Cup Position Research Articles

Evaluating Alternative Registration Planes in Imageless, Computer-Assisted Navigation Systems for Direct Anterior Total Hip Arthroplasty.

(1) Background: Imageless computer navigation systems have the potential to improve the accuracy of acetabular cup position in total hip arthroplasty (THA). Popular imageless navigation methods include locating the patient in a three-dimensional space (registration method) while using a baseline to angle the acetabular cup (reference plane). This study aims to compare the accuracy of different methods for determining postoperative acetabular cup positioning in THA via the direct anterior approach. (2) Methods: Fifty-one participants were recruited. Optical and inertial sensor imageless navigation systems were used simultaneously with three combinations of registration methods and reference planes: the anterior pelvic plane (APP), the anterior superior iliac spine (ASIS) and the table tilt (TT) method. Postoperative acetabular cup position, inclination, and anteversion were assessed using CT scans. (3) Results: For inclination, the mean absolute error (MAE) was lower using the TT method (2.4° ± 1.7°) compared to the ASIS (2.8° ± 1.7°, p = 0.17) and APP method (3.7° ± 2.1°, p < 0.001). For anteversion, the MAE was significantly lower for the TT method (2.4° ± 1.8°) in contrast to the ASIS (3.9° ± 3.2°, p = 0.005) and APP method (9.1° ± 6.2°, p < 0.001). (4) Conclusion: A functional reference plane is superior to an anatomic reference plane to accurately measure intraoperative acetabular cup inclination and anteversion in THA using inertial imageless navigation systems.

Does the utilization of fluoroscopy affect the accuracy of prosthesis position in patients undergoing hip replacement surgery via the direct anterior approach compared to the posterolateral approach for an experienced surgeon? A single-center retrospective study

BackgroundThe direct anterior approach (DAA) for total hip arthroplasty (THA) has gained popularity due to perceived advantages in achieving better early outcomes. However, the theoretical benefits such as precise implant positioning and accurate leg length restoration are still inconsistent. In this study, we compared implant position and leg length discrepancy (LLD) of the DAA and posterolateral approach (PLA) conducted by a single surgeon who had mastered both approaches.MethodsThis study retrospectively reviewed the medical records and radiographic images of 244 patients who underwent THA between 2012 and 2021 by a single experienced surgeon using either the DAA (n = 120) or PLA (n = 124). Postoperative pelvic anteroposterior radiographs at 6 months follow-up were used to assess acetabular component inclination and anteversion, as well as LLD. Mann-Whitney U tests and Chi-squared test were performed to compare outcomes between the two approaches.ResultsNo significant differences were observed in patient demographics between the two groups. The DAA group demonstrated significantly lower postoperative LLD (0.00 mm) compared to the PLA group (5.00 mm, p < 0.0001). No significant difference was observed in the Lewinnek zone for cup anteversion and inclination angles between the two groups.ConclusionsFor experienced surgeons in other approaches, our findings suggest transferring to the DAA may not substantially improve cup positioning, but it might slightly enhance limb length measurement. For surgeons already proficient in other approaches and deciding to maintain those approaches, their primary concern for optimal THA outcome should be striving for leg length equivalence.

Accuracy of robotic arm-assisted versus computed tomography-based navigation in total hip arthroplasty using the direct anterior approach: a retrospective study

BackgroundA robotic arm-assisted and a computed tomography (CT)- based navigation system have been reported to improve the accuracy of component positioning in total hip arthroplasty (THA). However, no study has compared robotic arm-assisted THA (rTHA) to CT-based navigated THA (nTHA) concerning accuracy of cup placement and acetabular fractures using the direct anterior approach (DAA). This study aimed to compare the accuracy of cup placement and the presence of intraoperative acetabular fractures between rTHA and nTHA using DAA in the supine position.MethodsWe retrospectively investigated 209 hips of 188 patients who underwent rTHA or nTHA using DAA (rTHA using the Mako system: 85 hips of 79 patients; nTHA: 124 hips of 109 patients). After propensity score matching for age and sex, each group consisted of 73 hips. We evaluated clinical and radiographic outcomes, comparing postoperative cup orientation and position, measured using a three-dimensional templating software, to preoperative CT planning. Additionally, we investigated the prevalence of occult acetabular fracture.ResultsClinical outcomes were not significantly different between the groups at 1 year postoperatively. The mean absolute error of cup orientation was significantly smaller in the rTHA group than in nTHA (inclination: 1.4° ± 1.2° vs. 2.7° ± 2.2°, respectively; p = 0.0001, anteversion: 1.5° ± 1.3° vs. 2.2° ± 1.7°, respectively; p = 0.007). The cases within an absolute error of 5 degrees in both RI and RA were significantly higher in the rTHA (97.3%) than in nTHA group (82.2%) (p = 0.003). The absolute error of the cup position was not significantly different between the two groups. The prevalence of occult acetabular fracture did not differ significantly between the two groups (rTHA: n = 0 [0%] vs. nTHA: n = 1 [1.4%]).ConclusionCup placement using DAA in the supine position in rTHA was more accurate with fewer outliers compared to nTHA. Therefore, rTHA performed via DAA in a supine position would be useful for accurate cup placement.

