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Biomedical subjects

R H Emerson

Publications and source records attributed to R H Emerson.

At least 19 recordsLinked to original sources
PubMed2001

A new method of trochanteric fixation after osteotomy in revision total hip arthroplasty with a calcar replacement femoral component.

Two series of cementless revision hip arthroplasties, using a transtrochanteric approach and an identical calcar replacement femoral prosthesis, were compared to ascertain the rate of trochanteric union and device problems. The failed implants removed at the time of revision were short-stemmed cemented or cementless designs in comparable patient populations. Eighteen patients had a traditional wiring fixation with a 72% union rate, and 111 patients had a bolt-and-plate fixation device, when it became available, that transfixed the trochanter to the lateral side of the femur through the proximal femoral component. The rate of union here was 94%. Of 111 bolt-and-plate devices, 13 (11.7%) were radiographically loose, although asymptomatic with a united osteotomy. Two bolts of the first-generation design broke, with 1 needing removal. Two bolt-and-plate devices disassembled, with 1 needing removal.

Adult↗
PubMed2001

A titanium cementless calcar replacement prosthesis in revision surgery of the femur: 13-year experience.

From January 1987 through December 2000, 1,179 cementless calcar prostheses were implanted at the Texas Center for Joint Replacement. The prosthesis is titanium, has proximal circumferential plasma-spray coating, and is designed for proximal bone loading. The average follow-up for the entire series was 6.2 years, and the projected stem survivorship at 13 years is 95.2%. There have been 9 stem revisions for loosening. When mechanical loosening alone is evaluated, the projected stem survivorship is 99%. There have been 56 revisions in the entire series. Prosthetic survivorship for the entire patient population is projected at 93.6% at 13 years. There have been no cases of distal lysis or late loosening. None of the prostheses are classified as loose at this time, and none are classified as stable fibrous fixation.

Adolescent↗
PubMed2000

Restoration of bone stock in revision surgery of the femur.

Three hundred and four femoral revisions were performed from 1987 to the end of 1990. All were done with cementless titanium calcar replacement prostheses, designed for proximal bone loading. Type III bone deficiencies were present in 160 femurs, all requiring supplemental cortical bone plates for bony augmentation. All grafts united and provided increased bone stock in the long term. Physiologic loading is important for graft remodeling and maturation. Hip scores have improved from an average Harris Hip Score of 44 to 84. Current survivorship at 10 years is 96%, and the revision rate is 3.2%. Thigh pain is mild in 3% of cases. There have been no late failures or distal lysis noted to date.

Animals↗
PubMed2000

The AGC total knee prosthesis at average 11 years.

A retrospective study of a series of 126 consecutive primary cemented total knee replacements using the AGC prosthesis is reported. Sixty-two knees were available for long-term review with an average clinical follow-up of 11.4 years (range, 8.4-13.6 years). The survivorship was 95%, defining the endpoint as revision of all components for any reason except sepsis. The average knee flexion was 110.9 degrees. The average Knee Society score was 91, and the average Knee Society Functional score was 67. There was no finding of tibial polyethylene failure, wear debris-generated osteolysis, or tibial or femoral loosening. Seven metal-backed patellae developed wear-through at an average of 80.4 months (7 of 126 for a 5.5% failure rate), with 3 (2.3%) resulting in complete revision. The authors continue to use the AGC prosthesis with an all-polyethylene patella. Compared with historical controls, the AGC has comparable survivorship.

Biomechanical Phenomena↗
PubMed1999

Structural bone grafting for femoral reconstruction.

Structural grafting for femoral reconstruction has been used in femoral revision surgery in connection with partial bone loss. In patients in whom the proximal femur is compromised significantly circumferentially, or is entirely absent, segmental proximal femoral allografts are indicated. Onlay cortical allografts have been used to supplement bone stock when the intact femur has advanced noncircumferential deficiencies attributable to osteoporosis, osteolysis, or other causes. The procedure using proximal femoral allografts was performed in 262 patients from 1983 to 1997. Satisfactory results were obtained in 85% of the patients. More than 1000 cortical onlay bone plate allografts were performed from 1984 to 1997. Detailed information was obtained on 251 patients who underwent surgery from 1984 to 1990. These constructs reliably united with the host bone and increased bone mass long-term.

