operated on or referred for follow-up to a single expert surgeon, between 2001 and 2011, with a minimum follow-up of at least two years.
Introduction. Accurate and reproducible cup positioning is one the most important technical factors that affects outcomes of total hip arthroplasty (THA). Although Lewinnek's safe zone is the most accepted range for anteversion and abduction angles socket orientation, the effect of fixed lumbosacral spine on pelvic tilt and obliquity is not yet established. Questions:. What is the change in anteversion and abduction angle from standing to sitting in a consecutive cohort of patients undergoing THA?. What is the effect of fixed and flexible spinal deformities on
Abstract. Objectives. Accurate orientation of the acetabular component during a total hip replacement is critical for optimising patient function, increasing the longevity of components, and reducing the risk of complications. This study aimed to determine the validity of a novel VR platform (AescularVR) in assessing acetabular component orientation in a simulated model used in surgical training. Methods. The AescularVR platform was developed using the HTC Vive® VR system hardware, including wireless trackers attached to the surgical instruments and pelvic sawbone. Following calibration, data on the relative position of both trackers are used to determine the
Introduction. Excessive standing posterior pelvic tilt (PT), lumbar spine stiffness, low pelvic Incidence (PI), and severe sagittal spinal deformity (SSD) have been linked to increased dislocation rates. We aimed to compare the prevalence of these 4 parameters in unstable and stable primary Total Hip Arthroplasty (THA) patients. Methods. In this retrospective cohort study, 40 patients with instability following primary THA for osteoarthritis were referred for functional analysis. All patients received lateral X-rays in standing and flexed seated positions to assess functional pelvic tilt and lumbar lordosis (LL). Computed tomography scans were used to measure pelvic incidence and
Introduction & aims. Apparently well-orientated total hip replacements (THR) can still fail due to functional component malalignment. Previously defined “safe zones” are not appropriate for all patients as they do not consider an individual's spinopelvic mobility. The Optimized Positioning System, OPS. TM. (Corin, UK), comprises preoperative planning based on a patient-specific dynamic analysis, and patient-specific instrumentation for delivery of the target component alignment. The aim of this study was to determine the early revision rate from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) for THRs implanted using OPS. TM. . Method. Between January 4. th. 2016 and December 20. st. 2017, a consecutive series of 841 OPS. TM. cementless total hip replacements were implanted using a Trinity acetabular cup (Corin, UK) with either a TriFit TS stem (98%) or a non-collared MetaFix stem (2%). 502 (59%) procedures were performed through a posterior approach, and 355 (41%) using the direct superior approach. Mean age was 64 (range; 27 to 92) and 51% were female. At a mean follow-up of 15 months (range; 3 to 27), the complete list of 857 patients was sent to the AOANJRR for analysis. Results. There were 5 revisions:
. a periprosthetic femoral fracture at 1-month post-op in a 70F. a ceramic head fracture at 12-months post-op in a 59M. a femoral stem loosening at 7-months post-op in a 58M. a femoral stem loosening at 16-months post-op in a 64M. an anterior dislocation in a 53M, that was revised 9 days after the primary procedure. CT analysis, prior to revision surgery, revealed
Introduction. Most of studies on Total Hip Arthroplasty (THA) are focused on
Impingement of total hip replacements (THRs) can cause rim damage of polyethylene liners, and lead to dislocation and/or mechanical failure of liner locking mechanisms[1]. Previous work has focussed on the influence of femoral neck profile on impingement without consideration of neck-shaft angle. This study assessed the occurrence of impingement with two different stem designs (Corail standard [135°] and coxa vara [125°]) under different activities with varying
Background. Virtual Reality (VR) uses headsets and motion-tracked controllers so surgeons can perform simulated total hip arthroplasty (THA) in a fully-immersive, interactive 3D operating theatre. The aim of this study was to investigate the effect of laboratory-based VR training on the ability of surgical trainees to perform direct anterior approach THA on cadavers. Methods. Eighteen surgical trainees (CT1-ST4) with no prior experience of direct anterior approach (DAA) THA completed an intensive 1-day course (lectures, dry-bone workshops and technique demonstrations). They were randomised to either a 5-week protocol of VR simulator training or conventional preparation (operation manuals and observation of real surgery). Trainees performed DAA-THA on cadaveric hips, assisted by a passive scrub nurse and surgical assistant. Performance was measured on the Intercollegiate Surgical Curriculum Project (ISCP) procedure-based assessment (PBA), on a 9-point global summary score (Table 1). This was independently assessed by 2 hip surgeons blinded to group allocation. The secondary outcome measure was error in cup orientation from a predefined target (40° inclination and 20° anteversion). Results. Surgeons trained using VR performed a cadaveric DAA-THA significantly better than those using conventional preparation, as assessed by
Introduction. Accurate
Introduction. Accurate
Acetabular cup placement in total hip replacement surgery is often difficult to assess, especially in the lateral position and using the posterior approach. On table control X-Rays are not always accessible, especially in the government sector. Conventional techniques and computer assisted surgery (CAS), are currently the two most popular methods for proper placement of the acetabular cup in Lewinnek's safe zone of orientation (anteversion 15°–10° and lateral inclination 40°±10°). We developed a simple way to get accurate cup placement using Smartphone technology. Methods:. A spirit level application was downloaded to the Smartphone. The acetabulum inclination was measured on the pre-operative X-Rays. The phone is placed in a sterile bag and then used intra-operatively, to measure and set our
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.
