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A retrospective study of 201 anatomic graduated component total knee arthroplasties implanted with hybrid fixation at the authors' center was performed in response to conflicting data in the literature concerning the benefits of a hybrid method. Selection for hybrid fixation was nonrandomized and based on femoral component fit. Survivorship analysis was performed, and rates of radiolucent lines surrounding the femoral component and occurrence of osteolysis were noted. At 7 and 13 years, survivorship with tibial or femoral revision as the end point was 0.9926 and 0.9732, respectively. Radiolucencies were found adjacent to 15 femoral components at final followup (seven in Zone 1, three in Zone 2, five in Zone 3, one in Zone 4, two in Zone 5, zero in Zone 6). Osteolysis was observed in one knee after secondary evaluation. Hybrid fixation in a selected patient population can result in excellent results in middle to long-term followup.

Production and package sterilization techniques for the polyethylene used in acetabular components for total hip arthroplasties are known to affect wear. We considered three combinations of techniques: sterilization by radiation in inert gas with isostatically molded polyethylene, in inert gas and ram-extruded polyethylene, and in air with extruded polyethylene. The intent of this study was to confirm that molded polyethylene and polyethylene radiated in inert environments reduce wear rates in vivo, to determine the combination of methods with the least wear, and to determine how much variance in wear is attributable to these methods. We reviewed 150 consecutive total hip arthroplasties done in 133 patients using 28-mm cobalt-chrome femoral heads and polyethylene-lined, titanium, ring-locked acetabular components. The least wear occurred in gamma inert-molded polyethylene components. The mean volumetric wear rates were 52.12 mm3/year for gamma inert-molded, 62.32 mm3/year for gamma inert-extruded, and 66.09 mm3/year for gamma air-extruded polyethylene components. Relative risk assessment found gamma air-extruded and gamma inert-extruded polyethylene components to wear 16% and 11% more than gamma inert-molded polyethylene components, respectively. Gender, body mass index, and age accounted for the greatest amount of the explained variance in volumetric wear (57.5%, 21.6%, and 14.4, respectively), followed by angle of wear (3.4%), and sterilization and production technique (3.2%).

A consecutive series of 220 primary posterior-cruciate ligament-retaining total knee replacements were done in 148 patients with rheumatoid arthritis. From this group, 212 total knee replacements (141 patients) were followed up for an average of 10 years. Average knee scores at 5, 10, 15, and 20 years after operation improved to 86, 83, 88, and 89, respectively, and average function scores improved to 70, 72, 64, and 88, respectively. Five knees (2.4%) were revised for deep infection. Posterior instability, recurvaum, or mediolateral instability, combined or otherwise, occurred in 15% (32 knees; in 31 patients). Three tibial components (1.4%) were revised: one for suspected aseptic loosening and two for instability. Excluding infections and failed metal-backed patellas, Kaplan-Meier survival rates were 99.5%, 97.9%, and 96.5%, respectively. Favorable long-term results may be achieved with posterior-cruciate ligament-retaining total knee replacements in patients with rheumatoid arthritis. Concern remains, however, about rotational instability in certain cases associated with preoperative genu-valgum and ipsilateral planovalgus deformity.

The purpose of this study was to examine the failure mechanisms and factors associated with failure of a nonmodular metal backed cemented tibial component. Out of 3152 total knee replacements done for osteoarthritis, 41 tibial components had been revised (1.3%). Four distinct failure mechanisms were identified: 20 knees were revised for medial bone collapse, 13 for ligamentous imbalance, 6 for progressive radiolucencies, and 2 for pain. Factors associated with medial bone collapse were varus tibial component alignment more than 3.0 degrees , Body Mass Index higher than 33.7, and overall postoperative varus limb alignment. Ligamentous imbalance was more prevalent in knees with preoperative valgus deformity. There were no knees revised for tibial component polyethylene wear or osteolysis. We conclude that the dominant failure mechanisms for this component design are related to preoperative deformity, technical factors of component alignment, overall limb alignment, and ligamentous imbalance.

