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Biomedical subjects

J N Powell

Publications and source records attributed to J N Powell.

At least 19 recordsLinked to original sources
PubMed2005

The effect of a venous filter on the embolic load during medullary canal pressurization: a canine study.

BACKGROUND: Acute intramedullary stabilization of femoral shaft fractures in multiply injured patients is controversial. Intravasation of medullary fat during canal pressurization has been suspected to trigger adult respiratory distress syndrome. The goal of the present study was to evaluate the effect, on the lungs, of a filter placed into the ipsilateral common iliac vein during medullary canal pressurization in a canine model. METHODS: With use of an established model of fat embolization, twelve mongrel dogs were randomized into two groups. In six dogs, a special filter was inserted percutaneously into the left common iliac vein while the dogs were under general anesthesia. In all dogs, the left femur and tibia were then pressurized by injection of bone cement and insertion of intramedullary rods. Hemodynamic measurements and echocardiographic images were recorded throughout the experiment. After one hour, the animals were killed and the lungs were harvested for histomorphometric analysis. RESULTS: Without the filter, the mean pulmonary artery pressure increased by 11.8 +/- 2.1 mm Hg (p < 0.001). With the filter, the mean pulmonary artery pressure increased by only 2.2 +/- 0.8 mm Hg (p < 0.02). Without the filter, there was a significant increase in the index of pulmonary vascular resistance as compared with the baseline value (p < 0.05). With the filter, there was no such increase. Histomorphometric analysis demonstrated that the presence of the filter reduced the absolute area of embolization and the volume percentages of lung and pulmonary vasculature embolized. CONCLUSIONS: In this canine experiment, temporary placement of a venous filter prior to medullary canal pressurization reduced the embolic load and minimized its hemodynamic effects.

Animals↗
PubMed2004

Non-union of acetabular fractures.

Non-unions of acetabulum are rare. Seven cases of acetabular non-unions are reported in this retrospective study. Five out of our seven patients had either transverse or associated transverse with posterior wall fractures. All patients had surgical stabilisation of their index fractures. A diagnosis of non-union was made at an average of 5.8 months from the original injury based on clinical and radiological features. Five of the six patients who underwent re-stabilisation and bone grafting of the non-union healed where as the remaining one did not heal after two attempts at re-stabilisation and was treated with excision arthroplasty. Two of the healed five, subsequently developed osteoarthritis and had total hip arthroplasty where as one patient had already developed degeneration of his hip at the time of diagnosis and hence treated with total hip arthroplasty. Analysis of the non-unions confirmed that fixation was unstable in all with residual displacement seen in two of them. In conclusion acetabular fracture non-union appear to be associated with transverse fractures and unstable fixation.

Acetabulum↗
PubMed2001

Assessment of osteoporosis using standard radiographs of the wrist.

BACKGROUND: This study evaluated the ability of the orthopaedic surgeon to radiographically assess bone density in the wrist with sufficient accuracy to determine which patients require treatment for osteoporosis. METHODS: Thirty-eight patients with unilateral distal radius fractures, 30 of whom were female, were included in this study. The mean age was 55 years (range 45 to 82). Standard radiographs of the fractured and normal wrists were taken. Dual energy x-ray absorptiometry was performed on the normal distal radius of all patients within 1 week of their injury. The radiographs were viewed in blinded randomized fashion on two separate occasions by three orthopaedic surgeons and once by a fourth. The participants were required to determine the presence of osteoporosis. Visual analog scales (VAS) were used to evaluate (1) porosity, (2) cortical thickness, (3) trabecular thickness, and (4) the number of trabeculae in the ultradistal radius. RESULTS: Intraobserver agreement assessing osteoporosis averaged 81% (kappa of 0.5393). VAS assessment was unreliable for all four parameters. Radiographic determination of osteoporosis had a specificity of 61% and a sensitivity of 61% using x-rays of the uninjured wrist. CONCLUSION: We conclude that orthopaedic surgeons cannot predict with sufficient accuracy using plain x-rays whether a patient is significantly osteoporotic.

