Background. Biomechanical joint contact pressure distribution measurements have proven to be a very valuable tool in orthopaedic research to investigate the influence of surgical techniques such as total knee arthroplasty (TKA) on the human knee joint. Quantification of the in vitro tibiofemoral and patellofemoral contact pressure distribution before and after the intervention are an important measure to evaluate the impact of the surgery. The K scan pressure sensor from Tekscan (South Boston USA) is a commonly reported device for these in vitro pressure measurements. Despite the large interest in the sensor, the effective measurement accuracy for in vitro biomechanical joint contact measurement still remains a big question and therefore the reliability of these measurements should be questioned. Methods. Reliable contact pressure measurements can only be done if the sensor behaviour is fully understood. Therefore, a tailored multi-axial testing machine has been designed to profoundly investigate and characterise the sensor behaviour. This test setup is unique through its ability to apply a predefined tangential force or sliding velocity to the sensor's interface next to a normal force. Dynamic effects occurring in knee joint motion can thus be simulated while evaluating the effect on the contact pressure measurements. Results. The change in contact friction coefficient by insertion of the sensor in the joint is quantified. Different interface conditions (dry, lubricated with PTFE spray, lubricated with surgical lubricant) have been evaluated to obtain the best sliding conditions and to minimise the undesired sensor accuracy deteriorating effects. Conclusion. An optimal calibration procedure is put forward and side-effects that deteriorate the measurement accuracy are quantified. The provided knowledge facilitates orthopaedic biomechanics researchers to optimally perform joint contact measurements and to estimate the effective measurement accuracy. In addition, the presented rig provides the opportunity to study the inherent knee kinematics and prosthesis shape optimisation through the inherent degrees of freedom in the rig

Introduction

Wear of polyethylene inserts plays an important role in failure of total knee replacement and can be monitored in vivo by measuring the minimum joint space width in anteroposterior radiographs. The objective of this retrospective cross-sectional study was to compare the accuracy and precision of a new model-based method with the conventional method by analysing the difference between the minimum joint space width measurements and the actual thickness of retrieved polyethylene tibial inserts.

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

Aims. Femoral component anteversion is an important factor in the success of total hip arthroplasty (THA). This retrospective study aimed to investigate the accuracy of femoral component anteversion with the Mako THA system and software using the Exeter cemented femoral component, compared to the Accolade II cementless femoral component. Methods. We reviewed the data of 30 hips from 24 patients who underwent THA using the posterior approach with Exeter femoral components, and 30 hips from 24 patients with Accolade II components. Both groups did not differ significantly in age, sex, BMI, bone quality, or disease. Two weeks postoperatively, CT images were obtained to measure acetabular and femoral component anteversion. Results. The mean difference in femoral component anteversion between intraoperative and postoperative CT measurements (system accuracy of component anteversion) was 0.8° (SD 1.8°) in the Exeter group and 2.1° (SD 2.3°) in the Accolade II group, respectively (p = 0.020). The mean difference in anteversion between the plan and the postoperative CT measurements (clinical accuracy of femoral component anteversion) was 1.2° (SD 3.6°) in the Exeter group, and 4.2° (SD 3.9°) in the Accolade II group (p = 0.003). No significant differences were found in acetabular component inclination and anteversion; however, the clinical accuracy of combined anteversion was significantly better in the Exeter group (0.6° (SD 3.9°)) than the Accolade II group (3.6° (SD 4.1°)). Conclusion. The Mako THA system and software helps surgeons control the femoral component anteversion to achieve the target angle of insertion. The Exeter femoral component, inserted using Mako THA system, showed greater precision for femoral component and combined component anteversion than the Accolade II component. Cite this article: Bone Joint J 2024;106-B(3 Supple A):104–109

