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Clifford W Colwell

Publications and source records attributed to Clifford W Colwell.

At least 37 records · Page 2Linked to original sources
PubMed2005

Patient compliance with outpatient prophylaxis: an observational study.

The need for prophylaxis against venous thromboembolic disease following lower-extremity joint replacement is well documented and accepted. Although low molecular weight heparin is approved for inpatient and extended prophylaxis beyond the hospital environment, orthopedic surgeons must determine the duration of injectable low molecular weight heparin based on the period of venous thromboembolic disease risk and on patient compliance with self-administration of medication at home. Lack of confidence in patients' ability to self-administer injections may contribute to hesitancy in prescribing injectable prophylaxis. This observational study evaluated the effectiveness of a self-injection education program. Findings demonstrate that when properly instructed, patients safely and efficaciously self-administer low molecular weight heparin at home. With shorter hospital stays, self-administration of low molecular weight heparin may optimize the clinical outcomes of orthopedic patients.

Adult↗
PubMed2004

Efficacy of fondaparinux for thromboprophylaxis in hip fracture patients.

Fondaparinux efficacy for thromboprophylaxis was evaluated in predefined high-risk hip fracture patients. Patients received fondaparinux 2.5 mg for 7 days following surgery; 656 patients were randomized double blind to receive placebo or continue fondaparinux regimen for 21 additional days. Primary efficacy was venous thromboembolism (VTE) based on bilateral venography during the double-blind period. Total VTE was 1.4% (3 of 208 patients) for extended prophylaxis and 35% (77 of 220 patients) for short-term prophylaxis (P = 0.001), relative risk reduction (RRR) of 96%. Major bleeding occurred in 2% (8 of 327 patients) with extended prophylaxis and in 0.6% (2 of 329 patients) with short-term prophylaxis (P =.063). Risk of VTE was continued following short course fondaparinux in hip fracture patients, but was significantly reduced by extending prophylaxis, without significant risk of major bleeding.

Aged↗
PubMed2004

Two-dose epoetin alfa reduces blood transfusions compared with autologous donation.

This study evaluated whether patients receiving a two-dose regime of epoetin alfa received less allogeneic blood than patients donating autologous blood before primary hip arthroplasty. Consenting patients with a hemoglobin level between 12 and 15 g/dL were randomly assigned to a two-dose administration of epoetin alfa (19 patients) or autologous donation (21 patients). Sixteen percent of the patients in the epoetin alfa group and 52% of the patients in the autologous donation group received transfusions, with a mean volume of 90 cc per patient in the epoetin alfa group and 340 cc in the autologous donation group. Hemoglobin was similar at screening; however, the epoetin alfa group achieved a higher hemoglobin (14.6 g/dL) than the autologous donation group (12.6 g/dL) before surgery. Hemoglobin remained significantly higher in the epoetin alfa group for 3 days after surgery. Administration of two doses of epoetin alfa provided patients with effective and safe reduction of allogeneic blood transfusions and decreased the necessity and difficulty of autologous donation before total hip arthroplasty.

Adolescent↗
PubMed2004

Oxidized zirconium femoral components reduce polyethylene wear in a knee wear simulator.

Polyethylene wear remains a major problem that can jeopardize the long-term durability of prostheses used in total knee arthroplasty. Oxidized zirconium is a material that combines the strength of a metal with the wear properties of a ceramic. This study evaluated the wear rates of polyethylene inserts against oxidized zirconium femoral components. Three oxidized zirconium femoral components and three Co-Cr femoral components of identical geometry used in total knee arthroplasty were articulated against standard tibial components with modular tibial inserts made of noncross-linked ultra-high molecular weight polyethylene. Gravimetric and volumetric polyethylene wear rates were calculated after 5 million gait cycles on an AMTI knee wear simulator. Oxidized zirconium reduced polyethylene wear by 42% compared with Co-Cr alloy. This study shows that oxidized zirconium can reduce polyethylene wear substantially when used for fixed-bearing total knee arthroplasty.

Biocompatible Materials↗
PubMed2004

Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.

