Purpose of the study: Computer assisted surgery for total knee arthroplasty is widely used in Europe. The reliability of these systems appears to be very good with bone cuts within 3° of the planned mechanical axis. Nevertheless, the relationship between intraoperative measurements provided by the navigation system and the postoperative gonometry can be used to assess the quality of realignment. The purpose of this work was to determine this relationship. Material and methods: Thirty-three knees operated on with the Navitrack® system were assessed. Two senior operaters performed all procedures. An Omnia® cemented prosthesis with an ultracongruent fixed plateau was used in all cases. Intraoperative measurements wer made with the definitive prosthesis after cement solidification without stress on the knee. Postoperative gonometry was undertaken when the intraoperative flexion had disappeared six weeks to six months after the operation. Gonometric measurements were made by an independent operator using a computerized system operating on digitalized x-rays. The gonometric protocol had been standardized previously and only the gonometric measurements in compliance with this protocol were retained for analysis. The difference between measurements was analyzed with the t test for paired variables. Search for correlations was also performed. Results: On average the intraoperative deviation was 0.8±0.8° (3° valgus to 2.4° varus). The postoperative gonometry showed 1.7±1.1° (3.4° valgus to 4.3° varus). The mean difference between the intraoperative axis and the measured postoperative axis was significant (p< 0.0001). There was no significant correlation between intraoperative and postoperative measurements. Discussion: Computer-assisted navigation systems have their limitations which should be measured. The present findings would demonstrate a significant difference of minimal amplitude between the intraoperative measurement and the postoperative gonometry. Although the clinical pertinence of this difference remains to be demonstrated, it must be kept in mind for safe use of these navigation systems

Introduction. Computer-assisted orthopaedic surgery (CAOS) provides great value in ensuring accurate, reliable and reproducible total knee arthroplasty (TKA) outcomes [1,2]. Depending on surgeon preferences or patient factors (e.g. BMI, ligament condition, and individual joint anatomy), resection planning (guided adjustment of cutting blocks) is performed with different knee flexion, abduction/adduction (ABD/ADD) and internal/external (I/E) rotation angles, potentially leading to measurement errors in the planned resections due to a modified tracker/localizer spatial relationship. This study assessed the variation in the intraoperative measurement of the planned resection due to leg manipulation during TKA, and identified the leg position variables (flexion, ABD/ADD, and I/E rotation) contributing to the variability. Materials and Methods. Computer-assisted TKA (ExactechGPS®, Blue-Ortho, Grenoble, FR) was performed on a neutral whole leg assembly (MITA knee insert and trainer leg, Medial Models, Bristol, UK) by a board-certified orthopaedic surgeon (BH) at his preferred leg flexion, ABD/ADD, and I/E rotation angles. A cutting block was adjusted and fixed to the tibia, targeting the resection parameters listed in Table 1A. An instrumented resection checker was then attached to the cutting block to measure the planned resection at the same leg position (baseline). Next, the surgeon moved the leg to 9 sampled positions, representing typical leg position/orientation associated with different steps during TKA [Table 1B]. The planned resection was tracked by the CAOS system at each leg position. Tibial resection parameters at each sampled position were compared to the baseline. Regression was performed to identify the variables (flexion, ABD/ADD, I/E rotation) that significantly contribute to the measured variation (p<0.05). Results. The resection parameters at the baseline leg position are presented (see Table 1A). Clinically negligible variations were found across the 9 positions [Table 1B], with mean errors ≤0.1mm in resection depths and ≤0.2° in alignment parameters. For this particular system analyzed, leg flexion strongly correlated with the measurement errors in medial resection depths (p≤0.01, R2=0.76), lateral resection depth (p=0.01, R2=0.61) and posterior slope (p<0.01, R2=0.92) [Fig. 1]. The system tended to measure less in resection depths and posterior slope with an increased leg flexion [Fig. 1]. No other statistical significance was found (N.S.). Discussion. The results here showed that ExactechGPS can provide robust measurements of the planned resection parameters during TKA, independent of the ABD/ADD and I/E rotation of the knee. Although for the system studied, measurement errors strongly correlated with leg flexion, the magnitude of the errors was clinically negligible (within ±0.5 mm/° at a confidence level of 95%) [Table 1B]. Although CAOS systems have been evaluated for accuracy in the spatial distance measurement and clinical alignment outcomes [2,3], the measurement accuracy of planned resection parameters due to change of leg position remains unknown, even though it directly impacts the final resection. This study provided an improved understanding of clinical variability on the measurement of planned TKA resection when using a CAOS system

Our objectives were to establish the envelope of passive movement and to demonstrate the kinematic behaviour of the knee during standard clinical tests before and after reconstruction of the anterior cruciate ligament (ACL). An electromagnetic device was used to measure movement of the joint during surgery.

