Biomedical subjects

J M Kabo

Publications and source records attributed to J M Kabo.

At least 19 recordsLinked to original sources

PubMed1992

Intra-articular corticosteroid reduces joint stiffness after an experimental periarticular fracture.

Early care after surgery or trauma to the extremities often includes a period of immobilization. The resultant joint stiffness may require extensive rehabilitation and may permanently limit function of the limb. Posttraumatic joint stiffness is particularly vexing in the small joints. In an experimental model, we tested the effects of intra-articular corticosteroid injections on stiffness in a joint at risk of posttraumatic joint stiffness. Triamcinolone was injected into ankle joints of rabbits after distal tibial fractures. Three weeks after injury, joint stiffness increased 34% in ankles injected with the steroid. Stiffness in ankles injected with saline solution and in ankles treated with no injection increased 133% and 224%, respectively. Limb swelling and tibial torsional strength to failure were not significantly affected by either of the treatments.

Animals↗

PubMed1992

Biomechanical effects of a new point configuration and a modified cross-sectional configuration in Kirschner-wire fixation.

Kirschner-type wires (K-wires) comprising three different point configurations and two cross-sectional shaft configurations were drilled into bone to determine the insertional force required and the holding power achieved with each type. Round K-wires with either a diamond point or a high rake-angle trocar point were compared with each other and with C-wires, which have a rounded square cross section and a short diamond point. The K-wires performed superiorly to C-wires with respect to bone penetration. The K-wires demonstrated about twice as much holding power as the C-wires. No significant differences in performance were detected between the diamond-tipped and trocar-tipped K-wires with respect to either insertion or pull-out. For all three wire-tip combinations, insertion was facilitated by faster drill speed, but holding strength was superior with slower speed. For ease of insertion, even at oblique angles, and for maximum holding strength, the high-rake angle, trocar-tipped K wire is best.

Animals↗

PubMed1992

Biomechanical comparisons of unidirectional and bidirectional Kirschner-wire insertion.

Peak axial loads on entry and peak pull-out loads were measured for Kirschner-wires (K-wire) inserted into canine metacarpals. The wires were placed using a standard, unidirectional drill and using an oscillating, bidirectional drill that reversed spin direction every 120 degrees. Seven trocar-tip wires were compared with seven diamond-tip wires using each drilling method. The trocar-tip wires demonstrated equal peak axial loads on entry when drilled at comparable speeds unidirectionally and bidirectionally. Pull-out load of the trocar tip after bidirectional insertion was less than that for unidirectional insertion but was still in the clinically useful range. The diamond-tip wire exhibited higher peak axial load on entry and lower peak pull-out load when drilled bidirectionally. Bidirectional insertion of a trocar-tip K-wire offers fixation characteristics comparable with those with unidirectional insertion and will potentially reduce the risk of soft-tissue damage associated with winding-up and avulsion of vital structures on the spinning shaft of a unidirectional driver.

Animals↗

PubMed1992

Continued growth of the proximal part of the tibia after prosthetic reconstruction of the skeletally immature knee. Estimation of the minimum growth force in vivo in humans.

We studied five skeletally immature patients who had a cemented endoprosthetic replacement involving the proximal part of the tibia because of a malignant tumor. In each patient, the cement-column fractured, allowing additional physeal growth. With plain radiographs and scanograms, we determined the cross-sectional areas of the physes, the cement-mantle, and the tibial component. Using the known tensile strength of polymethylmethacrylate cement, we then calculated the minimum force that the growth plates must have overcome to fracture the cement. This averaged 584 newtons per square centimeter. This observation of continued tibial growth after partial physeal ablation with a cemented prosthesis in skeletally immature patients presented a unique opportunity to estimate the force generated in the human physis during growth.

Biomechanical Phenomena↗

PubMed1992

Acetabular reconstruction with a threaded prosthesis for failed total hip arthroplasty.

The MEC-Ring threaded acetabular component was used in 35 patients for revision of failed cemented hip arthroplasties, and 32 have been observed for two to four years (mean, 2.5 years). With only a short-term follow-up period, 44% of patients have already required revision for failure of the MEC-Ring acetabular component. Patients with especially poor acetabular bone stock that had had structural bone graft had a significantly higher rate of failure. The authors developed a technique of supine oblique roentgenograms that allowed better visualization of the component-bone interface. Eighty-six percent of patients had radiolucencies, and 67% of these were progressive. The presence of progressive radiolucencies, component migration, or both was associated with a higher failure rate. Progressive radiolucencies were also associated with a worse pain score in patients whose arthroplasties have not failed. The MEC-Ring threaded component is not recommended for revision hip arthroplasty, especially in cases with poor acetabular bone stock.

