Hip Center Research Articles

Application of Intraoperative Individualized Cup Combination—Cup‐on‐Cup Technique in Severe Acetabular Defects

This study aimed to investigate the application of the cup‐on‐cup technique in revision total hip arthroplasty (THA) and report clinical and radiographic outcomes from a series of case follow‐ups. Retrospective analysis of 10 patients who underwent acetabular prosthesis revision with cup‐on‐cup technique. According to the Paprosky classification of acetabular bone defects, there were 2 cases of type II C, 3 cases of type III A, and 5 cases of type III B. The average follow‐up was 54.8 ± 5.1 months, and the Harris score of the hip joint increased from 37.0 ± 9.9 preoperatively to 80.5 ± 3.1 postoperatively at the final follow‐up (p < 0.001). Comparing the surgical side's hip center of rotation (COR) to the contralateral side, the preoperative average upward displacement was 33.8 ± 15.0 mm, while the postoperative average upward displacement was 0.2 ± 3.3 mm (p < 0.001). Similarly, the preoperative average inward displacement was 9.1 ± 5.1 mm, while the postoperative average outward displacement was 1.8 ± 1.6 mm (p < 0.001). There was no significant difference (p = 0.71) between the average density values of the contralateral and surgical sides at the final follow‐up, which were 127.4 ± 13.7 and 125.0 ± 14.8, respectively. During the follow‐up period, all patients achieved satisfactory radiographic outcomes, and no prosthetic loosening was observed. The cup‐on‐cup technique can reconstruct acetabular bone defects and restore hip COR in revision THA, with favorable clinical and radiographic outcomes.

The application and effect of bispherical augment in acetabular defects reconstruction

Objective: To evaluate the clinical effect of bispherical augment in acetabular defects reconstruction in hip revision. Methods: This is a retrospective case series study. A retrospective analysis of 119 patients (124 hips) patients who underwent hip revision surgery and reconstructed with bispherical augment for acetabular bone defects from January 2019 to December 2023 was performed. There were 57 males (58 hips) and 62 females (66 hips), aged (65.0±11.8) years (range:40 to 102 years). The body mass index was (23.9±3.5) kg/m2 (range:16.1 to 32.2 kg/m2). Acetabular bone defects were typed as follows: 2 hips in Paprosky type ⅡA, 29 hips in type ⅡB, 34 hips in type ⅡC, 31 hips in type ⅢA, and 28 hips in type ⅢB, of which 9 patients (9 hips) were combined with pelvic discontinuity. Differences in Harris hip score (HHS) and lower limb discrepancy (LLD) were compared between preoperatively and final follow-up. The height of the hip center of rotation and the horizontal distance from the center of rotation to the teardrop were measured by radiographs before and after surgery, and prothesis stability and the occurrence of postoperative complications were evaluated. Data were compared using the paired sample t test. Results: All patients successfully completed the operation. The operation time was (167.0±53.4) minutes (range:90 to 380 minutes) and the intraoperative bleeding was (345.3±124.2) ml (range:100 to 1 200 ml). The height of the hip center of rotation decreased from (39.7±13.0) mm preoperatively to (21.8±7.1) mm postoperatively and the horizontal distance from the center of rotation to the teardrop increased from (34.0±10.1) mm preoperatively to (38.5±5.9) mm postoperatively, and the differences were statistically significant (t=15.859, P<0.01; t=5.266,P<0.01). All the patients were followed up for (26.1±15.4) months (range:6 to 60 months). At the last follow-up, HHS improved from (35.2±10.0) points preoperatively to (85.5±9.5) points, and the difference was statistically significant (t=50.723,P<0.01). LLD decreased from (2.1±1.1) cm preoperatively to (0.5±0.5) cm, and the difference was statistically significant (t=13.767, P<0.01). All acetabular components were stable and free of displacement on imaging during follow-up. Three patients suffered dislocation and received closed reduction, all prosthesis were in good position during follow-up. No dislocation, loosening, fracture, recurrence of infection and vascular nerve injury occurred in other patients. Conclusion: Bispherical augment can effectively reconstruct acetabular bone defects, restore the hip center of rotation, and improve hip joint function scores at short and mid-term follow-up.

Increased force and elastic energy storage are not the mechanisms that improve jump performance with accentuated eccentric loading during a constrained vertical jump.

Accentuated eccentric loading (AEL) involves higher load applied during the eccentric phase of a stretch-shortening cycle movement, followed by a sudden removal of load before the concentric phase. Previous studies suggest that AEL enhances human countermovement jump performance, however the mechanism is not fully understood. Here we explore whether isolating additional load during the countermovement is sufficient to increase ground reaction force, and hence elastic energy stored, at the start of the upward movement and whether this leads to increased jump height or power generation. We conducted a trunk-constrained vertical jump test on a custom-built device to isolate the effect of additional load while controlling for effects of squat depth, arm swing, and coordination. Twelve healthy, recreationally active adults (7 males, 5 females) performed maximal jumps without AEL, followed by randomised AEL conditions prescribed as a percentage of body mass (10%, 20%, and 30%), before repeating jumps without AEL. No significant changes in vertical ground reaction force at the turning point were observed. High load AEL conditions (20% and 30% body weight) led to slight reductions in jump height, primarily due to decreased hip joint and centre of mass work. AEL conditions did not alter peak or integrated activation levels of the knee extensor muscles. The constrained movement task used here, which excluded potential contributions of trunk motion, arm swing, rate of descent, squat depth, and point of load application, allows the conclusion that increased elastic energy return is not the primary mechanism for potentiating effects of AEL on jump performance.

