Pelvic tilt (PT) is always described as the pelvic orientation along the transverse axis, yet four PT definitions were established based on different radiographic landmarks: anterior pelvic plane (PT. a. ), the centres of femoral heads and sacral plate (PT. m. ), pelvic outlet (PT. h. ), and sacral slope (SS). These landmarks quantify a similar concept, yet understanding of their relationships is lacking. Some studies referred to the words “pelvic tilt” for horizontal comparisons, but their PT definitions might differ. There is a demand for understanding their correlations and differences for education and research purposes. This study recruited 105 sagittal pelvic radiographs (68 males and 37 females) from a single clinic awaiting their hip surgeries. Hip hardware and spine pathologies were examined for sub-group analysis. Two observers annotated four PTs in a gender-dependent manner and repeated it after six months. The linear regression model and intraclass correlation coefficient (ICC) were applied with a 95% significance interval. The SS showed significant gender differences and the lowest correlations to the other parameters in the male group (-0.3< r <0.2). The correlations of SS in scoliosis (n = 7) and hip implant (female, n = 18) groups were statistically different, yet the sample sizes were too small. PT. m. demonstrated very strong correlation to PT. h. (r > 0.9) under the linear model PT. m. = 0.951 × PT. h. - 68.284. The PT. m. and PT. h. are interchangeable under a simple linear regression model, which enables study comparisons between them. In the male group, SS is more of a personalised spinal landmark independent of the pelvic anatomy. Female patients with hip implant may have more static spinopelvic relationships following a certain pattern, yet a deeper study using a larger dataset is required. The understanding of different PTs improves anatomical education

Abstract. Extended Trochanteric Osteotomy (ETO) improves surgical exposure and aids femoral stem and bone cement removal in Revision Total Hip Replacement (RTHR) surgery. The aim of this study was to identify healing rates and complications of ETO in RTHR. Methods. From 2012 to 2019 we identified patients who underwent ETO for RTHR. Data collected demographics, BMI, diabetes, anticoagulants, indication for ETO, surgical approach, length of ETO and complications. Descriptive analysis of patient demographics, multiple linear regression analysis was performed to assess ETO complications. Results. There were 63 patients with an average age of 69 years. Indications for ETO were aseptic loosening (30), infection (15), periprosthetic fracture (9), recurrent dislocation (5), broken implant (4). There were 44 cemented and 19 uncemented femoral stem that underwent ETO. Average time from index surgery was 12 years (less than a year to 38 years). All procedures were through posterolateral approach and all ETO were stabilised with cables. Average length of ETO was 12.5cm. BMI varied from 18 to 37. There were 5 diabetics and 16 on anticoagulants. All but one ETO went on to unite. Other complications included infection, dislocations, lateral thigh pain and significant limp. Discussion. Fixation of ETO can be with either wires or cables or plate with cables/screws. Advantages of cables are no irritation over greater trochanter, no disruption of gluteus medius/vastus lateralis continuity, reproducible tension in cables and use of torque limiter minimises loss of tension in cables

Intraoperative range of motion (ROM) radiographs are routinely taken during scaphoidectomy and four corner fusion surgery (S4CF) at our institution. It is not known if intraoperative ROM predicts postoperative ROM. We hypothesize that patients with a greater intra-operativeROM would have an improved postoperative ROM at one year, but that this arc would be less than that achieved intra- operatively. We retrospectively reviewed 56 patients that had undergone S4CF at our institution in the past 10 years. Patients less than 18, those who underwent the procedure for reasons other than arthritis, those less than one year from surgery, and those that had since undergone wrist arthrodesis were excluded. Intraoperative ROM was measured from fluoroscopic images taken in flexion and extension at the time of surgery. Patients that met criteria were then invited to take part in a virtual assessment and their ROM was measured using a goniometer. T-tests were used to measure differences between intraoperative and postoperative ROM, Pearson Correlation was used to measure associations, and linear regression was conducted to assess whether intraoperative ROM predicts postoperative ROM. Nineteen patients, two of whom had bilateral surgery, agreed to participate. Mean age was 54 and 14 were male and 5 were male. In the majority, surgical indication was scapholunate advanced collapse; however, two of the participants had scaphoid nonunion advanced collapse. No difference was observed between intraoperative and postoperative flexion. On average there was an increase of seven degrees of extension and 12° arc of motion postoperatively with p values reaching significance Correlation between intr-operative and postoperative ROM did not reach statistical significance for flexion, extension, or arc of motion. There were no statistically significant correlations between intraoperative and postoperative ROM. Intraoperative ROM radiographs are not useful at predicting postoperative ROM. Postoperative extension and arc of motion did increase from that measured intraoperatively

Aim. People awaiting surgery for bone and joint infection may be recommended to stop smoking to improve anaesthetic and surgical outcomes. However, restricting curative surgical treatment to non-smokers on the basis of potentially worse surgical outcomes is not validated for functional outcomes or quality of life differences between patients who do and do not smoke. This study used secondary analysis of trial data to ask: do peri-operative non-smokers have a greater improvement in their quality of life 12 months after surgery for bone and joint infection, compared with non-smokers?. Method. Participants in the SOLARIO and OVIVA clinical trials who had complete baseline and 12 month EQ-5D-5L or EQ-5D-3L scores were included. Smoking status was ascertained at baseline study enrolment from participant self-report. Normalised quality of life scores were calculated for participants at baseline and 12 months, based on contemporaneous health state scores for England. Baseline and 12 month scores were compared to calculate a post-operative increment in quality of life. Results. Mean quality of life increment over 12 months was +0.17 for people who reported smoking peri-operatively (95% confidence interval −0.55 to +0.89), compared to +0.23 for people who did not report smoking peri-operatively (95% confidence interval −0.48 to +0.94). Linear regression analysis found no significant difference between the improvement in quality of life for smokers and non-smokers (p>0.1). Mean increments for both groups were greater than estimates of Minimal Clinically Important Difference in quality of life in musculoskeletal conditions. [1,2]. Conclusions. People who smoke peri-operatively still experience an improvement in quality of life after surgery for orthopaedic infections, commensurate with the improvement experienced by non-smokers. Surgery should not be denied to people on the basis of reported smoking status alone

