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Biomedical subjects

R F Kyle

Publications and source records attributed to R F Kyle.

At least 19 recordsLinked to original sources
PubMed1999

Infection after total knee arthroplasty. A retrospective study of the treatment of eighty-one infections.

BACKGROUND: The clinical presentation of an infection at the site of a total knee arthroplasty can be used as a guide to treatment, including the decision as to whether the prosthesis should be retained or removed. We reviewed the results of treatment of infection after total knee arthroplasty to evaluate the effectiveness of four treatment protocols based on the clinical setting of the infection. METHODS: We retrospectively evaluated the results of treatment of eighty-one infections in seventy-six consecutive patients who either had an infection after a total knee arthroplasty or had multiple positive intraoperative cultures of specimens of periprosthetic tissue obtained during a revision total knee arthroplasty performed because of presumed aseptic loosening. The patients were managed according to one of four protocols. Five infections in five patients who had positive intraoperative cultures were treated with antibiotic therapy alone. Twenty-three early postoperative infections in twenty-one patients were treated with débridement, antibiotic therapy, and retention of the prosthesis. Twenty-nine late chronic infections in twenty-eight patients were treated with a delayed-exchange arthroplasty after a course of antibiotics. Seven acute hematogenous infections in six patients were treated with débridement, antibiotic therapy, and retention of the prosthesis. Seventeen infections in seventeen patients were not treated according to one of the four protocols. Sixteen late chronic infections were treated either with an arthrodesis (five infections) or with débridement, antibiotic therapy, and retention of the prosthesis (eleven infections). One acute hematogenous infection was treated with resection arthroplasty because of life-threatening sepsis. RESULTS: The mean duration of follow-up was 4.0 years (range, 0.3 to 14.0 years). Eleven patients who had an arthrodesis, a resection arthroplasty, or an above-the-knee amputation after less than two years of follow-up were included in the study as individuals who had a failure of treatment. In the group of patients who were managed according to protocol, the initial course of treatment was successful for all five infections that were diagnosed on the basis of positive intraoperative cultures, five of the ten deep early infections, all thirteen superficial early infections, twenty-four of the twenty-nine late chronic infections, and five of the seven acute hematogenous infections. Only one of eleven prostheses in patients who had a late chronic infection that was not treated according to protocol was successfully retained after débridement. CONCLUSIONS: Our treatment protocols, which were based on the clinical setting of the infection, were successful for most patients. A major factor associated with treatment failure was a compromised immune status. Bone loss and necrosis of the soft tissues around the joint also complicated the treatment of these infections.

Aged↗
PubMed1998

Blood conservation in hip trauma.

Patients with hip or pelvic fractures experience significant blood loss as a result of the fracture and from the surgery that subsequently is performed. The emergent and unplanned nature of fracture surgery precludes the use of preoperative blood donation and the optimization of chronic medical problems. Blood transfusion frequently is required to maintain adequate tissue O2 delivery in these injured patients. However, the administration of allogeneic blood causes other problems, including a well documented increase in the risk of infectious complications. Perioperative measures to minimize blood loss such as hypotensive anesthesia and red blood cell salvage are important, but often are inadequate to prevent the need for blood transfusion. Recently, erythropoietin therapy has been shown to stimulate hematopoiesis in patients with hip fractures. The authors discuss their experience with blood loss management in these patients with hip injuries, including aggressive Fe replacement therapy and the use of recombinant human erythropoietin.

Blood Loss, Surgical↗
PubMed1998

A parametric study of acetabular cup design variables using finite element analysis and statistical design of experiments.