This article discusses the prevention of venous thromboembolism (VTE) and is part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following. We recommend against the use of aspirin alone as thromboprophylaxis for any patient group (Grade 1A). For moderate-risk general surgery patients, we recommend prophylaxis with low-dose unfractionated heparin (LDUH) (5,000 U bid) or low-molecular-weight heparin (LMWH) [< or = 3,400 U once daily] (both Grade 1A). For higher risk general surgery patients, we recommend thromboprophylaxis with LDUH (5,000 U tid) or LMWH (> 3,400 U daily) [both Grade 1A]. For high-risk general surgery patients with multiple risk factors, we recommend combining pharmacologic methods (LDUH three times daily or LMWH, > 3,400 U daily) with the use of graduated compression stockings and/or intermittent pneumatic compression devices (Grade 1C+). We recommend that thromboprophylaxis be used in all patients undergoing major gynecologic surgery (Grade 1A) or major, open urologic procedures, and we recommend prophylaxis with LDUH two times or three times daily (Grade 1A). For patients undergoing elective total hip or knee arthroplasty, we recommend one of the following three anticoagulant agents: LMWH, fondaparinux, or adjusted-dose vitamin K antagonist (VKA) [international normalized ratio (INR) target, 2.5; range, 2.0 to 3.0] (all Grade 1A). For patients undergoing hip fracture surgery (HFS), we recommend the routine use of fondaparinux (Grade 1A), LMWH (Grade 1C+), VKA (target INR, 2.5; range, 2.0 to 3.0) [Grade 2B], or LDUH (Grade 1B). We recommend that patients undergoing hip or knee arthroplasty, or HFS receive thromboprophylaxis for at least 10 days (Grade 1A). We recommend that all trauma patients with at least one risk factor for VTE receive thromboprophylaxis (Grade 1A). In acutely ill medical patients who have been admitted to the hospital with congestive heart failure or severe respiratory disease, or who are confined to bed and have one or more additional risk factors, we recommend prophylaxis with LDUH (Grade 1A) or LMWH (Grade 1A). We recommend, on admission to the intensive care unit, all patients be assessed for their risk of VTE. Accordingly, most patients should receive thromboprophylaxis (Grade 1A).

Anticoagulants↗
PubMed2004

The efficacy of a single daily dose of enoxaparin for deep vein thrombosis prophylaxis following total knee arthroplasty.

Deep vein thrombosis (DVT) is a major risk following total knee arthroplasty (TKA). This prospective outcomes study evaluates the efficacy of enoxaparin 40 mg once daily for 7 days after TKA, by documenting symptomatic and asymptomatic outcomes using bilateral lower extremity duplex ultrasound upon hospital discharge and on postoperative day 21 (+/-2). In 60 extremities, duplex ultrasound demonstrated a DVT prevalence of 16.7% (10) on the day of discharge and of 11.7% (7) on postoperative day 21. No new DVT or propagation of distal to proximal DVT were noted. For this small cohort, enoxaparin 40 mg daily demonstrates effective prophylaxis for DVT in TKA patients.

Adult↗
PubMed2004

The use of the pain pump and patient-controlled analgesia in joint reconstruction.

Controlling postoperative pain following painful orthopedic procedures such as total knee arthroplasty is an ongoing challenge, as current pain management techniques often result in undermedication and/or complications. Traditional pain management strategies include opioid analgesics administered orally or via epidural catheter, patient-controlled analgesia (PCA), or intramuscular (IM) injection. This article discusses the use of PCA and the pain pump as effective modalities for the management of pain after arthroplasty. While the use of PCA has been somewhat controversial, a review of the literature supports its use over traditional IM dosing. PCA has been shown to provide more effective analgesia than IM dosing, and PCA administration is preferred over IM dosing by both patients and nurses. Continuous infusion of bupivacaine via pain pump is also an effective modality for reducing postoperative pain and decreasing postoperative consumption of opioid analgesics.

Analgesia, Patient-Controlled↗
PubMed2004

Advances in DVT prophylaxis and management in major orthopaedic surgery.

Every year, approximately 2 million people experience a deep venous thrombosis (DVT). Approximately 600,000 of these people are diagnosed with a pulmonary embolism and about 10% of these die. It has been established that surgery, anesthesia, and bed rest increase the risk of DVT, and therefore, patients who undergo a major lower-extremity procedure should receive prophylaxis. During the past 10 years, the choices of pharmacological and mechanical prophylaxis have increased greatly. Warfarin is probably the most widely used prophylactic method in the U.S., but low-molecular-weight heparin (LMWH) use has increased. Also available is a synthetic pentasaccharide that acts as an anti-Xa inhibitor to decrease DVT without increase in bleeding. All but warfarin are given by subcutaneous injection and require no laboratory management to adjust the medication. Another drug in clinical trials is a direct thrombin inhibitor taken orally in a fixed dose that does not require monitoring. Non-pharmacological prophylaxis and/or stacked modalities, although used, have not shown the efficacy of pharmacological prophylaxis. With the incidence of DVT reported in the range of 41% to 85% without prophylaxis in joint replacement and hip-fracture surgery, prophylaxis is warranted in all lower-extremity joint replacement and hip-fracture patients.

