Objective. The purpose of this study was to determine the outcomes of revision ankle replacements, using the Invision implant and impaction allograft for massive talar dome defects following primary ankle replacement failure. Outcomes were assessed in terms of bone graft incorporation; improvement in patient reported outcome measures (PROMs); and survivorship of the revision ankle arthroplasty. Methods. A retrospective review of prospectively collected data identified eleven patients who had massive bone cysts and underwent revision of a failed primary total ankle replacement to the Invision revision system, combined with impaction grafting using morselized femoral head allograft. These revisions occurred at a single high volume ankle arthroplasty centre. Computed tomography (CT) scans were used to assess bone graft incorporation and the Manchester-Oxford Foot Questionnaire (MOXFQ) and EQ-5D scores were used pre and post operatively to assess PROMs. Results. The mean follow up was 18 months (12–48months). In all eleven patients, improvement was reported in the post-operative MOXFQ and EQ-5D scores. CT scans showed bone graft incorporation in all cases. None of the patients have required further surgery and are continue to do well clinically at latest follow up. Conclusions. In the short term, this study confirms revision ankle replacements with the Invision prosthesis and impaction with morselized femoral head allograft is a suitable revision option for primary ankle replacement failure with massive talar bone loss. Long term follow up continues of these complex patients

Aims. Management of intra-articular calcaneal fractures remains a debated topic in orthopaedics, with operative fixation often held in reserve due to concerns regarding perioperative morbidity and potential complications. The purpose of this study was to identify the characteristics of patients who developed surgical complications to inform the future stratification of patients best suited to operative treatment for intra-articular calcaneal fractures and those in whom surgery was highly likely to produce an equivocal functional outcome with potential post-operative complications. Methods. All patients who underwent open reduction and internal fixation of calcaneal fractures utilizing the Sinus Tarsi approach between March 2014 and July 2018 were identified using theatre records. Patient imaging was used to assess pre- and post-operative fracture geometry with Computed Tomography (CT) used for pre-operative planning. Each patient's clinical presentation was established through retrospective analysis of medical records. Patients provided verbal consent to participation and patient reported outcome measures were recorded using the Maryland Foot Score. Results. Fifty-eight intra-articular calcaneal fractures (fifty-three patients including five bilateral, mean age = 46.91 years) were included. Forty-nine patients were injured as a result of a fall from a height (92.4%). Mean time from presentation to surgery was 3.23 days (range 0–21). Mean Maryland Foot score was found to be 77.6 (+/− 16.22) in forty-five patients. Five patients (9.4%) had wound complications; two superficial (3.7%) and three deep (5.6%). Conclusion. Intra-articular fractures of the calcaneus should be considered for surgical intervention in order to improve long-term functional outcomes. The Sinus Tarsi approach provides the potential to decrease the operative complication rate whilst maintaining adequate fixation, however, the decision to surgically manage these fractures should be carefully balanced against the risk of post-operative complications. This increased risk of complication associated with smoking may tip the balance against benefit from surgical management

Total joint arthroplasty (TJA) is one of the commonest and most successful orthopaedic procedures used for the management of end-stage arthritis. With the recent introduction of robotic-assisted joint replacement, Computed tomography (CT) has become part of required pre-operative planning. The aim of this study is to quantify and characterise incidental CT findings, their clinical significance, and their effect on the planned joint arthroplasty. All consecutive patients undergoing an elective TJA (total joint arthroplasty; hip or knee) were retrospectively identified, over a 4-year period (December 2019 and November 2023). Data documented and analysed included patient demographics, type of joint arthroplasty, CT findings, their clinical significance, as well as potential delays to the planned arthroplasty because of these findings and subsequent further investigation. A total of 987 patients (female: 514 patients (52.1%)) undergoing TJA were identified (THA: 444 patients (45.0%); TKA: 400 patients (40.5%); UKA: 143 patients (14.5%)). Incidental findings within imaged areas were identified in 227 patients (23.0%). Of these findings, 74 (7.5%) were significant, requiring further investigation or management, 40 (4.1%) of which represented potential malignancy and 4 (0.4%) resulting in a new cancer diagnosis. A single patient was found to have an aneurysm requiring urgent vascular intervention. Surgery was delayed for further investigation in 4 patients (0.4%). Significant findings were more frequent in THA patients (THA: 43 (9.7%) TKA/UKA: 31 (5.7%). Within our cohort, 74 (7.5%) patients had significant incidental findings that required further investigations or management, with 4 (0.4%) having a previously undiagnosed malignancy. We strongly advocate that all robotic arthroplasty planning CTs are reviewed and reported by a specialist, to avoid missing undiagnosed malignancies and other significant diagnoses