To isolate the primary variables influencing acetabular cup and interface stresses, we performed an evaluation of cup loading and cup support variables, using a Statistical Design of Experiments (SDOE) approach. We developed three-dimensional finite element (FEM) models of the pelvis and adjacent bone. Cup support variables included fixation mechanism (cemented or noncemented), amount of bone support, and presence of metal backing. Cup loading variables included head size and cup thickness, cup/head friction, and conformity between the cup and head. Interaction between and among variables was determined using SDOE techniques. Of the variables tested, conformity, head size, and backing emerged as significant influences on stresses. Since initially nonconforming surfaces would be expected to wear into conforming surfaces, conformity is not expected to be a clinically significant variable. This indicates that head size should be tightly toleranced during manufacturing, and that small changes in head size can have a disproportionate influence on the stress environment. In addition, attention should be paid to the use of nonmetal backed cups, in limiting cup/bone interface stresses. No combination of secondary variables could compensate for, or override the effect of, the primary variables. Based on the results using the SDOE approach, adaptive FEM models simulating the wear process may be able to limit their parameters to head size and cup backing.

Acetabulum↗
PubMed1998

Forces required to initiate sliding in second-generation intramedullary nails.

Second-generation intramedullary nails, which allow the fixation screw that is placed in the femoral head to slide distally and thus allow compression of the fracture of the femoral neck, have become a popular option for the treatment of ipsilateral fractures of the femoral neck and shaft. However, the sliding characteristics of the screw within the barrel of the nail or the side-plate have not been assessed biomechanically, to our knowledge. The goal of the current study was to investigate the forces required to initiate sliding of the proximal screw in intramedullary devices and to compare these forces with those required to initiate sliding of hip screws. The loading configuration simulated the typical angle of 135 degrees between the intramedullary nail and the proximal screw. The forces required to initiate sliding of the proximal screw, with the screw extended fifty-one, seventy-six, eighty-six, and 102 millimeters beyond the proximal end of the barrel, were measured for three different types of second-generation intramedullary nails (Recon, ZMS, and Gamma), a sliding compression hip screw, and an intramedullary hip screw, and these forces were then compared. With each amount of extension of the screw, the hip screws required lower forces to initiate sliding than did the second-generation intramedullary devices. Of the second-generation devices, the Gamma nail required the highest forces to initiate sliding; the Recon and ZMS nails required 20 to 40 percent lower forces compared with the Gamma nail. None of the devices jammed in any of the loading configurations that were tested. When the extension of the screw was increased, higher forces were required to initiate sliding.

Biomechanical Phenomena↗
PubMed1998

Norian SRS cement augmentation in hip fracture treatment. Laboratory and initial clinical results.

Bone quality, initial fracture displacement, severity of fracture comminution, accuracy of fracture reduction, and the placement of the internal fixation device are important factors that affect fixation stability. New high strength cements that are susceptible to remodeling and replacement for fracture fixation may lead to improved clinical outcome in the treatment of hip fractures. Norian SRS is an injectable, fast setting cement that cures in vivo to form an osteoconductive carbonated apatite of high compressive strength (55 MPa) with chemical and physical characteristics similar to the mineral phase of bone. It can be used as a space filling internal fixation device to facilitate the geometric reconstruction, load transfer, and healing of bone with defects and/or fractures in regions of cancellous bone. Furthermore, this cement can improve the mechanical holding strength of conventional fixation devices. Use of this material potentially could improve fracture stability, retain anatomy during fracture healing and improve hip function, thus achieving better clinical outcomes. In vivo animal studies have shown the material's biocompatibility, and cadaveric studies have shown the biomechanical advantage of its use in hip fractures. Initial clinical experience (in 52 femoral neck fractures and 39 intertrochanteric fractures) showed the potential clinical use of this innovative cement in the treatment of hip fractures.

Aged↗
PubMed1997

Decision making errors in the use of interlocking tibial nails.

Seventy-one fractures of the tibial shaft were treated with interlocking intramedullary nails. None of the fractures were treated with static locking of the intramedullary nails. These 71 fractures were studied to determine whether certain fracture patterns are prone to loss of alignment when static interlocking is not used. Loss of alignment was defined as shortening of 1 cm or more and/or change in angulation of at least 5 degrees. Loss of alignment occurred in eight of the 71 (11%) fractures. Shortening and/or angulation occurred in seven of 22 spiral and short oblique fractures, and in none of 27 transverse fracture patterns. It was concluded that the dynamically locked and nonlocked modes of intramedullary nailing should not be used in the stabilization of spiral and oblique fractures of the tibial shaft.