The emergence of patient specific instrumentation has seen an expansion from simple radiographs to plan total knee arthroplasty (TKA) with modern systems using computed tomography (CT) or magnetic resonance imaging scans. Concerns have emerged regarding accuracy of these non-weight bearing modalities to assess true mechanical axis. The aim of our study was to compare coronal alignment on full length standing AP imaging generated by the EOS acquisition system with the CT coronal scout image. Eligible patients underwent unilateral or bilateral primary TKA for osteoarthritis under the care of investigating surgeon between 2017 and 2022, with both EOS X-Ray Imaging Acquisition System and CT scans performed preoperatively. Coronal mechanical alignment was measured on the supine coronal scout CT scan and the standing HKA EOS. Pre-operative lower limb coronal alignment was assessed on 96 knees prior to TKA on the supine coronal scout CT scan and the standing HKA EOS. There were 56 males (56%), and 44 right knees (44%). The mean age was 68 years (range 53-90). The mean coronal alignment was 4.7 degrees (SD 5.3) on CT scan and 4.6 degrees (SD 6.2) on EOS (p=0.70). There was a strong positive correlation of coronal alignment on CT scan and EOS (pearson. 0.927, p=0.001). The mean difference between EOS and CT scan was 0.9 degrees (SD 2.4). Less than 3 degrees variation between measures was observed in 87% of knees. On linear regression for every 1° varus increase in CT HKA alignment, the EOS HKA alignment increased by 0.93° in varus orientation. The model explained 86% of the variability. CT demonstrates excellent reliability for assessing coronal lower limb alignment compared to EOS in osteoarthritic knees. This supports the routine use of CT to plan TKA without further weight bearing imaging in routine cases

The optimal timing of when to perform manipulation under anesthesia (MUA) for stiffness following total knee arthroplasty (TKA) is unclear. This study aimed to identify the risk factors for MUA following primary TKA and whether performing an “early” MUA within 3 months results in a greater improvement in range of motion. Primary TKAs performed between January 2013 and December 2018 at three tertiary New Zealand hospitals were reviewed. International Classification of Diseases discharge coding was used to identify patients who underwent an MUA. Multivariate Cox regression was performed to identify patient and surgical risk factors for MUA. Pre- and post-MUA knee flexion angles were identified through manual review of operation notes. Multivariate linear regression was performed to compare the mean flexion angles pre- and post-MUA, as well as the mean gain in flexion, between patients undergoing “early” (<3 months) versus “late” MUA (>3 months). 7386 primary TKAs were analyzed in which 131 underwent subsequent MUA (1.8%). Patients aged <65 years were two times more likely to undergo MUA compared to patients aged ≥65 years (2.5% versus 1.3%, adjusted hazard ratio = 2.1, p<0.001). Gender, body mass index, patient comorbidities or a history of cancer were not associated with the risk of MUA. There was no difference in the final post-MUA flexion angle between patients who underwent early versus late MUA (104.7 versus 104.1 degrees, p = 0.819). However, patients who underwent early MUA had poorer pre-MUA flexion (72.3 versus 79.6 degrees, p = 0.012), and subsequently had a greater overall gain in flexion compared to patients who underwent late MUA (mean gain 33.1 versus 24.3 degrees, p<0.001). Younger age was the only patient risk factor for MUA. A greater overall gain in flexion was achieved in patients who underwent early MUA within 3 months

Preoperative ligament laxity can be characterized intraoperatively using digital robotic tensioners. Understanding how preoperative knee joint laxity affects preoperative and early post-operative patient reported outcomes (PROMs) may aid surgeons in tailoring intra-operative balance and laxity to optimize outcomes for specific patients. This study aims to determine if preoperative ligament laxity is associated with PROMs, and if laxity thresholds impact PROMs during early post-operative recovery. 106 patients were retrospectively reviewed. BMI was 31±7kg/m. 2. Mean age was 67±8 years. 69% were female. Medial and lateral knee joint laxity was measured intraoperatively using a digital robotic ligament tensioning device after a preliminary tibial resection. Linear regressions between laxity and KOOS12-function were performed in extension (10°), midflexion (45°), and flexion (90°) at preoperative, 6-week, and 3-month time points. Patients were separated into two laxity groups: ≥7 mm laxity and <7 mm laxity. Student's t-tests determined significant differences between laxity groups for KOOS12-function scores at all time points. Correlations were found between preoperative KOOS12-function and medial laxity in midflexion (p<0.001) and flexion (p<0.01). Patients with <7 mm of medial laxity had greater preoperative KOOS12-function scores compared to patients with ≥7 mm of medial laxity in extension (46.8±18.2 vs. 29.5±15.6, p<0.05), midflexion (48.4±17.8 vs. 32±16.1, p<0.001), and flexion (47.7±18.3 vs. 32.6±14.7, p<0.01). No differences in KOOS12-function scores were observed between medial laxity groups at 6-weeks or 3-months. All knees had <5 mm of medial laxity postoperatively. No correlations were found between lateral laxity and KOOS12-function. Patients with preoperative medial laxity ≥7 mm had lower preoperative PROMs scores compared to patients with <7 mm of medial laxity. No differences in PROMs were observed between laxity groups at 6 weeks or 3 months. Patients with excessive preoperative joint laxity achieve similar PROMs scores to those without excessive laxity after undergoing gap balancing TKA

