Anteroposterior and lateral views of knee replacement in 62 year old male.
Here is the AP view
Anteroposterior view of knee replacement
Here is the lateral view [Read more...]
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.
Note the excessive cement present. [Read more...]
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
The fracture was undisplaced and was managed non operatively after patient chose the non operative means of treatment. The fracture united uneventfully.
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...]
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...]
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...]
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.
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...]
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...]
Anteroposterior Xray Of Both Knees Showing Severe Osteoarthritis, Varus Deformity and Subluxation
March 12, 2010 By Leave a Comment
This xray belongs to 58 year old women who weighed 120 khs and had severe pain in both the knees for last 10 years. patient was unable to walk beyond 10 steps even with support.
She also had respiratory and cardiac ailments.
The xray in picture shows severely destroyed knees with varus deformity in both sides along with subluxation of the knee joints on both sides.
The patient had been advised total knee replacement [TKR] two years back but she refused. This time she had come with a request to get operated for total knee replacement but her physician told her about the risk involved due to her medical illness.
The patient again refused.
Joint Replacement – History, Present and Future
February 6, 2010 By Leave a Comment
History of joint replacement is quite interesting. Earliest method for treating arthritis was interposition arthroplasty using soft and flexible materials.
But these substances lacked strengths and were not rigid enough to support.
Metal and glass were tried next in the form of condylar shapes attached to one of the joint. These provided some amount of success but joint apposition was not perfect and neither were kinematics of the joint.
Modern day joint replacement began in the early 1960s. This was hallmarked by introduction of cemented metal-polyethylene components for the hip. Later Gunston used this technique in the knee also.
Charnley prop0sed following principles of arthroplasty which are still valid today. [Read more...]
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