Reconstruction of the ACL significantly reduced the overall envelope of tibial rotation (10° to 90° flexion), moved this envelope into external rotation from 0° to 20° flexion, and reduced the anterior position of the tibial plateau (5° to 30° flexion) (p < 0.05 for all). During the pivot-shift test in early flexion there was progressive anterior tibial subluxation with internal rotation. These subluxations reversed suddenly around a mean position of 36 ± 9° of flexion of the knee and consisted of an external tibial rotation of 13 ± 8° combined with a posterior tibial translation of 12 ± 8 mm. This abnormal movement was abolished after reconstruction of the ACL.

Introduction

Correct postoperative leg length restoration is among the most important goals of hip arthroplasty. Therefore, we developed, validated and clinically applied a novel software algorithm based on surgical navigation, which allows the surgeon to restore a defined femur position without establishing a femoral coordinate system or the hip joint center and measure the leg length accurately and simply.

Background

Spastic muscles of patients with cerebral palsy (CP) are considered structurally as shortened muscles, that produce high force in short muscle lengths. Yet, previous intraoperative studies in which muscles’ forces are measured directly as a function of joint angle showed consistently that spastic knee flexor muscles produce a low percentage of their maximum force in flexed knee positions. They also showed effects of epimuscular myofascial force transmission (EMFT): simultaneous activation of different muscles elevated target muscle's force. However, quantification of spastic muscle's force - muscle-tendon unit length (l_MTU) data during gait is lacking.

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal

The purposes of this study were to report the accuracy of stem anteversion for Exeter cemented stems with the Mako hip enhanced mode and to compare it to Accolade cementless stems. We reviewed the data of 25 hips in 20 patients who underwent THA through the posterior approach with Exeter stems and 25 hips in 19 patients with Accolade stems were matched for age, gender, height, weight, disease, and approaches. There was no difference in the target stem anteversion (20°–30°) between the groups. Two weeks after surgery, CT images were taken to measure stem anteversion. The difference in stem anteversion between the plan and the postoperative CT measurements was 1.2° ± 3.8° (SD) on average with cemented stems and 4.2° ± 4.2° with cementless stems, respectively (P <0.05). The difference in stem anteversion between the intraoperative measurements and the postoperative CT measurements was 0.75° ± 1.8° with Exeter stems and 2.2° ± 2.3° with Accolade stems, respectively (P <0.05). This study demonstrated a high precision of anteversion for Exeter cemented stems with the Mako enhanced mode and its clinical accuracy was better with the cemented stems than that with the cementless stems. Although intraoperative stem anteversion measurements with the Mako system were more accurate with the cemented stems than that with the cementless stem, the difference was about 1° and the accuracy of intra-operative anteversion measurements was quite high even with the cementless stems. The smaller difference in stem anteversion between the plan and postoperative measurements with the cemented stems suggested that stem anteversion control was easier with cemented stems under the Mako enhanced mode than that with cementless stems. Intraoperative stem anteversion measurement with Mako total hip enhanced mode was accurate and it was useful in controlling cemented stem anteversion to the target angle