Introduction. The functional ante-inclination (AI) of the cup after total hip arthroplasty (THA) is a key component in the combined sagittal index (CSI) to predict joint stability after THA. To accurately predict AI, we deducted a mathematic algorithm between the radiographic anteversion (RA), radiographic inclincation (RI), pelvic tilting (PT), and AI. The current study aims (1) to validate the mathematic algorithm; (2) to convert the AI limits in the CSI index (standing AI ≤ 45°, sitting AI ≥ 41°) into coronal functional safe zone (CFSZ) and explore the influences of the stand-to-sit pelvic motion (PM) and pelvic incidence (PI) on CFSZ; (3) to locate a universal cup orientation that always fulfill the AI criteria of CSI safe zone for all patients or subgroups of PM(PM ≤ 10°, 10° < PM ≤ 30°, and PM > 30°) and PI (PI≤ 41°, 41°< PI ≤ 62°, and PI >62°), respectively. Methods. A 3D printed phantom pelvic model was designed to simulate changing PT values. An acetabular cup was implanted with different RA, RI, and PT settings using robot assisted technique. We enrolled 100 consecutive patients who underwent robot assisted THA from April, 2019 to June, 2019 in our hospital. EOS images before THA and at 6-month follow-up were collected. AI angles were measured on the lateral view radiographs as the reference method. Mean absolute error (MAE), Bland-Altman analysis and linear regression were conducted to assess the accuracy of the AI algorithm for both the phantom and patient radiographic studies. The 100 patients were classified into three subgroups by PM and PI, respectively. Linear regression and ANOVA analysis were conducted to explore the relationship between the size of CFSZ, and PM and PI, respectively. Intersection of the CFSZ was conducted to identify if any universal cup orientation (RA, RI) existed for the CSI index. Results. The mathematic algorithm for calculating AI based on RI, RA, and PT is highly accurate according to the phantom and patient radiographic study. CFSZ size corresponds linearly with PM (R² = 0.638) and PI (R² = 0.129), respectively. There are significant differences in the size of CFSZ, as well as in the intersection of CFSZ and LSZ, between the subgroups of PM and PI, respectively (P<0.017). There is no universal cup orientations could be identified to fulfill the AI limits of the CSI index for all the 100 patients or any of the three subgroups, according to either PM or PI. Conclusions. The cup target orientation should be individualized. The validated algorithm between AI and RA, RI, and PT parameters can serve as the quantitative tool for patient-specific optimization of functional cup AI in different postures

Thrombelastography (TEG) is a point-of-care tool that can measure clot formation and breakdown using a whole blood sample. We have previously used serial TEG analysis to define hypercoagulability and increased venous thromboembolism (VTE) risk following a major fracture requiring surgical treatment. Additionally, we have used serial TEG analysis to quantify the prolonged hypercoagulable state and increased VTE risk that ensues following a hip fracture. Recently developed cartridge-based platelet mapping (PLM) using TEG analysis can be used to activate platelets at either the adenosine diphosphate (ADP) receptor or at the Thromboxane A2 (AA) receptor, in order to evaluate clot strength when platelets are activated only through those specific receptors. This study aim was to evaluate platelet contribution to hypercoagulability, in order to identify potential therapeutic targets for VTE prevention. We hypothesized that there would be a platelet-predominant contribution to hypercoagulability following a hip fracture. Patients aged 50 years or older with a hip fracture treated surgically were enrolled in this prospective cohort study. Exclusion criteria were: prior history of VTE, active malignancy, or pre-injury therapeutic dose anticoagulation. Serial TEG and PLM analyses were performed at admission, post-operative day (POD) 1, 3, 5, 7 and at 2-, 4-, 6- and 12-weeks post-operatively. All patients received thromboprophylaxis with low molecular weight heparin (LMWH) for 28 days post-operatively. Hypercoagulability was defined as maximal amplitude (MA; a measure of clot strength) over 65mm based on TEG analysis. Independent samples t-tests were used to compare MA values with this previously established threshold and a mixed effects linear regression model was used to compare MA values over time. Independent samples t-tests and Chi-sqaured analyses were used to compare between the surgical fixation and arthroplasty groups. Forty-six patients with an acute hip fracture were included, with a mean age of 77.1 (SD = 10.6) years, with 61% (N=11) being female. Twenty-six were treated with arthroplasty (56.5%), while the remainder underwent surgical fixation of their hip fractures. TEG analysis demonstrated post-operative hypercoagulability (mean MA over 65mm) at all follow-up timepoints until 12-weeks. PLM identified a platelet-mediated hypercoagulable state based on elevated ADP-MA and AA-MA, with more pronounced platelet contribution demonstrated by the AA pathway. Patients treated with arthroplasty had significantly increased AA-MA compared with ADP-MA at POD 3 and at the 12-week follow-up. Thrombelastography can be used to identify hypercoagulability and increased risk for VTE following a hip fracture. Platelet mapping analysis from this pilot study suggests a platelet-mediated hypercoagulable state that may benefit from thromboprophylaxis using an anti-platelet agent that specifically targets the AA platelet activation pathway, such as acetylsalicylic acid (ASA). This research also supports differences in hypercoagulability between patients treated with arthroplasty compared to those who undergo fracture fixation