Adolescent↗
PubMed1996

Periprosthetic metastatic carcinoma. Pitfalls in the management of two cases initially diagnosed as osteolysis.

Periprosthetic osteolysis is a well-described phenomenon associated with total hip arthroplasty. Two cases are presented in which apparently healthy patients developed lytic lesions adjacent to cementless hip implants. Despite atypical features, the lesions were initially attributed to wear debris-induced osteolysis, and it was discovered during revision surgery that metastatic tumor was present. For one patient, if the initial diagnosis had been correct, subsequent surgery and related complications may have been avoided. It is important to consider the entire differential of radiolucent bone lesions whenever a patient presents with periprosthetic osteolysis. If revision surgery is not warranted on the basis of loosening, then a thorough medical examination, close follow-up evaluation, and/or biopsy should be performed to rule out metastatic disease.

Adenocarcinoma↗
PubMed1996

Noncemented femoral components in total hip arthroplasty for patients with rheumatoid arthritis.

Twenty-seven patients with rheumatoid arthritis underwent cementless total hip arthroplasty from 1982 through 1989. We performed all operations through a posterior approach. Postoperatively, patient convalescence consisted of ambulation with crutches, followed by weight bearing as tolerated until pain and discomfort subsided. We contacted 25 (92.5%) patients for follow-up. Combined, these patients received 34 total hip arthroplasties. The patients ranged in age from 14 to 69 years old with a mean age of 42.9 years. The follow-up period ranged from two to eight years with a mean of five and one-half years. The mean preoperative total Harris hip score was 48 (range 31-68). The mean total Harris hip score at latest follow-up was 80 (range 44-95). Hip pain status and functional ability were important indicators of treatment efficacy. The lower incidence of pain, as well as the increase in functional abilities experienced by the patients, suggests that cementless total hip arthroplasty is a preferable alternative to fixed arthroplasty in patients with rheumatoid arthritis.

Adolescent↗
PubMed1995

Fractures of the proximal part of the femur.

The orthopaedic surgeon has a multitude of internal fixation devices and techniques available for use in the treatment of subtrochanteric fractures of the proximal femur. The successful use of second-generation locking nails is technically demanding. Close attention to positioning of the patient, reduction of the fracture, placement of the guide-wire, and insertion of the nail and of the proximal and distal locking screws is mandatory. The newer, high-strength hip-screws allow good fixation of a fracture that extends into the piriformis fossa. If medial comminution is present, this technique is best performed in conjunction with indirect reduction and bone-grafting. With proper technique, these devices allow the surgeon to manage predictably a complex subtrochanteric fracture that previously had to be treated with traction or extensive dissection and with (frequently inadequate) internal fixation.

Adult↗
PubMed1991

Biomechanical characteristics of interlocking femoral nails in the treatment of complex femoral fractures.

Interlocking intramedullary (IM) nails allow more comminuted and proximal or distal femoral fractures to be successfully treated than previously possible with routine IM nailing. Autopsy specimens were prepared to evaluate the effectiveness of different locking mechanisms on fracture site stability. Grosse-Kempf (GK) and Brooker-Wills (BW) IM nails were inserted in anatomic specimen femurs with transverse fractures and 1-, 2-, and 3-cm defects. The femurs were loaded in four-point bending, and bending stiffness was calculated. The femurs were also loaded in torsion, and the amount of slippage between the nail and bone (at 10 Nm of applied torque) was measured. The GK nail, fully interlocked, had the lowest amount of rotational slip, followed by the BW and the GK noninterlocked nail. Bending stiffness was not significantly different for these IM nails.

Biomechanical Phenomena↗
PubMed1989

The effects of femoral head size on the deformation of ultrahigh molecular weight polyethylene acetabular cups.

