Hip replacement

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Hip replacement_table_infobox_0

Hip replacementHip replacement_header_cell_0_0_0
Other namesHip replacement_header_cell_0_1_0 Hip athroplastyHip replacement_cell_0_1_1
ICD-9-CMHip replacement_header_cell_0_2_0 Hip replacement_cell_0_2_1
MeSHHip replacement_header_cell_0_3_0 Hip replacement_cell_0_3_1
MedlinePlusHip replacement_header_cell_0_4_0 Hip replacement_cell_0_4_1

Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement_sentence_0

Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Hip replacement_sentence_1

Such joint replacement orthopaedic surgery is generally conducted to relieve arthritis pain or in some hip fractures. Hip replacement_sentence_2

A total hip replacement (total hip arthroplasty or THA) consists of replacing both the acetabulum and the femoral head while hemiarthroplasty generally only replaces the femoral head. Hip replacement_sentence_3

Hip replacement is currently one of the most common orthopaedic operations, though patient satisfaction short- and long-term varies widely. Hip replacement_sentence_4

Approximately 58% of total hip replacements are estimated to last 25 years. Hip replacement_sentence_5

The average cost of a total hip replacement in 2012 was $40,364 in the United States, and about $7,700 to $12,000 in most European countries. Hip replacement_sentence_6

Medical uses Hip replacement_section_0

Total hip replacement is most commonly used to treat joint failure caused by osteoarthritis. Hip replacement_sentence_7

Other indications include rheumatoid arthritis, avascular necrosis, traumatic arthritis, protrusio acetabuli, certain hip fractures, benign and malignant bone tumors, arthritis associated with Paget's disease, ankylosing spondylitis and juvenile rheumatoid arthritis. Hip replacement_sentence_8

The aims of the procedure are pain relief and improvement in hip function. Hip replacement_sentence_9

Hip replacement is usually considered only after other therapies, such as physical therapy and pain medications, have recently failed. Hip replacement_sentence_10

Risks Hip replacement_section_1

Risks and complications in hip replacement are similar to those associated with all joint replacements. Hip replacement_sentence_11

They can include infection, dislocation, limb length inequality, loosening, impingement, osteolysis, metal sensitivity, nerve palsy, chronic pain and death. Hip replacement_sentence_12

Weight loss surgery before a hip replacement does not appear to change outcomes. Hip replacement_sentence_13

Infection Hip replacement_section_2

Infection is one of the most common causes for revision of a total hip replacement, along with loosening and dislocation. Hip replacement_sentence_14

The incidence of infection in primary hip replacement is around 1% or less in the United States. Hip replacement_sentence_15

Risk factors for infection include obesity, diabetes, smoking, immunosuppressive medications or diseases, and history of infection. Hip replacement_sentence_16

Modern diagnosis of infection around a total knee replacement is based on the Musculoskeletal Infection Society (MSIS) criteria. Hip replacement_sentence_17

They are: Hip replacement_sentence_18

Hip replacement_ordered_list_0

  1. There is a sinus tract communicating with the prosthesis; orHip replacement_item_0_0
  2. A pathogen is isolated by culture from at least two separate tissue or fluid samples obtained from the affected prosthetic joint;Hip replacement_item_0_1

or Hip replacement_sentence_19

Four of the following six criteria exist: Hip replacement_sentence_20

Hip replacement_ordered_list_1

  1. Elevated serum erythrocyte sedimentation rate (ESR>30mm/hr) and serum C-reactive protein (CRP>10 mg/L) concentration,Hip replacement_item_1_2
  2. Elevated synovial leukocyte count,Hip replacement_item_1_3
  3. Elevated synovial neutrophil percentage (PMN%),Hip replacement_item_1_4
  4. Presence of purulence in the affected joint,Hip replacement_item_1_5
  5. Isolation of a microorganism in one culture of periprosthetic tissue or fluid, orHip replacement_item_1_6
  6. Greater than five neutrophils per high-power field in five high-power fields observed from histologic analysis of periprosthetic tissue at ×400 magnification.Hip replacement_item_1_7

None of the above laboratory tests has 100% sensitivity or specificity for diagnosing infection. Hip replacement_sentence_21

Specificity improves when the tests are performed in patients in whom clinical suspicion exists. Hip replacement_sentence_22

ESR and CRP remain good 1st line tests for screening (high sensitivity, low specificity). Hip replacement_sentence_23

Aspiration of the joint remains the test with the highest specificity for confirming infection. Hip replacement_sentence_24

Dislocation Hip replacement_section_3

Dislocation is the most common complication of hip replacement surgery. Hip replacement_sentence_25

The most common causes vary by the duration since the surgery. Hip replacement_sentence_26

Hip prosthesis dislocation mostly occurs in the first three months after insertion, mainly because of incomplete scar formation and relaxed soft tissues. Hip replacement_sentence_27