Multiligament knee injuries (MLKI) are rare and life-altering injuries that remain difficult to treat clinically due to a paucity of evidence guiding surgical management and timing. The purpose of this study was to compare injury specific functional outcomes following early versus delayed surgical reconstruction in MLKI patients to help inform timing decisions in clinical practice. A retrospective analysis of prospectively collected data from patients with MLKIs at a single academic level 1-trauma center was conducted. Patients were eligible for inclusion if they had an MLKI, underwent reconstructive surgery either prior to 6wks from injury or between 12weeks and 2 years from injury, and had at least 12months of post-surgical follow-up. Patients with a vascular injury, open injuries or associated fractures were excluded. Study participants were stratified into early (<6wks from injury) and delayed surgical intervention (>12 weeks – 2 years from injury). The primary outcome was patient reported, injury specific, quality of life in the form of the Multiligament Quality of Life questionnaire (MLQOL) and its four domains (Physical Impairment, Emotional Impairment, Activity Limitations and Societal Involvement). We secondarily analyzed differences in the need for manipulation under anesthesia, and reoperation rates, as well as radiographic Kellgren Lawrence (KL) arthritis grades, knee laxity grading and range of motion at the most recent follow-up. A total of 131 patients met our inclusion criteria, all having had surgery between 2006 and 2019. There were 75 patients in the early group and 56 in the delayed group. The mean time to surgery was 17.6 ± 8.0 days in the early group versus 279 ± 146.5 days in the delayed. Mean postoperative follow-up was 58 months. There were no significant differences between early and delayed groups with respect to age (34 vs. 32.8 years), sex (77% vs 63% male), BMI (28.3 vs 29.7 kg/m. 2. ), or injury mechanism (p>0.05). The early surgery group was found to include more patients with lateral sided injuries (n=49 [65%] vs. n=23 [41%]; p=0.012), a higher severity of Schenck Classification (p=0.024) as well as nerve injuries at initial presentation (n=35 [49%] vs n=8 [18%]; p<0.001). Multivariable linear regression analyses of the four domains of the MLQOL did not demonstrate an independent association with early versus delayed surgery status (p>0.05), when controlling for age, sex, Schenck classification, medial versus lateral injury, and nerve injury status. In terms of our secondary outcomes, we found that the early group underwent significantly more manipulations under anesthesia compare with the delayed group (n=24, [32%] vs n=8 [14%], p=0.024). We did not identify a significant difference in physical examination laxity grades, range of motion, KL grade or reoperation rates between groups (p>0.05). We found no difference in patient reported outcomes between those who underwent early versus delayed surgery following MLKI reconstruction. In our secondary outcomes, we found significantly more patients in the early surgery group required a manipulation under anesthesia following surgery, which may indicate a propensity for arthrofibrosis after early MLKI reconstruction

Introduction. Innovations in orthopaedic technology and infrastructure growth often require significant funding. Although an increasing trend has been observed for third-party investments into medical startups and physician practices, no study has examined the role of this funding in orthopaedics, including the influence of venture capital (VC). Therefore, this study analyzed trends in VC investments related to the field of orthopaedic surgery, as well as the characteristics of companies receiving said investments. Methods. Venture capital investments into orthopaedic-related businesses were reviewed from 2000–2019 using Capital IQ, a proprietary market intelligence platform documenting financial transactions. The dataset was initially filtered to include healthcare-related venture capital transactions pertaining to the field of orthopaedic surgery. The final list of VC investments and their corresponding businesses were categorized by transaction year, amount (in USD), and orthopaedic subspecialty. The number and sum of VC investments was calculated both annually and cumulatively across the entire study period. Linear regression was used for trend analysis within two distinct, decade-long timeframes (2000–2009 and 2010–2019) and one-way analysis of variance was used to assess differences across orthopaedic subspecialties. Results. Over the course of two decades, 672 VC investments were made into orthopaedic-related businesses, representing a total of $3.5 billion. Both the number and dollar value of transactions were greater in the second decade (2010–19) (233, $1.9 billion), compared to the first decade (439, $1.6 billion). Linear regression revealed significant trends in both the quantity and dollar amount of VC transactions within the decade from 2000–09 (p = 0.0002 and p = 0.0143, respectively) but no such trend in the latter decade (Figure 1A-B, Figure 2A-B). Throughout both decades studied, the largest and most frequent VC investments took place within Spine and Adult Reconstruction (Figure 3). One-way analysis of variance revealed significant differences in the annual frequency and amount of investment across orthopaedic subspecialties (p < 0.001 and p < 0.001, respectively). Discussion and Conclusion. The present data suggest that an initially rising trend in VC investment in orthopaedic-related businesses may have plateaued over the past decade. These findings may have important implications for continued investment into orthopaedic innovations and collaboration between the surgical community and private sector, as well as the perceived profitability of orthopaedic industries by third-party interests. For any figures or tables, please contact the authors directly