Impact of Xsens Technology on Analysis of Gait Deviation in Pre- and Post-surgical Total Knee Arthroplasty Patient.

Introduction Osteoarthritis (OA) is a degenerative joint ailment that predominantly affects the knee and is most common in older adults. It destroys the surrounding tissues and cartilage. Following total knee arthroplasty (TKA), patients with end-stage knee OA can have long-term pain reduction and patient satisfaction, although certain functional limitations still exist. While TKA significantly reduces pain and improve function, many patients stillexperience abnormalities post-surgery, such as slower walking and reduced step-length. Gait analysis using technologies like the Xsens Motion Visualization and Navigation (MVN) system (Movella, Henderson, NV, USA)provides insights into these functional limitations, helping to assess knee mobility and predict changes in joint movements during activities. Methods Thirty-four people participated in a study done at the Centre for Advance Physiotherapy Education and Research, Ravi Nair Physiotherapy College, Wardha, both before and after total knee arthroplasty. Participants who ranged in age from 50 to 70 and had undergone unilateral TKA were included. Informed consent was obtained, and demographic data were collected. Participants walked a predetermined distance at their usual speed, and measurements of hip and knee angular velocity and center of mass were recorded for gait analysis. Result The study involved participants aged 50-70, with a mean age of 59.79 years and height ranging from 153.00 to 185.00 cm. Significant gait changes were noted pre- and post-total knee arthroplasty, including a decrease in walking speed from 0.72 to 0.55m/s and cadence from 105.06 to 82.86. Other parameters, such as step length and center of mass, also exhibited considerable differences, highlighting the impact of TKA on gait dynamics. Conclusion The study underscores the significant impact of total knee arthroplasty on gait mechanics and the value of advance of technologies likeXsens for assessing functional outcomes. While TKA provides pain relief and improved mobility, residual gait abnormalities persist, highlighting the need for tailored rehabilitation. Xsens technology enhances patient preparation, recovery tracking, and rehabilitation strategies, setting a new standard for gait analysis in orthopedic practice.

Do the porous custom implants have a position consistent with the planning and allow anatomical reconstruction of hip center of rotation in complex acetabular revisions Paprosky III?

IntroductionIn revision total hip arthroplasty (THA), the advent of porous custom-made triflange acetabular implants with 3D scan planning offers a new perspective to improve implantation accuracy and anatomical restoration of the center of rotation (COR). This issue was investigated using CT-scan as the measurement tool, but in limited series (±10 cases) and without investigating the factors that may influence errors in positioning. Therefore we performed a retrospective study aiming to: (1) assess the placement accuracy of such implants with respect to the preoperative planning, (2) examine whether the volume of bone to be resected in order to apply the implant had an impact on this accuracy, (3) assess if errors in position at surgery had any influence on function, complications and survival. HypothesisPreoperative planning could be accurately reproduced when implanting porous custom-made acetabular implants, and that accuracy would decrease in proportion to the volume of bone to be resected MethodTwenty patients undergoing THA revision with porous custom-made acetabular implants were included in this single-center retrospective study. Mean follow-up was 17.9 months ± 9.4 [2–45.1]. Preoperative planning was performed using 3D scanographic modeling. A post-operative CT scan was performed to assess implantation accuracy in terms of orientation and COR restitution. Demographic data, Oxford scores, complications and survival were recorded. ResultsMean deviation from the preoperative planning in inclination, anteversion and rotation were 4.3 ° ± 2.5, 6.1 ° ± 4.7, and 7 ° ± 4.6, respectively. Restoration of the COR showed a mean deviation of 2.1 ± 1.3 mm anteroposteriorly, 2.5 ± 2 mm mediolaterally and 2.2 ± 1.3 mm proximodistally. In total, 45% (9/20) of implants were positioned with perfect restoration of orientation (±10 °) and COR (±5 mm). The mean planned bone resection was 8.1 ± 4.9 cm3, with placement accuracy and COR restitution decreasing significantly when the volume of bone to be resected exceeded 2.7 cm3. One dislocation was found (5%, 1/20). Survival at last follow-up was 100%, the mean Oxford score at follow-up was 31.7 ± 7.9 [16–52], without being influenced by errors in position or COR restitution. ConclusionIn total 45% of the implants restored an orientation and a COR as planned, particularly when the volume of bone to be resected is less than 2.7 cm3. Although these are complex cases with large amounts of bone loss, 3D manufacturing could give us hope of greater precision. The link between better precision and low bone resection volume could be an area to develop with the manufacturer in order to improve results. Level of evidenceIII; diagnostic using CT in transversal retrospective study

An Intraoperative Technique to Assess Tissue Tension and Leg Length When Aligning the Hip Centre of Rotation With the Acetabulum in Hip Arthroplasties.