Genu recurvatum deformities are unusual before total knee arthroplasty (TKA), occurring in less than 1% of patients. Because of its rarity, concern may exist regarding the recurrence of the deformity and the potential for instability after TKA. Recurvatum may be associated with a severe osseous deformity, including genu valgum, capsular or ligamentous laxity, and, rarely, neuromuscular disease. In the presence of the latter, a plantarflexion contracture of the ankle also may be present. Therefore, specific attention should be given preoperatively to evaluation of the quadriceps, hamstrings, and gastrocnemius complex. Because genu recurvatum is known to recur in patients with certain neuromuscular disorders, the etiology of the hyperextension deformity must be elucidated thoroughly before surgery. In the absence of neuromuscular disease, however, hyperextension deformities tend not to recur after TKA. Care should be taken to avoid even mild degrees of residual instability in the coronal plane at surgery because this is associated with increased extension in the postoperative period.

The purpose of the current study was to review the results of total knee replacement (TKR) in patients with diabetes mellitus and to test the hypothesis that patients with diabetes achieve inferior results after TKR. From a consecutive series of 5220 primary cemented TKRs, 363 were done in 291 patients with diabetes mellitus. Cefuoxime-impregnated cement was used routinely. The results in the study group were compared with the results in the patients without diabetes who had TKR during the same period. The followup averaged 52 months. Knee scores were higher in patients with diabetes preoperatively (47 versus 38) and postoperatively up to 7 years (80 versus 75). The average preoperative and postoperative pain scores also were higher in patients with diabetes. Four deep infections (1.2%) occurred in patients with diabetes versus 35 deep infections (0.7%) in patients without diabetes. The revision rate (including infections) was greater in patients with diabetes (3.6% versus 0.4 %). Knee and pain scores were similar in patients with insulin-dependent and noninsulin-dependent diabetes. Postoperative function scores, however, were lower in patients with insulin-dependent diabetes. In the study group, all deep infections occurred in patients with insulin-dependent diabetes.

The purpose of the current study was to evaluate and determine the mechanism and etiology of failure of components that failed in long-term followup of Anatomic Graduated Component total knee replacements. The authors previously reported the survivorship of 4583 Anatomic Graduated Component total knee arthroplasties done during a 17-year period. The current study was done to evaluate the etiology and cause of failure of the components that failed. There were six (0.18%) failures of the femoral component. There were 21 tibia components that failed (0.46%). Twelve tibial components failed because of an osteonecrotic lesion in the medial tibia plateau. The clinical survival rate with revision or loosening of one or more components was 98.9% at 15 years. No component was revised for polyethylene wear or osteolysis. This total knee replacement has proved to have minimal wear and excellent longevity with time with no revisions between 10 and 15 years despite having nearly flat-on-flat geometry and retaining the posterior cruciate ligament. The most common cause for revision (12 tibial components) was because of an osteonecrotic lesion in the medial tibia plateau, which developed after surgery and led to loosening.

Between June 1987 and March 1997, 57 total knee replacements were done in 53 patients with at least 5 degrees hyperextension deformity as measured on physical examination. The average recurvatum measured 11 degrees (range, 5 degrees-20 degrees). No cases of major ligamentous instability, neuromuscular disease, or inflammatory arthropathy were identified before surgery. Before surgery, Knee Society knee, function, and pain scores averaged 41 points, 41 points, and 13 points, respectively. A posterior cruciate-retaining prosthesis was implanted in all patients. The followup averaged 4.5 years (range, 3-10 years). Knee, function, and pain scores improved to 81 points, 78 points, and 43 points, respectively. Postoperative extension averaged 0 degrees (neutral) (range, 10 degrees hyperextension-10 degrees contracture). Only two (3.5%) knees had a hyperextension deformity after surgery. Both deformities measured 10 degrees and were in patients with a preoperative diagnosis of osteoarthritis. At final followup, no knee replacement was revised for any reason. In addition, only one case of a progressive radiolucent line greater than 1 mm (tibial Zone 7) was observed. Although the etiology of a hyperextension deformity should be elucidated before surgery, its presence does not preclude a well-functioning total knee replacement.

