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Biomedical subjects

Clifford W Colwell

Publications and source records attributed to Clifford W Colwell.

At least 19 recordsLinked to original sources
PubMed2007

Press-fit condylar design total knee arthroplasty. Fourteen to seventeen-year follow-up.

BACKGROUND: The Press-Fit Condylar total knee arthroplasty implant design has been used by many orthopaedic surgeons over the last twenty years. The design has survived with relatively minor modifications and remains a popular implant system today. The present study represents the fourteen to seventeen-year results for our patients who were described in our previous report on the eight to ten-year results. METHODS: The senior author performed 160 consecutive total knee arthroplasties with use of the Press-Fit Condylar cruciate-retaining device in 134 patients between 1986 and 1989. The mean age of the patients at the time of the index procedure was 70.5 years. Follow-up data were available for sixty-three of sixty-four surviving knees. Surviving patients were followed for a mean of 15.8 years. The knees were evaluated on the basis of Knee Society function and clinical scores, radiographs, and survivorship analysis. RESULTS: The mean Knee Society function score was 65, and the mean clinical score was 89. The overall survival rate of the knee was 91.5% with revision for any reason as the end point and 97.2% with aseptic loosening as the end point. The rate of revision of the tibial insert because of wear-related aseptic loosening was 2.5%. We found no relationship between revision and the shelf life or method of sterilization of the polyethylene insert. Radiolucent lines were present in 62% (twenty-one) of thirty-four knees; all radiolucent lines were nonprogressive. None of the implants were loose according to the criteria of the Knee Society. CONCLUSIONS: This long-term analysis indicates that the Press-Fit Condylar total knee implant is a successful implant system with excellent longevity.

Aged↗
PubMed2006

Flexibility in administration of fondaparinux for prevention of symptomatic venous thromboembolism in orthopaedic surgery.

Venous thromboembolism (VTE) is a common complication of total joint arthroplasty. Fondaparinux VTE prophylaxis is currently begun 6 to 8 hours after surgery. Flexible dosing may reduce bleeding risk and allow easier use by starting the morning after surgery instead of staggered hours on the surgery day. This study examined flexible timing of the first dose of fondaparinux. Whether the first dose was administered 8 +/- 2 hours after surgery or the morning after surgery, no significant difference was observed in incidence of symptomatic VTE (2.0% and 1.9%, respectively, P = .89). Major and minor bleeding events were similar between groups (1.2% and 0.7% [P = .19], and 1.4% and 2.0% [P = .31], respectively). Delaying initiation of fondaparinux prophylaxis provides an option after total joint arthroplasty with preserved efficacy and safety.

Aged↗
PubMed2006

Tibial forces measured in vivo after total knee arthroplasty.

An instrumented tibial prosthesis was developed to measure forces in vivo after total tibial arthroplasty. This prosthesis was implanted in a 67-kg, 80-year-old man. The prosthesis measured forces at the 4 quadrants of the tibial tray. Tibial forces were measured postoperatively during rehabilitation, rising from a chair, standing, walking, and climbing stairs. By the sixth postoperative week, the peak tibial forces during walking averaged 2.2 times body weight (BW). Stair climbing increased from 1.9 times BW on day 6 to 2.5 times BW at 6 weeks. This represents the first direct in vivo measurement of tibial forces, which should lead to refined surgical techniques and enhanced prosthetic designs. Technical design improvements will enhance function, quality of life, and longevity of total knee arthroplasty.

Aged, 80 and over↗
PubMed2006

Bilateral vs unilateral total knee arthroplasty: a patient-based comparison of pain levels and recovery of ambulatory skills.

Two important questions remain in simultaneous bilateral total knee arthroplasty (TKA). Is bilateral TKA significantly more painful and is physical recovery significantly more difficult compared with unilateral TKA? A retrospective matched-pair analysis compared 59 bilateral and 59 unilateral TKA patients based on age, sex, diagnosis, surgeon, and surgery date. Analog pain scores, narcotic use, ambulatory distances, and rehabilitative milestones were recorded. Bilateral patients' pain scores were 1 point higher during day 1 with subsequent equal scores. Narcotic use was 20% higher for the first 48 hours but equalized after that period. Ambulatory milestones lagged behind by 36 hours. Patients wishing to pursue bilateral TKA can proceed without pain, use of narcotics, and walking distance significantly different than unilateral TKA.