Arthroplasty, Replacement, Hip↗
PubMed1999

Effect of circumferential plasma-spray porous coating on the rate of femoral osteolysis after total hip arthroplasty.

BACKGROUND: Osteolysis of the femur has been a serious problem associated with some designs of total hip-replacement implants; it frequently leads to failure of the femoral component. We evaluated the effect of a circumferential plasma-spray porous coating on the rate of osteolysis in a study that included two groups of hips, each of which received an implant with the same design except for the extent of the porous coating. Our goal was to determine the possible role of circumferential porous coating in protecting the bone-implant interface from osteolysis. METHODS: A series of consecutive primary total hip replacements performed with insertion of the Mallory-Head implant without cement was divided into two study groups. The first 126 hips (Group 1) were treated with a femoral stem that had a noncircumferential plasma-spray porous titanium coating. The next ninety hips (Group 2) were treated with a circumferentially coated stem of the same design. The average duration of radiographic follow-up was 7.8 years in Group 1 and 7.5 years in Group 2. RESULTS: The average rate of polyethylene wear was similar for the two groups (0.187 millimeter per year in Group 1 and 0.189 millimeter per year in Group 2). The prevalence of osteolysis in Group 1 (40 percent; fifty of 126 hips) was significantly higher than that in Group 2 (10 percent; nine of ninety hips) (p < 0.001). Osteolysis remote from the joint space (distal to zones 1 and 7) was found in 11 percent (fourteen) of the hips in Group 1 but in none of those in Group 2 (p = 0.0004). The average total area of osteolysis in Group 1 (5.0 square centimeters) was significantly larger than that in Group 2 (2.9 square centimeters) (p < 0.05). CONCLUSIONS: A circumferential plasma-spray titanium porous coating on the femoral component of a total hip-replacement prosthesis inserted without cement appears to provide an effective barrier preventing wear debris from gaining access to the endosteal surface of the femur and the greater trochanter. This finding supports the hypothesis of the so-called effective joint space, which predicts that wear debris from the joint bearing can migrate, driven by intracapsular pressures, to all areas to which joint fluid has access and thus can result in osteolysis. The reduction of the prevalence of osteolysis and the elimination of osteolysis from the zones remote from the joint space by the use of a circumferential plasma-spray porous coating indicates that the femur was effectively sealed off from the joint space. We believe that the durability and longevity of the femoral component should be enhanced by the use of such a coating.

Coated Materials, Biocompatible↗
PubMed1999

Surgical closing in total knee arthroplasty. A series followup.

The benefits of closing the surgical wound of a primary and revision total knee prosthesis with the knee in full flexion are examined. A previous study showed that surgically closing the primary knee arthroplasty with the knee in full flexion produced significantly more postoperative flexion at 6 months: 114.7 degrees compared with 108.1 degrees. Of 108 selected sequential primary knee arthroplasties, the first 52 knees were closed surgically with the leg in full knee extension, and the second 56 knees were closed in 90 degrees to 110 degrees flexion, depending on the available motion of the joint. The patients in each group were matched closely in age, weight, height, gender, and surgical technique. At all followup intervals, the flexion measurements were significantly better in the flexion closure group. At 1 year, the flexion group had 117.9 degrees and the extension group had 112.9 degrees flexion. The revision series also was a selected sequential series with 13 knees in each closure group. In the revision case, the 1-year findings were similar, with significantly more knee flexion in the flexion closure group (118.7 degrees compared with 112.7 degrees). In matched groups, flexion closure in primary and revision knee replacements significantly increased total range of motion, as seen at the 1-year followup.

Aged↗
PubMed1998

Onlay cortical allografting for the femur.

Failed femoral total hip replacement components are frequently associated with bone loss. At the time of revision surgery, the goals are to create a construct that relieves pain, is stable, and preserves and enhances bone stock. This article discusses Materials and Methods, Indications, Operative Technique, and Results regarding onlay cortical allografting for the femur.

Arthroplasty, Replacement, Hip↗
PubMed1996

Clinical and radiographic outcome of a cementless, titanium, plasma spray-coated total hip arthroplasty femoral component. Justification for continuance of use.