The purpose of the current study was to evaluate the authors' 15-year experience with the Anatomic Graduated Components total knee replacement. This is a report of the survivorship of 4583 Anatomic Graduated Component total knee arthroplasties. Kaplan-Meier survival analyses were performed with the end point defined as radiographic loosening, revision, or both. This end point was subdivided into the best case scenario in which it was assumed that all the patients lost to followup were doing well throughout the study and a worst case scenario in which it was assumed that all patients lost to followup had failed results at their last clinic visit. There were six (0.18%) femoral, 21 (0.46%) tibial, and 180 (4.2%) all-polyethylene patellar component failures secondary to aseptic loosening. All femoral components and 90% of the tibial components were revised; however, only 15 patellar components were revised. The clinical survival rate with revision of one or more of the components was 98.86% at 15 years. Despite having nearly flat-on-flat geometry and retaining the posterior cruciate ligament, which should increase the stresses in the polyethylene and at the bone-cement interface, this total knee replacement has proved to have minimal wear and excellent longevity with time. The authors think this is a result of the direct compression molded polyethylene articulation and the nonmodular configuration that incorporates metal backing on the tibial component and eliminates back-sided tibial component polyethylene wear.

A consecutive series of 387, one-piece, 8-mm tibial components were implanted in 313 patients. All tibial prostheses were manufactured with 4.4 mm of polyethylene directly molded to a 3.6 mm cobalt chrome metal baseplate. The average age of the patients at surgery was 70.6 years. From this group, a subset of 116 patients underwent bilateral total knee arthroplasties with an 8-mm tibial component on one side and at least a 10-mm thick tibial component (at least 6.4 mm of polyethylene) on the other side. The followup averaged 10.7 years. Postoperative knee and pain scores average 81.4 points and 47.2 points, respectively. No radiographic polyethylene wear or osteolytic lesions were identified. Tibial radiolucencies were observed in four knees. There were nine failures (2.3%). Three knees were revised for infection. Five knees were revised for metallosis secondary to failure of metal-backed patellas. No loose tibial components were identified. Defining failure as revision for any reason or loosening of any component, Kaplan-Meier survival rates at 5, 10, and 15 years were 98.7%, 95.4%, and 94.3%, respectively. There was no significant difference in clinical scores or survival rates between the knee components with thicker (at least 6.4 mm) or thinner (4.4 mm) polyethylene.

The patellar component of total knee replacement is the most frequent source of nonseptic complications after total knee arthroplasty. The purpose of the current study was to review the radiographic factors associated with loosening of all-polyethylene patellar components. Four thousand five hundred eighty-three cases of Anatomic Graduated Components total knee replacements were performed at the authors' institution during the past 15 years. Radiographs were reviewed and loosening was defined as global radiolucency or component migration. Four thousand two hundred eighty-seven allpolyethylene patellar components were implanted. There were 180 (4.2%) loose all-polyethylene patellar components. The mean time to loosening was 2.6 years (+/- 1.75 years). Fifteen (0.3%) patellar components required revision. Five radiographic features were associated with failure. The incidence and mean time of appearance were recorded: (number; incidence; time) (1) Bone-cement radiolucency, n = 174, 96.7%, 1.4 years; (2) increased density, n = 118, 65.6%, 1.8 years; (3) trabecular collapse of the bone, n = 160, 88.9%, 2.3 years; (4) patella fracture and fragmentation, n = 133, 73.9%, 2.5 years; and (5) lateral subluxation of the residual patella bone, n = 146, 81.1%, 2.9 years. Lateral retinacular release was associated with an increased rate of patellar loosening. Loosening of the allpolyethylene patella component is an avascular process strongly associated with lateral retinacular release and for which the patient infrequently requires revision surgery.

Patients who had anterolateral and posterolateral approaches in total hip replacement surgery were compared clinically for limp, dislocation, hospital stay, and discharge disposition. The only statistical difference was that the posterior approach had a statistically higher dislocation rate. Although the number of patients with limp was higher in the anterolateral group, the difference was not statistically different.