Activities of Daily Living↗
PubMed2006

A multiaxial force-sensing implantable tibial prosthesis.

Accurate in vivo measurement of tibiofemoral forces is important in total knee arthroplasty. These forces determine polyethylene stresses and cold-flow, stress distribution in the implant, and stress transfer to the underlying implant bone interface. Theoretic estimates of tibiofemoral forces have varied widely depending on the mathematical models used. The six degrees of freedom of motion, complex articular surface topography, changing joint-contact position, intra- and extra-articular ligaments, number of muscles crossing the knee joint, and the presence of the patellofemoral joint contribute to the difficulty in developing reliable models of the knee. A prototype instrumented total knee replacement tibial prosthesis was designed, manufactured, and tested. This prosthesis accurately measured all six components of tibial forces (R2>0.997). The prosthesis was also instrumented with an internal microtransmitter for wireless data transmission. Remote powering of the sealed implanted electronics was achieved using magnetic coil induction. This device can be used to validate existing models of the knee that estimate these forces or to develop more accurate models. In conjunction with kinematic data, accurate tibiofemoral force data may be used to design more effective knee-testing rigs and wear simulators. Additional uses are intraoperative measurement of forces to determine soft-tissue balancing and to evaluate the effects of rehabilitation, external bracing, and athletic activities, and activities of daily living.

Humans↗
PubMed2006

Rationale for low-molecular-weight heparin prophylaxis after total knee arthroplasty.

Low-molecular-weight heparin has been studied extensively in total knee arthroplasty (TKA) and provides highly effective and safe prophylaxis against deep venous thrombosis (DVT). Low-molecular-weight heparin received the highest rating (A1) in the American College of Chest Physicians recommendations for DVT prophylaxis after elective TKA. Prevalence of DVT with low-molecular-weight heparin prophylaxis was 33% in TKA data pooled from six randomized studies, with a proximal DVT rate of 7.1%. A metaanalysis reported a 2.4% rate of major bleeding with low-molecular-weight heparin. Low-molecular-weight heparin, given by subcutaneous injection, can be started before surgery or after surgery. A synthetic pentasaccharide (fondaparinux), which received an A1 rating in the American College of Chest Physicians recommendations, also is available. As with all treatments, the benefit must be considered against the risk when using these anticoagulants.

Arthroplasty, Replacement, Knee↗
PubMed2006

Highly cross-linked polyethylene in total hip arthroplasty.

Although total hip arthroplasty is a common and highly successful procedure, its long-term durability has been undermined by the cellular response to polyethylene wear debris and the subsequent effects on periprosthetic bone. Research elucidating the effects of sterilization on polyethylene wear has facilitated the development of a more wear-resistant material-highly cross-linked polyethylene. Laboratory testing has demonstrated that highly cross-linked polyethylene has markedly improved wear resistance compared with conventional polyethylene under a variety of conditions. Early clinical data have supported these results. To make informed decisions about this already widely available and frequently used product, the practicing orthopaedic surgeon should have a basic understanding of the production process as well as knowledge of the most current laboratory and clinical data.

Arthroplasty, Replacement, Hip↗
PubMed2006

Thromboprophylaxis in orthopedic surgery.

More than 2 million people undergo major orthopedic surgery each year, and this rate is expected to continue rising as our population ages. Our patients are at particularly high risk for deep vein thrombosis (DVT) and pulmonary embolism. The latest guidelines from the American College of Chest Physicians recommend thromboprophylaxis for high-risk orthopedic surgery patients. Although specific recommendations vary by type of surgery, low-molecular-weight heparin, fondaparinux, warfarin, and sometimes low-dose unfractionated heparin are effective alone or with mechanical prophylaxis. Goals of treatment are to prevent proximal and distal DVT, pulmonary death, chronic pulmonary hypertension, and postthrombotic syndrome.

