The aim of this study was to assess the impact of Covid-19 measures on the rate of surgical site infections (SSI) and subsequent readmissions in orthopaedic patients.

Retrospective, observational study in a level 1 major trauma center comparing rates of SSI in orthopaedic patients who underwent surgery prior to the Covid-19 lockdown versus that of patients who underwent surgery during the lockdown period. A total of 1151 patients were identified using electronic clinical records over two different time periods; 3 months pre Covid-19 lockdown (n=680) and 3 months during the Covid-19 lockdown (n=470). Patients were followed up for 1 year following their initial procedure. Primary outcome was readmission for SSI. Secondary outcomes were treatment received and requirement for further surgeries.

The most commonly performed procedures were arthroplasty and manipulation under anaesthesia with 119 in lockdown vs 101 non-lockdown (p=0.001). The readmission rate was higher in the lockdown group with 61 (13%) vs 44 (6.5%) in the non-lockdown group (p <0.001). However, the majority were due to other surgical complications such as dislocations. Interestingly, the SSI rates were very similar with 24 (5%) in lockdown vs 28 (4%) in non-lockdown (p=0.472). Twenty patients (4.2%) required a secondary procedure for their SSI in the lockdown group vs 24 (3.5%) in non-lockdown (p=0.381). Mortality rate was similar at 44 (9.3%) in lockdown vs 61 (9.0%; p=0.836).

Whilst Covid-19 precautions were associated with higher readmission rates, there was no significant difference in rate of SSI between the two groups.

Canada is second only to the United States worldwide in the number of opioid prescriptions per capita. Despite this, little is known about prescription patterns for patients undergoing total joint arthroplasty (TJA). The purpose of this study was to detail preoperative opioid use patterns and investigate the effect it has on perioperative quality outcomes in patients undergoing elective total hip and total knee arthroplasty surgery (THA and TKA).

The study cohort was constructed from hospital Discharge Abstract Data (DAD) and National Ambulatory Care Reporting System (NACRS) data, using Canadian Classification of Health Intervention codes to select all primary THA and TKA procedures from 2017-2020 in Nova Scotia. Opioid use was defined as any prescription filled at discharge as identified in the Nova Scotia Drug Information System (DIS). Emergency Department (ED) and Family Doctor (FD) visits for pain were ascertained from Physician Claims data. Multivariate logistic regression was used to test for associations controlling for confounders. Chi-squared statistics at 95% confidence level used to test for statistical significance.

In total, 14,819 TJA patients were analysed and 4306 patients (29.0%) had at least one opioid prescription in the year prior to surgery. Overall, there was no significant difference noted in preoperative opiate use between patients undergoing TKA vs THA (28.8% vs 29.4%). During the period 2017-2019 we observed a declining year-on-year trend in preoperative opiate use. Interestingly, this trend failed to continue into 2020, where preoperative opiate use was observed to increase by 15% and exceeded 2017 levels. Within the first 90 days of discharge, 22.9% of TKA and 20.9% of THA patients presented to the ED or their FD with pain related issues. Preoperative opiate use was found to be a statistically significant predictor for these presentations (TKA: odds ratio [OR], 1.45; 95% confidence interval [CI], 1.29 to 1.62; THA: OR, 1.46; 95% CI, 1.28 to 1.65).

Preoperative opioid consumption in TJA remains high, and is independently associated with a higher risk of 90 day return to the FD or ED. The widespread dissemination of opioid reduction strategies introduced during the middle of the last decade may have reduced preoperative opiate utilisation. Access barriers and practice changes due to the COVID-19 pandemic may now have annulled this effect.

The coronavirus pandemic has reduced the capability of Canadian hospitals to offer elective orthopaedic surgery requiring admission, despite ongoing and increasing demands for elective total hip and total knee arthroplasty surgery (THA and TKA). We sought to determine if the coronavirus pandemic resulted in more outpatient THA and TKA in Nova Scotia, and if so, what effect increased outpatient surgery had on 90 day post-operative readmission or Emergency Department/Family Doctor (FD) visits.

The study cohort was constructed from hospital Discharge Abstract Data (DAD), inpatient admissions, and National Ambulatory Care Reporting System (NACRS) data, day surgery observations, using Canadian Classification of Health Intervention codes to select all primary hip and knee procedures from 2005-2020 in Nova Scotia. Emergency Department and General Practitioner visits were identified from the Physician Billings data and re-admissions from the DAD and NACRS. Rates were calculated by dividing the number of cases with any visit within 90 days after discharge. Chi-squared statistics at 95% confidence level used to test for statistical significance. Knee and hip procedures were modelled separately.

