Introduction

Outpatient total joint arthroplasty (TJA) is emerging as a viable alternative to the historically accepted hospital based inpatient TJA in the United States. Several studies have focused on the financial advantages of outpatient TJA, however little research has discussed patient reported outcome measures (PROM) and the overall patient experience. This is a retrospective comparison of PROM data in patients undergoing outpatient vs. inpatient total hip arthroplasty (THA).

Introduction

Outpatient total joint arthroplasty (TJA) is emerging as a viable alternative to the historically accepted hospital-based inpatient TJA in the United States. Several studies have focused on the financial advantages of outpatient TJA, however little research has discussed patient reported outcome measures (PROM) and the overall patient experience. The purpose of this study is to compare PROM data in patients undergoing outpatient vs. inpatient total knee arthroplasty (TKA) performed in the first year of a newly opened outpatient facility.

It is unclear whether combat casualties with complex hindfeet fractures would have an improved outcome with reconstruction or amputation. This study aimed to determine the outcomes of British military casualties sustaining calcaneal fractures. In the 12 years of conflict in Iraq and Afghanistan there were 116 calcaneal fractures in 98 patients. Seventy-four patients (74/98 76%) were contactable, providing follow up data for 85 fractures (85/116 73%). Median follow up was 5-years (64 months, IQR 52–79). Thirty limbs (30/85 35%) had undergone trans-tibial amputation at time of follow-up: there was no association between open fractures and requirement for amputation (p=0.06). Definitive treatment choice had a significant association with later requirement for amputation (p=0.0479). Fifty-two patients (52/74 70%) had been discharged from the military due to their injuries: there was a significant association between amputation and military discharge (p=0.001). Only 17 patients (17/74 23%) had been able to complete a military fitness test since their injury. The median physical component score of the SF-12 quality of life outcome tool for those undergoing amputation was 51.9 (IQR 48.1–54.3). The median for those retaining their limb was 44.1 (IQR 38.6–53.8). The difference between the two cohorts was not statistically significant (p=0.989).

Introduction

Better functional outcomes, lower pain and better stability have been reported with knee designs which restore physiological knee kinematics. Also the ability of the TKA design to properly restore the physiological femoral rollback during knee flexion, has shown to be correlated with better restoration of the flexor/extensor mechanism (appropriate flexor/extensor muscle lever arm, sufficient quadriceps force to extend the knee under load and limited patello-femoral force), which is fundamental to the function of the human knee. The purpose of the study is to compare the kinematics of three different TKA designs, by evaluating knee motion during Activities of Daily Living. The second goal is to see if there is a correlation between the TKA kinematics and the patient reported outcomes.

Introduction: The BOA recommends clinical and radiological arthroplasty follow up at one year then every five years. Increasing pressures placed on NHS Trusts with the implementation of the 18 week pathway and limitation on new:follow-up ratios has increased the use of patient reported outcome scores in arthroplasty follow-up. No single score is validated for this purpose, and there is no data surrounding their effectiveness as a screening tool for aseptic loosening.

Patients & Results: Patients undergoing their 10 year follow were included in the study and scored with the Harris (HHS), Hospital for Special Surgery (HSS), Merle d’Aubigne (MDA), Visual Analogue (VAS) or Oxford Hip Score (OHS) according to the unit’s established follow-up protocol. All patients underwent clinical and radiographic review in addition to scoring. Patients subsequently listed for revision surgery were defined as failure. Statistical analysis included significance testing and ROC analysis to determine the predictive value of the individual scores.

Four hundred and twelve patients were included in the study. The mean Harris, VAS and HSS were significantly different between the failed and well fixed groups. However there was no statistically significant difference between the mean Oxford and MDA scores. ROC analysis demonstrated the Harris (0.97), VAS (0.98) and HSS (0.77) score to have good prediction of outcome.