Aims. Accurate diagnosis of chronic periprosthetic joint infection (PJI) presents a significant challenge for hip surgeons. Preoperative diagnosis is not always easy to establish, making the intraoperative decision-making process crucial in deciding between one- and two-stage revision total hip arthroplasty (THA). Calprotectin is a promising point-of-care novel biomarker that has displayed high accuracy in detecting PJI. We aimed to evaluate the utility of intraoperative calprotectin lateral flow immunoassay (LFI) in THA patients with suspected chronic PJI. Methods. The study included 48 THAs in 48 patients with a clinical suspicion of PJI, but who did not meet European Bone and Joint Infection Society (EBJIS) PJI criteria preoperatively, out of 105 patients undergoing revision THA at our institution for possible PJI between November 2020 and December 2022. Intraoperatively, synovial fluid calprotectin was measured with LFI. Cases with calprotectin levels ≥ 50 mg/l were considered infected and treated with two-stage revision THA; in negative cases, one-stage revision was performed. At least five tissue cultures were obtained; the implants removed were sent for sonication. Results. Calprotectin was positive (≥ 50 mg/l) in 27 cases; out of these, 25 had positive tissue cultures and/or sonication. Calprotectin was negative in 21 cases. There was one false negative case, which had positive tissue cultures. Calprotectin showed an area under the curve of 0.917, sensitivity of 96.2%, specificity of 90.9%, positive predictive value of 92.6%, negative predictive value of 95.2%, positive likelihood ratio of 10.6, and negative likelihood ratio of 0.04. Overall, 45/48 patients were correctly diagnosed and treated by our algorithm, which included intraoperative calprotectin measurement. This yielded a 93.8% concordance with postoperatively assessed EBJIS criteria. Conclusion. Calprotectin can be a valuable tool in facilitating the intraoperative decision-making process for cases in which chronic PJI is suspected and diagnosis cannot be established preoperatively. Cite this article: Bone Joint J 2024;106-B(5 Supple B):118–124

Abstract. Objectives. There is renewed interest in bi-unicondylar arthroplasty (Bi-UKA) for patients with medial and lateral tibiofemoral osteoarthritis, but a spared patellofemoral compartment and functional cruciate ligaments. The bone island between the two tibial components may be at risk of tibial eminence avulsion fracture, compromising function. This finite element analysis compared intraoperative tibial strains for Bi-UKA to isolated medial unicompartmental arthroplasty (UKA-M) to assess the risk of avulsion. Methods. A validated model of a large, high bone-quality tibia was prepared for both UKA-M and Bi-UKA. Load totalling 450N was distributed between the two ACL bundles, implant components and collateral ligaments based on experimental and intraoperative measurements with the knee extended and appropriately sized bearings used. 95th percentile maximum principal elastic strain was predicted in the proximal tibia. The effect of overcuts/positioning for the medial implant were studied; the magnitude of these variations was double the standard deviation associated with conventional technique. Results. For all simulations, strains were an order of magnitude lower than that associated with bone fracture. Highest strain occurred in the spine, under the anteromedial ACL attachment, adjacent to transverse overcut of the medial component. Consequently, Bi-UKA had little effect on strain: <10% increases were predicted when compared to UKA-M with equivalent medial cuts/positioning. However, surgical overcutting/positional variation that resulted in loss of anteromedial bone in the spine increased strain. The biggest increase was for lateral translation of the medial component: 44% and 42% for UKA-M and Bi-UKA, respectively. Conclusions. For a large tibia with high bone quality, Bi-UKA with a well-positioned lateral implant had no tangible effect on the risk of tibial eminence avulsion fracture compared to UKA-M. Malpositioning of the medial component that removes bone from the anterior spine could prove problematic for smaller tibiae. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Objectives. High tibial osteotomy for knee realignment is effective at relieving symptoms of knee osteoarthritis but the operation is surgically challenging. A new personalised treatment with simpler surgery using pre-operatively planned measurements from computed tomography (CT) imaging and 3D-printed implants and instrumentation has been designed and is undergoing clinical trial. The aim of this study was to evaluate the early clinical results of a preliminary pilot study evaluating the safety of this new personalised treatment. Methods. The single-centre prospective clinical trial is ongoing (IRCCS Istituto Ortopedico Rizzoli; IRB-0013355; ClinicalTrials.gov NCT04574570), with recruitment completed and all patients having received the novel custom surgical treatment. To preserve the completeness of the trial reporting, only surgical aspects were evaluated in the present study. Specifically, the length of the implanted osteosynthesis screws was considered, being determined pre-operatively eliminating intraoperative measurements, and examined post-operatively (n=7) using CT image processing (ScanIP, Synopsys) and surface distance mapping. The surgical time, patient discharge date and ease of wound closure were recorded for all patients (n=25). Results. Over the study period the average surgical time (skin incision to suture) reduced from 54 to 31 minutes (range: 17–62, n=25). It was noted that wound closure was easier than the conventional surgery due to the lower profile of the implant. Over seventy percent of patients were discharged day 2 post-op. The position, orientation and length of all screws matched the pre-operative configuration to within approximately 1mm. Conclusions. The early trial results are promising from a clinical perspective. It was evident that surgical time was saved because no intraoperative screw length measurements were required, and the use of custom instrumentation significantly reduced the surgical inventory. The reduced invasiveness and ease of surgery may contribute to faster patient recovery compared to conventional techniques. The full trial results will be reported later this year. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Aims. The aim of this study was to evaluate the accuracy of implant placement when using robotic assistance during total hip arthroplasty (THA). Patients and Methods. A total of 20 patients underwent a planned THA using preoperative CT scans and robotic-assisted software. There were nine men and 11 women (n = 20 hips) with a mean age of 60.8 years (. sd. 6.0). Pelvic and femoral bone models were constructed by segmenting both preoperative and postoperative CT scan images. The preoperative anatomical landmarks using the robotic-assisted system were matched to the postoperative 3D reconstructions of the pelvis. Acetabular and femoral component positions as measured intraoperatively and postoperatively were evaluated and compared. Results. The system reported accurate values for reconstruction of the hip when compared to those measured postoperatively using CT. The mean deviation from the executed overall hip length and offset were 1.6 mm (. sd. 2.9) and 0.5 mm (. sd. 3.0), respectively. Mean combined anteversion was similar and correlated between intraoperative measurements and postoperative CT measurements (32.5°, . sd. 5.9° versus 32.2°, . sd. 6.4°; respectively; R. 2. = 0.65; p < 0.001). There was a significant correlation between mean intraoperative (40.4°, . sd. 2.1°) acetabular component inclination and mean measured postoperative inclination (40.12°, . sd. 3.0°, R. 2. = 0.62; p < 0.001). There was a significant correlation between mean intraoperative version (23.2°, . sd. 2.3°), and postoperatively measured version (23.0°, . sd. 2.4°; R. 2. = 0.76; p < 0.001). Preoperative and postoperative femoral component anteversion were significantly correlated with one another (R. 2. = 0.64; p < 0.001). Three patients had CT scan measurements that differed substantially from the intraoperative robotic measurements when evaluating stem anteversion. Conclusion. This is the first study to evaluate the success of hip reconstruction overall using robotic-assisted THA. The overall hip reconstruction obtained in the operating theatre using robotic assistance accurately correlated with the postoperative component position assessed independently using CT based 3D modelling. Clinical correlation during surgery should continue to be practiced and compared with observed intraoperative robotic values. Cite this article: Bone Joint J 2018;100-B:1303–9