Primary care physicians rely on radiology reports to confirm a scoliosis diagnosis and inform the need for spine specialist referral. In turn, spine specialists use these reports for triage decisions and planning of care. To be a valid predictor of disease and management, radiographic evaluation should include frontal and lateral views of the spine and a complete view of the pelvis, leading to accurate Cobb angle measurements and Risser staging. The study objectives were to determine 1) the adequacy of index images to inform treatment decisions at initial consultation by generating a score and 2) the utility of index radiology reports for appropriate triage decisions, by comparing reports to corresponding images. We conducted a retrospective chart and radiographic review including all idiopathic scoliosis patients seen for initial consultation, aged three to 18 years, between January 1-April 30, 2021. A score was generated based on the adequacy of index images to provide accurate Cobb angle measurements and determine skeletal maturity (view of full spine, coronal=two, lateral=one, pelvis=one, ribcage=one). Index images were considered inadequate if repeat imaging was necessary. Comparisons were made between index radiology report, associated imaging, and new imaging if obtained at initial consultation. Major discrepancies were defined by inter-reader difference >15°, discordant Risser staging, or inaccuracies that led to inappropriate triage decisions. Location of index imaging, hospital versus community-based private clinic, was evaluated as a risk factor for inadequate or discrepant imaging. There were 94 patients reviewed with 79% (n=74) requiring repeat imaging at initial consultation, of which 74% (n=55) were due to insufficient quality and/or visualization of the sagittal profile, pelvis or ribcage. Of index images available for review at initial consult (n=80), 41.2% scored five out of five and 32.5% scored two or below. New imaging showed that 50.0% of those patients had not been triaged appropriately, compared to 18.2% of patients with a full score. Comparing index radiology reports to initial visit evaluation with <60 days between imaging (n=49), discrepancies in Cobb angle were found in 24.5% (95% CI 14.6, 38.1) of patients, with 18.4% (95% CI 10.0, 31.4) categorized as major discrepancies. Risser stage was reported in only 14% of index radiology reports. In 13.8% (n=13) of the total cohort, surgical or brace treatment was recommended when not predicted based on index radiology report. Repeat radiograph (p=0.001, OR=8.38) and discrepancies (p=0.02, OR=7.96) were increased when index imaging was obtained at community-based private clinic compared to at a hospital. Re-evaluation of available index imaging demonstrated that 24.6% (95% CI 15.2, 37.1) of Cobb angles were mis-reported by six to 21 degrees. Most pre-referral paediatric spine radiographs are inadequate for idiopathic scoliosis evaluation. Standardization of spine imaging and reporting should improve measurement accuracy, facilitate triage and decrease unnecessary radiation exposure

Introduction. Recent technological advancements have led to the introduction of robotic-assisted total knee arthroplasty to improve the accuracy and precision of bony resections and implant position. However, the in vivo accuracy is not widely reported. The primary objective of this study is to determine the accuracy and precision of a cut block positioning robotic arm. Method. Seventy-seven patients underwent total knee arthroplasty with various workflows and alignment targets by three arthroplasty-trained surgeons with previous experience using the ROSA® Knee System. Accuracy and precision were determined by measuring the difference between various workflow time points, including the final pre-operative plan, validated resection angle, and post-operative radiographs. The mean difference between the measurements determined accuracy, and the standard deviation represented precision. Results. The accuracy and precision for all angles comparing the final planned resection and validated resection angles was 0.90° ± 0.76°. The proportion within 3° ranged from 97.9% to 100%. The accuracy and precision for all angles comparing the final intra- operative plan and post-operative radiographs was 1.95 ± 1.48°. The proportion of patients within 3° was 93.2%, 95.3%, 96.6%, and 71.4% for the distal femur, proximal tibia, femoral flexion, and tibial slope angles when the final intra-operative plan was compared to post-operative radiographs. No patients had a postoperative complication requiring revision at the final follow-up. Conclusions. This study demonstrates that the ROSA Knee System has accurate and precise coronal plane resections with few outliers. However, the tibial slope demonstrated decreased accuracy and precision were measured on post-operative short-leg lateral radiographs with this platform