Discussion: The scores in our study have been validated as outcome measures for joint arthroplasty, however they perform differently in the follow-up setting. There is evidence that a failing hip is reflected in a poorer VAS, Harris, Oxford and HSS scores however the VAS was more sensitive and specific than any hip score. Patient administered outcomes have a place in the follow up of joint replacement it must be remembered they are validated as outcome measures, not for follow up purposes.

We define the medium-term outcomes following total hip replacement (THR) for hip fracture. There is currently no information regarding longer term clinical and patient reported outcomes in this group of patients selected in accordance with national guidelines.

We prospectively identified patients who underwent THR for a displaced hip fracture over a three year period between 2007 and 2010. These patients were followed up at 5 years using the Oxford hip score, Short-form 12(SF-12) questionnaire and satisfaction questionnaire.

We identified 128 patients. Mean follow up was at 5.4 years with a mean age of 76.5 years. 21 patients (16%) had died, 12 patients (9%) had developed dementia and 3 patients had no contact details, leaving a study group of 92 patients. 74 patients(80%) responded. Patients reported excellent functional outcomes and satisfaction at 5 years (mean Oxford Hip Score 40.3; SF-12 Physical Health Composite Score 44.0; SF-12 Mental Health Composite Score 46.2; mean satisfaction 90%). The rates of dislocation (2%), deep infection (2%) and revision (3%) were comparable to those quoted for elective THR. When compared with 2 year follow up, there was no statistically significant change in outcome.

Medium-term outcomes for THR after hip fracture are excellent and the early proven benefits of this surgery are sustained. Mortality rates are equivalent to elective THR registry data and significantly lower than overall mortality rates following hip fracture. Our data validates the selection process detailed in national guidelines and confirms the low complication rate. THR is a safe and highly effective treatment for fit elderly patients with displaced hip fractures.

This study describes the long term clinical and patient reported outcomes following simple dislocation of the elbow.

We identified all adult patients treated at our trauma centre for a simple dislocation of the elbow over 10 years. 140 patients were identified and 110 (79%) patients were reviewed at a mean of 88 (95% CI 80–96) months after injury. This included clinical examination, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, an Oxford Elbow questionnaire and a patient satisfaction questionnaire.

Patients reported long-term residual deficits in range of movement. The mean DASH score was 6.5 (95% CI 4 to 9). The mean Oxford Elbow score was 43.5 (95% CI 42.2 to 44.8). The mean satisfaction score was 85.6 (95% CI 82.2 to 89). Sixty-two patients (56%) reported persistent subjective stiffness of the elbow. Nine (8%) reported subjective instability and 68 (62%) complained of continued pain. The DASH, Oxford Elbow and satisfaction scores all showed good correlation with absolute range of movement in the injured elbow. After multivariate analysis, a larger elbow flexion contracture and female gender were both independent predictors of worse DASH scores. Poorer Oxford Elbow scores and overall satisfaction ratings were predicted by reduced flexion-extension arc of movement.

Patients report good long term functional outcomes after simple dislocations of the elbow. These are not entirely benign injuries. There is a high rate of residual pain and stiffness. Functional instability is less common and does not often limit activities.

Birmingham Metal-on-metal total hip resurfacing (BHR) is a bone-conserving option for patients with advanced articular damage. While the outcomes of Total Hip Replacement (THR) are well documented, there is a paucity of literature comparing the patient reported outcomes of BHR versus THR. This study aims to compare the patient reported outcomes for an impact on quality of life between patients who had a BHR vs. THR after correcting for selection bias.

Patients who underwent a BHR or THR between July 2003 and December 2006 were included. Patient questionnaires included demographic details, co-morbidities, WOMAC, SF-36 Scores. In addition, a 4 point Likert scale was used to measure satisfaction post-operatively. The above data was collected pre-operatively and at 1, 2, 3 and 5 years post-operatively. Data was analysed with SPSS (version 19) software package. All analysis was adjusted for Age, gender, Co-morbidity and pre-operative score by using Multivariate regression analysis using a General Liner Model to rule out the effect of these predictors on outcomes between groups.