Abstract. Objectives. The fidelity of a 3D model created using image segmentation must be precisely quantified and evaluated for the model to be trusted for use in subsequent biomechanical studies such as finite element analysis. The bones within the ankle joint vary significantly in size and shape. The purpose of this study was to test the hypothesis that the accuracy and reliability of a segmented bone geometry is independent of the particular bone being measured. Methods. Computed tomography (CT) scan data (slice thickness 1 mm, pixel size 808±7 µm) from three anonymous patients was used for the development of the ankle geometries (consisting of the tibia, fibula, talus, calcaneus, and navicular bones) using Simpleware Scan IP software (Synopsys, Exeter, UK). Each CT scan was segmented 4 times by an inexperienced undergraduate, resulting in a total of 12 geometry assemblies. An experienced researcher segmented each scan once, and this was used as the ‘gold standard’ to quantify the accuracy. The solid bone geometries were imported into CAD software (Inventor 2023, Autodesk, CA, USA) for measurement of the surface area and volume of each bone, and the distances between bones (tibia to talus, talus to navicular, talus to calcaneus, and tibia to fibula) were carried out. The intra-class coefficient (ICC) was used to assess intra-observer reliability. Bland Altman plots were employed as a statistical measure for criteria validity (accuracy) [1]. Results. The average ICC score was 0.93, which is regarded as a high reliability score for an inexperienced user. The talus to navicular and talus to tibia separations, which had the smallest distances, showed a slight decrease in reliability and this was observed for all separations shorter than 2 mm. According to the Bland-Altman plots, more than 95% of the data points were inside the borders of agreement, which is an excellent indication of accuracy. The bias percentage (average error percentage) varied between 1% and 4% and was constant across all parameters, with the proportion rising for short distance separations. Conclusions. The current study demonstrates that an inexperienced undergraduate, with access to software manuals, can segment an ankle CT scan with excellent reliability. The present study also concluded that all five bones were segmented with high levels of accuracy, and this was not influenced by bone volume or type. The only factor found to influence the reliability was the magnitude of distance between bones, where if this was smaller than 2 mm it reduced the reliability, indicating the influence of CT scan resolution on the segmentation reliability. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Introduction. Total joint arthroplasty (TJA) is one of the commonest and most successful orthopaedic procedures, used for the management of end-stage arthritis. With the recent introduction of robotic assisted joint replacement, Computed Tomography (CT) has become part of required pre-operative planning. The aim of this study is to quantify and characterise incidental CT findings, their clinical significance, and their effect on planned joint arthroplasty. Methodology. All consecutive patients undergoing an elective TJR (hip or knee arthroplasty) were retrospectively identified, over a 3-year period (December 2019 and December 2022). Data documented and analysed included patient demographics, type of joint arthroplasty, CT findings, their clinical significance, as well as potential delays to the planned arthroplasty because of these findings and subsequent further investigation. Results. A total of 624 patients (637 studies, 323 (51.8%) female, 301 (48.2%) male) were identified of which 163 (25.6%) showed incidental findings within the long bones or pelvis. Of these 52 (8.2%) were significant, potentially requiring further management, 32 (5.0%) represented potential malignancy and 4 (0.6%) resulted in a new cancer diagnosis. Conclusion. It is not currently national standard practice to report planning CT imaging as it is deemed an unnecessary expense and burden on radiology services. Within the study cohort 52 (8.2%) of patients had a significant incidental finding that required further investigation or management and 4 (0.6%) had a previously undiagnosed malignancy. In order to avoid the inevitability of a missed malignancy on a planning CT, we must advocate for formal reports in all cases

Aneurysmal bone cyst (ABC) of the spine is a locally aggressive benign lesion which can be treated by en bloc resection with wide margin to reduce the risk of local recurrence. To avoid morbidity associated with surgery, selective arterial embolization (SAE) can be considered the first-line treatment for ABCs of the spine. We previously introduced the use of autologous bone marrow concentrate (BMC) injection therapy to stimulate bone healing and regeneration in ABC of the spine. In this prospective study we described the clinical and radiological outcomes of percutaneous injection of autologous BMC in a series of patients affected by ABCs of the spine. Fourteen patients (6 male, 8 female) were treated between June 2014 and December 2019 with BMC injection for ABC of the spine. The mean age was 17.85 years. The mean follow up was 37.4 months (range 12–60 months). The dimension of the cyst and the degree of ossification were measured by Computed Tomography (CT) scans before the treatment and during follow-up visits. Six patients received a single dose of BMC, five patients received two doses and in three patients three doses of BMC were administered. The mean ossification of the cyst (expressed in Hounsfield units) increased statistically from 43.48±2.36 HU to 161.71±23.48 HU during follow-up time and the ossification was associated to an improvement of the clinical outcomes. The mean ossification over time was significantly higher in patients treated with a single injection compared to patients treated with multiple injections. No significant difference in ossification was found between cervical and non-cervical localization of the cyst. Moreover, the initial size of the cyst was not statistically associated with the degree of ossification during follow-up. The results of this study reinforce our previous evidence on the use of BMC as a valid alternative for spinal ABC management when SAE is contraindicated or ineffective. The initial size of the cyst and its localization does not influence the efficacy of the treatment. However, data suggest that BMC injection could be indicated as treatment of choice for spinal ABC in young adolescent women

