ABSTRACT. Introduction The technique for total hip replacement (THR) surgery has evolved over time. Modern developments include computer navigation and robotic assistance. There is a paucity of data comparing computer navigation to robotic assistance. The aim of this study was to compare radiographic and clinical outcomes between conventional, computer navigated and robot assisted THR. Methods A total of 255 patients underwent THR by the same surgeon using conventional(CTHR),computer navigation(NTHR) and robotic techniques(RTHR). The demographic distribution in Table1. The navigation system used was Orthopilot and the robotic system was MAKO robot. We aimed for a target acetabular inclination of 40° in all patients. Anteversion was aimed to avoid anterior rim impingement. Postoperative follow up was by independent arthroplasty practitioners. Table 1: Demographics CTHR (n=57) NTHR (n=123) RTHR (n=75) Gender (Female) 45 57 50 Mean Age (years) 72.1 (SD8.2) 67.5 (SD9.3) 66.7 (SD13.2) Body Mass Index (kg/m2) 29.4 (SD4.1) 29.17 (SD5.3) 30.9 (4.5) Operated Side (Right) 32 70 39 Results There was a statistically significant difference in the accuracy achieved for acetabular inclination and anteversion with NTHR (p= <0.005) and RTHR (p=<0.005) compared to CTHR. RTHR performed better than NTHR for inclination and anteversion (p=<0.005, p=0.03). There was no significant difference in the mean oxford hip score (OHS) or patient satisfaction between the three groups (p=0.11) at 3 months postop.

Present study demonstrates that modern techniques like NTHR and RTHR have superior radiographic outcomes compared to conventional techniques. RTHR can further improve on NTHR. Early postoperative outcomes with all three techniques are similar.

ABSTRACT. Introduction We developed a new noninvasive augmented reality (AR)-based portable navigation system for accurate cup positioning during total hip arthroplasty (THA) in the supine position. This study aimed to clarify whether the navigation system supports cup positioning more accurately than a conventional goniometer during surgery. Materials and Methods Sixty patients who underwent THA in the supine position were enrolled. The navigation system was used for 30 patients (navigation group) and a conventional goniometer was used for 30 patients (control group) to measure radiographic cup inclination and anteversion during surgery. The primary outcome was the absolute value of the difference in cup alignment measured during surgery and by postoperative radiography. Results The new noninvasive AR-based navigation system showed superior cup positioning accuracy compared to a conventional goniometer. An assessment of the primary outcome showed no significant difference in the radiographic cup inclination in the navigation and control groups (2.3° vs. 2.9°; mean difference, 0.6°; 95% confidence interval, −0.4 to 1.6; p = 0.22); however, the positioning in the navigation group was significantly more accurate than that in the control group in terms of radiographic anteversion (2.4° vs. 5.5°; mean difference, 3.1°; 95% confidence interval, 1.7–4.5; p<0.001). Conclusion The use of a new noninvasive AR-based portable navigation system resulted in more accurate cup positioning than the conventional goniometer. Because it is noninvasive, this system should be used for THA in the supine position.

ABSTRACT. 1. Introduction Total knee arthroplasty remains the standard of care for treating end-stage osteoarthritis of the knee joint. Approximately 15 - 20 % of the patients are dissatisfied following surgery. To improve outcomes, some authors suggest a personalized alignment with narrow and specific margins as ideal target in TKA. In an attempt to achieve this goal different techniques are being introduced in the field of TKA surgery. An augmented reality solution was explored and tested. 2. Materials and Methods In this study the Pixee Knee + system was used (Pixee Medical, Besancon, France). The device offers orthopaedic surgeons intraoperative assistance for implant positioning with the help of augmented reality glasses. The primary research goal is to evaluate the accuracy of an augmented reality based navigation system in the frontal plane by direct comparison of the planned angular values, the intraoperative obtained values and the angles as measured on postop full leg radiographs. The secondary research goal is to assess the feasibility of the system in terms of safety and surgical time. 3. Results This retrospective study evaluated 124 patients. All patients were followed up for at least one year. For the coronal plane, the mean difference between the planned angles and the measured angles was approximately 0.5 degrees. The average skin-to-skin surgical time was 76 minutes. 4. Discussion The most important finding of the present study is that this novel technology demonstrated high accuracy in reproducing the planned angular values in a clinical setting.