337 patients were included (205 for THR and 132 for BHR). BHR patients were younger than THR patients (49 vs. 67 years, p<0.01), were more likely to be male (68% vs. 42% of THR, p<0.01), reported fewer co-morbidities (1.06 vs. 1.59, p<0.01). BHR patients reported better WOMAC pain and function scores at 5 years (p<0.05). For SF-36 scores, BHR patients reported higher scores for all 8 domains at 1 year and 5 year follow up (p<0.05). BHR patients reported higher satisfaction than THR group for return to Activities of Daily Living and Recreational activities at 1 and 5 years (p<0.05)

After correction for patient variability, BHR patients reported better improvement in pain and function and enjoyed a better quality of life in relation to return to ADL and recreational activities over to 5 years post-surgery.

Purpose of the Study

To identify trends in patient satisfaction of their knee arthroplasty, total and unicompartmental, one year post primary knee arthroplasty surgery, with reference to age, gender and primary diagnosis, from 1990 to 2008.

Triple-tapered cemented stems were developed in the hope that they would reduce aseptic loosening and prevent calcar bone loss.

Between March 2005 and April 2008, a consecutive series of 415 primary C-stem AMT hip arthroplasties in 386 patients were performed under the care of three surgeons at our institution. When all the patients had reached the 5-year anniversary of surgery, functional questionnaires were sent out by mail. In the event of non-response, reminders were sent by post before the patients were contacted by telephone. Postoperative radiographs were also reviewed.

Follow-up ranges from 60 to 99 months, with a mean of 76 months. 32 hips (8%) were lost to follow-up. The median OHS was 40, median SF-12 mental component score (MCS) was 50, and median SF-12 physical component score (PCS) was 39. Radiographic review showed that aseptic femoral component loosening has yet to be observed. At 99 months follow up, stem survivorship is 96.9% (95% confidence interval (CI) 82.5 to 99.5). Adverse events such as calcar fracture, greater trochanter fracture and dislocation were rare at <1%.

The C-stem AMT demonstrates excellent implant survivorship at 5–8 year follow-up, as well as good midterm functional outcome.

We obtained pre-operative and six-month post-operative Oxford hip (OHS) and knee scores (OKS) for 1523 patients who underwent total hip replacement and 1784 patients who underwent total knee replacement. They all also completed a six-month satisfaction question.

Scatter plots showed no relationship between pre-operative Oxford scores and six-month satisfaction scores. Spearman’s rank correlation coefficients were -0.04 (95% confidence interval (CI) -0.09 to 0.01) between OHS and satisfaction and 0.04 (95% CI -0.01 to 0.08) between OKS and satisfaction. A receiver operating characteristic (ROC) curve analysis was used to identify a cut-off point for the pre-operative OHS/OKS that identifies whether or not a patient is satisfied with surgery. We obtained an area under the ROC curve of 0.51 (95% CI 0.45 to 0.56) for hip replacement and 0.56 (95% CI 0.51 to 0.60) for knee replacement, indicating that pre-operative Oxford scores have no predictive accuracy in distinguishing satisfied from dissatisfied patients.

In the NHS widespread attempts are being made to use patient-reported outcome measures (PROMs) data for the purpose of prioritising patients for surgery. Oxford hip and knee scores have no predictive accuracy in relation to post-operative patient satisfaction. This evidence does not support their current use in prioritising access to care.