Worldwide, most spine imaging is either “inappropriate” or “probably inappropriate”. The Choosing Wisely recommendation is “Do not perform imaging for lower back pain unless red flags are present.” There is currently no detailed breakdown of lower back pain diagnostic imaging performed in New Brunswick (NB) to inform future directions. A registry of spine imaging performed in NB from 2011-2019 inclusive (n=410,000) was transferred to the secure platform of the NB Institute for Data, Training and Research (NB-IRDT). The pseudonymized data included linkable institute identifiers derived from an obfuscated Medicare number, as well as information on type of imaging, location of imaging, and date of imaging. The transferred data did not include the radiology report or the test requisition. We included all lumbar, thoracic, and complete spine images. We excluded imaging related to the cervical spine, surgical or other procedures, out-of-province patients and imaging of patients under 19 years. We verified categories of X-ray, Computed Tomography (CT), and Magnetic Resonance Imaging (MRI). Red flags were identified by ICD-10 code-related criteria set out by the Canadian Institute for Health Information. We derived annual age- and sex-standardized rates of spine imaging per 100,000 population and examined regional variations in these rates in NB's two Regional Health Authorities (RHA-A and RHA-B). Age- and sex-standardized rates were derived for individuals with/without red flag conditions and by type of imaging. Healthcare utilization trends were reflected in hospital admissions and physician visits 2 years pre- and post-imaging. Rurality and socioeconomic status were derived using patients’ residences and income quintiles, respectively. Overall spine imaging rates in NB decreased between 2012 and 2019 by about 20% to 7,885 images per 100,000 people per year. This value may be higher than the Canadian average. Females had 23% higher average imaging rate than males. RHA-A had a 45% higher imaging rate than RHA-B. Imaging for red flag conditions accounted for about 20% of all imaging. X-rays imaging accounted for 67% and 75% of all imaging for RHA-A and RHA-B respectively. The proportions were 20% and 8% for CT and 13% and 17% for MRI. Two-year hospitalization rates and rates of physician visits were higher post-imaging. Females had higher age-standardized hospitalization and physician-visit rates, but the magnitude of increase was higher for males. Individuals with red flag conditions were associated with increased physician visits, regardless of the actual reason for the visit. Imaging rates were higher for rural than urban patients by about 26%. Individuals in the lowest income quintiles had higher imaging rates than those in the highest income quintiles. Physicians in RHA-A consistently ordered more images than their counterparts at RHA-B. We linked spine imaging data with population demographic data to look for variations in lumbar spine imaging patterns. In NB, as in other jurisdictions, imaging tests of the spine are occurring in large numbers. We determined that patterns of imaging far exceed the numbers expected for ‘red flag’ situations. Our findings will inform a focused approach in groups of interest. Implementing high value care recommendations pre-imaging ought to replace low-value routine imaging

Abstract

Introduction and Objective. Curative resection of proximal humerus tumours is now possible in this era of limb salvage with endoprosthetic replacement considered as the preferred reconstructive option. However, it has also been linked with mechanical and non-mechanical failures such as stem fracture and aseptic loosening. One of the challenges is to ensure that implants will endure the mechanical strain under physiological loading conditions, especially crucial in long surviving patients. The objective is to investigate the effect of varying prosthesis length on the bone and implant stresses in a reconstructed humerus-prosthesis assembly after tumour resection using finite element (FE) modelling. Methods. Computed tomography (CT) scans of 10 humeri were processed in Mimics 17 to create three-dimensional (3D) cortical and cancellous solid bone models. Endoprostheses of different lengths manufactured by Stryker were modelled using Solidworks 2020. The FE models were divided into four groups namely group A consisting of the intact humerus and groups B, C and D composed of humerus-prosthesis assemblies with a body length of 40, 100 and 120 mm respectively and were meshed using linear 4-noded tetrahedral elements in 3matic 13. The models were then imported into Abaqus CAE 6.14. Isotropic linear elastic behaviour with an elastic modulus of 13400, 2000 and 208 000 MPa were assigned to the cortical bone, cancellous bone and prosthesis respectively and a Poisson's ratio of 0.3 was assumed for each material. To represent the lifting of heavy objects and twisting motion, a tensile load of 200 N for axial loading and a 5 Nm torsional load for torsional loading was applied separately to the elbow joint surface with the glenohumeral joint fixed and with all contact interfaces defined as fully bonded. A comparative analysis against literature was performed to validate the intact model. Statistical analysis of the peak von Mises stress values collected from predicted stress contour plots was performed using a one-way repeated measure of analysis of variance (with a Bonferroni post hoc test) using SPSS Statistics 26. The average change in stress of the resected models from the intact state were then determined. Results. The validation of the intact humerus displayed a good agreement with literature values. The peak bone stress occurred distally above the coronoid and olecranon fossa closer to the load application region in the intact and resected bone models with a significant amount of loading borne by the cortical bone, while the peak implant stress occurred at the bone-prosthesis contact interface under both loading conditions. Based on the results obtained, a statistically significant difference (p =.013) in implant stress was only seen to occur between groups B and C under tension. Results illustrate initiation of stress shielding with the bone bearing lesser stress with increasing resection length which may eventually lead to implant failure by causing bone resorption according to Wolff's law. The peak implant stress under torsion was 3–5 times the stress under tension. The best biomechanical behaviour was exhibited in Group D, having the least average change in stress from the intact model, 5% and 3.8% under tension and torsion respectively. It can be deduced that the shorter the prosthesis length, the more pronounced the effect on cortical bone remodelling. With the maximum bone and implant stresses obtained being less than their yield strength, it can be concluded that the bone-implant construct is safe from failure. Conclusions. The developed FE models verified the influence of varying the prosthesis length on the bone and implant stresses and predicted signs of stress shielding in longer endoprostheses. By allowing for 2 cm shortening in the upper extremity and post-surgical scarring, it is beneficial to err towards a shorter endoprosthesis