Acetabulum↗

PubMed1992

The mechanism of loosening of cemented acetabular components in total hip arthroplasty. Analysis of specimens retrieved at autopsy.

Late aseptic loosening of cemented acetabular components is governed by the progressive, three-dimensional resorption of the bone immediately adjacent to the cement mantle. This process begins circumferentially at the intraarticular margin and progresses toward the dome of the implant. Evidence of bone resorption at the cement-bone interface was present even in the most well-fixed implants before the appearance of lucent lines on standard roentgenographic views. The mechanical stability of the implant was determined by the three-dimensional extent of bone resorption and membrane formation at the cement-bone interface. The leading edge of the membrane is a transition zone from regions of membrane interposition between the cement and the bone to regions of intimate cement-bone contact. Histologic analysis revealed that progressive bone resorption is fueled by small particles of high density polyethylene (HDP) migrating along the cement-bone interface and bone resorption occurs as a result of the macrophage inflammatory response to the particulate HDP. Evidence in support of a mechanical basis for failure of fixation was lacking. The mechanism of late aseptic loosening of a cemented acetabular component is therefore biologic in nature, not mechanical. This is exactly opposite to the mechanism of loosening on the femoral side of a cemented total hip replacement, which is mechanical in nature.

Acetabulum↗

PubMed1991

Endoprosthetic replacement for stage IIB osteosarcoma.

Over an eight-year period, 100 patients with IIB osteosarcoma have been managed. Eighty-one were treated with limb-salvage procedures, 78 of which involved reconstruction utilizing endoprostheses. Only 19 patients received amputation as the primary treatment for local control. Since 1984, all patients received preoperative and post-operative adjuvant chemotherapy. Those patients who received chemotherapy had a statistically significant improvement in five-year survival over those who did not (57% and 32%, respectively, p = 0.014). The functional results were good overall, with excellent results seen in distal femoral reconstruction. Twenty-eight of the 78 patients treated with endoprosthetic reconstruction experienced 30 complications (36%). Mechanical failure was the most common complication (10%) but was generally correctable. The local recurrence rate was 5% and the infection rate was 3%. Local complications were manageable. A statistical analysis revealed that the relative risk of patient death was 2.5 times higher than prosthesis failure for the 78 patients with endoprosthetic reconstruction. The intermediate-term results, with a median follow-up period of 43 months, remains encouraging.

Adolescent↗

PubMed1991

Continuous passive motion versus immobilization. The effect on posttraumatic joint stiffness.

Management of intraarticular fractures is often complicated by joint stiffness long after bony healing has occurred. The following experiments provide biomechanical evidence for the effectiveness of CPM in maintaining joint function in stabilized articular injuries. The ankles of ten adolescent New Zealand white rabbits were penetrated by Steinmann pins to create an intraarticular injury. One limb of each animal was immobilized, and the contralateral limb was placed in a continuous passive motion (CPM) machine for three weeks. Joint stiffness of each ankle was quantified with an arthrograph before injury and after three weeks of treatment. Hindlimb volumes were recorded before injury and monitored at weekly intervals using a water-displacement method. Joint stiffness increased 2.6 times the preinjury levels in limbs that were immobilized for three weeks. There was no statistically significant increase in joint stiffness in ankles treated with CPM compared to preinjury values. The posttraumatic difference between the CPM-treated and immobilized limbs was highly significant; limb swelling was not affected by CPM.

Animals↗

PubMed1990

Direct measurement of resultant forces in the anterior cruciate ligament. An in vitro study performed with a new experimental technique.

A new technique was used to measure the resultant forces in the anterior cruciate ligament during a series of loading experiments on seventeen fresh-frozen cadaver specimens. The base of the ligament's tibial attachment was mechanically isolated with a coring cutter, and a specially designed load-transducer was fixed to the bone-plug that contained the ligament's tibial insertion so that the resultant forces were directly measured by the load-cell. Although the magnitudes of values for forces varied considerably between specimens for a given test condition, the patterns of loading with respect to direction of loading and the angle of flexion of the knee were remarkably consistent. Passive extension of the knee generated forces in the ligament only during the last 10 degrees of extension; at 5 degrees of hyperextension, the forces ranged from fifty to 240 newtons (mean, 118 newtons). When a 200-newton pull of the quadriceps tendon was applied to extend a knee slowly against tibial resistance, however, the force in the ligament increased at all angles of flexion of the knee. Internal tibial torque always generated greater forces in the ligament than did external tibial torque; higher forces were recorded as the knee was extended. The greatest forces (133 to 370 newtons) were generated when ten newton-meters of internal tibial torque was applied to a hyperextended knee. Fifteen newton-meters of applied varus moment generated forces of ninety-four to 177 newtons at full extension; fifteen newton-meters of applied valgus moment generated a mean force of fifty-six newtons, which remained unchanged with flexion of the knee. The force during straight anterior translation of the tibia was approximately equal to the anterior force applied to the tibia. The application of 925 newtons of tibiofemoral contact force reduced the mean force in the ligament that was generated by 200 newtons of anterior pull on the tibia by 36 per cent at full extension and 46 per cent at 20 degrees of flexion.