Aims. As an alternative to external fixators, intramedullary lengthening nails (ILNs) can be employed for distraction osteogenesis. While previous studies have demonstrated that typical complications of external devices, such as soft-tissue tethering, and pin site infection can be avoided with ILNs, there is a lack of studies that exclusively investigated tibial distraction osteogenesis with motorized ILNs inserted via an antegrade approach. Methods. A total of 58 patients (median age 17 years (interquartile range (IQR) 15 to 21)) treated by unilateral tibial distraction osteogenesis for a median leg length discrepancy of 41 mm (IQR 34 to 53), and nine patients with disproportionate short stature treated by bilateral simultaneous tibial distraction osteogenesis, with magnetically controlled motorized ILNs inserted via an antegrade approach, were retrospectively analyzed. The median follow-up was 37 months (IQR 30 to 51). Outcome measurements were accuracy, precision, reliability, bone healing, complications, and patient-reported outcome assessed by the Limb Deformity-Scoliosis Research Society Score (LD-SRS-30). Results. A median tibial distraction of 44 mm (IQR 31 to 49) was achieved with a mean distraction index of 0.5 mm/day (standard deviation 0.13) and median consolidation index of 41.2 days/cm (IQR 34 to 51). Accuracy, precision, and reliability were 91%, 92%, and 97%, respectively. New temporary range of motion limitations occurred in 51% of segments (34/67). Distraction-related equinus deformity treated by Achilles tendon lengthening was the most common major complication recorded in 16% of segments (11/67). In 95% of patients (55/58) the distraction goal was achieved with 42% unplanned additional interventions per segment (28/67). The median postoperative LD-SRS-30 score was 4.0 (IQR 3.6 to 4.3). Conclusion. Tibial distraction osteogenesis using motorized ILNs inserted via an antegrade approach appears to be a reliable and precise procedure. Temporary joint stiffness of the knee or ankle should be expected in up to every second patient. A high rate and wide range of complications of variable severity should be anticipated. Cite this article: Bone Joint J 2024;106-B(3):293–302

Recently, electromagnetic tracking for surgical procedures has gained popularity due to its small sensor size and the absence of line-of-sight restrictions. However, EM trackers are susceptible to measurement noise. Indeed, depending on the environment, measurement uncertainties may vary considerably. Therefore, it is important to characterise electromagnetic measurement systems when used in a fluoroscopy setting. The purpose of our study is to assess decoupled static electromagnetic measurement errors in position and orientation, without adding potential interference, in the presence of fluoroscopic imaging equipment. Using an Aurora electromagnetic tracking system (Northern Digital, Waterloo, Canada), 5 degrees of freedom measurements were collected in a working space located midway between the source and the receiver of a flat-panel 3D fluoroscope (Innova 4100, GE Healthcare, Buc, France) emitting X-rays. In addition, to determine potential EM distortion from X-rays, electromagnetic measurement accuracies, as a function of position, were compared before, during, and after X-ray emissions. To decouple position and orientation errors, two scaffold devices were designed. Their centre was placed approximately at X = −50, Y = 0, and Z = −300 mm in the EM tracker's global coordinate system. First the positioning scaffold was used to assess the position and orientation measurement uncertainties as a function of position. Next, the orienting scaffold was used to assess the position and orientation measurement uncertainties as a function of orientation. Then, a least-squares method was employed to register the path position measurements to the known geometry of the scaffolds. As a result, the position accuracy was defined as the Euclidean distance between the registered and the ground truth positions. Finally, the orientation accuracy was defined as the difference between two direct angles: the angle between two measured consecutive paths, and the angle of the corresponding ground truth. When translating the sensor using the positioning scaffold, the resulting position accuracy was characterised by a mean of 3.2 mm. Similarly, when rotating the sensor using the orienting scaffold, the resulting orientation accuracy was characterised by a mean of 1.7 deg. As for the “cross-displacement” errors, the orientation accuracy as a function of position had a mean of 1.8 deg. Likewise, the position as a function of orientation had a mean of 4.0 mm. Position and orientation accuracies – as a function of position, before, during, and after emission of X-rays – indicate that there was no significant interference by the presence of an X-ray beam on the EM measurements. This work provides evidence that placing the EM system into X-ray beams does not affect EM measurement accuracies. Nevertheless, the fluoroscope itself significantly increases the EM measurement errors. Careful analysis of the EM measurement distribution errors suggests that associated uncertainties are predictable and preventable. In essence, EM tracking is promising for orthopedic procedures that may require the use of a fluoroscope