Aims. Surgery is often indicated in patients with metastatic bone disease (MBD) to improve pain and maximize function. Few studies are available which report on clinically meaningful outcomes such as quality of life, function, and pain relief after surgery for MBD. This is the published protocol for the Bone Metastasis Audit — Patient Reported Outcomes (BoMA-PRO) multicentre MBD study. The primary objective is to ascertain patient-reported quality of life at three to 24 months post-surgery for MBD. Methods. This will be a prospective, longitudinal study across six UK orthopaedic centres powered to identify the influence of ten patient variables on quality of life at three months after surgery for MBD. Adult patients managed for bone metastases will be screened by their treating consultant and posted out participant materials. If they opt in to participate, they will receive questionnaire packs at regular intervals from three to 24 months post-surgery and their electronic records will be screened until death or five years from recruitment. The primary outcome is quality of life as measured by the European Organisation for Research and the Treatment of Cancer Quality of Life questionnaire (EORTC-QLQ) C30 questionnaire. The protocol has been approved by the Newcastle & North Tyneside 2 Research Ethics Committee (REC ref 19/NE/0303) and the study is funded by the Royal College of Physicians and Surgeons of Glasgow (RCPSG) and the Association for Cancer Surgery (BASO-ACS). Discussion. This will be the first powered study internationally to investigate patient-reported outcomes after orthopaedic treatment for bone metastases. We will assess quality of life, function, and pain relief at three to 24 months post-surgery and identify which patient variables are significantly associated with a good outcome after MBD treatment. Cite this article: Bone Jt Open 2021;2(2):79–85

Introduction. We undertook a qualitative study to explore what is important to people with lower limb conditions requiring reconstruction (LLR) and how it impacted their quality of life (QOL), in order to develop a conceptual framework for a new patient reported outcome measure (PROM). This builds on a previous qualitative evidence synthesis of existing research to develop a preliminary conceptual framework as part of the Patient Reported Outcomes for Lower Limb Reconstruction (PROLLIT) study. Materials and Methods. Patients (n=32) and Orthopaedic staff (n=23) were interviewed (November 2020-June 2021) from three centres in England using one-to-one, semi-structured interviews. Patient interviews focused on experiences during and after LLR, including impact on QOL. Staff interviews explored important outcomes and goals for patients and how the LLR impacted QOL. Recordings were transcribed verbatim and analysed using thematic analysis. Results. The conceptual framework consists of 6 overarching factors important to patients: Pain, Identity, Work, Daily lifestyle, Emotional well-being and Support. These factors are not independent of each other, rather they're all interrelated (e.g. pain impacts identity, work, emotional well-being and daily lifestyle. Work impacts identity, pain, emotional well-being and daily lifestyle). Support from the hospital, physiotherapists and family underpins the other factors and acts as a moderator of their influence. Conclusions. This conceptual framework displays key factors important to patients after a LLR. Further research is required to map these factors onto existing PROMs to establish whether the factors we identified are captured by existing PROMs

Aims. The aim of this study was to compare patient-reported outcome measures (PROMs), radiological measurements, and total hip arthroplasty (THA)-free survival in patients who underwent periacetabular osteotomy (PAO) for mild, moderate, or severe developmental dysplasia of the hip. Patients and Methods. We performed a retrospective study involving 336 patients (420 hips) who underwent PAO by a single surgeon at an academic centre. After exclusions, 124 patients (149 hips) were included. The preoperative lateral centre-edge angle (LCEA) was used to classify the severity of dysplasia: 18° to 25° was considered mild (n = 20), 10° to 17° moderate (n = 66), and < 10° severe (n = 63). There was no difference in patient characteristics between the groups (all, p > 0.05). Pre- and postoperative radiological measurements were made. The National Institute of Health’s Patient Reported Outcomes Measurement Information System (PROMIS) outcome measures (physical function computerized adaptive test (PF CAT), Global Physical and Mental Health Scores) were collected. Failure was defined as conversion to THA or PF CAT scores < 40, and was assessed with Kaplan–Meier analysis. The mean follow-up was five years (2 to 10) ending in either failure or the latest contact with the patient. Results. There was no significant difference in PROMs for moderate (p = 0.167) or severe (p = 0.708) groups compared with the mild dysplasia group. The numerical pain scores were between 2 and 3 units in all groups at the final follow-up (all, p > 0.05). There was no significant difference (all, p > 0.05) in the proportion of patients achieving target correction for the LCEA between groups. The mean correction was 12° in the mild, 15° in the moderate (p = 0.135), and 23° in the severe group (p < 0.001). Failure-free survival at five years was 100% for mild, 79% for moderate, and 92% for severely dysplastic hips (p = 0.225). Conclusion. Although requiring less correction than hips with moderate or severe dysplasia, we found PAO for mild dysplasia to be associated with promising PROMs, consistent with that of the general United States population, and excellent survivorship at five years. Future studies should compare these results with the outcome after arthroscopy of the hip in patients with mild dysplasia. Cite this article: Bone Joint J 2019;101-B(6 Supple B):16–22