Anticoagulants↗
PubMed2003

Comparison of ximelagatran with warfarin for the prevention of venous thromboembolism after total knee replacement.

BACKGROUND: In a previous study of the prevention of venous thromboembolism after total knee replacement, the efficacy of ximelagatran, an oral direct thrombin inhibitor that does not require monitoring of coagulation or dose adjustment, was found to be similar to that of warfarin at a dose of 24 mg of ximelagatran twice daily. The purpose of the present study was to determine whether a higher dose of ximelagatran is superior to warfarin. METHODS: This randomized, double-blind trial compared a regimen of 7 to 12 days of oral ximelagatran, at a dose of 24 or 36 mg twice daily, starting the morning after surgery, with warfarin therapy started the evening of the day of surgery. The composite end point of venous thromboembolism and death from all causes and the incidence of bleeding were the primary outcome measures. RESULTS: Among the 1851 patients in the efficacy analysis, oral ximelagatran at a dose of 36 mg twice daily was superior to warfarin with respect to the primary composite end point of venous thromboembolism and death from all causes (20.3 percent vs. 27.6 percent; P=0.003). There were no significant differences between these two groups with respect to major bleeding (incidence, 0.8 percent and 0.7 percent, respectively), perioperative indicators of bleeding, wound characteristics, or the composite secondary end point of proximal deep-vein thrombosis, pulmonary embolism, and death (2.7 percent vs. 4.1 percent; P=0.17). CONCLUSIONS: The efficacy of oral ximelagatran, administered starting the morning after total knee replacement, was superior to that of warfarin for prevention of venous thromboembolism. Rates of hemorrhagic complications with the two drugs were similar.

Administration, Oral↗
PubMed2003

Polyethylene cross-linking by two different methods reduces acetabular liner wear in a hip joint wear simulator.

Advances in cross-linking have led to the development of wear resistant ultrahigh molecular weight polyethylene for total joint replacement. This study compared wear reduction by two different cross-linking methods as measured in a hip wear simulator. One highly cross-linked polyethylene was treated with 7.5 Mrad gamma irradiation with post-irradiation annealing and a sterilization dose of 2.5 Mrad (10 Gamma), while the other used 9.5 Mrad warm irradiation with 10 MeV electron-beam (9.5 EB). Liners of the same design, made from nominally cross-linked (gamma sterilized) polyethylene were also tested. Gravimetric wear analysis was performed every 500,000 cycles for 5,000,000 cycles. After correcting for weight gain due to water absorption, the nominally cross-linked liners demonstrated mean wear rates of 15.7 (+/-1.7) and 12.5 (+/-1.0) mg/million cycles. Both highly cross-linked polyethylene liners demonstrated significantly less wear than their respective controls (with mean wear rates of 1.5 (+/-1.2) and -1.4 (+/-1.5) mg/million cycles). The 9.5 EB liners gained weight presumably due to increased fluid absorption, in addition to that measured in loaded-soaked control implants. Any wear occurring was therefore assumed to have been more than offset by weight gain. Highly cross-linked polyethylene was significantly more wear resistant than non- or nominally cross-linked polyethylene. The differences in wear rates between the two highly cross-linked polyethylene designs (9.5 EB or 10 Gamma) are probably too small to be clinically significant.

Acetabulum↗
PubMed2003

Polyethylene wear and acetabular component orientation.