Polyethylene (PE) wear particle induced osteolysis remains a major cause of failure in total hip arthroplasty (THA), so that routine clinical measurement of wear stays important. Crosslinked PE promises very low wear rates so that measurement accuracy becomes increasingly important to distinguish alternative materials. The rising use of large femoral heads causes lower linear head penetration also requiring improved accuracy. Digital x-rays and wear measurement software have become standard, but during archiving and exchange of x-rays, image format, resolution or compression are often changed without knowing the effects on wear measurement. This study investigates the effect of digital x-ray resolution and compression on the accuracy of two software programs to measure wear. The 8-year post-op digital x-rays of 24 THA patients (Stryker ABG-II, 28mm metal femoral head against Duration or conventional PE) were taken from the hospital PACS (Philips Diagnost H, AGFA ADC Solo, Siemens Medview) as DICOM at 5.1 MPix resolution. Images were converted to compression-free TIFF format using Irfanview V4.1. Wear (linear head penetration) was measured using Roman V1.7 and Martell Hip Analysis Suite 7.14. The x-rays were smoothened (Irfanview V4.1, Median Filter: 3) as recommended in literature for compatibility with Martell’s edge detection algorithm. Wear was measured twice by two independent observers at original format and resolution and then once by a single observer at three subsequently halved resolutions (2.6, 1.3, 0.65MPix) and three jpeg compressions (90%, 50%, 20%). Intra- and inter-observer reliability (R) was compared to the reliability of measuring manipulated images (Pearson’s r). The mean absolute wear differences (AD) were calculated versus the original x-ray. The mean total wear was 0.98+/−0.59mm (0.3–2.4mm) equaling an annual of wear rate of 0.11mm/yr. Using Roman, Intra-R (0.97) and Inter-R (0.96) were high and AD low (0.10 and 0.20mm). Reduced image resolution caused the R to drop only slightly to 0.95 (2.6MPix), 0.92 (1.3MPix) and 0.94 (0.65MPix) while AD remained low (< 0.20mm). Also compression hardly affected R (90%:0.96, 50%: 0.94, 20%:0.93) nor AD (< 0.20mm). Using Martell Intra-R (0.99) and Inter-R (0.87) were also high but dropped with reducing resolution (0.82, 0.72, 0.34, AD: 0.4–1.1mm) but hardly with increased compression (0.95, 0.92, 0.94, AD< 0.20mm). Low resolution and high compression do not have to be critical for wear measurement accuracy and reliability when edge detection is performed by a trained human eye. This way interpolating the ball and cup perimeters and locating their centers can be performed at accuracy below pixel size (ca. 0.40mm at 0.65MPix). Automatic edge detection is less robust to reducing resolution but performs at high compression. If image size needs to be reduced compression is preferable to reducing resolution

The December 2024 Children’s orthopaedics Roundup³⁶⁰ looks at: Establishing best practice for managing idiopathic toe walking in children: a UK consensus; Long-term outcomes of below-elbow casting in paediatric diaphyseal forearm fractures; Residual dysplasia risk persists in developmental dysplasia of the hip patients after Pavlik harness treatment; 3D printing in paediatricorthopaedics: enhancing surgical efficiency and patient outcomes; Pavlik harness treatment for hip dysplasia does not delay motor skill development in children; High prevalence of hip dysplasia found in adolescents with idiopathic scoliosis on routine spine radiographs; Minifragment plates as effective growth modulation for ulnar deformities of the distal radius in children; Long-term success of Chiari pelvic osteotomy in preserving hip function: 30-year follow-up study.