Introduction and Objective. Aneurysmal bone cyst (ABC) of the spine is a locally aggressive benign lesion which can be treated by en bloc resection with wide margin to reduce the risk of local recurrence. To avoid morbidity associated with surgery, selective arterial embolization (SAE) can be considered the first-line treatment for ABCs of the spine. Other emerging treatments for ABCs include bisphosphonates, percutaneous doxycycline, sclerotherapy and Denosumab. In addition, we previously introduced the use of autologous bone marrow concentrate (BMC) injection therapy to stimulate bone healing and regeneration in ABC of the spine. One of the potential advantages of such a method is that surgical treatments are not necessary, thus allowing for both a minimally invasive approach and the treatment of poorly accessible lesions. In this prospective study we described the clinical and radiological outcomes of percutaneous injection of autologous BMC in a series of patients affected by ABCs of the spine and followed for at least one year. Materials and Methods. Fourteen patients (6 male, 8 female) were treated between June 2014 to December 2019 with BMC injection for ABC of the spine. The mean age was 17.85 years. The mean follow up was 37.4 months (range 12– 60 months). The dimension of the cyst and the degree of ossification were measured by Computed Tomography (CT) scans before the treatment and during follow-up visits. Results. Six patients received a single dose of BMC, five patients received two doses and in three patients three doses of BMC were administered. The mean ossification of the cyst (expressed in Hounsfield units) increased statistically from 43.48±2.36 HU to 161.71±23.48 HU during follow-up time and the ossification was associated to an improvement of the clinical outcomes. The mean ossification over time was significantly higher in patients treated with a single injection compared to patients treated with multiple injections. No significant difference in ossification was found between cervical and non-cervical localization of the cyst. Moreover, the initial size of the cyst was not statistically associated with the degree of ossification during follow-up. We also observed that five out of six female patients (83.3%) were less than sixteen years old and four of these (66.7%) were managed with a single dose of BMC injection, while a higher percentage of male patients (6/8, 75%) were more than sixteen years old and more than one injection was administered to them. Conclusions. The results of this study reinforce our previous evidence on the use of BMC as a valid alternative for spinal ABC management when SAE is contraindicated or ineffective. The initial size of the cyst and its localization does not influence the efficacy of the treatment. However, BMC injection could be indicated as treatment of choice for spinal ABC in young adolescent women

Introduction and Objective. Virtual Surgical Planning (VSP) is becoming an increasingly important means of improving skills acquisition, optimizing clinical outcomes, and promoting patient safety in orthopedics and traumatology. Pediatric Orthopedics (PO) often deals with the surgical treatment of congenital or acquired limbs and spine deformities during infancy. The objective is to restore function, improve aesthetics, and ensure proper residual growth of limbs and spine, using osteotomies, bone grafts, age-specific or custom-made hardware and implants. Materials and Methods. Three-dimensional (3D) digital models were generated from Computed Tomography (CT) scans, using free open-source software, and the surgery was planned and simulated starting from the 3D digital model. 3D printed sterilizable models were fabricated using a low-cost 3D printer, and animations of the operation were generated with the aim to accurately explain the operation to parents. All procedures were successfully planned using our VSP method and the 3D printed models were used during the operation, improving the understanding of the severely abnormal bony anatomy. Results. The surgery was precisely reproduced according to VSP and the deformities were successfully corrected in eight cases (3 genu varum in Blount disease, 2 coxa vara in pseudo achondroplasia, 1 SCFE, 1 missed Monteggia lesion and 1 post-traumatic forearm malunion deformity). In one case, a focal fibrocartilaginous dysplasia, the intraoperative intentional undersizing of the bone osteotomy produced an incomplete correction of a congenital forearm deformity. Conclusions. Our study describes the application of a safe, effective, user-friendly, VSP process in PO surgery. We are convinced that our study will stimulate the widespread adoption of this technological innovation in routine clinical practice for the treatment of rare congenital and post-traumatic limb deformities during childhood

Aims

We quantitatively compared the 3D bone density distributions on CT scans performed on scaphoid waist fractures subacutely that went on to union or nonunion, and assessed whether 2D CT evaluations correlate with 3D bone density evaluations.