Robotic-assisted technology in total knee arthroplasty (TKA) aims to increase implantation accuracy, with real-time data being used to estimate intraoperative component alignment. Postoperatively, Perth computed tomography (CT) protocol is a valid measurement technique in determining both femoral and tibial component alignments. The aim of this study was to evaluate the accuracy of intraoperative component alignment by robotic-assisted TKA through CT validation. A total of 33 patients underwent TKA using the MAKO robotic-assisted TKA system. Intraoperative measurements of both femoral and tibial component placements, as well as limb alignment as determined by the MAKO software were recorded. Independent postoperative Perth CT protocol was obtained (n.29) and compared with intraoperative values. Mean absolute difference between intraoperative and postoperative measurements for the femoral component were 1.17 degrees (1.10) in the coronal plane, 1.79 degrees (1.12) in the sagittal plane, and 1.90 degrees (1.88) in the transverse plane. Mean absolute difference between intraoperative and postoperative measurements for the tibial component were 1.03 degrees (0.76) in the coronal plane and 1.78 degrees (1.20) in the sagittal plane. Mean absolute difference of limb alignment was 1.29 degrees (1.25), with 93.10% of measurements within 3 degrees of postoperative CT measurements. Overall, intraoperatively measured component alignment as estimated by the MAKO robotic-assisted TKA system is comparable to CT-based measurements