ABSTRACT. Background * The development of 3D printing technology has had a significant impact on the medical field. This technology has made it possible to create custom-made implants that can be flexibly adapted to the bone defects of individual patients. In this study, total hip arthroplasty (THA) using the custom-made implant developed in Japan, was reviewed in patients with severe acetabular bone defects. The accuracy of each implant placement was examined. Study Design & Methods * We retrospectively studied 10 patients who underwent THA with T-REX® (Teijin Nakashima Medical) at our institution between 2020 and 2022. A 3D pelvic model of each patient was created based on preoperative computed tomography (CT) data. The 3D CAD system was used to preoperatively plan the construction of an augmentation and a flange, where necessary. A pelvic model and an implant copy made to the same shape as the custom-made implant were used as a patient-specific guide. Postoperative CT data confirmed implant placement and determined alignment errors. Results * The absolute errors of implant alignment were 3.92 degrees for inclination, 1.81 degrees for anteversion, and 5.48 degrees for rotation. Absolute errors of 1.87 mm in the internal/external direction, 1.55 mm in the anteroposterior direction, and 1.10 mm in the vertical direction were also observed. Conclusions * T-REX® implants can be accurately placed during THA in cases with severe acetabular bone defects. These implants can be expected to provide firm initial fixation by taking advantage of the flexibility in their design, making them a useful treatment option for patients.

ABSTRACT. Preoperative planning of total hip arthroplasty (THA) continues to be an essential step for a successful outcome. Preoperative templating has advanced from two dimensional templating (2D) using acetate and digital software to three-dimensional templating (3D) using CT scan. The aim of this study was to compare the accuracy of 2D and 3D templating method to actual component sizes. It also assesses the interobserver reliability of 2D templating. Seventy consecutive THAs were performed using the robotic assisted MAKO system (Stryker) 57 hybrid and 13 uncemented replacements. The preoperative 3-D template was performed by arthroplasty surgeon and senior arthroplasty fellow. Calibrated digital AP pelvis radiograph were available for all patients prior to surgery, which were reviewed by two independent blinded observers and 2D templating was conducted using Materialise Orthoview templating software. The preoperative variables studied were cup size, femoral offset, and femoral stem size. The 3D template also included the angle of the planned cup anteversion and cup inclination. A correlation coefficient of 0.99 was found between the 3D templated cup size and the actual implant used, and 0.92 between the 3D templated femoral offset and the actual implant. Robotic arm assisted total hip replacement 3D templating system outperforms 2D templating.

ABSTRACT. Iliopsoas tendonitis (IT) occurs in between 4-30% of patients after total hip arthroplasty (THA). We have developed an iliopsoas impingement detection simulation and previously validated this in a case-controlled investigation. The aim of this study was to apply our simulation to the preoperative context to understand risk factors that may exacerbate iliopsoas tendonitis under the hypothesis that iliopsoas impingement would be related to kinematic factors, such as pelvic tilt and femoral rotation.

This was a retrospective simulation study of 455 patients undergoing THA surgery. All patients underwent 3D templating with standardized implant parameters. The segmented bones were transformed to the standing reference frame using the pelvic tilt and functional femoral rotation measured on the lateral x-rays and each patient was simulated in a novel computational model that detects iliopsoas impingement. Patients who were at-risk of IT were identified using the optimal cut-off point from the previous validation study and matched to patients who were not at-risk of IT using a 1:1 nearest-neighbor logistic regression matching algorithm with age and gender as covariates. Implant and postural parameters were compared between the patient cohorts.

25% of patients were identified as being at-risk of IT. Mean standing pelvic tilt for the at-risk patients was -6.6° and -0.4° for the not at-risk patients. The difference was statistically significant (p << 0.01). Mean difference between planned cup size and native femoral head diameter (ΔC-NFH) for the at-risk patients was 6.7mm and 5.2mm for the not at-risk patients. The difference was statistically significant (p = 0.01). No significant differences were found for native femoral head diameter (p = 0.11), planned cup diameter (p = 0.57), and functional femoral rotation (p = 0.58).

Iliopsoas tendonitis is more complex than simply being related to the presence of cup uncoverage and may be exacerbated by postural factors. Our results shed light on the relevance of spinopelvic factors to iliopsoas irritation, which could factor into a surgeon’s preoperative expectation management of patients who have significant posterior pelvic tilt in standing. Additionally, we observed a similar ΔC-NFH threshold to Odri et al., which could be factored into preoperative planning to avoid IT.