Introduction. Density-modulus relationships are often used to map the mechanical properties of bone based on CT- intensity in finite element models (FEMs). Although these relationships are thought to be site-specific, relationships developed for alternative anatomic locations are often used regardless of bone being modeled. Six relationships are commonly used in finite element studies of the shoulder; however, the accuracy of these relationships have yet to be compared. This study compares each of these six relationships ability to predict apparent strain energy density (SED. app. ) in trabecular bone cores from the glenoid. Methods. Quantitative-CT (QCT) (0.625 mm isotropic voxels), and µ-CT scans (0.032 mm isotropic voxels) were obtained for fourteen cadaveric scapulae (7 male, 7 female). Micro finite element models (µ-FEMs) were created from 98 virtual ‘cores’ using direct conversion to hexahedral elements. Two µ-FEM cases were considered: homogeneous tissue modulus of 20 GPa, and heterogeneous tissue modulus scaled by CT intensity of the µ-CT images (196 models). Each µ- FEM model was compressively loaded to 0.5% apparent strain and apparent strain energy density (SED. app. ) was calculated. Additionally, each of the six density-modulus relationships were used to map heterogeneous material properties to co- registered QCT-derived models (588 models in total). The loading and boundary conditions were replicated in the QCT-FEMs and the SED. app. was calculated and compared to the µ-FEM SED. app. To account for more samples than donors, restricted maximum likelihood estimation (REML) linear regression compared µ-FEM SED. app. and QCT-FEM SED. app. for each relationship. Results. When considering comparisons between QCT-FEMs and µ-FEMs with a homogeneous tissue modulus, near absolute statistical agreement (Y=X) was observed between the µ-FEMs and the QCT-FEMs using the Morgan et al. (2003) pooled relationship. Not surprisingly, due to the similarity between the two relationships, the Gupta & Dan (2004) and Carter and Hayes (1977) models showed near identical REML linear regression fit parameters. All relationships other than the Morgan et al. (2003) pooled relationship, greatly underestimated the µ-FEM apparent strain energy density (SED. app. ) when considering a homogeneous tissue modulus in the µ-FEMs. The same result with the pooled relationship did not hold true when heterogeneous tissue modulus was considered in the µ-FEMs. The Büchler et al., (2002) relationship most accurately predicted the SED. app. for this comparison. Interestingly, the Gupta & Dan (2004) and Carter and Hayes (1977) relationships again showed near identical REML linear regression fit parameters. DISCUSSION. This study compared six common density-modulus relationships used to map mechanical properties of bone in shoulder FE studies. It was found that when considering a homogeneous tissue modulus for µ-FEMs, relationships pooled from alternative anatomic locations may accurately predict the mechanical properties of glenoid trabecular bone. However, when considering a heterogeneous tissue modulus, this did not hold true. Further studies to determine if these relationships can be translated to whole bones may provide insight into the predictive capabilities of using pooled density-modulus equations in the mapping of mechanical properties in future FEMs of the shoulder

Introduction. Machine learning is a relatively novel method to orthopaedics which can be used to evaluate complex associations and patterns in outcomes and healthcare data. The purpose of this study is to utilize 3 different supervised machine learning algorithms to evaluate outcomes from a multi-center international database of a single shoulder prosthesis to evaluate the accuracy of each model to predict post-operative outcomes of both aTSA and rTSA. Methods. Data from a multi-center international database consisting of 6485 patients who received primary total shoulder arthroplasty using a single shoulder prosthesis (Equinoxe, Exactech, Inc) were analyzed from 19,796 patient visits in this study. Specifically, demographic, comorbidity, implant type and implant size, surgical technique, pre-operative PROMs and ROM measures, post-operative PROMs and ROM measures, pre-operative and post-operative radiographic data, and also adverse event and complication data were obtained for 2367 primary aTSA patients from 8042 visits at an average follow-up of 22 months and 4118 primary rTSA from 11,754 visits at an average follow-up of 16 months were analyzed to create a predictive model using 3 different supervised machine learning techniques: 1) linear regression, 2) random forest, and 3) XGBoost. Each of these 3 different machine learning techniques evaluated the pre-operative parameters and created a predictive model which targeted the post-operative composite score, which was a 100 point score consisting of 50% post-operative composite outcome score (calculated from 33.3% ASES + 33.3% UCLA + 33.3% Constant) and 50% post-operative composite ROM score (calculated from S curves weighted by 70% active forward flexion + 15% internal rotation score + 15% active external rotation). 3 additional predictive models were created to control for the time required for patient improvement after surgery, to do this, each primary aTSA and primary rTSA cohort was subdivided to only include patient data follow-up visits >20 months after surgery, this yielded 1317 primary aTSA patients from 2962 visits at an average follow-up of 50 months and 1593 primary rTSA from 3144 visits at an average follow-up of 42 months. Each of these 6 predictive models were trained using a random selection of 80% of each cohort, then each model predicted the outcomes of the remaining 20% of the data based upon the demographic, comorbidity, implant type and implant size, surgical technique, pre-operative PROMs and ROM measures inputs of each 20% cohort. The error of all 6 predictive models was calculated from the root mean square error (RMSE) between the actual and predicted post-op composite score. The accuracy of each model was determined by subtracting the percent difference of each RMSE value from the average composite score associated with each cohort. Results. For all patient visits, the XGBoost decision tree algorithm was the most accurate model for both aTSA & rTSA patients, with an accuracy of ∼89.5% for both aTSA and rTSA. However for patients with 20+ month visits only, the random forest decision tree algorithm was the most accurate model for both aTSA & rTSA patients, with an accuracy of ∼89.5% for both aTSA and rTSA. The linear regression model was the least accurate predictive model for each of the cohorts analyzed. However, it should be noted that all 3 machine learning models provided accuracy of ∼85% or better and a RMSE <12. (Table 1) Figures 1 and 2 depict the typical spread and RMSE of the actual vs. predicted total composite score associated with the 3 models for aTSA (Figure 1) and rTSA (Figure 2). Discussion. The results of this study demonstrate that multiple different machine learning algorithms can be utilized to create models that predict outcomes with higher accuracy for both aTSA and rTSA, for numerous timepoints after surgery. Future research should test this model on different datasets and using different machine learning methods in order to reduce over- and under-fitting model errors. For any figures or tables, please contact the authors directly