Precision of Cup Positioning Using a Novel Computed Tomography Based Navigation System in Total Hip Arthroplasty

Background and Objectives: Navigation systems are designed to enhance surgical precision, improving patient outcomes and reducing the risk of implant misplacement. In this study, we have evaluated a novel orthopedic surgical platform that utilizes CT imaging with AI-based algorithms to automate several critical aspects of total hip arthroplasty. It contains three modules—preoperative planning, navigation during surgery, and follow-up analysis. The primary objective of the current study was to evaluate the precision of the navigation tool in cup placement, i.e., whether the information displayed for navigation correctly reflected the actual position of the implant. Materials and Methods: Surgery outcomes of 15 inter-rater measurements on human cadavers and 18 surgeries on patients who underwent total hip replacement using the navigation tool were analyzed. Results: In the inter-rater assessment, the mean errors were −0.31 ± 1.42° for anteversion, 1.06 ± 1.73° for inclination, and −0.94 ± 1.76 mm for cup position depth. In patients’ surgeries, the mean errors were −0.07 ± 2.72° for anteversion, −0.2 ± 0.86° for inclination, and 0.28 ± 0.78 mm for cup depth. Conclusions: The navigation tool offers intra-operative guidance on notable precision in cup placement, thereby effectively mitigating the risk of cup malpositioning outside the patient-specific safe zone.

Assessment of Cup Placement Impact on Functional Outcomes in Total Hip Replacement: A Retrospective Analysis of 20 Patients

Introduction:Total hip replacement surgery is gaining popularity as a treatment for hip disorders, replacing alternative treatments like excisional arthroplasty, osteotomy, arthrodesis, and hemiarthroplasty. This research aims to evaluate the effect of the acetabular cup on functional outcomes, particularly in younger patients with hip arthritis and femur neck fractures.Materials And Methods:This study aimed to evaluate the placement of the acetabular cup and its association with functional outcomes in total hip replacement (THR). 20 patients were randomly selected from the MRD department and underwent pelvic CT scans postoperatively. Functional results have been analyzed using the Harris Hip Score. The acceptable cup version range was 15 ± 10 degrees, and patients outside this range were closely examined for rotational movements. Results: A study of 20 patients with a neck or femur fracture found that 11 patients had a right knee injury, while 9 had a left knee injury. After a year postoperatively, 18 patients reported no pain, while 2 had mild pain. Functional assessment depicted better outcomes in 17 patients, good outcomes in 2 patients, and fair outcomes in 1 patient. Radiological analysis revealed a mean cup version of 17.77 degrees, with complications including one dislocation and three limb length discrepancies. None of the patients developed an infection.Conclusion:The study found that 90% of patients had excellent functional outcomes, with only 10% exhibiting excessive anteversion. CT scan-based measurements of cup placement provided reliable predictions, consistent with intraoperative assessment of cup positioning.

Change of Sacral Slope according to the Surgical Position in Total Hip Arthroplasty.

