Use of augmented reality surgical navigation reduces intraoperative fluoroscopic imaging in anterior total hip arthroplasty with equivalent accuracy for component positioning

Background

Computer-assisted surgical navigation was designed to reduce the rates of acetabular component malpositioning, a common cause for revision following primary total hip arthroplasty (THA). We compared intraoperative measures such as radiation exposure, radiographic acetabular cup placement, and outcomes of patients who underwent a THA using computer-assisted surgical navigation with augmented reality (AR) compared to those who underwent traditional manual THA with fluoroscopic assistance (FA).

Methods

We retrospectively reviewed 115 hips who underwent primary direct anterior THAs using the intraoperative AR surgical navigation system between 3/30/2021 and 12/30/2022. These were compared to a matched cohort of 115 primary THAs performed with FA through a direct anterior approach during the same time period. Patients were matched based on age, gender, American Society of Anesthesiologists score (ASA), and BMI. Goal inclination and anteversion were set to 42° (°) and 22°, respectively.

Results

THA with AR patients had decreased intraoperative radiation exposure (mean 2.0 versus 3.2 mGy, p < 0.001) and radiation time (mean 0.2 versus 0.4 min, p < 0.001). Deviation from the preoperative plan was similar between AR and FA for both radiographic inclination and anteversion. There was no difference in the operative time, estimated blood loss, or reoperations, all of which were for infection (1.7 versus 0.0 %, p = 0.5).

Conclusion

AR surgical navigation in primary THA has similar radiographic, operative and clinical results as THA with intraoperative FA. However, AR surgical navigation is associated with decreased intraoperative fluoroscopic radiation and time. Further research is needed to evaluate accuracy of acetabular component positioning and complications.

Dislocation incidence and risk factors following direct anterior primary total hip arthroplasty: a consecutive, single-surgeon cohort

BACKGROUNDS

Dislocation is one of the debilitating complications of total hip arthroplasty. It is a common reason for revision surgery after THA, along with other complications such as infection and instability. This study determined the incidence and risk factors of dislocation after primary total hip arthroplasty using the direct anterior approach.

METHODS

Retrospective Data from patients who underwent primary THA from 2013 to 2020 was analyzed. Anteversion and inclination angles were extracted from their imaging studies, and demographic data were also recorded from their medical records. Data were analyzed using SPSS version 26.

RESULTS

One thousand two hundred four cases of THA were reviewed in our study. 31 (2.57%) dislocations happened after a minimum follow-up of five years. Our study showed that DDH diagnosis as the underlying condition, using Wagner Cone and Wagner SL stem, cup size smaller than 52, head size smaller than 34, anteversion and inclination angle outside the Lewinnek safe zone can be risk factors for dislocation. Primary OA and Fitmore stem acted as protective factors for dislocation.

CONCLUSION

In the DA approach, the underlying disease, properties of the prosthesis used such as cup and head size, stem type, and anteversion and inclination angles can be the potential risk factors for dislocation.

LEVEL OF EVIDENCE

III.

Influence of highly cross-linked polyethylene manufacturing characteristics on femoral head penetration in total hip arthroplasty : a ten- to 22-year follow-up study

Aims

Highly cross-linked polyethylene (HXLPE) has reduced wear and revision rates in total hip arthroplasty (THA) in the long term. However, the effect of HXLPE manufacturing characteristics on femoral head penetration has not yet been clearly defined. We report this single-institution study to investigate the clinical and radiological results of various HXLPE liners in THA.

Methods

Between January 2001 and December 2013, 904 uncemented THAs using HXLPE liners were performed at our institution. Seven different HXLPE liner types were identified: remelted (n = 3), annealed (n = 2), sequentially annealed (n = 1), and vitamin E diffused (n = 1). A total of 746 hips were available for a minimum follow-up of ten years. The linear femoral head penetration rate was measured at six weeks and at one, five, ten, and 15 years, applying the Dorr criteria to digitized radiographs, using the Roman v. 1 70 software package for analysis.

Results

No patient was revised due to wear or osteolysis. The mean total femoral head penetration ten years after THA ranged from 0.14 mm (SD 0.06) to 0.20 mm (SD 0.17) for all groups (p = 0.649). Femoral head penetration > 0.40 mm at ten years was observed in 27 (3.6%) hips. From one to 15 years after surgery, mean total penetration was 0.21 mm (SD 0.13) in components with an acetabular inclination > 50° and 0.10 mm (SD 0.12) in those placed between 35° and 50° (p < 0.001). The radiological analysis did not detect osteolysis in any hip.

Conclusion

Although HXLPE characteristics can result in different wear performance in patients undergoing THA at a mean follow-up of 15 years, the clinical and radiological results were excellent in all groups. The position of the acetabular component can influence the femoral head penetration of modern HXLPEs.

The use of porous titanium acetabular augments in primary total hip arthroplasty for hip dysplasia or rapidly destructive coxopathy

Aims

This study aimed to evaluate the efficacy of porous titanium acetabular augments in primary total hip arthroplasty (THA) for reconstruction of superolateral acetabular bone defects in patients with Crowe II or higher classes of developmental dysplasia of the hip (DDH) or rapidly destructive coxopathy (RDC).

Methods

We conducted a retrospective evaluation of 27 patients (30 hips) who underwent primary THA using cementless cups and porous titanium acetabular augments. The follow-up periods ranged from two to 11 years, with a mean of 5.0 years. The cohort included 22 females (24 hips) and five males (six hips), with a mean age of 67 years (45 to 83) at the time of surgery.

Results

At the final follow-up, there was no radiological evidence of loosening or radiolucency around the cups and augments, indicating successful biological fixation in all cases. Clinically, there was a significant improvement in the Western Ontario and McMaster Universities Osteoarthritis Index score, which improved from a mean of 39.1 (SD 14.7) preoperatively to 5.1 (SD 6.4) postoperatively.

Conclusion

The use of cementless cups and porous acetabular titanium augments in primary THA for patients with DDH and RDC can lead to considerable clinical improvements and reliable biological fixation, suggesting their potential as a viable solution for managing challenging acetabular defects in these conditions.

Imaging study of aseptic loosening of the acetabular cup after cementless total hip arthroplasty: a retrospective study

PURPOSE

The purpose of this study was to provide more accurate imaging diagnostic parameters for acetabular cup loosening through radiological characteristic of acetabular cup aseptic loosening after cementless total hip arthroplasty, especially for patients lacking postoperative baseline or serial follow-up radiographs.

METHODS

The radiographic data of patients who underwent primary unilateral cementless total hip arthroplasty in our hospital from January 2017 to July 2024 were retrospectively studied. Forty-one patients with aseptic loosening of the acetabular cup, confirmed by surgery or consensus between clinicians and radiologists, were included in the loosening group. Sixty-one patients who underwent primary total hip arthroplasty and were evaluated more than one year postoperatively were included as the control group. The absence of postoperative complications was confirmed through discussions between clinicians and radiologists. Radiographic examination of the contralateral hip joint in all included patients showed no significant abnormalities. The following imaging parameters were measured on anteroposterior bilateral hip radiography: acetabular cup inclination (AA), acetabular difference in vertical distance 1 (DVD1), acetabular difference in vertical distance 2 (DVD2), acetabular difference in horizontal distance (DHD), wide radiolucent zones around the acetabular cup (TA), number of wide radiolucent zones around the acetabular cup (NTA) and difference in head-cup edge distance (DHCD).

RESULTS

The numerical value of TA, DVD1, DHCD, AA and NTA in the loosening group was significantly higher than in the control group, and the differences were all statistically significant (P < 0.05). The critical values of DVD1, DHCD, AA and NTA were 1.49 cm, 0.16 cm, 53.2 ° and 1, respectively. The combined imaging diagnostic criteria for acetabular cup loosening are defined as the simultaneous fulfillment of the following two conditions: (1) NTA ≥ 1; (2) AA ≥ 53.2° or DHCD ≥ 0.16 cm. The results of the validation analysis were statistically significant.

CONCLUSIONS

The combined imaging diagnostic criteria for aseptic loosening of the acetabular cup after total hip arthroplasty, established in this study, demonstrate superior diagnostic efficacy compared to single imaging parameters. This approach does not rely on postoperative baseline radiographs or serial follow-up radiographs and can accurately determine the specific location of prosthetic loosening.

Vibratory and conventional impaction of acetabular components into porcine acetabula

Aims

Sufficient primary implant stability with minimal bone damage is one of the challenges for uncemented implant fixation to prevent periprosthetic fractures and implant loosening. A pilot study on a non-viscoelastic material (polyurethane foam) showed a reduced impaction force when using vibratory implant insertion. This study assessed the effectiveness of vibratory implant insertion compared to an established implant insertion method in physiological viscoelastic bone from porcine hips.

Methods

Acetabular components were impacted line-to-line and into 1 mm nominal undersized cavities in porcine acetabula (n = 24 in total, n = 6 acetabula per group of study) using vibration (60 Hz) and 1 Hz (established) impaction methods. The impaction force, remaining polar gap, and lever-out moment were measured and compared between the impaction methods and different press-fits.

Results

The vibratory impaction method produced almost 40% lower impaction forces at both press-fit levels. However, complete seating at the nominal press-fit of 1 mm was not achieved, and primary stability was lower for the vibratory impaction for either press-fit.

Conclusion

Bone fracture risk due to high impaction forces could be reduced by vibrational implant insertion at the cost of a reduction in primary stability. The outcome of the vibratory impaction method in porcine bone was similar to a previous study using polyurethane foams, suggesting that the viscoelasticity of bone may not play a crucial role during press-fit implant impaction.

Radiographic and Clinical Outcomes After Direct Anterior Versus Mini Posterior Total Hip Arthroplasty

Background

Total hip arthroplasty (THA) is a successful surgical treatment for end-stage hip arthritis. There is controversy over whether the surgical approach leads to any differences in implant sizing, implant positioning, and clinical outcomes. This study sought to compare radiographic and clinical outcomes when performing primary THA through the direct anterior approach (DAA) and posterior approach (PA).

Methods

In this retrospective cohort study of patients undergoing primary THA, 198 DAA patients were matched to 198 PA patients. Surgeries were performed by 3 fellowship-trained surgeons. Radiographic parameters analyzed were acetabular cup anteversion and abduction angles, femoral stem coronal alignment, femoral offset, and leg-length discrepancy. Postoperative complications, including periprosthetic joint infection, wound complications, periprosthetic fracture, and dislocation, were extracted from the medical record. Statistical analysis was performed to compare radiographic and clinical outcomes between groups.

Results

There were no statistically significant differences for any postoperative complications between the 2 groups. One dislocation occurred in the PA group, and no dislocations occurred in the DAA group. DAA had a longer operative time (117 vs 79 minutes, P < .01). PA had a higher increase in femoral offset compared to the contralateral limb (2.76 mm vs 1.01 mm, P < .01), higher cup anteversion (26.17° vs 23.44°, P < .001), and higher use of dual mobility components (6.06% vs 1.01%, P = .007).