It takes eight to twelve weeks for the soft tissues injured or cut during surgery to heal. Hip replacement_sentence_28

During this period, the hip ball can come out of the socket. Hip replacement_sentence_29

The chance of this is diminished if less tissue is cut, if the tissue cut is repaired and if large diameter head balls are used. Hip replacement_sentence_30

Dislocations occurring between three months and five years after insertion usually occur due to malposition of the components, or dysfunction of nearby muscles. Hip replacement_sentence_31

Risk factors of late dislocation (after five years) mainly include: Hip replacement_sentence_32

Hip replacement_unordered_list_2

  • Female genderHip replacement_item_2_8
  • Younger age at primary hip arthroplastyHip replacement_item_2_9
  • Previous subluxation without complete dislocationHip replacement_item_2_10
  • Previous traumaHip replacement_item_2_11
  • Substantial weight lossHip replacement_item_2_12
  • Recent onset or progression of dementia or a neurological disorderHip replacement_item_2_13
  • Malposition of the cupHip replacement_item_2_14
  • Wear of the liner, particularly when it causes movement of the head of more than 2 mm within the cup compared to its original positionHip replacement_item_2_15
  • Prosthesis loosening with migrationHip replacement_item_2_16

Surgeons who perform more of the operations each year tend to have fewer patients dislocate. Hip replacement_sentence_33

Doing the surgery from an anterior approach seems to lower dislocation rates when small diameter heads are used, but the benefit has not been shown when compared to modern posterior incisions with the use of larger diameter heads. Hip replacement_sentence_34

The use of larger diameter head size does in itself decrease the risk of dislocation, even though this correlation is only found in head sizes up to 28 mm, thereafter no additional decrease in dislocation rate is found. Hip replacement_sentence_35

People can decrease the risk further by keeping the leg out of certain positions during the first few months after surgery. Hip replacement_sentence_36

Limb length inequality Hip replacement_section_4

Most adults prior to a hip replacement have a limb length inequality of 0–2 cm which they were born with and which causes no deficits. Hip replacement_sentence_37

It is common for people to feel a limb length inequality after total hip replacement. Hip replacement_sentence_38

Sometimes the leg seems long immediately after surgery when in fact both are equal length. Hip replacement_sentence_39

An arthritic hip can develop contractures that make the leg behave as if it is short. Hip replacement_sentence_40

When these are relieved with replacement surgery and normal motion and function are restored, the body feels that the limb is now longer than it was. Hip replacement_sentence_41

This feeling usually subsides by 6 months after surgery as the body adjusts to the new hip joint. Hip replacement_sentence_42

The cause of this feeling is variable, and usually related to abductor muscle weakness, pelvic obliquity, and minor lengthening of the hip during surgery (<1 cm) to achieve stability and restore the joint to pre-arthritic mechanics. Hip replacement_sentence_43

If the limb length difference remains bothersome to the patient more than 6 months after surgery, a shoe lift can be used. Hip replacement_sentence_44

Only in extreme cases is surgery required for correction. Hip replacement_sentence_45

Fracture Hip replacement_section_5

Intraoperative fractures may occur. Hip replacement_sentence_46

After surgery, bones with internal fixation devices in situ are at risk of periprosthetic fractures at the end of the implant, an area of relative mechanical stress. Hip replacement_sentence_47

Post-operative femoral fractures are graded by the Vancouver classification. Hip replacement_sentence_48

Vein thrombosis Hip replacement_section_6

Venous thrombosis such as deep vein thrombosis and pulmonary embolism are relatively common following hip replacement surgery. Hip replacement_sentence_49

Standard treatment with anticoagulants is for 7–10 days; however treatment for more than 21 days may be superior. Hip replacement_sentence_50

Extended-duration anticoagulants (up to 35 days following surgery) may prevent VTE in people undergoing hip replacement surgery. Hip replacement_sentence_51

Research from 2013 has on the other hand suggested that anticoagulants in otherwise healthy patients undergoing a so-called fast track protocol with hospital stays under five days, might only be necessary while in the hospital. Hip replacement_sentence_52

There is emerging evidence supporting the use of aspirin for venous thromboembolism prophylaxis. Hip replacement_sentence_53

Large randomised control trials have suggested that aspirin is non inferior to low-molecular weight heparins and rivaroxaban. Hip replacement_sentence_54

However, there is uncertainty if aspirin is appropriate in all cases, especially people who have additional risk factors for venous thromboembolisms or may be at risk of being aspirin resistant. Hip replacement_sentence_55

Some physicians and patients may consider having an ultrasonography for deep vein thrombosis after hip replacement. Hip replacement_sentence_56

However, this kind of screening should only be done when indicated because to perform it routinely would be unnecessary health care. Hip replacement_sentence_57