This controlled study compared the strength and porosity of 48 polymethylmethacrylate cement-implant constructs prepared with open bowl versus vacuum mix technique. Forty-eight blast finished stainless steel rods of 13 mm diameter were implanted with centralizers into 17-mm inner diameter tubes that had been retrograde filled with polymethylmethacrylate cement. The eight cement preparations used were open bowl and vacuum mixed Simplex, Osteobond, Zimmer Dough Type, or Palacos R. Six replications of each condition were performed. The tubes were maintained at 37 degrees C. Each tube was cut transversely into five segments. The center three segments were used for data analysis: pushout strength, cycles to failure, and interface porosity analysis. Rod pushout data showed there was no significant difference between open bowl and vacuum mixed samples when all cement brands were combined. Mean sheer force for Palacos R vacuum mixed samples was greater than open bowl (634+/-47 versus 423+/-171), whereas the force for the Zimmer Dough Type cement open bowl was greater than that of the vacuum mixed samples (901+/-71 versus 705 +/-82). Cycles to failure data did not show significant differences when open bowl and vacuum mixed samples were compared when cements were analyzed individually or combined. Image analysis of cement-implant interfaces showed that vacuum mixing reduced void area significantly compared with open bowl mixing in the Palacos R and Osteobond preparations. Vacuum mixing does not appear to reduce cement prosthesis interface porosity or improve its mechanical properties in all cements.

The preoperative radiographs of 1015 patients undergoing 1163 total hip replacements for osteoarthritis were evaluated to determine if a relationship exists between the extent of osteoarthritis and the clinical results of a total hip replacement. Preoperative radiographs were graded with respect to the degree of cartilage space loss, direction of cartilage space loss (femoral head migration), and severity of osteophyte formation. Followup averaged 32.1 months (range, 6-93 months). Greater degrees of cartilage space loss correlated with lower hip scores preoperatively but were unrelated to preoperative pain. These patients had statistically less pain at 6 months and 1 year. Patients with superior cartilage space loss before surgery also had statistically less pain at 6 months. However, at 3 years and beyond, pain was independent of degree of preoperative cartilage space loss, osteophyte formation, or femoral head migration. In addition, hip scores at any followup were independent of the degree of osteoarthritis observed on the preoperative radiograph. These findings provide statistical support to the concept that greater degrees of joint space loss correlate with better relief of pain and less severe joint space loss correlates with less relief of pain within the first year after total hip replacement. At 3 years and beyond, hip and pain scores were independent of the degree of preoperative osteoarthritis.

Between 1980 and 1995, 95 consecutive total knee replacements were performed at an average of 10 years 4 months after high tibial osteotomy. The average age of the 82 patients was 66 years, with a preoperative diagnosis of osteoarthritis in 94 knees. One patient died 6 months after surgery. The followup of the remaining 81 patients (94 knees) averaged 8.6 years (range, 2-17 years). Knee Society knee score at final followup improved to an average of 87.6 points from a preoperative average of 38.1 points. No pain was present in 86.2% of knees, and 12.8% of knees had only mild or occasional pain. Tibial radiolucencies were identified in 12 (12.8%) knees at final followup, and in only four knees were radiolucent lines found about the lateral zones. Only one tibial component required revision 3 years after surgery. Although no preoperative factor was identified that predisposed to an inferior knee score, function score, or pain score, the severity of the preoperative flexion contracture and the number of previous surgeries did relate to diminished postoperative motion. However, an increased number of patellar radiolucencies were seen in the knees in which the lateral joint line was raised (referenced from the fibular head) a greater degree. The clinical results of total knee replacement after high tibial osteotomy appeared similar to those of primary total knee replacement. The previous high tibial osteotomy had no adverse effect on the eventual results of a cemented posterior cruciate retaining total knee replacement.

One thousand, one hundred forty-six Anatomic Graduated Component total knee arthroplasties performed between 1987 and 1989 were used to investigate the effects of patellar thickness alone or coupled with lateral retinacular release on initial patellar complications and maximal flexion. Lateral release was found not to be statistically significant regarding radiolucency, patellar prosthesis loosening, or an increase or decrease in flexion. However, total knee arthroplasties in which a lateral release was done, which either saved the superior lateral genicular artery or sacrificed the superior lateral genicular artery, were found to increase the incidence of initial patellar fractures and/or loosening (complications within 1 year) when compared with total knee arthroplasties in which a lateral release was not performed. There was no statistical difference in failure rates regarding fractures and/or loosening of the patella between lateral releases in which the superior lateral genicular artery was saved and the lateral releases in which the superior lateral genicular artery was sacrificed. A difference in postoperative patellar thickness compared with preoperative patellar thickness was found not to be significant to initial patellar fracture and/or loosening, patellar fracture alone, patellar loosening alone, radiolucency, the need for a lateral release, or to an increase or decrease in flexion. Lateral release and patellar thickness had no significant effect on patellar fracture and/or loosening.