Conclusions

Both DAA and PA lead to acceptable clinical and radiographic outcomes for primary THA, with significant differences noted for cup position, femoral offset, and use of dual mobility components. These differences likely represent surgeon factors to help mitigate the risk for dislocation.

Quarter Century Outcomes of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty

BACKGROUND

Alumina ceramic-on-ceramic (CoC) bearings were widely used in total hip arthroplasty (THA) due to their superior wear resistance and inert properties, making them ideal for young, active patients who require long-lasting implants. This study aimed to synthesize findings from previous reports, providing a comprehensive follow-up of at least 25 years on the clinical and radiologic outcomes, the prevalence of osteolysis, and implant survivorship in patients undergoing primary cementless CoC THA.

METHODS

We have previously reported 5- to 10-year outcomes following the implementation of third-generation alumina-on-alumina bearings in a consecutive series of 100 primary cementless THAs. This report updates those results with a minimum follow-up of 25 years. Of the original cohort, 58 patients who had 67 hips were available for the latest follow-up. Clinical assessments were performed using the Harris Hip Score and pain questionnaires. Radiographic evaluations were employed to assess implant fixation and osteolysis.

RESULTS

At the final follow-up, the implant survival rate was an impressive 96.3%, with revision of the implant as the end point. The mean Harris Hip Score improved significantly from preoperative values to 90.1, indicating excellent functional outcomes. The incidence of ceramic-related noise increased over time, with three cases of ceramic head fractures requiring a change of bearings. Notably, the extent of stem notching observed in earlier reports did not show further progression. Radiologically, all implants demonstrated bony ingrowth with no signs of aseptic loosening or major osteolysis.

CONCLUSIONS

The long-term (minimum 25-year) follow-up of alumina-on-alumina bearings in primary cementless THA demonstrates outstanding implant survivorship, excellent functional outcomes, and minimal adverse effects over 25 years. Despite some issues like ceramic-related noise and component fractures, the overall performance of CoC bearings remains highly encouraging, particularly suitable for young, active patients. Surgeons should provide appropriate education to both potential THA candidates and patients who already have THAs with CoC bearings.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Enhancing the accuracy of cup placement in total hip arthroplasty using CT-based navigation by a trainee surgeon: a retrospective cohort study

BACKGROUND

The learning curve of total hip arthroplasty (THA) using the anterior approach in the supine position is considered to be long owing to limited surgical field visualization. This study aimed to investigate the learning curve of a trainee's cup placement using computed tomography (CT)-based navigation, focusing on identifying the number of cases required to achieve proficiency.

METHODS

This retrospective cohort study included 112 hips that underwent total hip arthroplasty using CT-based navigation via anterolateral approach in the supine position by a trainee surgeon who had performed fewer than 20 prior THA cases. The absolute differences in cup alignment between postoperative measurements and intraoperative records, and differences in three-dimensional position between postoperative measurements and preoperative plan were assessed using the Mann-Whitney U test. A receiver operating characteristic (ROC) curve was used to determine the cutoff point for achieving accuracy.

RESULTS

The absolute differences were 2.4°±2.5° (inclination) and 2.4°±2.0° (anteversion), and 1.5 mm ± 1.3 mm (coronal plane) and 1.4 mm ± 1.2 mm (axial plane). The ROC curve identified 20 cases as the cutoff point for proficiency, with significant improvement in cup inclination accuracy. Multivariate analysis revealed that the first 20 cases (odds ratio, 10.4; 95% confidence interval, 3.1-34.5) were a predictive risk factor for inaccurate cup alignment. No cup revisions or dislocations occurred.

CONCLUSIONS

This is the first study to identify the learning curve of cup placement using CT-based navigation via an anterior approach by an inexperienced trainee surgeon. Proficiency in cup placement was achieved after 20 cases using CT-based navigation.

Evaluation of cup placement accuracy in computer assisted total hip arthroplasty

BACKGROUND

Total hip arthroplasty (THA) accuracy has improved significantly with various advances in computer-assisted equipment (CAE), including robotic systems, computed tomography (CT) navigation, and portable navigation. However, no studies have directly compared the accuracy of acetabular cup placement and its impact on patient-reported outcome measures (PROMs) across these three CAE systems. In this study, we aimed to evaluate cup placement accuracy and PROMs in THA using different CAE systems.

METHODS

This retrospective analysis included 196 patients (202 hip joints) who underwent THA with three CAE systems from May 2021 to August 2023. Patients were categorized into the robotic system (73 hips), CT navigation (83 hips), and portable navigation (46 hips). Postoperative CT scans measured cup placement angles-radiographic inclination (RI) and radiographic anteversion (RA) -and compared them with preoperative target angles. Anterior-posterior (AP) cup position differences were evaluated by measuring the distance between the acetabular and cup center in the axial view of the postoperative CT scans. PROMs were evaluated using the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) at 3 and 12 months.

RESULTS

Demographic characteristics, including age, sex, primary disease, and Body Mass Index, were similar across groups. The robotic system exhibited significantly smaller deviations in ΔRI and ΔRA compared to CT navigation and portable navigation. AP cup position differences were also smaller in the robotic system versus portable navigation; however, the difference between the robotic and CT navigation systems was not statistically significant. Despite the superior precision of cup placement in the robotic system, no significant differences in JHEQ scores were observed among the groups at 3 and 12 months.

CONCLUSION

Robotic systems demonstrated superior accuracy in cup placement. However, short-term PROMs did not significantly differ, suggesting that PROMs may not solely depend on accurate cup placement. Future research should investigate additional factors influencing PROMs.

Application and exploration of total hip arthroplasty for developmental dysplasia of the hip assisted by full-process robotics

OBJECTIVE

This study aimed to explore whether total hip arthroplasty (THA) aided by full-process robotics was effective in patients undergoing developmental dysplasia of the hip (DDH).

METHODS

Totally 112 patients were enrolled and classified into robotic-assisted group (n = 56) and the conventional group (n = 56). In addition, retrospective analysis was used for comparing the difference in therapeutic efficacy.

RESULTS

A total of 112 patients received THA, and were followed up for (12.78 ± 0.76) months on average, with no occurrence of associated complications. For patients in robot-assisted group, their abduction and anteversion angles of acetabular cup placement were in the safe zone, while those in 8 patients of the conventional group were outside the safe zone. Compared to the conventional group, the robot-assisted group had higher postoperative Harris Hip Score and FJS, whereas lower VAS score.

CONCLUSION

Robot-assisted THA is advantageous in terms of both intraoperative precision and postoperative effect on the treatment of patients with DDH.

The accuracy of a patient-specific femoral planning and delivery system for total hip arthroplasty

INTRODUCTION

A primary objective when performing a total hip arthroplasty (THA) is to restore hip biomechanics in accordance with a chosen surgical plan. The aim of this study was to assess the accuracy of a 3D-printed patient-specific guide for delivering a planned femoral osteotomy for both a posterior and an anterior approach.

METHODOLOGY

40 patients (20 anterior and 20 posterior) scheduled for THA received a preoperative work-up allowing for patient-specific implant sizing and positioning. Following surgeon confirmation, a patient-specific guide was designed and printed, enabling the desired osteotomy to be executed. Achieved osteotomies were assessed using commercially available software platforms. Planning accuracy was also assessed using both the planning platform as well as more traditional 2D-templating techniques.

RESULTS

The mean deviation between the planned and achieved osteotomy level was -0.6 mm (range -4.1-6.4 mm). 95% of the achieved osteotomy levels were within 3 mm of the plan for both the posterior and anterior approach groups. 70% of the Optimized Positioning System (OPS) planned femoral components were the exact size as planned versus 25% of the 2D-planned components. 98% of the OPS planned femoral components were within 1 size of plan versus 58% for the 2D-planned components. No sizing accuracy difference was observed between planning approaches (p = 0.70).

CONCLUSIONS

A patient-specific osteotomy guide can be a simple and accurate method to reproduce a planned femoral neck resection through an anterior or posterior approach. Further, 3D planning appears to more accurately predict femoral sizing in THA than more conventional 2D methods.

Usefulness of an Extensible Trial Neck in Total Hip Arthroplasty

BACKGROUND

Maintaining appropriate soft tissue tension is essential in total hip arthroplasty (THA). Surgeons generally achieve this by altering the neck length. However, experimenting with different neck lengths is time-consuming, as it requires repeated hip dislocations. To address this, we have used a new extensible trial neck device that allows for easy adjustment of neck length during surgery. This device can help surgeons avoid the need for repeated hip dislocations to determine the correct neck size. The objective of this research was to investigate whether this device could help shorten operative times and decrease surgical invasion for patients.

MATERIALS AND METHODS

Patients undergoing THA were randomly separated into two groups. The first group used the extensible trial neck during trial reduction after the stem and cup were placed (group M), while the second group used a conventional trial neck (group C). Operative time, blood loss, number of additional dislocations needed during the operation, and C-reactive protein (CRP) and creatine phosphokinase (CPK) levels after the operation were compared.

RESULTS

Operative time was significantly shorter and the number of additional dislocations required to choose the final neck size was significantly lower in group M compared with group C. No significant difference in blood loss was observed. CRP and CPK levels days 3 and 7 after surgery decreased in group M compared with group C.

CONCLUSION

The extensible trial neck was useful for THA by greatly reducing operative time and stress on the patient. [Orthopedics. 2025;48(2):e88-e93.].

Computed tomography-based navigation versus accelerometer-based portable navigation in total hip arthroplasty for dysplastic hip osteoarthritis

PURPOSE

Accurate cup placement is challenging in total hip arthroplasty (THA) for dysplastic hip osteoarthritis (DHOA) because of the complex morphology of the acetabulum. Studies have reported good accuracy for total hip arthroplasty (THA) using computed tomography-based navigation (CTN); however, in recent years, portable navigation (PN) has become more widely applied because of its low cost and ease of use. This study aimed to compare the accuracy of portable navigation with that of CT-based navigation.

METHODS

A total of 114 patients underwent THA for DHOA via the standard posterior approach in the lateral decubitus position using the CTN (CTN-THA group) or PN (PN-THA group) system. After propensity score matching, 32 patients were included in each group. The accuracy of cup inclination, anteversion, cup placement position, and operative time were compared between the groups.

