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Biomedical subjects

J Kenwright

Publications and source records attributed to J Kenwright.

66 records · Page 4Linked to original sources
PubMed1985

The influence of induced micromovement upon the healing of experimental tibial fractures.

Although it has been well established that fracture healing is influenced by the mechanical environment, the optimal parameters have not yet been established. In two groups of sheep an experimental tibial diaphysial fracture was created, and stabilised using external skeletal fixation. In one group rigid fixation was maintained throughout fracture healing; in the other group controlled axial micromovement, with a loading regime known to be osteogenic in intact bones, was applied for a short period daily. A significant improvement in healing was associated with the application of controlled micromovement. Data from these experiments provide the basis for improving the conditions for fracture healing and may assist in the prevention of delayed union.

Animals↗
PubMed1983

The influence on the spine of leg-length discrepancy after femoral fracture.

We investigated the spines of 15 patients who had significant leg-length inequality as a result of femoral shaft fractures sustained after skeletal maturity but below the age of 21 years. The patients were examined at least 10 years after fracture. The spines were studied clinically and radiographically before and after correction of leg-length inequality with a shoe-raise. Lateral spinal flexion was measured from radiographs. The lumbar scoliosis associated with the leg-length inequality was compensatory: after equalisation of leg-length the overall curve and the axial rotation were corrected completely. There was also an equal range of lateral flexion to either side after correction. Minor malalignments of the whole spine remained despite correction of the compensatory scoliosis, and within the lumbar spine correction of the scoliosis had not occurred equally at all levels. No patients complained of significant discomfort and neither structural abnormalities nor degenerative changes were seen on the radiographs.

Adolescent↗
PubMed1982

Scoliosis associated with limb-length inequality.

We reviewed the records and physical findings of twenty-three young adults who had had significant untreated limb-length inequality, present since childhood. The spine was studied radiographically and clinically before and after neutralization of the discrepancy of limb lengths with a lift. Movements of the spine also were measured. A significant asymmetry of lateral flexion of the spine remained in nearly all of the patients after neutralization of the discrepancy. The lumbar scoliosis associated with the limb-length inequality was compensatory and non-progressive, but abnormalities of the Cobb angle and of axial rotation remained in the young adults. No relationship was found between the underlying cause of the anisomelia or its duration and the severity of the spinal abnormality. The scoliosis was minor in patients with discrepancies of less than 2.2 centimeters. No patients complained of significant discomfort in the back, nor were degenerative radiographic changes evident there.

Adolescent↗
PubMed1979

The prognosis in congenital lower limb hypertrophy.

Twenty-eight patients with congenital total hypertrophy and ten patients with lower limb hypertrophy with congenital vascular abnormalities are reviewed. The pattern of increase in leg length discrepancy during growth and its influence on surgical management is discussed and the clinical features of the affected limbs are described. In congenital total hypertrophy the maximal increase in leg length discrepancy of more than 2.5 cm at age 4 years are likely to develop significant limb overgrowth that will require eventual surgical correction. In patients with congenital vascular abnormalities the change of leg length discrepancy was variable in degree and unpredictable in pattern, even in those with similar venous anomalies. The outcome for the limb was detergiography.

Adolescent↗
PubMed1970

Leg lengthening.

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Adolescent↗
PubMedDate not supplied

Force-displacement behaviour of biological tissue during distraction osteogenesis.

Limb lengthening and bone transport treatments are used frequently, and complications during treatment are common. Knowledge of the origin of tensile forces which resist distraction and the force-displacement response of biological tissues during extension would assist in reducing complication rates. Two tibial diaphyseal lengthenings carried out using an Ilizarov fixator were monitored by a displacement transducer to determine extension of the lengthening tissue (the regenerate bone), and by force transducers to determine tensile forces in the tissues that resist extension. The position of the force vector within a cross-section of the limb at the regenerate (provided by CT) was used to determine the origin of these forces. The muscle groups and adjacent fascia resisting extension were the gastrocnemius in one subject and the anterior and peroneal compartments in the other. In response to distraction, these tissues had relatively high stiffness (> 200 N/mm), less "immediate" displacement (< 35% of long term non-recoverable displacement) and inconsistent force relaxation properties (0-90%). In contrast, when the force vector was located in the vicinity of the regenerate, tissue exhibited lower stiffness (< 50 N/mm) and more immediate displacement (> 65% of long term nonrecoverable displacement), but also exhibited inconsistent force relaxation (0-67%).

Adaptation, Physiological↗
PubMedDate not supplied

Epiphyseal distraction for bony bridges: a biomechanical and morphologic study.

Partial physeal bridges were produced by resecting part of the lower femoral physis in 8-week-old rabbits. After 4 weeks, an external fixator, strain-gauged to measure distraction forces, was applied across the physis. Distraction was performed for 15 days: 1.0 mm/day medially and 0.5 mm/day laterally. Weekly radiographs were obtained. Animals were killed at 0, 3, and 6 weeks after distraction. Characteristic force patterns were evident if the bridge fractured. Medial fixator forces just before bridge fracture were very high (mean 89 N, SD 28 N), although forces in the lateral fixator were low (mean 25 N, SD 15 N). All animals killed 3 and 6 weeks after distraction ceased showed complete physeal closure. Results suggest that distraction epiphysiolysis may have high potential for producing premature physeal fusion.

Animals↗
PubMedDate not supplied

Biomechanical measurement of fracture healing.

Three techniques for measuring fracture healing are presented. These techniques are: (1) use of strain gauge measurements of the forces in an external fixator to determine fracture stiffness, (2) measurement of the vibration modes of a fractured long bone compared to the unfractured contralateral and (3) comparison of the ultrasound velocity across the fracture site with that for the normal unfractured bone. Examples of clinical results obtained using these techniques are presented, and the advantages and disadvantages of each technique are discussed.

Biomechanical Phenomena↗