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Biomedical subjects

M L Olmstead

Publications and source records attributed to M L Olmstead.

At least 19 recordsLinked to original sources
PubMed1995

Canine cemented total hip replacements: state of the art.

Total hip replacements in the dog have become well established over the past 20 years as an effective method for treating disabling hip conditions. A fixed head prosthesis has been the mainstay during most of this period. Return to normal function with this prosthesis has been reported at 95 per cent. Although patient selection, pre- and post surgical care, the surgical technique and the treatment or prevention of complications has been continually improved, it was not until recently that the prosthesis and its instrumentation were improved. Now a modular prosthesis with improved instrumentation gives the veterinary surgeon state of the art' implants and instruments. The prosthesis is easier to implant, the surgeon has greater flexibility in surgery and improved results are expected. Total hip replacement continues to be an effective way to give dogs a pain-free, mechanically sound hip joint.

Animals↗
PubMed1993

The use of orthopedic wire as a lateral suture for stifle stabilization.

Extracapsular suture stabilization is a long-accepted technique for stabilization of cranial cruciate deficient stifles in small-breed dogs. Use of stainless steel wire as the suture material in the extracapsular technique extends the procedure to use in many large breed dogs and is currently the author's surgery of choice. The surgical technique and illustrative cases are described.

Animals↗
PubMed1991

Fracture complications. An overview.

No surgical procedure is free of complications. Determining the reason that a complication of a fracture repair occurred and developing a treatment plan are important if the objectives of fracture treatment are to be met. It is also necessary to deal with owners, and, sometimes, other veterinarians in meeting these objectives.

Animals↗
PubMed1991

Complications of fractures repaired with plates and screws.

The complications associated with bone plates and screws often are related to undersized or oversized implant selection, improper number of implants, inadequate or improper screw fixation, malpositioned plates or screws, poor plate contouring, and failure to use cancellous bone grafts when a gap is present at the fracture site. A thorough understanding of the principles of plate and screw application helps to avoid most problems. The surgeon must use an implant that will stabilize the fracture adequately during the healing process. The patient's activity levels must not exceed the mechanical limits of the implant. Methods to promote bone healing, such as using cancellous bone grafts when a deficit is present, help to protect the implant from fatiguing before the fracture is healed. Proper positioning and contouring of the implants are important to the successful application of plates and screws. It must be realized that even if all of these things are done, some complications still will occur. When that happens, the complication should be dealt within a manner that will allow the objectives of fracture treatment (a healed bone and normal limb function) to be achieved.

Animals↗
PubMed1989

Mechanical properties of primate vascularized vs. nonvascularized patellar tendon grafts; changes over time.

Mechanical properties of patellar tendon autografts used to replace the anterior cruciate ligament (ACL) in the cynomolgus monkey were measured at four time periods up to 1 year. The ACL was replaced in each knee with the medial half of the patellar tendon: as a vascularized graft (VG) on one side and as a nonvascularized or free graft (FG) on the other. Postoperative care consisted of 4 weeks of cast immobilization at 30 degrees flexion followed by unrestricted activity in a large cage. Both grafts showed low stiffness and maximum force at 7 weeks (24% and 16% of ACL control values, respectively), increasing to 57% of control ACL stiffness and 39% of control maximum force by 1 year. Corresponding material properties, modulus and maximum stress, also increased over time, but at 1 year were only 34% and 26% of ACL values, respectively. The results indicate that retaining vascularity does not prevent significant reduction in graft properties that occur postoperatively, nor does it accelerate the return in strength and stiffness. Tissue stiffness, which returns earlier than maximum force and joint anteroposterior (AP) force displacement data, should be routinely reported in any healing study. Finally, in studies of this kind, the large variation in the results makes sampling only one or two animals from each time period unreliable.

Animals↗
PubMed1987

Brucella canis osteomyelitis in two dogs with total hip replacements.

Brucella canis was isolated from the cement or bone surrounding a hip prosthesis after total hip replacement was performed for treatment of hip dysplasia in 2 dogs. Lameness or signs of infection were not evident for 9 and 16 months after surgery. Osteomyelitis surrounding the prostheses was detected radiographically only after the lameness developed. The origin of the B canis infection in the 2 dogs was believed to be hematogenous because of the biologic behavior of this organism and because of the duration of excellent limb function after hip replacement. A slide agglutination test for B canis should be performed as a screening test on any canine total hip candidate when the anamnesis and physical examination indicate that the dog may have been exposed to or infected with B canis.

Animals↗
PubMed1987

Total hip replacement.

Total hip replacement in the dog has proved to be a highly successful method of restoring normal, pain-free motion to the coxofemoral joint. In a prospective study done at The Ohio State University College of Veterinary Medicine and the Berwyn Veterinary Associates Hospital, the indications and contraindications, the most effective surgical technique, the complication rate, and the long-term functional evaluation have been established for canine total hip replacements. This study has established that a 95 per cent success rate for function of the hip joint can be achieved if the established guidelines are followed.

Animals↗
PubMed1986

[Replacement of the hip joint in the dog].

Hundreds of total hip replacements in dogs have been performed at the Ohio State University of Veterinary Medicine since August 1976. Dogs with disabling diseases or conditions of the hip are candidates for the THR. The technique provides the dog with a pain free, mechanically sound ball and socket joint. The most commonly encountered complication is dislocation, while the most disastrous complication is infection. Complications can be minimized through adherence to detail during the procedure. By following strict aseptic principles, surgical technique and postoperative care, successful hip function has been achieved in 94.7% of the cases.

Animals↗
PubMed1982

Fracture-associated sarcoma in the dog.

