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Biomedical subjects

S A Olson

Publications and source records attributed to S A Olson.

At least 19 recordsLinked to original sources
PubMed1997

Statically equivalent load and support conditions produce different hip joint contact pressures and periacetabular strains.

The hip is a common site of orthopaedic trauma and disease, and considerable research has been directed toward understanding the development of contact pressures within the joint. Virtually all experimental studies to date have employed proximal femurs compressed along the joint reaction force vector into acetabulae explanted from cadaver pelves. This approach presumes that deformations of the acetabulum are highly localized, and that the pelvis is functionally a rigid body. We have developed a methodology that uses intact pelves loaded through simulation of the abductor mechanism. A direct comparison of the two techniques revealed significantly different joint contact characteristics and periacetabular strains. Fuji film measurements of contact area and pressure were more widely distributed across the acetabulum for the intact pelvis, with significant pressure development in anterior and posterior regions. Contact patterns in the explanted acetabulae were concentrated in the superior portion of the joint. Principal strains from three rosette gages placed near the acetabular rim were also significantly different for the two testing techniques, but were not substantially altered by the presence of Fuji film within the joint. The results indicate that deformation of the entire pelvis and the manner in which loads are applied significantly affect development of contact pressures within the hip joint, and that Fuji film is a suitable technique for recording those patterns.

Acetabulum↗
PubMed1997

Reamed femoral nailing in patients with multiple injuries. Adverse effects of tourniquet use.

Limb reperfusion after tourniquet ischemia causes pulmonary microvascular injury. Similarly, microembolization, like that associated with reamed femoral nailing, can induce pulmonary microvascular injury. Both processes result in increased pulmonary capillary membrane permeability and edema. However, the association between femoral nailing followed by tourniquet ischemia and clinical lung injury has not been described. The authors reviewed 72 patients with femoral shaft fractures and tibial or ankle fractures requiring internal fixation between 1987 and 1993. All femoral shaft fractures were treated with reamed intramedullary nails. Patients were divided into groups, based on whether the tibial or ankle injury was managed surgically with (Group T, 34 patients) or without (Group NT, 38 patients) a tourniquet. Group T was subdivided based on tourniquet time: T1, less than or equal to 90 minutes; T2, greater than 90 minutes. Groups were matched for injury severity. Group NT had fewer ventilator dependent days and intensive care days than Group T (NT: ventilator dependent days, 2.5 +/- 5.2; intensive care days, 3.9 +/- 6.5; T: 5.1 +/- 6.4; intensive care days, 6.7 +/- 6.6). Ventilator dependent days and intensive care days increased with increasing tourniquet time (T1: ventilator dependent days, 3.2 +/- 3.6; intensive care days, 5.4 +/- 4.6; T2: ventilator dependent days, 7.5 +/- 8.5; intensive care days, 8.5 +/- 8.5), suggesting that in patients with multitrauma, combining reamed femoral nailing with fracture fixation under tourniquet control increases pulmonary morbidity. Further investigation to measure pulmonary injury associated with ischemia reperfusion and intramedullary nailing in patients with multitrauma is warranted.

Adult↗
PubMed1997

Nonreamed locking intramedullary nailing for open fractures of the tibia.

The use of nonreamed interlocking tibial nails in the management of open fractures of the tibial shaft has gained wide acceptance. This technique has been reported to have reproducible good results with a low incidence of complications in Type I, Type II, and Type IIIA open tibial shaft fractures. The use of nonreamed nails in Type IIIB fractures continues to be a source of controversy. The treatment of 72 open fractures of the tibial shaft with nonreamed interlocking intramedullary nailing is detailed. There were 27 Type I, 22 Type II, 11 Type IIIA, and 12 Type IIIB open tibial shaft fractures. There were three (4.2%) deep infections; one Type II, one Type IIIA, and one Type IIIB. Forty-nine fractures (68%) united by 6 months, all fractures had united by 12 months. The use of nonreamed locking intramedullary nailing in Types I, II, IIIA, and IIIB open fractures of the tibial shaft is supported.

Adolescent↗
PubMed1997

Biomechanics of the hip joint and the effects of fracture of the acetabulum.

The biomechanical analysis of the normal and arthritic hip joint have been the subject of numerous publications in orthopaedics. Biomechanical investigations focusing on the effect of fractures of the acetabulum on the alteration of hip joint mechanics have been a recent development. This paper outlines currently available methodologies for simulating load across the hip, and as measuring articular contact and contact stresses. Results of investigations of posterior wall fractures and transverse fractures of the acetabulum are presented. Directions for future research in the area of mechanical investigations of acetabular fractures are discussed.

Acetabulum↗
PubMed1997

Diagnosis and management of closed internal degloving injuries associated with pelvic and acetabular fractures: the Morel-Lavallée lesion.