Introduction. Sagittal pelvic tilt (SPT) can change with spinal pathologies and fusion. Change in the SPT can result in impingement and hip instability. Our aim was to determine the magnitude of the SPT change for hip instability to test the hypothesis that the magnitude of SPT change for hip instability is less than 10° and it is not similar for different hip motions. Methods. Hip implant motions were simulated in standing, sitting, sit-to-stand, bending forward, squatting and pivoting in Matlab software. When prosthetic head and liner are parallel, femoral head dome (FHD) faces the center of the liner. FHD moves toward the edge of the liner with hip motions. The maximum distance between the FHD and the center in each motion was calculated and analyzed. To make the results more reliable and to consider the possibility of bony impingement, when the FHD approached 90% of the distance between the liner-center and liner-edge, we considered the hip “in danger for dislocation”. The implant orientations and SPT were modified by 1-degree increments and we used linear regression with receiver operating characteristic (ROC) curve and area under the curve (AUC) to determine the magnitude of SPT change that could cause instability. Results. SPT modification as low as 7° could result in dislocation during pivoting (AUC: 87.5; sensitivity: 87.9; specificity 79.8; p=0.0001). This was as low as 10° for squatting (AUC: 91.5; sensitivity: 100; specificity 75.9; p=0.0001) and as low as 13° for sit-to-stand (AUC: 94.6; sensitivity: 98; specificity 83; p=0.0001). SPT modification affects hip stability more in pivoting than sit-to-stand and squatting. Discussion. Our results show the importance of close collaboration between the hip and spine surgeons in treating patients who undergo THA and spinal fusion. The postoperative SPT modification should be considered for preoperative computer simulation for determining the implant safe zone

Purpose. Various alignment philosophies for total knee arthroplasty (TKA) have been described, all striving to achieve excellent long-term implant survival and good functional outcomes. In recent years, in search of higher functionality and patient satisfaction, a shift towards more patient-specific alignment is seen. Robotics is the perfect technology to tailor alignment. The purpose of this study was to describe ‘inverse kinematic alignment’ (iKA) technique, and to compare clinical outcomes of patients that underwent robotic-assisted TKA performed by iKA versus adjusted mechanical alignment (aMA). Methods. The authors analysed the records of a consecutive series of patients that received robotic assisted TKA with iKA (n=40) and with aMA (n=40). Oxford Knee Score (OKS) and satisfaction on a visual analogue scale (VAS) were collected at a follow-up of 12 months. Clinical outcomes were assessed according to patient acceptable symptom state (PASS) thresholds, and uni- and multivariable linear regression analyses were performed to determine associations of OKS and satisfaction with 6 variables (age, sex, body mass index (BMI), preoperative hip knee ankle (HKA) angle, preoperative OKS, alignment technique). Results. The iKA and aMA techniques yielded comparable outcome scores (p=0.069), with OKS respectively 44.6±3.5 and 42.2±6.3. VAS Satisfaction was better (p=0.012) with iKA (9.2±0.8) compared to aMA (8.5±1.3). The number of patients that achieved OKS and satisfaction PASS thresholds was significantly higher (p=0.049 and p=0.003, respectively) using iKA (98% and 80%) compared to aMA (85% and 48%). Knees with preoperative varus deformity, achieved significantly (p=0.025) better OKS using iKA (45.4±2.0) compared to aMA (41.4±6.8). Multivariable analyses confirmed better OKS (β=3.1; p=0.007) and satisfaction (β=0.73; p=0.005) with iKA. Conclusions. The results of this study suggest that iKA and aMA grant comparable clinical outcomes at 12-months follow-up, though a greater proportion of knees operated by iKA achieved the PASS thresholds for OKS and satisfaction. Notably. in knees with preoperative varus deformity, iKA yielded significantly better OKS and satisfaction than aMA