RESULTS

There was no difference in accuracy error between the CTN-THA (inclination 2.8 ± 2.0° and anteversion 3.4 ± 2.1°) and PN-THA groups (inclination 2.5 ± 1.8° and anteversion 2.6 ± 2.2°). The CTN-THA group (inclination 2.2 ± 2.0° and anteversion 2.1 ± 1.6°) achieved better navigation error compared to the PN-THA group (inclination 2.6 ± 2.2° and anteversion 3.8 ± 3.3°). The error of cup placement position in the anteroposterior direction was significantly larger in the PN-THA group (4.27 ± 3.02 mm) than in the CTN-THA group (2.13 ± 2.17 mm). The operative time was significantly longer in the CTN-THA group (115 ± 41 min) than in the PN-THA group (87 ± 19 min).

CONCLUSIONS

CTN-THA exhibited better accuracy than PN-THA for both cup placement angles and positions. CTN-THA tended to increase the operative time compared to PN-THA.

Impact of Hip Rotation Angle Following Total Hip Arthroplasty with Leg Lengthening

Background/Objectives: Few studies report on hip rotation after total hip arthroplasty (THA); however, details of the factors affecting the hip rotation angle are unknown. We aimed to investigate the factors related to hip rotation after THA. Methods: This study included 124 consecutive patients who underwent THA. We retrospectively analyzed the correlation between changes in the rotation angle of the femur relative to the pelvis, global femoral offset, and femoral version and leg lengthening. Moreover, we performed a multivariate regression analysis of these parameters to calculate the efficacy of the change in the rotation angle of the femur relative to the pelvis. Results: Leg lengthening and femoral version change were negatively correlated, whereas change in global femoral offset was positively correlated with leg lengthening, with correlation coefficients of 0.376, 0354, and 0.334, respectively. Regarding the multiple regression analysis, only leg lengthening was correlated with the change in rotation angle of the femur relative to the pelvis, with a coefficient of -0.336. Conclusions: The change in the rotation angle of the femur relative to the pelvis is only associated with leg lengthening in multivariate analysis. In actual planning, in cases where the hip is internally rotated, it may be better not to excessively increase leg length, decrease anterior stem anteversion, or increase global femoral offset. Thus, physicians should avoid large leg lengthening for patients with highly external rotation in their hip joint as it may lead to increased internal rotation of the hip, consequently resulting in relative malpositioning and subsequent implant impingement and/or dislocation following THA.

Evaluating the Accuracy of a Computed Tomography-Based Mixed-Reality Navigation Tool for Acetabular Component Positioning in Total Hip Arthroplasty

BACKGROUND

Robotics and navigation systems have improved the accuracy and precision of acetabular component placement in total hip arthroplasty (THA). The purpose of this study was to determine if the intraoperative use of a novel mixed-reality (MR) navigation system resulted in accurate acetabular component placement with minimal outliers.

METHODS

A series of 79 patients who underwent THA performed by a single surgeon using a novel MR navigation system were retrospectively reviewed. The preoperative planned acetabular component operative inclination (OI) and tilt-adjusted operative anteversion (OA) were collected for each case. At the six-week follow-up, each patient underwent three-dimensional EOS imaging, which was used to measure the acetabular component placement via validated measuring software. Patients who had bilateral THAs or three-dimensional images that did not have critical bony landmarks visible for measurement were excluded from the study. Absolute error was calculated for both inclination and anteversion. Outliers were defined as any cup position that was outside a range of ± 10 degrees from the preoperatively planned target. A total of 39 patients met the inclusion criteria.

RESULTS

The mean planned OI for each patient was 40.8 (range, 40 to 41) degrees, and the mean measured postoperative OI was 40.4 (range, 37 to 46) degrees (P = 0.40), resulting in a mean absolute error of 1.8 (range, zero to five) degrees. The mean planned OA was 30.2 (range, 25 to 35) degrees, and the mean measured postoperative OA was 31.1 (range, 27 to 42) degrees (P = 0.11), resulting in a mean absolute error of 2.0 (range, zero to six) degrees. There were no outliers in either OI or OA.

CONCLUSIONS

The results of this study suggest that the use of MR navigation during THA results in accurate postoperative acetabular component inclination and anteversion relative to the preoperative plan without outliers.

Impact of CT-based navigation, large femoral head, and dual-mobility liner on achieving the required range of motion in total hip arthroplasty

Aims

This study aimed to investigate whether the use of CT-based navigation enhances: 1) the accuracy of cup placement; and 2) the achievement rate of required range of motion (ROM). Additionally, we investigated the impact of using a large femoral head and dual-mobility liner on the achievement rates.

Methods

This retrospective study analyzed 60 manual and 51 CT-based navigated primary total hip arthroplasties performed at a single facility. Postoperative CT scans and CT-based simulation software were employed to measure the cup orientation and to simulate the ROM. We compared the absolute errors for radiological inclination (RI) and radiological anteversion (RA) between the two groups. We also examined whether the simulated ROM met the required ROM criteria, defined as flexion > 110°, internal rotation > 30°, extension > 30°, and external rotation > 30°. Furthermore, we performed simulations with 36 mm femoral head and dual-mobility liner.

Results

The absolute errors of RI and RA from the preoperative plan were significantly smaller in the CT-based navigation group (3.7° (SD 3.5°) vs 5.1° (SD 3.5°); p = 0.022, and 3.9° (SD 3.5°) vs 6.8° (SD 5.0°); p = 0.001, respectively). The proportion of cases achieving the required ROM in all directions was significantly higher in the CT-based navigation group (42% vs 63%; p = 0.036). The achievement rates of the required ROM were significantly higher with the use of a 36 mm ball or dual-mobility liner compared to the use of a 32 mm ball (65% vs 51%; p = 0.040 and 77% vs 51%; p ≤ 0.001, respectively).

Conclusion

CT-based navigation enhanced required ROM achievement rates by > 20%, regardless of the ball diameter. The improved accuracy of cup placement through CT-based navigation likely contributed to the enhancement. Furthermore, the use of large femoral heads and dual-mobility liners also improved the required ROM achievement rates. In cases with a high risk of dislocation, use of these devices is preferred.

Radiological assessment of cup anteversion with a novel 3D-printed highly-porous titanium dual mobility cup

BACKGROUND

Cup anteversion after primary total hip arthroplasty (THA) with monobloc dual mobility cups (DMC) is difficult to measure on anterior-posterior (AP) pelvic radiographs because of the implant radiopacity and cup design which do not allow for an accurate visualization of the radiographic projection of the cup equatorial rim and the femoral head. This study aims to radiographically investigate on the reliability and accuracy of different measurement methods for cup anteversion in monobloc DMC THA, by comparing a novel titanium cup with conventional cup designs.

METHODS

97 THAs with a monobloc 3D-printed titanium DMC were radiographically assessed for cup radiographic anteversion (RA) one month postoperatively. RA were measured by three blinded observers through Lewinnek, Woo-Morrey methods and an open access mathematical software (GeoGebra), used as reference method. Intra- and interobserver reliability of RA measurements were evaluated for each method using intraclass correlation coefficient (ICC). Accuracy was assessed comparing Lewinnek and Woo-Morrey methods with GeoGebra. Moreover, further 98 THAs with conventional different brand DMC were radiographically assessed as control group by using the same methods.

RESULTS

ICC for intra- and interobserver reliability for RA measurements with GeoGebra, Lewinnek and Woo-Morrey methods were 0.975-0.980, 0.978 - 0.965, and 0.979 - 0.958, respectively, for the titanium DMC group. Lewinnek resulted more accurate for RA than Woo-Morrey, differing by + 0.4° (p = 0.06) and + 4.4° (p < 0.001) from GeoGebra, respectively. ICC for intra- and interobserver reliability for GeoGebra, Lewinnek and Woo-Morrey methods were 0.848 - 0.756, 0.843 - 0.801, and 0.965 - 0.958, respectively, for the control DMC group. Lewinnek and Woo-Morrey methods differed by -2.3° and + 5.1° from GeoGebra, respectively (p < 0.001).

CONCLUSIONS

RA measurements are more consistent, repeatable and accurate with a titanium DMC than standard DMC, due to the minor radiopacity of the former cup which enable RA measurements on AP radiographs. Conversely, RA measurements of conventional DMC are more consistent but less accurate if performed on cross-table lateral radiographs by Woo-Morrey method than AP radiographs.

Comparing Stability, Gait, and Functional Score after 40-mm Dual-Mobility Hip Arthroplasty to 36-mm Head Hip Arthroplasty in Elderly Hip Fracture Patients

Backgroud

This study aimed to compare the intraoperative stability and early clinical outcomes of 40-mm diameter dual mobility (DM)-total hip arthroplasty (THA) with 36-mm ceramic head (large head) THA in active elderly patients with hip fractures.

Methods

A prospective randomized controlled trial was conducted from May 2022 to December 2022. Inclusion criteria were as follows: age ≥ 60 years, displaced femoral neck fracture, Koval grade 1 or 2, planned 54-mm acetabular component, and over 1-year follow-up. Intraoperative stability tests were performed on all patients (internal rotation at 45°, 60°, and 90° of hip fracture). Functional outcomes (Harris Hip Score and University of California, Los Angeles [UCLA] Score) were evaluated at 6 weeks and 3 months postoperatively. Gait analysis using artificial intelligence (AI) techniques was conducted at 3 months postoperatively.

Results

The study included 36 DM-THA patients (mean age, 69.6 ± 2.2 years; 44% women) and 37 large head THA patients (mean age, 69.6 ± 1.2 years; 64% women). No statistically significant differences were observed in functional outcomes and hip range of motion between the 2 groups. However, there was a significant difference in the gait speed and stance-swing phase of the large head THA group and the DM-THA group: the DM-THA group demonstrated superior gait speed (2.85 ± 0.83 kph vs. 2.04 ± 1.04 kph, p = 0.003) and higher stance phase ratios (operated side: 63.57% ± 3.82% vs. 48.19% ± 5.50%, p < 0.001; opposite side: 62.77% ± 2.27% vs. 49.93% ± 6.94%, p < 0.001). In the stability test at 90° of hip flexion, the DM-THA group had a measurement of 48.40° ± 5.17°, while the large head THA group had a measurement of 30.94° ± 2.98° (p = 0.012). Despite the lack of statistical significance, the intraoperative stability test showed the dislocation angle was notably different between the groups in the hip flexion position of 60° (51.60° ± 6.09° in the DM-THA group and 40.00° ± 2.80° in the large head THA group, p = 0.072).

Conclusions

Superior results were observed in the intraoperative stability test and early recovery of gait after DM-THA compared to large head THA. We believe that DM-THA can be a useful surgical option for THA in elderly patients with hip fractures.

Analysis of posterior hip joint impingement about developmental dysplasia of the hip after total hip arthroplasty

BACKGROUND

Total hip arthroplasty is the preferred treatment for advanced hip osteoarthritis, yet complications like hip dislocation (0.2 %-10 %) persist due to factors such as implant design, positioning, surgical technique, and patient-specific conditions. Impingement between prosthetic components or the acetabulum and proximal femur is a primary cause of instability.