Closed internal degloving is a significant soft-tissue injury associated with a pelvic trauma in which the subcutaneous tissue is torn away from the underlying fascia, creating a cavity filled with hematoma and liquefied fat. It commonly occurs over the greater trochanter but may also occur in the flank and lumbodorsal region. When this closed internal degloving occurs over the greater trochanter, it is known as a Morel-Lavallée lesion. We reviewed 24 patients who sustained a closed internal degloving injury. Cultures from the closed internal degloving injury were positive in 46% (11 of 24 cases). The incidence of positive cultures was not dependent on the time from injury to debridement. All wounds were treated by thorough debridement before or during pelvic or acetabular surgery. Three patients subsequently developed deep-bone infections, only one of whom had a positive culture at the initial debridement. One patient whose wound was primarily closed over suction drains developed a chronic deep soft-tissue infection requiring multiple debridements. The development of hematoma in the zone of operation reduces the safety of early operative intervention by increasing the risk of infection. An expanding hematoma in a closed internal degloving injury may further compromise the skin vascularity if not promptly drained. The injured soft tissues should be debrided early, either before or at the time of fracture fixation. The wound should be left open, and repeated surgical debridement of the injured tissue is recommended.

Acetabulum↗
PubMed1997

Amputation versus limb salvage.

The decision to attempt salvage or to amputate a severely injured leg in among the most difficult that the orthopaedist must face. Even surgeons with tremendous trauma experience cannot agree on standard course of action. In the face of such injuries, physician consultation regarding the treatment decision, including all of those members of the team that are needed for a successful salvage, is necessary. In the best circumstances, the trauma surgeon, vascular surgeon, orthopaedist, and a soft-tissue specialist are all involved. From a psychological perspective, the timing of an amputation is important. Although each patient's case is unique, immediate amputation is often viewed by the patient and family as a result of the injury. Conversely, a delayed amputation may be viewed as a failure of treatment. It is imperative that the surgeon have a detailed discussion with the patient and the family whenever possible before making the decisions. Scoring systems are of some help in estimating the chances of a successful salvage. However, the ultimate decision to amputate or attempt salvage is based on such patient factors as preinjury function and social situation, and of associated injuries, surgeon experience, available resources, projected physical abilities, and the patient's projected physical requirements. These decisions are difficult and tax the judgment and emotions of the patient, family, and physician.

Adult↗
PubMed1996

Assessment of pelvic ring stability after injury. Indications for surgical stabilization.

The indications for surgical stabilization of pelvic ring injuries are based on an assessment of the extent of disruption of the pelvic ring and the associated deformity of the bony pelvis. The relevant anatomy and biomechanics or the pelvis, pelvic ring injury classifications, initial assessment, and emergent treatment of patients with pelvic ring injuries is reviewed, and a discussion or indications for surgical stabilization of pelvic ring disruptions is presented.

Biomechanical Phenomena↗
PubMed1996

The effect of variable size posterior wall acetabular fractures on contact characteristics of the hip joint.

The indications for open reduction and internal fixation of posterior wall acetabular fractures associated with a clinically stable hip joint are unclear. In previous work a large posterior wall defect (27% articular surface area) resulted in significant alteration of load transmission across the hip; specifically, there was a transition from evenly distributed loading along the acetabular articular surface to loading concentrated mainly in the superior portion of the articular surface during simulated single leg stance. However, the majority of posterior wall fractures involve a smaller amount of the articular surface. Posterior wall acetabular fractures not associated with instability of the hip are commonly treated nonoperatively. This practice does not account for the size of the posterior wall fracture. To study the biomechanical consequences of variably sized articular defects, a laboratory experiment was conducted evaluating three progressively larger posterior wall defects of the acetabulum during simulated single leg stance using superlow Fuji prescale film (Itochu International, New York): (a) 1/3 articular surface width through a 50 degrees arc along the posterior wall of the acetabulum, (b) 2/3, and (c) 3/3 articular width defects through the same 50 degrees arc along the posterior wall of the acetabulum. In the intact acetabulum, 48% of the total articular contact was located in the superior acetabulum. Twenty-eight percent of articular contact was in the anterior wall region of the acetabulum and 24% in the posterior wall region. After the 1/3 width posterior wall defect, 64% of the articular contact was located in the superior acetabulum (p = 0.0011). The 2/3 width posterior wall defect resulted in 71% of articular contact area being located in the superior acetabulum (p = 0.0006). After the 3/3 width posterior wall defect, 77% of articular contact was located in the superior acetabulum, significantly greater than the intact condition (p < 0.0001) and 1/3 width defect (p = 0.0222). The total absolute contact areas for all defect conditions were significantly less than the intact conditions. The results of this study reconfirm the observation that posterior wall fractures of the acetabulum significantly alter the articular contact characteristics in the hip during single leg stance. The relationship between defect size and changes in joint contact showed that the smallest defect resulted in the greatest alteration in joint contact areas, whereas larger defects resulted in minor increments of change in contact area. This finding is of concern because the clinical practice of managing acetabular fractures nonoperatively if the hip joint is stable is based on the supposition that the joint retains enough integrity to function without undue risk of late posttraumatic osteoarthritis. A better understanding of the natural history of stable posterior wall acetabular fractures is needed to ascertain whether some of these fractures merit operative repair.

