The effect of stem modularity and mode of fixation on tibial component stability in revision total knee arthroplasty.

The effect of stem length, diameter, and mode of fixation on the motion and stress transfer of a cemented tibial tray were evaluated for in 12 cadaver knees. There was a significant decrease in motion of the tibial tray with increasing press-fit stem length (75-150 mm) and increasing stem diameter (10-14 mm). Cemented tibial stems showed significantly less tray motion than uncemented stems. The short cemented stems produced tray stability equivalent to long press-fit stems. Although there was a trend for increased proximal tibial stress shielding with the use of cement and longer, wider stems, the trend was not statistically significant. Modular, press-fit stems can achieve tray stability similar to a smaller cemented stem and can avoid the potential problems with cement.

Efficacy of preoperative skin traction in hip fracture patients: a prospective, randomized study.

OBJECTIVE: To compare the analgesic benefit of preoperative skin traction with the placement of a pillow under the injured extremity in patients with hip fractures. DESIGN: Prospective, randomized clinical study. SETTING: University-affiliated teaching institution. PATIENTS AND PARTICIPANTS: One hundred consecutive patients with hip fractures admitted to the authors' institution who met inclusion criteria were enrolled. Fifty-five patients had femoral neck fractures, and forty-five patients had intertrochanteric fractures. The average patient age was seventy-eight years. INTERVENTION: All patients were preoperatively randomized into two intervention groups. One group underwent placement of five pounds of skin traction on the injured extremity, whereas the second underwent placement of a pillow under the injured extremity. Fifty patients were enrolled in each intervention group. RESULTS: With respect to immediate postintervention pain levels, patients treated with a pillow showed a trend toward better pain relief, as compared with patients treated with skin traction; however, this was not statistically significant. On the morning after admission, patients treated with a pillow had a statistically significant greater reduction in pain (p = 0.04). These patients also requested a statistically significant lower amount of pain medication (p < 0.01). CONCLUSIONS: The authors think that preoperative skin traction in patients with hip fractures does not provide significant pain relief, as compared with pillow placement under the injured extremity, and thus should not be routinely performed in this patient population for analgesia.

The test-retest reliability of a new occupational risk factor questionnaire for outcome studies of low back pain.

This study reports the test-retest reliability of a 25-item occupational risk factor questionnaire that can be self-administered in clinical settings and used in outcome studies of low back pain or return to work programs. Subjects were 24 patients (workers on sick leave due to acute low back pain), 29 co-workers on active duty in the same jobs in a utility company, and 53 supervisors. Eighty-six subjects were re-tested within a mean interval of 7-10 days; one group of 20 supervisors was re-tested within 81 days. The questionnaire was self-administered during individual interviews. Reliability was estimated by the kappa statistic as the agreement on the scores within the raters in each group. The agreement ranged from 'slight' (0.15) to 'almost perfect' (0.93) when the re-test interval was less than 43 days. Patients and non-patients were consistent in their assessment of the job demands. rights reserved.

Anticoagulant treatment of thromboembolism with intravenous heparin therapy in the early postoperative period following total joint arthroplasty.

BACKGROUND: Treatment of thromboembolism with intravenous heparin therapy in the early postoperative period after total joint arthroplasty has been associated with a high rate of complications. The purpose of the present study was to compare the rate of bleeding complications in a group of patients who required intravenous heparin therapy for the treatment of thromboembolism after total hip or knee arthroplasty with the rate in a control group of patients who received only prophylactic anticoagulation. METHODS: The postoperative courses of forty-four consecutive patients who were managed with intravenous administration of heparin and oral administration of warfarin for the treatment of a thromboembolic event following unilateral total hip or knee arthroplasty were compared with those of a control group of 376 consecutive patients who had these same procedures but did not have a thromboembolic complication. The patients in the control group were managed with prophylactic anticoagulation with use of enoxaparin. Sixty-eight percent (thirty) of the forty-four patients in the heparin group received the initial dose of heparin on or before the fourth postoperative day, and 82 percent (thirty-six) received an initial bolus of 5000 units of heparin at the initiation of therapy. RESULTS: The rate of bleeding complications was 9 percent (four of forty-four) in the heparin group, compared with 6 percent (twenty-three of 376) in the control group (p = 0.44). The mean transfusion requirement in the heparin group (1.8 units of packed red blood cells) was significantly greater than that in the control group (0.8 unit) (p < 0.0001). Three of the four patients who had a bleeding complication while receiving heparin and warfarin had coagulation parameters that were substantially higher than recommended levels. The mean duration of hospitalization in the heparin group (fifteen days) was significantly longer than that in the control group (seven days) (p < 0.0001). CONCLUSIONS: The results of the present study suggest that the use of intravenous heparin therapy for the treatment of thromboembolism in the early postoperative period after total joint arthroplasty is associated with a rate of bleeding complications that is similar to that associated with the use of prophylactic anticoagulation with use of enoxaparin alone. One should expect an increased transfusion requirement and a longer duration of hospitalization for patients who require intravenous heparin therapy for the treatment of a thromboembolic event.