Pelvis tilting in sagittal plane influences the acetabular cup position. Majority of total hip arthroplasty (THA) are performed in lateral decubitus surgical position. This study is to assess whether there is any difference in sacral slope between standing and lateral decubitus position and influence of this variation in planning acetabular cup anteversion. This is a prospective study including 50 patients operated between January 2020 to March 2022. Preoperative radiograph included lumbosacral spine lateral X-ray in standing, supine and lateral decubitus positions to calculate the sacral slope for assessment of anterior or posterior pelvic tilting. In our study, we determined the position of the acetabular cup based on changes in sacral slope between standing and lateral decubitus postures. For patients whose sacral slope increased from lateral decubitus to standing, we implanted the acetabular component with a higher degree of anteversion. Conversely, for patients with reverse phenomenon, the cup was inserted at lower anteversion. Twenty-four patients (48.0%) had increase in sacral slope from lateral decubitus to standing whereas 26 patients (52.0%) had decrease in sacral slope. There was linear correlation between difference in preoperative sacral slope and postoperative cross table lateral cup anteversion. Harris hip scores improved from 40.78 to 85.43. There was no subluxation or dislocation in any patient at minimum 2-year follow-up. Individualized acetabular cup placement is important for better functional outcome in THA. Evaluation of pelvic tilting in lateral decubitus position is necessary for better positioning of acetabular cup and avoid postoperative complications.

Analysis of trapeziometacarpal prosthesis cup position with respect to the trapezial anatomy.

The purpose of this study was to analyse the anatomy of the trapezium with regard to cup position in trapeziometacarpal replacement and identify those trapeziums that are at risk of cup perforation through the trapezoid articular surface. The width of the proximal and distal articular surface and the height of the trapezium and second metacarpal facet were measured on 96 peritrapezial views reconstructed from computed tomography scans. The trapezoid articular surface of the trapezium (TRAST) angle was calculated, and four different cup designs were virtually positioned centrally in the trapezium and parallel to the proximal articular surface. Risk of perforation was defined as a cup that exceeds the ulnar border of the proximal articular surface. The mean TRAST angle in our study was 33°. Risk of perforation is higher when the second metacarpal facet is smaller than 5 mm and when the TRAST angle is 35° or more. In these cases, the position of the cup should be more radial or more distal.

Optimasi Human Error pada Proses Produksi Air Minum Dalam Kemasan di PT. Telaga Tanjung Pomosda Nganjuk

PT. Telaga Tanjung Pomosda, a bottled mineral water manufacturer in Nganjuk, East Java, faces challenges in maintaining high production standards and addressing operational issues such as product rejection and production process errors, impacting overall company efficiency and reputation. This study identifies operational error factors and evaluates the effectiveness of improvement methods. Research procedures utilize HTA, SHERPA, and Poka-Yoke to identify and reduce human errors in bottled mineral water production at PT. Telaga Tanjung Pomosda Nganjuk, focusing on error analysis, probability assessment, and Poka-Yoke strategy implementation. The bottled water packaging process involves critical stages such as cup packaging, pressing, and packing. Errors in each stage can result in delays, decreased water volume, imperfectly pressed lids, and packing mistakes, hindering the entire production process. Research at PT. Telaga Tanjung Pomosda identifies operator issues in machine settings, water measurement, lid positioning, task interruptions, packaging, and cup positioning, with solutions including routine checks and training to enhance product quality

Midterm Results of Severe Hip Dysplasia after Using a Cementless Acetabular Component with Bulk Bone Graft in Total Hip Arthroplasty: A Minimum Five-Year Follow-Up Study.

In patients with severe hip dysplasia, total hip arthroplasty (THA) using bulk bone graft (BBG) enhances anatomic cup positioning and provides early structural support. This study assesses the mid-term outcomes of THA with BBG in patients with over 50% graft bone coverage. Among 1951 patients who underwent THA between 2003 and 2007, 183 had BBG. After excluding early dropouts and infections, 151 patients remained. They were classified into uncovered (<50% coverage, 79 patients) and covered (>50% coverage, 72 patients) groups. The efficacy of cup fixation was compared between these groups. After ten years, the survival rate for not needing THA revision was 98% in the uncovered group and 100% in the covered group, while the rate for radiographic stability was 93% versus 99%, respectively. Although the cutoff value for the uncovered portion could not be clarified in this study, the mid-term results for 50% to approximately 70% uncovered were comparable to those for 50% or lesser, which have previously been expected to perform well. Recently, biomechanically advantageous bone grafting techniques have been identified, and based on the results of this study, it may be possible to expand the indications for THA with bone grafting for developmental dysplasia of the hip.