Clinical and radiographic data were collected in 139 patients with 195 posterior cruciate retaining total condylar knee prostheses to evaluate the relationship of the proximal tibial resection level with long term results. Among the 139 patients were 75 patients with 106 total knee replacements observed for more than 8 years. All patients underwent biyearly routine examinations, including radiographs and clinical evaluations. The average medial tibial resection for the 139 patients with 195 total knee replacements was 2.95 mm, and in the subset of 75 patients (106 knees) observed for more than 8 years, it was 3.3 mm; both groups had a maximum of 14 mm. Sixty-three percent or 67 knees had medial resection levels of 3 mm or less. The average lateral tibial resection for the 195 knees was 5.48 mm and in the 106 knees was 5.71 mm, with a maximum of 22 mm. Fifty-one percent of 104 knees had lateral resection levels of 5 mm or less. Statistical analysis showed that there was no significant correlation between the level of proximal tibial resection and Knee Society knee score, range of motion, radiolucencies, or loosening or revision. These long term results suggest that minimal proximal tibial resection is not necessary for a successful arthroplasty, and problems associated with minimal resection, such as joint line elevation and thin polyethylene inserts, can be avoided.

Under normal physiologic conditions the level of circulating red blood cells is regulated precisely by the glycoprotein erythropoietin. In major elective surgery, patients who are participating in preoperative autologous blood donation or who are anemic may not have the capacity to manufacture sufficient red blood cells in response to increases in endogenous erythropoietin that is sufficient to avoid perioperative allogeneic blood transfusion. In these patients pharmacologic doses of recombinant human erythropoietin (Epoetin alfa) have been shown to accelerate erythropoiesis, thereby increasing preoperative red blood cell production, hematocrit level, and hemoglobin concentration and reducing exposure to allogeneic blood transfusion. In four large multicenter studies, 869 patients undergoing major elective surgery were treated with a daily regimen (300 or 100 IU/kg x 14 or 15 doses) or a weekly regimen (600 IU/kg x 4 doses) of subcutaneous Epoetin alfa beginning either 2 or 3 weeks before surgery, respectively. Although all Epoetin alfa regimens were effective at accelerating erythropoiesis and increasing red blood cell production, the weekly regimen was the most patient friendly, cost effective regimen for treating preoperative anemia and minimizing patient risk of allogeneic blood transfusion.

Two hundred seventy-nine patients undergoing primary unilateral total knee replacement and 280 patients undergoing primary bilateral total knee replacements were reviewed retrospectively. Patients' height, weight, hemoglobin level before donation, hemoglobin level before surgery, autologous donation, number and type of transfusions whether autologous or allogeneic, and hemoglobin at discharge were collected from hospital and clinic records. The average drop in hemoglobin was 3.85 g/dL in the group of patients undergoing unilateral total knee replacement and 5.42 g/dL in the group of patients undergoing bilateral total knee replacements. The preoperative hemoglobin and blood volume seemed to be very strong, statistically significant predictors of transfusion risk in single and bilateral knee replacements. In unilateral total knee replacement, patients with a hemoglobin of greater than 13 g/dL had only an 8% chance of transfusion and if they donated autologous blood, 66% of the blood was wasted. Preoperative anemia was a strong predictor of transfusion risk in patients undergoing unilateral and bilateral total knee replacements and carried a very high allogeneic transfusion exposure risk, even in patients who had donated blood preoperatively. A nomogram was developed using blood volume and predonation hemoglobin to predict transfusion risk and need to predeposit autologous blood in patients undergoing unilateral and bilateral total knee replacements.

One hundred fifteen patients who underwent total hip replacement for osteonecrosis between June 1972 and April 1990 were divided into 3 groups according to the cause of the disorder: (1) osteonecrosis secondary to alcoholism (21 patients), (2) osteonecrosis secondary to hypersteroidism (29 patients), and (3) idiopathic osteonecrosis (65 patients). To determine the differences in short and long term arthroplasty failure rates, these 3 patient groups were compared with a group of 202 patients who received total hip replacement for osteoarthritis. Statistical analyses were carried out on the following definitions of failure: loosening of the acetabular component, loosening of the femoral component, and revision arthroplasty. Radiolucency and postoperative pain scores also were evaluated. A significant difference in the rate of failure because of loosening of the femoral component was found among the 4 groups. Likewise, a significant difference was found among the 4 groups in all revisions or loosenings or both. However, only the comparison between the idiopathic osteonecrosis and osteoarthritic groups showed a significant difference with survival analysis. Second generation cement technique was as significant as any variable relating to failure. The authors conclude that total hip arthroplasty is an equally viable treatment for the 3 types of osteonecrosis examined in this study; however, failure might be more imminent in studies where larger numbers are needed.

