Orthopedic Care and Consultation
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...]
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...]
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...]
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...]
Joint replacement is a common orthopedic procedure done worldwide. A joint replacement aims at of replacing painful, arthritic or diseased parts of the joint with artificial surfaces.
The artificial joint is called prosthesis.
Hip and knee replacements are very common form of joint replacements. In medical terms the joint replacement is called replacement arthroplasty or total arthroplasty or sometimes simply arthroplasty.
Actually arthroplasty means repair of the joint. Earlier, a popular form of arthroplasty was interpositional arthroplasty with interposition of some other tissue like skin, muscle or tendon to keep inflammatory surfaces apart. [Read more...]
Avascular necrosis (AVN) of head of femur occurs when blood supply to the head is jeopardized. That may occur when blood vessels are injured or the pressure within the bone rises enough to cause narrowing of blood vessels resulting in ischaemia of the bone.
The various known causes of avascular necrosis of hip are
There are percentage of people in whom the cause cannot be determined and are labeled as idiopathic AVN.
In uncorrectable painful deformities, it becomes necessary to perform either of two procedures. It is difficult to decide when to perform arthrodesis and when to do total joint replacement. Individual assessment should be carried out to aid in decision making. The treatment options should be discussed with the patient after evaluating his needs and expectation.
Most common indication for surgery is disabling pain. If involvement is unilateral and the opposite lower limb is relatively normal, arthrodesis is a good option.
Total joint replacement in bilateral knees is indicated with Stage IV or Stage V arthropathy when persistent knee pain is presesent.
Total hip replacement is indicated in Stage IV or Stage V hemophilic arthropathy when pain is persistent with severe disability not relieved by conservative measures. Arthroplasty of the elbow has been reported.
Arthrodesis of the ankle, subtalar and midtarsal joints in the foot, shoulder, or knee may be indicated when these joints are destroyed. The surgical technique is the same as in normal patients with the exception that percutaneous pins should not be utilized in hemophiliacs.
Osteoarthritis of hip is a major problem in Western world. About 10 million Americans reported having been diagnosed with osteoarthritis.
You are more likely to get it if you have a family history of the disease. Congenital or developmental defects like acetabular dysplasia, Legg-Calve-Perthes disease, slipped capital epiphysis may be implicated in as may as 80 percent of cases of hip osteoarthritis.
Risk increases with obesity or a previous hip injury. [Read more...]
Join Discussions