METHODS

A retrospective analysis of 120 patients (130 hips) undergoing total hip arthroplasty at XX Hospital (2011-2023) categorized patients by lateral center-edge angle: developmental dysplasia of the hip, borderline developmental dysplasia of the hip, and normal hip. ct imaging facilitated virtual 3D bone models for motion analysis, excluding cases with prior hip surgery or spinal fusion. Statistical analyses utilized the Mann-Whitney U test and one-way ANOVA.

FINDINGS

The developmental dysplasia of the hip group showed the highest posterior impingement frequency, significantly affecting range of motion in flexion, adduction, and external rotation compared to borderline developmental dysplasia of the hip and normal hip groups. Variations in femoral neck anteversion, lesser trochanter version, and ischiofemoral space were notable. Posterior impingement commonly occurred between the lesser trochanter and ischial tuberosity.

INTERPRETATION

Posterior bony impingement emerged as a predominant factor reducing range of motion and increasing dislocation risk, particularly in developmental dysplasia of the hip patients, challenging the conventional "safe zone" for implant positioning. Personalized surgical strategies tailored to individual bone morphology are crucial for enhancing total hip arthroplasty outcomes and minimizing complications, although limitations include the exclusion of soft tissue influences and focusing solely on range of motion until impingement occurs.

Does Osteonecrosis of the Femoral Head Increase Early Complication Rates After Total Hip Arthroplasty? A Japanese Nationwide Medical Claims Database Study

BACKGROUND

Osteonecrosis of the femoral head (ONFH) and osteoarthritis (OA) are two common diagnoses for patients undergoing total hip arthroplasty (THA). The early surgical complications in THA for ONFH compared to OA are inconsistently reported. Therefore, this study aimed to evaluate whether THA for ONFH was associated with early postoperative complications in comparison to THA for OA using a large database of Japanese patients.

METHODS

In this cohort study, using a Japanese national medical claims database on ONFH and OA patients undergoing THA from December 2011 to March 2023, we assessed the surgical-related complications, medical complications, and mortality during hospitalization after propensity score matching by age, sex, body mass index, and comorbidities. A total of 24,326 pairs of THAs for ONFH and OA were included.

RESULTS

In the THA for ONFH group, the odds ratios for various complications were as follows: dislocation (1.3, 95% CI [confidence interval]: 1.1 to 1.6, P < 0.01), infection (1.0, 95% CI: 0.8 to 1.2, P = 0.94), periprosthetic fracture (1.0, 95% CI: 0.8 to 1.4, P = 0.86), nerve palsy during hospitalization (0.4, 95% CI: 0.2 to 0.9, P = 0.034), pneumonia (1.7, 95% CI: 1.1 to 2.5, P < 0.01), deep vein thrombosis (0.9, 95% CI: 0.8 to 1.0, P = 0.018), pulmonary embolism (1.5, 95% CI: 0.9 to 2.5, P = 0.14), cardiac events (0.7, 95% CI: 0.3 to 2.1, P = 0.55), cerebrovascular events (0.7, 95% CI: 0.5 to 1.0, P = 0.084), acute renal failure (1.4, 95% CI: 0.4 to 4.4, P = 0.56), and mortality during hospitalization (1.8, 95% CI: 1.3 to 2.4, P < 0.01).

CONCLUSIONS

These findings contribute to identifying postoperative risks for ONFH patients and suggest that more attention should be paid to preoperative planning and postoperative care for ONFH patients.

Robotically Assisted vs. Manual Total Hip Arthroplasty in Developmental Hip Dysplasia: A Comparative Analysis of Radiological and Functional Outcomes

Background/Objectives: Developmental dysplasia of the hip (DDH), defined by the malalignment of the femoral head and acetabulum, is a major precursor to coxarthrosis, posing substantial challenges during total hip arthroplasty (THA). Patients with coxarthrosis secondary to DDH often exhibit acetabular bone insufficiency, which makes challenging surgical reconstruction difficult. This study aimed to compare the radiologic and functional outcomes of robotically assisted and conventional manual THA techniques in patients with coxarthrosis secondary to Crowe type III-IV DDH. Methods: This prospective study included 40 patients divided into robotically assisted (n = 20) and conventional manual (n = 20) THA groups. Evaluations encompassed hip pain (Visual Analogue Scale, VAS), function (Harris hip score and University of California, Los Angeles, activity scale), quality of life (Short Form-12), and prosthesis sensation (Forgotten Joint Score-12). Radiologic outcomes included acetabular inclination and anteversion angles. Femoral shortening, operative duration, and follow-up times were also analyzed. Results: Demographic characteristics did not differ between groups (p > 0.05). Robotically assisted THA exhibited a significantly longer operative time (171.40 ± 11.96 vs. 150.30 ± 14.67 min; p = 0.001) but a shorter follow-up (29.3 ± 8.51 vs. 52.95 ± 18.96 months; p = 0.001), without a difference in the amount of femoral shortening (p = 0.947). Despite the extended surgical duration, the two techniques achieved comparable radiologic outcomes, with no significant differences in acetabular inclination or anteversion angles (p > 0.05). Functional assessments, including Harris hip scores (73.85 vs. 73.95; p = 0.978), UCLA activity scores, and VAS, indicated similar efficacy between groups. SF-12 physical and mental quality of life and Forgotten Joint Score-12 prosthesis sensation did not differ between groups (p > 0.05). Conclusions: This study concludes that robotically assisted and conventional manual THA present similar radiologic and functional outcomes in patients with coxarthrosis secondary to Crowe type III-IV DDH, as displayed by comparable acetabular anteversion and inclination alignment, femoral shortening, hip function, pain, quality of life, and prosthesis sensation scores. While robotically assisted THA requires a longer operative time, its precision in implant placement may hold potential advantages for long-term outcomes, demanding further investigation in extended follow-up studies.

Lewinnek zone not "the be-all and end-all" functional planning for acetabular component positioning in total hip arthroplasty

BACKGROUND

Proper positioning of a total hip arthroplasty (THA) plays a crucial role in the success and long-term survivorship of the implant. Cup positioning within the Lewinnek Safe Zone (LSZ) does not, however, avoid implant dislocation. Thus, the concept of a functional cup position has been introduced. The purpose of this study was to assess the discrepancy between LSZ and the acetabular cup position suggested by the patient's specific functional planning. The hypothesis was that a mismatch does exist.

METHODS

One hundred consecutive patients with primary hip osteoarthritis undergoing primary THA with a personalized functional preoperative planning and patient-specific cup implantation system were enrolled. Anatomical and spino-pelvic functional parameters were recorded and, for each patient, a "safe cup orientation" was suggested. The suggested functional safe zone was compared to the LSZ.

RESULTS

The mean suggested inclination was 39° ± 3° (range 32°-45°). The mean suggested anteversion was 21° ± 3° (range 12°-28°). The patient's functional acetabular inclination (AI) corresponded to the LSZ in one of the 100 patients, whereas the acetabular anteversion (AV) was outside the LSZ in 8 of the 100 patients. The mean pelvic tilt while standing and sitting were 0.5° ± 7° (range 21°-45°) and -6° ± 16.7° (range -63°-33°), respectively. The mean pelvic incidence was 52° ± 9.7° (range 33°-83°).

CONCLUSION

When a functional patient's specific preoperative planning is performed, the LZS does not correspond to the patient's functional safe zone in about 8% of patients. The concept of a universal safe zone should be revisited, and a functional personalized safe zone may have to be more widely considered.

The Visual Assessment of Cup Position on Anteroposterior Pelvis Radiographs Before Revision Total Hip Arthroplasty for Instability Is Highly Deceiving

BACKGROUND

Is "eyeballing" enough to determine cup malposition on anteroposterior (AP) pelvis radiographs before revision total hip arthroplasty (rTHA) for instability? We aimed to determine the following: (1) the reliability of eyeballing cup inclination/anteversion on AP pelvis radiographs vs geometrical measurements and (2) whether visual assessments are affected by surgeon experience.

MATERIALS AND METHODS

Fifteen de-identified standing AP pelvis radiographs obtained before rTHA for instability were evaluated by one orthopedic surgeon who measured inclination/anteversion of the cups (n=15) using a new simplified method based on basic geometry. Subsequently, 4 orthopedic surgeons and 4 fellows (postgraduate year 6) assessed inclination/anteversion by eyeballing. A modified Lewinnek safe zone range was employed to categorize each value (in degrees) by geometrical measurements or by raters' eyeballing as within or outside the safe zones. Cohen's kappa (κ) statistics were performed. Mean κ values of attending surgeons and fellows were compared.

RESULTS

According to geometrical measurements, 8 and 12 cups were in malposition (for inclination and anteversion, respectively). By just eyeballing, no attending surgeon or fellow attained an excellent (κ>0.8) level of agreement when compared with geometrical measurements. Only 1 attending surgeon attained a substantial (κ=0.6-0.8) level of agreement (κ=0.737, for inclination, P=.003). Mean κ values of attending surgeons and fellows were 0.476 and 0.187, respectively, for inclination (P=.2) and 0.416 and 0.428, respectively, for anteversion (P=.9).

CONCLUSION

Eyeballing cup position on AP pelvis radiographs before rTHA for instability is extremely misleading, regardless of surgeon experience. It is imperative to always measure the inclination and anteversion of the cup. [Orthopedics. 2025;48(1):e22-e26.].

Computed Tomography Evaluation of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty With More Than 20 years of Follow-Up: Is a Follow-Up Computed Tomography Scan Necessary?

BACKGROUND

Ceramic-on-ceramic (CoC) bearings have been increasingly used in total hip arthroplasty (THA) because of their superior wear resistance and biocompatibility. However, there is a scarcity of reports on the computed tomography (CT) evaluation of CoC bearings with more than 10 years. The aim of this study was to evaluate the long-term CT results of THA using CoC bearings for more than 20 years of follow-up. We hypothesized that there would be no wear, osteolysis, or ceramic fracture.

METHODS

Between November 1997 and June 2003, 956 hips underwent THA using alumina-on-alumina bearings at a tertiary referral hospital. Among them, 107 hips were assessed, all of which underwent a CT examination more than 20 years after the index surgery. The mean age at the time of surgery was 41 years, and a CT scan was performed at an average of 22.0 years postoperatively (range, 20.0 to 25.1). The CT scans were thoroughly assessed for osteolysis, stem notching, and ceramic component fracture.

RESULTS

No loosening was observed in the acetabular cup or femoral stem. Stem notching was observed in 3 hips (2.8%). In the CT scan taken after a minimum of 20 years of follow-up, 1 case (0.9%) of osteolysis around the cup and 2 cases (1.9%) of osteolysis around the femoral stem were noted. Suspected chip fractures of the ceramic insert were discovered in 4 cases (3.7%). Despite these findings, the patients remained asymptomatic, and no subsequent surgical intervention was needed after close follow-up.