BACKGROUND: Polyethylene wear contributes substantially to both periprosthetic osteolysis and aseptic loosening after total hip arthroplasty. Acetabular component orientation has been shown to affect the range of motion of the hip as well as contact stresses. A series of studies was designed to test the hypothesis that acetabular component orientation can affect the magnitude and direction of polyethylene wear. METHODS: A finite-element model was used to compute contact stresses during a normal gait cycle. Wear at the end of each gait cycle was calculated with use of the sliding-distance-coupled finite-element formulation. The wear that was calculated with use of finite-element analysis was validated by comparison with the findings of hip wear simulator studies with the acetabular liner oriented to simulate 45 degrees and 55 degrees of abduction. In a clinical study, fifty-six patients who underwent sixty hip arthroplasties with use of a single prosthetic design were followed for as long as five years. Radiographs were analyzed to measure the abduction angle of the acetabular component and polyethylene wear. RESULTS: The finite-element analysis predicted increased peak contact stresses with an increased abduction angle and reduced peak contact stresses with an increased anteversion angle. Linear wear rates ranging from 0.036 to 0.045 mm/million cycles were also predicted, and increased acetabular abduction angles were predicted to be associated with higher linear wear rates. In the hip wear simulator studies, significantly different wear rates were found between the cups with acetabular abduction angles of 45 degrees and 55 degrees (mean, 17.2 compared with 21.7 mg/million cycles; p < 0.01). In the clinical study, radiographic analysis revealed significant correlation between the acetabular abduction angle and the linear polyethylene wear rate. A 40% increase in mean linear polyethylene wear was seen in cups with an abduction angle of >or=45 degrees. The direction of wear was more medial (by 9.4 degrees ) in cups with an abduction angle of <45 degrees. CONCLUSION: All three studies presented here underlined the importance of optimizing the position of the acetabular component. Careful attention to acetabular position may help to minimize wear.

Aged↗
PubMed2003

Impact of patellofemoral design on patellofemoral forces and polyethylene stresses.

BACKGROUND: The patellofemoral joint is a complex articulation because it relies mainly on soft-tissue constraints for stable tracking. The presence of a functioning posterior cruciate ligament and the design parameters of a total knee arthroplasty, such as trochlear groove alignment and cam-post configuration, can have a major effect on patellar biomechanics. METHODS: A finite element model of a knee implanted with femoral, tibial, and patellar components was generated. The model was validated by experimental testing of three cadaver knees implanted with a total knee prosthesis and a patellar force transducer. Two femoral component designs with different valgus angles of the trochlear groove (0 degrees and 7 degrees ) were studied. The effects of femoral rollback, rotation of the femoral component, medialization of the patellar implant, and alignment of the trochlear groove on patellar forces were then analyzed. RESULTS: A consistent reduction of up to 7% in patellofemoral forces was seen with progressive magnitudes of femoral rollback. The 0 degrees -aligned trochlear groove generated some lateral patellofemoral shear force throughout knee flexion. The 7 degrees -aligned trochlear groove generated medial shear force at flexion angles of <20 degrees and lateral shear force at flexion angles of >20 degrees. A more medial patellar component position reduced peak lateral shear forces by up to 10 to 15 N. However, a corresponding increase in medial shear forces was seen. CONCLUSIONS: This model predicted substantial reduction in patellofemoral lateral shear forces with a medialized patellar component or with external rotation of the femur. The model supported the hypothesis that femoral rollback reduces patellofemoral forces by improving the efficiency of the extensor mechanism. CLINICAL RELEVANCE: Patellofemoral complications after total knee arthroplasty include anterior knee pain, patellar subluxation and dislocation, abnormal polyethylene wear and damage, and loosening. There is a wide variation in the design features of current total knee prostheses, such as the sagittal radius, depth, and orientation of the trochlear groove of the femur and the geometry of the patellar component surface. The finite element model used in the present study can provide insight into the effects of design parameters on patellofemoral forces and on local contact stresses.

Arthroplasty, Replacement, Knee↗
PubMed2003

Comparison of the wear rates of twenty-eight and thirty-two-millimeter femoral heads on cross-linked polyethylene acetabular cups in a wear simulator.

BACKGROUND: The use of larger femoral head sizes in total hip arthroplasty has been shown to reduce the rate of dislocation and to increase the range of motion; however, such components have been associated with unacceptably high polyethylene wear rates. Studies have shown dramatic differences in wear rates between nominally cross-linked polyethylene (i.e., polyethylene that is cross-linked during radiation sterilization) and elevated cross-linked polyethylene (i.e., polyethylene that is cross-linked to a higher degree than that obtained by radiation sterilization alone). The aim of this study was to test the effect of increased cross-linking and of increased head size on polyethylene wear rates. METHODS: Four groups of acetabular liners obtained from a single manufacturer, including 28-mm-diameter nominally cross-linked, 32-mm-diameter nominally cross-linked, 28-mm-diameter elevated cross-linked, and 32-mm-diameter elevated cross-linked polyethylene liners, were tested. Three implants from each group were tested in a twelve-station hip wear simulator with use of 90% bovine serum as a lubricant. The liners were articulated with the appropriately sized cobalt-chromium femoral head. Additional liners from each design were subjected only to the same load without motion to serve as load-soak controls to account for any weight gain due to fluid absorption. Gravimetric analysis was performed every 500,000 cycles for a total of five million cycles. RESULTS: Nominally cross-linked liners demonstrated mean wear rates of 14.97 and 16.92 mg per million cycles for the 28-mm and 32-mm head sizes, respectively. Both of the elevated cross-linked liners had significantly lower wear rates than the nominally cross-linked liners, with a mean of 1.51 and 2.57 mg per million cycles for the 28-mm and 32-mm head sizes, respectively (p < 0.001). CONCLUSION: The dramatic reduction in wear rates with polyethylene cross-linking, even with the larger head size, may increase the potential for use of 32-mm head components in total hip arthroplasty.

