Differential messenger ribonucleic acid expression in aggressive versus linear periprosthetic osteolysis.

Osteolysis is a radiographic term used to describe bone resorption adjacent to prosthetic implants. This process involves a spectrum of radiographic presentations, from small generalized linear patterns (linear osteolysis) to larger erosive patterns (aggressive osteolysis). The tissue from aggressive osteolytic lesions from five patients were compared with a series of linear osteolytic lesions from five additional patients. Total ribonucleic acid was extracted from these tissue samples, followed by reverse transcription and amplification by the polymerase chain reaction using a series of primers intended to amplify all ribonucleic acid species. The polymerase chain reaction products were separated by gel electrophoresis and compared by side by side analysis (differential display techniques). Transcription initiation factor IIB and cytokine receptor CRFB4 messenger ribonucleic acid were expressed in four of five patients with aggressive osteolytic lesions, as compared with none of five patients with linear osteolytic lesions. Conversely, nonmuscle myosin heavy chain messenger ribonucleic acid was expressed in five of five patients with linear osteolysis, and in none of the five patients with aggressive osteolysis. Thus, there is a difference in cell behavior between linear and aggressive osteolytic lesions that likely accounts for differences in radiographic appearance. This disparity is likely attributable to differences in local conditions (greater amounts of debris, increasing instability of the implant, or increased fluid pressures within the osteolytic lesions), and differences in host response.

Finite-element modelling of femoral shaft fracture fixation techniques post total hip arthroplasty.

The presence of a femoral prosthesis superior to a shaft fracture severely complicates fixation and treatment. This study uses two-dimensional, multithickness, plane stress finite-element models of a femur with prosthesis to investigate the stresses developed with the application of three popular fixation techniques: revision to a long stem prosthesis, lateral plating with a cortical bone allograft strut and cerclage wires, and custom plate application with proximal Parham band fixation with distal cortical screws (Ogden plate). The plate and bone contact as well as the fracture site contact were modelled by using orthotropic elements with custom-fit moduli so that only the normal stress to the interface was significant. A thermal analogy was used to model the cerclage and Parham band preloads so that representative preloads in the proximal fixation of the two types of plate treatments could be modelled. A parametric study was performed with the long-prosthesis model to show variations in stem lengths of one, two and three femoral diameters distal to the fracture site. The Ogden plate model showed a transfer of tensile stress near the proximal-most band, with the highest tensile stress being at the fracture site with evidence of stress shielding of the proximal lateral cortex. The cortical bone strut model showed a transfer of tensile stress to the bone strut but showed less shielding of the proximal cortex. The cerclage wires at the base of the bone strut showed the highest changes in load with the distalmost wire increasing to almost four times its original preload.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the Brooker-Wills and Russell-Taylor nails for treatment of patients who have fractures of the femoral shaft.

Seventy-three fractures of the femoral shaft (seventy patients) were randomized to treatment with interlocked nailing with either the Brooker-Wills femoral nail (thirty-nine fractures) or the Russell-Taylor femoral nail (thirty-four fractures). Sixty-one patients (sixty-four fractures) were prospectively followed from admission until healing of the fracture. Specific attention was paid to recording operative details, including technical difficulties associated with insertion of the nails. Technical difficulties were encountered in insertion of the proximal screw, distal screw, and nail, and in deployment of the fins. Insertion of the Russell-Taylor nail was associated with less technical difficulty, operative time, and estimated loss of blood. The two nails differ in their biomechanical properties, methods of fixation, and instrumentation. These differences did not affect the clinical outcome; the fractures in both groups of patients healed with excellent functional results.

Use of high-energy shock waves for bone cement removal.

The revision rate of total hip arthroplasty has increased dramatically over recent years, leading to different methods of extraction of the femoral cement mantle to reduce operative time and surgical risks. The use of high-energy shock waves produced by the Dornier HM.3 Lithotripter to interrupt the cement-bone interface and to reduce the material properties of the cement is investigated. Tests were conducted to measure the pull-out strength of cemented treated rods versus untreated rods, from the medullary canal of canine femurs. The treated femurs showed an average reduction in pull-out strength of 43%. An investigation involving the material properties of acrylic bone cement was also conducted. The properties tested were the compressive modulus of elasticity, the ultimate compressive strength, the ultimate tensile strength, and fracture toughness. The scanning electron microscope aided in determining whether microfractures in the cement resulted from the shock wave treatment. A theoretical study utilizing the finite element method was used to investigate areas of select shock wave treatment about the femoral prosthesis. Analysis of the results showed that the lithotripter treatment had no significant effect on the compressive properties but reduced the tensile properties and fracture toughness significantly. Scanning electron microscopy uncovered definite areas of induced microfractures not present in the control specimens. This study supports the concept of clinically noninvasive, preoperative shock wave treatment prior to total hip revision.

Open pelvic fracture with vaginal laceration and diaphragmatic rupture in a child.

A case report of a 4-year-old child who sustained an unstable open pelvic fracture with a diaphragmatic rupture is presented. A strong correlation exists between rupture of the diaphragm and pelvic fractures. We note the difference between pediatric and adult pelvic fractures, and discuss late complications unique to the child with a pelvic fracture. Pelvic external fixation is faster and less morbid than other surgical treatments for unstable pelvic fractures, and therefore provides an excellent alternative to pelvic open reduction in the acute treatment of pediatric patients with multi-system injuries. If fracture reduction is incomplete following initial closed manipulation, a staged secondary open reduction can then be performed.

Treatment of femoral shaft fractures with the Brooker-Wills interlocking intramedullary nail.