A PROSPECTIVE RANDOMIZED CONTROLLED TRIAL COMPARING THE DIRECT SUPERIOR APPROACH WITH THE POSTERIOR APPROACH FOR TOTAL HIP ARTHROPLASTY

The direct superior approach (DSA) is a modification of the posterior approach (PA) that preserves the iliotibial band and short external rotators except for the piriformis or conjoined tendon during total hip arthroplasty (THA). The objective of this study was to compare postoperative pain, early functional rehabilitation, functional outcomes, implant positioning, implant migration, and complications in patients undergoing the DSA versus PA for THA.This study included 80 patients with symptomatic hip arthritis undergoing primary THA. Patients were prospectively randomised to receive either the DSA or PA for THA, surgery was undertaken using identical implant designs in both groups, and all patients received a standardized postoperative rehabilitation programme. Predefined study outcomes were recorded by blinded observers at regular intervals for two-years after THA. Radiosteriometric analysis (RSA) was used to assess implant migration.There were no statistical differences between the DSA and PA in postoperative pain scores (p=0.312), opiate analgesia consumption (p=0.067), and time to hospital discharge (p=0.416). At two years follow-up, both groups had comparable Oxford hip scores (p=0.476); Harris hip scores (p=0.293); Hip disability and osteoarthritis outcome scores (p=0.543); University of California at Los Angeles scores (p=0.609); Western Ontario and McMaster Universities Arthritis Index (p=0.833); and European Quality of Life questionnaire with 5 dimensions scores (p=0.418). Radiographic analysis revealed no difference between the two treatment groups for overall accuracy of acetabular cup positioning (p=0.687) and femoral stem alignment (p=0.564). RSA revealed no difference in femoral component migration (p=0.145) between the groups at two years follow-up.There were no differences between patients undergoing the DSA versus PA for THA with respect to postoperative pain scores, functional rehabilitation, patient-reported outcome measurements, accuracy of implant positioning, and implant migration at two years follow-up. Both treatment groups had excellent outcomes that remained comparable at all follow-up intervals.

Archetype analysis of the spine-hip relationship identifies distinct spinopelvic profiles

IntroductionThe position of the pelvis in the sagittal plane can vary considerably between different functional positions. Adapting the position of the acetabular cup in relation to the alignment between the spine and the hip of each individual, prior to prosthesis placement, can prevent the risk of prosthetic impingement. Taken individually, risk factors for unfavorable spinopelvic kinematics can be difficult to interpret when trying to precisely predict which patients are at risk. Furthermore, the use of classifications or algorithms can be complex, most often associated with limited values and often difficult to apply in current practices of risk assessment. HypothesisWe hypothesized that the deconstruction of the data matrix including age and spinopelvic parameters (SPT, LL, PI, LF and PI-LL) correlated with the analysis of spinopelvic kinematics could be used to define an individualized hip-spine relationship. Material and methodWe applied archetypal analysis, which is a probabilistic, data-driven and unsupervised approach, to a complete phenotype cohort of 330 patients before total hip arthroplasty to define the spinopelvic profile of each individual using the spinopelvic parameters without threshold value. For each archetype, we analyzed the spinopelvic kinematics, not implemented in the creation of the archetypes. ResultsAn unsupervised learning method revealed seven archetypes with distinct spinopelvic kinematic profiles ranging from −8.9 ° to 13.15 ° (p = 0.0001) from standing to sitting and −5. 35 ° to −10.81 ° (p = 0.0001) from supine to standing. Archetype 1 represents the “ideal” patient (A1); young patients without spinopelvic anomaly and the least at risk of mobility anomaly. Followed by 3 archetypes without sagittal imbalance according to their lumbar lordosis and pelvic incidence, from the highest to the lowest (archetypes 2–4), archetype 4 exposing a greater risk of spinopelvic kinematic anomaly compared to others. Then 2 archetypes with sagittal imbalance: archetype 5, with an immobile pelvis in the horizontal plane from standing to sitting position in anterior tilt and archetype A6, with significant posterior pelvic tilt standing, likely compensating for the imbalance and associated with the greatest anomaly of spinopelvic kinematics. Finally, archetype 7 with the stiffest lumbar spine without sagittal imbalance and significant unfavorable kinematics from standing to sitting. ConclusionAn archetypal approach to patients before hip replacement can refine diagnostic and prognostic features associated with the hip-spine relationship and reduced heterogeneity, thereby improving spinopelvic characterization. This risk stratification of spinopelvic kinematic abnormalities could make it possible to target patients who require adapted positioning or types of implants before prosthetic surgery. Level of evidenceIV retrospective study.