CONCLUSIONS

Routine CT examinations for patients who underwent THA using CoC bearings over 20 years ago revealed unexpected findings, such as osteolysis and suspected chip fractures of the ceramic liner. However, routine CT scans may not be universally necessary. The CT evaluation in this cohort should be selectively performed for patients who have relevant clinical symptoms.

LEVEL OF EVIDENCE

Level III, Therapeutic study.

Impact of the difference between preoperative planning and intraoperative femoral neck osteotomy level on stem alignment

BACKGROUND

The combined anteversion theory is used for implant placement in total hip arthroplasty (THA). While majority of the research emphasizes the precise placement of the acetabular cup, there's less focus on stem alignment. This study aimed to investigate the impact of the discrepancy between the preoperatively planned femoral neck osteotomy level and the actual osteotomy level during surgery on stem alignment.

MATERIALS AND METHODS

The study involved 232 patients (258 joints) who had a total hip arthroplasty (THA) between April 2018 and December 2022 at our hospital. They were implanted with either the ACTIS stem (Depuy Synthes) or Taperloc Complete XR 123° (Zimmer Biomet)-147 joints with ACTIS stem and 111 with Taperloc stem. Three-dimensional templating software was used to evaluate preoperative planning and postoperative stem placement angles. The difference between the actual and preoperatively planned osteotomy levels was also measured. The impact of this difference in femoral neck osteotomy level on stem alignment was evaluated.

RESULTS

In the ACTIS stem group, the femoral neck osteotomy level was - 0.3 ± 3.7 mm. The stem alignment had a varus of 1.8 ± 1.9°, extension of 0.1 ± 1.5°, and anteversion of 2.4 ± 5.9°, compared to preoperative plans. A positive correlation was identified between osteotomy level and varus/valgus alignment (r = 0.607, p < 0.01), with a weak correlation for anteversion (r = 0.236, p < 0.01). No correlation existed with flexion/extension. In the Taperloc stem group, osteotomy level was 2.2 ± 3.1 mm. The postoperative stem showed a varus of 1.6 ± 1.5°, extension of 0.5 ± 1.7°, and anteversion of 4.9 ± 6.5°. A correlation was observed between osteotomy level and varus/valgus alignment (r = 0.476, p < 0.01), but not with flexion/extension or anteversion.

CONCLUSIONS

The study examined how differences in planned vs. actual femoral neck osteotomy affect stem alignment in THA using ACTIS stem and Taperloc stem. We found that osteotomy level influenced varus/valgus alignment; mildly affected flexion/extension; and had no effect on anteversion.

Robotic-Assistance in Total Hip Arthroplasty Is Associated With Decreased Dislocation Rates

Background

As the use of robotics in total hip arthroplasty (THA) continues to gain popularity, differences in clinical outcomes when compared to manual techniques have remained unclear. This study aimed to compare postoperative complications between patients undergoing robotic-assisted techniques and manual THA for primary osteoarthritis at 90 days, 1 year, and 2 years.

Methods

Using an all-payer national database, we identified 405,048 patients who underwent either robotic-assisted or manual THA for primary osteoarthritis. A propensity match was performed for age, sex, a comorbidity index, chronic kidney disease, obesity, and diabetes, resulting in 7652 patients in each cohort. We assessed postoperative outcomes, including surgical site infections, pulmonary emboli, venous thromboemboli, wound complications, dislocations, aseptic revisions, periprosthetic joint infections, and periprosthetic fractures. We completed bivariate analyses via chi-square tests to assess categorical variables. We utilized student's t-tests to compare continuous variables, including ages and comorbidities. Odds ratios (ORs) were calculated for complications using 95% confidence intervals (CIs).

Results

The robotic-assisted cohort had lower rates of dislocation at 90 days (0.93 vs 1.41%, OR 0.65, 95% CI 0.48-0.88, P = .007), 1 year (1.32 vs 1.92%, OR 0.68, 95% CI 0.53-0.88, P = .004), and 2 years (1.66 vs 2.1%, OR 0.79, 95% CI 0.62-0.99, P = .049). Total surgical complications were significantly lower in the robotic-assisted cohort at 1 year (5.29 vs 6.16%, OR 0.85, 95% CI 0.74-0.98, P = .0205), but were similar at 90 days and 2 years. At 90 days, the rates of medical complications, including surgical site infections, pulmonary emboli, venous thromboemboli, and wound complications, were similar (all P > .05). The rates of periprosthetic joint infections, aseptic revision, periprosthetic fractures, and aseptic loosening were similar at all time points (all P > .05).

Conclusions

Patients who underwent robotic-assisted THA had lower rates of dislocation at 90 days, 1 year, and 2 years. This finding supports the use of robotic assistance in THA, though further research is needed to confirm and strengthen these findings.

Patient-Specific Acetabular Safe Zones in Total Hip Arthroplasty: External Validation of a Quantitative Approach to Preoperatively Templating Spinopelvic Parameters

Background

Spinopelvic mechanics are critical in total hip arthroplasty; however, there is no established consensus for adjusting acetabular component positioning based on spinopelvic parameters. This study aimed to (1) validate a recently developed Patient-Specific acetabular safe-zone calculator that factors in spinopelvic parameters and (2) compare differences with hip-spine classification targets.

Methods

A total of 3750 patients underwent primary total hip arthroplasty across 3 academic referral centers, with 33 (0.88%) requiring revision for instability. Spinopelvic parameters were measured before initial total hip arthroplasty, and acetabular component position was measured following the index and revision procedures. Most operations employed either computer navigation or robotic assistance (94%). Surgical approaches included both anterior and posterior techniques. Utilizing our recently developed patient-specific safe-zone calculator, theoretical intraoperative positions were calculated and compared to true component positions before and after revision.

Results

Among 33 patients who underwent revision, none dislocated at an average follow-up of 5.1 years. In the external validation cohort, the average absolute differences between the patient-specific safe-zone and the median hip-spine classification recommendation were 3.8° ± 2.1° inclination and 5.0° ± 3.2° version. For the pooled cohort, the absolute differences between the patient-specific safe-zone targets and the prerevision component positions were 7.9° ± 5.1° inclination and 11.4° ± 6.9° version. After revision, the mean absolute differences decreased to 3.6° ± 3.1° inclination and 5.8° ± 3.5° version (P < .001).

Conclusions

A patient-specific approach improved acetabular component positioning accuracy within 6° of version and 4° of inclination of stable, revised hips. Patient-specific safe zones provide quantitative targets for nuanced spinopelvic preoperative planning that may mitigate risk of instability and may indicate use of assisted technologies.

Mechanical studies for the rotational stability of a cemented stem in cases with stem anteversion adjustment in the cement mantle

INTRODUCTION

The cemented stem can accommodate various shapes of femurs and is a stable stem with long-term results. Additionally, the cemented stem is a highly versatile stem that can be used to adjust stem anteversion in patients with variable femoral anteversion. On the other hand, rotating a stem with increasing cement viscosity may result in reduced postoperative rotational stability.

MATERIALS AND METHODS

Rotational stability was compared using two different cementing techniques via in vitro models. Six stems in Group S (Static) were inserted and fixed until the cement was completely hardened. Six stems in Group R (Rotation) were inserted and then rotated 15° before the cement had fully cured. After the cement had completely set, a static rotation testing was performed in which the stem was rotated at a rate of 1°/sec to 20° while a vertical load of 600 N was applied. For the dynamic testing, a vertical load of 600 N and 10,000 cycles of repetitive rotation were applied at 10° around the stem axis at 0.1 Hz. After 10,000 cycles, maximum torque was compared between Groups S and R.

RESULTS

In both groups, the torque value increased proportionally to the rotation angle. There were no significant differences in resistance to static rotation between Groups S and R (P = 0.599). In the dynamic testing, there was no significant difference between Groups S and R in both minimum torque and maximum torque in any of the cycles. There were no differences in the rotational torque between Groups S and R at 10,000 cycles (P = 0.693).

CONCLUSIONS

The rotational stability of the cemented stems did not decrease in vitro when stem version control was performed up to 15° before the cement had completely hardened.

A novel method of acetabular component anteversion measurement on plain radiographs

BACKGROUND

Acetabular component anteversion (ACA) markedly impacts the outcome of total hip arthroplasty (THA) and thus is routinely measured on radiographs postoperatively. However, clinical ACA measurement methods are either too complicated or subjective due to three drawbacks: complex calculations, measurement of obscured points, and complex geometric drawings. This study aimed to develop a precise and convenient novel method of measuring ACA on routine radiographs without the three drawbacks and to verify its accuracy and reliability by comparing it against existing methods.

METHODS

A novel geometric principle to measure ACA was developed. Accordingly, a protractor was designed to measure radiographic anteversion (RA) on anteroposterior (AP) hip radiographs. Three researchers measured RA twice, using the protractor, McLaren's, and Pradhan's method on 26 computer-simulated radiographs with pre-set RAs and 20 actual radiographs. Accuracy was assessed by errors on simulated radiographs, and reliability was assessed by results of measurements on simulated and actual radiographs.

RESULTS

The absolute error of the novel method (1.01° ± 1.06°) was lower than McLaren's method (1.34° ± 1.16°) (p < 0.05) and not significantly different from Pradhan's method (1.10° ± 1.02°) (p = 0.392). The protractor's intra-rater and inter-rater reliability were good-to-excellent or excellent and higher or equivalent to the two other methods.

CONCLUSIONS

The novel method avoids the three major drawbacks of conventional methods. Its accuracy is significantly higher than McLaren's method and comparable to Pradhan's. The novel method has higher or non-inferior accuracy and reliability than McLaren's and Pradhan's methods.

Large cohort study on prevention strategies for dislocation in total hip arthroplasty

BACKGROUND

Dislocation is a major complication of total hip arthroplasty (THA). This study aimed to assess the dislocation rate after THA using the combined strategy of using CT-based navigation, large diameter heads, and posterior soft tissue repair in a large cohort.

METHODS

We included 1410 patients who had undergone primary cementless THA using the CT-based navigation system. The posterior approach was used by a single surgeon for all patients. The participants included 143 (10.1 %) men and 1267 (89.9 %) women, with a mean age of 65 years. The mean body mass index was 24 kg/m2. Additionally, the incidence rate of postoperative dislocation per year was calculated. The dislocation onset was classified as early when the dislocation occurred within 2 years of the primary THA and late when it occurred more than 2 years after the primary THA. Recurrence and revision rates in patients with dislocations were investigated.

RESULTS

The postoperative dislocation rate was 0.56 % (8 patients). The mean time to dislocation onset was 11.2 (0.5-20.0) months postoperatively. All postoperative dislocations occurred in the early phase whereas none in the late phase, showing a significant difference (p < 0.01). Six (0.43 %) patients experienced recurrent dislocations or required revision.