Aged↗

PubMed1990

Strength of initial mechanical fixation of screw ring acetabular components.

This study was conducted to determine the effects of design on the initial fixation of several types of screw-ring acetabular components. The components were tested in polyurethane foam to assess relative screw fixation strengths with a consistent material. Embalmed pelves from anatomic specimens were used to conduct paired tests between designs that showed large differences in insertional torque to failure in foam. The quality of the initial fixation in foam was found to be dependent on the design features of the components. Components with widely spaced, deep threads, and minimal thread interruptions offered the strongest initial fixation in foam. Tests in bone revealed a wide range of fixation strengths reflecting the variability in bone quality. No differences in fixation strength attributable to component design were observed in bone. When the insertional failure torque was greater than 60 N.m, one-half of the pelves fractured, and these fractures occurred with all designs. At failure torques less than 60 N.m, failure was predominantly due to thread strippage of the screw, with only two of 20 specimens experiencing pelvic fracture.

Acetabulum↗

PubMed1989

Preliminary results of an off-the-shelf press-fit stem. The anthropometric total hip femoral component using exact-fit principles.

The use of custom-manufactured femoral prostheses as part of routine total hip arthroplasty (THA) has been suggested. However, there are several disadvantages, including possible inaccuracy of fit, inadequate instrumentation, and high cost. A series of 28 THAs (including 18% for revision of failed, cemented THA) using a press-fit prosthesis of contemporary design were investigated. The average follow-up period was 28 months (range, 12-49 months). Clinical results were overall very good, even in revision cases. Roentgenographic changes included rapid femoral remodeling, which may increase component stability. Given the clinical and roentgenographic results obtained in this complex-problem patient population, it is difficult to justify the use of custom femoral components in routine THA.

Adult↗

PubMed1989

The anthropometric total hip femoral prosthesis. Preliminary clinical and roentgenographic findings of exact-fit cementless application.

Total hip arthroplasty in the young patient remains a considerable challenge. Cemented arthroplasty has an unacceptably high failure rate. Porous ingrowth designs are one alternative, but bone ingrowth is unpredictable, thigh pain is a frequent clinical finding, stress shielding is often observed, revision is more complicated, and microporous components are mechanically weaker. A new anthropometric femoral component has been designed with a goal of long-term stability through osseointegration. The prosthesis is optimized for canal fill in the distal metaphysis and proximal diaphysis. The components are manufactured in 16 sizes, with cutting broaches precisely machined to the same dimensions to provide an exact fit to the femur. The high-strength TiAl6V4 alloy stem is combined with heads of either CoCr alloy or alumina (Al2O3) for reduced polyethylene wear. The 135 degrees neck-shaft angle and modular design allow for restoration of the abductor lever arm. Because the prosthesis is not porous coated, it is also suitable for use with cement. In cemented application, the prosthesis shape provides an optimal cement mantle. Seventy-one total hip arthroplasties have been performed using the Anthropometric Total Hip (ATH) prosthesis: 31 with exact-fit cementless fixation and 40 with cement. Of those using cementless fixation, 21 have been followed for more than one year (mean, 20 months; range, 12-48 months). The early clinical findings are as good as, or superior to, other cementless designs used at the authors' institution. Stress remodeling of the proximal femur occurs early and stabilizes by one year. The observed changes appear to improve the stability of the prosthesis. Clinical and roentgenographic findings suggest the osseointegration of the ATH femoral component.

Adult↗

PubMed1989

The effects of dexamethasone on periarticular swelling and joint stiffness following fracture in a rabbit hindlimb model.

An established rabbit hindlimb model was used to determine the effects of systemic steroid administration on posttraumatic limb swelling and joint stiffness. Dexamethasone acetate was administered intramuscularly to the test rabbits in one of four doses two hours following fracture as well as one and two weeks later. Dexamethasone did not produce a significant decrease in swelling but did produce a statistically significant dose-dependent decrease in ankle stiffness compared to controls. Tibia torsional strength to failure was not adversely affected.