Intraoperative application of three-dimensional printed guides in total hip arthroplasty: A systematic review.

Acetabular component positioning in total hip arthroplasty (THA) is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications. The majority of acetabular components are aligned freehand, without the use of navigation methods. Patient specific instruments (PSI) and three-dimensional (3D) printing of THA placement guides are increasingly used in primary THA to ensure optimal positioning. To summarize the literature on 3D printing in THA and how they improve acetabular component alignment. PubMed was used to identify and access scientific studies reporting on different 3D printing methods used in THA. Eight studies with 236 hips in 228 patients were included. The studies could be divided into two main categories; 3D printed models and 3D printed guides. 3D printing in THA helped improve preoperative cup size planning and post-operative Harris hip scores between intervention and control groups (P = 0.019, P = 0.009). Otherwise, outcome measures were heterogeneous and thus difficult to compare. The overarching consensus between the studies is that the use of 3D guidance tools can assist in improving THA cup positioning and reduce the need for revision THA and the associated costs. The implementation of 3D printing and PSI for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning.

Assessment of BFX cup version in a three-dimensional model simulating the ventrodorsal radiographic view.

To measure truncated face and open face versions of the biological fixation (BFX) cup in a three-dimensional (3D) model simulating the ventrodorsal radiographic projection with different cup and pelvis positions. Computer simulation. Simulated ventrodorsal views were generated in silico using 3D models of a BFX cup and a medium-sized canine pelvis. Truncated face and open face versions of the BFX cup were defined and measured with various angles of cup version, cup inclination, and pelvic extension. Truncated face version was different from and underestimated open face version by 12° to 22° (p < .001). Open face version varied with inclination while truncated face version was unaffected by inclination. Open face version was dependent on the degree of pelvic extension while truncated face version was unaffected. Open face version differed from truncated face version. Changes in open face version were not consistently matched by a change in truncated face version. The open face of the cup may be excessively retroverted without this being reflected by truncated face retroversion as seen on a ventrodorsal radiographic view. However, in this study, BFX cups placed with truncated face version and inclination in the normal range and an ALO of 45° yielded predictable open face version.

Anterior-approach total hip arthroplasty in patients with poliomyelitis: Long-term outcomes

ObjectiveIn patients with residual poliomyelitis-related impairments, total hip arthroplasty (THA) is challenging due to the high frequency of risk factors such as hip dysplasia, dislocation, muscle weakness, and fracture. The objective of this study was to assess the long-term functional and radiographic outcomes of anterior-approach THA with a ceramic-ceramic, dual-mobility, or constrained implant in patients with poliomyelitis sequelae. HypothesisTHA via the anterior approach with a ceramic-ceramic, dual-mobility, or constrained implant is a reliable technique that is not associated with excess risks of instability or aseptic loosening. Material and methodsThis single-centre retrospective study included consecutive patients with poliomyelitis sequelae who underwent THA between January 1998 and September 2019 via the anterior approach, with implantation of a ceramic-ceramic, dual-mobility, or constrained implant. The Harris Hip Score (HHS), implant position, and complications (e.g., infection and loosening) were collected during the most recent in-person visit. ResultsThe study included 19 patients (23 hips). Mean follow-up was 5.2 ± 4.2 years (range, 2.0–10.6 years). Only six of the 23 procedures were done on the side with greater muscle weakness. The mean HHS at last follow-up was 80.4 ± 10.4. A single procedure (1/23, 4%) was followed by a complication, consisting in intra-prosthetic dislocation 2 years after implantation of a dual-mobility cup. At last follow-up, the HHS was not associated with psoas and gluteus muscle strength (rs = 0.35, p = 0.11 and rs = 0.37, p = 0.09, respectively) and was not significantly different between the weaker vs. stronger side (82.7 ± 8.0 vs. 79.5 ± 11.3, respectively; p = 0.53). Cup position was more horizontal, thereby optimising function, when the procedure was done on the weaker vs. the stronger side (39.9° ± 4.3 vs. 45.0° ± 6.8, respectively; p = 0.02). ConclusionTHA is a good option for improving function in patients with poliomyelitis sequelae. THA via the anterior approach with a ceramic-ceramic, dual-mobility, or constrained implant is a reliable method that is not associated with an excess risk of instability or loosening. Level of evidenceIV.