INTRODUCTION. The restoration of physiological kinematics is one of the goals of a total knee arthroplasty (TKA). Navigation systems have been developed to allow an accurate and precise placement of the implants. But its application to the intraoperative measurement of knee kinematics has not been validated. The hypothesis of this study was that the measurement of the knee axis, femoral rotation, femoral translation with respect to the tibia, and medial and lateral femorotibial gaps during continuous passive knee flexion by the navigation system would be different from that by fluoroscopy taken as reference. MATERIAL – METHODS. Five pairs of knees of preserved specimens were used. The e.Motion FP ® TKA (B-Braun Aesculap, Tuttlingen, Germany) was implanted using the OrthoPilot TKA 4.3 version and Kobe version navigation system (B-Braun Aesculap, Tuttlingen, Germany). Kinematic recording by the navigation system was performed simultaneously with fluoroscopic recording during a continuous passive flexion-extension movement of the prosthetic knee. Kinematic parameters were extracted from the fluoroscopic recordings by image processing using JointTrack Auto ® software (University of Florida, Gainesville, USA). The main criteria were the axis of the knee measured by the angle between the center of the femoral head, the center of the knee and the center of the ankle (HKA), femoral rotation, femoral translation with respect to the tibia, and medial and lateral femorotibial gaps. The data analysis was performed by a Kappa correlation test. The agreement of the measurements was assessed using the intraclass correlation coefficient (ICC) and its 95% confidence interval. RESULTS. The respective CCIs were as follows: HKA angle 0.839 [0.820; 0.856]; femoral translation 0.560 [0.517; 0.600]; femoral rotation 0.652 [0.616; 0.686]; medial femorotibial gap 0.905 [0.894; 0.916]; lateral femorotibial gap 0.767 [0.740; 0.791]. DISCUSSION. Measurements of TKA kinematics by the navigation system and by fluoroscopy were consistent for HKA angle and medial and lateral femorotibial gaps, but not for femoral translation and femoral rotation. These differences can be explained by a methodological bias. At the end of this work, the specific navigation system cannot be considered as a reliable instrument for measuring the kinematics of a TKA

Introduction. Primary robotic-arm assisted total hip arthroplasty (THA) yields more accurate and reproducible acetabular cup placement, nonetheless, data is scarce in terms of outcomes. The purpose of the present study was to report on patient-reported outcomes (PROMs) in a large group of patients who underwent robotic-arm assisted THA. The authors hypothesized that (1) patients who underwent robotic-arm assisted primary THA would achieve favorable and significant improvement in PROMs, (2) an accurate and reproducible acetabular cup placement with respect to the defined SafeZones would be obtained, and (3) a low rate of THA dislocation would be observed. Methods. Prospectively collected data were retrospectively reviewed between April 2012 to May 2017. Primary THA using Mako Robotic-Arm [Mako Surgical Corp. (Stryker), Fort Lauderdale, FL, USA] with minimum two-year follow-up for the Harris Hip Score (HHS) and the Forgotten Joint Score-12 (FJS-12) were included. Exclusion criteria were: bodymass index (BMI) > 40 kg/m2, age < 21-year old, worker's compensation, or unwilling to participate. Visual analog scale (VAS) for pain and patient satisfaction were obtained. Intraoperative measurements for leg-length, global offset, acetabular inclination and version were documented. Results. 501 hips were included (57.29% females), follow-up was 43.99 ± 15.59 months. Average age was 58.70 ± 9.41 years, and the BMI was 28.41 ± 4.55 kg/m2. The group reported HHS of 90.87 ± 13.45, FJS-12 of 79.97 ± 25.87, VAS of 1.20 ± 2.06, and patient satisfaction of 8.85 ± 2.08. Intraoperative values for acetabular inclination and version were 40.0° ± 2.2 ° and 20.5° ± 2.4° respectively. Revision due to instability was 0.2%. Conclusions. Patients who received primary robotic-arm assisted THA reported excellent results at 44-month follow-up for multiple PROMs. Consistency in acetabular cup placement accuracy was achieved in regard to the Lewinnek and Callanan safe-zones

