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Biomedical subjects

E Ebramzadeh

Publications and source records attributed to E Ebramzadeh.

At least 19 recordsLinked to original sources
PubMed2001

Cement-cement interface strength: influence of time to apposition.

Cement-cement interfaces were created under simulated operating-room conditions. In order to analyze the effect of time to apposition on interface strength, two cement surfaces were brought together 1, 2, 4, and 6 min after 1 min of mixing and 45 s of waiting. Cement-cement interface strength was evaluated with the use of a three-point bending to failure test. Scanning electron microscopy (SEM) images of the failed interface were obtained. The mean interface strength decreased when the cement-cement interface was time delayed. Compared to bulk cement, interface strength in time-delayed groups decreased 8% after 1-min delay (p=.037), 18% after 2-min delay (p=.0004), 20% after 4-min delay (p=.0005), and 42% after 6-min delay (p<.0001). No statistically significant differences in interface strength were found between the 2- and 4-min delayed groups (p=.73). SEM images revealed that after 6-min delay, up to 50% of the cement surface can remain unbonded, explaining the decrease in strength of the cement-cement interface as a function of time to apposition. This laboratory study indicates that time to apposition plays a critical role in cement-cement interface strength. If any cementing technique involves the joining of two cement surfaces, it is recommended that the two cement surfaces be mated together within 5 min and 45 s after the start of mixing (1 min mixing; 45 s waiting; 4 min delay), in order to obtain a strong cement-cement interface bond. Delay beyond this can result in substantial reduction in the strength of the cement-cement interface bond.

Adhesiveness↗
PubMed2001

Open fractures of the forearm in children.

OBJECTIVE: To describe the epidemiology, early results of treatment, and complications associated with open fractures of the forearm in children. DESIGN: Retrospective review of patients treated according to protocol. SETTING: Level I trauma center. PATIENTS/PARTICIPANTS: All children with an open fracture of the forearm during a four-year period (n = 76). Fourteen patients were excluded because of inadequate follow-up or incomplete medical records. INTERVENTION: All fractures were treated with irrigation and debridement, and parenteral antibiotics. Twenty-five patients were managed with cast immobilization only, and the remaining thirty-seven, with internal fixation either with transcutaneous pins, intramedullary pins, or plates and screws, followed by immobilization in a cast. MAIN OUTCOME MEASUREMENTS: Time to union, angular alignment at union, and incidence of complications. RESULTS: The average time to union was 8.9 weeks (median, eight weeks; range, 6 to 17 weeks). There were no nonunions, but three of the sixty-two fractures had delayed union. Eight of the sixty-two fractures healed with an angular deformity of more than 10 degrees, and two developed infections, one deep and one superficial. There were three preoperative and four postoperative nerve palsies, which all resolved spontaneously. CONCLUSIONS: Open fractures of the forearm in children, treated with prompt administration of parenteral antibiotics followed by debridement, were associated with a fairly low incidence of complications. Although we found that the use of some form of internal fixation tended to reduce both the need to remanipulate these fractures (p = 0.08), and to minimize the incidence of angular deformity greater than 10 degrees (p = 0.16), these findings did not reach statistical significance.

Adolescent↗
PubMed2001

Outcome study of hallux valgus surgery--an AOFAS multi-center study.

Three hundred and eleven patients have been enrolled in a multi-center prospective study evaluating the outcome of hallux valgus surgery by the members of the American Orthopaedic Foot and Ankle Society. One hundred seventy-nine of these patients have completed six-month follow-up questionnaires, and 195 have completed 12-month questionnaires. The AAOS Lower Limb Outcomes Data Collection Questionnaire and the Foot and Ankle Outcomes Data Collection Questionnaire were used to assess patients' perceptions of their results. Both of these instruments are validated lower extremity instruments. They contain the SF-36 instrument as well as questions relating to lower extremity function. At six- and 12-month follow-up, significant improvement has been noted in the patients' SF-36 physical function scores, role physical scores, and bodily pain scores. Role emotional scores were increased at six months but returned to baseline at 12 months. The scores for physical health and pain and satisfaction with symptoms for the lower extremity have significantly improved. The global foot and ankle score and shoe comfort score from the foot and ankle module have also significantly improved. This outcome study is the first to focus on the patient's perception of results of hallux valgus surgery and demonstrates a significant improvement in pain, function, and satisfaction after bunion surgery performed by members of the American Orthopaedic Foot and Ankle Society.