Spinal stenosis is a condition resulting in the compression of the neural elements due to narrowing of the spinal canal. Anatomical factors including enlargement of the facet joints, thickening of the ligaments, and bulging or collapse of the intervertebral discs contribute to the compression. Decompression surgery alleviates spinal stenosis through a laminectomy involving the resection of bone and ligament. Spinal decompression surgery requires appropriate planning and variable strategies depending on the specific situation. Given the potential for neural complications, there exist significant barriers to residents and fellows obtaining adequate experience performing spinal decompression in the operating room. Virtual teaching tools exist for learning instrumentation which can enhance the quality of orthopaedic training, building competency and procedural understanding. However, virtual simulation tools are lacking for decompression surgery. The aim of this work was to develop an open-source 3D virtual simulator as a teaching tool to improve orthopaedic training in spinal decompression. A custom step-wise spinal decompression simulator workflow was built using 3D Slicer, an open-source software development platform for medical image visualization and processing. The procedural steps include multimodal patient-specific loading and fusion of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) data, bone threshold-based segmentation, soft tissue segmentation, surgical planning, and a laminectomy and spinal decompression simulation. Fusion of CT and MRI elements was achieved using Fiducial-Based Registration which aligned the scans based on manually placed points allowing for the identification of the relative position of soft and hard tissues. Soft tissue segmentation of the spinal cord, the cerebrospinal fluid, the cauda equina, and the ligamentum flavum was performed using Simple Region Growing Segmentation (with manual adjustment allowed) involving the selection of structures on T1 and/or T2-weighted scans. A high-fidelity 3D model of the bony and soft tissue anatomy was generated with the resulting surgical exposure defined by labeled vertebrae simulating the central surgical incision. Bone and soft tissue resecting tools were developed by customizing manual 3D segmentation tools. Simulating a laminectomy was enabled through bone and ligamentum flavum resection at the site of compression. Elimination of the stenosis enabled decompression of the neural elements simulated by interpolation of the undeformed anatomy above and below the site of compression using Fill Between Slices to reestablish pre-compression neural tissue anatomy. The completed workflow allows patient specific simulation of decompression procedures by staff surgeons, fellows and residents. Qualitatively, good visualization was achieved of merged soft tissue and bony anatomy. Procedural accuracy, the design of resecting tools, and modeling of the impact of bone and ligament removal was found to adequately encompass important challenges in decompression surgery. This software development project has resulted in a well-characterized freely accessible tool for simulating spinal decompression surgery. Future work will integrate and evaluate the simulator within existing orthopaedic resident competency-based curriculum and fellowship training instruction. Best practices for effectively teaching decompression in tight areas of spinal stenosis using virtual simulation will also be investigated in future work

Anteroposterior (AP) pelvic radiographs are the standard tool used for pre-operative planning and post-operative evaluation during total hip arthroplasty (THA). The accuracy of this imaging modality is, however, limited by errors in pelvic orientation and image distortion. Pelvic obliquity is corrected for by orienting measurements to a reference line such as the interteardrop line or the interischial line, while several methods for correcting for pelvic tilt have been suggested, with varying levels of success. To date, no reliable method for correcting for pelvic rotation on pelvic imaging is available. The purpose of this study was to evaluate a novel method for correcting pelvic rotation on a standard anteroposterior (AP) radiographs. Computed tomography (CT) scans from 10 male cadavers and 10 female THA patients were segmented using 3D Slicer and used to create 3D renderings for each pelvis. Synthetic AP radiographs were subsequently created from the 3D renderings, using XRaySim. For each pelvis, images representing pelvic rotation of 30° left to 30° right, at 5° increments were created. Four unique parameters based on pelvic landmarks were used to develop the correction method: i) the horizontal distance from the upper edge of the pubic symphysis to the sacroiliac joint midline (PSSI), ii) the ratio of the horizontal distances from the upper edge of the pubic symphysis to the outer lateral border of both obturator foramina (PSOF), iii) the width ratio of the obturator foramina (OFW) and iv) the ratio of the horizontal distance from each anterior superior iliac spine to the sacroiliac joint midline (ASISSI). The relationships between the chosen parameters and pelvic rotation were investigated using a series of 260 (13 per pelvis) synthetic AP radiographs. Male and female correction equations were generated from the observed relationships. Validation of the equations was done using a different set of 50 synthetic radiographs with known degrees of rotation. In males, the PSSI parameter was most reliable in measuring pelvic rotation. In females, PSOF was most reliable. A high correlation was noted between calculated and true rotation in both males and females (r=0.99 male, r=0.98 female). The mean difference from the male calculated rotation and true rotation value was 0.02°±1.8° while the mean difference from the female calculated rotation and true rotation value was −0.01°±1.5°. Our correction method for pelvic rotation using four pelvic parameters provides a reliable method for correcting pelvic rotation on AP radiographs. For any figures or tables, please contact authors directly