Intermittent pneumatic compression (IPC) devices are sometimes used for prevention of blood clots following total hip replacement. Hip replacement_sentence_58

While there are a variety of different devices, it is currently unclear whether one is more effective than another. Hip replacement_sentence_59

Osteolysis Hip replacement_section_7

Many long-term problems with hip replacements are the result of osteolysis. Hip replacement_sentence_60

This is the loss of bone caused by the body's reaction to polyethylene wear debris, fine bits of plastic that come off the cup liner over time. Hip replacement_sentence_61

An inflammatory process causes bone resorption that may lead to subsequent loosening of the hip implants and even fractures in the bone around the implants. Hip replacement_sentence_62

In an attempt to eliminate the generation of wear particles, ceramic bearing surfaces are being used in the hope that they will have less wear and less osteolysis with better long-term results. Hip replacement_sentence_63

Metal cup liners joined with metal heads (metal-on-metal hip arthroplasty) were also developed for similar reasons. Hip replacement_sentence_64

In the lab these show excellent wear characteristics and benefit from a different mode of lubrication. Hip replacement_sentence_65

At the same time that these two bearing surfaces were being developed, highly cross linked polyethylene plastic liners were also developed. Hip replacement_sentence_66

The greater cross linking significantly reduces the amount of plastic wear debris given off over time. Hip replacement_sentence_67

The newer ceramic and metal prostheses do not always have the long-term track record of established metal on poly bearings. Hip replacement_sentence_68

Ceramic pieces can break leading to catastrophic failure. Hip replacement_sentence_69

This occurs in about 2% of the implants placed. Hip replacement_sentence_70

They may also cause an audible, high pitched squeaking noise with activity. Hip replacement_sentence_71

Metal-on-metal arthroplasty releases metal debris into the body raising concerns about the potential dangers of these accumulating over time. Hip replacement_sentence_72

Highly cross linked polyethylene is not as strong as regular polyethylene. Hip replacement_sentence_73

These plastic liners can crack or break free of the metal shell that holds them. Hip replacement_sentence_74

Loosening Hip replacement_section_8

On radiography, it is normal to see thin radiolucent areas of less than 2 mm around hip prosthesis components, or between a cement mantle and bone. Hip replacement_sentence_75

However, these may still indicate loosening of the prosthesis if they are new or changing, and areas greater than 2 mm may be harmless if they are stable. Hip replacement_sentence_76

The most important prognostic factors of cemented cups are absence of radiolucent lines in DeLee and Charnley zone I, as well as adequate cement mantle thickness. Hip replacement_sentence_77

In the first year after insertion of uncemented femoral stems, it is normal to have mild subsidence (less than 10 mm). Hip replacement_sentence_78

The direct anterior approach has been shown to itself be a risk factor for early femoral component loosening. Hip replacement_sentence_79

Metal sensitivity Hip replacement_section_9

Concerns are being raised about the metal sensitivity and potential dangers of metal particulate debris. Hip replacement_sentence_80

New publications have demonstrated development of pseudotumors, soft tissue masses containing necrotic tissue, around the hip joint. Hip replacement_sentence_81

It appears these masses are more common in women and these patients show a higher level of iron in the blood. Hip replacement_sentence_82

The cause is unknown and is probably multifactorial. Hip replacement_sentence_83

There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. Hip replacement_sentence_84

Metal hypersensitivity is a well-established phenomenon and is common, affecting about 10–15% of the population. Hip replacement_sentence_85

Contact with metals can cause immune reactions such as skin hives, eczema, redness and itching. Hip replacement_sentence_86

Although little is known about the short- and long-term pharmacodynamics and bioavailability of circulating metal degradation products in vivo, there have been many reports of immunologic type responses temporally associated with implantation of metal components. Hip replacement_sentence_87

Individual case reports link hypersensitivity immune reactions with adverse performance of metallic clinical cardiovascular, orthopedic and plastic surgical and dental implants. Hip replacement_sentence_88

Metal toxicity Hip replacement_section_10

Main article: Metallosis Hip replacement_sentence_89

Most hip replacements consist of cobalt and chromium alloys, or titanium. Hip replacement_sentence_90

Stainless steel is no longer used. Hip replacement_sentence_91

All implants release their constituent ions into the blood. Hip replacement_sentence_92

Typically these are excreted in the urine, but in certain individuals the ions can accumulate in the body. Hip replacement_sentence_93

In implants which involve metal-on-metal contact, microscopic fragments of cobalt and chromium can be absorbed into the person's bloodstream. Hip replacement_sentence_94

There are reports of cobalt toxicity with hip replacement, particularly metal-on-metal hip replacements, which are no longer in use. Hip replacement_sentence_95