Adolescent↗
PubMed2001

Characteristics of degeneration in an unstable knee with a coronal surface step-off.

To investigate the effect of instability on the remodelling of a minor articular surface offset, we created a 0.5 mm coronal step-off of the medial femoral condyle in 12 New Zealand white rabbits and transected the anterior cruciate ligament (ACL). A control group of 12 rabbits had only ACL resection and the opposite knee was used as the non-operated control. The osteoarthritic changes at 6, 12 and 24 weeks after surgery were evaluated histologically. In addition, changes in the immunological detection of 3-B-3(-) and 7-D-4 chondroitin-6-sulphate epitopes were determined because of the previous association of such changes with repair of cartilage and early osteoarthritis. In the instability/step-off group there was rapidly progressing focal degeneration of cartilage on the high side of the defect, not seen in previous step-off studies in stable knees. The rest of the femoral condyles and the tibial plateaux of the instability/step-off group had moderate osteoarthritis similar to that of the instability group. 3-B-3(-) was detectable in the early and the intermediate stages of osteoarthritis but no staining was seen in the severely damaged cartilage zones. Immunoreactivity with 7-D-4 increased as degeneration progressed.

Animals↗
PubMed1999

Lessons learned from loosening of the McKee-Farrar metal-on-metal total hip replacement.

Clinical and radiographic data for 15 McKee-Farrar hip replacements that had failed because of aseptic loosening (4 stem loosening, 9 cup loosening, and 2 loosening of both components) between 0.6 and 21 years (average, 8.3 years) were compared with 15 hips in which the McKee-Farrar total hip replacement has survived between 21 and 26 years. Hips that loosened were biomechanically disadvantaged compared with those that demonstrated long-term survival. Radiographic evaluation demonstrated that in hips that were revised for aseptic femoral loosening, the offset was decreased by a mean of 1.4, whereas it was increased by a mean of 4.9 mm in the surviving hips (P = .04). Further, in hips revised for aseptic loosening, the center of rotation was medialized by a mean of only 1.4 mm, whereas the center of rotation was medialized by a mean of 6.4 mm in the surviving hips (P = .1). Unfavorable biomechanics results in increased joint reaction forces that could contribute to loosening of these prostheses. Five of 6 McKee-Farrar stems revised for aseptic loosening compared with 7 of 15 surviving stems were in varus (P = .1) and, as a result, had cement mantle defects in zones III and VII. Thus, in the McKee-Farrar, similar to what has been seen in hips with metal-on-plastic bearings, curved stems are associated with varus positioning, cement mantle defects, and loosening. Wear of the metal-on-metal articulation does not appear to be the cause of failure in these cases. Wear could not be detected radiographically. At revision surgery, there was no indication of excessive bearing wear or gross metal staining of periprosthetic tissues. Microscopic analysis of tissue sections demonstrated both metal and polymethylmethacrylate particles of variable size and shape. The variability of the particles suggests that they are likely the result of loosening and that they were not generated by bearing surface wear that could cause loosening. Although it is hoped that improvements in the wear resistance of the bearing will increase survivorship, this experience and analysis of the McKee-Farrar total hip replacement illustrates the importance of the implant design, biomechanics of the reconstruction, and role of surgical implantation technique.

Arthroplasty, Replacement, Knee↗
PubMed1999

Mechanism of failure in hips with an uncemented, all polyethylene socket.

The outcome of 32 patients with 33 primary total hip replacements performed using noncemented uncoated polyethylene acetabular cups (RM cup) with cemented titanium alloy monoblock stems (STH-2 stem) was reviewed. At a mean followup of 6.3 years (range, 6 months-10 years), the failure rate was 57%, more than 14 times higher than the rate typically seen with cemented polyethylene acetabular cups used with the STH stem. Failure was characterized by rapidly progressive acetabular or femoral osteolytic lesions that resulted in extensive bone loss, often in patients who had no symptoms. In addition to the debris that typically is generated by a metal on plastic bearing couple, an abundance of polyethylene particles of submicron size were produced at the cup-bone interface. Tissues retrieved from areas of osteolysis revealed the presence of intracellular submicron polyethylene particles in macrophages. It is recommended that patients with no symptoms who have RM noncemented, uncoated acetabular cups be followed up yearly and undergo early revision surgery when faced with osteolysis to prevent extensive bone loss.