Absorptiometry, Photon↗
PubMed1997

Evaluation of pelvic fractures. Clinical and radiologic.

This article gives the orthopedic surgeon a framework to use during the initial evaluation of a patient with a pelvic fracture in the emergency room. The essential elements of the assessment of instability, both clinically and radiologically, are given in this article. Examples of the major patterns of instability are provided.

Fractures, Bone↗
PubMed1997

Open pelvic fractures. A multicenter retrospective analysis.

A marked discrepancy exists in the reported mortality rates in patients with open pelvic fractures, ranging from 4.8% to 50%. A retrospective review of patients with open pelvic fractures was performed at three centers. Thirty-nine patients with open pelvic fractures were identified; the average age was 32. The average injury-severity score was 29 (13-75). There were 10 (26%) deaths. Factors that correlated with mortality and morbidity were instability of the pelvic fracture and the presence of a rectal injury. Delay in performing diverting colostomy correlated with a poor outcome. Previously described methods of treatment are still valid; however, there is a need for re-emphasis of early diverting colostomy in the patient with a rectal or perineal injury. A classification system for open pelvic fractures is proposed in this article.

Adult↗
PubMed1996

Fixation of segmental subtrochanteric fractures. A biomechanical study.

Segmental subtrochanteric fractures have been associated with high rates of malunion, nonunion, and implant failure. Although the use of second generation intramedullary nails with proximal interlocking in the femoral head has been advocated for these fractures, shaft fractures at the tip of short second generation intramedullary rod nails in clinical studies raise concerns about the mechanical suitability of these implants. No biomechanical data are available on the strength of fixation and mode of failure of these newer implants. This study compares the strength and failure mode of segmental subtrochanteric fractures stabilized with 3 current implants. Eighteen anatomic specimen femurs were obtained. The 3 implants tested were the Russell-Taylor reconstruction nail, a short intramedullary hip screw, and a long intramedullary hip screw. Each femur was instrumented and a segmental subtrochanteric fracture was created. The femurs were loaded in a Materials Testing System. The strength of the reconstruction nail group (2869 +/- 210 N) was significantly greater than for the short intramedullary rod hip screw (2330 +/- 490 N), and the long intramedullary rod hip screw (2181 +/- 244 N). The failure modes for the implants were: screw cut out of the femoral head for the reconstruction nail; fracture of the femoral shaft for the short intramedullary hip screw, and implant bending for the long intramedullary hip screw. This study suggests that the reconstruction nail is the superior implant for segmental subtrochanteric fractures of those tested. Implant bending and shaft fractures at lower loads make the 2 intramedullary rod hip screw implants less suitable.

Aged↗
PubMed1996

Small versus large diameter closed-section femoral nails for the treatment of femoral shaft fractures: is there a difference?

UNLABELLED: A retrospective series of 99 femoral shaft fractures treated by small diameter (10 and 11 mm) and large diameter (> 11 mm) closed section femoral nails from November 1989 to September 1993 was analyzed. No significant differences in the parameters of bony union and time to full weight bearing were seen between the two groups nor were there significant differences between the rate of secondary procedures. There were no broken nails in either group and there was no difference in the overall respiratory complication rate. CONCLUSION: No statistically significant differences existed between the small and large diameter groups except for the mean age and mean follow-up period. Small diameter nails can be used safely without the risk of nail breakage.

Adult↗
PubMed1995

Lateral extension of the ilioinguinal incision in the operative treatment of acetabulum fractures.

The choice of which decision to use for open reduction and internal fixation of complex acetabulum fractures depends on several variables. We report on 26 patients in whom a lateral extension of the ilioinguinal incision was used to achieve fracture reduction and stabilization. The lateral extension allowed visualization of the lateral ilium, in some cases passage of cerclage wires around the anterior and posterior columns, and in some cases placement of lateral to medial lag screws above the dome of the acetabulum. Reduction with a step of 1 mm or less and a gap of 3 mm or less with joint congruence was achieved in 21 patients (81 per cent). No patients had clinically significant heterotopic ossification. One patient had a transient postoperative femoral neuropathy, one a superficial infection, and one a deep infection. We recommend this lateral extension as an option during surgery of complex acetabular fractures through the ilioinguinal incision.