Introduction. There is increasing interest in the functional positions the pelvis assumes with activities of daily living and its effect on
Positioning of the hip resurfacing is crucial for its long term survival and is critical in young patients for some reasons; manly increase the wear in the components and change the load distribution. THR have increased in the last years, mainly in young patients between 45 to 59 years old. The resurfacing solution is indicated for young patients with good bone quality. A long term solution is required for these patients to prevent hip revision. The resurfacing prosthesis Birmingham Hip Resurfacing (BHR) was analyzed in the present study by in vitro experimental studies. This gives indications for surgeons when placing the acetabular cup. One synthetic left model of composite femur (Sawbones®, model 3403), which replicates the cadaveric femur, and four composite pelvic bones (Sawbones®, model 3405), were used to fix the commercial models of Hip resurfacing (Birmingham model). The resurfacing size was chosen according to the head size of femurs with 48 mm head diameter and a cup with 58 mm. They were introduced by an experimented surgeon with instrumental of prosthesis. The cup is a press fit system and the hip component was cemented using bone cement Simplex, Stryker Corp. The acetabular cup was analyzed in 4 orientations; in anteverion with 15º and 20°; and in inclination 40 and 45°. Combinations of these were also considered. The experimental set-up was applied according to a system previously established by Ramos et al. (2013) in the anatomic position. The femur rotates distally and the Pelvic moves vertically as model changes, such that the same boundary conditions are satisfied. This system allows compensating motions of the
INTRODUCTION. Acetabular cup malpositioning has been implicated in instability and wear-related complications after total hip arthroplasty. Although computer navigation and robotic assistance have been shown to improve the precision of implant placement, most surgeons use mechanical and visual guides to place acetabular components. Authors have shown that, when using a bean bag positioner, mechanical guides are misleading as they are unable to account for the variability in pelvic orientation during positioning and surgery. However, more rigid patient positioning devices may allow for more accurate free hand cup placement. To our knowledge, no study has assessed the ability of rigid devices to afford surgeons with ideal pelvic positioning throughout surgery. The purpose of this study is to utilize robotic-arm assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. METHODS. 100 hips (94 patients) prospectively underwent total hip Makoplasty in the lateral decubitus position from the posterior approach; 77 stabilized by universal lateral positioner, and 23 by peg board. After dislocation but prior to reaming, one fellowship trained arthroplasty surgeon manually placed the robotic arm parallel to both the longitudinal axis of the patient and the horizontal surface of the operating table, which, if the pelvis were oriented perfectly, would represent 0 degrees of anteversion and 0 degrees of inclination. The CT-templated computer software then generated true values of this perceived zero degrees of anteversion and inclination based on the position of the robot arm registered to a preoperative pelvic CT. Therefore, variations in pelvic positioning are represented by these robotic navigation generated values. To assure the accuracy of robotic measurements, cup anteversion and inclination at times of impaction were recorded and compared to those calculated via the trigonometric ellipse method of Lewinnek on standardized 3 months postoperative X-rays. RESULTS. Mean alteration in anteversion and inclination values were 1.7 degrees (absolute value 5.3 degrees, range −20 – 20 degrees) and 1.6 degrees (absolute value 2.6 degrees, range −8 – 10 degrees) respectively. 22% of anteversion values were altered by >10 degrees; 41% by > 5 degrees. There was no difference between positioners (p=0.36) and regression analysis revealed that anteversion differences were correlated with BMI (p=0.02). Robotic navigation acetabular cup anteversion (mean 21.8 degrees) was not different from postoperative X-ray anteversion (mean 21.9 degrees)(p=0.50), nor was robotic navigation acetabular cup inclination (mean 40.6 degrees) different from postoperative X-ray inclination (mean 40.5 degrees)(p=0.34). DISCUSSION AND CONCLUSION. Rigid pelvic positioning devices present 5 to 20 degrees of variability in