Acetabulum↗
PubMed1998

Use of the Taguchi method for biomechanical comparison of flexor-tendon-repair techniques to allow immediate active flexion. A new method of analysis and optimization of technique to improve the quality of the repair.

The current trend toward early active flexion after repair of the flexor tendons necessitates a stronger repair than that provided by a modified Kessler technique with use of 4-0 nylon suture. The purpose of the current study was to determine, with use of the Taguchi method of analysis, the strongest and most consistent repair of the flexor tendons. Flexor tendons were obtained from fresh-frozen hands of human cadavera. Eight flexor tendons initially were repaired with the modified Kessler technique with use of 4-0 nylon core suture and 6-0 nylon epitenon suture. A test matrix was used to analyze a total of twenty variables in sixty-four tests. These variables included eight techniques for core-suture repair, four types of core suture, two sizes of core suture, four techniques for suture of the epitenon, and two distances from the repair site for placement of the core suture. After each repair, the specimens were mounted in a servohydraulic mechanical testing machine for tension-testing to failure. The optimum combination of variables was determined, with the Taguchi method, to be an augmented Becker technique with use of 3-0 Mersilene core suture, placed 0.75 centimeter from the cut edge with volar epitenon suture. The four-strand, double modified Kessler technique provided the second strongest repair. Five tendons that had been repaired with use of the optimum combination then were tested and compared with tendons that had been repaired with the standard modified Kessler technique. With the optimum combination of variables, the strength of the repair improved from a mean (and standard deviation) of 17.2 +/- 2.9 to 128 +/- 5.6 newtons, and the stiffness improved from a mean of 4.6 to 16.2 newtons per millimeter.

Biomechanical Phenomena↗
PubMed1998

Complications in the use of the Bailey-Dubow extensible nail.

The results of 40 extensible intramedullary nailing procedures in 15 children who had osteogenesis imperfecta were reviewed to identify risk factors leading to complications of this method of treatment. There were 40 complications, 17 major and 23 minor. The 17 major complications led to 15 additional procedures, 10 of which were to remove or replace the implant. The prevalence of major complications was highest in patients who were younger than 5 years when the nail was inserted. Nails placed in the tibia tended to produce a higher incidence of major complications than did those placed in the femur, but this difference was not statistically significant. By survivorship analysis, patients had a greater risk of requiring a revision procedure when a technical error occurred at the time the nail was inserted. Patients who had nails placed in the femur tended to have a lower risk of needing revision surgery than did those who had nails placed in the tibia, but this difference was not statistically significant. The results suggested that the extensible nail is most advantageous in the femur and in patients older than 5 years. Avoiding technical errors when inserting the nail may improve the longevity of the device.

Age Factors↗
PubMed1997

Effect of partial versus complete plantar fasciotomy on the windlass mechanism.

Eight adult below-knee cadaver specimens were placed in a testing machine and loaded to 350 newtons according to a strict protocol. Arch height and length measurements were obtained in each specimen with the toes resting on the foot plate, dorsiflexed to 30 degrees, and maximally dorsiflexed manually. The plantar fascia was then divided from medial to lateral in one-quarter increments, and the effect on arch height and length measurements was assessed using the same loading protocol. A consistent decrease in the arch-supporting function on sequential sectioning of the plantar fascia was encountered. A less consistent decrease in the arch-supporting function was reflected by the increase in the height of the arch with sequential sectioning of the plantar fascia. The study demonstrates that partial plantar fasciotomy decreases the arch-supporting function of the plantar fascia in addition to weakening the structure. Strict surgical indications for this type of procedure should be maintained.

Adult↗
PubMed1997

The effect of fibular malreduction on contact pressures in an ankle fracture malunion model.

