To compare the number of airborne bacteria and particles under laminar airflow (LAF) versus turbulent airflow (TAF) with 100% and 50% reduced fresh air exchange during simulated total hip arthroplasty (THA) Two equally dimensioned operating rooms (OR) build in 2009 with modern ventilation systems of LAF and TAF respectively were used during 32 simulated THA-operations under four different ventilation conditions: LAF or TAF with either full (n=8+8) or 50% reduced (n=8+8) fresh air exchange volume. We followed a protocol controlling the complete perioperative setup including interior cleaning, sterile materials, OR-personnel procedures, surgical clothing, instruments and 50-minute surgical procedure on a full-sized dummy at 37°C. Microbial contamination was determined intra-operatively by ISO-validated Microbiological Active Sampler (MAS-100, Merck, 100 L/min) at two 10-minute intervals in 30 cm distance of the operating field. Blood-agar plates from each operation were incubated for 2 days at 35°C and the microbial concentration was determined by viable counting of colony-forming units (CFU) per m3 air. Furthermore airborne particulate (0,5–10 µm) was sampled with ISO-validated light scattering particle analyzer (MET-one, Beckman Coulter, 28,3 L/min) during the 50-minute surgical procedure (1,42 m3/operation). Large particle sizes (>5 µm) are correlated with microbial contamination (Stocks, 2010). According to standards large-sized particle number must not exceed a 2.900/m3-threshold for cleanroom operations. Microbial air concentration (mean CFU/m3 ±standard deviation) under LAF conditions with full and 50% reduced fresh air exchange were 0,4±0,8 and 0,4±0,4 respectively, whereas air contamination under TAF conditions were significantly higher with 7,6±2,0 and 10,3±8,1 (p<0,05). Large (>5 µm) airborne particulate (mean no./m3 ±standard deviation) under LAF conditions with full and 50% reduced fresh air exchange were 1.581±2.841 and 1.018±1.084 respectively, whereas particulate under TAF conditions were 7.923±5.151 and 6.157±2.439 respectively. Microbial air contamination was significantly lower under LAF ventilation compared to TAF during simulated THA under both full and 50% reduced fresh air exchange in modern operating theatres used in daily clinic. The number of particles measured under TAF conditions exceeded the threshold for cleanroom operations in 12/16 simulated operations. These findings indicate that LAF reduces the airborne microbial risk factor of surgical site infection in comparison to TAF.
The purpose of this study was to examine the utility of the acetabular component introducer as a tool to intra-operatively predict implant inclination in total hip arthroplasty. This study investigated (1) the correlation between intra-operative photographic assessment of cup inclination using the acetabular introducer and that measured on post-operative radiograph; and (2) the accuracy of intra-operative prediction of abduction angle. For this study, we prospectively recruited 56 patients scheduled to receive primary hip arthroplasty from one of two senior surgeons. During the procedure, the lead surgeon provided a prediction of the abduction angle based on the alignment of the impactor attached to the cup in its final seated position. A standardized anteroposterior (AP) photograph was then taken of the acetabular impactor Measurements of cup position made from post-operative radiographs were significantly correlated with the measurements as assessed by intra-operative photographs (r = 0.34, p = 0.00). Our findings demonstrate that radiological abduction angles tend to be greater than that assessed by intra-operative photographs by a mean of 5.6 degrees (SD = 6.6 degrees; 95% CI = 7.3 to 3.9 degrees). Conversely, surgeon prediction of cup inclination based on the acetabular introducer differed from the radiographic measurements by a mean of 6.8 degrees (SD = 8.7 degrees). There was good agreement between the two observers in both photographic and radiographic measurement (k = 0.95, k = 0.96, respectively). In conclusion, we found that the intra-operative photographic assessment of acetabular cup inclination by acetabular impactor alignment tends to underestimate the abduction angle by a mean of approximately 5 degrees. In addition, intra-operative surgeon estimation of acetabular inclination did not appear accurate in this study demonstrating that cup position should rely on additional visual cues beyond that captured in the anteroposterior view of the cup introducer.