There was a reduction in THA and TKA surgery in Nova Scotia during the coronavirus pandemic in 2020. Outpatient arthroplasty surgery in Nova Scotia in the years prior to 2020 were relatively stable. However, in 2020 there was a significant increase in the proportion and absolute number of outpatient THA and TKA. The proportion of THA increased from 1% in 2019 to 14% in 2020, while the proportion of TKA increased from 1% in 2019 to 11% in 2020. The absolute number of outpatient THA increased from 16 cases in 2019, to 163 cases in 2020. Outpatient TKA cases increased from 21 in 2019, to 173 in 2020. The increase in outpatient surgery resulted in an increase in 90 day presentations to ED following TKA but not THA which was not statistically significant. For outpatient THA and TKA, there was a decrease in 90 day readmissions, and a statistically significant decrease in FD presentations.

Outpatient THA and TKA increased significantly in 2020, likely due to the restrictions imposed during the coronavirus pandemic on elective Orthopaedic surgery requiring admission to hospital. The increase in outpatient surgery resulted in an increase in 90 day presentations to ED for TKA, and a decrease in 90 day readmissions and FD presentations for THA and TKA. Reducing the inpatient surgical burden may result in a post-operative burden on ED, but does not appear to have caused an increase in hospital readmission rates.

Aims

A pragmatic multicentre randomized controlled trial, UK FROzen Shoulder Trial (UK FROST), was conducted in the UK NHS comparing the cost-effectiveness of commonly used treatments for adults with primary frozen shoulder in secondary care.

The dual mobility design concept for acetabular components is intended to reduce the risk of dislocation and increase range of motion, but the wear pattern of this design is unclear and may have implications in implant fixation. Additionally, the solid back cups do not have the option for supplementary screw fixation, providing an additional smooth articulating surface for the liner to move against. The objective of this study was to assess cup fixation by measuring implant migration as well as proximal femoral head penetration to evaluate wear performance.

Thirty subjects were recruited in a consecutive series prospective study and received dual mobility uncemented acetabular components with mobile bearing polyethylene liners through a direct lateral approach. Femoral stems were cemented or uncemented. All subjects had 28 mm femoral heads. The femur, acetabulum, and non-articulating surface of the mobile polyethylene liner were marked with tantalum beads. Radiostereometric analysis (RSA) exams were performed post-operatively and at 6 weeks, 3 months, 6 months, 1 year, 2 years, and 3 years. Oxford 12 Hip and Satisfaction questionnaire responses were recorded. Mobile bearing motion was assessed under fluoroscopy for a single case under loaded and unloaded conditions.

Twenty-nine subjects (17 female) proceeded to surgery. Subjects were 63±11 years of age with BMIs of 28±4.7 kg/m2. Cup migration reached 0.16 ± 0.31 mm of proximal translation and 0.29±1.03 degrees of sagittal rotation at three years. A single individual had more than 3 degrees of cup rotation, occurring by 6 months and not substantially increasing after this time. Proximal translation was low for this subject. Wear of the highly cross-linked mobile bearings was 0.18 ± 0.30 mm of proximal femoral head penetration from 0 to 3 years. The mean wear rate from 1 to 3 years was 0.02 mm/year. One subject was an outlier for wear, with more than 1 mm of femoral head penetration at 1 year. However, wear did not increase after 1 year for this subject and cup migrations were below average for this individual. Similarly, the outlier for cup rotation had below average wear. Satisfaction (out of 100%) improved from 25±27% to 96±7% pre-operatively to 3 years post-operatively. Oxford 12 scores (best possible score of 48) improved from 21±7 to 43±7 over the same period. The fluoroscopic case study demonstrated visible motion of the mobile bearing during hip rotation tasks.

The overall migration of the cup was low and demonstrated favorable patterns suggesting low risk of aseptic loosening. Wear rates are also within the expected range of 0 to 0.06 mm/year for highly cross-linked polyethylene. The combination of low subsidence and low sagittal rotations of the cup, and low wear of the polyethylene are favorable predictors of good long-term performance.

Objective evaluations of resident performance can be difficult to simulate. A novel competency based surgical OSCE was developed to evaluate surgical skill. The goal of this study was to test the construct validity comparing previously validated Ottawa scores (O-scores) and Orthopaedic in-training evaluation scores (OITE).

An OSCE designed to simulate typical general orthopaedic surgical cases was developed to evaluate resident surgical performance. Post-graduate year (PGY) 3–5 trainees have an encounter (interview and physical exam) with a standardized patient and perform a correlating surgery on a cadaver. Examiners evaluate all components of the treatment plan and provide an overall score on the OSCE and also provide an O-score on overall surgical performance. Convergent and divergent validity was assessed comparing OSCE scores to O-scores and OITE scores. SPSS was used for statistical analysis. ANOVA was used to compare PGY averages and Pearson correlation coefficients were calculated to compare OSCE versus O-score and OITE scores.