Fifty femur fractures were treated with the Brooker-Wills intramedullary locking nail. The indications included subtrochanteric, subisthmal, segmental or comminuted acute fractures or nonunions, and intramedullary shortening procedures. Eighteen technical problems in 13 (26%) patients were encountered during insertion of the nail. The incidence of technical problems was high early in the series and in procedures done with the patient in the supine position. Adverse clinical results from technical errors occurred in two patients. Most technical errors seem avoidable with careful technique. The mean healing time was only 12.1 weeks and there were four nonunions (8%). One patient had a 10 degrees malunion, four patients had 1-2 cm of shortening, and there were two late device fractures. No patients had rotational malalignment or deep infections. The results and complication rate are comparable to those reported for other interlocking systems. The Brooker-Wills nail is useful for treatment of complex femur fractures and has been effective in preventing malrotation, angulation, and excessive shortening.

Polymethylmethacrylate fixation of osteochondral fragments in dog knees.

The usefulness of polymethylmethacrylate (PMMA) to secure small osteochondral fragments was investigated in canine knees. Small osteochondral free fragments were osteotomized from the medial femoral condyle of 16 dog knees. The fragments were then bonded back in place with various amounts of PMMA. After 13 months, the animals were killed and each knee was examined for healing and arthritis. All of the fragments revascularized and healed. Poor reduction and PMMA extending to the articular surface universally led to arthritis. Small localized spot bonds of PMMA seemed to yield better results than large amounts of surface attachments.

Arthroscintigraphic evaluation of the painful total hip prosthesis.

Arthroscintigraphy was performed in 19 patients with a painful total hip prosthesis by injecting both Tc-99m sulfur colloid and iodinated radiographic contrast material intra-articularly. Scintigraphic and radiographic results correlated exactly in 15 patients, with one false-negative scintigram, one false-positive scintigram, and one false-negative arthrogram. One patient was evaluated by scintigraphy alone. Although arthroscintigraphy is potentially more sensitive than conventional arthrography in the detection of femoral component loosening, acetabular component loosening cannot be evaluated by scintigraphy alone. A combination of scintigraphy and conventional arthrography appears to be the most accurate imaging method in the evaluation of hip prosthesis loosening.

Total hip arthroplasty complicated by mismatched implant sizes. Report of two cases.

Numerous alternative types and sizes of implants for total hip arthroplasties are currently available. Two cases are reported in which the head size of the femoral component inserted was larger than the corresponding inner diameter of the acetabular cup. These are the first reported cases of this technical complication. The error can be avoided with careful preoperative planning and proper selection of implants. At 12- and 30-month follow-up evaluation, however, neither of these hips had dislocated or required revision. Immediate revision is not recommended, unless the hip dislocates or has symptomatic subluxations.

Dynamic musculotendinous transfer to replace the anterior cruciate ligament in the dog.

Dynamic muscle-tendon substitution for acute anterior cruciate deficiency in the dog was studied using the semimembranosus muscle-tendon. Nineteen mongrel dogs each had a semimembranosus transfer in one knee; as a control, the anterior cruciate ligament and the semimembranosus were released in the opposite knee. No postoperative immobilisation was used. The anterior drawer sign was assessed before and after operation and when the dogs were killed five months later. Dogs were excluded from the study if they developed infections or contractures of the hind legs. At five months, 11 dogs were available for study. The operated knees were examined histologically and evaluated using a reproducible index of arthritis based on: the macroscopic discoloration of the articular cartilage, the cellularity of the cartilage, the microscopic appearance of the articular surface, the loss of proteoglycans, the formation of osteophytes and the degree of subchondral osteosclerosis. There was no significant difference in the anterior drawer sign or the degree of arthritic changes between knees with a semimembranous transfer and the controls. Examination showed that a muscle-tendon transfer into the tibia was equivalent to transferring the muscle into the posterior capsule--the intra-articular tendon being weak but histologically viable. The transfer did not prevent the anterior drawer sign becoming positive nor the development of osteoarthritis. A second control group, in which three dogs had an arthrotomy and semimembranosus release in both their hind legs, showed that a semimembranosus release alone did not cause osteoarthritis.

Vertical deceleration injuries.

Six patients simultaneously sustained vertical deceleration injuries. Vertical deceleration injuries are serious and characteristically involve major weight bearing structures with forces transmitted through the foot, leg, pelvis and vertebral column. Injuries of the lower extremity are likely to be unilateral and comminuted because the force of deceleration is applied to a small area. The severity of the injury increases by increasing the rate of deceleration and decreasing the distance through which the body is decelerated. More severe injury occurs when deceleration forces are applied to the body in the vertical axis compared with the transverse, provided that mass, velocity and stopping distance remain the same.

Limb loss following Military Anti-Schock Trousers (MAST) application.

External counterpressure is a safe and effective method to treat shock and restore central circulation. Experience with the short-term use of MAST has been favorable. If external counterpressure is maintained for extended periods, however, altered peripheral hemodynamics may result in permanent damage. The development of compartment syndrome requiring amputation is reported in two patients with associated leg fractures. This unfortunate experience suggests that the sustained use of MAST in patients with shock and comminuted lower extremity fractures may jeopardize limb survival.

Vascular changes in leg trauma.

Fifteen patients with closed fractures of the distal tibia and fibula had marked elevation of initial compartment pressures. The pressures remained elevated for five days in the ten patients treated by cast and elevation. The pressures returned to normal within 24 hours in the five patients placed in a prototype water-jacketed boot which provides cooling and intermittent compression. Some patients exhibited arteriographic evidence of vascular injury.