Aims

The Oxford Shoulder Score (OSS) is a 12-item measure commonly used for the assessment of shoulder surgeries. This study explores whether computerized adaptive testing (CAT) provides a shortened, individually tailored questionnaire while maintaining test accuracy.

Aims

The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients.

Purpose of the study: The accuracy, reproducibility and concordance of wear measurements made with the Imagika system were tested on knee prostheses. Material and methods: Anteroposterior radiographic images of implants with tibial inserts measuring 9, 7, and 11 mm thick were obtained, the tibial base had a 28 mm bead for calibration. The ap images were digitalized and variations in incidence were controlled with a plumb line. Combining the tilt positions from −10° to +10° and rotation from −5° to +5°, a total of 132 images were obtained. Four groups were defined according to tilt and rotation (±5°, ±3°). The images were read by to observers. Reproducibility and agreement were assessed for the overall series and for each of the four groups. Two images were read 40 times by the same observer using variable digital quality (100–300dpi) to determine measurement accuracy and error. Results were compared with the manufacturer’s data sheet. Results: Measurement agreement was poor in the four groups. Reproducibility was excellent at the 1% threshold for the overall series and for groups 3 and 4 for both observers. The accuracy improved from 0.6 to 0.5 mm by improving digitalization from 100 to 300 dpi with an error to the order of 0.05. Guiding the points used by the software for measurements, the accuracy could be improved to 0.25mm. The difference between the lateral plateau and the medial plateau appeared for the lesser tilt and for rotation greater than 2°. The thickness displayed was close only for the groups with little tilt. Discussion: The reproducibility and accuracy of the Imagika system can be brought below the 0.5 mm threshold. For views without tilt, the difference compared with the displayed values varied from 0.1 to 0.3mm. The agreement remains poor if the position of the measurement points is not predefined by the system. Conclusion: Offering an excellent reproducibility and good accuracy, the Imagika system enables monitoring TKA wear if the incidence of the radiographic images is perfectly controlled. For a more quantitative approach, the calibration method would have to be improved

Radiostereometric analysis (RSA) has become the gold standard technique for measuring implant migration and wear following joint replacement due to its high measurement precision and accuracy. However, RSA is conventionally performed using two oblique radiographic views with the presence of a calibration cage. Thus, a second set of radiographs must be acquired for clinical interpretation, for example anterior-posterior and cross-table lateral views following total hip arthroplasty (THA). We propose a modification to the RSA setup for examining THA, in which RSA measurements are performed from anterior-posterior and lateral views, with the calibration cage images acquired separately from the patient images. The objective of the current study was to compare the accuracy and precision of the novel technique to the conventional technique using a phantom. X-ray cassette holders were developed to enable simultaneous acquisition of anterior-posterior and cross-table lateral radiographs with the patient in a supine position in the RSA suite. A Sawbones phantom with total hip implant components was attached to a micrometer-driven stage. The femoral component was translated known distances relative to the acetabular cup in all planes, mimicking head penetration due to wear. Double RSA examinations were acquired for each increment using the traditional and novel radiograph orientations. Translations were measured from the radiographic images using RSA software. For both techniques, accuracy was calculated by comparing the measured translations to the known translation from the micrometer, and reported as the 95% confidence interval. Precision was measured by comparing the measured translations between the double exams, and reported as the standard deviation. Accuracy was greater for the conventional technique in the inferior-superior axis (p = 0.03), greater for the novel technique in the anterior-posterior axis (p = 0.01), and equivalent in the medial-lateral axis (p = 0.06). Overall accuracy for both the conventional and novel techniques was identical at ±0.022 mm. Precision was equivalent between both techniques for the medial-lateral (p = 0.68), inferior-superior (p = 0.14), and anterior-posterior axes (p = 0.86). Overall precision for the conventional technique was ±0.127 mm and for the novel technique was ±0.095 mm. Utilising standard clinical radiograph view angles within an RSA exam had no detrimental effect on wear measurement accuracy or precision. This reduces the barriers to implementing RSA imaging in routine follow-up of arthroplasty patients, potentially greatly increasing the numbers of patients that can have quantitative data on implant performance. Future applications can involve applying more clinically relevant radiograph view angles to RSA exams of the knee and shoulder