Acetabulum↗
PubMed1996

Removal of intramedullary nails from the femur: a review of 45 cases.

The excellent biocompatibility of titanium and its alloys may result in osseointegration. In order to determine if this presents an obstacle to removal of intramedullary nails, we retrospectively reviewed a series of 45 cases of isolated removal of a femoral nail. Indications for removal were persistent pain and discomfort, request of an asymptomatic patient, or skeletal immaturity. Twenty-three nails were titanium, and 22 were stainless steel. Although removal of the titanium nails had a significantly longer operative time (110 vs. 84 min), analysis of variance indicated that this was due to a greater number of crosslocking screws in the titanium nails (2.2 vs. 0.6) and a tendency to set the titanium nails deeper in the femur. The use of the titanium material per se did not pose a risk factor for difficulty in late removal of an intramedullary nail.

Adult↗
PubMed1995

Anatomy of the medial distal femur: a study of the adductor hiatus.

The proximity of the vascular structures traversing the adductor hiatus in the medial distal femur is a potential concern for the surgeon. The distance from the adductor tubercle to the adductor hiatus was measured in both lower extremities in 24 skeletally mature cadavers. This distance ranged from 8.0 to 13.5 cm (mean 10.0). The area up to 8 cm proximal to the adductor tubercle, anterior to the medial intermuscular septum, appears to be a safe interval for avoiding vascular structures with percutaneous or limited open surgeries of the medial aspect of the distal femur.

Cadaver↗
PubMed1995

Biomechanical consequences of fracture and repair of the posterior wall of the acetabulum.

We measured the distribution of contact area and pressure between the acetabulum and the femoral head of cadaveric pelves in three different conditions: intact, with an operatively created fracture of the posterior wall, and after anatomical reduction and fixation of the fracture with a buttress plate and interfragmentary screws. The study involved eight cadaveric hip joints from five pelves loaded to 2000 newtons in simulated single-limb stance. Measurements were made with pressure-sensitive film. The acetabulum was divided into three areas--the anterior wall, the superior aspect, and the posterior wall--for the analysis of the data. Creation of a fracture of the posterior wall was followed by an increase in contact area, maximum pressure, and contact force in the superior aspect of the acetabulum. A concomitant decrease in these parameters was observed in the anterior and posterior walls. Anatomical reduction and fixation of the fracture with a plate and screws did not restore the pattern of loading to pre-injury levels.

Acetabulum↗
PubMed1995

The effect of prostaglandin E1 on liver adenine nucleotides and cytoplasmic enzymes in a porcine model of normothermic hepatic ischemia.

The liver has been judged relatively resistant to ischemia, but prolonged inflow occlusion at normothermic conditions can produce evidence of reversible or irreversible hepatocellular damage. Cytoprotective agents have been used both experimentally and clinically to afford extended viability of hepatocytes under reduced perfusion. One agent, prostaglandin E1, has been described clinically as effective in sustaining liver function under ischemic conditions. We have sought to verify this observation in an experimental model using prolonged normothermic inflow occlusion. Twenty miniature pigs were anesthetized and subjected to subtotal normothermic hepatic inflow occlusion (portal vein, hepatic artery, choledochal vessels) to allow for sufficient splanchnic decompression. Half of the animals received pretreatment with prostaglandin E1 (alprostadil) 500 micrograms intravenously. Inflow occlusion was maintained for 2 hours followed by reperfusion and killing 24 hours later. As a measure of functional preservation, the tissue adenine nucleotides adenosine monophosphate, diphosphate, and triphosphate (AMP, ADP, ATP) were measured in ischemic liver by freeze-clamping and high-performance liquid chromatography during occlusion and after reperfusion. Cytosolic enzyme determinations (aspartate transaminase, alanine transaminase, lactate dehydrogenase) were also made before occlusion and after reperfusion. As a possible indicator of cellular injury, blood ionized Ca++ was measured before inflow occlusion and after reperfusion. Although no difference was found in levels of AMP and ADP between prostaglandin E1 and control animals, ATP levels rose significantly higher during recovery in prostaglandin E1 animals at 60 minutes and 24 hours after reperfusion (13.97 +/- 1.29 and 13.60 +/- 0.91 mumoles/gm dry weight prostaglandin E1 vs. 9.25 +/- 0.97 and 9.80 +/- 0.85 mumoles/gm dry weight co control, P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