Hip arthroplasties are cost-effective procedures; however, instability and leg length discrepancy are common complications that can lead to higher revision rates and patient dissatisfaction. Preoperative planning aids surgeons in choosing the right offset and neck length before surgery. Nonetheless, intraoperative measures are still necessary due to the differences dictated by the surgical procedure. Several hip trials might be needed to reach the optimum choice of implants. We have introduced a technique that utilizes the trunnion as a reference point to the hip centre of rotation, matching it with the acetabulum centre of rotation after applying the necessary soft tissue tension. This serves as a proximal reference point. Using the trunnion, as opposed to the trial head, allows for a better assessment of tissue tension within the acetabular void, avoiding constraints imposed by the applied trial head. Additionally, determining the acetabulum's centre of rotation is challenging if obscured by the trial head. Matching the two tibial tuberosities indicates the correct leg length, serving as the distal reference point. Both reference points should be considered together to select the right neck length and offset for optimal tissue tension. This technique has been tested on hip arthroplasty patients over five years. All hip surgeons who used this technique agree that it gives a better representation of the tissue tension, easing the challenges when preparing the acetabulum as well as reducing the need for multiple trials.

Trabecular Metal Augments for Reconstruction of Acetabular Bone Defects in Revision Total Hip Replacement: Short-Term Outcomes

Abstract Background: Revision hip surgeries are increasing dramatically nowadays, and achieving hip center of rotation is challenging. Obtaining a press-fit implant and restoring the hip’s center of rotation might be difficult during the restoration of acetabular deformities during revision total hip arthroplasty (THA). Aim: The aim of the study was to evaluate the outcomes of using trabecular metal augments for reconstruction of the acetabulum in patients undergoing revision THA with short-term follow-up. Patients and Methods: This study was conducted in Benha University Hospital between April 2019 and March 2023. It is a prospective cohort study including 20 patients who are undergoing revision THA with acetabular defects. Results: The mean age of patients in this study was 59 years old. According to Paprosky classification: 45% of type 2B. The postoperative Oxford Hip Score showed marked improvement in the outcomes, the score was excellent in 55% (11 patients), good in 40% (8 patients), and fair in only 5% (1 patient) over 16 months’ mean follow-up period. Conclusion: Due to its modularity, tantalum augments are considered a valuable method in the reconstruction of acetabular defects.

Poster 197: A 3D Analysis of Hip Center of Rotation Trajectory and its Effects on Impingement-Free Range of Motion: A Dynamic Analysis of 1222 Hips

Objectives: Traditionally, the hip has been thought of as a particularly stable ball and socket joint with a fixed center of rotation and no translation. This view has been the basis for several simulation platforms studying hip impingement and instability for treatment planning and outcome analyses. More recently, in vivo imaging and cadaveric studies have suggested that, in addition to rotation, the femoral head and center of rotation (COR) translate within the joint throughout physiologic range of motion. A recent MRI study has shown an average translation of 2 mm, with up to 7 mm translations in certain positions, among subjects with asymptomatic hips. Importantly, substantial magnitudes of translation can alter hip contact and impingement patterns with downstream effects on the treatment planning and patient outcomes. However, there is a paucity of literature regarding how hip translation may influence hip impingement. Therefore, the purpose of this study was to use a validated simulation platform, capable of simulating hip translation during impingement analysis, to map the trajectory of the hip COR and its effects on impingement-free hip range of motion (ROM). Methods: Following institutional review board approval, the New Mexico Decedent Image Database (NMDID) was queried to identify computed tomography scans with full coverage of the hip and femur from subjects with no documented bone and joint pathology (n = 1222 hips, 611 patients, age: 30.4 ± 8.8; 67% male patients). A custom-developed and validated program (VirtualHip, Boston Children’s Hospital) was used to automatically segment the bones, identify landmarks (Dice 0.94 – 0.99), and define an anatomical coordinate system based on International Society of Biomechanics (ISB) recommendations. The pelvis was then fixed in 3D and the femur was moved to simulate uniplanar rotations (ie, flexion: 0° to 150°, extension: 0° to 50°, abduction/adduction: 0° to 75°, internal /external rotations: 0° to 75°). The simulations were first done assuming a fixed hip COR (no translation) and then repeated by incrementally allowing the hip COR to translate by up to 5 mm with increments of 1 mm, avoiding bone-to-bone penetration or hip dislocation (distance between the femoral head and acetabulum exceeding the joint space width measured at neutral). Mixed linear models were used to evaluate the relationships between COR translation and impingement-free rotation (maximum rotation prior to impingement). The effect of translation on ROM was characterized by calculating the proportion of hips able to achieve each ROM. Finally, the path of the hip COR was mapped throughout the tested ranges of motion. Results: The effect of COR translation on achieved impingement-free range of motion along with COR trajectories are shown in Figure 1. Hip flexion was associated with COR posterior (by 4.0 ± 0.9 mm), lateral (only after 100°, by 3.6 ± 1.4 mm), and superior (only after 100°, by 2.0 ± 1.8 mm) translations (P &lt; 0.001). Hip extension was only associated with anterior COR translation (by 0.8 ± 0.7 mm, P &lt; 0.001). Hip adduction was associated with anterior (by 2.9 ± 1.3 mm), lateral (by 4.0 ± 1.3 mm), and superior (by 4.4 ± 0.6 mm) translations (P&lt;0.01). Hip abduction was only associated with medial (by 2.6 ± 1.5 mm) and inferior (by 2.9 ± 1.7 mm) translations (P &lt; 0.02). There were minimal COR translations during hip internal rotation (P &gt; 0.05). Hip external rotation was associated with anterior (by 3.7 ± 1.4 mm) and inferior (by 1.2 ± 1.3 mm) translations (P &lt; 0.05). Conclusions: This is the first study to map the hip COR trajectory under common movements in a large cohort of patients. The current findings highlight the importance of hip translation (nonfixed COR) on physiologic hip range of motion. As the hip is not a perfect ball and socket joint, with an aspherical femoral head, translation is required to accommodate physiologic rotation (ie, glide mechanism) without bony impingement between the femur and pelvis. These preliminary observations highlight the need for a comprehensive assessment of normal and pathologic hip translation along with their role in biomechanics, injury risk, and response to treatment. A clear understanding of the role of hip translation in hip function and health will improve clinical care through better diagnosis and personalized treatment planning, which can ultimately lead to improved treatment outcomes, particularly lower risk of osteoarthritis. [Figure: see text]