Use of metal on metal hip replacements from the 1970's were discontinued in the 1980s, and 1990s, particularly after the discovery of aseptic lymphocyte-dominant vasculitis-associated lesions (ALVAL). Hip replacement_sentence_96

The FDA's 510k approval process, allowed companies to get new and 'improved' metal on metal hips approved without much clinical testing. Hip replacement_sentence_97

Again, some with these hips are experiencing the same reactions to the metal debris and some devices have been recalled, like the DePuy ASR. Hip replacement_sentence_98

Nerve palsy Hip replacement_section_11

Post operative sciatic nerve palsy is another possible complication. Hip replacement_sentence_99

The incidence of this complication is low. Hip replacement_sentence_100

Femoral nerve palsy is another but much more rare complication. Hip replacement_sentence_101

Both of these will typically resolve over time, but the healing process is slow. Hip replacement_sentence_102

Patients with pre-existing nerve injury are at greater risk of experiencing this complication and are also slower to recover. Hip replacement_sentence_103

Chronic pain Hip replacement_section_12

A few patients who have had a hip replacement suffer chronic pain after the surgery. Hip replacement_sentence_104

Groin pain can develop if the muscle that raises the hip (iliopsoas) rubs against the edge of the acetabular cup. Hip replacement_sentence_105

Bursitis can develop at the trochanter where a surgical scar crosses the bone, or if the femoral component used pushes the leg out to the side too far. Hip replacement_sentence_106

Also some patients can experience pain in cold or damp weather. Hip replacement_sentence_107

Incision made in the front of the hip (anterior approach) can cut a nerve running down the thigh leading to numbness in the thigh and occasionally chronic pain at the point where the nerve was cut (a neuroma). Hip replacement_sentence_108

Death Hip replacement_section_13

The rate of perioperative mortality for elective hip replacements is significantly less than 1%. Hip replacement_sentence_109

Metal-on-metal hip implant failure Hip replacement_section_14

See also: Implant failure Hip replacement_sentence_110

By 2010, reports in the orthopaedic literature increasingly cited the problem of early failure of metal on metal prostheses in a small percentage of patients. Hip replacement_sentence_111

Failures may relate to release of minute metallic particles or metal ions from wear of the implants, causing pain and disability severe enough to require revision surgery in 1–3% of patients. Hip replacement_sentence_112

Design deficits of some prothesis models, especially with heat-treated alloys and a lack of special surgical experience accounting for most of the failures. Hip replacement_sentence_113

In 2010, surgeons at medical centers such as the Mayo Clinic reported reducing their use of metal-on-metal implants by 80 percent over the previous year in favor of those made from other materials, like combinations of metal and plastic. Hip replacement_sentence_114

The cause of these failures remain controversial, and may include both design factors, technique factors, and factors related to patient immune responses (allergy type reactions). Hip replacement_sentence_115

In the United Kingdom the Medicines and Healthcare products Regulatory Agency commenced an annual monitoring regime for metal-on-metal hip replacement patients from May 2010. Hip replacement_sentence_116

Data which are shown in The Australian Orthopaedic Association's 2008 National Joint replacement registry, a record of nearly every hip implanted in that country over the previous 10 years, tracked 6,773 BHR (Birmingham Hip Resurfacing) Hips and found that less than 0.33% may have been revised due to the patient's reaction to the metal component. Hip replacement_sentence_117

Other similar metal-on-metal designs have not fared as well, where some reports show 76% to 100% of the people with these metal-on-metal implants and have aseptic implant failures requiring revision also have evidence of histological inflammation accompanied by extensive lymphocyte infiltrates, characteristic of delayed type hypersensitivity responses. Hip replacement_sentence_118

It is not clear to what extent this phenomenon negatively affects orthopedic patients. Hip replacement_sentence_119

However, for patients presenting with signs of an allergic reactions, evaluation for sensitivity should be conducted. Hip replacement_sentence_120

Removal of the device that is not needed should be considered, since removal may alleviate the symptoms. Hip replacement_sentence_121

Patients who have allergic reactions to cheap jewelry are more likely to have reactions to orthopedic implants. Hip replacement_sentence_122

There is increasing awareness of the phenomenon of metal sensitivity and many surgeons now take this into account when planning which implant is optimal for each patient. Hip replacement_sentence_123

On March 12, 2012, The Lancet published a study, based on data from the National Joint Registry of England and Wales, finding that metal-on-metal hip implants failed at much greater rates than other types of hip implants and calling for a ban on all metal-on-metal hips. Hip replacement_sentence_124

The analysis of 402,051 hip replacements showed that 6.2% of metal-on-metal hip implants had failed within five years, compared to 1.7% of metal-on-plastic and 2.3% of ceramic-on-ceramic hip implants. Hip replacement_sentence_125