Alignment of the initial femoral guidewire is critical in avoiding technical errors that may increase the risk of failure of the femoral component. A novel alternative to conventional instrumentation for femoral guidewire insertion is a computed tomography (CT) based alignment guide. The aim of this study was to assess the accuracy of femoral component alignment using a CT-based, patient specific femoral alignment guide. Between March 2010 and January 2011, 25 hip resurfacings utilizing a CT-based femoral alignment guide were performed by three surgeons experienced in hip resurfacing. Stem-shaft angle (SSA) accuracy was assessed using minimum 6 week post-operative digital radiographs. A benchside study was also conducted utilizing six pairs of cadaveric femora. Each pair was divided randomly between a group utilizing firstly a conventional lateral pin jig followed by computer navigation and a group utilizing a CT-based custom jig. Guidewire placement accuracy for each alignment method was assessed using AP and lateral radiographs.Introduction:
Methods:
The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examinedwhether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing. Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy.Purpose:
Methods:
One method of femoral head preservation following avascular necrosis (AVN) is core decompression and Tantalum Rod insertion. There is, however, a published failure rate of up to 32% at 4 years. The purpose of the present study was to document the clinical and radiological outcome following Total Hip Arthroplasty (THA) subsequent to failed Tantalum Rod insertion. Twenty-five failed Tantalum Rod insertions subsequently requiring THA were identified from a prospectively updated database. Seventeen patients met minimum 2 year clinical and radiographic follow-up criteria. St. Michael's Hip (SMH) scores were compared to a matched cohort of patients with THA for AVN without prior Tantalum Rod insertion. Postoperative radiographs were reviewed assessing component alignment, linear wear (Dorr & Wan) and presence of tantalum residue within the joint space.Introduction:
Methods:
Computer navigation for hip resurfacing has been shown to reduce the incidence of technical error during femoral head preparation and provides increased accuracy compared to conventional instrumentation for insertion of the initial femoral guidewire. Limitations to the widespread use of navigation in hip resurfacing include access and cost. A novel, patient specific nylon jig has been developed as a cost effective alternative for placement of the initial guidewire. The purpose of this study was to compare the accuracy of femoral guidewire insertion between imageless navigation, conventional instrumentation and a new type of CT-based custom jig. Six pairs of cadaveric femora were used in the study. Each pair was divided randomly between a group utilizing firstly a conventional lateral pin jig (BHR, Smith & Nephew Inc.) followed by navigation (Vector Vision SR, BrainLAB) and a group utilizing a CT-based, patient specific custom jig (Visionaire, Smith & Nephew Inc.). A single surgeon inserted all guidewires. The planned guidewire position was approximately 10 degrees of relative valgus to the native neck-shaft angle in the coronal plane and neutral version in the sagittal plane. The same coronal alignment angle was used between paired femora. Femurs were positioned in a draped synthetic foam hip model prepared with a standard posterior approach. Guidewire insertion time and placement accuracy for each of the three alignment methods was assessed. Guidewire placement accuracy for coronal inclination and version was assessed by anteroposterior and lateral digital radiographs and was defined as the mean deviation from the planned alignment value.Purpose
Method
The Birmingham Mid-Head Resection (BMHR) is a bone-conserving, short-stem alternative to hip resurfacing for patients with compromised femoral head anatomy. It is unclear, however, if an uncemented, metaphyseal fixed stem confers a mechanical advantage to that of a traditional hip resurfacing in which the femoral prosthesis is cemented to the prepared femoral head. Thus, we aimed to determine if a metaphyseal fixed, bone preserving femoral component provided superior mechanical strength in resisting neck fracture compared to a conventional hip resurfacing arthroplasty. Sixteen matched pairs of human cadaveric femurs were divided evenly between specimens receiving a traditional epiphyseal fixed hip resurfacing arthroplasty (BHR) and those receiving a metaphyseal fixed BMHR. Pre-preparation scaled digital radiographs were taken of all specimens to determine anatomical parameters as well as planned stem-shaft angles and implant sizes. A minimum of 10 degrees of relative valgus alignment was planned for all implants and the planned stem-shaft angles and implant sizes were equal between femur pairs. Prior to preparation, bone mineral density scans of the femurs were obtained. Prepared specimens were potted, positioned in single-leg stance and tested to failure using a mechanical testing machine. Load-displacement curves were used to calculate construct stiffness, failure energy and ultimate failure load.Purpose
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