A total of 96 simulated surgical cases were evaluated over a 3 year period for 24 trainees. There was a significant difference in OSCE scores based on year of training. (PGY3 − 6.06/15, PGY4 − 8.16/15 and PGY5 − 11.14/15, p < 0 .001). OSCE and O-scores demonstrated a strong positive correlation of +0.89 while OSCE and OITE scores demonstrated a moderate positive correlation of 0.68.

OSCE scores demonstrated strong convergent and moderate divergent correlation. A positive trajectory based on level of training and stronger correlations with established, validated scores supports the construct validity of the novel surgical OSCE.

Up to 20 percent of patients remain dissatisfied after primary total knee arthroplasty (TKA) surgery. Understanding the reasons for dissatisfaction post TKA may allow for better patient selection and optimized treatment for those who remain dissatisfied. The association between function, mobility and satisfaction are not well understood. The purpose of this study was to investigate the association between post-TKA satisfaction and i) pre-operative, ii) post-operative, and iii) change in knee joint function during gait.

Thirty-one patients scheduled to receive primary TKA for knee osteoarthritis (OA) diagnosis were recruited and visited the Dynamics of Human Motion laboratory for instrumented walking gait analysis (using a synchronized NDI Optotrak motion capture system and AMTI force platforms in the walkway) at two time points, first within the week prior to their surgery, and second at approximately one year after surgery. At their post-operative visit, patients were asked to indicate their satisfaction with their knee prosthesis on a scale from zero to 100, with zero being totally unsatisfied and 100 being completely satisfied. Knee joint mechanics during gait at both time points were characterized by discriminant scores, the projection of their three-dimensional knee angles and moments during gait onto an existing discriminant model that was created to optimize separation of severe knee OA and healthy asymptomatic gait patterns. This discriminant model was created using data from 73 healthy participants and 73 with severe knee OA, and includes the magnitude and pattern features (captured with principal component analysis) of the knee adduction and flexion moment, and the magnitude of the knee flexion angle during gait. Larger discriminant scores indicate improved function toward healthy patterns, and smaller scores indicate more severe function. Associations between post-operative satisfaction and pre, post and change in discriminant scores were examined using Pearson correlation analyses. We also examined associations between satisfaction and pre-operative BMI, EQ5D and Oxford 12 scores, as well as changes in these scores from pre to post-TKA.

Discriminant scores representing knee joint function during gait significantly improved on average after surgery (P =0.05).

While overall knee joint function improved after primary TKA surgery, the amount of improvement in function was not reflected in post-operative patient satisfaction. However, the pre-operative function of the patient was negatively associated with satisfaction, indicating that patients with higher pre-operative function are overall less satisfied with their TKA surgery, regardless of any functional improvement due to the surgery. Interestingly, the only significant association with post-operative satisfaction was knee joint function, and the relationship between function and patient satisfaction following TKA appears to relate only to the baseline functional state of the patient, and not with functional improvement. This suggests that dissatisfaction post-surgery is more likely reflecting the unmet expectations of a higher functioning patient, and has implications for the need for improved understanding of pre-operative patient functional variability in TKA triage and expectation management.

The trabecular metal Monoblock TKR is comprised of a porous tantalum base plate with the polyethylene liner embedded directly in the porous metal. An alternative design, the trabecular metal Modular TKR, allows polyethylene liner insertion into the locking base plate after base plate implantation, but removes the low modulus of elasticity that was inherent in the Monoblock design. The purpose of this study was to compare the fixation of the Monoblock and Modular trabeucular metal base plates in a randomised controlled trial.

Fifty subjects (30 female) were randomly assigned to receive the uncemented trabecular metal Monoblock or uncemented trabecular metal Modular knee replacement. A standard procedure of tantalum marker insertion in the proximal tibial and polyethylene liner was followed with uniplanar radiostereometric analysis (RSA) examinations immediately post-operatively and at 6 week, 3 month, 6 month, and 12 month follow-ups. The study was approved by the Research Ethics Board and all subjects signed an Informed Consent Form.

Twenty-one subjects received Monoblock components and 20 received Modular components. An intra-operative decision to use cemented implants occurred in 5 cases and 4 subjects did not proceed to surgery after enrollment. The clinical precision of implant migration measured as maximum total point motion (MTPM) was 0.13 mm (upper limit of 95% confidence interval of double exams). Implant migration at 12 months was 0.88 ± 0.64 mm (mean and standard deviation; range 0.21 – 2.84 mm) for the Monoblock group and 1.60 ± 1.51 mm (mean and standard deviation; range 0.27 – 6.23 mm) for the Modular group. Group differences in 12 month migration approached clinical significance (p = 0.052, Mann Whitney U-test).