Is Preoperative Weight Reduction in Patients Who Have Body Mass Index ≥ 40 Associated With Lower Complication Rates After Primary Total Hip Arthroplasty?

BackgroundGiven the heightened risk of postoperative complications associated with obesity, delaying total hip arthroplasty (THA) in patients who have a body mass index (BMI) > 40 to maximize preoperative weight loss has been advocated by professional societies and orthopaedic surgeons. While the benefits of this strategy are not well-understood, previous studies have suggested that a 5% reduction in weight or BMI may be associated with reduced complications after THA. MethodsWe identified 613 patients who underwent primary THA in a single institution during a 7-year period and who had a BMI >40 recorded from 9 to 12 months prior to surgery. Subjects were stratified into 3 cohorts based on whether their baseline BMI decreased by >5% (147 patients, 24%), was unchanged ( ± 5%) (336 patients, 55%), or increased by >5% (130 patients, 21%) on the day of surgery. The frequency of 90-days Hip Society and Centers for Medicare & Medicaid Services complications was compared between these cohorts. There were significant baseline differences between the cohorts with respect to baseline American Society of Anesthesiologists class (P < .001) and hemoglobin A1C (P = .011), which were accounted for in a multivariate regression analysis. ResultsIn univariate analysis, there was a lower incidence of readmission (P = .025) and total complications (P = .005) in the increased BMI cohort. The overall complication rate was 18.4% in the decreased BMI cohort, 17.6% in the unchanged cohort, and 6.2% in the increased cohort. However, multivariable regression analysis controlling for potential confounders did not find that preoperative change in BMI was associated with differences in 90-days complications between cohorts (P > .05). ConclusionsPatients who have a BMI >40 and achieved a clinically significant (>5%) BMI reduction prior to THA did not have a lower risk of 90-days complications or readmissions. Thus, delaying THA in these patients to encourage weight loss may result in restricting access to a beneficial surgery without an appreciable safety benefit.

Functional outcomes and center of rotation restoration in total hip arthroplasty after acetabular fracture: A review of 367 hips

BackgroundTotal hip arthroplasty (THA) after acetabular fracture is typically performed months or years later for posttraumatic arthritis after initial conservative treatment. But THA can be performed earlier after open reduction and internal fixation (ORIF) of the fracture. The aim of this study was to determine which strategy is best. The primary outcome measure was the radiological restoration of the hip's center of rotation (COR). The secondary outcome measures were the incidence of complications and the hip's functional scores. Materials and methodsA multicenter cohort was analyzed by splitting patients into three groups: group A (THA within 3weeks of fracture); group B (THA deferred after early ORIF); group C (THA more than 3weeks after fracture, without ORIF). Group B was separated into two subgroups: B- (THA less than 1year after ORIF) and B+ (THA more than 1year after ORIF). The demographics, surgical techniques, COR superior and lateral migration coefficient and functional scores (HHS, HOOS-PS and FJS) were recorded. The functional scores were gathered using PROMs. ResultsIn all, 367 patients were included: 108 in group A, 69 in group B-, 113 in group B+ and 77 in group C. The mean follow-up was 5.8years [3.4 months-35years]. The mean age of the patients was 69.2years [SD 15; 26-101], 52years [SD 16; 19-83], 49years [SD 16; 16-85] and 58.1years [SD 17; 13-94], respectively (p<0.01). The mean ASA score was 2.13 [SD 0.70], 1.84 [SD 0.65], 1.67 [SD 0.63] and 1.79 [SD 0.60], respectively (p<0.01). A complex Letournel fracture was present in 63 patients (61%), 46 patients (71%), 48 patients (49%) and 38 patients (62%), respectively (p<0.01). A reinforcement cage was implanted in 38 patients (69%), 16 patients (62%), 5 patients (12%) and 19 patients (66%), respectively (p<0.01). Cement was used in 45 patients (45%), 23 patients (35%), 19 patients (18%) and 21 patients (32%), respectively (p<0.01). A graft was needed in 46 patients (46%), 35 patients (53%), 17 patients (16%) and 21 patients (48%), respectively (p<0.01). Posterior ORIF was done in 40 patients (46%), 32 patients (55%), 64 patients (61%) and 9 patients (82%), respectively (p<0.01). The COR lateral migration coefficient was significantly higher in group C with a mean of +0.17 (SD 0.85) [-0.27 to +6] compared to the other groups (p=0.02). The COR superior migration coefficient was comparable between groups, with a mean of +0.77 (SD 2.26) [-0.99 to 27], p>0.05. There were complications in 10 patients (9.2%), 6 patients (8.7%), 6 patients (5.3%) and 3 patients (3.9%), respectively, with no significant difference between groups. The PROMs were completed by 51% of patients. At the final review, the mean HHS was 79.2 (SD 21.8) and the mean HOOS-PS was 77.7 (SD 20.1) in the entire cohort, p>0.05. The mean FJS by group was 55.9 (30.2), 47.7 (SD 36.4), 66.1 (SD 30.4) and 65.8 (SD 30.3), respectively (p=0.02). Discussion and conclusionThe B strategy (B+) yielded good outcomes in terms of function and COR restoration. When using this strategy, anterior ORIF preserves the native hip for a subsequent THA through a posterior approach. Strategy C also produces good functional outcomes but shifts the COR laterally. This study confirms the poor results of strategy A in previous publications. When the prognosis is poor, immediate mobilization after anterior ORIF followed by THA within 1year appears to be a good strategy (group B-). Level of evidenceIV, observational study.

