Noncardiac surgery brain injury: etiologic factors and prevention.

EXCERPT: During total joint arthroplasty, showers of bony spicules, marrow fat, and clot are carried by venous blood to the lungs, creating conditions not unlike those present in patients who have suffered traumatic long bone fractures. There is recent evidence that, like the fat embolism syndrome (FES), which often has a component of neurologic dysfunction, total joint arthroplasty and femoral nailing are associated with intraoperative brain embolization as determined by transcranial Doppler ultrasonography, and magnetic resonance brain imaging. Although there are good data demonstrating that intraoperative brain embolization occurs during total joint arthroplasties, the makeup and, even more importantly, the clinical significance of these emboli remain speculative. Brain microemboli resulting from cardiac surgery occur by the millions and may cause focal ischemia resulting in significant neurologic dysfunction. Our studies suggest that the major source of these microemboli is lipid droplets of the patient's fat that drip into the blood in the surgical field. This lipid-laden blood is aspirated and then returned to the patient via the cardiopulmonary bypass (CPB) apparatus. Our investigations have focused on the causes (microemboli), consequences (brain damage), and strategies for elimination of brain lipid microemboli resulting from salvaged blood collected during surgery.

Outcome after total hip arthroplasty. Comparison of a traditional disease-specific and a quality-of-life measurement of outcome.

The purpose of this study was to examine the relationship between the Harris Hip Score (HHS), a traditional method of patient assessment of a total hip arthroplasty (THA), and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), a commonly used health-related quality-of-life survey. One hundred forty patients returning for routine clinical follow-up evaluation of a primary THA were asked to fill out the SF-36 quality-of-life survey, as well as questions concerning their perceptions of their THA. The patient's surgeon assessed the THA with the traditional HHS. The correlations between the HHS and the SF-36 domains were highest in the physical component summary scores for male patients of all ages and female patients 65 years of age or older. The correlations were lower for the mental component summary scores of all patients, but particularly in female patients younger than 65. When the SF-36 scores were compared with age and sex-matched population norms, both age and sex were found to be important. Men younger than 65 had scores lower than norms in the physical function domains, but were comparable in the mental health domains. The older men had scores comparable to the norms in all domains. Female patients of all ages, however, had lower scores in the physical function domains. The greatest differences were noted in the female patients younger than 65. The HHS is commonly used to assess disease-specific pain and function in THA patients; however, the results of this study suggest that the SF-36 health survey can capture additional important quality-of-life domains that are influenced by a THA and that these domains are influenced by the age and sex of the patient. The combination of a disease-specific scoring system and a quality-of-life survey would allow a more global assessment of a THA in all patients. Studies evaluating the results of THAs should either assess the results of male and female patients separately when sample size is sufficiently large or use sex as a possible covariate in a multivariate analysis.

The efficacy of prophylaxis with low-dose warfarin for prevention of pulmonary embolism following total hip arthroplasty.

The selection of a prophylaxis regimen and its implementation have been influenced considerably by the decreased duration of hospital stays and the pressures of cost containment. The purpose of the present study was to determine the rate of symptomatic pulmonary embolism both before and after discharge, the number of days required to achieve an adequate level of anticoagulation, and the complications associated with the use of low-dose warfarin after total hip arthroplasty. Between 1987 and 1993, 1099 primary and revision total hip arthroplasties were performed in 940 patients who received low-dose warfarin for prophylaxis against thromboembolic disease. The average duration of prophylaxis was fifteen days (range, one to twenty-nine days). The target level of anticoagulation (as indicated by a prothrombin time of fourteen to seventeen seconds) was achieved an average of three days (range, one to sixteen days) after the operation. The level of anticoagulation was lower than the target range at the time of discharge after 257 total hip arthroplasties (23.4 per cent), and the target level was never achieved during the period of hospitalization after fifty-four such procedures (4.9 per cent). Twelve total hip arthroplasties were associated with a symptomatic pulmonary embolism; the over-all prevalence of this complication therefore was 1.1 per cent (95 per cent confidence interval, 0.4 to 1.9 per cent). Four pulmonary emboli were diagnosed before discharge and eight, after discharge. A fatal pulmonary embolism occurred after one procedure (0.1 per cent). Patients who had a history of symptomatic venous thromboembolic disease had a significantly increased risk of symptomatic pulmonary embolism after total hip arthroplasty (p = 0.001, Fisher exact test). A major bleeding episode occurred after thirty-two total hip arthroplasties (2.9 per cent). Patients who had a prothrombin time of more than seventeen seconds had a significantly increased risk of hematoma formation (p = 0.003, chi-square analysis). Prophylaxis with low-dose warfarin is safe and effective for the prevention of pulmonary embolism after total hip arthroplasty.