Model-image registration types of measurements have profoundly changed capabilities for studying dynamic 3D joint and implant kinematics since their introduction in the early 1990's. Since that time, a variety of proprietary and open-source software packages have been developed and reported for performing these measurements. Model-image registration based measurements have been used to quantify motions in natural and replaced knees, hips, ankles, shoulders, elbows, and spines in both single- and stereo-projection radiographic measurement setups. In theory, with the same quality images and the same quality bone/implant models, any of the software developed to perform model-image registration has the potential to provide equivalent measurement accuracy. Hence, much of the effort to improve measurement capabilities has been to reduce human interaction requirements and make the measurements more automatic and objective. In this paper, we report a new open-source software program that requires a minimum of user input to automate the 3D kinematic measurement process from single- or bi-plane radiographic projections. JointTrack Auto (JTA) is an open source (. sourforge.net/projects/jointtrackauto. ) program for performing model-image registration of metallic implants with single- or bi-plane radiographic images (see image). A predominantly edge-based cost function is used with an adaptive partioning global optimization scheme for model-image registration. Although this method works without any human intervention, JTA allows users to roughly identify one ‘feature’ of each implant that is visible in all images, e.g. the tip of a peg, to very significantly reduce the search space and time required for numerical optimization. This makes for a very convenient and fast initialization process where a human user simply mouse-clicks on a few easily identifiable locations in each radiographic image, and then the automated registration process is begun. Registration accuracy examples and a software demonstration will be included in this e-poster presentation to introduce attendees to the software and spur discussion about the various methods available to perform these important measurements

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

Introduction. High Tibial Osteotomy has become an increasingly popular management option for patients with painful medial compartment osteoarthritis. The Fujisawa method used to calculate the angle of correction is well-documented but there have been no studies to look at the reliability and accuracy of web-based systems to calculate this angle. Patients and Methods. Patients undergoing valgus high tibial osteotomy between October 2004 and February 2010 who had full-length lower-limb views on the Picture Archiving and Communications System (PACS). The Fujisawa angle and length of osteotomy were calculated by the surgeon and two Orthopaedic registrars who had been appropriately trained. Results. Thirty X-rays were reviewed in 28 patients. Mean difference between measurements was 0.43 mm (SD 2.45) There was a statistically significant correlation between all three raters (P < 0.001). The greatest correlation was between the Consultant and the more senior trainee (r=0.86) with the lowest correlation between the Consultant and the more junior trainee (r=0.70). Concordance correlation coefficient between raters varied from 0.81 to 0.63. Bland-Altman plot of agreement between the Consultant and senior trainee was excellent showing only two values lying outside 1.96 SD. Discussion. Comparison of measurements between raters showed increased accuracy with greater experience of the measurement technique. Despite this we show high correlation between raters with measurement accuracy of all raters found within clinically acceptable limits (< 1mm). Conclusion. Measurement of tibial osteotomy using the fujisawa method on a web-based X-ray interpretation system is accurate and reliable

Aims

Pelvic incidence (PI) is a position-independent spinopelvic parameter traditionally used by spinal surgeons to determine spinal alignment. Its relevance to the arthroplasty surgeon in assessing patient risk for total hip arthroplasty (THA) instability preoperatively is unclear. This study was undertaken to investigate the significance of PI relative to other spinopelvic parameter risk factors for instability to help guide its clinical application.