Each 1 mm (0.039 in) increase in head size of metal-on-metal hip implants was associated with a 2% increase of failure. Hip replacement_sentence_126

Surgeons of the British Hip Society are recommending that large head metal-on-metal implants should no longer be performed. Hip replacement_sentence_127

On February 10, 2011, the U.S. FDA issued an advisory on metal-metal hip implants, stating it was continuing to gather and review all available information about metal-on-metal hip systems. Hip replacement_sentence_128

On June 27–28, 2012, an advisory panel met to decide whether to impose new standards, taking into account findings of the study in The Lancet. Hip replacement_sentence_129

No new standards, such as routine checking of blood metal ion levels, were set, but guidance was updated. Hip replacement_sentence_130

Currently, FDA has not required hip implants to be tested in clinical trials before they can be sold in the U.S. Hip replacement_sentence_131

Instead, companies making new hip implants only need to prove that they are "substantially equivalent" to other hip implants already on the market. Hip replacement_sentence_132

The exception is metal-on-metal implants, which were not tested in clinical trials but because of the high revision rate of metal-on-metal hips, in the future the FDA has stated that clinical trials will be required for approval and that post-market studies will be required to keep metal on metal hip implants on the market. Hip replacement_sentence_133

Modern process Hip replacement_section_15

The modern artificial joint owes much to the 1962 work of Sir John Charnley at Wrightington Hospital. Hip replacement_sentence_134

His work in the field of tribology resulted in a design that almost completely replaced the other designs by the 1970s. Hip replacement_sentence_135

Charnley's design consisted of three parts: Hip replacement_sentence_136

Hip replacement_ordered_list_3

  1. stainless steel one-piece femoral stem and headHip replacement_item_3_17
  2. polyethylene (originally Teflon), acetabular component, both of which were fixed to the bone usingHip replacement_item_3_18
  3. PMMA (acrylic) bone cementHip replacement_item_3_19

The replacement joint, which was known as the Low Friction Arthroplasty, was lubricated with synovial fluid. Hip replacement_sentence_137

The small femoral head (⁄8 in (22.2 mm)) was chosen for Charnley's belief that it would have lower friction against the acetabular component and thus wear out the acetabulum more slowly. Hip replacement_sentence_138

Unfortunately, the smaller head dislocated more easily. Hip replacement_sentence_139

Alternative designs with larger heads such as the Mueller prosthesis were proposed. Hip replacement_sentence_140

Stability was improved, but acetabular wear and subsequent failure rates were increased with these designs. Hip replacement_sentence_141

The Teflon acetabular components of Charnley's early designs failed within a year or two of implantation. Hip replacement_sentence_142

This prompted a search for a more suitable material. Hip replacement_sentence_143

A German salesman showed a polyethylene gear sample to Charnley's machinist, sparking the idea to use this material for the acetabular component. Hip replacement_sentence_144

The UHMWPE acetabular component was introduced in 1962. Hip replacement_sentence_145

Charnley's other major contribution was to use polymethylmethacrylate (PMMA) bone cement to attach the two components to the bone. Hip replacement_sentence_146

For over two decades, the Charnley Low Friction Arthroplasty, and derivative designs were the most used systems in the world. Hip replacement_sentence_147

It formed the basis for all modern hip implants. Hip replacement_sentence_148

The Exeter hip stem was developed in the United Kingdom during the same time as the Charnley device. Hip replacement_sentence_149

Its development occurred following a collaboration between Orthopaedic Surgeon Robin Ling and University of Exeter engineer Clive Lee and it was first implanted at the Princess Elizabeth Orthopaedic Hospital in Exeter in 1970. Hip replacement_sentence_150

The Exeter Hip is a cemented device, but with a slightly different stem geometry. Hip replacement_sentence_151

Both designs have shown excellent long-term durability when properly placed and are still widely used in slightly modified versions. Hip replacement_sentence_152

Early implant designs had the potential to loosen from their attachment to the bones, typically becoming painful ten to twelve years after placement. Hip replacement_sentence_153

In addition, erosion of the bone around the implant was seen on x-rays. Hip replacement_sentence_154

Initially, surgeons believed this was caused by an abnormal reaction to the cement holding the implant in place. Hip replacement_sentence_155

That belief prompted a search for an alternative method to attach the implants. Hip replacement_sentence_156

The Austin Moore device had a small hole in the stem into which bone graft was placed before implanting the stem. Hip replacement_sentence_157

It was hoped bone would then grow through the window over time and hold the stem in position. Hip replacement_sentence_158

Success was unpredictable and the fixation not very robust. Hip replacement_sentence_159

In the early 1980s, surgeons in the United States applied a coating of small beads to the Austin Moore device and implanted it without cement. Hip replacement_sentence_160

The beads were constructed so that gaps between beads matched the size of the pores in native bone. Hip replacement_sentence_161

