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Biomedical subjects

E M Keating

Publications and source records attributed to E M Keating.

At least 73 records · Page 4Linked to original sources
PubMed1993

Polyethylene wear in total hip arthroplasty in patient-matched groups. A comparison of stainless steel, cobalt chrome, and titanium-bearing surfaces.

Osteolysis and component loosening secondary to polyethylene (PE) debris are of paramount concern to today's joint replacement surgeon. This retrospective clinical study measures linear wear in 568 implanted total hip prostheses in which three different metals were used as bearing surfaces (307 stainless steel T-28 [Zimmer, Warsaw, IN], 162 cobalt chrome Tr-28 [Zimmer], and 99 nonion implanted titanium Miami Orthopedic Surgical Consultants [Biomet, Warsaw, IN] prostheses) implanted by a single surgeon over an 8-year period. The acetabular component in all cases was nonmetal-backed compression-molded PE, and all components were cemented. Linear wear was measured using the radiographic technique described by Livermore et al. (The effect of femoral head size on wear of the polyethylene acetabular component. J Bone Joint Surg 72A:518, 1990) in which change in acetabular component thickness is determined from serial radiographs. A separate evaluation of this technique confirmed accuracy to within 0.18 mm. Radiographs were also evaluated for femoral and acetabular radiolucencies, femoral subsidence, and osteolysis. Patients were matched for sex, age, weight, and length of follow-up period to eliminate these retrospective variables for comparison of wear. The patient-matched groups consisted of 77 patients from each group (43 women, 34 men) with the following demographics: age, 66 years; weight, 158.9 lbs.; follow-up period, 7.9 years. Results revealed linear wear rates of 0.06 stainless steel, 0.05 cobalt chrome, and 0.08 titanium in the patient-matched groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Polyethylene wear in cemented metal-backed acetabular cups.

We examined radiographic polyethylene wear in 233 cemented total hip arthroplasties (201 patients) with either a metal-backed or a non-metal-backed acetabular cup. All patients had identical cemented one-piece titanium femoral stems with a femoral head diameter of 28 mm. The mean linear wear rate was 0.11 mm/yr in metal-backed sockets and 0.08 mm/yr in non-metal-backed sockets (p = 0.0002). The mean volumetric wear rate was 66.2 mm3/yr in the metal-backed sockets and 48.2 mm3/yr in the polyethylene sockets (p = 0.0002). The addition of metal backing to a cemented acetabular cup therefore resulted in a 37% increase in mean polyethylene wear rates which may partially explain the higher failure rate of cemented metal-backed cups. Linear regression analysis also implicated increased follow-up time (log), gross acetabular migration, metal backing and male gender in increasing polyethylene wear. We advocate the use of an all-polyethylene cup in cemented total hip arthroplasty. The increased polyethylene wear must also cause concern about the wear rate of uncemented metal-backed acetabular sockets.

Acetabulum↗
PubMed1993

Revision total hip arthroplasty using ultrasonically driven tools. A clinical evaluation.

A three-center clinical evaluation of the use of ultrasonic instrumentation for cement removal during 90 revision total hip arthroplasties was undertaken. In conjunction with hand tools, cement removal was facilitated with ultrasonic tools. Superficial bone burns were seen in eight cases (9%). Bone perforations were created with ultrasonic tools in three cases (4%)--two followed perforations already created by hand tools in the proximal metaphyseal area. Only one perforation (1%) was made in the shaft of the femur. Ultrasonic instrumentation is a valuable adjunct for cement removal in revision total hip arthroplasty.

Acetabulum↗
PubMed1993

Use of lateral heel and sole wedges in the treatment of medial osteoarthritis of the knee.

The authors discuss the use of lateral heel wedges in the treatment of medial osteoarthritis of the knee in 121 knees in 85 patients. Follow-up was an average of 12 months after the insertion of the wedge. Patients' roentgenograms were graded according to the Ahlback classification, and various improvements were noted. Overall, 38% of patients improved to a Hospital for Special Surgery pain score of 25 or 30, which corresponds to an excellent result from total knee arthroplasty. Fifty percent of patients improved to a pain score of 20 or higher, which corresponds to a good result from total knee arthroplasty. The patients with milder osteoarthritis received greater pain relief. However, even patients with complete loss of joint space and bony erosion showed some improvement. It appears that the use of lateral wedges has a place in the conservative treatment of medial osteoarthritis.

Adult↗
PubMed1993

Intramedullary versus extramedullary femoral alignment systems in total knee replacement.

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)

Biometry↗
PubMed1992

The effect of preoperative knee deformity on the initial results of cruciate-retaining total knee arthroplasty.