Introduction. Computer-assisted orthopaedic surgery (CAOS) has been shown to help achieve accurate, reliable and reproducible prosthesis position and alignment during total knee arthroplasty (TKA) [1]. A typical procedure involves inputting target resection parameters at the beginning of the surgery and measuring the achieved resection after bone cuts. Across CAOS systems, software/hardware design, mechanical instrumentation, and system-dependent work flow may vary, potentially affecting the intraoperative measurement of the achieved resection. This study assessed the cumulative effect of system-dependent differences between two CAOS systems by comparing the alignment deviation between the measurement of the achieved resection and the targeted parameters. Materials and Methods. TKA resections were performed on 10 neutral whole leg assemblies (MITA knee insert and trainer leg, Medial Models, Bristol, UK) by a board-certified orthopaedic surgeon (BH) using System I (5 legs, ExactechGPS®, Blue-Ortho, Grenoble, FR) and System II (5 legs, globally established manufacturer). The surgeon was deemed as “experienced” user (>30 surgeries) with both systems. The target parameters for the TKA resections, as well as major differences between the two systems are summarized in Table 1A. The deviations of the intraoperative alignment measurements on the achieved distal femoral and proximal tibial resection from the target were calculated and compared between the two systems with significance defined as p<0.05. Results. The alignment deviations (signed and unsigned) are presented in Table 1B. On average, System II had significantly higher deviation towards varus (2.2°) than System I (0.83° valgus) for the tibia (p<0.01) [Table 1B]. System I tended to measure slightly more in flexion (∼1°) than System II (∼0.5° extension) (p=0.03). System I demonstrated lower variability of the signed deviation (SD) than System II in tibial varus/valgus alignment, femoral flexion/extension, and femoral varus/valgus alignment [Fig. 1]. No significant differences were found in between systems in the unsigned errors. Both systems had measurement within the perceived acceptable range (within 3°) [2,3]. Discussion. Intraoperative measurement of the achieved TKA resections is important as it allows for intraoperative adjustment if the resections are not deemed suitable. Assuming a consistent surgical variability exhibited by the same surgeon with equal experience on both systems, this study demonstrated that some systems (System II) may have higher variability than others (System I), and exhibit clinically meaningful bias (tibial varus/valgus) while achieving or quantifying the resections. The variability may be caused by the cumulated effect of the differences between the two systems [see Table 1A]. As clinical alignment accuracy has been found to be system-dependent in a previous study [4], and archived resection parameters in the surgical report has been used as key inputs in relevant studies [5], the results here emphasizes the importance of taking into account the specific CAOS system in both clinical application and CAOS research. To view tables/figures, please contact authors directly

We evaluated 100 patients in two separate groups of 50 patients for Limb Length Discrepancy after Charnley Total Hip Arthroplasty. The study was a retrospective analysis of the group considered. Group 1 included 50 consecutive patients with unilateral disease who underwent total hip arthroplasty between June 98 – June 99 without intraoperative measurement. Group II included 50 patients with unilateral disease who underwent total hip arthroplasty between June 98 – July 99 with pre-operative templating and intraoperative measurements. Evaluation was undertaken with radiographs using the method of Williamson and Reckling. Two independent observers evaluated pre-operative radiographs and postoperative radiographs taken at a mean of 3 months (6 weeks – 6 months). The inter-oberserver variation was found in 9 preoperative radiographs and 15 postoperative radiographs in the 100 patients (p< 0.6). The mean age of the patients in Group I was 71 years and 4 months (52–83 years) with 24 males and 26 females. The mean age of patients in group II was 69 years and 7 months (41–82 years) with 25 males and 25 females. 23 patients (46%) in group I had a discrepancy of which 19 patients (38%) had a mean increase of o.4cm (0.1–0.8cm) and 4 patients (8%) had a mean decrease in length of 0.325cm (0.2–1.1cm). In group II 14 patients (28%) had a discrepancy with 9 patients (18%) had an mean increase of 0.41cm(0.1–1cm) and a mean decrease of 0.3cm(0.1–0.6cm). The discrepancy found in our series of 100 patients in minimal. The discrepancy can be minimised to a further extend with pre operative templating and intraoperative measurements (p< 0.04). Our study supports the adoption of this to prevent limb length discrepancy after total hip arthroplasty