Seven fracture-associated sarcomas developed in large-breed dogs after stabilization of comminuted long bone fractures with stainless steel plates and screws. In most cases, the healing pattern of the fractures was disturbed. The mean interval between fracture occurrence and tumor diagnosis was 5.5 years. Radiographically, the sarcomas were typified by smooth-bordered subperiosteal proliferation and soft tissue mineralization. Cortical destruction was variable. Several histologic subtypes of osteosarcoma were seen. Four sarcomas had a marked inflammatory cell component and 5 of the dogs had clinical evidence of chronic infection. These findings were similar to those in 35 previously reported fracture-associated sarcomas, even though many types of fixation devices in addition to plates, as well as no fixation at all, were represented in these cases. Fracture-associated sarcomas most frequently were found to be diaphyseal, and the femur accounted for almost half of the sarcomas reported.

Animals↗
PubMedDate not supplied

Evaluation of risk factors for luxation after total hip replacement in dogs.

OBJECTIVE: To identify risk factors for luxation after canine total hip replacement (THR). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: 256 client-owned dogs that underwent THR. METHODS: Patient data surveyed included signalment, body weight, diagnosis, prior hip surgery, implant size, intraoperative complications, and angle of lateral opening of the acetabular component. RESULTS: Postoperative complications were recorded in 20 cases (7.8%). The most common complication was dorsal luxation which occurred in 12 dogs (4.7%). The interval between joint replacement and luxation ranged from 1 to 116 days (mean, 44 days). In 1 case, luxation was attributable to failure of the repair of an intraoperative fracture of the greater trochanter. Excluding this case, the mean angle of lateral opening in those dogs that sustained luxation was 62 degrees (range, 46 degrees - 75 degrees). The mean angle of lateral opening overall was 48 degrees (range, 18 degrees - 76 degrees). The angle of lateral opening was the only factor that had a statistically significant effect on whether luxation occurred (P = .035). Acetabular revision, performed primarily to reduce the angle of lateral opening, was performed in 8 dogs and successfully prevented subsequent luxation. CONCLUSION: Luxation of the prosthesis is substantially under the control of the surgeon. It is recommended that the acetabular cup be inserted at an angle of lateral opening of 35 degrees to 45 degrees. In those cases of THR luxation in which an inappropriate angle of lateral opening is identified, acetabular revision arthroplasty generally results in a good clinical outcome.

Acetabulum↗
PubMedDate not supplied

In vitro evaluation of antibiotic elution from polymethylmethacrylate (PMMA) and mechanical assessment of antibiotic-PMMA composites.

OBJECTIVE: To determine whether different methods of sterilization of antibiotic vials or the heat of polymerization altered the antimicrobial activity or mechanical properties of antibiotic/polymethylmethacrylate (PMMA) composites when compared to antibiotic-free PMMA. STUDY DESIGN: In vitro study. METHODS: Steam-sterilized, gas-sterilized, and non-sterilized 1 gram vials of cefazolin and injectable gentamicin sulfate (high and low doses) were mixed with PMMA to prepare composites for antibiotic elution evaluation, compression, and elongation testing. Blocks of PMMA that contained antibiotic were assayed for antibacterial activity using an agar gel diffusion method or were placed in phosphate buffered saline (PBS) to assess elution of antibiotic. Phosphate buffered saline samples from steam-sterilized cefazolin and high-dose gentamicin groups were assayed on days 1, 2, 5, and 9 for cefazolin or gentamicin concentration by high-pressure liquid chromatography or fluorescent polarization immunoassay, respectively. RESULTS: PMMA blocks containing antibiotic inhibited bacterial growth of Staphylococcus aureus 25923 for an average of 9 days. Cefazolin and gentamicin concentration in PBS decreased dramatically after the first 24 hours, but remained above minimum inhibitory concentration (MIC) throughout the experiment for all groups except low-dose gentamicin. Compressive strength of plugs made from plain cement and plugs made from PMMA mixed with untreated and steam-sterilized cefazolin was similar, but was significantly different from the other groups. There appeared to be an inverse relationship between compressive strength and elongation. CONCLUSION: PMMA/antibiotic composites inhibited bacterial growth for 7 to 10 days. Compressive strength was affected by different additions of antibiotic. CLINICAL RELEVANCE: Bacteria introduced during a surgical procedure may be inhibited by elution of antibiotic from PMMA at the time of contamination.

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PubMedDate not supplied

Radiographic evaluation of acetabular component position in dogs.

OBJECTIVE: To assess the usefulness of standard radiographic projections for determining acetabular cup position and to compare 2 radiographic methods for calculation of the angle of lateral opening of the acetabular cup. STUDY DESIGN: In vitro radiographic study. METHODS: Acetabular components were mounted on a custom-built inclinometer. The effect of varying the angles of lateral opening, inclination, version, and centering of the x-ray beam on the radiographic appearance of the cup was investigated. The angle of lateral opening was calculated trigonometrically after direct measurement and by means of computer-aided image analysis. RESULTS: Using a ventrodorsal radiograph, the computer-aided measurement of angle of lateral opening was accurate to within 5 degrees when the true angle of lateral opening was > or = 40 degrees. In the case of direct measurement, the calculated angle was accurate to within 5 degrees only when the true angle was > or = 60 degrees. An increasing angle of inclination was associated with reduced accuracy of calculation of the angles of lateral opening and version. Standard radiographic assessment of acetabular version and inclination was not found to be clinically useful. The displacement of the x-ray beam, which would cause significant error in the determination of lateral opening, is unlikely to be exceeded in practice. Cup size had no significant effect on the accuracy of the results. CONCLUSIONS: Computer-aided image analysis can be used to calculate angles of lateral opening to within 10 degrees throughout the range of acetabular positions seen in practice and is appropriate for postoperative documentation of cup position. The angles of inclination and version should be interpreted with caution.

Acetabulum↗