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

Important factors which are related to dislocation are: component positioning, preservation of the gluteal muscles and restoration of leg length and femoral offset.

[15] Risk factors of late dislocation (after five years) mainly include:[15] Infection is one of the most common causes for revision of a total hip replacement.

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.

[medical citation needed] The perceived difference in limb length for a patient after surgery is a common cause for lawsuits against the healthcare provider.

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.

[41][additional citation(s) needed] 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.

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

[54][55] 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.

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

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.

The small femoral head (7⁄8 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.

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

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

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.

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

The approaches are posterior (Moore), lateral (Hardinge or Liverpool),[74] antero-lateral (Watson-Jones),[75] anterior (Smith-Petersen)[76] and greater trochanter osteotomy.

[medical citation needed] 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.

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.

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.

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

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

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.

Size, material properties and machining tolerances at the articular interface can be selected based on patient demand to optimise implant function and longevity whilst mitigating associated risks.

[medical citation needed] Total hip replacement incidence varies in developed countries between 30 (Romania) and 290 (Germany) procedures per 100,000 population per year.

[4] 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).

[111][112] In 1938, Philip Wiles of Middlesex General Hospital, UK carried out a total hip replacement using a stainless-steel prosthesis attached by bolts.

[111] Following the lead of Wiles, several UK general hospitals including Norwich, Wrightington, Stanmore, Redhill and Exeter developed metal-based prostheses during the 1950s and 1960s.

In the 1960s, John Charnley[117][111][112] at Wrightington General Hospital combined a metal prosthesis with a PTFE acetabular cup before settling on a metal/polyethylene design.

The choice of alloy, bearing material, attachment and detailed geometry has led to the wide variety of prosthesis designs available today.