Low-dose warfarin prophylaxis to prevent symptomatic pulmonary embolism after total knee arthroplasty.

Pulmonary embolism poses a risk to patients undergoing total knee arthroplasty. The selection of an appropriate prophylaxis agent and its implementation have been influenced by decreased duration of hospital stay and the pressures of cost containment. The purpose of this study was to determine the inpatient and outpatient pulmonary embolism rates, the number of days required to attain the target level of anticoagulation, and complications associated with the use of a low-dose warfarin prophylaxis protocol after primary and revision total knee arthroplasty. Between 1984 and 1993, there were 815 primary and revision total knee arthroplasties that received low-dose warfarin prophylaxis at our institution. The average time to attainment of the target level of anticoagulation was 3 days. The average duration of warfarin prophylaxis was 12 days. Overall, there were a total of three symptomatic pulmonary embolisms (0.3%; 95% confidence interval, 0.08%-1.1%). There were eight (1%) symptomatic deep vein thromboses (all distal). There were two deaths (0.3%), but neither one was secondary to a pulmonary embolism. Seventeen knees (2.5%) developed a hematoma after surgery, and two of these patients required drainage of the knee. Low-dose warfarin prophylaxis is safe and effective in preventing symptomatic pulmonary embolism after total knee arthroplasty.

Effects of distal femoral centralizers on bone-cement in total hip arthroplasty. An experimental analysis of cement-centralizer bonding, cement void formation, and crack propagation.

Distal femoral centralizers of five different designs were inserted into model femoral stems and cemented into closed-ended tubes simulating a proximal femoral canal. Specimens underwent cyclic loading from 50 to 500 lb. for 0, 1, 2, 5, and 10 million cycles. Each specimen was then sectioned transversely at multiple levels to obtain serial cross-sections, beginning at the femoral stem tip and proceeding distally so as to include the full extent of the centralizer. The area of each section occupied by a centralizer and the total amount of porosity present in the cement surrounding the centralizers were measured using an image analyzer. A dye penetrant was then applied to each section to visualize cement cracks and areas of incomplete bonding between cement and centralizers. The number, length, and location of cement cracks were catalogued for each section. No cement cracks or lack of bonding was observed at the interface between cement and centralizers. There was greater porosity in the specimens containing centralizers than in controls without centralizers (P < .05). The cement surrounding two of the centralizer designs had a significantly smaller amount of porosity than the cement surrounding the other three designs (P < .05). The number of cracks did not depend on whether a centralizer was used, the type of centralizer, or the cycling duration. In the control specimens, failure to adequately plug the centralizer receptacle hole in the stem tip resulted in very large cement voids.

Differences between patients' and physicians' evaluations of outcome after total hip arthroplasty.