Current Concepts and Technologies in Acetabular Cup Positioning for Primary Total Hip Arthroplasty

Current Concepts and Technologies in Acetabular Cup Positioning for Primary Total Hip Arthroplasty

A multicentre prospective assessment of the utility of robotic assisted total hip arthroplasty with virtual range of motion on intraoperative implant positioning.

The growing adoption of robotic-assistance during total hip arthroplasty (THA) has provided novel means through which a patient's anatomy and dynamic spinopelvic relationship can be incorporated into surgical planning. However, the impact of enhanced technologies on intraoperative decision-making and changes to component positioning has not yet been described. A multicentre, prospective study included 105 patients (52% women) patients who underwent robotic-assisted THA with the integration of software that incorporates a patient's pelvic tilt (PT) and virtual range-of-motion (VROM) for impingement modeling. The primary outcome of the study was the percentage of patients who underwent changes to the preoperative plan for cup position after incorporating the data from the software. Utilising the intraoperative VROM information, the preoperative plan for cup position was changed from the default (40° inclination and 20° anteversion) in 82/105 (78%) cases. When stratifying by spinopelvic mobility, 64% were considered normal (change ⩾ 10° and ⩽30°), 27% were stiff (change < 10°), and 9% were hypermobile (change > 30°). For all cohorts, the majority of cases (78%) deviated from the 40° inclination and 20° version target. When evaluating the proportion of cases within the Lewinnek and Callanan safe zones based on spinopelvic mobility, 19% of cases within the normal group were planned outside of both zones compared to 39% of stiff cases and 10% of hypermobile cases. Utilising the latest version of robotic-assisted THA software, the preoperative plan for cup position was changed in the vast majority (78%) of patients, causing substantial deviations from traditional, generic cup targets.

Accuracy of acetabular cup placement in total hip arthroplasty using an augmented reality navigation “pin-less” system: A pilot study

PurposeCurrently, there is limited information regarding the utilization of pin-less augmented reality (AR) assistance in total hip arthroplasty (THA). This preliminary study aimed to evaluate the precision of acetabular cup placement in THA utilizing the AR Navigation “Pin-less” System (Pin-less AR navigation, prototype). MethodsA total of 72 consecutive primary THAs in 58 patients were categorized into two groups: the Pin-less AR navigation group and the conventional group. All THAs were conducted via the direct anterior approach. First, the absolute value of difference between the intra-operative and post-operative angles (absolute difference) was calculated in the Pin-less AR navigation group. Second, the absolute value of error between the post-operative angles and the target angles (absolute target error) was assessed both in the Pin-less AR navigation group and the conventional group. ResultsThe absolute difference in inclination and anteversion angles was 2.2 ​± ​1.4° and 2.4 ​± ​1.5°, respectively. The absolute target error in the Pin-less AR navigation group versus the conventional group was 1.9 ​± ​1.5° versus 4.2 ​± ​2.7° in inclination (P ​< ​0.001) and 2.3 ​± ​1.5° versus 3.1 ​± ​2.1° in anteversion (P ​= ​0.092). The percentage of acetabular cups placed within ±5° from the target angles was significantly higher in the Pin-less AR navigation group (90.3%) compared with the conventional group (52.6%) (P ​< ​0.001). ConclusionsThis study demonstrates that Pin-less AR navigation yielded generally accurate acetabular cup positioning, surpassing the conventional method. Further research is warranted to thoroughly evaluate Pin-less AR navigation.