Outcomes of a Double-Cup Construct to Treat Paprosky 3A and 3B Acetabular Defects at a Mean of 39 Months

BackgroundModular reconstruction systems based on porous tantalum (PT) prosthetic components have been increasingly used for the treatment of complex acetabular bone defects in revision total hip arthroplasty. We report a novel technique that applies a revision cup as a “super-augment” to form a “double-cup” construct for Paprosky type III defects. MethodsA retrospective review was conducted on revision total hip arthroplasty cases, comparing those treated with double-cup constructs (DC group, n = 48) to those treated with PT shells and augments (PT group, n = 48). All procedures were performed at the same institute between 2017 and 2022. Clinical outcome evaluation utilized the Harris Hip Score, Oxford Hip Score, and the 36-Item Short Form Survey. Preoperative and postoperative radiographic assessments measured hip center of rotation (COR) position and leg length discrepancy. Additionally, postoperative complications and implant survivorship were monitored during the follow-up period. ResultsThe clinical outcomes improved substantially in both groups, which showed no significant difference in the Harris Hip Score (P = .786), the Oxford Hip Score (P = .570), and the 36-Item Short Form Survey (P = .691). Compared to the PT group, the reconstruction COR was significantly closer to the anatomic COR (vertical distance: 2.630 versus 7.355 mm, P = .0034; horizontal distance: 1.881 versus −6.413 mm, P < .0001) in Paprosky 3B type defects. Additionally, postoperative leg length discrepancy was less in the DC group (−8.252 versus −1.821 mm, P = .0008). Dislocation was the main complication in the DC group, and only 1 patient received re-revision due to repeated dislocation. The cumulative survival rate of the DC group (100%; 95% confidence interval 100) was better than the PT group (83.4%; 95% confidence interval 70.5 to 98.6) when re-revisions for aseptic loosening were the endpoint (P = .046). ConclusionsThe DC is a reliable revision technique for the reconstruction of Paprosky type III bone defects. Although dislocation remains challenging, the biomechanically superior restoration achieved by this technique lowers the risk of aseptic loosening.

EARLY TO MID-TERM OUTCOMES OF THE CUSTOM-MADE 3D-PRINTED TRIFLANGE ACETABULAR COMPONENT (AMACE) IN COMPLEX REVISION HIP ARTHROPLASTY: LARGEST UK STUDY REPORTING THE COMBINED EXPERIENCE OF TWO TERTIARY REVISION CENTRES

Different techniques have been described to address massive bone loss of the acetabulum in revision hip surgery. aMace has gained popularity as it provides customization aiming to restore hip centre and provide good initial stability in cases of large non-contained defects. It takes into account quality of host bone. Its porous defect filling scaffold provides an excellent surface for osteointegration.Our aim was to assess the short and mid-term outcomes of patients who underwent revision surgery using aMace system.Ethical approval was obtained. A retrospective study included all patients who had aMace between June 2013 and October 2022 allowing for a minimum of 12-months follow-up. Patients’ demographics, indication, bone-loss severity, reconstruction details, re-operation, complications, mortality, pain and function were assessed.52 cases were performed by 13 surgeons with median 51 months follow-up. Median age was 72.7 years. 86.5% were female. Average BMI was 25.3. Average ASA grade was 3.65% were classified as Paprosky IIIB and 32% were IIIA.73% were found to have poor bone quality on CT. Main indication for aMace was massive bone loss/discontinuity secondary to aseptic loosening in 88.5%.77% underwent single-stage revision. 53.8% had 2 or more previous revisions. 71% underwent stem revision in the same setting. 77% received a dual mobility bearing.Re-operation rate was 5.7% for instability and femoral PPF. LLD was reported in 9.6%.Permanent Sciatic nerve palsy occurred in 3.8% of the cases.30-days mortality was 1.9%.Statistically significant post-op improvements in pain and mobility were reported (p&lt;0.001). None of the acetabular components have been revised.Our study shows satisfactory surgical outcomes with a relatively low complication rate and significant pain and mobility improvements in the early to mid-term stages.We recommend these costly cases to be done in highly specialist centres adopting MDT approach.