Aims. The Patient-Reported Outcomes Measurement Information System (PROMIS) has demonstrated faster administration, lower burden of data capture and reduced floor and ceiling effects compared to traditional Patient Reported Outcomes Measurements (PROMs). We investigated the suitability of PROMIS Mobility score in assessing physical function in the sequelae of childhood hip disease. Methods. In all, 266 adolscents (aged ≥ 12 years) and adults were identified with a prior diagnosis of childhood hip disease (either Perthes’ disease (n = 232 (87.2%)) or Slipped Capital Femoral Epiphysis (n = 34 (12.8%)) with a mean age of 27.73 years (SD 12.24). Participants completed the PROMIS Mobility Computer Adaptive Test, the Non-Arthritic Hip Score (NAHS), EuroQol five-dimension five-level questionnaire, and the Numeric Pain Rating Scale. We investigated the correlation between the PROMIS Mobility and other tools to assess use in this population and any clustering of outcome scores. Results. There was a strong correlation between the PROMIS Mobility and other established PROMs; NAHS (rs = 0.79; p < 0.001). There was notable clustering in PROMIS at the upper end of the distribution score (42.5%), with less seen in the NAHS (20.3%). However, the clustering was broadly similar between PROMIS Mobility and the comparable domains of the NAHS; function (53.6%), and activity (35.0%). Conclusion. PROMIS Mobility strongly correlated with other tools demonstrating convergent construct validity. There was clustering of physical function scores at the upper end of the distributions, which may reflect truncation of the data caused by participants having excellent outcomes. There were elements of disease not captured within PROMIS Mobility alone, and difficulties in differentiating those with the highest levels of function. Cite this article: Bone Jt Open 2021;2(12):1089–1095

Component alignment cannot fully explain total knee arthroplasty [TKA] performance with regards to patient reported outcomes and pain. Patient specific variations in musculoskeletal anatomy are one explanation for this. Computational simulations allow for the impact of component alignment and variable patient specific musculoskeletal anatomy on dynamics to be studied across populations. This study aims to determine if simulated dynamics correlate with Patient Reported Outcomes. Landmarking of key anatomical points and 3D registration of implants was performed on 96 segmented post-operative CT scans of TKAs. A cadaver rig validated platform for generating patient specific rigid body musculoskeletal models was used to assess the resultant motions. Resultant dynamics were segmented and tested for differentiation with and correlation to a 6 month postoperative Knee injury and Osteoarthritis Outcome Score (KOOS). Significant negative correlations were found between the postoperative KOOS symptoms score and the rollback occurring in midflexion (p<0.001), quadriceps force in mid flexion (p=0.025) and patella tilt throughout flexion (p=0.009, p=0.005, p=0.010 at 10°, 45° and 90° of flexion). A significant positive correlation was found between lateral shift of the patella through flexion and the symptoms score. (p=0.012) Combining a varus/valgus angular change from extension to full flexion between 0° and 4° (long leg axis) and measured rollback of no more than 6mm without roll forward forms a ‘kinematic safe zone’ of outcomes in which the postoperative KOOS score is 11.5 points higher (p=0.013). The study showed statistically significant correlations between kinematic factors in a simulation of postoperative TKR and post-operative KOOS scores. The presence of a ‘kinematic safe zone’ in the data suggests a patient specific optimisation target for any given individual patient and the opportunity to preoperatively determine a patient specific alignment target

