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Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_9 | Pages 89 - 89
1 May 2016
Megahed R Stocks O Ismaily S Stocks G Noble P
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Introduction

The success of knee replacement surgery depends, in part, on restoration of the correct alignment of the leg with respect to the load-bearing vector passing from the hip to the ankle (the mechanical axis). Conventional thinking is that the correct angle of resection of the distal femur (Valgus Cut Angle, VCA) depends on femoral length or femoral offset, though femoral bowing, in addition to length and medial offset, may also have a significant influence on the VCA. We hypothesized that femoral bowing has a strong effect on the VCA necessary to restore physiologic alignment after arthroplasty or osteotomy.

Methods

A total of 102 long-leg radiographs were obtained from patients scheduled for primary total knee arthroplasty. The patients on average were 41% male 59% female, 67.9 ± 11.1 years, 67.0 ± 4.7 in, 192 ± 43 lbs, and had a BMI of 29.7 ± 4.8. All radiographs were prepared with the feet placed in identical rotation and the patellae pointing forward, and were excluded if there was evidence of malrotation, as defined by (i) a difference in the medial head offsets of the right and left femur of >3mm, (ii) a difference in the width of the tibiofibular syndesmoses, or (iii) a difference in the rotation of one foot compared to the other.

The following anatomic variables were measured on each radiograph: (i) the neck shaft angle (NSA) of the femur, (ii) the length of the femur, (iii) the length of the femoral shaft, (iv) the medial head offset, (v) the medial-lateral bow of the distal femur, (vi) the hip- knee axis angle, (vii) the mechanical axis deviation of the extremity at the knee, (viii) the medio-lateral bow of the tibia, and (ix) the valgus cut angle required to restore the mechanical axis to the center of the knee during surgery (VCA). Bivariate plots were constructed using the measurements thought to influence the VCA: femoral bowing, femoral offset, and length of femur. Multivariate regression was then used to find the variable that had the strongest effect on the VCA.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_3 | Pages 94 - 94
1 Jan 2016
Osadebe U Brekke A Ismaily S Loya-Bodiford K Gonzalez J Stocks G Mathis KB Noble P
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Background

With the rising demand for primary total hip arthroplasty (THA), there has been an emphasis on reducing the revision burden and improving patient outcomes. Although studies have shown that primary THA effectively minimizes pain and restores normal hip function for activities of daily living, many younger patients want to participate in more demanding activities after their operation. The purpose of this study was to examine the relationship between age, gender and patient satisfaction after total hip arthroplasty.

Methods

With IRB approval, 2 groups of subjects were enrolled in this study: (i) 143 patients at an average of 25 months (range 10–69 months) post-primary THA, and (ii) 165 control subjects with no history of hip surgery or hip pathology. All subjects were assigned to one of four categories according to their age and gender: Group A: 40–60 year old males (31 THA; 42 Controls), Group B: 40–60 year old females (25 THA; 53 Controls), Group C: 60–80 year old males (35 THA; 25 Controls), and Group D: 60–80 year old females (36 THA; 23 Controls). Each patient completed a self-administered Hip Function Questionnaire (HFQ) which assessed each subject's satisfaction, expectations, symptoms and ability to perform a series of 94 exercise, recreational and daily living activities. These included participation in work-out activities, adventure and water sports, running and biking, and contact and team sports. Each participant was also asked their activity frequency, symptom prevalence and satisfaction with their hip in performing each activity.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXV | Pages 223 - 223
1 Jun 2012
Stocks G O'Connor D Self S Marcek G Thompson B
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Postoperative sepsis is a costly and potentially devastating problem in total joint arthroplasty. Airborne bacteria and other viable microorganisms shed from surgical staff are a source of deep prosthetic infection, and the density of airborne bacteria is correlated with the rate of postoperative joint sepsis in total joint arthroplasty surgery. Previous studies have also reported a positive relationship between the density of nonviable airborne particulate and viable CFU counts, both airborne and in the surgical wound, during surgery. The purpose of this study was to determine the extent to which a system that delivers a small field of local, directed HEPA-filtered air flow over the surgical field reduces airborne particulate and airborne bacteria during total hip arthroplasty. A minimum of 8 subjects per group provided 80% power (a = 0.05) to detect a =75% difference in bacterial density between groups. All patients who consented to undergo primary total hip arthroplasty were eligible. Thirty-six patients were prospectively randomized into three groups: directed air flow, air flow system present but turned off (sham), and control (standard) conditions. Airborne particulate and bacteria were continuously collected in consecutive 10 minute intervals within 5 cm of the surgical wound using an air sampling device. Data were analyzed using a generalized linear model for repeated measures. Particulate counts and bacterial density at the surgical site were 80% lower on average in the directed air flow group compared to the other two groups (p<0.001) (Figure 1). Density of particulate >10 μm in diameter was strongly related to bacterial density at the surgical site (p<0.001), as was staff count (p<0.001) and bacterial density at a control site that was remote from the surgical field (p<0.001). The directed air flow system's effectiveness in reducing bacteria appears to be related to its ability to reduce particulate that may carry and allow proliferation of bacteria. The directed air flow system is relatively simple to use and does not appear to hinder the function of the surgeon or operating room staff, impede access to the surgical site, or interfere with the surgical procedure. The directed air flow system can be used in any operating room environment to provide clean air equivalent to a properly-used, well-functioning laminar air flow system. The directed air flow system was effective in reducing airborne particulate and bacteria in the surgical field during total hip arthroplasty.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXV | Pages 174 - 174
1 Jun 2012
Noble P Conditt M Thompson M Usrey M Stocks G
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Introduction

Femoro-acetabular impingement (FAI) is a common source of impaired motion of the hip, often attributed to the presence of an aspherical femoral head. However, other types of femoral deformity, including posterior slip, retroversion, and neck enlargement, can also limit hip motion. This study was performed to establish whether the “cam” impinging femur has a single deformity of the head/neck junction or multiple abnormalities.