High early implant migration is associated with an increased risk for late aseptic loosening. Although not statistically significant, the mean migration for the Modular component group was nearly twice that of the Monoblock, which places it at the 1.6 mm threshold for “unacceptable” early migration (Pijls et al 2012). This finding is concerning in light of the recent recall of a similar trabecular metal modular knee replacement and adds validity to the use of RSA in the introduction of new or modified implant designs.

Reference: Pijls, B.G., et al., Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties. Acta Orthop, 2012. 83(6): p. 614–24.

Total knee arthroplasty (TKA) has been shown to improve knee joint function during gait post-operatively. However, there is considerable patient to patient variability, with most gait mechanics metrics not reaching asymptomatic levels. To understand how to target functional improvements with TKA, it is important to identify an optimal set of functional metrics that remain deficient post-TKA. The purpose of this study was to identify which combination of knee joint kinematics and kinetics during gait best discriminate pre-operative gait from postoperative gait, as well as post-operative from asymptomatic.

Seventy-three patients scheduled to receive a TKA for severe knee osteoarthritis underwent 3D gait analysis 1 week before and 1 year after surgery. Sixty asymptomatic individuals also underwent analysis. Eleven discrete gait parameters were extracted from the gait kinematic and kinetic waveforms, as previously defined (Astephen et al., J Orthop Res., 2008). Stepwise linear discriminant analyses were used to determine the sets of parameters that optimally separated pre-operative from post-operative gait, and post-operative from asymptomatic gait. Cross-validation was used to quantify group classification error.

Knee flexion angle range, knee adduction moment first peak, and gait velocity were included in the optimal discriminant function between the pre- and post-operative groups (P<0.05), with relatively equal standardised canonical coefficients (0.567, −0.501, 0.565 respectively), and a total classification rate of 74%. A number of metrics were included in the discriminant function to optimally separate post-operative and asymptomatic gait function, including the knee flexion angle range, peak stance knee flexion angle, minimum late stance knee extension moment, minimum mid-stance knee adduction moment, and peak knee internal rotation moment (P<0.05). The mid-stance knee adduction moment had the largest standardised canonical coefficients in the function, and 89.5% of cases were correctly classified.

Separation of pre and post-operative gait patterns included only three parameters, suggesting that current standard of care TKA significantly improves only walking velocity, knee flexion angle range, and the peak value of the knee adduction moment. A number of gait metrics, which were included in the discriminant function between post-operative and asymptomatic gait, could benefit from further improvement either through rehabilitation or design. With almost 90% classification, separation of post-operative gait function from asymptomatic levels is significant. The consolidation of knee joint function during gait into single, discrete discriminant scores allows for an efficient summary representation of patient-specific (or implant-specific) improvement in gait function from TKA surgery.

Introduction

Debate over appropriate alignment in total knee arthroplasty has become a topical subject as technology allows planned alignments that differ from a neutral mechanical axis. These surgical techniques employ patient-specific cutting blocks derived from 3D reconstructions of pre-operative imaging, commonly MRI or CT. The patient-specific OtisMed system uses a detailed MRI scan of the knee for 3D reconstruction to estimate the kinematic axis, dictating the cutting planes in the custom-fit cutting blocks machined for each patient [1, 2].

The purpose of this study was to evaluate the correlation between post-operative limb alignment and implant migration in subjects receiving shape match derived kinematic alignment.

Introduction

Surgical techniques for implant alignment in total knee arthroplasty (TKA) is a expanding field as manufacturers introduce patient-specific cutting blocks derived from 3D reconstructions of pre-operative imaging, commonly MRI or CT. The patient-specific OtisMed system uses a detailed MRI scan of the knee for 3D reconstruction to estimate the kinematic axis, dictating the cutting planes in the custom-fit cutting blocks machined for each patient. The resulting planned alignment can vary greatly from a neutral mechanical axis. The purpose of this study was to evaluate the early fixation of components in subjects randomized to receive shape match derived kinematic alignment or conventional alignment using computer navigation. A subset of subjects were evaluated with gait analysis.

Introduction

The dual mobility design concept for acetabular liners is intended to reduce the risk of dislocation and increase range of motion, but the wear pattern of this design is unclear and may have implications in implant fixation. Additionally, the solid back cups do not have the option for supplementary screw fixation, providing an additional smooth articulating surface for the liner to move against. The objective of this study was to assess cup fixation by measuring implant migration. A secondary objective was to evaluate the mobile bearing motion after rotating the hip.

Purpose

To evaluate the five year Radiostereometric Analysis (RSA) results of the NexGen LPS Trabecular Metal Tibial Monoblock component (TM) and the NexGen Option Stemmed cemented component (Cemented), (Zimmer, Warsaw IN).