Acetabulum↗
PubMed1994

Comparison of torsional strength of humeral intramedullary nailing: a cadaveric study.

Control of rotation after intramedullary fixation of the humeral shaft has been observed to vary clinically. Two of the newer intramedullary nails specifically designed for the humerus were tested. Transverse and spiral fractures were created in 35 fresh-frozen cadaveric humeri. The constructs were tested in a materials testing system to evaluate in vitro the torsional strength of the nailed humeral fractures. Intact bones showed a mean peak torque of 53 +/- 17 Nm. The humeri fixed with the Russell-Taylor nail (n = 18) using one interlocking screw proximally and one distally showed a mean torsional strength of 10.4 +/- 3.6 Nm. The specimens fixed with the Seidel nail (n = 17), interlocked proximally with two screws and distally by the friction of three expanded flanges against the inner cortex, had a significantly lower mean torsional strength of 1.5 +/- 0.6 Nm (p < 0.0005). When compared with intact bones, constructs using the Russell-Taylor nail achieved 20% of mean peak torque. This improved rotational strength should permit an earlier return to full functional use of the extremity.

Aged↗
PubMed1991

Primary intramedullary nailing of open femoral shaft fractures.

The cases of 60 patients with 63 open femoral fractures treated by primary reamed intramedullary nailing were retrospectively reviewed. Twenty-two were classified as Type I open fractures, 26 as Type II and 15 as Type III open fractures by Gustilo's classification. All fractures were treated by wound debridement followed by immediate reamed intramedullary nailing. There were five early soft-tissue infections and three late deep infections. Of the late infections, only one was osteomyelitis (1.6%). There were three nonunions and seven malunions. All of the complications were dealt with effectively by standard methods. We concluded that primary reamed intramedullary nailing is an effective alternative for the treatment of Type I and II open femur fractures and for Type III open femur fractures associated with multiple trauma.

Adolescent↗
PubMed1989

Multiple-level noncontiguous spinal fractures.

Double-level noncontiguous spinal injury is a more common occurrence than generally appreciated. A large number of these patients have neurological injury. Because these injuries occur in patients who meet the criteria for categorization as multiple trauma patients, we feel that a complete radiographic survey of the spine must be accomplished in the emergency room in any situation where clinical assessment is impaired. Treatment must be individualized with the same guidelines for treatment as for the isolated injury in the majority of circumstances.

Adolescent↗
PubMed1986

Biodegradable resurfacing of the hip in dogs.

Arthroplasties of the hips in dogs using a biodegradable poly-L-lactide cup to protect the regenerating cartilage following removal of normal articular cartilage and the drilling of multiple full thickness defects into subchondral bone were performed to determine whether or not the repair response could be improved. The poly-L-lactide cup degraded in approximately 60 days. The regenerating cartilage was much better in the experimental than the control dogs initially, but ultimately failed, perhaps due to inadequate duration of protection of the immature cartilage by the arthroplasty material.

Animals↗
PubMed1977

The induction of chromosomal abnormalities by inhalational anaesthetics.

When Vicia faba root tips are exposed for 2 h to clinically useful concentrations of halothane or methoxyflurane in air, or to halothane in 80% nitrous oxide/20% oxygen, there is a transient increase in mitotic index and then abnormal interphase cells are produced in proportion to the anaesthetic concentrations. After exposure there is a period of mitotic inhibition during which the cells become partially synchronised. When colchicine-metaphase cells collected 28 h after exposure are compared with controls and with metaphases collected only 4 h after exposure, they show a significant increase in the incidence of aneuploidy, tetraploidy and the results of chromosome breakage. It is suggested that all the abnormalities seen can be accounted for by the effects of the anaesthetics on spindle movements, and that at the concentrations used the anaesthetics have no mutagenic effects on chromosomes in interphase.

Aneuploidy↗