Animals↗

PubMed1989

The effects of two nonsteroidal antiinflammatory drugs on limb swelling, joint stiffness, and bone torsional strength following fracture in a rabbit model.

Using a rabbit distal tibia fracture model treated by immobilization for three weeks, the effects of two nonsteroidal antiinflammatory drugs on postfracture limb swelling, joint stiffness, and torsional bone strength were examined. Limb swelling in rabbits treated with low-dose piroxicam was reduced by 39%, and high-dose piroxicam reduced limb swelling by 86%. Flunixin, tested at one dose, reduced swelling by 53%. Neither piroxicam nor flunixin affected ankle stiffness or tibia torsional strength.

Animals↗

PubMed1988

Efficacy of soft splints in reducing severe knee-flexion contractures.

This study evaluated the effectiveness of soft splints made from polyurethane foam in reducing severe knee-flexion contractures of patients with cerebral palsy. The splints were applied nightly over a period of 10 months. Knee-flexion contractures were reduced by an average of 24 degrees in all patients. Younger patients generally presented with less severe initial contractures and had the greatest percentage of improvement. When used on a single limb when bilateral contractures were present, sympathetic reduction of the contracture occurred to varying degrees in the unsplinted limb. It is recommended that the splints be replaced regularly to maximize their effectiveness. The benefit-to-cost ratio is extremely high and their low cost makes soft splints feasible for use in developing countries and by low-income families.

Adolescent↗

PubMed1988

The effects of dimethyl sulfoxide on posttraumatic limb swelling and joint stiffness. A review and an experimental study in rabbits.

Dimethyl sulfoxide (DMSO) is an inorganic compound with many interesting in vitro properties, including the ability to scavenge oxygen-free radicals. DMSO has been used to treat a variety of clinical conditions, especially musculoskeletal trauma, but valid data regarding its effectiveness are lacking. This paper reviews the pharmacology of DMSO and reports on its effectiveness in reducing posttraumatic limb swelling and ankle joint stiffness in a rabbit hind limb model. The left and right hind limbs of the test and control animals were instrumented and fractured identically. DMSO was applied daily to the skin of only one limb in the test animals. DMSO reduced postinjury ankle stiffness in both ankles of the test rabbits by 41% but had no effect on limb swelling compared to control rabbits. Postulated mechanisms of decreased joint stiffness include oxygen-free radical scavenging and inhibition of fibroblast proliferation.

Animals↗

PubMed1988

Comparison of in vivo cementless acetabular fixation.

Cementless fixation in total hip arthroplasty is increasingly popular because of the failure rates of cemented components, particularly in younger patients. The reported European studies with cementless acetabular implants and the relatively short-term American studies suggest that loosening is not a problem with any of the designs in clinical use. This point of view is reminiscent of that regarding cemented acetabular components prior to the realization that cemented acetabular failure was a delayed long-term phenomenon. Cementless acetabular components are principally of two types, threaded and porous coated. Prior to this study, there was little clinical or experimental evidence to indicate which design gains superior fixation and which is most likely to maintain long-term fixation and durability. Fixation of threaded and porous-coated components was evaluated mechanically and histologically in dogs after weight-bearing periods of two and six months. The threaded specimens were significantly looser than the porous-coated specimens at both two and six months. There was a trend toward loosening of both types of components with time. Fibrous tissue alone appeared to invest all of the threaded components, whereas bone and fibrous-tissue ingrowth appeared to incorporate the porous components. The mineral apposition rate for the components was not significantly different between the two components or between different regions in the specimens.

Acetabulum↗

PubMed1988

The Dana total shoulder arthroplasty.

Fifty-six Dana unconstrained total shoulder arthroplasties in forty-seven patients were followed for a minimum of two years. The preoperative diagnoses included osteoarthritis, rheumatoid arthritis, traumatic arthritis, avascular necrosis, failed hemiarthroplasty, and failed total shoulder arthroplasty of another design. For all of the patients, the average rating for pain improved from 3 points preoperatively to 8 points postoperatively, and the average rating for function improved from 3 to 7 points. The ranges of abduction and of external rotation improved substantially in the shoulders that were affected by osteoarthritis, rheumatoid arthritis, or osteonecrosis. Ten patients were treated with a hooded glenoid component, designed to improve stability in shoulders in which the rotator cuff is deficient. In these shoulders, both the rating for pain and the rating for function improved, although the range of motion did not. Complications that required revision of the arthroplasty developed in five shoulders in which a regular component had been implanted and in two that had a hooded glenoid component. A radiolucent line developed at the bone-cement interface of the glenoid component in fifty-three shoulders, but only two revisions were done for loosening of the glenoid component.

Adult↗