Anesthesia, Epidural↗
PubMed2005

Hydroxyapatite-coated femoral stem survivorship at 10 years.

Ninety-six patients were implanted with the Omnifit-HA femoral stem and the Omnifit-PSL porous-coated dual-radius acetabular shell (Stryker, Mahwah, NJ) and liners that were sterilized by gamma-radiation in air. The mean age at the time of surgery was 52 years (range, 27-78 years), and male/female ratio was 54:42. The mean follow-up was 10.3 years (range, 7-12 years). The survivorship of the stem and cup was 100% and 90%, respectively. Four cups were revised for aseptic loosening, and 6 liners were exchanged. The mean polyethylene wear rate was 0.24 mm/y. Lysis was noted in 23% of the cups. No patient developed femoral lysis distally. This hydroxyapatite-coated stem continues to perform well and appears to protect against the migration of wear debris along the femoral stem.

Adult↗
PubMed2005

An implantable telemetry device to measure intra-articular tibial forces.

Tibial forces are important because they determine polyethylene wear, stress distribution in the implant, and stress transfer to underlying bone. Theoretic estimates of tibiofemoral forces have varied between three and six times the body weight depending on the mathematical models used and the type of activity analyzed. An implantable telemetry system was therefore developed to directly measure tibiofemoral compressive forces. This system was tested in a cadaver knee in a dynamic knee rig. A total knee tibial arthroplasty prosthesis was instrumented with four force transducers located at the four corners of the tibial tray. These transducers measured the total compressive forces on the tibial tray and the location of the center of pressure. A microprocessor performed analog-to-digital signal conversion and performed pulse code modulation of a surface acoustic wave radio frequency oscillator. This signal was then transmitted through a single pin hermetic feed-through tantalum wire antenna located at the tip of the stem. The radio frequency signal was received by an external antenna connected to a receiver and to a computer for data acquisition. The prosthesis was powered by external coil induction. The tibial transducer accurately measured both the magnitude and the location of precisely applied external loads. Successful transmission of the radio frequency signal up to a range of 3m was achieved through cadaveric bone, bone cement, and soft tissue. Reasonable accuracy was obtained in measuring loads applied through a polyethylene insert. The implant was also able to detect unicondylar loading with liftoff.

Cadaver↗
PubMed2005

Patellofemoral forces after total knee arthroplasty: effect of extensor moment arm.

Total knee arthroplasty implant designs with larger extensor moment arms theoretically should generate lower extensor forces for the same externally applied loads. This study measured knee kinematics, quadriceps forces, and patellofemoral forces under conditions of dynamic knee extension under load in two knee designs with differing quadriceps moment arms. Six human cadaver knees were tested both before implantation and after sequential implantation with two posterior cruciate retaining designs. The extensor moment arm of the LMA (long extensor moment arm design, Scorpio, Howmedica Osteonics, Rutherford, NJ) was approximately 1 cm longer than that of the Control design (7000, Howmedica Osteonics). Quadriceps tension was measured during dynamic closed kinetic chain knee extension. Patellar compressive and shear forces were also recorded using a patellar component instrumented with a custom triaxial load transducer. Knee kinematics were monitored using a three-dimensional electromagnetic tracking device. Both designs produced similar patterns of femoral rollback and tibial rotation. Quadriceps tension was lower in the LMA design compared with the Control design. Patellofemoral compressive forces were also significantly reduced in the LMA design when compared with Control (8-18% lower at angles greater than 50 degrees flexion). The design with the longer extensor moment arm required less quadriceps force to extend the knee under load and reduced patellofemoral compressive forces. Reduced quadriceps forces may facilitate postoperative rehabilitation and activities such as stair climbing. Reduction in patellofemoral forces could reduce patellar complications such as anterior knee pain, component wear, and loosening.

Arthroplasty, Replacement, Knee↗
PubMed2005

The Chitranjan Ranawat Award: in vivo knee forces after total knee arthroplasty.