Introduction. Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes. Robotic-assisted (RA) total knee arthroplasty has demonstrated improved accuracy to plan in cadaver studies compared to conventionally instrumented (manual) TKA, but less clinical evidence has been reported. The objective of this study was to compare the three-dimensional accuracy to plan of RATKA with manual TKA for overall limb alignment and component position. Methods. A non-randomized, prospective multi-center clinical study was conducted to compare RATKA and manual TKA at 4 U.S. centers between July 2016 and August 2018. Computed tomography (CT) scans obtained approximately 6 weeks post-operatively were analyzed using anatomical landmarks. Absolute deviation from surgical plans were defined as the absolute value of the difference between the CT measurements and surgeons’ operative plan for overall limb, femoral and tibial component mechanical varus/valgus alignment, tibial component posterior slope, and femoral component internal/external rotation. We tested the differences of absolute deviation from plan between manual and RATKA groups using stratified Wilcoxon tests, which controlled for study center and accounted for skewed distributions of the absolute values. Alpha was 0.05 two-sided. At the time of this abstract, data collections were completed for two centers (52 manual and 58 RATKA). Results. Comparing absolute deviation from plan between groups, RATKA demonstrated clear benefits for tibial component alignment (median absolute deviation from plan: 1.5° vs. 0.8°, manual vs RATKA, p<.001), tibial slope (2.7° vs. 1.1°, manual vs RATKA, p<.001), and femoral component rotation (1.4° vs. 0.9°, manual vs RATKA, p<0.02). Femoral component and overall limb alignment accuracy were comparable (p>0.10). Discussion and Conclusions. In this study, compared to manual TKA, RATKA cases were 47% more accurate for tibial component alignment, 59% more accurate for tibial slope, and 36% more accurate for femoral component rotation (percent differences of median absolute deviations from plan). Further clinical data is needed to study the longer-term benefits of robotic technologies. Nevertheless, this study supports improved accuracy to plan utilizing RATKA compared to manual TKA. For any figures or tables, please contact authors directly

Introduction. Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes. 1. The objective of this study was to compare the accuracy to plan of three-dimensional modeled (3D) TKA with manual TKA for component alignment and position. Methods. An open-label prospective clinical study was conducted to compare 3D modeling with manual TKA (non-randomized) at 4 U.S. centers between July 2016 and August 2018. Men and women aged > 18 with body mass index < 40kg/m. 2. scheduled for unilateral primary TKA were recruited for the study. 144 3DTKA and 86 manual TKA (230 patients) were included in the analysis of accuracy outcomes. Seven high-volume, arthroplasty fellowship-trained surgeons performed the surgeries. The surgeon targeted a neutral (0°) mechanical axis for all except 9 patients (4%) for whom the target was within 0°±3°. Computed tomography (CT) scans obtained approximately 6 weeks post-operatively were analyzed using anatomical landmarks to determine femoral and tibial component varus/valgus position, femoral component internal/external rotation, and tibial component posterior slope. Absolute deviation from surgical plan was defined as the absolute value of the difference between the CT measurement and the surgeon's operative plan. Smaller absolute deviation from plan indicated greater accuracy. Mean component positions for manual and 3DTKA groups were compared using two-sample t tests for unequal variances. Differences of absolute deviations from plan were compared using stratified Wilcoxon tests, which controlled for study center and accounted for skewed distributions of the absolute values. Alpha was 0.05 two-sided. At the time of this report, CT measurements of femoral component rotation position referenced from the posterior condylar axis were not yet completed; therefore, the current analysis of femoral component rotation accuracy to plan reflects one center that exclusively used manual instruments referencing the transepicondylar axis (TEA). Results. Coronal positions of the femoral components measured via CT for manual and 3D TKA, respectively, were (mean ± standard deviation) 0.1°±1.6° varus and 0.0°±1.4° varus (p=0.533); positions of the tibial components were 1.9°±2.4° varus and 0.9°±2.0° varus (p=0.002). Positions of external femoral component rotation relative to the TEA were 1.1°±2.3° and 0.5°±2.3°, respectively (p=0.036). Tibial slopes were 3.7°±3.0° and 3.2°±1.8°, respectively (p=0.193). Comparing absolute deviation from plan between groups, 3DTKA demonstrated greater accuracy for tibial component alignment [median (25. th. , 75. th. percentiles) absolute deviation from plan, 1.7° (0.9°, 2.9°) vs. 0.9°(0.4°, 1.9°), p<.001], femoral component rotation [1.4° (0.9°, 2.5°) vs. 0.9° (0.7°, 1.5°), p=0.015], and tibial slope [2.9° (1.5°, 5.0°) vs. 1.1° (0.6°, 2.0°), p<.001] (Table 1). Accuracy for femoral component alignment was comparable [1.0° (0.4°, 1.7°) vs. 0.9° (0.4°, 1.5°), p=0.159] (Table 1). Discussion and Conclusions. Our findings support improved accuracy to the surgical plan utilizing 3DTKA compared with manual TKA. Compared to manual TKA, 3DTKA cases were typically 47% more accurate for tibial component alignment, 62% more accurate for tibial slope, and 36% more accurate for femoral component rotation (calculated as percent reduction of median absolute deviation). The evaluation of femoral component coronal alignment reflected already very good baseline accuracy of the surgeons utilizing the intramedullary femoral guide system (Table 1). As optimal component position in TKA affects joint kinematics and may positively influence implant longevity, it is important for surgeons to maximize the opportunity to direct component positioning. Further clinical data is needed to study potential longer-term benefits of robotic technologies. For figures, tables, or references, please contact authors directly