Objective. In total hip arthroplasty (THA), the femoral component influences leg length inequality and gait, and is associated with poor muscle strength and other unsatisfactory long-term results. We have therefore used intraoperative radiographs to acquire accurate measurements of femoral component size and position. At the last meeting of this society, we reported that accurate positioning was successfully achieved in 68 cases (87.2%) as a consequence of taking intraoperative radiographs. However, we have little understanding as regards to the accuracy of X-ray measurements. We accordingly undertook an examination of the accuracy of such measurements. The purpose of this study was to evaluate the difference between leg length discrepancy (LLD) measured using X-ray and computed tomography (CT). Materials and Methods. The study group comprised 48 primary THAs performed between October 2010 and April 2012. Using 2D template software (JMM Corporation), we measured LLD using pre-operative anteroposterior (AP) radiographs of the pelvis. On the basis of both teardrop lines, we measured LLD of the lesser trochanter top (Fig. 1), lesser trochanter direct top (Fig. 2), and trochanteric top (Fig. 3). Furthermore, using Aquarius NET software, we measured LLD using AP and lateral scout views of the pelvis and bilateral femurs. This data was defined as the true LLD. The difference between the X-ray data (lesser trochanter top, lesser trochanter direct top, and trochanteric top) and the CT data was defined as accuracy. Additionally, we measured the size of the lesser trochanter and examined the association. Results. The mean LLD was 11.4, 12.1, and 9.6 mm on the lesser trochanter top, the lesser trochanter direct top, and the trochanteric top of radiographs, respectively, and 11.6 mm on CT scans. Precision was within 5 mm of the true LLD in 42 cases (87.5%) for the lesser trochanter top, 36 cases (75.0 %) for the lesser trochanter direct top, and 27 cases (63.0%) for the trochanteric top. We observed no association between the size of the lesser trochanter and the measurement accuracy. Conclusions. When using X-ray measurements, the lesser trochanter top is the most useful site for LLD measurement

Introduction: Shoulder arthroplasty in rheumatoid patients gives satisfactory pain relief and some recovery of motion. Long term complications are however frequent, such as loosening of the glenoid and rotatorcuff insufficiency. Proximal migration (PM) might be related to both these conditions, and is assumed to lead to deterioration in function and recurrence of pain. Goal: Aim of this study was to evaluate the occurrence and identify risk factors for proximal migration after shoulder arthroplasty in a rheumatoid population. Methods and patients: Data of 102 patients (FU 5.8 yrs) treated with a shoulder arthroplasty for rheumatoid gleno-humeral disease was analysed. Requirements were at least 3 years of follow–up and 3 follow-up moments. At each visit clinical scores and standardised radiographs were performed prospectively. Rotator-cuff status was scored per-operatively. For quantification of PM a validated measurement technique - The Spina Humeral centre method- was used. A significant decrease of the subacromial space was defined as more than two times the standard deviation of the measurement accuracy (3.65 mm). Results: In 25 of 77 cases PM was present. PM commenced in two separate patterns, determined by the time-frame that passed before PM commenced. Early PM started directly during postoperative rehabilitation within the first two postoperative years, late PM after two years. This allowed group formation according to migration pattern; patients with no PM (PMnone), patients with late PM (PMlate) and those with early PM (PMearly). Age was higher in the PMearly group. Rotator cuff tears were more frequent and more severe in the PM groups. The ROM improved postoperatively in the PMnone and PMlate group, with deterioration of the latter in time. The HSS clinical outcome score improved in all groups. Quality of rotator cuff repair did not alter PM outcome. PM did not occur more frequently in hemi-artho-plasty compared to total shoulder arthroplasty. A more upward oriented glenoid was observed in the PMearly and PMlate groups