A functional recovery score for elderly hip fracture patients: I. Development.

OBJECTIVE: To develop a Functional Recovery Score for ambulatory elderly hip fracture patients related to independent functioning to assess restoration of function to prefracture status. STUDY DESIGN/METHODS: The phases of this effort consisted of: (a) identification of five relevant components represented by sixteen specific functional capacities; (b) assessment of the importance independent community-dwelling elderly gave to the sixteen functional capacities; (c) pilot testing of a sixteen-item preliminary questionnaire in recovering elderly hip fracture patients; and (d) modification of the questionnaire to an eleven-item score. RESULTS: The resulting eleven-item Functional Recovery Score is comprised of three main components: basic activities of daily living (BADL) assessed by four items, instrumental activities of daily living (IADL) assessed by six items, and mobility assessed by one item. Basic activities of daily living comprise 44 percent of the score; instrumental activities of daily living comprise 23 percent, and mobility comprises 33 percent. Complete independence in basic and instrumental activities of daily living and mobility results in a score of 100 percent.

Autoimmune-associated congenital heart block: demographics, mortality, morbidity and recurrence rates obtained from a national neonatal lupus registry.

OBJECTIVES: The present study describes the demographics, mortality, morbidity and recurrence rates of autoimmune-associated congenital heart block (CHB) using information from the Research Registry for Neonatal Lupus. BACKGROUND: Isolated CHB detected at or before birth is strongly associated with maternal autoantibodies to 48-kD SSB/La, 52-kD SSA/Ro and 60-kD SSA/Ro ribonucleoproteins and is a permanent manifestation of the neonatal lupus syndromes (NLS). Available data are limited by the rarity of the disease. RESULTS: The cohort includes 105 mothers whose sera contain anti-SSA/Ro or anti-SSB/La antibodies, or both, and their 113 infants diagnosed with CHB between 1970 and 1997 (56 boys, 57 girls). Of 87 pregnancies in which sufficient medical records were available, bradyarrhythmia confirmed to be CHB was initially detected before 30 weeks of gestation in 71 (82%) (median time 23 weeks). There were no cases in which major congenital cardiac anatomic defects were considered causal for the development of CHB; in 14 there were minor abnormalities. Twenty-two (19%) of the 113 children died, 16 (73%) within 3 months after birth. Cumulative probability of 3-year survival was 79%. Sixty-seven (63%) of 107 live-born children required pacemakers: 35 within 9 days of life, 15 within 1 year, and 17 after 1 year. Forty-nine of the mothers had subsequent pregnancies: 8 (16%) had another infant with CHB and 3 (6%) had a child with an isolated rash consistent with NLS. CONCLUSIONS: Data from this large series substantiate that autoantibody-associated CHB is not coincident with major structural abnormalities, is most often identified in the late second trimester, carries a substantial mortality in the neonatal period and frequently requires pacing. The recurrence rate of CHB is at least two- to three-fold higher than the rate for a mother with anti-SSA/Ro-SSB/La antibodies who never had an affected child, supporting close echocardiographic monitoring in all subsequent pregnancies, with heightened surveillance between 18 and 24 weeks of gestation.

Active analog pipeline delays for high signal rates in multistation flow cytometers.

Flow cytometers with sequential measuring stations require alignment of event timing information to assure that multiparameter data for each cell are properly correlated. Information from the first detector must be delayed until signals are produced at the last detector, with adjustments to align them in time for simultaneous digitization after the last measurement is completed. By using an analog "pipeline" delay, the deadtime between the first and last measuring stations can be minimized. The described device is capable of acquiring and propagating many signals within the delay period, with good fidelity at high signal rates. An integrated circuit charge-coupled device (CCD), which is an analog shift register, is shown to be useful as a signal delay in the time range from 22 microseconds to several milliseconds.