Introduction. Robotic-arm assisted knee arthroplasty (rKA) has been associated with improved clinical, radiographic, and patient-reported outcomes. There is a paucity of literature, however, addressing its cost effectiveness. In the context of an integrated health system with an insurance plan and single source comprehensive data warehouse for electronic health records and claims data, we present an evaluation of healthcare costs and utilization associated with manual knee arthroplasty (mKA) versus rKA. We also examine the influence of rKA technology on surgeons’ practice patterns. Methods. Practice patterns of KA were assessed 18 months before and after introduction of robotic technology in April 2018. For patients also insured through the system's health plan, inpatient costs (actual costs recorded by health system), 90-day postoperative costs (allowed amounts paid by insurance plan), and 90-day postoperative utilization (length of stay, home health care visits, rehabilitation visits) were compared between mKA and rKA patients, stratified by total (TKA) or unicompartmental (UKA) surgery. Linear regression modeling was used to compare outcomes between the two pairs of groups (mKA vs. rKA, for both UKA and TKA). Log-link function and gamma error distribution was used for costs. All analyses were done using SAS statistical software, with p<0.05 considered statistically significant. Results. Overall KA volume increased 21%, from 532 cases in the pre-rKA period to 644 post-rKA introduction, with UKA surgeries increasing from 38 to 97 (155%). Of these KAs, 218 patients were insured through our system's health plan (38 rUKAs, 9 mUKAs, 91 rTKAs, and 80 mTKAs), allowing precise insurance claims analysis for postoperative utilization and cost. Patients with rKA had significantly lower mean home health costs (-90% difference for UKA, −79% difference for TKA, p<0.02) and home rehab costs (-64% difference for UKA, −73% difference for TKA, p≤0.007) than mKA patients. No significant differences were observed in outpatient rehab (visits or costs), total rehab costs, or length of stay. Mean total postoperative costs were significantly lower for rUKA than mUKA (-47% difference, p=0.02) but similar for TKA (p>0.05). There were no significant differences in total inpatient costs between MAKO and non-MAKO patients. Conclusion. Robotic-arm assisted KA can allow for increased UKA volume and potential for substantial cost savings over the total episode of care by reducing postoperative utilization and costs

Rapid discharge pathways (RDP) have been implemented throughout most areas of orthopaedics. The primary goal of these pathways is to standardize the post-surgical hospital course for patients in order to decrease hospital length-of-stay (LOS). Surgical treatment of adolescent idiopathic scoliosis (AIS) remains one of the most invasive pediatric orthopaedic procedure and is routinely associated with a prolonged hospital stay. The implementation of RDPs following surgery for AIS has shown to be successful; however, all of these studies have been conducted within the United States and it has been shown previously that there exists major differences in hospital LOS and in post-operative complications between Canada and the United States. Therefore, the objective of this study was to determine if the implementation of a RDP at a single children's tertiary-referral centre in Canada could decrease hospital LOS without increasing post-operative complications. A retrospective chart review was completed for all patients who underwent posterior spinal instrumentation and fusion (PSIF) between March 1st, 2010 and February 28th, 2019, with date of implementation being March 1st, 2015. Patient pre-operative, operative, and post-operative information was collected from the charts along with the primary outcome variables: LOS, wound complication, 30-day return to the OR, 30-day emergency department admission, and 30-day hospital readmission. An interrupted time series analysis with a robust linear regression model was utilized to assess for any differences in outcomes following implementation of the RDP. Ninety days before and after the implementation of the RDP was not included in this analysis due to variances in practice that were occurring at this time. A total of 244 participants were identified, with 113 patients in the conventional pathway and 131 patients in the RDP cohort. No significant differences in pre-operative or operative characteristics existed between the groups, except for the RDP group having approximately a 50 larger pre-operative curve and the conventional pathway having on average 200mL greater intra-operative blood loss (p<0.05). Hospital LOS was found to be significantly shorter in the RDP group, with the median LOS being 5.2 [95% IQR 4.3–6.1] days in the conventional group and 3.4 [95% IQR 3.3–3.5] days in the RDP group (p<0.05). Patients in the RDP group were also found to stand 0.9 days earlier, walk 1.1 days earlier, their Foley catheter was discontinued 0.5 days earlier and their personal controlled analgesia was discontinued 12 hours sooner (p<0.05). There were no differences in post-operative complications between the two groups (p>0.05). This study demonstrates that implementing a RDP following PSIF for AIS can successfully decrease hospital LOS without increasing post-operative complications in a single payer universal healthcare system. The associated decrease in LOS could correlate with decreasing costs for both the healthcare system and for the patient's family

Management of the pathologic long-head biceps tendon remains controversial. Biceps tenotomy is a simple intervention but may result in visible deformity and subjective cramping. Comparatively, biceps tenodesis is technically challenging, and has increased operative times, and a more prolonged recovery. The purpose of this study was to determine the incidence of popeye deformity following biceps tenotomy versus tenodesis, identify predictors for developing a deformity, and compare subjective and objective outcomes between those that have one and those that do not. Data for this study were collected as part of a randomized clinical trial comparing tenodesis versus tenotomy in the treatment of lesions of the long head of biceps tendon. Patients 18 years of age or older with an arthroscopy confirmed biceps lesion were randomized to one of these two techniques. The primary outcome measure for this sub-study was the rate of a popeye deformity at 24-months post-operative as determined by an evaluator blinded to group allocation. Secondary outcomes were patient reported presence/absence of a popeye deformity, satisfaction with the appearance of their arm, as well as pain and cramping on a VAS. Isometric elbow flexion and supination strength were also measured. Interrater reliability (Cohen's kappa) was calculated between patient and evaluator on the presence of a deformity, and logistic regression was used to identify predictors of its occurrence. Linear regression was performed to identify if age, gender, or BMI were predictive of satisfaction in appearance if a deformity was present. Fifty-six participants were randomly assigned to each group of which 42 in the tenodesis group and 45 in the tenotomy group completed a 24-month follow-up. The incidence of popeye deformity was 9.5% (4/42) in the tenodesis group and 33% (15/45) in the tenotomy group (18 male, 1 female) with a relative risk of 3.5 (p=0.016). There was strong interrater agreement between evaluator and patient perceived deformity (kappa=0.636; p<0.001). Gender tended towards being a significant predictor of having a popeye with males having 6.6 greater odds (p=0.090). BMI also tended towards significance with lower BMI predictive of popeye deformity (OR 1.21; p=0.051). Age was not predictive (p=0.191). Mean (SD) satisfaction score regarding the appearance of their popeye deformity was 7.3 (2.6). Age was a significant predictor, with lower age associated with decreased satisfaction (F=14.951, adjusted r2=0.582, p=0.004), but there was no association with gender (p=0.083) or BMI (p=0.949). There were no differences in pain, cramping, or strength between those who had a popeye deformity and those who did not. The risk of developing a popeye deformity was 3.5 times higher after tenotomy compared to tenodesis. Male gender and lower BMI tended towards being predictive of having a deformity; however, those with a high BMI may have had popeye deformities that were not as visually apparent to an examiner as those with a lower BMI. Younger patients were significantly less satisfied with a deformity despite no difference in functional outcomes at 24 months. Thus, biceps tenodesis may be favored in younger patients with low BMI to mitigate the risk of an unsatisfactory popeye deformity