Acetabulum↗
PubMed2003

Managing thromboembolic risk in hip and knee arthroplasty: state of the art.

Deep vein thrombosis and pulmonary embolism are major causes of morbidity and mortality after knee and hip arthroplasty in the United States. Although patients frequently receive prophylaxis for thromboembolism postarthroplasty, surgeons vary in their choice of modality and often use suboptimal strategies due to the possibility of provoking postoperative bleeding. This article discusses the rationale for the prevention of venous thromboembolism and offers an overview of clinical recommendations for prophylaxis in knee and hip replacement surgery. Supporting medical evidence for these recommendations is described. A summary of current prophylactic regimens and discussion of duration of therapy are also presented.

Arthroplasty, Replacement, Hip↗
PubMed2003

Blood conservation in primary total hip arthroplasty.

Total hip arthroplasty is characterized by significant blood loss. The principal aim of blood management in joint replacement surgery is to minimize both the risks associated with surgical blood loss and the risks associated with allogenic blood transfusion. In the 1980s, the AIDS epidemic triggered the development of a variety of innovative approaches to conserving blood and reducing the need for allogenic transfusion to replace surgical blood loss. Subsequently, the safety of the blood supply was dramatically improved, changes in surgical technique led to decreased surgical blood loss, and changes in transfusion thresholds made the need for transfusion less common. The review re-examines the options available for the management of blood loss in total joint replacement and defines parameters that can be used preoperatively to predict which patients are likely to benefit from these interventions, given the clinical realities of the 21st century.

Arthroplasty, Replacement, Hip↗
PubMed2002

Ximelagatran versus warfarin for the prevention of venous thromboembolism after total knee arthroplasty. A randomized, double-blind trial.

BACKGROUND: Warfarin is used for prophylaxis of venous thromboembolism in patients undergoing total knee arthroplasty. However, it is associated with rates of deep venous thrombosis (DVT) of approximately 38% to 55% and requires routine coagulation monitoring and frequent dose adjustment. Ximelagatran, an oral direct thrombin inhibitor, has shown promising efficacy and tolerability in patients undergoing total hip or knee arthroplasty. OBJECTIVE: To compare the efficacy and safety of ximelagatran and warfarin for prophylaxis of venous thromboembolism after total knee arthroplasty. DESIGN: Randomized, double-blind, parallel-group trial. SETTING: 74 North American hospitals. PATIENTS: 680 patients who had undergone total knee arthroplasty. INTERVENTION: 7 to 12 days of treatment with oral ximelagatran, 24 mg twice daily, starting on the morning after surgery, or warfarin (target international normalized ratio, 2.5 [range, 1.8 to 3.0]), starting on the evening of the day of surgery. MEASUREMENTS: Principal end points were asymptomatic DVT on mandatory venography; symptomatic DVT confirmed by ultrasonography or venography; symptomatic, objectively proven pulmonary embolism; and bleeding. All were assessed by blinded adjudication locally and at a central study laboratory. RESULTS: On central adjudication, incidence of venous thromboembolism was 19.2% (53 of 276 patients) in the ximelagatran group and 25.7% (67 of 261 patients) in the warfarin group (difference, -6.5 percentage points [95% CI, -13.5 to 0.6 percentage points]; P = 0.070). On local assessment, incidence was 25.4% in the ximelagatran group and 33.5% in the warfarin group (P = 0.043). In the ximelagatran and warfarin groups, respectively, major bleeding occurred in 1.7% and 0.9% of patients and minor bleeding occurred in 7.8% and 6.4% of patients. No variables related to bleeding differed significantly between the two groups. CONCLUSIONS: For prophylaxis of venous thromboembolism, fixed-dose ximelagatran started the morning after total knee arthroplasty is well tolerated and at least as effective as warfarin, but it does not require coagulation monitoring or dose adjustment.

Administration, Oral↗