The purpose of this study was to compare patients' and physicians' evaluations of the results of 147 total hip arthroplasties. The patients and physicians independently evaluated pain and over-all satisfaction with the outcome of the procedure using a 10.0-centimeter visual-analog scale. They also answered a questionnaire with which they assessed general health, functional ability, and pain. The mean (and standard deviation) analog rating for pain (with 0.0 centimeters indicating no pain and 10.0 centimeters, severe pain) was 1.7 +/- 2.6 centimeters as assessed by the patients and 1.1 +/- 1.8 centimeters as assessed by the physicians (p < 0.001, paired t test). The mean analog rating for over-all satisfaction (with 0.0 centimeters indicating poor and 10.0 centimeters, excellent) was 8.6 +/- 2.1 centimeters as assessed by the patients and 8.8 +/- 1.7 centimeters as assessed by the physicians (p = 0.07, paired t test). There was a marked disparity between the patients' and the physicians' scores when the patients assigned a low score to a particular area. For the thirty patients who rated the pain as more than 4.0 centimeters, the mean analog rating was 6.8 +/- 2.1 centimeters according to the patients, while it was 3.6 +/- 2.7 centimeters according to the physicians (p < 0.001, linear regression). The mean analog rating for over-all satisfaction according to the nineteen patients who rated this parameter as less than 7.0 centimeters was 3.8 +/- 2.0 centimeters, while the mean rating according to the physicians 6.5 +/- 2.8 centimeters (p < 0.001, linear regression). The patients' and physicians' evaluations were similar regarding the results of the total hip arthroplasty when the patients had little or no pain and were satisfied with the result. However, the disparity increased as the patients' ratings for pain increased and their ratings for over-all satisfaction decreased. This study highlights a discrepancy between patients' and physicians' evaluations of the results of total hip arthroplasty. This discrepancy increased when the patient was not satisfied with the outcome. The use of patients' self-administered questionnaires as well as traditional physician-generated assessments may provide a more complete evaluation of the results of total hip arthroplasty.

Correlation of computed finite element stresses to bone density after remodeling around cementless femoral implants.

Fundamental to the development of a durable, uncemented femoral component is an understanding of the remodeling process that goes on after implantation. Predicting the bone remodeling that results from the use of a given hip implant would facilitate the design of a prosthesis that would optimize bone adaptation. This report combines the results of finite element stress analysis of the AML prosthesis implanted in vitro into a proximal femur with quantitative bone mineral density measured in vivo in the medial and lateral aspects of human femora at periods after implantation. Unimplanted femora were also analyzed for comparison purposes. Bone density measurements were obtained using dual energy x-ray absorptiometry. Absolute values of the maximum principal stress and maximum shear stress calculated in the femur at the time of implantation accurately predict bone density resulting from remodeling caused by the prosthesis. The calculated initial strain was not found to correlate with resultant bone density. These findings suggest that the results of stress analyses using three dimensional models of femora implanted in vitro can predict bone remodeling around prostheses and may be used to quantitate appropriate design criteria for total hip replacements.

Ipsilateral hip and femoral shaft fractures.

Forty-two cases of ipsilateral hip and femoral shaft fractures are reviewed. All patients were treated operatively for both fractures, with the exception of the shaft fracture in one child. Several different methods of fixation were used. The most common method was placement of multiple pins or screws around a previously placed intramedullary rod. Initial rodding of the shaft was not associated with avascular necrosis of the femoral head. Nonunion of the femoral neck occurred in three patients as a result of initial displacement and subsequent malreduction. Delays in operative fixation up to six weeks did not affect the ability to obtain union of the femoral neck. Complications involving the shaft fracture were at least as common as complications involving the femoral neck, suggesting that this component of the double injury should receive equally serious consideration. The hip fracture was initially overlooked in 13 cases (31%) without subsequent nonunion or avascular necrosis. Overall, the prognosis with regard to healing of the femoral neck and avascular necrosis of the femoral head in these combination injuries was found to be superior to that of isolated femoral neck fractures in young adults.

Dual-energy X-ray absorptiometry measurement of bone mineral density around porous-coated cementless femoral implants. Methods and preliminary results.