Proximal femoral cortical bone remodeling was evaluated radiographically about a 1 piece cemented titanium alloy femoral prosthesis implanted with modern cement techniques and was compared with one described previously in which early cement techniques and a stainless steel stem were used. Two hundred twenty-six total hip replacements (196 patients) were observed for an average of 6.3 years (range, 5-10 years). Analysis of all hips revealed that the ratio of cortical thickness to that of the overall femoral bone diameter did not change significantly about the periprosthetic bone throughout the length of the study. Cortical hypertrophy and atrophy occurred at rates similar to those seen with the early cement techniques. Distal fusiform cortical hypertrophy and the formation of osteosclerotic (reactive) lines at the bone cement interface occurred at approximately half the rate using modern cement techniques. In addition, cortical atrophy was associated with the formation of these reactive lines, the occurrence of osteolytic lesions, and progressive bone cement interface radiolucencies. Although periprosthetic cortical atrophy occurred at rates similar to those reported previously, important differences were noted between the findings of this study and the earlier study; these differences most likely were a result of cement technique or the prosthesis.

Flat-on-flat, posterior cruciate ligament-sparing total knee prostheses recently have shown problems of wear, loosening, and multiple design changes. Two thousand one Anatomical Graduated Components total knee arthroplasties with compression molded, nonmodular polyethylene tibial components were done between 1983 and 1991 at 3 institutions. All knees were evaluated clinically and radiographically every 2 to 3 years; 71 knees were seen in followup > 10 years. There were 8 failures secondary to revision (5 tibial failures; 2 secondary to metalosis from patellar polyethylene dissociation; and 3 femoral failures) resulting in a 98% survival rate at 10 years. The tibial design was flat-on-flat with a compression molded polyethylene that the authors believe is the primary reason for its success.

Polyethylene wear increasingly has been blamed for osteolysis and granuloma formation after total joint arthroplasty. The authors evaluated the wear difference between bearing surfaces of stainless steel, cobalt chrome, and titanium alloy. They also compared cemented all-polyethylene molded cups with cemented metal-backed molded acetabular cups. These were compared with molded and machined polyethylene cups. Two patient groups were matched individually for gender, age, weight, and length of followup. Analyses were done using the technique of Livermore et al. The bearing surface evaluation consisted of 3 groups after matching, leaving 77 patients per group. Results showed linear wear rates of 0.06 mm per year, 0.05 mm per year, and 0.08 mm per year for stainless steel, cobalt chrome, and titanium alloy, respectively. The comparison between cemented molded metal-backed and nonmetal-backed acetabular components was not matched, with 134 metal-backed and 99 nonmetal-backed components. Results showed linear wear rates of 0.011 mm per year in the metal-backed group and 0.08 mm per year in the nonmetal-backed group. Results were statistically significant. These results indicate that the metal composition of the femoral bearing surface has minimal, if any, effect on the linear polyethylene wear rate. The method of polyethylene fabrication and the use of metal backing had a significant effect on the polyethylene wear rate in these patient groups. These results suggest that the compression-molded all-polyethylene acetabular component may be optimal for reducing polyethylene wear in total hip arthroplasty.

Polyethylene wear debris has been identified as a cause of osteolysis, granuloma formation, and loosening in total hip arthroplasty. This study was designed to evaluate differences in polyethylene wear rates between acetabular cups machined from extruded bar stock and those direct compression molded. Two hundred thirty-six hip prostheses underwent radiographic evaluation using the technique of Livermore et al. Seventy-four were all-polyethylene cups machined from extruded bar stock, and 162 were all-polyethylene cups direct compression molded. Both groups were similar in that the acetabular and femoral components were all cemented, the acetabular components were all polyethylene, nonmetal backed, and bearing surfaces of both groups were polished, cobalt chrome. The femoral components were TRIAD in the machined group and TR28 in the molded group. Patient matching was performed, assigning 54 patients in each group, whose average age was 66 years old, average followup 6.7 years, and average weight 161 pounds. Rates of polyethylene wear then were compared. Results showed a linear wear rate of 0.05 mm per year for compression-molded polyethylene and 0.11 mm per year for machined polyethylene. Results of this study raise questions regarding the types of polyethylene fabrication and its ultimate molecular weight, and wear resistance.