Introduction. Tibial tuberosity and trochlear groove (TT-TG) distance has been investigated for the patients with primary patellofemoral subluxation/dislocation. To date, TT-TG distance after TKA has not been evaluated, and the effect of postoperative TT-TG distance on patellar tracking is unknown. The purpose of the current study was to investigate the effect of TT-TG distance and rotational position of the femoral and tibial components on patellar tilt after TKA. Methods. Consecutive 115 knees for the diagnosis of osteoarthritis were included in the current study. TKA was performed using posterior cruciate ligament sacrificed prosthesis. A total of 17 men and 96 women with an average age of 75.3 years were included at the time of the surgery. Computed tomography (CT) was taken after TKA in full extension. Postoperative TT-TG distance was measured as a reference of surgical epicondylar axis (SEA) of the femur. Patellar tilt was defined as the angle of the patellar component relative to SEA. Femoral and tibial component rotation was measured as the angle relative to SEA and tibial antero-posterior (AP) axis. Tibial AP axis was defined as the line connecting medial one-third of the tibial tuberosity and center of medial-lateral width. Pearson correlation coefficients were calculated to determine the correlations between patellar tilt and TT-TG distance and between patellar tilt and femoral and tibial component rotation. Results. TT-TG distance had significant correlation with patellar tilt (Figure 1; r = 0.254, p = 0.006), whereas femoral component rotation (p = 0.092) and tibial component rotation (p = 0.062) were not correlated with patellar tilt. Concerning the effect on TT-TG distance, femoral component rotation (r = 0.248, p = 0.008) and tibial component rotation (r = −0.567, p < 0.001) were correlated with TT-TG distance. Conclusion. The current study investigated the effect of TT-TG distance on patellar tilt with postoperative CT scan. Greater TT-TG distance resulted in more patellar tilt, which might have negative effects on patellar tracking. In previous clinical studies, femoral component and tibial component rotation affected patellar maltracking. In the current study, however, component rotation itself did not affect patellar tilt. Postoperative TT-TG distance includes information of rotational and medial-lateral positioning of the femoral and tibial components, and can be a useful indicator to predict patellar maltracking after TKA. For any figures or tables, please contact authors directly

Ceramic-on-ceramic bearings provide a solution to the osteolysis seen with traditional metal-on-polyethylene bearings. Sporadic reports of ceramic breakage and squeaking concern some surgeons and this bearing combination can show in vivo signs of edge loading wear which was not predicted from in vitro studies. Taper damage or debris in the taper between the ceramic and metal may lead to breakage of either a ceramic head or insert. Fastidious surgical technique may help to minimise the risk of ceramic breakage. Squeaking is usually a benign complication, most frequently occurring when the hip is fully flexed. Rarely, it can occur with each step of walking when it can be sufficiently troublesome to require revision surgery. The etiology of squeaking is multifactorial in origin. Taller, heavier and younger patients with higher activity levels are more prone to hips that squeak. Cup version and inclination are also relevant factors. Osteolysis following metal-on-UHMW polyethylene Total Hip Arthroplasty (THA) is well reported. Earlier generation ceramic-on-ceramic bearings did produce some osteolysis, but in flawed implants. As third and now fourth generation ceramic THAs come into mid- and long-term service, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. The technique used by radiologists for identifying the nature of lesions on Computed Tomography (CT) scan is the Hounsfield score which will identify the density of the tissue within the lucent area. Commonly the radiologist will have no access to previous imaging, especially pre-operative imaging if a long time has elapsed. With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA, which states there is osteolysis? This retrospective review aims to determine the accuracy of CT in identifying true osteolysis in a cohort of long-term third generation ceramic-on-ceramic uncemented hip arthroplasties in our department. Pelvic CT scans were performed on the first 27 patients from a cohort of 301 patients undergoing 15-year review with third generation alumina-alumina cementless THAs. The average follow-up was 15 years (15–17). The CT scans were reviewed against pre-operative and post-operative radiographs and reviewed by a second musculoskeletal specialist radiologist. Eleven of the CT scans were reported to show acetabular osteolysis, two reported osteolysis or a possible pre-existing cyst and one reported a definitive pre-existing cyst. After review of previous imaging including pre-operative radiographs, eleven of the thirteen patients initially reported to have osteolysis were found to have pre-existing cysts or geodes in the same size and position as the reported osteolysis, and a further patient had spot-welds with stress-shielding. One patient with evidence of true osteolysis awaits aspiration or biopsy to determine if he has evidence of ceramic wear or metallosis. Reports of osteolysis on CT should be interpreted with care in modern ceramic-on-ceramic THA to prevent unnecessary revision. Further imaging and investigations may be necessary to exclude other conditions such as geodes, or stress shielding which are frequently confused with osteolysis on CT scans