Nine fresh-frozen cadaveric specimens were disarticulated through the knee, and the soft tissues, except for the interosseous ligaments and interosseous membrane, were removed to the level of the ankle. The subtalar joint was secured with screws in neutral position (approximately 5 degrees of valgus). Contact pressures in the tibiotalar joint were measured with use of low-grade pressure-sensitive film, which was placed through an anterior capsulotomy. For each measurement, 700 newtons of load was applied to the specimen for one minute. The film imprints were scanned, and the contact pressures were quantitated in nine equal quadrants over the talar dome. A fracture-displacement device was secured to the distal end of the fibula; the device allowed for individual or combined displacements consisting of shortening, lateral shift, and external rotation of the fibula. The ankle was maintained in neutral flexion. The ligamentous injury associated with a pronation-lateral rotation fracture of the ankle was simulated by dividing the deep fibers of the deltoid ligament, the anterior-inferior tibiofibular ligament, and the interosseous membrane to a point that was an average of fifty-three millimeters proximal to the ankle joint. Baseline contact area and contact pressure in the joint were determined, followed by measurements after two, four, and six millimeters of shortening of the fibula; after two, four, and six millimeters of lateral shift of the fibula; and after 5, 10, and 15 degrees of external rotation of the fibula. The three types of displacement were tested individually as well as in combination. The simulated deformities were found to cause a shift of the contact pressure to the mid-lateral and posterolateral quadrants of the talar dome, with pressures as high as 4.1 megapascals. A corresponding decrease in the contact pressures was noted in the medial quadrants of the talar dome. The highest pressures were recorded for maximum shortening of the fibula, the combination of maximum shortening and lateral shift, the combination of maximum shortening and external rotation, and the combination of maximum shortening, lateral shift, and external rotation. In general, increases in each displacement variable corresponded to increasing contact pressures.

Aged↗
PubMed1997

The Allen test. A study of inter-observer reliability.

The Allen test was performed by four physician examiners on 200 hands of healthy volunteers. Positive results were found in 5.5% of hands. There was not a single case in which all four observers agreed. Considerable inter-observer disagreement is associated with the Allen test.

Adult↗
PubMed1997

Swanson metacarpophalangeal joint arthroplasty in patients with rheumatoid arthritis.

Between 1981 and 1991, 348 Swanson metacarpophalangeal replacements were implanted in patients with rheumatoid arthritis. There were 64 female and seven male patients. Both hands were reconstructed in 18 patients. Clinically, 170 implants were available for an average of 5.2 years (range, 2-10 years) followup. Severe synovitis was seen in 7% of metacarpophalangeal joints, moderate synovitis in 25%, slight synovitis in 17%, and synovitis was not present in 51%. Pain was found to be severe in 4% of the joints, moderate in 3%, slight in 39%, and not present in 54% of the joints. The average preoperative active arc of motion was 38 degrees, and the average postoperative arc of motion was 27 degrees. Eleven of 12 fractures found were revised. There were no infections. Functionally, of 58 patients assessed, 58 (100%) reported the ability to feed themselves, 55 (94%) to button clothes, and 54 (93%) to write. Quality radiographs were available in 144 joints. Eighty-four percent of implants showed sclerosis of bone and 8% showed resorption adjacent to the implant. Survivorship analysis revealed a 94% success rate at 5 years, 93% at 7 years, and 90% at 10 years using the end point of revision surgery.

Arthritis, Rheumatoid↗
PubMed1997

Swanson proximal interphalangeal joint arthroplasty in patients with rheumatoid arthritis.

One hundred thirty-eight Swanson proximal interphalangeal replacements were implanted in patients with rheumatoid arthritis, of which 99 implants were available for average 5.8 years followup. Pain was severe in 1%, moderate in 4%, slight in 28%, and not present in 67%. The average preoperative active arc of motion was 38 degrees, and postoperative 29 degrees. Ten fractures were found, and were revised. Of 45 patients assessed, 45 (100%) reported the ability to feed themselves, 43 (96%) to button their clothes, and 42 (93%) to write. There was sclerosis of bone around 78% of the implants and resorption adjacent to 12% of the implants. Survivorship analysis showed that 81% of implants were not revised at 9 years.