Between November 1985 and June 1987, 751 posterior cruciate-sparing total knee arthroplasties were performed on 523 patients who exhibited fixed varus or valgus deformities. Patients excluded from this study included the following: those with a postoperative follow-up period of less than 2 years (including patients who had died), patients who became infected, and patients with previous failed total knee arthroplasty in the same knee. A total of 473 knees left for evaluation. All arthroplasties were measured using anatomic axis for alignment measurement. The Hospital for Special Surgery scoring system was used to determine the clinical scores prior to the end of each follow-up examination. All ligament releases were performed sequentially, including balancing of the posterior cruciate ligament. All arthroplasties were divided into six separate groups depending upon the degree of varus or valgus deformity. Kaplan-Meier curves were constructed using three methods of failure definition. Curves were then compared between groups. The mean Hospital for Special Surgery score was no different between any of the groups, except for the group of 6 degrees-10 degrees varus, which was significantly higher than the mean score of the 11 degrees and higher valgus group. All other groups were the same statistically. It is concluded that severe varus and valgus deformities may be satisfactorily corrected with the use of a cruciate-retaining type of total knee arthroplasty.

Adult↗
PubMed1992

Influential factors in cemented acetabular cup loosening.

To delineate further the cause of acetabular loosening in a group of 238 total hip arthroplasties performed between 1980 and 1982, the authors subjected those total hip arthroplasties to a multifactorial analysis utilizing the log normal model. Data collected on each patient consisted of age, sex, weight at the time of surgery, diagnosis, cement thickness between zones 1 and 2 and between zones 2 and 3, polyethylene thickness, lateral tilt, and metal backing of the acetabular components. The acetabulum was considered a failure by radiographic loosening with migration greater than 5 mm, revision in patients younger than 60 years of age (P = 0.154), or when the acetabular cup was metal-backed (P = .001).

Aged↗
PubMed1992

The biomechanical evaluation of intramedullary nails in distal femoral shaft fractures.

The biomechanical parameters (torsional rigidity and compressive strength) for three different intramedullary femoral nails, Küntscher (K), Brooker-Wills (BW), and Küntscher Interlocking (KI) were compared in this study. Fractures were created in the femoral shaft distal to the isthmus with sections removed so that pure torsional rigidity and resistance to compression could be measured. The standard K nail provided no torsional rigidity and only minimal resistance to longitudinal compression. The KI was significantly more rigid under compression than either the BW or the K. In torsional resistance the K nail was significantly weaker than either the BW or KI. The K nail does not provide significant resistance to compression or torsion for use in oblique or comminuted fractures. The BW nail probably provides enough resistance to rotation for use in distal fractures, but probably does not provide enough resistance to compression for use in fractures that are prone to shortening.

Biomechanical Phenomena↗
PubMed1991

The total condylar III knee prosthesis in elderly patients.

Sixteen knee arthroplasties using a total condylar III prosthesis were performed in 14 patients with an average follow-up period of 4.5 years and a minimum follow-up period of 3 years. Eleven of the sixteen knee arthroplasties were revision prostheses. The average age was 71 year, with all but three patients being 69 years of age or older. In this age group, fifteen of sixteen implants had a good to excellent Hospital for Special Surgery (HSS) knee score at the most recent follow-up evaluation. One patient had a fair score, the result of a remote postoperative proximal tibial fracture, and requires a long leg brace for ambulation.

Aged↗
PubMed1991

Revision total knee arthroplasty. A survival analysis.

The results of revision total knee arthroplasty (TKA) have been documented reasonably well in the literature. It is notable, however, that none of these reports have used the technique known as survival analysis to compare virgin and revision arthroplasties. This technique has an advantage over conventional analyses because it does not exclude patient data for inadequate follow-up study or patient death. In this study, survival analysis was applied to 37 revision TKAs performed exclusively by the senior author. With failure defined as removal of the prosthesis, revision surgeries experienced a 97.0% survival rate at 6 years. The secondary arthroplasty demonstrated a significantly lower survival rate than the index procedure over a period of approximately 6 years.

Actuarial Analysis↗
PubMed1991

Trochanteric fixation by cable grip in hip replacement.

We used the stainless steel cable grip system described by Dall and Miles in 1983 to fix trochanters in 40 hips after total arthroplasty with trochanteric osteotomy. The cable broke in 32.5% of the hips; the trochanter failed to unite in 37.5%. Significantly more cables broke when placed inside the femoral canal than when the cable was placed round the femoral shaft (58% as against 9.5%, difference p less than 0.01). The high incidence of breakage may have resulted from contact between the stainless steel cable and the titanium prosthesis, from the acute angulation, or because of the lower fatigue strength of stainless steel. Better results have been obtained using cables with a higher fatigue strength, passed outside the proximal femur.