The measurement of bone mineral density in defined areas around metal implants has improved with the development of dual-energy X-ray absorptiometry. We used this technique to compare the bone mineral density adjacent to metal cementless femoral implants with that of identical regions of bone in normal proximal femora. We studied the anteroposterior views only of 72 femora which contained total hip implants and 34 non-operated femora. We compared the regional bone mineral density of bone adjacent to proximally porous-coated and distally porous-coated implants of one design, to measure the relative differences in the remodelling changes induced by different amounts of porous coating. We also measured differences in bone density with time and with variations in implant size (and therefore stiffness). The greatest decrease in bone mineral density (34.8%) occurred in the most proximal 1 cm of the medial femoral cortex around relatively stiff, extensively porous-coated implants. The next most severe decrease (20% to 25%) was in the next most proximal 6 cm of the medial femoral cortex. Small, progressive decreases in bone mineral density continued for five to seven years after implantation.

Catastrophic wear of tibial polyethylene inserts.

A number of factors play an important role in the wear-resistance of tibial polyethylene inserts. Among these are manufacturing processes that adversely affect the wear-resistance of polyethylene (such as heat treatments to the articular surface or gamma irradiation used for sterilization), tibio-femoral articular geometry, polyethylene thickness, knee alignment, femoral-component-bearing surface material, modularity of the tibial inserts and tibial trays, and quality of the polyethylene itself. The authors report an unusually high rate of failure by wear of tibial polyethylene inserts from a series of 176 Porous Coated Anatomic (PCA) knees in which there were eight revisions (4.5% of the series) performed for tibial polyethylene wear at an average of 60 months. Nine additional knees (5.1%) had thinning of greater than 30% of the initial polyethylene thickness. Four of the unsuccessful knees revealed areas of osteolysis filled with membranes containing large amounts of particulate polyethylene. In addition to the 176 knees from a series from a Los Angeles university, the cases of five other knees in four patients who came for treatment from outside hospitals with full-thickness wear of the tibial polyethylene are discussed. One of these five knees was a cementless PCA knee that developed massive osteolysis in response to the particulate polyethylene debris.

Patient activity, sports participation, and impact loading on the durability of cemented total hip replacements.

Patients with either cemented surface replacements or cemented stemmed hip prostheses and who regularly participate in sporting activities or heavy labor after total joint arthroplasty are at twice the long-term risk of requiring revision surgery for loosening as patients who are less active. For patients with surface replacement total hip arthroplasty (THA), the adverse effects of activity are greatest in patients with preoperative diagnoses other than osteoarthritis, and were seen by the sixth year postsurgery. For patients with conventional stemmed prostheses, the effects of patient activity are not seen until about ten years postsurgery. For resurfacing THA for osteoarthritis, the long-term of loosening is primarily in patients who participate in high impact activities.

Periprosthetic chronic inflammation characterized through the measurement of superoxide anion production by synovial-derived macrophages.

Periprosthetic macrophages were isolated from the synovium of primary and revision arthroplasty patients. Inflammatory activity was determined by the level of superoxide (O2-) production de novo and in response to phorbol myristate acetate (PMA) stimulation. Nonstimulated primary arthroplasty-derived macrophages produced 2.54 +/- 2.04 pmoles of O2-/minute/10(5) cells. When identical reaction tubes were stimulated with PMA, O2- levels increased to 5.76 +/- 3.77 pmol of O2-/minute/10(5) cells. Nonstimulated revision arthroplasty-derived macrophages produced 3.26 +/- 2.02 pmol of O2-/minute/10(5) cells during this ten-minute time period. When identical reaction tubes were stimulated with PMA, O2- levels increased to 3.98 +/- 2.52 pmol of O2-/minute/10(5) cells. The difference in the ratio of O2- production in response to stimulation between primary and revision groups was statistically significant. The observation of a chronic moderate level of activation and the lack of responsiveness to a potent stimulator suggests that macrophage inflammatory activity is down-regulated in periprosthetic synovium.