Over time, bone cells from the patient would grow into these spaces and fix the stem in position. Hip replacement_sentence_162

The stem was modified slightly to fit more tightly into the femoral canal, resulting in the Anatomic Medullary Locking (AML) stem design. Hip replacement_sentence_163

With time, other forms of stem surface treatment and stem geometry have been developed and improved. Hip replacement_sentence_164

Initial hip designs were made of a one-piece femoral component and a one-piece acetabular component. Hip replacement_sentence_165

Current designs have a femoral stem and separate head piece. Hip replacement_sentence_166

Using an independent head allows the surgeon to adjust leg length (some heads seat more or less onto the stem) and to select from various materials from which the head is formed. Hip replacement_sentence_167

A modern acetabulum component is also made up of two parts: a metal shell with a coating for bone attachment and a separate liner. Hip replacement_sentence_168

First the shell is placed. Hip replacement_sentence_169

Its position can be adjusted, unlike the original cemented cup design which are fixed in place once the cement sets. Hip replacement_sentence_170

When proper positioning of the metal shell is obtained, the surgeon may select a liner made from various materials. Hip replacement_sentence_171

To combat loosening caused by polyethylene wear debris, hip manufacturers developed improved and novel materials for the acetabular liners. Hip replacement_sentence_172

Ceramic heads mated with regular polyethylene liners or a ceramic liner were the first significant alternative. Hip replacement_sentence_173

Metal liners to mate with a metal head were also developed. Hip replacement_sentence_174

At the same time these designs were being developed, the problems that caused polyethylene wear were determined and manufacturing of this material improved. Hip replacement_sentence_175

Highly crosslinked UHMWPE was introduced in the late 1990s. Hip replacement_sentence_176

The most recent data comparing the various bearing surfaces has shown no clinically significant differences in their performance. Hip replacement_sentence_177

Potential early problems with each material are discussed below. Hip replacement_sentence_178

Performance data after 20 or 30 years may be needed to demonstrate significant differences in the devices. Hip replacement_sentence_179

All newer materials allow use of larger diameter femoral heads. Hip replacement_sentence_180

Use of larger heads significantly decreases the chance of the hip dislocating, which remains the greatest complication of the surgery. Hip replacement_sentence_181

When currently available implants are used, cemented stems tend to have a better longevity than uncemented stems. Hip replacement_sentence_182

No significant difference is observed in the clinical performance of the various methods of surface treatment of uncemented devices. Hip replacement_sentence_183

Uncemented stems are selected for patients with good quality bone that can resist the forces needed to drive the stem in tightly. Hip replacement_sentence_184

Cemented devices are typically selected for patients with poor quality bone who are at risk of fracture during stem insertion. Hip replacement_sentence_185

Cemented stems are less expensive due to lower manufacturing cost, but require good surgical technique to place them correctly. Hip replacement_sentence_186

Uncemented stems can cause pain with activity in up to 20% of patients during the first year after placement as the bone adapts to the device. Hip replacement_sentence_187

This is rarely seen with cemented stems. Hip replacement_sentence_188

Techniques Hip replacement_section_16

There are several incisions, defined by their relation to the gluteus medius. Hip replacement_sentence_189

The approaches are posterior (Moore), lateral (Hardinge or Liverpool), antero-lateral (Watson-Jones), anterior (Smith-Petersen) and greater trochanter osteotomy. Hip replacement_sentence_190

There is no compelling evidence in the literature for any particular approach. Hip replacement_sentence_191

Posterior approach Hip replacement_section_17

The posterior (Moore or Southern) approach accesses the joint and capsule through the back, taking piriformis muscle and the short external rotators of the femur. Hip replacement_sentence_192

This approach gives excellent access to the acetabulum and femur and preserves the hip abductors and thus minimizes the risk of abductor dysfunction post operatively. Hip replacement_sentence_193

It has the advantage of becoming a more extensile approach if needed. Hip replacement_sentence_194

Critics cite a higher dislocation rate, although repair of the capsule, piriformis and the short external rotators along with use of modern large diameter head balls reduces this risk. Hip replacement_sentence_195

Limited evidence suggests that the posterior approach may cause less nerve damage. Hip replacement_sentence_196

Lateral approach Hip replacement_section_18

The lateral approach is also commonly used for hip replacement. Hip replacement_sentence_197

The approach requires elevation of the hip abductors (gluteus medius and gluteus minimus) to access the joint. Hip replacement_sentence_198

The abductors may be lifted up by osteotomy of the greater trochanter and reapplying it afterwards using wires (as per Charnley), or may be divided at their tendinous portion, or through the functional tendon (as per Hardinge) and repaired using sutures. Hip replacement_sentence_199