Acetabular component malpositioning is the most common reason for instability and wear resulting in revision total hip arthroplasty (THA). The current study aimed to assess a novel mechanical navigation device which was designed to simply and efficiently indicate appropriate cup orientation during surgery. The accuracy was compared to a series of hip arthroplasties performed using CT-based computer-assisted cup placement. The study group consisted of 70 THAs performed using the mechanical device. The control group consisted of 146 THAs performed using CT-based computer navigation. Postoperative cup positioning was measured using a validated 2D/3D-matching method. An outlier was defined outside a range of ± 10 degrees from the planned inclination or anteversion. In the study group the mean accuracy for inclination was 1.3 ± 3.4 (-6.6 – 8.2) and 1.0 ± 4.1 (-8.8 – 9.5) for anteversion with no outliers for either parameter. In the control group the accuracy for anteversion (3.0 ± 5.8 [-11.8 - 19.6]; p=0.6%) and the percentage of outliers (6.8%; p=3.3%) differed significantly. The accuracy for inclination (3.5 ± 4.1 [-12.7 - 9.5]; p=21.4%) and the percentage of ouliers (4.8%; p=9.9%) did not differ significantly. The use of this mechanical navigation device can result in similar accuracy of
A 10° deviation from the ideal cup orientation in Metal on Metal (MoM) bearing couples leads to increased wear and the subsequent risk of early revision surgery. We assessed the accuracy of orthopaedic trainees and consultants in achieving optimal
In total hip arthroplasty (THA),
The efficacy of an imageless navigation system in
INTRODUCTION.
Imageless navigation is useful in
INTRODUCTION. Several papers have reported the efficacy of an imageless navigation system in
Over the last few years low dose digital radiography (DR) has all but replaced traditional chemical image processing. This appears to have created a paradigm shift in the suitability of intraoperative radiographic guidance for total hip arthroplasty. It is the purpose of this publication to describe our preferred technique and assess its reliability in achieving the desired parameters of a successful total hip arthroplasty. A consecutive prospective evaluation of 150 primary total hip arthroplasties employing intraoperative digital radiography was carried out. An anteroposterior pelvic radiograph with the patient in the lateral decubitus position was obtained for all hips. The orientation of the intraoperative film was matched to that of the preoperative pelvic radiograph. The image was taken after placement of the acetabular component and best estimate of femoral trial size, position, and head and neck length. The DR system produced an image within 6 seconds of exposure. This trial radiograph was then used to make adjustments. Given that the cassette does not have to be moved for image processing, a precise anteroposterior film was obtained by simply adjusting the operating table. Two to three minutes were allotted for each radiograph. Corrections to stem size, cup position, screw length and position, limb length, and offset were made based on this intraoperative radiograph. The final intraoperative image was then compared to a postoperative standard radiograph in supine position at 2 weeks after total hip arthroplasty to verify the accuracy of intraoperative digital radiography. Abduction angle, limb length, offset, and canal fit and fill were assessed for confirmation of the validity of the intraoperative imaging technique. Acetabular abduction angle was determined with a mean of 43 degrees (range, 35 to 48 degrees). The intraoperative measurement was within 3 degrees of the postoperative measurement in all cases. Adjustment of
Background: There are no large comparative metal ion studies of commercially available hip resurfacing devices which have taken into account the effects of femoral size and cup inclination and anteversion. Patients and methods: Metal ion analysis is carried out routinely at our independent centre. We present the metal ion results of 95 unilateral ASR patients and 70 unilateral BHR patients. For all patients,
The aim was to review patients that had single stage bilateral total hip joint replacements (SSBTHJR) of two surgeons in the Wellington area, to assess symptomatic relief and overall quality of life before and after surgery. To also review xrays of this population to assess acetabular component orientation. Fifty patients from two hospitals, with minimum follow up of two years, who had SSBTHJR, were reviewed for duration of stay, time to mobilisation, and complications (eg. wound infections, venous thrombus and embolism (VTE), gastrointestinal ileus, and cardiac events). Patient opinions on hip joint function (Oxford Hip Score) and overall quality of life (EQ-5D Score) were performed (37/50 patients could participate). Patient’s postoperative radiographs were analysed with Polyware Auto Version 6.00 to measure