Cementless total joint arthroplasty prostheses with titanium-alloy articular surfaces. A human retrieval analysis.

Surgical implants of titanium alloy (Ti-6Al-4V) have been found to be susceptible to abrasive wear, resulting in the well-known phenomenon of metallosis. In the presence of the acrylic debris generated by loose joint arthroplasty prostheses, this abrasive wear is greatly increased. However, the bone loss seen in these cases has generally been presumed to be due to the osteolytic effects of particulate acrylic, not the alloy debris, which has generally been assumed to be biocompatible. To examine the in vivo effects of titanium-alloy wear without the added presence of acrylic debris, a comprehensive analysis was made of cementless human joint arthroplasty prostheses with Ti-6Al-4V alloy surfaces articulating on ultra-high molecular weight polyethylene (UHMWPE). Specimens, including the prostheses, synovium, pseudocapsule and additional soft tissues, and periarticular bone, were retrieved from 22 hips and two knees. Specimens were examined by histologic techniques, energy-dispersive X-ray analysis, and electron microscopy. Serial sections of the implants were evaluated for tissue ingrowth. Tissues surrounding all joints implanted more than one year showed some degree of discoloration indicative of metallosis, whereas after two years the synovium was hypertrophic and villiform. Histologic evaluation showed good fixation by bony ingrowth in the vast majority of cases, although location and extent of ingrowth was dependent on numerous factors. Viability of ingrowth bone was established by fluorochrome labeling. However, despite good biologic fixation, cavitary osteolysis of the bone surrounding the implants was frequently identified. These lesions were filled with sheets of aggressive macrophages within a matrix of fibrous tissue and necrotic debris. Under polarized light the macrophages were found to be filled with alloy and polyethylene fragments of a characteristic size. Osteoblast-mediated remodeling of bone was infrequently observed. Instead, the bone was resorbed along a front in contact with the granulomatous tissues filling the cystic lesions. Visible burnishing was observed on every articular surface, with a linear relationship between wear and time implanted. By one year the surfaces were covered with a characteristic "scratch and gouge" pattern, similar on all sizes of femoral heads as well as the total knee prostheses. This study demonstrates that the combination of Ti-6Al-4V alloy and UHMWPE, when used as a bearing surface combination in total joint arthroplasty prostheses, results in excessive wear of both metal and polymer.(ABSTRACT TRUNCATED AT 400 WORDS)

Total hip replacement for patients who have ankylosing spondylitis. The importance of the formation of heterotopic bone and of the durability of fixation of cemented components.

Fifty-three total hip replacements were performed in thirty-one patients who had ankylosing spondylitis. After an average period of follow-up of 6.3 years, cemented conventional hip prostheses proved to be very durable in this young population (average age, forty-three years). Only one primary conventional hip prosthesis was revised for aseptic loosening, seventeen years after implantation. Clinically important heterotopic bone (Classes III and IV of Brooker et al.) developed in 11 per cent of the patients, all of whom had had a previous operation on the hip, postoperative infection, or complete ankylosis preoperatively. If a patient has clinically important heterotopic bone after one operation on the hip, and an arthroplasty of the contralateral hip or reoperation on the same hip is to be done, prophylactic treatment should be considered for prevention of formation of heterotopic bone.

Dislocation of a posterior stabilized total knee prosthesis. A report of two cases.

Posterior stabilized knee prostheses have been recommended for knees with posterior cruciate deficiency, as well as for knees with prior patellectomy. Two cases are presented in which a complete dislocation of a Kinematic II Stabilizer prosthesis occurred after primary knee arthroplasty. The mechanism of dislocation was a varus or valgus stress while the knee was flexed. This previously unreported complication of dislocation after primary knee arthroplasty with a posterior stabilized knee prosthesis was, we believe, due, in part, to the design of this prosthesis, which provides little mediolateral stability in flexion, in combination with a mild degree of laxity of the collateral ligaments. This complication could be prevented by use of a prosthesis with greater inherent mediolateral stability.