Although this approach has a lower dislocation risk than the posterior approach, critics note that occasionally the abductor muscles do not heal back on, leading to pain and weakness which is often very difficult to treat. Hip replacement_sentence_200

Antero-lateral approach Hip replacement_section_19

The anterolateral approach develops the interval between the tensor fasciae latae and the gluteus medius. Hip replacement_sentence_201

The Gluteus medius, gluteus minimus and hip capsule are detached from the anterior (front) for the greater trochanter and femoral neck and then repaired with heavy suture after the replacement of the joint. Hip replacement_sentence_202

Anterior approach Hip replacement_section_20

The anterior approach uses an interval between the sartorius muscle and tensor fasciae latae. Hip replacement_sentence_203

Dr. Joel Matta and Dr. Bert Thomas have adapted this approach, which was commonly used for pelvic fracture repair surgery, for use when performing hip replacement. Hip replacement_sentence_204

When used with older hip implant systems that had a small diameter head, dislocation rates were reduced compared to surgery performed through a posterior approach. Hip replacement_sentence_205

With modern implant designs, dislocation rates are similar between the anterior and posterior approaches. Hip replacement_sentence_206

The anterior approach has been shown in studies to variably improve early functional recovery, with possible complications of femoral component loosening and early revision compared to other approaches Hip replacement_sentence_207

Minimally invasive approaches Hip replacement_section_21

The dual incision approach and other minimally invasive surgery seeks to reduce soft tissue damage through reducing the size of the incision. Hip replacement_sentence_208

However, component positioning accuracy and visualization of the bone structures can be significantly impaired as the approaches get smaller. Hip replacement_sentence_209

This can result in unintended fractures and soft tissue injury. Hip replacement_sentence_210

The majority of current orthopedic surgeons use a "minimally invasive" approach compared to traditional approaches which were quite large comparatively. Hip replacement_sentence_211

Computer-assisted surgery and robotic surgery techniques are also available to guide the surgeon to provide enhanced accuracy. Hip replacement_sentence_212

Several commercial CAS and robotic systems are available for use worldwide. Hip replacement_sentence_213

Improved patient outcomes and reduced complications have not been demonstrated when these systems are used when compared to standard techniques. Hip replacement_sentence_214

Implants Hip replacement_section_22

The prosthetic implant used in hip replacement consists of three parts: the acetabular cup, the femoral component, and the articular interface. Hip replacement_sentence_215

Options exist for different people and indications. Hip replacement_sentence_216

The evidence for a number of newer devices is not very good, including: ceramic-on-ceramic bearings, modular femoral necks, and uncemented monoblock cups. Hip replacement_sentence_217

Correct selection of the prosthesis is important. Hip replacement_sentence_218

Acetabular cup Hip replacement_section_23

The acetabular cup is the component which is placed into the acetabulum (hip socket). Hip replacement_sentence_219

Cartilage and bone are removed from the acetabulum and the acetabular cup is attached using friction or cement. Hip replacement_sentence_220

Some acetabular cups are one piece, while others are modular. Hip replacement_sentence_221

One-piece (monobloc) shells are either UHMWPE or metal, they have their articular surface machined on the inside surface of the cup and do not rely on a locking mechanism to hold a liner in place. Hip replacement_sentence_222

A monobloc polyethylene cup is cemented in place while a metal cup is held in place by a metal coating on the outside of the cup. Hip replacement_sentence_223

Modular cups consist of two pieces, a shell and liner. Hip replacement_sentence_224

The shell is made of metal; the outside has a porous coating while the inside contains a locking mechanism designed to accept a liner. Hip replacement_sentence_225

Two types of porous coating used to form a friction fit are sintered beads and a foam metal design to mimic the trabeculae of cancellous bone and initial stability is influenced by under-reaming and insertion force. Hip replacement_sentence_226

Permanent fixation is achieved as bone grows onto or into the porous coating. Hip replacement_sentence_227

Screws can be used to lag the shell to the bone providing even more fixation. Hip replacement_sentence_228

Polyethylene liners are placed into the shell and connected by a rim locking mechanism; ceramic and metal liners are attached with a Morse taper. Hip replacement_sentence_229

Femoral component Hip replacement_section_24

Articular interface Hip replacement_section_25

Conservative management Hip replacement_section_26

The first line approach as an alternative to hip replacement is conservative management which involves a multimodal approach of oral medication, injections, activity modification and physical therapy. Hip replacement_sentence_230

Conservative management can prevent or delay the need for hip replacement. Hip replacement_sentence_231

Preoperative care Hip replacement_section_27

Preoperative education is currently an important part of patient care. Hip replacement_sentence_232

There is some evidence that it may slightly reduce anxiety before hip or knee replacement, with low risk of negative effects. Hip replacement_sentence_233

