Introduction

Carriers of Staphylococcus aureus, both methicillin sensitive (MSSA) and methicillin resistant (MRSA), have an increased risk for health-care associated infections. Despite WHO recommendations there is currently no national screening and eradication policy for the detection of MSSA in the UK or USA. This study aimed to evaluate the effectiveness of current standard MRSA eradication therapies in the context of S. aureus decolonisation prior to joint replacement surgery.

Use of large databases for orthopaedic research has increased exponentially. Each database represents unique patient populations and vary in methodology of data acquisition. The purpose of this study was to evaluate differences in reported demographics, comorbidities and complications following total hip arthroplasty (THA) amongst four commonly used databases.

Patients who underwent primary THA during 2010–2012 were identified within National Surgical Quality Improvement Programs (NSQIP), Nationwide Inpatient Sample (NIS), Medicare Standard Analytic Files (MED) and Humana Claims Database (HAC). NSQIP definitions for comorbidities and surgical complications were queried in NIS, MED, and HAC using coding algorithms. Age, sex, comorbidities, inpatient and 30-day postoperative complications were compared (NIS has inpatient data only).

Primary THAs from each database were 22,644 (HAC), 371,715 (MED), 188,779 (NIS) and 27,818 (NSQIP). Age and gender distribution were similar between databases. There was variability in the prevalence of comorbidities and complications depending upon the database and duration of post-operative follow-up. HAC and MED had twice the prevalence of COPD, coagulopathy and diabetes than NSQIP. NSQIP had more than twice the obesity than NIS. HAC had more than twice the rates of 30-day complications at all endpoints compared to NSQIP and more than twice the DVTs, strokes and deep infection as MED at 30-days post-op. Comparison of inpatient and 30-day complications rates demonstrated more than twice the amount of infections and DVTs are captured when analysis is extended from inpatient stay to 30-days post-op.

Amongst databases commonly used in orthopaedic research, there is considerable variation in complication rates following THA depending upon the database. It will be important to consider these differences when critically evaluating database research. Additionally, with the advent of bundled payments, these differences must be considered in risk adjustment models.

Nasal carriers of methicillin sensitive Staphylococcus aureus (MSSA) have an increased risk for health-care associated infections. There is currently no national screening policy for the detection of MSSA in the UK. This study aimed to: evaluate the diagnostic performance of molecular and culture techniques in MSSA screening, determine the cause of any discrepancy between the diagnostic techniques, and model the potential effect of different diagnostic techniques on MSSA detection in orthopaedic patients. Paired nasal swabs for PCR assay and culture of S. aureus were collected from a study population of 273 orthopaedic outpatients due to undergo joint replacement surgery.

The prevalence of MSSA nasal colonisation was found to be between 22.4–35.6%. The current standard direct culturing methods for detecting S. aureus significantly underestimated the prevalence (p=0.005), failing to identify its presence in ∼1/3 of patients undergoing joint replacement surgery.

Modelling these results to national surveillance data, it was estimated that 800–1200 MSSA surgical site infections could be prevented annually in the UK by using alternative diagnostic methods to direct culture in pre-operative MSSA screening and eradication programmes.

Introduction

Patellar mobilisation methods used during total knee arthroplasty (TKA) have been debated in the literature, with some proponents of minimally invasive TKA suggesting that laterally retracting, rather than everting the patella may be beneficial. It was our hypothesis that by using randomised, prospective, blinded study methods, there would be no significant difference in clinical outcome measures based solely on eversion of the patella during total knee arthroplasty.

Introduction

Although Total Knee Arthroplasty (TKA) has been shown to correct abnormal frontal plane knee biomechanics, little is known about this effect beyond 6 months. The purpose of this study was to compare sequentially the knee adduction moment during level-walking before and after TKA in varus knees. We hypothesized that adduction moment would diminish after TKA proportionate to the tibio-femoral realignment in degrees.

Introduction: Studies have shown a strong relationship between knee osteoarthritis (OA) and the adduction moment at the knee during gait. Total knee arthroplasty (TKA) is known to improve range of motion and function in patients with severe OA. Examinations of tibial bearing wear suggest that although the static alignment of the joint is restored, the abnormal dynamic loading conditions may still remain. The aim of this study was to compare the pre-op and post-op knee biomechanics during gait in patients undergoing TKA.

Methods: Gait analysis was performed on 15 patients with 17 TKA’s (8 women and 7 men, all with pre-op varus knee alignment) prior to, 6 months and 1 year following TKA. Reflective markers were placed on the lower extremity of each patient and motion data were collected at 60 Hz using six infrared cameras (Qtrac, Qualysis). Ground reaction forces were recorded at 960 Hz with a multicomponent force plate (Kistler). The frontal plane knee moment (adduction/abduction) was calculated for each trial using inverse dynamics. Based on the anterior/posterior ground reaction force, the stance phase of each trial was divided into a braking phase and a propulsive phase. The area under the knee adduction moment curve (knee adduction impulse) was calculated for each phase. A repeated-measures (Time x Phase) ANOVA was used to compare changes in the peak knee adduction moment and knee adduction impulse for each phase over time. P-values less than 0.05 were considered significant.

Results: Mean knee alignment was 4.75 degrees varus pre-op and 4.25 degrees valgus post-op (P < 0.001). A significant time-by-phase interaction was found for peak adduction moment (P = 0.002) and a nearly significant time-by-phase interaction was found for adduction impulse (P = 0.056). In braking phase, six months after surgery, knee adduction impulse and peak moment decreased 26% and 15% respectively. At one year, however, both increased by 20% and 19% respectively to near pre-op levels. In propulsive phase, knee adduction impulse and moment decreased 34% and 25% respectively at 6 months but only increased by 4% and 11% respectively at one year follow-up. Knee Society and Function scores improved from 50.17 and 61.67 pre-op to 82.08 and 82.50 at 6 months and 88.83 and 85.83 at 1 year post-op (P < 0.001, respectively).

Discussion: After TKA, in the breaking phase of gait, the initial improvement in knee adduction impulse and peak knee adduction moment noted at 6 months disappeared completely indicating no improvement in medial compartment loading conditions at 1 year post operatively. The improvement in these parameters during the propulsive phase remained persistent at 1 year although there was some tendency to revert back to pre-operative levels. This would suggest that restoration of anatomic axial alignment and soft tissue balance do not change the medial loading conditions following TKA.