CONCLUSIONS

THA using the combined strategy resulted in low dislocation rates, especially without late dislocation.

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

BACKGROUND

The 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.

METHODS

This 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.

RESULTS

No 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.

CONCLUSIONS

For 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.

Assessment of Pelvic Tilt in Anteroposterior Radiographs by Area Ratio Based on Deep Learning

STUDY DESIGN

Diagnostics.

OBJECTIVES

Based on deep learning semantic segmentation model, we sought to assess pelvic tilt by area ratio of the lesser pelvic and the obturator foramen in anteroposterior (AP) radiographs.

BACKGROUND

Pelvic tilt is a critical factor in hip and spinal surgery, commonly evaluated by medical professionals through sagittal pelvic radiographs. The inherent pelvic asymmetry, as well as potential obstructions from clothing and musculature in roentgenography, may result in ghosting and blurring artifacts, thereby complicating precise measurement.

METHODS

PT directly affects the area ratio of the lesser pelvis to the obturator foramen in AP radiographs. An exponential regression analysis of simulated radiographs from ten male and ten female pelvises in specific tilt positions derived a formula correlating this area ratio with PT. Two blinded investigators evaluated this formula using 161 simulated AP pelvic radiographs. A deep learning semantic segmentation model was then fine-tuned to automatically calculate the area ratio, enabling intelligent PT evaluation. This model and the regression function were integrated for automated PT measurement and tested on a dataset of 231 clinical cases.

RESULTS

We observed no disparity between men and women in the aforementioned area ratio. The test results from two blinded investigators analyzing 161 simulated radiographs revealed a mean absolute error of 0.19° (SD ±4.71°), with a correlation coefficient between them reaching 0.96. In addition, the mean absolute error obtained from testing 231 clinical AP radiographs using the fine-tuned semantic segmentation model mentioned earlier is -0.58° (SD ±5.97°).

CONCLUSIONS

We found that using deep learning neural networks enabled a more accurate and robust automatic measurement of PT through the area ratio of the lesser pelvis and obturator foramen.

Robotic-assisted total hip arthroplasty outperforms manual technique in obese and overweight patients: a prospective comparative study

BACKGROUND

With the increasing prevalence of obesity, there is growing awareness of the impact of overweight and obesity on total hip arthroplasty (THA). Research exploring the accuracy of acetabular component orientation in THA between robotic-assisted and manual techniques across different BMI categories is insufficient.

METHODS

This prospective study evaluated 221 patients who underwent THA with a Robotic Interactive Orthopaedic Arm system and 252 patients who underwent manual THA between March 2022 and January 2024. The patients were divided into four groups according to their BMI. We analysed whether there were differences in the accuracy of acetabular component positioning between robotic-assisted THA and manual THA across different BMI categories.

RESULTS

In the overweight group, robotic-assisted THA achieved a significantly higher rate of abductions within the target range (73/6) than manual THA (62/28) (p = 0.000). Both abductions and anteversions within the target range were also significantly more frequent in the robotic-assisted THA group (69/10) than in the manual THA group (56/34) (p = 0.000). Among the obese patients, robotic-assisted THA showed a perfect record for anteversions within the target range (29/0), markedly outperforming manual THA (39/6) (p = 0.040).

CONCLUSION

In the overweight (24 kg/m² ≤ BMI < 28 kg/m²) and obese (BMI ≥ 28 kg/m²) groups, robotic-assisted THA demonstrates significantly greater accuracy in acetabular component positioning compared to manual THA. This indicates that robotic-assisted technology may provide a more precise positioning of the acetabular component in overweight and obese patients.

Correlation of Acetabular Cup Placement Angles Between an Artificial Intelligence-Powered System Using a Smartphone and Human Measurements

Background

An automated measurement system for the placement angles of acetabular cup in total hip arthroplasty prostheses was developed utilizing artificial intelligence (AI) algorithms. The AI-powered system enables immediate measurement by capturing an anteroposterior pelvic X-ray through a smartphone camera.

Methods

While developing the AI-powered measurement system, we trained AI utilizing 100 labeled anteroposterior pelvic X-rays to recognize the hip joint and 483 labeled anteroposterior pelvic X-rays to identify anatomical landmarks and the acetabular cup. To validate the AI-powered system, we measured the acetabular cup placement angles of 126 unlabeled post-total hip arthroplasty anteroposterior pelvic X-rays with both the AI-powered system and conventional measurement methods and assessed the correlation between the 2 methods.

Results

The Pearson's correlation coefficients for the acetabular cup placement angles measured using the AI-powered system and conventional method were 0.88 (95% confidence interval, 0.84-0.92, P < .001) in inclination angle and 0.76 (95% confidence interval, 0.67-0.83, P < .001) in anteversion angle, respectively.

Conclusions

Both inclination and anteversion angles measured using the AI-powered system showed a strong correlation with angles obtained through conventional methods.

Piriformis preserving posterior approach STAR for primary and primary complex total hip arthroplasty: Excellent safety and efficacy in a single blinded prospective single surgeon cohort of 522 patients with a mean follow-up of 2 years

INTRODUCTION

STAR (Superior Transverse Anatomic Reconstruction), a piriformis-preserving posterior approach, has not been extensively studied. Our study aimed to assess the STAR approach's safety and efficacy by recording postoperative complication rates and measuring implantation accuracy in a single surgeon prospective cohort with a mean follow-up of two years.

METHODS

The study involved 522 patients with elective primary or complex primary total hip arthroplasty (THA) performed by a senior surgeon using the STAR approach between 2019 and 2023. 63.6% of the patients were female. The mean patients' age was 65.6 years. 19.5% of the procedures were primary complex THAs. The mean follow-up and length of stay were 2.13 years and 1.50 days. The ratio of uncemented to hybrid and standard to dual mobility liner THAs were 3:2 and 4:1. Fifty-eight patients received blood transfusions. All patients followed the same postoperative protocol. Two physicians not involved in surgery collected clinical and radiological data. Efficacy was defined as measuring the cup inclination and anteversion, stem alignment, and leg length discrepancy (LLD) using the one-month postoperative standardised supine anteroposterior pelvic X-rays. The postoperative complication rate, including dislocation and infection, defined safety.

RESULTS

The mean cup inclination and anteversion were 42.80 (±4.9) and 19.90 (±8.9), respectively. 97.5% of the stems were placed in neutral and 2.5% in varus position. The mean LLD was 3.3 ± 6.3 mm. A single deep infection was managed with two-stage revision with no recurrence, and an early traumatic dislocation in an 80-year-old woman was managed successfully with closed reduction and hip spica. Three superficial wound infections were treated with oral antibiotics.

DISCUSSION

The STAR approach is safe and has demonstrated excellent early-to-mid-term efficacy profile outcomes. The unobstructed acetabular and femoral intraoperative view facilitated optimal implant positioning and contributed to excellent dislocation outcomes in combination with piriformis preservation.

Error of intraoperative measurement of stem anteversion is decreased by measuring in neutral hip position during total hip arthroplasty

BACKGROUND

Intraoperative stem anteversion, which is the angle between the lower leg axis and the trial-stem axis with hip flexion and adduction, is generally evaluated by the surgeon's visual estimation during total hip arthroplasty (THA). However, the conventional approach can be influenced by knee osteoarthritis or uncertain surgeon's observation point. Therefore, we developed a new method for measuring the stem anteversion angle in the neutral hip position using an original rod attached to the trial-stem perpendicular to the long axis and parallel to the stem neck. This study aimed to assess the accuracy of our method in comparison with the conventional method of measuring intraoperative stem anteversion angle.

METHODS

We measured the intraoperative stem anteversion angle in consecutive 106 hips of 106 patients who underwent cementless primary THA with a tapered wedge stem. Absolute error in the stem anteversion angle was expressed as the difference between intraoperative (common vs. neutral hip positions) and postoperative computed tomography measurements, i.e., true stem anteversion. Additionally, we investigated the factors affecting these errors.

RESULTS

The absolute error of measurement was significantly smaller in the neutral hip position than in the common position (3.0° ± 2.5° vs. 8.0° ± 3.9°; p < 0.0001). The factor associated with the error was advanced knee osteoarthritis in the common position, whereas it was not statistically significant in the neutral hip position.

CONCLUSIONS

This study suggests that the error in the intraoperative measurement of stem anteversion is decreased by measuring in the neutral hip position during THA.

Intraoperative fluoroscopic confirmation of the knee improves the accuracy of stem anteversion in total hip arthroplasty with direct anterior approach using traction table

BACKGROUND

Stem anteversion (SA) in total hip arthroplasty (THA) is crucial for postoperative outcomes, affecting dislocation risk and hip function. Accurate SA placement is challenged by intraoperative estimation methods, with discrepancies reported between predicted and true SA. This study investigates the effect of conventional methods and intraoperative fluoroscopic confirmation on SA accuracy in THA performed with a direct anterior approach using a traction table.

METHODS

This involves 200 patients undergoing primary THA from August 2019 to January 2023, divided into a conventional group (n = 100) and a fluoroscopic group (n = 100). Postoperative SA measurements were conducted using computed tomography scans. Statistical analysis focused on comparing the SA angles and the prevalence of excessive SA (≥>35° and ≥>40°) between the groups.

RESULTS

The fluoroscopic group showed a lower average SA angle (24.3° ± 8.3°) compared to the conventional group (30.0° ± 11.3°), with a statistically significant difference (p < 0.01). Excessive SA (≥>40°) was found in 17% of the conventional group, significantly reduced to 5% in the fluoroscopic group (p < 0.01). Similarly, SA exceeding 35° was present in 39% of the conventional group, compared to only 11% in the fluoroscopic group (p < 0.01), indicating a substantial reduction in excessive SA placements with fluoroscopic guidance.

DISCUSSION

The study demonstrates that intraoperative fluoroscopic guidance significantly enhances the accuracy of SA placement in THA, reducing the variability and proportion of excessive SA. This suggests a critical reevaluation of conventional estimation methods in favor of fluoroscopic confirmation to improve surgical outcomes.

CONCLUSION

Intraoperative fluoroscopic confirmation of knee external rotation angle markedly decreases the proportion of excessive SA and enhances the precision of stem placement in THA with a direct anterior approach. This technique represents a significant advancement in surgical practice, offering a simple and effective method to achieve optimal postoperative results.

Impact of Offset and Leg Length on Functional Outcomes Post-Total Hip Arthroplasty: How Accurate Should Coronal Reconstruction Be?

BACKGROUND

Accurate hip reconstruction is associated with improved biomechanical behavior following total hip arthroplasty (THA). However, whether this is associated with improved patient-reported outcomes (PROs) is unknown.

HYPOTHESIS/PURPOSE

This study aimed to: 1) describe the ability to reconstruct coronal geometry during THA without advanced technology; 2) assess whether restoration of global offset (GO) and leg length (LL) is associated with improved PROs; and 3) investigate whether increased femoral offset (FO) to compensate for reduced acetabular offset (AO) influences PROs.