Hemiarthroplasty Hip replacement_section_28

Hemiarthroplasty is a surgical procedure which replaces one half of the joint with an artificial surface and leaves the other part in its natural (pre-operative) state. Hip replacement_sentence_234

This class of procedure is most commonly performed on the hip after an intracapsular fracture of the neck of the femur (a hip fracture). Hip replacement_sentence_235

The procedure is performed by removing the head of the femur and replacing it with a metal or composite prosthesis. Hip replacement_sentence_236

The most commonly used prosthesis designs are the Austin Moore prosthesis and the Thompson Prosthesis. Hip replacement_sentence_237

More recently a composite of metal and HDPE which forms two interphases (bipolar prosthesis) has also been used. Hip replacement_sentence_238

The monopolar prosthesis has not been shown to have any advantage over bipolar designs. Hip replacement_sentence_239

The procedure is recommended only for elderly and frail patients, due to their lower life expectancy and activity level. Hip replacement_sentence_240

This is because with the passage of time the prosthesis tends to loosen or to erode the acetabulum. Hip replacement_sentence_241

Independently mobile older adults with hip fractures may benefit from a total hip replacement instead of hemiarthroplasty. Hip replacement_sentence_242

Hip replacement_unordered_list_4

  • Hip replacement_item_4_20
  • Hip replacement_item_4_21

Hip resurfacing Hip replacement_section_29

Hip resurfacing is an alternative to hip replacement surgery. Hip replacement_sentence_243

It has been used in Europe for over seventeen years and become a common procedure. Hip replacement_sentence_244

Health-related quality of life measures are markedly improved and patient satisfaction is favorable after hip resurfacing arthroplasty. Hip replacement_sentence_245

The minimally invasive hip resurfacing procedure is a further refinement to hip resurfacing. Hip replacement_sentence_246

Viscosupplementation Hip replacement_section_30

Current alternatives also include viscosupplementation, or the injection of artificial lubricants into the joint. Hip replacement_sentence_247

Use of these medications in the hip is off label. Hip replacement_sentence_248

The cost of treatment is typically not covered by health insurance organizations. Hip replacement_sentence_249

Some believe that the future of osteoarthritis treatment is bioengineering, targeting the growth and/or repair of the damaged, arthritic joint. Hip replacement_sentence_250

Centeno et al. Hip replacement_sentence_251

have reported on the partial regeneration of an arthritic human hip joint using mesenchymal stem cells in one patient. Hip replacement_sentence_252

It is yet to be shown that this result will apply to a larger group of patients and result in significant benefits. Hip replacement_sentence_253

The FDA has stated that this procedure is being practiced without conforming to regulations, but Centeno claims that it is exempt from FDA regulation. Hip replacement_sentence_254

It has not been shown in controlled clinical trials to be effective, and costs over $7,000. Hip replacement_sentence_255

Prevalence and cost Hip replacement_section_31

Total hip replacement incidence varies in developed countries between 30 (Romania) and 290 (Germany) procedures per 100,000 population per year. Hip replacement_sentence_256

Approximately 0.8% of Americans have undergone the procedure. Hip replacement_sentence_257

According to the International Federation of Healthcare Plans, the average cost of a total hip replacement in 2012 was $40,364 in the United States, $11,889 in the United Kingdom, $10,987 in France, $9,574 in Switzerland, and $7,731 in Spain. Hip replacement_sentence_258

In the United States, the average cost of a total hip replacement varies widely by geographic region, ranging from $11,327 (Birmingham, Alabama) to $73,927 (Boston, Massachusetts). Hip replacement_sentence_259

History Hip replacement_section_32

The earliest recorded attempts at hip replacement were carried out in Germany in 1891 by Themistocles Gluck (1853–1942), who used ivory to replace the femoral head (the ball on the femur), attaching it with nickel-plated screws, plaster of Paris, and glue. Hip replacement_sentence_260

On September 28, 1940 at Columbia Hospital in Columbia, South Carolina, American surgeon Dr. Austin T. Moore (1899–1963) performed the first metallic hip replacement surgery. Hip replacement_sentence_261

The original prosthesis he designed was a proximal femoral replacement, with a large fixed head made of the cobalt-chrome alloy Vitallium. Hip replacement_sentence_262

It was about a foot in length and bolted to the resected end of the femoral shaft (hemiarthroplasty). Hip replacement_sentence_263

A later version, the so-called Austin Moore Prosthesis which was introduced in 1952, is still in use today, although rarely. Hip replacement_sentence_264

Like modern hip implants, it is inserted into the medullary canal of the femur, and depends on bone growth through a hole in the stem for long-term attachment. Hip replacement_sentence_265

Other animals Hip replacement_section_33

Main article: Hip replacement (animal) Hip replacement_sentence_266

See also Hip replacement_section_34

Hip replacement_unordered_list_5


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Hip replacement.