Introduction. Evaluations of Computer-assisted orthopaedic surgery (CAOS) systems generally overlooked the intrinsic accuracy of the systems themselves, and have been largely focused on the final implant position and alignment in the reconstructed knee [1]. Although accuracy at the system-level has been assessed [2], the study method was system-specific, required a custom test bench, and the results were clinically irrelevant. As such, clinical interpolation/comparison of the results across CAOS systems or multiple studies is challenging. This study quantified and compared the system-level accuracy in the intraoperative measurements of resection alignment between two CAOS systems. Materials and Methods. Computer-assisted TKAs were performed on 10 neutral leg assemblies (MITA knee insert and trainer leg, Medial Models, Bristol, UK) using System I (5 legs, ExactechGPS®, Blue-Ortho, Grenoble, FR) and System II (5 legs, globally established manufacturer). The surgeries referenced a set of pre-defined anatomical landmarks on the inserts (small dimples). Post bone cut, the alignment parameters were collected by the CAOS systems (CAOS measured alignment). The pre- and post- operative leg surfaces were scanned, digitized, and registered (Comet L3D, Steinbichler, Plymouth, MI, USA; Geomagic, Lakewood, CO, USA; and Unigraphics NX version 7.5, Siemens PLM Software, Plano, TX, USA). The alignment parameters were measured virtually, referencing the same pre-defined anatomical landmarks (baseline). The signed and unsigned measurement errors between the baseline and CAOS measured alignment were compared between the two CAOS systems (significance defined as p<0.05), representing the magnitude of measurement errors and bias of the measurement error generated by the CAOS systems, respectively. Results. The measurement errors are presented [Table 1]. For unsigned measurement error, System II was higher in the tibial varus/valgus alignment and posterior slope (p≤0.01), and lower in the femoral varus/valgus alignment (p=0.03), compared to System I [Fig. 1]. System II exhibited higher error bias towards tibial varus alignment (up to 2.59°), more posterior slope (up to 1.41°), and more femoral hyper extension (up to 1.6°) than System I (p<0.01) [Fig. 1]. The mean signed and unsigned errors were generally less than 1°, except for System II in the measurement of tibial varus/valgus alignment (signed and unsigned mean errors=1.93°). Discussion. This study reported system-dependent bias and variability associated with intraoperative measurements of alignment parameters during TKA. The results showed that System I generally had lower variability and less bias than System II. Although the majority of the significant differences found were clinically irrelevant (<1° in means), System II was notably shown to produce on average ∼2° measurement errors in tibial varus/valgus alignment biased towards varus. Intra-operative measurement of surgical resection parameters during imageless computer-assisted TKA surgery is a critical step, in which a surgeon directly relies on the real-time data to prepare the bony resections and check the final realized cuts. Clinical-level accuracy in alignment outcomes has been shown to be system-dependent [2], this study further suggested there are differences in system-level accuracy between CAOS systems

In cases of poor bone quality intraoperative torque measurement might be an alternative to preoperative dual energy x-ray absorptiometry (DXA) to assess bone quality in Total Hip Arthroplasty (THA). 14 paired fresh frozen human femurs were included for trabecular peak torque measurement. We evaluated an existing intraoperative torque measurement method to assess bone quality and bone strength. We modified the approach to use this method in total hip arthroplasty (THA), which has not been published before. Since there are several approaches used in THA to exposure the hip joint, we decided to prefer the measurement in the femoral head which allows every surgeon to perform this measurement. Here a 6.5 × 23 mm blade was inserted into the proximal femur without harming the lateral cortical bone (figure 1). Further tests of the proximal femur evaluated the results of this new method: DXA, micro-computed tomography (μCT) and biomechanical load tests. Basic statistical analyses and multiple regressions were done. In the femoral head mean trabecular peak torque was 4.38 ± 1.86 Nm. These values showed a strong correlation with the values of the DXA, the μCT and the biomechanical load test. In comparison to the bone mineral density captured by DXA, the results of the intraoperative torque measurement showed a superior correlation with high sensitive bone quality evaluating methods (mechanical load tests and micro-computed tomography). Hence, the use of this intraoperative torque measurement seems to be more accurate in evaluating bone strength and bone quality than DXA during THA. The torque measurement provides sensitive information about the bone strength, which may affect the choice of implant in cases of poor bone stock and osteoporosis. In clinical use the surgeon may alter the prosthesis if the device indicates poor bone quality. Furthermore, we assume that the disadvantages associated with DXA scans like radiation exposure or errors caused by potential extraosteal sclerosis and interindividual soft-tissue artifacts could be excluded