ABSTRACT. The purpose of this study was to investigate changes in spinopelvic sagittal alignment and motion before and after total hip arthroplasty (THA). A total of 91 patients were assessed. To evaluate spinopelvic motion, sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), lumber lordosis (LL) were measured on lateral spinopelvic radiographs in standing and sitting position. To evaluate spinopelvic sagittal alignment, PI-LL was categorized as follow: PI-LL > 10°, PI-LL ≤ 10° was regarded as flat back and normal alignment, respectively. The classification of spinopelvic mobility was defined as a change in SS from standing to sitting position (ΔSS). 10° ≤ ΔSS ≤ 30°, ΔSS < 10°, and ΔSS > 30° were regarded as normal, stiff, and hypermobile, respectively. At one year after THA, the classification of PI-LL changed in 19 cases (20%) and ΔSS changed in 47 cases (52%). Our findings suggest that surgeons should take care that preoperative spinopelvic alignment and mobility could change 1 year after THA.

ABSTRACT. It has been well reported that the use of navigation in total hip arthroplasty (THA) optimises the restoration of hip biomechanics through accurate positioning of the acetabular component. However, there is a lack of data published on the role navigation has on the functional biomechanics of the hip, and how this correlates to patient reported outcome measures (PROMS). Traditional PROMs have not been able to detect differences in the outcomes of technology assisted surgeries such as navigation and robotics.

The aim of this study is to describe the relationship between PROMS and functional biomechanics during a sit to stand (STS) and active flexion task in a cohort of 65 male patients who underwent navigated unilateral THA.

Despite significant improvements in the Oxford Hip Score, EQ5D and Harris Hip Score, patients demonstrated a mild but significant asymmetry in limb loading during STS measured three months post-THA using 3D motion analysis. There was no correlation between limb loading and PROMs. There was a statistically significant difference in peak hip flexion in the operated and non-operated limbs, however, this did not correlate with any PROMs.

This study demonstrates the importance of objective functional assessment of THA patients as asymmetries of limb loading during STS are evident despite excellent PROM scores. In order to scrutinise the benefits of emerging surgical technologies such as robotics, we need to utilise more sensitive measures of assessment, such as functional biomechanical assessment.

ABSTRACT. Introduction Femoral Implant designs are historically based on femoral anatomy using CT scan and bony dimensions. Most femoral implant designs ignore the role acetabular cup positioning plays in biomechanics of total hip offset. The primary aim of this paper was to see if the existing femoral implant design catered to all the patients’ biomechanical requirements. Secondary aim was to see if a design recommendation can be made based on intraoperative navigation biomechanics. Methods Present study was done on 68 patients who underwent total hip replacement with computer navigation. The implant has two offset variables using same intramedullary fit: Excia T with neck shaft angle 135 and Excia TL, the lateralised offset with neck shaft angle of 128. Age was 66.5 (Std 7.3) and BMI 29.3 (Std 4.4). Authors aimed to make either no change in total offset or lateralise (Increase) it to within 6mm. Any medialisation was not intended. Results Only 8 patients needed standard offset femoral component. Of the rest, 48.33% (29/60) ended up with medialisation (Range -13 to 6mm Av -1.35mm Median 0mm Std 4.66mm) even though they had a lateralised Excia TL. In total 42.65% (29/68) hips ended up medialised, due to lack of a femoral component with extra lateral offset. An additional 6 mm lateralised component would mean 87% of patients would have the biomechanics restored to surgeon`s target as compared to only 57% of the present design and all but one (98.5%) would be within 6mm medialisation range. Conclusion Present study proved that the existing femoral implant design portfolio did not cater to all the patients. Navigation acted as an excellent tool to show deficiency in the present implant design portfolio and to make a recommendation based on numbers

ABSTRACT. Iliopsoas tendonitis (IT) occurs in up to 30% of patients after hip resurfacing arthroplasty (HRA). We have previously developed an iliopsoas impingement detection simulation and validated it in case-controlled investigation of total hip arthroplasty (THA) patients. However, the incidence of IT after HRA is meaningfully higher than THA, so the aim of this study was to examine why this differential might exist through a similar case-controlled investigation. Our hypotheses were that: (1) the symptomatic HRA cohort would have a significantly greater level of impingement than the asymptomatic HRA cohort; and (2) the symptomatic HRA cohort would have a significantly greater level of impingement than the symptomatic THA cohort.