Introduction. There is increasing pressure on healthcare providers to demonstrate competitiveness in quality, patient outcomes and cost. Robotic and computer-assisted total knee arthroplasty (TKA) have been shown to be more accurate than conventional TKA, thereby potentially improving quality and outcomes, however these technologies are usually associated with longer procedural times and higher costs for hospitals. The aim of this study was to determine the surgical efficiency, learning curve and early patient satisfaction of robotic-assisted TKA with a contemporary imageless system. Methods. The first 29 robotic-assisted TKA cases performed by a single surgeon having no prior experience with computer or robotic-assisted TKA were reviewed. System time stamps were extracted from computer surgical reports to determine the time taken from the first step in the anatomical registration process, the hip center acquisition, to the end of the last bone resection, the validation of the proximal tibial resection. Additional time metrics included: a) array attachment, b) anatomical registration, c) robotic-assisted femoral resection, d) tibial resection, e) trailing, f) implant insertion, and skin-to-skin time. The Residual Time was also calculated as the skin-to-skin time minus the time taken for steps a) to f), representing the time spent on all other steps of the procedure. Patients completed surveys at 3 months to determine their overall satisfaction with their surgical joint. Results. All time metrics decreased significantly after the first 7 cases, except the residual time (table 1 and figure 1). Mean skin-to-skin time significantly decreased from 83.7min to 57.1min (p=0.0008) beyond 7 cases, and hip center to final cut validation time decreased from 30.2min to 20.3min (p=0.0002). 85.7% (24/29) of patients were “Fully satisfied” and 14.3% (5/29) were “Partly satisfied”. Cost analysis showed there were no capital costs associated with acquisition of the robotic system and per case cost was equal to conventional TKA. Conclusion. Improvements in surgical efficiency and quality are becoming increasing important in today's healthcare environment. The results of this study indicated equal cost, a short learning curve and comparable procedure times to conventional TKA. The Patient Reported Outcomes with this group of patients was very high compared to rates reported in the literature