INTRODUCTION. The restoration of the anatomical hip rotation center (HRC) has a major influence on the longevity of hip prostheses. Deviations from the HRC of the anatomical joint after total hip arthroplasty (THA) can lead to increased hip joint forces, early wear or loosening of the implant. The contact conditions of acetabular press-fit cups after implantation, including the degree of press-fit, the existence of a polar gap and cup orientation, may affect the HRC restoration, and therefore implant stability. The aim of this study was to determine the influence of acetabular press-fit, polar gap and cup orientation on HRC restoration during THA. METHODS. THAs were performed by an experienced orthopaedic surgeon in full cadaveric models simulating real patient surgery (n=7). Acetabular cups with a Porocoat™ (n=3) and Gription™ surface coating (n=4) were implanted (DePuy Synthes, Leeds, UK). Computed tomography (CT) scans prior to surgery, as well as after reaming and implantation of press-fit cups were used to calculate the HRC displacement. After aligning the pelves in the anterior pelvic plane, 3D reconstruction of the HRC at each stage was performed by fitting spheres to the femoral head, the reamed cavity and the inserted cup. 3D surface models of the cups were generated using a laser scanner and were registered to the CT images. The effective press-fit was calculated using the diameters of spheres, fitted to the cavity prior to cup insertion and to the outer cup coating. The polar gap was defined as the difference between the outer cup surface and the subchondral bone at the cup pole. Anteversion and abduction angles were calculated as difference between the cup planes and the sagittal and transverse plane, respectively. RESULTS. A medial (6.4±1.6mm), superior (5.1±1.5mm) and posterior (3.0±1.4mm) displacement of the HRC after reaming was measured. A significant inferior shift of the HRC could be measured after cup implantation (p=0.043). No significant influence of the coating design on the HRC shift could be observed. The shift of the HRC back towards the anatomical HRC was highly correlated to the degree of polar gap (R. 2. =0.928, p<0.001) and a trend towards an association with effective press-fit was observed (R. 2. =0.536, p=0.061). The cup angles had no influence on the shift of the HRC, but a high variability in cup anteversion (20.7° to 61.8°) was observed. DISCUSSION. The study suggests that increasing the press-fit and polar gap improves the restoration of the anatomical HRC. Since increasing the degree of press-fit could also lead to higher stresses and an increased fracture risk, future work will study how the acetabular contact conditions influence both primary implant stability and fracture risk, in order to establish an optimal HRC reconstruction to maximize implant longevity

Background. Use of a baseplate with a smaller diameter in reverse shoulder arthroplasty has been recommended, especially in patients with a small glenoid or insufficient bony stock due to severe glenoid wear. However, effect of a smaller baseplate on stability of the glenoid component has not been evaluated. The purpose of this study was to determine whether a smaller baseplate (25 mm) is beneficial to the initial primary stability of the glenoid component compared to that with a baseplate of a commonly used size (29 mm) by finite element analysis. Methods. Computed tomography (CT) scans of fourteen scapulae were acquired from cadavers with no apparent deformity or degenerative change. Glenoid diameter corresponding to the diameter of the inferior circle of glenoid was measured using a caliper and classified into the small and large glenoid groups based on 25mm diameter. CT slices were used to construct 3-dimensional models with Mimics (Materialise, Leuven, Belgium). A corresponding 3D Tornier Aequalis® Reversed Shoulder prosthesis model was generated by laser scanning (Rexcan 3D Laser Scanner, Solutionix, Seoul, Korea). Glenoid components with 25mm and 28mm diameter of the baseplate were implanted into the scapular of small and large glenoid group, respectively. Finite element models were constructed using Hypermesh 11.0 (Altair Engineering, Troy, MI, USA) and a reverse engineering program (Rapidform 3D Systems, Inc., Rock Hill, SC, USA). Abaqus 6.10 (Dassault Systemes, Waltham, MA) was used to simulate 30. o. , 60. o. , and 90. o. glenohumeral abduction in the scapular plane. Single axial loads of 686N (1 BW) at angles of 30. o. , 60. o. , and 90. o. abduction were applied to the center of the glenosphere parallel to the long axis of the humeral stem. Relative micromotion at the middle and inferior thirds bone–glenoid component interface, and distribution of bone stress under the glenoid component and around the screws were analyzed. Wilcoxon's rank-sum test was used for statistical comparison and p < 0.05 was considered as a minimum level of statistical significance. Results. In small glenoid group, micromotion at the middle and inferior thirds of the glenoid-glenosphere interface at angles of 30. o. and 60. o. abduction were significantly greater in the 29mm baseplate than in the 25mm baseplate. There was no significant difference in micromotion at angle of 90. o. abduction between 25mm and 29mm baseplate. In large glenoid group, there was no statistically significant difference in micromotion between 25mm and 29mm baseplate at all angles of abduction. In small glenoid group, maximum bone stress was measured at the point of cortical engagement of the inferior screw and was statistically greater in the 29mm baseplate than in the 25mm baseplate. In large glenoid group, there was no statistically significant difference of maximum bone stress around the inferior screw between 25mm and 29mm baseplates. Conclusions. Use of a baseplate with a smaller diameter (25 mm) in reverse shoulder arthroplasty is suitable for improving the primary stability of the glenoid component, especially in small glenoid