This was a simulation study of HRA patients who were diagnosed with IT (symptomatic cohort) and patients who were not diagnosed with IT (asymptomatic cohort). 3D reconstructions of each patient’s bony anatomy were generated from CT and used to simulate the iliopsoas impingement in supine and standing using our validated simulation. Receiver operating characteristic (ROC) curves were generated to determine the model’s sensitivity, specificity, and area under the curve (AUC).

The mean cup prominence for the symptomatic cohort was 10.7mm and 5.1mm for the asymptomatic cohort (p << 0.01). The average standing mean impingement for the symptomatic cohort was 0.1mm and 0.0mm for the asymptomatic cohort (p << 0.01). The average standing maximum impingement for the symptomatic cohort was 0.2mm and 0.0mm for the asymptomatic cohort (p << 0.01). Impingement significantly predicted the probability of pain in logistic regression models and the simulation had a sensitivity of 92%, specificity of 91%, and an AUC ROC curve of 0.95.

Our simulation has now been validated to detect iliopsoas impingement in THA and HRA cohorts. Interestingly, less impingement was observed in the symptomatic HRA patients than the symptomatic THA patients, despite greater cup prominence. This tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to aid in the diagnosis of iliopsoas tendonitis. Also of interest were the two patients in the symptomatic cohort for whom no impingement was detected – what might be called ‘false negatives’. This is indicative of the multi-causal nature of iliopsoas tendonitis as these patients likely experienced irritation due to another sources of iliopsoas tendonitis.

ABSTRACT. Curved periacetabular osteotomy (CPO) is technically demanding procedure because we have to enter the osteotomy site from inside of pelvis without direct view of hip joint. To achieve this tricky procedure without troubles such as posterior column fracture or intraarticular osteotomy, we used CT-based navigation. To investigate accuracy of osteotomy in patients who underwent CT-based navigation assisted CPO, pre- and post-operative CT images were measured with three dimensional (3D) image analyzing software. The 3D image analysis demonstrated that our osteotomies were not so accurate because each standard deviation of measurement values were not small. Our clinical data showed that 73% patients developed cartilage degeneration after CPO in postoperative X-ray films. Painful hips were observed in 26.9% and one hip was converted to total hip arthroplasty within 3 years after CPO. The first reason of these inaccuracy and unsatisfaction of our CPO was lack of consensus for true target zone of rotated acetabulum in CPO. We determined each final acetabular position by checking with intraoperative fluoroscopic 2D images. The second reason was that the current CT-based navigation could only assist osteotomy of ilium and quadrilateral surface. In addition, our navigation could not assist to rotate the acetabulum in real time. Further improvements are required to achieve more accurate and successful CPO with computer assisted surgery.

ABSTRACT. Dislocation is one of the most common complications in total hip arthroplasty (THA). The aims of this study were two-fold. First, to develop a simulation that incorporates the functional position of the femur and pelvis and instantaneously determines range of motion (ROM) limits. Second, to assess the number of patients for whom their functional bony alignment escalates or de-escalates impingement risk.

This was a retrospective simulation study of 436 patients. All patients underwent 3D templating with standardized implant criteria and their ROM was simulated in seated flexion (rise from chair movement) and standing external rotation (ER) (pivot movement) with the following thresholds: 120° for hip flexion and 45° for ER. ROM was simulated in three bony alignments: (1) Neutral (neutral pelvis and neutral femur). (2) Semi-Functional (functional pelvis, neutral femur). (3) Functional (functional pelvis and functional femur).

For standing ER, the following percentages of patients failed the simulations: 24% of patients with Neutral alignment, 23% of patients with Semi-Functional alignment, and 24% of patients with Functional alignment. 38% of patients who failed the simulation in Semi-Functional passed in their Functional alignment (‘false positives’). These patients have femoral rotation that protect them from being at risk of posterior impingement and anterior instability. 13% of patients who passed the simulation in Semi-Functional failed in their Functional alignment (‘false negatives’). These patients have femoral rotation that escalates them to being at risk of posterior impingement and anterior instability.

We have developed a ROM simulation that can solve bony and prosthetic impingement limits instantaneously using functional femoral and pelvic positioning. Not considering the functional position of the pelvis and/or femur may manifest as ‘false positive’ or ‘false negative’ simulation results, which could lead to correcting for an issue that would not have occurred. Some consequences of ‘false positives’ could be: 1. increasing cup anteversion to prevent supposed anterior impingement, leading to anterosuperior edge loading with subsequent squeaking or excessive wear. 2. decreasing cup anteversion to prevent supposed posterior impingement, leading to impingement between the iliopsoas and an exposed acetabular cup.