Joint replacement for ankylosed hips.

Forty-one fused hips in thirty-eight patients were converted to total hip replacement. The average length of follow-up was seven years. The predominant indications for conversion were progressively disabling pain in the low back or the hip, or both; loss of function due to immobility or malposition of the hip; and progressive pain and instability of the knee (usually ipsilateral). The postoperative arc of flexion averaged 87 degrees. Limb-length discrepancies improved an average of 2.5 centimeters. Postoperative function of the abductor muscles depended on the preoperative quality of those muscles and on the accuracy of the biomechanical restoration. Postoperative strength of the muscles of the hip improved for two years or more in most patients. There was complete or major relief of pain, improved mobility of the hip, and decreased dependence on supports for walking. There were nine failures: four because of sepsis, four because of loosening of the femoral component, and one because of malposition of the acetabular component. The failures were predominantly in patients who were fifty years old or less at the time of arthroplasty, patients who had had two or more previous operations, and patients who had had an injury to the hip. The quality of the results approached that after primary hip arthroplasty in older patients who have not had multiple previous operations on the hip. Survivorship analysis of the spontaneously fused hips that were treated with conventional hip replacement predicted a probability of survival of the implant of 96 per cent at thirteen years postoperatively (p = 0.048).

Three dimensional imaging techniques for the reconstruction of a complex hip problem. A case report.

This report illustrates the use of three-dimensional imaging techniques to solve a difficult reconstruction problem of the hip. Custom prosthetic components manufactured by a computer-assisted design process are used in this procedure.

Porous surface replacement of the hip with chamfered-cylinder component.

One hundred porous surface replacements (PSR) were performed in 92 patients (63 men and 29 women) with a mean age of 53 (range 17-76). Follow-up times range from 1 to 4 years, with 48 patients having a follow-up of at least 2 years. Preoperative diagnoses were osteoarthritis (OA) 63, osteonecrosis (ON) 13, dysplasia 9, rheumatoid-ankylosing spondylitis 6, and other 9. Seventeen hips had metal-backed acrylic-fixed THARIES acetabular sockets, nine hips had a porous cobalt chrome hemispheric beaded acetabular component with adjuvant fixation screws and externally protruding screw hubs, and 74 hips had a porous chamfered cylinder-design acetabulum. Pain relief had been immediate and more complete than with acrylic-fixed or biologic-ingrowth stem-type replacement with comparable walking and function improvements. There have been no major systemic complications, sepsis, or loosening. There have been two transient peroneal nerve palsies and three trochanteric fibrous unions. There have been three reoperations, one for subluxation, one for "metalosis" due to mesh pad loosening, and one femoral neck fracture. Examination of one removed femoral surface component which has been histologically sectioned revealed excellent (90%) bone in-growth. Circumferential progressive radiolucencies developed at the bone-cement interface by 1 year in all of the 17 acrylic-fixed acetabular components. Reaming or seating defects were noted in 25% of the ingrowth components on postoperative radiographs. Radiographic analysis of immediate postoperative films of the chamfered cylinder design acetabular components frequently demonstrated bone-component interface radiolucencies which represented component seating defects. These initial interface radiolucencies became progressively more narrow over the first six months postoperatively suggesting "healing" of the reamed bone-component interface with trabecular bone around the chamfered cylinder acetabular components. Partial healing of initial interface voids with residual narrow radiolucencies were typical of the nine hemispheric-design acetabula with adjuvant screws and screw hubs. This new porous surface replacement (PSR) of the hip using porous ingrowth fixation avoids the major disadvantages of acrylic-fixed SR: excessive acetabular reaming and difficulty with acetabular revision. (When conversion to stem-type replacement is necessary the modular polyethylene socket liner can be exchanged.) The PSR has the prospect of enhanced fixation and improved longterm durability.