Introduction. Cementless total knees were historically associated with early failure. These failures, likely associated with implant design, made cemented total knee arthroplasty (TKA) the “gold standard”. Manufacturers have introduced newer uncemented technologies that provide good initial stability and utilize a highly-porous substrates for bony in-growth. Outcome data on these implants has been limited. In addition, these implants typically have a price premium which makes them difficult to use in the setting of cost containment and in at risk 90-day bundles. Our purpose was to compare 90-day outcomes of a new uncemented implant with those of a comparable cemented implant from the same manufacturer. We hypothesized that the implants would have equivalent 90-day clinical and economic outcomes. Methods. Ninety-day clinical and economic outcomes for 252 patients with prospectively collected data from the Michigan Arthroplasty Registry Collaborative Quality Initiative (MARCQI) database were reviewed. Ninety-day outcomes were compared between uncemented knees and an age-matched group of cemented knees (Triathlon cemented vs uncemented Triathalon-tritanium, Stryker Orthopedics, Mahwah, NJ, USA). Both cruciate retaining and posterior stabilized designs were included. MARCQI data: demographics, co-morbidities, length of stay, complications, emergency department visits, discharge disposition, and readmissions were reviewed. Financial data provided by the hospital's finance department was used for economic comparisons. Fischer's test was done to assess categorical data and a student's t-test was used to compare numerical data. Results. Uncemented knees had shorter length of stay (1.58 vs. 1.87, p<0.0001), were more frequently discharged home (90.48% vs. 68.75%; p<0.0001) and used less home care or extended care facilities (6.35% vs. 19.14%, p<0.0001; 2.78% vs. 11.72%, p=0.0001). More uncemented knees had “no complications”. Moreover, there were no reoperations in uncemented knees, compared to 19 reoperations in cemented knees most being manipulations (14 vs. 0, p=0.0028). Uncemented knees scored better than age matched counterparts Knee Injury and Osteoarthritis Outcomes Score (63.69 vs. 47.10, n=85 and 43, p<0.0001), and Patient Reported Outcomes Measurement Information System T-physical and T-mental (44.12 vs. 39.45, n=95 and 59, p<0.0001; 51.84 vs 47.82, n=97 and 59, p=0.0018). Cemented cases were more expensive overall, the surgical costs were higher ($6806.43 vs. $5710.78 p<0.01) and the total hospital costs were higher ($8347.65 vs. $7016.11 p<0.01). The 90-day readmission and hospital outpatient costs were not significantly different between the designs. Conclusion. The use of a modern uncemented TKA implants has increased, but data on outcomes and the economic impact has been limited particularly in regard to 90-day at risk global periods. Our study suggests that patients receiving an new uncemented TKA have a shorter length of stay, higher rate of discharge to home, better patient reported outcome measures, fewer complications and fewer reoperations than an age-matched group of patients receiving a similar, cemented design during the 90-day global period. Importantly, the uncemented knees had $1,095 less surgical episode costs (p< 0.001) and a 90-day cost savings of over $1,300 (p< 0.001). Uncemented TKA, when utilizing modern technologies, is successful and economically viable for an at-risk bundle. The results of this study should alleviate fears increased cost, early failure, complications or poor outcomes with the use of a modern uncemented TKA

Introduction. Recent studies have challenged the concept that a single ‘correct’ alignment to standardised anatomical references is the primary driver of TKA performance with regards to patient satisfaction outcomes. Patient specific variations in musculoskeletal anatomy are one explanation for this. Virtual simulated environments such as rigid body modelling allow for the impact of component alignment and variable patient specific musculoskeletal anatomy to be studied simultaneously. This study aims to determine if the output kinematics derived from consideration of both postoperative component alignment and patient specific musculoskeletal modelling has predictive potential of Patient Reported Outcomes. Method. Landmarking of key anatomical points and 3D registration of implants was performed on 96 segmented post-operative CT scans of TKAs. Both femoral and tibia implant components were registered. Acadaver rig validated platform for generating patient specific rigid body musculoskeletal models was used to assess the resultant motions and contact forces through a 0 to 140 degree deep knee bend cycle. Resultant kinematics were segmented and tested for differentiation with and correlation to a 12 month postoperative Knee injury and Osteoarthritis Outcome Score (KOOS). Results. Significant negative correlations (p<0.05) were found between the postoperative KOOS symptoms score and the rollback occurring in midflexion, quadriceps force in mid flexion, patella shear force and patella tilt at 90 degrees of flexion. A significant positive correlation was found between lateral shit of the patella through flexion and the symptoms score. (p<0.05) When segmenting those KOOS scores performing in the lowest 20% of patients, both rollback and the three patella measurements have statistically significantly different means (t test, p<0.05). There were other trends present that are discernible but do not have linear correlations, as they are cross-dependant on other kinematic factors or are not linear in nature. When segmenting the varus/valgus angular change into those with a varus angular change from extension to full flexion between 0 and 4 degrees (long leg axis, not implant to implant) and those with either further varus change or a valgus change, a statistically significant difference of 7 points (p<0.05) in the postoperative KOOS pain score is observed. Likewise, measured rollback of no more than 6mm without roll forward scored 10 points higher (p<0.05) in the postoperative KOOS score. These two parameters form a ‘kinematic safe zone' of outcomes in which the postoperative KOOS score is 12 points higher (p<0.05). Conclusions. The study showed statistically significant correlations between kinematic factors in a simulation of postoperative TKA and post-operative KOOS scores. The kinematic factors so captured are the result of both the variation in implant position and the subject specific, variable musculoskeletal anatomy. The presence of a ‘kinematic safe zone' in the data suggests a subject specific optimisation target for any given individual patient and the opportunity to preoperatively determine a subject specific implant position target