Impact of model geometry and joint center locations on inverse kinematic/dynamic predictions: A comparative study of sexually dimorphic models

This work illustrates the sensitivity of demographically characteristic body segment inertial properties and subject-specific customization on model performance. One characteristic demographic, gender, and one subject-specific characteristic, hip joint center location, were represented with musculoskeletal modeling to evaluate how design decisions may alter model outputs. Generic sexually dimorphic musculoskeletal models were developed from the commonly used Rajagopal model using male and female data adapted by Dumas et al. Hip joint centers of these models were adjusted based on functional joint center testing. The kinematics and dynamics of 40 gait cycles from four subjects are predicted using these models. Two-way analysis of variance (ANOVA) was performed on the continuous time series data using statistical parametric mapping (SPM) to assess changes in kinematics/dynamics due to either choice in model (Rajagopal vs Dumas) or whether joint center adjustment was performed. The SPM based two-way ANOVA of the inverse dynamics found that differences in the Rajagopal and Dumas models resulted in significant differences in sagittal plane moments during swing (0.115 ± 0.032 Nm/kg difference in mean hip flexion moment during initial swing and a 0.077 ± 0.041 Nm/kg difference in mean hip extension moment during terminal swing), and differences between the models with and without hip joint center adjustment resulted in significant differences in hip flexion and abduction moments during stance (0.217 ± 0.055 Nm/kg increased mean hip abductive moment). By comparing the outputs of these differently constructed models with each other, the study finds that dynamic predictions of stance are sensitive to positioning of joint centers, and dynamic predictions of swing are more sensitive to segment mass/inertial properties.

Cup-cage constructs in revision total hip arthroplasty for pelvic discontinuity.

Pelvic discontinuity is a challenging acetabular defect without a consensus on surgical management. Cup-cage reconstruction is an increasingly used treatment strategy. The present study evaluated implant survival, clinical and radiological outcomes, and complications associated with the cup-cage construct. We included 53 cup-cage construct (51 patients) implants used for hip revision procedures for pelvic discontinuity between January 2003 and January 2022 in this retrospective review. Mean age at surgery was 71.8 years (50.0 to 92.0; SD 10.3), 43/53 (81.1%) were female, and mean follow-up was 6.4 years (0.02 to 20.0; SD 4.6). Patients were implanted with a Trabecular Metal Revision Shell with either a ZCA cage (n = 12) or a TMARS cage (n = 40, all Zimmer Biomet). Pelvic discontinuity was diagnosed on preoperative radiographs and/or intraoperatively. Kaplan-Meier survival analysis was performed, with failure defined as revision of the cup-cage reconstruction. The five-year all-cause survival for cup-cage reconstruction was 73.4% (95% confidence interval (CI) 61.4 to 85.4), while the ten- and 15-year survival was 63.7% (95% CI 46.8 to 80.6). Survival due to aseptic loosening was 93.4% (95% CI 86.2 to 100.0) at five, ten, and 15 years. The rate of revision for aseptic loosening, infection, and dislocation was 3/53 (5.7%), 7/53 (13.2%), and 6/53 (11.3%), respectively. The mean leg length discrepancy improved (p < 0.001) preoperatively from a mean of 18.2 mm (0 to 80; SD 15.8) to 7.0 mm (0 to 35; SD 9.8) at latest follow-up. The horizontal and vertical hip centres improved (p < 0.001) preoperatively from a mean of 9.2 cm (5.6 to 17.5; SD 2.3) to 10.1 cm (6.2 to 13.4; SD 2.1) and 9.3 cm (4.7 to 15.8; SD 2.5) to 8.0 cm (3.7 to 12.3; SD 1.7), respectively. Cup-cage reconstruction provides acceptable outcomes in the management of pelvic discontinuity. One in four constructs undergo revision within five years, most commonly for periprosthetic joint infection, dislocation, or aseptic loosening.

Hip joint center lateralization minimally affects the biomechanics of patient-specific flanged acetabular components: A computational model.

Patient-specific flanged acetabular components are utilized to treat failed total hip arthroplasties with large acetabular defects. Previous clinical studies from our institution showed that these implants tend to lateralize the acetabular center of rotation. However, the clinical impact of lateralization on implant survivorship is debated. Our goal was to develop a finite element model to quantify how lateralization of the native hip center affects periprosthetic strain and implant-bone micromotion distributions in a static level gait loading condition. To build the model, we computationally created a superomedial acetabular defect in a computed tomography 3D reconstruction of a native pelvis and designed a flanged acetabular implant to address this simulated bone defect. We modeled two implants, one with ~1 cm and a second with ~2 cm of hip center lateralization. We applied the maximum hip contact force and corresponding abductor force observed during level gait. The resulting strains were compared to bone fatigue strength (0.3% strain) and the micromotions were compared to the threshold for bone ingrowth (20 µm). Overall, the model demonstrated that the additional lateralization only slightly increased the area of bone at risk of failure and decreased the areas compatible with bone ingrowth. This computational study of patient-specific acetabular implants establishes the utility of our modeling approach. Further refinement will yield a model that can explore a multitude of variables and could be used to develop a biomechanically-based acetabular bone loss classification system to guide the development of patient-specific implants in the treatment of large acetabular bone defects.

Which method should we use to determine the hip joint center location in individuals with a high amount of soft tissue?

