Hip replacement
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- This article discusses hip replacement in humans. For additional information on hip replacement in animals, specifically dogs, please see Hip replacement (animal)
Hip replacement is a medical procedure in which the hip joint is replaced by a synthetic implant. It is the most successful, cheapest and safest form of joint replacement surgery.
[edit] History
The earliest recorded attempts at hip replacement (Gluck T, 1891), which were carried out in Germany, used ivory to replace the femoral head (the ball on t In 1960 a Burmese orthopaedic surgeon, Dr. San Baw (29 June 1922 – 7 December 1984), pioneered the use of ivory hip prostheses to replace ununited fractures of the neck of femur ('hip bones'), when he first used an ivory prosthesis to replace the fractured hip bone of an 83 year old Burmese Buddhist nun, Daw Punya. This was done while Dr San Baw was the chief of orthopeadic surgery at Mandalay General Hospital in Manadalay, Burma. Dr San Baw used over 300 ivory hip replacements from the 1960s to 1980s. He presented a paper entitled 'Ivory hip replacements for ununited fractures of the neck of femur' at the conference of the British Orthopeadic Association held in London in September 1969. An 88% success rate was discerned in that Dr San Baw's patients ranging from the ages of 24 to 87 were able to walk, squat, ride the bicycle and play football a few weeks after their fractured hip bones were replaced with ivory prostheses. Dr San Baw's use of ivory was, at least in Burma during the 1960s, 1970s and 1980s (before the illicit ivory trade became rampant starting around the early 1990s) cheaper than metal. Moreover, due to the physical, mechanical, chemical, and biological qualities of ivory, it was found that there was a better 'biological bonding' of ivory with the human tissues nearby the ivory prostheses. An extract from Dr San Baw's paper, which he presented at the British Orthopeadic Association's Conference in 1969, is published in Journal of Bone and Joint Surgery (British edition), February 1970.
The modern artificial joint owes much to the work of John Charnley at Wrightington Hospital; his work in the field of tribology resulted in a design that completely replaced the other designs by the 1970s. Charnley's design consisted of 3 parts – (1) a metal (originally Stainless Steel) femoral component, (2) an Ultra high molecular weight polyethylene acetabular component, both of which were fixed to the bone using (3) special bone cement. The replacement joint, which was known as the Low Friction Arthroplasty, was lubricated with synovial fluid. The small femoral head (22.25mm) was chosen for its decreased wear rate however has relatively poor stability (the larger the head of a replacement the less likely it is to dislocate, but the more wear debris produced due to the increased surface area). For over two decades, the Charnley Low Friction Arthroplasty design was the most used system in the world, far surpassing the other available options (like McKee and Ring).
Due to longer living patients and hip replacements being more common, longer term problems have been noticed in the use of polyethylene acetabular cups. The wear debris from these components can cause Osteolysis, and the bond between the femeral component and the femur weakens, and this may require more surgery.
[edit] Techniques
There are several different incisions or approaches used to access the hip joint including the posterior (Kocher), anterolateral (Hardinge or Liverpool), and anterior (Smith-Peterson).
The posterior (Kocher) approach accesses the joint through the back, taking Piriformis and Quadratus internis off the lesser trochanter. This approach gives excellent access to the acetabulum and preserves the hip abductors however is supposed to have a higher dislocation rate.
The anterolateral approach is the most commonly used approach as it is also the usual approach for trauma replacements (hemiarthroplasties). The approach requires division of the hip abductors (Gluteus Medius and Minimus) in order to access the joint. The abductors may be lifted up by cutting of the greater trochanter and reapplying it afterwards using cables (as per Charnley), or may be divided at there tendinous portion and repaired using sutures.
In contrast to the posterior approach and lateral approach, the anterior approach uses a natural interval between soft tissue to gain access to the hip joint. The interval is found between the sartorius and tensor fascia latae. The main disadvantages to the anterior approach are that it risks damage to the lateral femoral cutaneous nerve, and it is not widely available to the public because fewer surgeons have been trained in this technique. Dr. Kristaps Keggi has been a pioneer and advocate of this approach for nearly 30 years. More recently, this approach has been advocated by Zimmer. This approach is not commonly used for hip arthroplasty.