Activities of Daily Living↗
PubMed1996

Stable partial debonding of the cement interfaces indicated by a finite element model of a total hip prosthesis.

A simplified three-dimensional finite element model of the femoral component of a cemented total hip prosthesis was used to investigate whether partial debonding at the stem-cement or bone-cement interfaces propagates in a stable or unstable manner, and to assess the resultant variation of the stresses within the cement layer. The likelihood of unstable debonding under tensile failure mode was assessed both by a conventional monotonic strength criterion and by a fracture mechanics approach that took into account debonding due to fatigue loading. The model predicted that partial debonding at the cement interfaces would be stable and would not precipitate complete debonding. Among the various bonding conditions that were investigated, the maximum tensile stress within the cement layer was least with a small amount of debonding rather than with complete bonding. These results were consistent with clinical observations of nonprogressive or slowly progressive separation at cement interfaces in cemented femoral components that were otherwise well functioning and asymptomatic.

Biomechanical Phenomena↗
PubMed1995

Factors influencing the outcome of closed tibial fractures treated with functional bracing.

One thousand consecutive closed diaphyseal tibial fractures, treated with prefabricated functional below-knee braces, were analyzed by statistical methods to determine factors predictive of final fracture outcome. Neither the age of the patient nor the location of the fracture influenced the speed of healing. In 95% of the fractures, the final shortening was < or = 12 mm. The mean final shortening was 4.28 mm, compared with mean initial shortening of 4.25 mm. This confirmed the authors' long-held hypothesis, that, in general, for closed, diaphyseal tibial fractures treated with functional bracing and graduated weightbearing ambulation, the final shortening does not increase beyond the initial one. Final angulatory deformity in any plane was < or = 6 degrees in 90% of patients. The presence of an intact fibula was a relative contraindication for functional fracture bracing because angulatory deformity was more likely to develop. The incidence of nonunion was 1.1%. The high union rate and low morbidity associated with functional bracing of closed tibial fractures suggest that the routine use of more expensive surgical treatments is difficult to justify. A clear understanding of the rationale of functional bracing, its indications and contradictions, and its clinical application protocol are essential for the attainment of satisfactory results.

Adolescent↗
PubMed1994

A review of ankle arthrodesis: predisposing factors to nonunion.

The purpose of this study was to review 15 years of experience with ankle fusions, specifically addressing the underlying etiology of ankle pathology, incidence of nonunion, and associated predisposing conditions that can lead to nonunion. Seventy-eight ankle fusions, performed between 1975 and 1990, were reviewed for this study. The average follow-up was 4 years. Patients with nonunion were evaluated separately to look at the predisposing factors that may have lead to nonunion. Factors associated with nonunion included fracture type, evidence of avascular necrosis, infection, major medical problems, and open injuries. Factors that were not associated with nonunion included age, past history of subtalar or triple arthrodesis, and technique.

Adolescent↗
PubMed1994

The cement mantle in total hip arthroplasty. Analysis of long-term radiographic results.

The correlation between the thickness of the cement mantle, the medullary canal fill, and the orientation of the stem and the long-term radiographic outcome of 836 cemented femoral components in patients who had a primary total hip replacement was assessed with use of survival analysis over a twenty-one-year follow-up period. The femoral stems of hips that had a two to five-millimeter-thick cement mantle in the proximal medial region had a better outcome than stems implanted with a thicker or thinner cement mantle. Stems in femora with less than two millimeters of proximal medial cancellous bone had a better outcome than stems in femora with thicker cancellous bone. Stems that filled more than half of the medullary canal had better radiographic results than those that filled half or less. Progressive loosening, fracture of the cement, and radiolucent lines at the stem-cement or bone-cement interfaces were more likely to develop in stems that were oriented in more than 5 degrees of varus than in those in neutral or valgus. The noted correlations were true whether the stem was made of titanium alloy or of stainless steel. The results of this study emphasize the importance of careful preoperative planning in total hip arthroplasty done with cement and provide guidelines for the selection of the shape, size, and position of the stem.

Bone Cements↗