BackgroundThis study investigated the most accurate method for estimating the hip joint center position in clinical 3D gait analysis for young individuals with high amounts of soft tissue. We compared position estimates of five regression-based and two functional methods to the hip joint center position obtained through 3D free-hand ultrasound. MethodsFor this purpose, the data of 14 overweight or obese individuals with a mean age of 13.6 (SD 2.1 yrs) and a BMI of 36.5 (SD 7.1 kg/m2, range 26–52 kg/m2) who underwent standard clinical 3D gait analysis were used. The data of each participant were processed with five regression-based and two functional methods and compared to the hip joint center identified via 3D free-hand ultrasound. FindingsThe absolute location errors to 3D free-hand ultrasound for each anatomical plane and the Euclidean distances served as outcomes next to their effects on gait variables. The data suggest that regression-based methods are preferable to functional methods in this population, as the latter demonstrated the highest variability in accuracy with large errors for some individuals. InterpretationBased on our findings we recommend using the regression method presented by Hara et al. due to its superior overall accuracy of <9 mm on average in all planes and the lowest impact on kinematic and kinetic output variables. We do not recommend using the Harrington equations (single and multiple) in populations with high amounts of soft tissue as they require pelvic depth as input, which can be massively biased when a lot of soft tissue is present around the pelvis.

Do all short stem types restore biomechanical parameters of the hip? Comparison according to femoral neck osteotomy levels.

There is no consensus on ideal short femoral stem design. A classification system proposed by Feyen and Shimmin divides short stems in two types according to femoral neck osteotomy levels: subcapital (IIIA) and standard (IIIB). The study aims to determine which design type is more successful in restoring native biomechanical parameters and whether stem type has an impact on clinical results. In this retrospective comparative study, patients that have undergone short stem hip arthroplasty were evaluated according to stem types: type IIIA (n = 52, 66.7%) (Mathys Optimys) and IIIB (n = 26, 33.3%) (Implantcast Aida and Smith & Nephew SMF). Pelvis X-rays were assessed in terms of femoral neck length, horizontal and vertical hip centres of rotation, horizontal and vertical femoral offsets, abductor lever arm lengths, leg lengths, and stem-shaft angles. Improvement in Harris hip scores, differences between post-operative and pre-operative measurements, and stem-shaft angles were evaluated and compared between two groups. Mean femoral neck resection (8.27 ± 6.68mm in IIIA and 15 ± 6.33mm in IIIB) was significantly different between both groups (p < 0.001). Harris hip scores were increased at post-operative six months in both groups with no difference (84.4 ± 6.4 and 84.6 ± 5.5, p = 0.4). The absolute values of differences between pre-operative and post-operative horizontal centres of rotation (p = 0.63), vertical centers of rotation (p = 0.75), horizontal femoral offsets (p = 0.78), vertical femoral offsets (p = 0.83), abductor lever arm distances (p = 0.63), and leg length (p = 0.21) measurements were not different between both groups. Stem positions were both varus with no statistically significant difference between groups (p = 0.14). We found no difference regarding restoration of biomechanical parameters between short stem designs with different levels of neck osteotomy. Additionally, short stem can mostly result in varus component positioning regardless of the level of neck osteotomy.

Does Periacetabular Osteotomy Change Sagittal Spinopelvic Alignment?

There are few data on the impact of periacetabular osteotomy (PAO) on sagittal spinopelvic alignment. Prior studies have attempted to delineate the relationship by performing measurements on AP radiographs and using mathematical models to determine changes in postoperative pelvic tilt. This information is clinically significant to a surgeon when evaluating acetabular/pelvic position intraoperatively and understanding spinopelvic alignment changes postoperatively; therefore, radiographic changes from PAO should be described in more detail. In this study, we asked: (1) Does the performance of PAO result in consistent changes in spinopelvic alignment, as measured on EOS radiographs? (2) Does this differ for unilateral versus bilateral PAOs? (3) Does this differ in the setting of a mobile spine versus an immobile spine? (4) Does this differ based on preoperative pelvic tilt? Mean preoperative and at least 1-year postoperative (15 ± 8 months from surgery, minimum 11 months, maximum 65 months) EOS hip-to-ankle standing and sitting radiographs for 55 patients in a prospectively collected registry who underwent PAO with a single surgeon from January 1, 2019, to January 11, 2022, were measured for pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, lateral center-edge angle, L1 pelvic angle, and pubic symphysis to the sacroiliac index. Normality was assessed and paired sample t-tests (normally distributed data) or Wilcoxon signed rank tests (not normally distributed data) were utilized to assess if any measurements changed from preoperative to postoperative. Patients were then divided based on whether they had unilateral or bilateral dysplasia and unilateral or bilateral surgery, and these subgroups were analyzed the same way as the entire cohort. Two more subgroups were then formed based on lumbar mobility, defined as a change in sitting-to-standing lumbar lordosis less or greater than 1 SD from the population mean preoperatively, and the subgroups were analyzed the same way as the entire cohort. Finally, two additional subgroups were formed, preoperative standing pelvic tilt less than 10° and more than 20°, and analyzed the same as the entire cohort. For the entire cohort, the median (IQR) standing lateral-center edge angle increased 17°, from a median of 21° (10°) to a median of 38° (8° [95% confidence interval (CI) 16° to 20°; p < 0.001). The median sitting lateral center-edge angle increased 17°, from a median of 18° (8°) to a median of 35° (8° [95% CI 14° to 19°]; p < 0.001). Standing pelvic incidence increased from 50° ± 11° to 52° ± 12° (mean difference 2° [95% CI 1° to 3°]; p = 0.004), but there were no changes for other measured parameters. There were no changes in any of the spinopelvic parameters for patients with unilateral dysplasia receiving a unilateral PAO, but patients with bilateral dysplasia who underwent bilateral PAOs demonstrated an increase in pelvic incidence from 57° (14°) to 60° (16°) (95% CI 1° to 5°; p = 0.02) and a decrease in pubic symphysis to sacroiliac index from 84 mm (24 mm) to 77 mm (23 mm) (95% CI -7° to -2°; p = 0.007). Patients with mobile lumbar spines preoperatively did not exhibit any changes in sagittal spinopelvic alignment, but patients with immobile lumbar spines preoperatively experienced several changes after surgery. Patients with less than 10° of standing pelvic tilt demonstrated a median (IQR) 2° increase in pelvic incidence from median 43° (9°) to 45° (12° [95% CI 0.3° to 4°]; p = 0.03), but they did not experience any other changes in sagittal spinopelvic alignment parameters postoperatively. Patients with preoperative pelvic tilt more than 20° did not experience any change in sagittal spinopelvic parameters. PAO increases pelvic incidence, potentially because of anterior translation of the hip center. There were no changes in other spinopelvic parameters postoperatively except after bilateral PAO. Additionally, patients lacking spine mobility preoperatively, indicated by a minimal change in lumbar lordosis between standing and sitting positions, may experience several changes in spinopelvic alignment, including increased mobility of their spine after PAO. This may be because of decreased compensatory spine splinting after increasing acetabular coverage, but further research including patient-reported outcomes is warranted. Level III, therapeutic study.