METHOD

This was a prospective, multicenter, consecutive cohort study of 500 patients treated with primary THA without robotics or navigation. The Oxford Hip score (OHS) was obtained preoperatively and at 1-year follow-up. Supine anteroposterior pelvic radiographs were analyzed to determine AO, FO, GO, and LL relative to the native contralateral side. Contour plots for ΔOHS based on ΔLL and ΔGO were created, and ΔOHS was calculated within and outside various ranges (±2.5, ±5, or ±10 mm).

RESULTS

In the operated hip, mean FO increased by 3 ± 6 mm (range, -16 to 27), while AO decreased by 2 ± 4 mm (range, -17 to 10). The contour graph for ±2.5 mm zones showed the best outcomes (ΔOHS >25) with GO and LL centered on 0 ± 2.5 mm (P < .01). However, only 10% achieved such reconstruction. When GO and LL differences were within ±10 mm, ΔOHS was superior when both AO and FO were within ±5 mm (mean: 24 ± 10; range, -5 to 40) compared with when FO was above 5 mm to compensate for a reduction in AO (mean: 22 ± 11; range, -10 to 46; P = .040).

CONCLUSIONS

The PROs were associated with biomechanical reconstruction, and the best clinical improvement can be expected when GO and LL differences are both within 2.5 mm. Maintenance of AO is important, as compensation by increasing FO is associated with inferior OHS.

Assessing the Reliability of Postoperative Cross-Table Radiographs Compared to CT Scans for Measuring Acetabular Anteversion Angle Following Total Hip Arthroplasty

AIM

This study aimed to evaluate acetabular anteversion following total hip arthroplasty (THA) using cross-table lateral radiographs and CT scans and to determine the reliability of cross-table lateral radiographs compared to computed tomography (CT) scans for measuring acetabular anteversion.

MATERIALS AND METHODS

We conducted a cross-sectional study of patients undergoing THA at Justice K.S. Hegde Charitable Hospital, Deralakatte, Mangalore, from January 2020 to June 2021. Radiographs are typically taken in both anteroposterior (AP) and lateral views after THA. However, for this study, a cross-table lateral view was used instead of the usual lateral radiograph to measure the angle of anteversion. The anteversion was calculated using the method described by Woo and Morrey. Additionally, CT scans were performed on all patients as part of the study protocol. The anteversion measured in these scans was compared to that in the cross-table radiographs to assess the latter's reliability for routine use. The risk of radiation exposure from CT scans was minimized by adhering to the ALARA (As Low as Reasonably Achievable) principle, with only axial sections of the acetabular cup being scanned.

RESULTS

 The results show that the radiographic acetabular anteversion and CT scan measurements have a mean difference of 0.3036. There is a positive correlation between these measurements. The p-value is not statistically significant (p=0.698). Therefore, the measurements are correlated with each other with a linear relationship (r=0.919). For anteversion measurements using the X-ray method, the mean was 27.16 degrees with a standard deviation of ±9.49. The median was 27.26 degrees, ranging from 10.27 to 42.58 degrees. In comparison, the CT method yielded a mean anteversion of 27.40 degrees with a standard deviation of ±8.50 degrees. The median was 27.64 degrees, ranging from 12.35 to 43.11 degrees.

CONCLUSION

Cross-table lateral radiographs are a reliable and comparable method to CT scans for measuring acetabular anteversion following total hip arthroplasty.

Contribution of the Medial Iliofemoral Ligament to Hip Stability After Total Hip Arthroplasty Through the Direct Anterior Approach

BACKGROUND

Dislocation after total hip arthroplasty (THA) is a primary reason for THA revision. During THA through the direct anterior approach (DAA), the iliofemoral ligament, which provides the main resistance to external rotation (ER) of the hip, is commonly partially transected. We asked: (1) what is the contribution of the medial iliofemoral ligament to resisting ER after DAA THA? and (2) how much resistance to ER can be restored by repairing the ligament?

METHODS

A fellowship-trained surgeon performed DAA THA on 9 cadaveric specimens. The specimens were computed tomography scanned before and after implantation. Prior to testing, the ER range of motion of each specimen to impingement in neutral and 10° of extension was computationally predicted. Each specimen was tested on a 6-degrees-of-freedom robotic manipulator. The pelvis was placed in neutral and 10° of extension. The femur was externally rotated until it reached the specimen's impingement target. Total ER torque was recorded with the medial iliofemoral ligament intact, after transecting the ligament, and after repair. Torque at extremes of motion was calculated for each condition. To isolate the contribution of the native ligament, the torque for the transected state was subtracted from both the native and repaired conditions.

RESULTS

The medial iliofemoral ligament contributed an average of 68% (range, 34 to 87) of the total torque at the extreme of motion in neutral and 80% (58 to 97) in 10⁰ of extension. The repaired ligament contributed 17% (1 to 54) of the total torque at the extreme of motion in neutral and 14% (5 to 38) in 10⁰ of extension, restoring on average 18 to 25% of the native resistance against ER.

CONCLUSIONS

The medial iliofemoral ligament was an important contributor to the hip torque at the extreme of motion during ER. Repairing the ligament restored a fraction of its ability to generate torque to resist ER.

Is it feasible to develop a supervised learning algorithm incorporating spinopelvic mobility to predict impingement in patients undergoing total hip arthroplasty?

Aims

Precise implant positioning, tailored to individual spinopelvic biomechanics and phenotype, is paramount for stability in total hip arthroplasty (THA). Despite a few studies on instability prediction, there is a notable gap in research utilizing artificial intelligence (AI). The objective of our pilot study was to evaluate the feasibility of developing an AI algorithm tailored to individual spinopelvic mechanics and patient phenotype for predicting impingement.

Methods

This international, multicentre prospective cohort study across two centres encompassed 157 adults undergoing primary robotic arm-assisted THA. Impingement during specific flexion and extension stances was identified using the virtual range of motion (ROM) tool of the robotic software. The primary AI model, the Light Gradient-Boosting Machine (LGBM), used tabular data to predict impingement presence, direction (flexion or extension), and type. A secondary model integrating tabular data with plain anteroposterior pelvis radiographs was evaluated to assess for any potential enhancement in prediction accuracy.

Results

We identified nine predictors from an analysis of baseline spinopelvic characteristics and surgical planning parameters. Using fivefold cross-validation, the LGBM achieved 70.2% impingement prediction accuracy. With impingement data, the LGBM estimated direction with 85% accuracy, while the support vector machine (SVM) determined impingement type with 72.9% accuracy. After integrating imaging data with a multilayer perceptron (tabular) and a convolutional neural network (radiograph), the LGBM's prediction was 68.1%. Both combined and LGBM-only had similar impingement direction prediction rates (around 84.5%).

Conclusion

This study is a pioneering effort in leveraging AI for impingement prediction in THA, utilizing a comprehensive, real-world clinical dataset. Our machine-learning algorithm demonstrated promising accuracy in predicting impingement, its type, and direction. While the addition of imaging data to our deep-learning algorithm did not boost accuracy, the potential for refined annotations, such as landmark markings, offers avenues for future enhancement. Prior to clinical integration, external validation and larger-scale testing of this algorithm are essential.

Polyethylene liner dissociation in total hip arthroplasty: a retrospective case-control study on a single implant design

BACKGROUND

Modular acetabular components for total hip arthroplasty (THA) provide intraoperative flexibility; however, polyethylene liner dissociation may occur. This study aimed to examine the incidence and causes of liner dissociation associated with a specific acetabular component design at a single centre.

MATERIALS AND METHODS

A retrospective analysis of 7027 patients who underwent primary THA was performed to identify isolated liner dislocations. Patient demographics, clinical presentations, surgical and implant details, and both radiographic and computed tomography (CT) findings were analysed. Patients with liner dislocation were matched to a control group via 2:1 propensity score matching, and a logistic regression analysis was employed to identify associated risk factors.

RESULTS

A total of 32 patients (0.45%) experienced liner dislocation at a mean 71.47 ± 60.10 months post surgery. Significant factors contributing to dislocations included the use of a conventional compared with a highly crosslinked polyethylene component (p = 0.049) and screw fixation (p = 0.028). Radiographic and CT analysis highlighted the importance of proper component orientation, revealing that patients experiencing dislocations demonstrated significantly lower acetabular cup anteversion angles (p = 0.001) compared with the control group. Impingement and malposition, identified in 41% and 47% of the cases, respectively, further underscored the multifactorial nature of dislocation risks.

CONCLUSIONS

While the overall rate of polyethylene liner dislocation was low, the findings of this study highlight the importance of appropriate cup placement to decrease the risk of dissociation. It further substantiates the influence of impingement and malposition in liner displacement, with increased mechanical stress exerted on the locking mechanism under adverse conditions and the potential risk increase due to screw placement.

Comparison of mid-term clinical and radiological results of short and conventional femoral stems in total hip arthroplasty

This study aims to answer the question: Which are superior-conventional or short femoral stems?. An Optymis stem was used as a short-femoral stem, and an Accolade II stem was used as a conventional-femoral stem. There were 95 patients in the short femoral stem group (Group 1) and 90 in the conventional stem group (Group 2). The SF-36 Life Quality Score, thigh pain, and the Harris Hip Score were used to evaluate the patients' clinical outcomes. Pre-operative, immediate post-operative, and final follow-up x-rays were used for radiological evaluation. Stem varus/valgus alignment, hip offset changing, acetabular anteversion/inclination changing, femoral migration, acetabular migration, periarticular ossification, and osteointegration evaluation were assessed for both groups. The mean follow-up time was 5.5 years for Group 1 and 5.2 years for Group 2. No significant difference existed between the two groups in terms of clinical scores (Harris Hip Score, SF-36). Thigh pain was significantly higher in Group 2 (p = 0.0001). As for radiological parameters, Group 1 exhibited more varus position-related results. In terms of angular stability, Group 1 was found to be more unstable than Group 2 (p = 0.0001). The power to reconstruct femoral offset was superior in Group 1. Periarticular ossification was more frequent in Group 2. Femoral osteointegration was denser proximally in Group 1 and distally in Group 2. When mid-term radiological and clinical results of both femoral stems are evaluated, they have no superiority over each other.

How useful are indirect radiographic measurements of hip instability in borderline hip dysplasia? An MRI-based comparison to a healthy cohort

PURPOSE

Symptomatic hips with borderline hip dysplasia (BHD) morphology pose a challenge in differentiating stable from unstable hips. The current study aims to compare indirect radiographic signs of instability in a symptomatic BHD population to those in a healthy cohort.

