Biomedical subjects

M N Charles

Publications and source records attributed to M N Charles.

3 recordsLinked to original sources

PubMed2005

Fractures of distally-fixed femoral stems after revision arthroplasty.

We identified five (2.3%) fractures of the stem in a series of 219 revision procedures using a cementless, cylindrical, extensively porous-coated, distally-fixed femoral stem. Factors relating to the patients, the implant and the operations were compared with those with intact stems. Finite-element analysis was performed on two of the fractured implants. Factors associated with fracture of the stem were poor proximal bone support (type III-type IV; p = 0.001), a body mass index > 30; (p = 0.014), a smaller diameter of stem (< 13.5 mm; p = 0.007) and the use of an extended trochanteric osteotomy (ETO 4/5: p = 0.028). Finite-element analysis showed that the highest stresses on the stem occurred adjacent to the site of the fracture. The use of a strut graft wired over an extended trochanteric osteotomy in patients lacking proximal femoral cortical support decreased the stresses on the stem by 48%.We recommend the use of a strut allograft in conjunction with an extended trochanteric osteotomy in patients with poor proximal femoral bone stock.

Adult↗

PubMed2000

Properties of a hybrid plaster-fibreglass cast.

OBJECTIVE: To examine the suitability of a plaster-fibreglass hybrid cast for orthopedic applications, comparing them to plaster of Paris (POP) and fibreglass constructs. METHOD: Groups of 10 standardized hybrid, POP and fibreglass casts were studied. An Instron servohydraulic system was used to test the casts in 3-point bending and shear. OUTCOME MEASURES: Strength, stiffness, weight, thickness and cost of the 3 types of cast, and shear strength at the interface between the POP and fibreglass in the hybrid casts. RESULTS: The hybrid casts were twice as strong as the POP constructs, were stiffer and weighed 14% less but were thicker and cost 2.5 times more. They were almost as strong as and less than half the cost of the fibreglass constructs but were thicker, not as stiff, and weighed 42% more. The shear strength of the POP-fibreglass interface in the hybrid casts was higher than the 3-point bending strength of this construct by a factor of 3. CONCLUSIONS: Plaster-fibreglass hybrid casts should be considered for orthopedic use on the basis of their strength, stiffness, weight and cost, combined with their acknowledged advantages of good moulding ability and water resistance.

Analysis of Variance↗

PubMed1995

Percutaneous A1 pulley release: a cadaveric study.

Percutaneous A1 pulley release was performed on 17 fresh-frozen cadaveric hands with a 14-gauge angiocath needle. Each hand was then explored to assess the adequacy of release and the degree of injury to adjacent structures. Complete release of the A1 pulley was obtained in 45 of the 66 fingers and in 10 of the 17 thumbs. Significant injury to the flexor tendons was observed in two digits. All tendon injuries occurred along the line of the fibers. There were no digital nerve injuries. The release was within 2 mm of a thumb digital nerve in seven hands and the little finger ulnar digital nerve in two. In the thumb, the close proximity of the digital nerves makes percutaneous trigger digit release potentially hazardous. With the little finger held in abduction the risk of digital nerve injury or inadequate release is reduced. Percutaneous trigger finger release can be safely performed in the index, long, and ring fingers.

Cadaver↗