A new novel recognition and positioning system of black light-absorbing volute for automation depalletizing development

Abstract In the application of vision measurement, the black light-absorbing object is difficult to reflect the structured light from infrared emitter of the RGB-D camera. Therefore, an image recognition algorithm based on reference environment information is proposed to acquire the spatial positioning information of black volutes in the depalletizing system. The hardware system of the depalletizing system is mainly constructed of an upper computer, a six-axis industrial robot, an RGB-D camera and an end adsorption device. Firstly, the horizontal position information of each volute placed on the cardboard is obtained by the depth differences between the cardboard and the volute. Then, the depth information of the volute is obtained by the upper cardboard depth through collecting the position of the end vacuum suction cup triggered by feedback signal from vacuum generator. Secondly, a regional planar hand-eye calibration method is developed to improve the calibration accuracy in two-dimensional coordinates. The regional calibration method divides the robot working area into four regions: upper left, lower left, upper right, and lower right. The transformation matrix of each region is calculated separately. Finally, the depalletizing experiment is conducted on the three types of volutes. It is concluded that the average positioning error of the grasping center point of each volute obtained by our method is 3.795 mm, and its standard deviation is 1.769 mm. The average value of regional planar hand-eye calibration error is 4.044 mm, and its standard deviation is 1.501 mm. Under a stack of materials with dimensions of 1350 mm × 1350 mm × 1500 mm, the maximum error is controlled within 15 mm. Additionally, when combined with the end feedback compensation mechanism, the success rate for grasping all three volutes reaches 100%.

Cup Placement in Thumb Carpometacarpal Joint Prostheses: The Role of the Guidewire

The increasing use of thumb carpometacarpal joint prostheses for advanced CMC 1 (carpometacarpal) joint arthritis reflects the success of the latest prosthesis generations, which has been achieved through their improved functional outcomes and lower complication rates. Precise alignment of the prosthesis cup parallel to the proximal joint surface of the trapezium is essential for stability and the prevention of dislocation. This is a challenging surgical step, particularly for surgeons new to this technique. Despite adequate positioning of the guidewire, misplacements of the cup may occur, necessitating intraoperative revision. This study examined the deviations in cup and guidewire positioning in thumb carpometacarpal joint prosthesis implantations by inexperienced and experienced surgeons through radiological analysis of 65 prostheses. Both inexperienced and experienced surgeons achieved precise guidewire positioning with mean deviations of<2.2°. Inexperienced surgeons showed significantly larger cup deviations in the dorsopalmar and lateral view (7.6±6.1° and 7.3±5.9°) compared with experienced surgeons (3.6±2.7° and 3.6±2.5°; p=0.012, p=0.017). The deviation of the cup position exhibited by inexperienced surgeons tends to be in the direction opposite to the initial guidewire position (p<0.0038). The results highlight the current challenges in cup positioning depending on a surgeon's level of experience, questioning the reliability of the current guidewire placement.

A GEOMETRIC MODEL OF IMPINGEMENT DURING DISLOCATION-PRONE ACTIVITIES IN DUAL-MOBILITY AND STANDARD ACETABULAR CUPS

Dual Mobility (DM) Total Hip Replacements (THRs), are becoming widely used but function in-vivo is not fully understood.The aim of this study was to compare the incidence of impingement of a modular dual mobility with that of a standard cup.A geometrical model of one subject's bony anatomy \[1\] was developed, a THR was implanted with the cup at a range of inclination and anteversion positions (Corail® stem, Pinnacle® cup (DePuy Synthes)). Two DM variants and one STD acetabular cup were modelled. Joint motions were taken from kinematic data of activities of daily living associated with dislocation \[2\] and walking. The occurrence of impingement was assessed for each component combination, orientation and activity. Implant-implant impingement can occur between the femoral neck and the metal or PE liner (DM or STD constructs respectively) or neck-PE mobile liner (DM only).The results comprise a colour coded matrix which sums the number of impingement events for each cup position and activity and for each implant variant.Neck-PE mobile liner impingement, occurred for both DM sizes, for all activities, and most cup placement positions indicating that the PE mobile liner is likely to move at the start of all activities including walking.For all constructs no placement positions avoided neck-metal (DM) or neck-PE liner (STD) impingementevents in all activities. The least number of events occurred at higher inclination and anteversion component positions. In addition to implant-implant impingement, some instances of bone-bone and implant-bone impingement were also observed.Consistent with DM philosophy, neck-PE mobile liner impingement and liner motion occurred for all activities including walking. Neck-liner impingement frequency was comparable between both DM sizes (metal liner) and a standard cup (PE liner).