METHODS

The study group consisted of patients with a lateral centre-edge angle (LCEA) with values 18° ≤ LCEA < 25° who underwent corrective periacetabular osteotomy (PAO) and reported an improvement in patient-reported outcome measures (PROMs). The comparison group consisted of a healthy cohort of athletes who did not complain of any hip-related symptoms and who had normal values of their hip morphological parameters (LCEA, acetabular index (AI°), alpha angle (α°), femoral version, acetabular version). Indirect signs of instability consisting of the femoro-epiphyseal acetabular roof index (FEAR), iliocapsularis-to-rectus-femoris (IC/RF) ratio and labral dimensions (height-to-length ratio) were assessed in both groups. Partial Pearson correlation, logistic multiple regression analysis and Receiver-Operating Characteristic (ROC) curve analysis were performed to determine correlations, as well as the sensitivity and specificity of these signs to differentiate between healthy hips and BHD.

RESULTS

On binary logistic multiple regression analysis, the FEAR Index was the only independent predictor to differentiate between BHD and healthy hips (p < 0.001). The IC/RF ratio did not achieve significance. The calculated area under the curve (AUC) was 0.93 (0.87 - 0.99, CI 95%, p < 0.001) for the FEAR Index and 0.81 (0.70 - 0.92, CI 95%, p < 0.001) for the height-length ratio. Using the predefined cut-off values (dysplastic-FEAR Index ≥ 5° or labral height-to-length ratio ≤ 0.5), 27% sensitivity/100% specificity and 20% sensitivity/ 100% specificity, were achieved. ROC analysis provided the following new thresholds: FEAR Index ≥ -5° (73% sensitivity/97% specificity); labral height-to-length ratio ≤ 0.8 (70% sensitivity, 79% specificity).

CONCLUSION

In our cohort, the FEAR index was an independent parameter that could differentiate between borderline dysplastic and asymptomatic hips. The previously published values for both the FEAR index and labral hypertrophy ratio had a poor sensitivity in differentiating symptomatic unstable BHD from healthy hips. The cut-off values of ≥ -5° (FEAR index) and ≤ 0.8 (labral height-to-length ratio) provided acceptable sensitivity and specificity when comparing to morphological healthy hips.

Robotic Arm-Assisted System Improved Accuracy of Cup Position and Orientation in Cementless Total Hip Arthroplasty for Dysplastic Hips: A Comparison Among Groups With Manual Placement, Computed Tomography-Based Navigation, and Robotic Surgery

Background

Accurate cup placement in total hip arthroplasty (THA) for patients with dysplasia is challenging due to the distinctive bone deformities. This study aimed to compare the accuracy of cup placement position and orientation across robotic arm-assisted systems (R-THA), computed tomography-based navigation (N-THA), and manual procedure (M-THA) in THA for osteoarthritis secondary to dysplasia.

Methods

A total of 167 patients (197 hips), including 88 R-THAs, 45 N-THAs, and 46 M-THAs, were analyzed. Propensity score matching was performed to align the patient backgrounds. Horizontal and vertical centers of rotation were measured for cup position, whereas radiographic inclination and anteversion were measured for cup orientation. The proportion of cases with cup placement within 3 mm and 5° from the target was compared.

Results

R-THA had a significantly higher percentage of cup placement within 3 mm of the target compared to N-THA (78% vs 49%; P = .0041) and M-THA (78% vs 53%; P = .013). Similarly, R-THA was significantly more successful in placing the cup within 5° of the target compared to N-THA (84% vs 58%; P = .0049) and M-THA (91% vs 20%; P < .0001). Moreover, N-THA was significantly better at placing the cup within 5° of the target compared to M-THA (62% vs 14%; P < .0001), whereas there was no significant difference in the percentage of cup placement within 3 mm of the target (51% vs 51%; P = 1.0).

Conclusions

Robotic arm-assisted system and computed tomography-based navigation improved accuracy in cup orientation compared to the manual procedure. Additionally, the robotic arm-assisted system further improved cup position accuracy.

A Novel Device for Intraoperative Measurement of Stem Anteversion Angle in Total Hip Arthroplasty

Background

Stem anteversion plays a crucial role in mitigating postoperative complications in total hip arthroplasty (THA). The application of the combined-anteversion theory in THA necessitates the intraoperative measurement of the stem anteversion angle (SAA). However, estimating SAA intraoperatively poses challenges for surgeons lacking a computer-assisted navigation system. In this study, we assessed the precision of intraoperative SAA measurements using a recently developed device, comparing them with 3-dimensional measurements obtained from postoperative computed tomography.

Methods

We examined 127 hips in 127 patients who underwent unilateral THA at our institution. Employing our newly constructed device, attachable to rasping broach handles, we measured the SAA intraoperatively. This process involved incorporating the correction angle derived from the preoperative epicondylar view. We then compared the postoperative SAA with the intraoperative measurements, both with and without the correction angle, to ascertain the device's utility.

Results

The device yielded an intraoperative SAA measurement of 17.93 ± 7.53°. In contrast, the true SAA measured on postoperative computed tomography was 26.40 ± 9.73°. The discrepancy between intraoperative and true SAA was 8.94 ± 5.44° (without the correction angle) and 4.93 ± 3.85° (with the correction angle). Accuracy within a discrepancy of <5° was achieved in 77 cases (60.6%), and <10° was achieved in 113 cases (89.0%). The accuracy remained consistent regardless of the stem-placement angle (varus/valgus, or flexion/extension) or the presence of ipsilateral knee osteoarthritis.

Conclusions

The SAA-measuring device, attachable to various rasping handles, proves useful for straightforward, cost-effective, and noninvasive intraoperative SAA measurement during THA.

Spinopelvic interactions in total hip arthroplasty: 295 patients followed for a minimum follow-up of 10 years

BACKGROUND

Concurrent spinal pathology is frequent in patients undergoing total hip arthroplasty (THA). In this study we examined whether spinopelvic interactions affect THA outcomes at a minimum follow-up of 10 years.

PATIENTS AND METHODS

295 patients with a mean age of 63.3 (range 56‒80) years receiving a THA between 2006 and 2009 were assessed. Of these, 195 had mild lumbar disc degeneration and 100 had advanced lumbar spondylosis. We analysed the changes in the Harris Hip Score (HHS) and the survival rate for postoperative low back pain (LBP) and dislocation. Changes in acetabular component position, sacro-femoral-pubic (SFP) and pelvic obliquity (PO) angles were assessed with radiological images.

RESULTS

The mean HHS was lower in female patients (p = 0.009), patients >65 years of age (p < 0.001) and those with advanced lumbar spondylosis (p = 0.002). 52 (71.2%) of the patients reporting preoperative LBP experienced improvement after THA while 47 (21.1%) of those without preoperative LBP postoperatively reported new onset LBP. Female patients (p = 0.025; hazard ratio [HR]: 1.831; 95% CI, 1.081-3.101) and those with preoperative LBP (p = 0.007; HR 2.068; 95% CI, 1.221-3.504) were at a higher risk of developing postoperative LBP at 10 years. 4 out of 9 THA dislocations were late and had shown decreasing SFP angle values over time. Acetabular component inclination and anteversion angles increased over time, whereas the SFP angle was associated with sex and age and the PO angle with age and the severity of any preoperative lumbar degeneration.

CONCLUSIONS

Concurrent spinal pathology influences THA outcomes at a minimum follow-up of 10 years. Sex, age, and associated lumbar degeneration can affect clinical and radiological changes over time. A decrease in SFP angle values over time was found in patients sustaining late dislocation.

Long-term follow-up of total hip arthroplasty using polyethylene-ceramic composite (sandwich) liner

INTRODUCTION

Ceramic-on-ceramic bearings have been widely used since their introduction in the 1970s. First-generation ceramics have very high fracture (breakage) rates. To overcome this, in the 1990s, modular cotyloid insert designs were developed, consisting of a ceramic and polyethylene composite (sandwich-type) liner; however, high implant fracture rates were observed in the medium term. We aimed to estimate the cumulative incidences of revision surgery (implant failure) and implant failure due to fractures, survival rates (time-to-revision surgery and time-to-fracture), and the long-term clinical and radiological outcomes in our series.

METHODS

This was an observational, longitudinal, ambispective, single-centre study based on patients who underwent primary total hip arthroplasty (THA) using a sandwich-type liner (Cerasul), only available in our tertiary hospital between January 1999 and December 2002. Cumulative incidences were estimated and the 95% confidence interval (95% CI) was calculated. The Kaplan-Meier method was used to assess the time-to-revision surgery and time-to-fracture.

RESULTS

54 patients (49 men) were included, accounting for 59 sandwich-type linear implants. The mean (range) age was 47.4 (22-57) years. The primary THA indications were osteoarthritis (28 patients), osteonecrosis (14), childhood pathology sequelae (11), and inflammatory arthritis (6). The cumulative incidence of revision surgery by implants was 8.5% (5/59, 95% CI, 3.5-19.2%), 9.3% by patients (5/54, 95% CI, 4.0-19.9%), and 5.1% by implant fractures (3/59, 95%CI, 1.7-13.9%). The median (Interquartile Range, IQR) time-to-revision surgery was 158 (72.5-161) months, and the time to fracture was 182 (138-215) months. All primary THAs had good clinical and long-term survival outcomes. All implants had signs of solid fixation.

CONCLUSIONS

After a 20-year follow-up period, the polyethylene-ceramic sandwich-type liner showed a long survival rate and low cumulative incidence of implant fracture; however, implant fractures remain the main complication. Orthopaedic surgeons should be aware that some patients still have this type of prosthesis and must be capable of responding quickly if a fracture occurs.

Stem anteversion is not affected by proximal femur geometry in robotic-assisted total hip arthroplasty

BACKGROUND

In the present study, the surgeon aimed to align the stem at 5° to 25° in anteversion. The robotic technology was used to measure stem anteversion with respect to proximal femur anteversion at different levels down the femur.

METHODS

A total of 102 consecutive patients underwent robotic-arm-assisted total hip arthroplasty (RTHA). 3D CT-based preoperative planning was performed to determine femoral neck version (FNV), posterior cortex anteversion (PCA), anterior cortex anteversion (ACA), and femoral metaphyseal axis anteversion (MAA) at 3 different levels: D (10 mm above lesser trochanter), E (the midpoint of the planned neck resection line) and F (head-neck junction). The robotic system was used to define and measure stem anteversion during surgery.

RESULTS

Mean FNV was 6.6° (SD: 8.8°) and the mean MAA was consistently significantly higher than FNV, growing progressively from proximal to distal. Mean SV was 16.4° (SD: 4.7°). There was no statistically significant difference (P = 0.16) between SV and MAA at the most distal measured level. In 96.1% cases, the stem was positioned inside the 5°-25° anteversion range.

CONCLUSIONS

Femoral anteversion progressively increased from neck to proximal metaphysis. Aligning the stem close to femoral anteversion 10 mm above the lesser trochanter often led to the desired component anteversion.