Introduction. Wear of the ultra-high molecular weight polyethylene (UHWMPE) component and the subsequent aseptic loosening remains a primary reason for late revision of total knee replacements (TKRs).[1] While improved measurement techniques have provided more quantitative information on the wear of surgically retrieved inserts, it is not well understood how observed damage patterns translate to volume loss of polyethylene in vivo. The overall purpose of this study is to investigate the relationship of damage patterns and volume loss at the articular surface of total knee replacements. We hypothesize that damage patterns are reliable predictors of volume loss. Methods. Two different investigators independently analyzed damage patterns and volume loss on 43 revision- and 21 postmortem-retrieved MG II (Zimmer Inc.) tibial UHMWPE components. Areas of damage patterns on the articular surfaces were outlined with a video microscope (SmartScope, OGP) and were separated into four spatially exclusive categories (Fig. 1): delamination, pitting, striations and polishing. Articular surfaces were digitized with a low-incidence laser coordinate measuring machine (SmartScope, OGP). Autonomous reconstruction, a previously described and validated method,[2] calculated volume loss on the medial and lateral sides of each component. To investigate the predictability of volume loss using observed patterns, stepwise linear regression models were rendered in PASW Statistics 18 (SPSS Inc). Results. Components with total volume loss higher than 300 mm3 exhibited the jagged and flaky surface topography characteristic of severe delamination. Excluding delaminated components, the population's total wear rate (±95% CI) was 12.9 ± 5.97 mm3/year (Pearson's r = 0.527, p < 0.001), which accounted for volume loss due to creep (Figure 2). The wear rates on the medial side (6.56 ± 3.91 mm3/year, Pearson's r = 0.434, p = 0.002) and on the lateral side (6.32 ± 3.44 mm3/year, Pearson'sr = 0.467, p < 0.001) were not significantly different (p = 0.926). Linear regression models that included delaminated components revealed that delaminated and striated areas were significant predictors of volume (Figure 3 - Table 1). Pitted area was also a significant factor on the total part, but fell out of the medial and lateral models. When delaminated components were excluded, volume loss was similarly explained by striated and pitted areas on the medial side and total part. However, the adjusted R2 of these models was low − 0.177 and 0.166, respectively. Discussion. We found that damage patterns were not reliable surrogates for material volume loss. Other than delamination, area of striated patterns best predicted volume loss. However, the large reduction in adjusted R2 of the linear regression model indicates that delaminated areas were essential to explaining variations in the volume loss. While other groups have reported striations on retrievals [3], this damage pattern remains widely unrecognized in retrieval and knee simulator studies, with the mechanism poorly understood. To view tables/figures, please contact authors directly

Numerous studies have demonstrated that concomitant lower back pain (LBP) results in worse functional outcomes in patients undergoing surgical treatment for the management of end stage hip and knee arthritis. However, no equivalent studies have analysed the impact of back pain on the outcomes of patients with end stage ankle arthritis. Furthermore, given that two widely accepted surgical options exist in the treatment of ankle arthritis, namely total ankle arthroplasty (TAA) and ankle arthrodesis (AA), it is possible that one surgical technique may be superior in patients with LBP. The aim of this study was to determine the incidence of LBP in people with ankle arthritis, analyse its effect on functional outcomes, and explore whether there was a treatment advantage from either TAA or AA. Prospectively collected data from the Canadian Orthopaedic Foot and Ankle Society (COFAS) database of ankle arthritis was analysed in this study. All patients with ankle arthritis who underwent surgery performed by three fellowship-trained foot and ankle surgeons at a single institution between January 2003 and July 2012 were studied. Patient demographics were collected pre-operatively, including the absence or presence of back pain, and post-operative follow up was performed at 2 and 5 years, evaluating patient-reported functional outcome measures including the Ankle Arthritis Score (AAS) and the 36-item short form survey (SF-36). Using a linear regression model, a multivariate analysis was performed to examine the relationship between back pain, TAAs and AAs. In total, 451 patients were studied. 164 patients (36.4%) presented with concomitant LBP. At presentation, the LBP group had worse AAS scores (54.8 vs 57.8 p. At 2 years postoperatively, the AAS score was the same in both groups (28.9 vs 26.8 p = 0.3), but patients with LBP had worse SF-36 PCS (42.1 vs 36.6 p 0.05) in any of the functional outcome scores at 2 or 5 years post-operatively. The results of this study suggest there is no advantage of TAA over AA in the treatment of ankle arthritis in patients with concomitant lower back pain. Although pre-operative back pain resulted in worse SF-36 outcomes at 2 and 5 years post- operatively, this was not the case for AAS scores