Surgical navigation, coupled with preoperative plans, allows surgeons to plan and execute procedures to improve the likelihood of positive outcomes. In real life these navigation systems, which track both the patient and the surgical tools, are not absolutely accurate. Therefore, there is a need to know how much error there may be in the navigation system, so that the surgeon can assess the effects of possible errors in positioning. The methodology for assessing the accuracy of a surgical navigation system is similar across surgical specialties. We developed a framework for assessing the accuracy of the HipNav system, a computer assisted surgical system used for planning and intra-operative surgical navigation for total hip arthroplasty. This framework can be adapted to other systems and surgical procedures. To assess navigational accuracy, we compared acquired values to a ground-truth model: rigid plastic Sawbones pelvii with mounted fiducials and acetabular implants, whose positions were measured with a coordinate measuring machine. We then identified the individual components of the system that can contribute to overall accuracy, and characterised their contributions to the accuracy of the system. We also measured the end-to-end accuracy of the HipNav system, from initial CT scan through to
Introduction: Edge-loading, a phenomenon whereby the femoral component comes into contact with the edge of the acetabular component, has been suggested to increase wear in metal-on-metal hip resurfacing arthroplasty (MoMHRA). Pseudotumours (soft-tissue mass relating to the hip joint) have been associated with elevated serum and hip aspirate metal ion levels. This study aimed to investigate in vivo edge-loading in MoMHRA patients with pseudotumours by quantifying dynamic loci of the hip joint segment force relative to the acetabular component during functional activities. Materials and Methods: A total of 21 MoMHRA patients (30 hips) in two groups were investigated in this Ethics approved study:. 6 patients with pseudo-tumours detected using ultrasound/MRI;. 15 patients without pseudotumours. Three-dimensional lower limb motion analysis (12 camera Vicon System) was performed to estimate hip joint segment force during walking, chair-rising and stair-climbing. CT scans were used to determine each patient’s specific hip joint centre and acetabular component orientation. Edge-loading was defined to occur when a hip joint segment force vector/ cup intersection was located within 10% of the cup radius from the edge of the cup. Serum cobalt and chromium levels were analysed using Inductively-Coupled Plasma Spectrometer. Results: Edge-loading in the pseudotumour group occurred with significantly (p=0.02) longer (4-fold increase) duration as well as greater magnitude (7-fold increase) of force, compared to the non-pseudotumour group. The duration and force of the edge-loading were activity-dependent, with proportionally greater difference observed during stair climbing. The
There is increasing interest in the use of image free computer assisted surgery (CAS) in total hip arthroplasty (THA). Many of these systems require the registration of the Anterior Pelvic Plane (APP) via the bony landmarks of the anterior superior iliac spines (ASIS) and pubic tubercles (PT) in order to accurately orient the acetabular cup in terms of anteversion and inclination. Given system accuracies are within 1mm and 1° and clinical validation studies have given accuracy by cup position. However, clinical outcomes contain not only system inaccuracies but also variations due to clinical practice. To understand the effects of variation in landmark acquisition on the identification of the
Introduction:. Wear, wear-associated osteolysis, and instability are the most common reasons for revision total hip arthroplasty. These failures have been shown to be associated with acetabular component malpositioning. However, optimal acetabular component orientation on a patient-specific basis is currently unknown. The current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips. Methods:. Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 99 hips in 93 patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the
Introduction. The optimal acetabular component orientation in general or on a patient-specific basis is currently unknown. In order to answer this question, the current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips. Methods. Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 101 hips in patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the