Late loosening of cemented acetabular cups is increasingly being recognized as a clinical problem. One of the factors which may contribute to loosening is high localized deformation and stress at the cement-bone interface, the magnitude of which depends on the size of the total hip replacement (THR) femoral head. The effects of varying the femoral head size, from 22 to 32 mm, on strain values measured on the surface of the cup were investigated using experimental stress analysis techniques. The largest absolute strains were recorded when loading with the 22 mm head size. Peak strain values decreased to a minimum with the 26 mm head size and increased steadily with head sizes beyond 26 mm. The selection of an acetabular cup size and corresponding femoral head size in a total hip arthroplasty should not be an arbitrary one, but should be based on scientific studies which indicate minimum states of stress within the cup and cement mantle, as well as clinical evidence that the combination of components shows a reduced incidence of failure. This study experimentally quantifies the states of stress on the surface of the acetabular cup and points to the possible existence of an optimum component size to minimize surface stress.

Acetabulum↗
PubMed1989

Rationale, experience, and results of long-stem femoral prosthesis.

A long, curved-stem, uncemented femoral component was evaluated for use in primary and revision hip arthroplasty in young patients aged 43.5 years (range, 16-60 years). The femoral component has a proximal wedge shape and a medial collar for proximal press fit and load transfer; anterior and posterior ingrowth pads; anteverted head and neck; and a long, anatomically curved intramedullary stem for distal stability. In testing the contribution of the long, curved stem to the torsional stability of uncemented prostheses by comparing it with other stems, the long, curved stem was the most stable, followed by a shorter straight stem, and a short, proximally curved stem. If the long, and a short, proximally curved stem. If the long, curved stem is incrementally shortened by 1.5-7.5 cm, the initial torsional stability is reduced in proportion to the amount of shortening. Geometrically, for a given patient, the stem-bone contact (and thus the distal stability) is increased when a larger stem is inserted. Clinically, Harris hip scores in 69 hips followed for five to seven years (average patient age, 43.5 years) improved from 52.6 to 92.0 at last follow-up evaluation. The femoral component revision rate was 2.9%, the acetabular rate was 8.9%, and bipolar revision rate was 3.1%, for a combined rate of 12%.

Adolescent↗
PubMed1988

Comparative analysis of ankle arthroplasty versus ankle arthrodesis.

In a retrospective study of 41 patients with total ankle arthroplasty (25 patients) and ankle arthrodesis (18 patients), the mean follow-up period was 3.8 years for total ankle arthroplasties and 3.3 for ankle arthrodeses. Sixteen of the 23 ankle arthroplasty patients, and 17 of the 18 arthrodesis patients had good or excellent results. Total ankle arthroplasty was successful in patients with rheumatoid arthritis, but not posttraumatic arthrosis. Total ankle arthroplasty is indicated in rheumatoid patients with severe ankle involvement who have not responded to medical management. It also may be used in the elderly or debilitated patients who will place minimal stress on the ankle. The elderly may not tolerate the prolonged immobilization or repeated operations that fusion may require. Total ankle arthroplasty should not be used in young patients with posttraumatic arthrosis.

Adult↗
PubMed1985

Biomechanics of intramedullary fracture fixation.

Intramedullary rodding allows excellent control of bending forces on long bone fractures when adequate sized rods are used. This is made possible by reaming when necessary. Torsional stability is poor if adequate bone nail contact is not obtained and there is little bone fragment interdigitation. This can be optimized with the interlocking system, especially with proximal and distal fractures. Intramedullary rods allow transmission of compressive load so there must be adequate bone to bone contact without comminution to prevent shortening. If a great deal of comminution is present, an interlocking system must be used to resist compressive loads. The interlocked devices have not been proven to be a detriment to union and indeed are a semi-rigid fixation system when used in comminuted shaft fractures. The strength of an osteosynthesis with an intramedullary rod depends on the geometry of the rod and the geometry of the fracture complex. Both locked and nonlocked intramedullary rods perform extremely well when one understands the mechanical principles involved in intramedullary rodding and pays close attention to detail.

Biomechanical Phenomena↗