Marvin L. Olmstead

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.

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 authors surgery of choice. The surgical technique and illustrative cases are described.

An experimental animal model of aseptic loosening of hip prostheses in sheep to study early biochemical changes at the interface membrane

BackgroundAseptic loosening of hip prosthesis as it occurs in clinical cases in human patients was attributed to wear particles of the implants, the response of the tissue dominated by macrophages and the production of inflammatory mediators and matrix degrading enzymes; however, the cascade of events initiating the process and their interaction regarding the time course is still open and discussed controversially. Therefore, the goal of this study was to establish an experimental animal model in sheep allowing to follow the cascade of early mechanical and biochemical events within the interface membrane and study the sequence of how they contribute to the pathological bone resorption necessary for aseptic loosening of the implant.MethodsA cemented modular system (Biomedtrix) was used as a hip replacement in 24 adult Swiss Alpine sheep, with one group receiving a complete cement mantle as controls (n = 12), and the other group a cement mantle with a standardized, lateral, primary defect in the cement mantle (n = 12). Animals were followed over time for 2 and 8.5 months (n = 6 each). After sacrifice, samples from the interface membranes were harvested from five different regions of the femur and joint capsule. Explant cell cultures were performed and supernatant of cultures were tested and assayed for nitric oxide, prostaglandin E2, caseinolytic and collagenolytic activity. RNA extraction and quantification were performed for inducible nitric oxide synthase, cyclooxygenase-2, interleukin 1, and interleukin 6. Overall differences between groups and time periods and interactions thereof were calculated using a factorial analysis of variance (ANOVA).ResultsThe development of an interface membrane was noticed in both groups at both time points. However, in the controls the interface membrane regressed in thickness and biological activity, while both variables increased in the experimental group with the primary cement mantle defect over time. Nitric oxide (NO) and PGE2 concentrations were higher in the 8.5 months group (P < 0.0001) compared to the 2 months group with a tendency for the unstable group to have higher concentrations. The same was true for collagenolytic activity (P = 0.05), but not for caseinolytic activity that decreased over time (P < 0.0001).ConclusionIn this study, a primary cement mantle defect of the femoral shaft elicited biomechanical instability and biochemical changes over time in an experimental animal study in sheep, that resembled the changes described at the bone cement-interface in aseptic loosening of total hip prosthesis in humans. The early biochemical changes may well explain the pathologic bone resorption and formation of an interface membrane as is observed in clinical cases. This animal model may aid in future studies aiming at prevention of aseptic loosening of hip prosthesis and reflect some aspects of the pathogenesis involved.

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 patients 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.

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.

Comparison of the effects of two screw insertion patterns on bone fragment translocation in a 3.5 mm dynamic compression plate and a 3.5 mm limited-contact dynamic compression plate.

OBJECTIVE To compare the effects of screw insertion pattern, plate type, application of bone reduction forceps, and additional load screw insertion in an 8-hole 3.5 mm dynamic compression plate (DCP) and limited-contact dynamic compression plate (LC-DCP) on bone fragment translocation (BFT) in a fracture gap model. STUDY DESIGN In vitro mechanical study. METHODS Two screw insertion patterns were tested in the DCP and newly redesigned LC-DCP using gap model synthetic bone constructs. In Pattern 1, screws were first inserted into the holes at each end of the plate, then screws were inserted into the holes adjacent to the fracture gap. In Pattern 2, screws were only inserted into the holes adjacent to the fracture gap. The effects of tight or loose bone forceps securing the plate, loosening a neutral screw in Pattern 1, and inserting up to 4 additional load screws with each pattern were tested. Changes in the fracture gap were measured after insertion of all neutral screws and after each load screw. RESULTS Pattern 2 BFT was significantly greater than Pattern 1 BFT when bone forceps were loose with both plates (P < .001). In the DCP, the BFT was significantly increased by loosening the bone forceps with Pattern 2 (P < .001) and by loosening 1 neutral screw in Pattern 1 (P < .001). The BFT for each additional load screw inserted was significantly less than 1.0 mm. CONCLUSIONS A tight neutral screw in the same bone fragment as the load screw or bone clamps that tightly secure the plate to the bone can limit BFT.