Between 1984 and 1986, 177 nonconsecutive, primary total hip arthroplasties were performed in 150 patients using the Mallory-Head Porous femoral component (Biomet, Warsaw, IN) inserted without cement. Average time to follow-up evaluation for the entire population (including all early revisions) was 76 months (6.3 years). There were 10 revisions (6%) with an average time to revision of 50 months (4.2 years). Two revisions were for component undersizing; three revisions were for aseptic loosening; four revisions were for acetabular component failure and one revision was due to a femoral fracture secondary to trauma. At the most recent follow-up visit, the average Harris hip score for all hips increased from 41.5 before surgery to 86.8 (P < .001). Radiographic assessments yielded an average Engh fixation score of 20.7. The Kaplan-Meier survival estimate for the average time to follow-up evaluation was 0.98. Based on our patient selection criteria and excellent intermediate clinical and radiographic results, the initial design strategies of the Mallory-Head Porous femoral prosthesis have been confirmed.

Adolescent↗
PubMed1996

Surgical closing in primary total knee arthroplasties: flexion versus extension.

One hundred eight consecutive patients with primary osteoarthritis of the knee undergoing primary arthroplasty were compared retrospectively to determine whether surgical closure of the entire wound in flexion has any effect on range of motion postoperatively over a period of up to 6 months. The knees of the first 52 patients were surgically closed in extension. In the second group of 56 patients, the knees were closed in 90 degrees to 110 degrees flexion depending on the available motion of the joint. Although the patients were not randomized, the groups were closely matched in age, weight, height, and gender. Preoperative and postoperative patellar heights were similar in both groups. The patients were started on a continuous passive motion device in the recovery room. At all intervals the flexion measurements were significantly better in the flexion closure group. By 6 months the flexion closure group had surpassed their preoperative measurements, whereas the extension closure group had not yet achieved this goal. The flexion group required less home physical therapy than the extension group. Closing the knee in flexion permits the patients to regain knee motion faster with less effort, thereby saving money and enhancing patient satisfaction.

Aged↗
PubMed1995

Dealing with the deficient acetabulum in revision hip arthroplasty.

Variable bone loss is the defining feature of the failed acetabulum. Preoperative planning must include an assessment of the extent of bone deficiency. When bone loss precludes a routine revision there are three reconstructive options, a small cup in the false acetabulum, reconstruction of the lost bone with an allograft, and a jumbo cup filling the expanded acetabulum. The investigators have found that the latter technique can often be used in the setting of the difficult acetabulum with improvement in hip mechanics and avoiding a structural bone graft. When a graft is necessary, the best technique is a small graft and large fixed cup, with support of both the cup and graft on as much host bone as possible. A posterior buttressing plate should be considered for any graft providing substantial posterior support of the acetabular component.

Acetabulum↗
PubMed1995

Titanium as the material of choice for cementless femoral components in total hip arthroplasty.

Modern total hip arthroplasty has been performed using femoral stems manufactured from stainless steel, cobalt-chrome molybdenum alloy (CoCrMb), titanium aluminum vanadium alloy (TiAlV), and, on a limited basis, low-elastic modulus composites. Today, only CoCrMb and TiAlV are used in significant numbers. There is ample theoretical, experimental, and clinical evidence to support Ti-AlV as the material of choice for cementless femoral stems, based on superior mechanical compatibility and biocompatibility. The primary advantage of TiAlV over CoCrMb is a lower modulus of elasticity. This results in decreased stress shielding and subsequent favorable femoral remodeling. This effect is more significant with the smaller stem sizes used in primary surgery but persists even with larger stem sizes used in revision surgery. The second advantage of TiAlV is its biocompatibility. Titanium aluminum vanadium alloy is of relatively low toxicity in concentrations found clinically, and TiAlV is inert in the physiologic environment. With regard to fixation in cementless total hip arthroplasty, TiAlV has been shown to achieve excellent bone ingrowth into porous surfaces. In addition, there is evidence of superior bony ingrowth into TiAlV as compared with CoCrMb. Titanium aluminum vanadium alloy is presently the material of choice to be used in conjunction with hydroxyapatite coating. Prosthetic design, stem diameter, and porous-coating applications play significant roles in bony response regardless of metal composition.

Biocompatible Materials↗