Seven hundred thirty-two total hip replacements performed from 1970 to 1980 were evaluated for the degree of heterotopic bone formation postoperatively and its effect on long-term mechanical loosening. There were 231 Charnley total hip replacements, of which 152 had no heterotopic bone formation, 58 had Grade 1 formation, and 21 had Grade 2 or 3 formation. Among the 123 Mueller total hip replacements, 98 had no heterotopic bone formation, 19 had Grade 1 formation, and 6 had Grade 2 or 3 formation. For the 378 T-28 total hip replacements, there were 305 with no heterotopic bone formation, 59 with Grade 1 formation, and 14 with Grade 2 or 3 formation. Survival analyses using the definition of failure as loosening, fracture, or revision of the acetabulum or femoral components were constructed. There was no correlation between mechanical loosening, fracture, or revision of the total hip replacement and any degree of heterotopic bone formation.

From 1975 to 1983, 278 patients received 418 posterior cruciate ligament-retaining Total Condylar knee arthroplasties. Twenty-four patients were excluded, 15 for lack of followup data, 6 for infection during followup, and 3 for revision surgeries for previous infections. The 394 remaining knees were observed from 1 to 18 years (mean, 8.08 years). Kaplan-Meier and crude survival estimates at 12 years were 96.8% and 98.1%, respectively. Various survival analyses by other authors have yielded similar successful results.

Four hundred twenty-one posterior cruciate condylar total knee arthroplasties were performed between 1975 and 1983. Anatomic alignment of the knee was recorded on follow-up evaluations from two months to 13 years postoperatively. Patients were stratified into a normal group that was 5 degrees to 8 degrees anatomic valgus, a varus group that was from 4 degrees anatomic valgus to any degree of varus, and a valgus group that was more than 9 degrees anatomic valgus. There were eight failures, five in the varus group and three in the normal group. There were no failures in the valgus group. Kaplan-Meier survival curves showed no significant difference between normal and valgus groups; however, there was a statistical difference between the valgus and varus and the normal and varus groups. A surgeon should align a total knee prosthesis in neutral or a slight amount of anatomic valgus to give the patient the best chance for long-term survival.

The accuracy of intramedullary (IM) versus extramedullary (EM) distal femoral alignment systems was compared in 200 consecutive total knee replacements (TKRs) on standing full-length lower-extremity roentgenographs. Intramedullary femoral alignment systems were used in 125 TKRs and an EM system was used in 75 TKRs. All tibial cuts were made using an EM tibial cutting guide. Roentgenographic measurements of (1) femoral-tibial angle, (2) distal-femoral resection angle, (3) proximal-tibial resection angle, (4) joint line orientation, (5) physiologic femoral valgus, and (6) distance of the lower-extremity mechanical axis from the center of the knee were made. No significant intragroup differences were seen in the average values obtained for each of the six roentgenographic measurements. However, the percentage of distal-femoral resections outside the accepted normal range (94 degrees-100 degrees) was higher in the EM group (28%) versus the IM group (14.4%) at p = 0.019. Likewise, the percentage of joint line orientations outside the desired normal range was higher in the EM groups when compared with the IM group (21.3% versus 11.2%, p = 0.052). A disturbing number of proximal-tibial resection angles were inaccurate in both groups. Improper tibial cuts were seen in 20.6% of Group 1 and in 24% of Group 2 when an EM tibial cutting guide was used. A range of distal-femoral cuts exists when using either an IM or an EM femoral alignment guide. This study demonstrated a statistically significant improvement in distal-femoral resection accuracy when using an IM femoral alignment system. Methods of improving proximal-tibial bone resections are needed.(ABSTRACT TRUNCATED AT 250 WORDS)