Tibial forces were measured in vivo during the first year after total knee arthroplasty in a 66 kg, 80-year-old man. Forces were measured during activities of daily living, rehabilitation, and exercise. Peak tibial forces recorded during walking increased up to 12 months postoperatively (2.8 times body weight). Tibial forces correlated with increasing speed during treadmill walking. Rising from a chair generated peak forces of 2.6 times body weight. Stair descent generated higher peak forces than stair ascent (3.3 versus 2.9 times body weight, respectively). Exercising on a stair-climbing machine generated forces close to two times body weight whereas stationary bicycling generated even lower forces, near one times body weight. In general, the tibial forces recorded during walking and stair climbing were lower than most predicted values. These measurements can be used to validate in vitro and mathematical models of the knee. This should lead to refined surgical techniques and to enhanced prosthetic designs that will improve patient function, patient quality of life, and longevity of total knee arthroplasty implants.

Aged, 80 and over↗
PubMed2005

Outcome of an acetabular design with hydroxyapatite coating on a rough substrate.

UNLABELLED: Outcomes of hydroxyapatite-coated cups have not been as consistently successful as outcomes of hydroxyapatite-coated stems; therefore, we studied a newer generation acetabular design with a plasma-sprayed hydroxyapatite coating on an arc-deposited rough titanium substrate. Our objective was to determine whether clinical and radiographic outcomes would be better than reported for earlier-generation designs. Ninety consecutive hips in 85 patients implanted with this design were followed up prospectively for 2 to 5 years after surgery. Hip scores improved from a preoperative mean of 59 (+/- 12) to final followup mean of 91 (+/- 12). One hip was revised for recurrent dislocation. No hips were revised for aseptic loosening. No cup had complete continuous radiolucent lines. Incomplete lucent lines were noted on early postoperative radiographs. With followup, radiolucent line length decreased by a mean 32% and radiolucent line density increased by 9%. Mean polyethylene linear and volumetric head penetration rates were 0.17 (+/- 0.16) mm/year and 73 (+/- 70) mm/year, respectively. Head penetration rates were higher in men. No other factor (age, body weight, cup abduction, or anteversion angle) correlated with head penetration rate. Our study presents encouraging short-term results. Improvement in radiolucent lines suggests a beneficial effect of hydroxyapatite coating on osseointegration of the cup. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Acetabulum↗
PubMed2005

Fatal vascular outcomes following major orthopedic surgery.

Major orthopedic surgery is known to be associated with potentially serious arterial and venous vascular complications, although uncertainty exists about current event rates. Using electronic databases and investigator contact, we identified randomized and cohort studies reporting overall mortality and fatal vascular events. Where possible, studies reporting high autopsy rates (>60%) were examined. Pooled incidences were calculated from eligible studies. For Autopsy studies: Pooled overall mortality and fatal pulmonary embolism for patients undergoing elective hip and knee replacement without prophylaxis could not be calculated, while with prophylaxis they were 0.44% (95% confidence interval 0.02 to 0.87%) and 0.43% (0.01 to 0.85%). For patients undergoing hip fracture surgery, the corresponding rates without prophylaxis were 15.9% (14.5 to 17.3%) and 1.9% (1.4 to 2.4%). With prophylaxis, mortality and fatal pulmonary embolismrates were 8.5% (7.3 to 9.7%) and 1.0% (0.6 to 1.5%). Among Cohort studies: Pooled overall mortality and fatal pulmonary embolism for patients undergoing elective hip and knee replacement without prophylaxis were 0.93% (0.57 to 1.29%) and 0.36% (0.14 to 0.59%). For patients receiving prophylaxis (7 to 14 days), mortality and fatal pulmonary embolism were 0.57% (0.51 to 0.62%) and 0.18% (0.14 to 0.21%). Patients undergoing hip fracture surgery receiving prophylaxis hadmortality and fatal pulmonary embolismrates of 3.2% (2.8 to 3.6%) and 0.30% (0 to 0.61%). Vascular events contributed towards approximately 50% of all deaths with similar proportions due to ischemic heart disease, cardiac failure and pulmonary embolism. In conclusion, although prophylaxis results in a reduction in overall mortality and fatal pulmonary embolism, vascular events continue to be a common cause of mortality.