Accuracy of conventional motion capture in measuring hip joint center location and hip rotations during gait, squat, and step-up activities

Accurate measurements of hip joint kinematics are essential for improving our understanding of the effects of injury, disease, and surgical intervention on long-term hip joint health. This study assessed the accuracy of conventional motion capture (MoCap) for measuring hip joint center (HJC) location and hip joint angles during gait, squat, and step-up activities while using dynamic biplane radiography (DBR) as the reference standard. Twenty-four young adults performed six trials of treadmill walking, six body-weight squats, and six step-ups within a biplane radiography system. Synchronized biplane radiographs were collected at 50 images per second and MoCap was collected simultaneously at 100 images per second. Bone motion during each activity was determined by matching digitally reconstructed radiographs, created from subject-specific CT-based bone models, to the biplane radiographs using a validated registration process. Errors in estimating HJC location and hip angles using MoCap were quantified by the root mean squared error (RMSE) across all frames of available data. The MoCap error in estimating HJC location was larger during step-up (up to 89.3 mm) than during gait (up to 16.6 mm) or squat (up to 31.4 mm) in all three anatomic directions (all p < 0.001). RMSE in hip joint flexion (7.2°) and abduction (4.3°) during gait was less than during squat (23.8° and 8.9°) and step-up (20.1° and 10.6°) (all p < 0.01). Clinical analysis and computational models that rely on skin-mounted markers to estimate hip kinematics should be interpreted with caution, especially during activities that involve deeper hip flexion.

High accuracy of positioning custom triflange acetabular components in tumour and total hip arthroplasty revision surgery.

Custom triflange acetabular components (CTACs) play an important role in reconstructive orthopaedic surgery, particularly in revision total hip arthroplasty (rTHA) and pelvic tumour resection procedures. Accurate CTAC positioning is essential to successful surgical outcomes. While prior studies have explored CTAC positioning in rTHA, research focusing on tumour cases and implant flange positioning precision remains limited. Additionally, the impact of intraoperative navigation on positioning accuracy warrants further investigation. This study assesses CTAC positioning accuracy in tumour resection and rTHA cases, focusing on the differences between preoperative planning and postoperative implant positions. A multicentre observational cohort study in Australia between February 2017 and March 2021 included consecutive patients undergoing acetabular reconstruction with CTACs in rTHA (Paprosky 3A/3B defects) or tumour resection (including Enneking P2 peri-acetabular area). Of 103 eligible patients (104 hips), 34 patients (35 hips) were analyzed. CTAC positioning was generally accurate, with minor deviations in cup inclination (mean 2.7°; SD 2.84°), anteversion (mean 3.6°; SD 5.04°), and rotation (mean 2.1°; SD 2.47°). Deviation of the hip centre of rotation (COR) showed a mean vector length of 5.9 mm (SD 7.24). Flange positions showed small deviations, with the ischial flange exhibiting the largest deviation (mean vector length of 7.0 mm; SD 8.65). Overall, 83% of the implants were accurately positioned, with 17% exceeding malpositioning thresholds. CTACs used in tumour resections exhibited higher positioning accuracy than rTHA cases, with significant differences in inclination (1.5° for tumour vs 3.4° for rTHA) and rotation (1.3° for tumour vs 2.4° for rTHA). The use of intraoperative navigation appeared to enhance positioning accuracy, but this did not reach statistical significance. This study demonstrates favourable CTAC positioning accuracy, with potential for improved accuracy through intraoperative navigation. Further research is needed to understand the implications of positioning accuracy on implant performance and long-term survival.