Introduction. Although we know that smoking damages health, we do not know impact of smoking on a patient's outcome following primary knee arthroplasty (KA). In the UK, clinical commissioning groups (CCGs) have the authority (& funds) to commission healthcare services for their communities. Over the past decade, an increasing number of CCGs are using smoking as a contraindication for patients with end-stage symptomatic knee arthritis being referred to a specialist for due consideration of KA without any clear evidence of the associated risks & benefits. The overall objective of this study is to compare clinical outcomes after knee arthroplasty surgery in smokers, ex-smokers & non-smokers. Methods. We obtained data from the UK Clinical Research Practice Datalink (CPRD) that contains information on over 11 million patients (7% of the UK population) registered at over 600 general practices. CPRD data was linked to Hospital Episode Statistics, hospital admissions & Patient Reported Outcome Measures (PROMs) data. We collected data on all KAs (n=64,071) performed over a 21-year period (1995 to 2016). Outcomes assessed included: local & systemic complications (at 6-months post-surgery): infections (wound, respiratory, urinary), heart attack, stroke & transient ischaemic attack, venous thromboembolism, hospital readmissions & GP visits (1-year), analgesic use (1-year), surgical revision (up to 20-years), mortality (90-days and 1-year), & 6-month change from pre-operative scores in Oxford Knee Score (OKS). Regression modelling is used to describe the association of smoking on outcomes, adjusting for confounding factors. Results. Smoking was associated with an increased risk of lower respiratory tract infections (LRTI) (4.2% smokers vs. 2.7% non-smokers) (Odds Ratio (OR) 0.76, p-value 0.017). LRTI were similar in ex-smokers & smokers at 3.9%. There was no association with any of the other 6-month complications. Pain medication use over 1-year post surgery was higher in smokers compared to non-smokers: gabapentinoids 7.4% vs. 5.2% (OR 0.74, p< 0.001), opioids 45.9% vs. 35.3% (OR 0.79, p< 0.001), NSAIDs 51.6% vs. 46.1% (OR 0.91, p = 0.044). Mortality was higher in smokers at 1-year compared to non-smokers (hazard ratio (HR) 0.53, p<0.001) & ex-smokers (HR 0.65, p = 0.037), but there was no difference observed at 90-days. There was no association of smoking on revision surgery over 20-years follow up. Smoking was associated with worse postoperative OKS being 3.1 points higher in non-smokers (p<0.001) & 3.0 points higher in ex-smokers (p<0.001). The overall change in OKS before & after surgery was 13.9 points in smokers versus 16.3 points in non-smokers (p<0.001) & 15.7 points in ex-smokers (p<0.001). Over the year following surgery, smokers were more likely to visit their GP, but there was no association with hospital readmission rates. Conclusion. This is the largest study with linked primary care & secondary care data highlighting impact of a preventable patient factor on outcome of a routinely performed planned intervention. Smokers achieved clinical meaningful improvements in patient reported pain & function (OKS) following KA, although their attained post-operative OKS was lower than in non-smokers & ex-smokers. Levels of pain medication use were notably higher in both smokers & ex-smokers. As smokers achieved good clinical outcomes following KA surgery, smoking should not be a barrier to referral for or consideration of KA. However, the study does highlight particular risks a patient is taking if he/she continues to smoke when being considered for elective knee arthroplasty. This study will help the family physicians as well as patients to make an informed decision on whether to go ahead with a planned intervention whilst patient continues to be an active smoker or not. Key Words: Knee Arthroplasty, Smoking, Patient Reported Outcomes, Epidemiology, Complications