Signal processing electronics for multiple electronic and optical measurements on cells.

Processing electronics for flow cytometry applications requiring simultaneous or sequential analysis of multiple electrical and optically sensed signals has been developed. A maximum of six analog signals are input to the processor. A measurement mode selector determines what signals are to be analyzed and the initial timing sequence of sense gates for acquiring signal crest values. Processor signal-triggering and sense gate time delays are selectable. Logic coincidence-anticoincidence circuits determine constraints on incoming signals. Gated peak-sense and hold signals are routed to computer interface electronics for digitizing and are then displayed as frequency distribution histograms using an LSI-11 computer. Signals also are processed as single parameters, ratios, and gated single parameters for output to a multichannel pulse-height analyzer and cell sorting electronics. The functional features of the processor are described along with examples illustrating simultaneous and sequential analysis of cultured cells stained with fluorescent dyes.

Modular electronics for flow cytometry and sorting: the LACEL system.

LACEL is newly developed, fast, general-purpose data acquisition and processing system for flow cytometric applications. The system's modular electronics allows flexibility in system configurations. The system can process as many as eight input analog parameters and can transfer 16-bit words between the user's electronics and the computer with standard input/output interfaces. The system's 8-fold coincidence logic capability can be set to operate with the noncoincidental timing that may occur in multiparameter flow measurements. As many as four parameters can be used to establish amplitude and timing criteria for each of two sorting directions. Two experiments can be on line with the computer at one time.

Differential light scattering photometer for rapid analysis of single particles in flow.

A differential light scattering photometer has been developed for rapid size analysis of single particles in flow. A fluid stream carrying individual particles in single file intersects a focused laser beam at the primary focal point of an annular strip of an ellipsoidal reflector situated in a scattering chamber. The light scattered from polar angles theta = 2.5-177.5 degrees at azimuthal angles phi = 0 and 180 degrees , spanning a circle of 355 degrees , is reflected onto a circular array of 60 photodiodes. The signal processing electronics and computer storage can accept 32 signals/particle at rates up to 1000 particles/sec. Photometer performance is tested by comparing measured responses from individual spherical particles with angular scattering patterns calculated for the particular detector geometry. These patterns exhibit the required symmetry in the two half scattering planes. Response measurements for eight samples with particle diameters of 1.1, 2.7, 5.0, 7.9, 10.0, 12.5, 15.6, and 19.5 microm are consistent with calculated size-response curves. The composition of a mixture of five components with particle diameters of 1.1, 5.0, 10.0, 15.6, and 19.5 Am is determined from an analysis of light scattering measurements at various forward-scattering angles.

A real-time delay monitor for flow-system cell sorters.

For optimum performance in cell sorting, it is critical to assure proper timing in the charging of droplets to be deflected. A method for determining the transiet delay time in cell sorters has been devised and applied to daily operation in the Los Alamos sorter systems. This delay monitor relies on detection of either scattered or absorbed light from cells in the fluid stream near the point of droplet breakoff.

Pulse-height light-scatter distributions using flow-systems instrumentation.

Several laboratories have recently been making light-scatter measurements on cells and other particles using flow-systems instrumentation. We at the Los Alamos Scientific Laboratory, as well as others, have obtained multimodal pulse-height distributions in certain angular regimes from particles of supposedly uniform characteristics. Because it was assumed that multimodal distributions implied characteristics of multivalue, the accuracy of such data has been doubted. In the present work, pulse-height distributions anticipated on the basis of exact electromagnetic theory were calculated for particles of known characteristics. These calculated pulse-height distributions agree quite well with those obtained experimentally. Physical optics form the basis for the explanation of the complex pulse-height distributions obtained experimentally. However, the results of this study show that certain cautions are necessary in the interpretation of light-scatter data presented in this manner.

A flow-system multiangle light-scattering instrument for cell characterization.

A flow-system cell-analysis instrument is described in which cells from a heterogeneous population are characterized by their light-scatter patterns alone. As the cells pass at high speed through a focused helium/neon laser beam, the scatter pattern from each cell is sampled simultaneously at up to 32 angles between 0 degrees and 30 degrees with respect to the laser beam axis, and the scatter pattern for each cell is transferred to a computer. A mathematical clustering algorithm is used to determine the number of classes into which the cells can be divided, and a linear separation algorithm is used to find the boundaries between the classes. Preliminary results on exfoliated cells from gynecological specimens are presented. This technique may be useful for automated prescreening of gynecological specimens.