Risks and complications in<unk>  are similar to those associated with all joint replacements. They can include infection, dislocation, limb length inequality, loosening, impingement, osteolysis, metal sensitivity, nerve palsy, chronic pain and death. Weight loss surgery before a<unk>  does not appear to change outcomes. Infection Infection is one of the most common causes for revision of a total<unk> , along with loosening and dislocation. The incidence of infection in primary<unk>  is around 1% or less in the United States. Risk factors for infection include obesity, diabetes, smoking, immunosuppressive medications or diseases, and history of infection. Dislocation Dislocated artificial hip Liner wear, particularly when over 2 mm, increases the risk of dislocation. Liner creep, on the other hand, is normal remoulding. Dislocation is the most common complication of<unk>  surgery. The most common causes vary by the duration since the surgery. Hip prosthesis dislocation mostly occurs in the first three months after insertion, mainly because of incomplete scar formation and relaxed soft tissues. It takes eight to twelve weeks for the soft tissues injured or cut during surgery to heal. During this period, the hip ball can come out of the socket. 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. Dislocations occurring between three months and five years after insertion usually occur due to malposition of the components, or dysfunction of nearby muscles. Risk factors of late dislocation (after five years) mainly include: * Female biological sex * Younger age at primary hip arthroplasty * Previous subluxation without complete dislocation * Previous trauma * Substantial weight loss * Recent onset or progression of dementia or a neurological disorder * Malposition of the cup * Wear of the liner, particularly when it causes movement of the head of more than 2 mm within the cup compared to its original position * Prosthesis loosening with migration Surgeons who perform more of the operations each year tend to have fewer patients dislocate. 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. 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. People can decrease the risk further by keeping the leg out of certain positions during the first few months after surgery. Limb length inequality Most adults prior to a<unk>  have a limb length inequality of 0–2 cm which they were born with and which causes no deficits. It is common for people to feel a limb length inequality after total<unk> . Sometimes the leg seems long immediately after surgery when in fact both are equal length. An arthritic hip can develop contractures that make the leg behave as if it is short. 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. This feeling usually subsides by 6 months after surgery as the body adjusts to the new hip joint. The cause of this feeling is variable, and usually related to abductor muscle weakness, pelvic obliquity, and minor lengthening of the hip during surgery ( have demonstrated development of pseudotumors, soft tissue masses containing necrotic tissue, around the hip joint. It appears these masses are more common in women and these patients show a higher level of iron in the blood. The cause is unknown and is probably multifactorial. 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. Metal hypersensitivity is a well-established phenomenon and is common, affecting about 10–15% of the population. Contact with metals can cause immune reactions such as skin hives, eczema, redness and itching. 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. Individual case reports link hypersensitivity immune reactions with adverse performance of metallic clinical cardiovascular, orthopedic and plastic surgical and dental implants. Metal toxicity Most<unk> s consist of cobalt and chromium alloys, or titanium. Stainless steel is no longer used. All implants release their constituent ions into the blood. Typically these are excreted in the urine, but in certain individuals the ions can accumulate in the body. In implants which involve metal-on-metal contact, microscopic fragments of cobalt and chromium can be absorbed into the person's bloodstream. There are reports of cobalt toxicity with<unk> , particularly metal-on-metal<unk> s, which are no longer in use. Use of metal on metal<unk> s from the 1970's were discontinued in the 1980s, and 1990s, particularly after the discovery of aseptic lymphocyte-dominant vasculitis-associated lesions (ALVAL). The FDA's 510k approval process, allowed companies to get new and 'improved' metal on metal hips approved without much clinical testing. Again, some with these hips are experiencing the same reactions to the metal debris and some devices have been recalled, like the DePuy ASR. Nerve palsy Post operative sciatic nerve palsy is another possible complication. The incidence of this complication is low. Femoral nerve palsy is another but much more rare complication. Both of these will typically resolve over time, but the healing process is slow. Patients with pre-existing nerve injury are at greater risk of experiencing this complication and are also slower to recover. Chronic pain A few patients who have had a<unk>  suffer chronic pain after the surgery. Groin pain can develop if the muscle that raises the hip (iliopsoas) rubs against the edge of the acetabular cup. 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. Also some patients can experience pain in cold or damp weather. 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). Death The rate of perioperative mortality for elective<unk> s is significantly less than 1%. Metal-on-metal hip implant failure 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. 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. Design deficits of some prothesis models, especially with heat-treated alloys and a lack of special surgical experience accounting for most of the failures. 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. 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). In the United Kingdom the Medicines and Healthcare products Regulatory Agency commenced an annual monitoring regime for metal-on-metal<unk>  patients from May 2010. 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. 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. It is not clear to what extent this phenomenon negatively affects orthopedic patients. However, for patients presenting with signs of an allergic reactions, evaluation for sensitivity should be conducted. Removal of the device that is not needed should be considered, since removal may alleviate the symptoms. Patients who have allergic reactions to cheap jewelry are more likely to have reactions to orthopedic implants. 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. 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. The analysis of 402,051<unk> s showed that
Hip replacement
Ankle replacement
Finger joint replacement
Hip resurfacing
Knee replacement
Shoulder replacement
Joint replacement
Femoral head ostectomy