Autopsy↗
PubMed2005

Can normal knee kinematics be restored with unicompartmental knee replacement?

BACKGROUND: Unicompartmental replacement can be an alternative to tibial osteotomy in younger, active patients with unicompartmental knee disease. In unicompartmental replacement, the other compartments and knee ligaments are largely untouched. Therefore, it was hypothesized that the knee kinematics after unicompartmental replacement may also be unchanged. To test this hypothesis, knee kinematics and quadriceps tension were recorded before and after replacement with a unicompartmental design and then with a tricompartmental design. METHODS: Six human cadaver knees were tested before implantation, after implantation with a bicruciate-retaining unicompartmental knee prosthesis, and after implantation with a posterior cruciate-retaining tricompartmental knee prosthesis. The unicompartmental prosthesis was initially implanted, and it was then revised to a total condylar knee replacement. The knee kinematics were measured with use of an electromagnetic tracking device while the knee was put through dynamic simulated stair-climbing under peak flexion moments of approximately 40 N-m. Quadriceps tension was also measured for all three conditions. RESULTS: No significant differences in tibial axial rotation were noted between the intact and unicompartmental conditions. However, tricompartmental replacement significantly affected tibial axial rotation (p = 0.001). Femoral rollback was not significantly affected by either unicompartmental or tricompartmental arthroplasty. Quadriceps tension was also similar among all three conditions. CONCLUSIONS: In this in vitro cadaver study, the tricompartmental replacement significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.

Aged↗
PubMed2005

Oral direct thrombin inhibitor ximelagatran compared with warfarin for the prevention of venous thromboembolism after total knee arthroplasty.

BACKGROUND: Warfarin, which requires coagulation monitoring, is associated with relatively high rates of thromboembolism despite providing adequate prophylaxis. This study compared an oral direct thrombin inhibitor, ximelagatran, with warfarin in order to evaluate the safety and efficacy of the medication for the prevention of venous thromboembolism in patients undergoing total knee arthroplasty. METHODS: Following surgery, patients were randomly assigned to fixed-dose oral ximelagatran (36 mg twice daily) or warfarin (target international normalized ratio, 2.5), both administered for seven to twelve days in a double-blind, double-dummy design. Warfarin was initiated on the evening of the day of surgery, and ximelagatran, on the morning after surgery. The primary efficacy end point was the incidence of asymptomatic deep-vein thrombosis determined by bilateral venography, objectively confirmed symptomatic deep-vein thrombosis or pulmonary embolism, and death from all causes during treatment. RESULTS: Adequate venograms or confirmed symptomatic events (efficacy population) were obtained for 1949 patients. Venous thromboembolism and death from all causes occurred in 22.5% (221) of 982 ximelagatran-treated patients and in 31.9% (308) of 967 warfarin-treated patients (p < 0.001). Proximal deep-vein thrombosis and pulmonary embolism were observed in 3.1% (thirty) and 0.2%, respectively, of the patients in the ximelagatran group and in 3.4% (thirty-three) and 0.4%, respectively, of the patients in the warfarin group. The six deaths from all causes included 0.3% (four) of the ximelagatran-treated patients and 0.2% (two) of the warfarin-treated patients. Major bleeding was noted in 1% (twelve) of the ximelagatran-treated patients and in 0.4% (five) of the warfarin-treated patients (p = 0.09). CONCLUSIONS: Oral ximelagatran (36 mg twice daily), administered without coagulation monitoring or dose adjustment and started the day after total knee arthroplasty, demonstrates superior efficacy compared with warfarin prophylaxis, with no wound complications and no significant difference with respect to bleeding events, although the rate of major bleeding events was greater with ximelagatran than with warfarin. LEVEL OF EVIDENCE: Therapeutic Level I.

Aged↗