Seventy-two cementless tricompartmental total knee arthroplasties were performed in 47 patients using a porous-coated prosthesis without screw fixation for the tibial components between 1984 and 1986. These individuals were observed at regular intervals for a minimum of three years. Their Hospital for Special Surgery pain and function scores as well as roentgenographic signs of anatomic alignment and subsidence were evaluated at six months, one year, and three years postoperatively. The roentgenographic evaluation for subsidence looked at a measurable difference in the anteroposterior roentgenograph on the medial and lateral plateaus and on the lateral roentgenograph anteriorly and posteriorly. Early postoperative interpretations have suggested pain and knee scores to be much lower than scores in the cemented prosthesis. Reassessment after three years, however, revealed no further deterioration of the noncemented prosthesis in respect to knee scores and survival analysis. Roentgenographic analysis showed no correlation between subsidence and alignment alterations, subsidence and time, or subsidence and pain. It appears that after an initial period of discomfort, the noncemented knee can achieve a functional, clinical, and roentgenographic result much better than previously anticipated. The consequences beyond this time period still remain unknown.

Thirty bilateral-paired cruciate-retaining and cruciate-substituting total knee arthroplasties (TKAs) were evaluated two to five years after surgery. In general, the more deformed knees received the cruciate-substituting prosthesis. Preoperative Hospital for Special Surgery knee scores averaged 56.4 (range, 44-68) in the cruciate-retaining knees and 53.3 (range, 29-69) in the cruciate-substituting knees. Postoperatively, 25 patients were observed climbing stairs. All patients were scored and asked their preference of knees. Fifteen patients handled stairs normally. Five patients climbed stairs favoring the cruciate-substituting knee and four the cruciate-retaining knee. One patient favored one knee ascending and the other descending. In the cruciate-substituting knees, there were 27 excellent and three good knee scores. There were 28 excellent and two good knee scores in the cruciate-retaining knees. Ten patients preferred the cruciate-retaining knee, eight preferred the cruciate-substituting knee, and 12 had no preference. In this group of patients no clinical advantage of one type of TKA over the other was observed.

The results of total knee arthroplasty in patients with osteonecrosis of the medial femoral condyle were examined using Kaplan-Meier survival analysis. The study included 32 osteonecrotic knees with an average final follow-up examination of 3.9 years. For comparison, 63 osteoarthrotic knees with an average final follow-up examination of 4.6 years were also analyzed. The survival rates were calculated using four distinct categories of failure: (1) revision, (2) revision or radiolucency, (3) revision, radiolucency, or pain, and (4) pain. On the basis of pain relief alone, the five-year postoperative success rate was 82% for osteonecrosis (eight knees) and 90% for osteoarthrosis (27 knees), with no significant statistical difference between the two groups.

A retrospective analysis of 144 total knee arthroplasties was performed between 1975 and 1981 with a minimum follow-up period of seven years. A posterior cruciate condylar prosthesis was used in each procedure. Patients were followed clinically and roentgenographically, and a set of statistical variables was established based on elevation in joint line, tibial component angular alignment, overall limb alignment, and position of the tibial component on anteroposterior and lateral roentgenograms. Review of the study group found that the Hospital for Special Surgery knee scores improved from a preoperative score of 55 to a postoperative score of 88, with 94.5% having good or excellent results. The mean postoperative range of motion was 106 degrees with a mean extension of -0.3 degrees. Radiolucencies developed in 41% of the knees with 5% of the knees having progressive radiolucencies. Eight knees were considered failures based on clinical and roentgenographic evaluations. Factors found to significantly affect the formation of radiolucent lines included a shift of the tibial component medially by greater than 4 mm, a varus tilt of the tibial component greater than 2 degrees, and the diagnosis of rheumatoid arthritis. The only variable associated with aseptic loosening was an elevation of the joint line by greater than 8 mm.

Forty-eight patients treated by primary bilateral simultaneous total knee arthroplasty, in which one knee had a lateral release and the other did not, were evaluated clinically and roentgenographically from one to 12 years postoperatively. Thirty of these patients also had a technetium-99 bone scan. Mean clinical scores at the last follow-up examination were 90 for both groups. Roentgenographically, there were no subluxations, dislocations, or fractures in either group. There were two metal-backed patellae (one in each group) with signs of polyethylene wear and developed debris. Bone scans showed no difference between the two groups and no signs of osteonecrosis of the patella.