Introduction. Radiographic assessment of acetabular fragment positioning during periacetabular osteotomy (PAO) is of paramount importance. Plain radiographic examination is time and resource intensive. Fluoroscopic based assessment is increasingly utilized but can introduce distortion. Our purpose was to determine the correlation of intraoperative fluoroscopy-based measurements with a fluoroscopic tool that corrects for distortion with postoperative plain-film measurements. Methods. We performed a prospective validation study on 32 PAO's (28 patients) performed by a single academic surgeon. Preoperative standing radiographs, intraoperative fluoroscopic images, and postoperative standing radiographs were evaluated with lateral center edge angle (LCEA), acetabular index (AI), posterior wall sign (PWS), and anterior center edge angle (ACEA). Intraoperative fluoroscopy was adjusted to account for pelvic inclination. The fluoroscopic GRID was utilized in all cases (Phantom MSK Hip Preservation, OrthoGrid LLC, Salt Lake City, UT). Intraoperative fluoroscopic measurements were compared to preoperative and postoperative standing radiographs at 6 weeks using linear regression applied in MINITAB. Results. All pre and post-correction measurements demonstrated excellent agreement within an average difference of 1.2 and 0.9 degrees (deg) respectively (p<0.01). Agreement between post-correction fluoroscopic GRID measurements and 6-week postoperative radiographs was: average difference for LCEA −0.4 deg (range −5 to 8 deg, SD 3.4), −0.9 deg for ACEA (range −16 to 7 deg, SD 5.1), and 0.3 deg for AI (range −8 to 6 deg, SD 3.3) (all p<.01). The PWS agreement was 93%. There was a tendency for fluoroscopic GRID measurements to underestimate acetabular coverage by less than 1 degree. Conclusion. Our study validated the use of a novel intraoperative fluoroscopic tool that accounts for fluoroscopic distortion and permits real-time measurements of PAO fragment correction that correlate accurately with postoperative evaluation. We believe that this tool adds value by giving surgeons reliable quantitative measurements of correction without interfering with surgical work-flow. For any tables or figures, please contact the authors directly

Introduction:. Acetabular component orientation has been linked to hip stability as well as bearing mechanics such as wear. Previous studies have demonstrated wide variations of cup placement in hip arthroplasty using conventional implantation techniques which rely upon either anatomic landmarks or the use of commercial positioning guides. Enabling technologies such as navigation have been used to improve precision and accuracy. Newer technologies such as robotic guidance have been postulated to further improve accuracy. The goal of our study was to evaluate the clinical reproducibility of a consecutive series of haptically guided THR. Methods:. 119 patients at 4 centers were enrolled. All patients had preoperative CT scans for the purpose of planning cup placement in lateral opening and version using proprietary software (Mako, Ft. Lauderdale, FL). All procedures were performed using a posterolateral approach. Following bone registration, acetabular preparation and component position is performed using haptic guidance. Final implant postion is ascertained by obtaining 5 points about the rim of the acetabular component and recorded. At 6 weeks, all patients had AP and cross-table lateral radiographs which were then analyzed for cup abduction and anteversion using the Hip Analysis Suite software. The goal was to determine the variability between desired preoperative plan, intraoperative measurement and postoperative results. Results:. Of the 119 hips replaced, 9 hips were excluded due to problems using the Hip Suite software leaving 110 hips for analysis. As seen in Table 1., the mean cup inclination was planned for 40.0 degrees. Intraoperative recorded inclination was 39.9 degrees and using the Martell software, 40.4 degrees. Planned cup anteversion was 18.7 degrees, with intraoperative measurement of 18.6 degrees and postoperative Hip Suite analysis 21.5 degrees. There was no significant difference between any of these measurements. Conclusion:. The use of a haptically guided robot to prepare and implant an acetabular component during total hip arthroplasty is both precise and accurate based upon this multicentered study. While further research determining optimal cup position is needed, these results suggest that the ability to achieve desired position is possible utilizing this enabling technology