Materials and Methods

Computer models of 71 femora (28 normal and 43 “cam” impinging) were prepared from CT scans. Morphologic parameters describing the dimensions of the head, neck, and medullary canal were calculated for each specimen. The anteversion angle, alpha angle of Notzli, beta angle of Beaulé, and normalized anterior heads offset were also calculated. Average dimensions were compared between the normal and impinging femora.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_IV | Pages 442 - 442
1 Nov 2011
Stocks G Self S Thompson B Adame X O’Connor D
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Prevention of surgical infection following joint arthroplasty is preferable to treatment.

Prevention requires identification and control of the potential sources of microbial contamination. The purpose of this study was to determine whether the density of airborne particulate in the operating room during total joint arthroplasty could predict the density of viable airborne bacteria at the surgery site.

A standard particle analyzer was used to measure the number and diameters of airborne particulate during 22 joint arthroplasty surgeries performed in non-laminer flow rooms. An impact air sampler and standard culture plates were used to collect airborne particulate and were analysed to identify and count colony-forming units.

Particulate density averaged > 500,000 particles/ft3, and 1,786 colony-forming units were identified, primarily gram-positive cocci. The density of particles ≥10um explained 41% of the variation in colony-forming unit density. Colony-forming units and ≥10 um particle density increased with longer surgery duration and higher staff counts.

This is the first study to the authors knowledge that shows a correlation between the number of persons in the OR and CFUs at the surgical site during total joint arthroplasty procedures. Increasing surgical staff appear to produce both more particulate and more CFUs. These observations support the use of environmental controls that isolate and protect the surgical site from airborne particulate and microbial contamination.

Continuous monitering of particulate larger than 10 um during joint arthroplasty procedures may be warrented.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_I | Pages 187 - 187
1 Mar 2010
Noble P Schroder S Ellis A Thompson M Usrey M Holden J Stocks G
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Introduction: Femoro-acetabular impingement (FAI) is a common source of impaired motion of the hip, often attributed to the presence of an aspherical femoral head and reduced concavity of the anterior head/neck junction. However, other types of femoral deformity, including posterior slip, retroversion, and neck enlargement, can also limit hip motion. This study was performed to establish whether the “cam” impinging femur is a unique entity with a single deformity of the head/neck junction or is part of a multi-component continuum of femoral dysmorphia.

Materials and Methods: Computer models of 71 femora (28 normal and 43 “cam” impinging) were prepared from CT scans. Morphologic parameters describing the shape and dimensions of the head, neck, and medullary canal were calculated for each specimen. The anteversion angle, alpha angle of Notzli, beta angle of Beaulé, and normalized anterior heads offset were also calculated. Average dimensions were compared between the normal and impinging femora. A dimensionless model of the femoral neck was also generated to determine whether there is an inherent difference in the shape of the femoral neck in cam impinging and normal femora, independent of any differences in specimen size.

Results: Compared to the normal controls, the impinging femora had wider necks (AP: 15.2 vs 13.3 mm, p< 0.0001), larger heads (diameter: 48.3mm vs 46.0mm, p=0.032) and decreased head/neck ratios (1.60 vs 1.74, p=0.0002). However, there was no difference in neck/shaft angle (125.7° vs 126.5°, p=0.582) or anteversion angle (8.70 vs 8.44°, p=0.866). Most significantly, 53% of impinging femora also had a significant posterior slip (> 2mm), compared to only 14% of normal controls. Average head displacements for the two groups were: FAI: 1.93mm vs Normals: 0.78mm (p< 0.0001). Shape indices derived from individual dimensionless models showed slight AP widening of the abnormal femora (ap/ml ratio: 1.10 abnormal vs. 1.07 normal).

Conclusions: The CAM impinging femur has many abnormalities apart from the morphology of the head/neck junction. These femora have increased neck width and head/neck ratio, a smaller spherical bearing surface, and reduced neck offset from the medullary canal. Moreover, the presence of posterior head displacement and reduced anteversion should be appreciated when assessing treatment options, as surgical treatment limited to localized re-contouring of the head–neck profile may fail to address significant components of the underlying abnormality.


The Journal of Bone & Joint Surgery British Volume
Vol. 77-B, Issue 6 | Pages 853 - 861
1 Nov 1995
Stocks G Freeman M Evans S

We measured the proximal migration of 265 acetabular cups over seven years and correlated the findings with clinical outcome and acetabular revision for aseptic loosening. Cups which eventually became aseptically loose were shown to migrate more rapidly than successful cups. The average proximal migration at two years postoperatively for four groups of cups showed a monotonic relationship to the acetabular revision rate for aseptic loosening at 6.5 years. We conclude that acetabular cups which develop aseptic loosening as evidenced by pain, revision or screw fracture show increased proximal migration by one year, and that the 'migration rate' at two years can be used to predict the acetabular revision rate from aseptic loosening at 6.5 years.