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Patients With Rheumatoid Arthritis Have Higher Rate of Complications After Joint Replacement

December 12, 2012 by Leave a Comment

A recent study published in Arthritis and Rheumatism has reported that patients with rheumatoid arthritis have higher risk of complications following total joint replacement than patients of rheumatoid arthritis.

The study, a systematic review of the literature, by Bheeshma Ravi and colleagues has been published in December issue of Arthritis and Rheumatism.

With a background that most of the evidence regarding complications following total hip arthroplasty  and total knee arthroplasty  is based on studies of patients with osteoarthritis, the authors carried out present study to  review the current evidence regarding rates of THA/TKA complications in RA versus OA. [Read more...]

Filed Under: Hip Replacement, Joint Replacement, Knee Replacement, News Tagged With: , , , , , , , , ,

Photographs of Acteabular Cup With Cement Removed In Revision Arthroplasty

June 21, 2011 by Leave a Comment

46 years old adult male presented with dislocation of the prosthesis after total hip arthroplasty surgery. His xray revealed a acetabular cup in unacceptable position and thus a revision of acetabular cup was done.

Following images are of the removed acetabular cup from previous surgery.

Acetabular-Cup WIth Excess Cement
Note the excessive cement present. [Read more...]

Filed Under: Hip Replacement, Implants-Instruments, Joint Replacement Tagged With: , , , , ,

Periprosthetic Fracture Shaft Of Femur In A Patient With Bipolar Hemiarthroplasty

April 1, 2011 by Leave a Comment

Periprosthetic fractures are fractures that occur around the implants of joint replacement.

Following xray is of 82 years old male who had undergone bipolar hemiarthroplasty for fracture of neck of femur about 3 years before this episode.

he was brought to the hospital after complaint of increased thigh pain following fall while walking. Xray revealed the implant and a fracture in the femoral shaft around distal part of the stem.

periprosthetic-fracture-femur

Periprosthetic Fracture Femur

The fracture was undisplaced and was managed non operatively after patient chose the non operative means of treatment. The fracture united uneventfully.

Filed Under: Fracture Dislocations, Hip Replacement, Images, Radiology Tagged With: , , ,

Total Hip Replacement – Cemented Components

September 19, 2010 by Leave a Comment

In early designs the cement–bone interface was aimed for an intimate mechanical contact with rough bone or trabecular bone. The cement was not intended to bond to the stem.

Standard cemented acetabular components consist of a solid UHMWPE hemispherical shape, with grooves on the outer surface for keying to the cement.

A metal wire is usually embedded on the outside to measure the wear relative to the femoral head on radiographs. The range of motion  between the femoral neck and the socket is affected by [Read more...]

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Hip Replacement – Uncemented Componenets

September 14, 2010 by Leave a Comment

Uncemented components do not require use of cement for fixing the implant to  the bone. Successful fixation of uncemented components depends on achieving tolerable stresses at the implant–bone interface and minimizing interface micromotion.

The conditions responsible for fixation of uncemented stem depends on the surface of the stem, its cross-sectional shape, and the overall geometry.

Stem Surface.

Smooth stem surfaces are unsatisfactory when used without cement.  Rough surfaces and porous surface have been shown to perform better. [Read more...]

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Total Hip Replacement – Bone Implant Stresses and Factors Governing Them

August 22, 2010 by Leave a Comment

The implant material, its shape, size and the method of affects the  of stress transfer to the bone. Implant loosening, and  fracture of the femur or the implant are risks that arise from stress transfers to the bone. At the same time stress also provides stimulus for maintaining bone mass.

Modulus of elasticity of the implant material affects the stress that it would cause. A decrease in the modulus of the stem, stem length and cross sectional area  causes a decrease in the stress  in the stem. But it would increase the stress in the proximal third of the cement mass, which transfers these stresses to the surrounding bone. [Read more...]

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What Is Femoral Offset?

August 19, 2010 by Leave a Comment

Femoral offset is the distance from the center of rotation of the femoral head to a line dissecting the long axis of the femur. In case of  total replacement hip the the offset  is considered  as the  distance from the center of rotation of the femoral head to a line bissecting the long axis of the stem.

Normal femoral offset varies  between 30 amd 60 mm.

Femoral Offset

Image Credit: http://www.traumazamora.org/articulos/offset/offset.html

A decrease in femoral offset would move the femur closer to the pelvis medially. [Read more...]

Filed Under: Hip Replacement Tagged With: , , ,

Hip Replacement – Mechanics of The Hip

August 17, 2010 by Leave a Comment

Hip joint biomechanics are quite complex due to pelvic motion associated with it and range of movements it produces.

During normal gait, on heel-strike, the hip moves into 3o degree of flexion and at toe-off [when the foot is finally off the ground] about 10° of extension. The range of abduction to adduction is about 11°, and for internal-external rotation, the range is about 8°.

During different phases of gait cycle, different forces act on femoral head. Approximately two thirds of the hip force is produced by the abductors.

The directions of the resultant force on the joint are important to the function of total hips. [Read more...]

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