Adult↗
PubMed1991

Early clinical results of hydroxyapatite-coated total hip arthroplasty.

A retrospective clinical and radiographic review of 25 conventional cementless total hip replacements (THRs) and 25 cementless hydroxyapatite-coated THRs was performed to evaluate early postoperative results. The hydroxyapatite-coated group had a higher incidence of pain-free arthroplasties compared with the standard cementless group (72% v 44%, P = .045) at the 2-month postoperative evaluation. At the 6-month evaluation, 76% of hydroxyapatite-coated THRs were pain-free compared with 52% of conventional cementless THRs, although the statistical significance disappears (P greater than .05). No differences between groups existed in the 6-month Harris hip scores, average motion, use of external support, Trendelenberg gait, postoperative implant radiolucent lines. Adding a 50- to 75-mug hydroxyapatite coating to a proximal one-third porous femoral prosthesis and porous surface acetabular cup improved the early clinical results in cementless THR. Whether this improvement in pain scores reflects a more stable cementless prosthesis via increased rates and amount of osseus ingrowth or adjunctive bone hydroxyapatite chemical bonding remains unanswered. Long-term follow-up of femoral subsidence and THR revision is needed to indicate the durability and success of hydroxyapatite coating.

Adult↗
PubMed1991

Survival analysis of total condylar-type prostheses.

Between 1975 and 1983, 280 patients received 422 posterior cruciate ligament-retaining total condylar knee arthroplasties. Fifty-nine were excluded for one of the following reasons: previous total knee replacement, follow-up less than 1 year, or infection at any time during the life of the prosthesis. The 363 remaining knees were observed from 1 to 13 years (mean, 6.86). Kaplan-Meier and "crude" survival estimates at 12 years were 94.7% and 96.6%, respectively. Results of various survival analyses by other authors yield similar successful results.

Follow-Up Studies↗
PubMed1991

The effect of miscellaneous invasive procedures on subsequent total knee arthroplasty.

Invasive orthopedic procedures were performed on 112 joints that underwent total condylar knee arthroplasty between November 1975 and February 1987. These knees were divided into six categories based on the most traumatic surgical procedure the patients had experienced. The six classifications were total knee arthroplasty, proximal tibial osteotomy, fracture fixation, patellectomy, arthroscopy, and debridement. Each group of knees was compared with the 579 primary arthroplasties performed during the same time period. The only group in which results were significantly less favorable than those of the virgin joints was the previous total arthroplasty category. All other surgical classification groups had knee scores, radiolucency frequencies, and ranges of motion comparable with those of the primary replacement surgeries. When surgical techniques are modified to insure proper soft tissue alignment, patients who have undergone previous invasive procedures on their knees can expect highly favorable results from total joint arthroplasty.

Arthroscopy↗
PubMed1991

Unwashed filtered shed blood collected after knee and hip arthroplasties. A source of autologous red blood cells.

We evaluated the results of twelve hematological and plasma protein determinations in 450 to 500-milliliter volumes of shed blood that had been collected with or without acid-citrate-dextrose anticoagulant (National Institutes of Health Formula A) from knees and hips during the first twelve hours after arthroplasty. We also evaluated the effects on the recipients when the blood was used for reinfusion. The findings in the units that had been obtained in less than four hours, in between four and six hours, and in more than six hours after the arthroplasty were similar whether or not the acid-citrate-dextrose anticoagulant had been used. The mean values for the collected units were: in the blood, a concentration of hemoglobin of 115 grams per liter, a hematocrit of 0.34, a white blood-cell count of 4.8 x 10(9) per liter, and a red blood-cell count of 3.7 x 10(12) per liter, and, in the plasma, a level of hemoglobin of 160 grams per liter, a level of fibrinogen of less than 0.2 gram per liter, a level of factor-V clotting protein of less than 10 per cent of normal, a level of factor-VIII clotting protein that was 45 per cent of normal, a level of antithrombin III that was 45 per cent of normal, a level of plasminogen that was 55 per cent of normal, a level of protein C that was 100 per cent of normal, and a level of fibrin-degradation products of 1000 micrograms per milliliter of plasma. The clinical response of the patient was assessed after the reinfusion of a total of 205 units of unwashed shed blood into 153 patients. In addition, in 126 of the 153 patients, hematological and plasma-protein measurements were analyzed before the autotransfusion and one and twenty-four hours afterward. Each of these patients had received one to four units of shed blood that had been filtered but not washed. Only two (2 per cent) of the ninety-nine patients who received shed blood that had been collected six hours or less after the operation had a febrile reaction, whereas twelve (22 per cent) of the fifty-four patients who received blood that had been collected six to twelve hours after the operation had such a reaction.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