Hip Replacement (Total Hip Arthroplasty)

Total hip replacement (synonym: total endoprosthesis (TEP) of the hip joint), also known as “hip TEP” (total hip replacement; total hip arthroplasty), is a surgical procedure to correct severe damage to the hip joint that, as a result of various diseases, limits the mobility and quality of life of the affected patient. Hip joint prostheses are divided into femoral head prostheses, stem prostheses and acetabular prostheses. If both the femoral head and the acetabulum are replaced, it is a total endoprosthesis (TEP); if only the head is replaced, it is called a hemiendoprosthesis (HEP). Between the stem and the socket of the hip joint is the bearing couple, which consists of two parts. The ball head, made of metal or ceramic, is attached to the stem. This head can rotate in a spherical cup insert so that the difference in freedom of movement between the implant and the functional hip joint should not be significant. The cup insert described can be made of metal, ceramic, or plastic. Total hip arthroplasty represents an important therapeutic option in the treatment of, for example, coxarthrosis (hip joint wear) or a rheumatic disease such as rheumatoid arthritis. In addition to these extremely common causes, less common bacterial infections also play an important role in the development of inflammatory damage to the hip joint. Examples include chlamydia, Borrelia or Campylobacter pylori. Inflammations of other causes, such as psoriasis, but also existing tumors and necrosis of the femoral head are further indications. Injuries to the joint, fractures (broken bones) and malpositions can also make a total hip joint endoprosthesis necessary. Implantation of a total hip joint is one of the most common orthopedic procedures in Germany. Hip-preserving therapy variants for coxarthrosis, for example, have been replaced by total hip arthroplasty almost without exception within the last 20 years.

Indications (areas of application)

  • Symptomatic coxarthrosis (osteoarthritis of the hip joint; wear and tear of the hip joint).
  • Inflammatory joint damage (secondary coxarthrosis) due to.
    • Rheumatoid-related disease such as rheumatoid arthritis (also chronic polyarthritis) – is the most common inflammatory disease of the joints.
    • Other autoimmune phenomena such as a systemic lupus erythematosus (SLE; systemic autoimmune disease from the group of collagenoses).
  • Femoral head necrosis (FKN; femoral head necrosis), for example, in the case of deficient blood supply to the femur after an accident.
  • Subcapital femoral fracture (femoral fracture below the femoral head).
  • Comminuted fracture of the head or acetabulum
  • Malalignment of the joint
  • Hip dysplasia (malformation of the hip) with secondary coxarthrosis.

Contraindications

  • Poor general health
  • Lack of tolerance of anesthesia or anesthesia.

Before the operation

  • According to various scientific studies, in addition to the preparation and performance of the surgical procedure, the success of the operation depends on other factors besides the patient’s length of stay. The better the patient’s general condition, the lower the risk of complications. However, muscular resilience is also an important component in the function of the implanted joint. Targeted muscle building training can minimize the risk that the joint function does not improve relevantly.
  • In addition, training can simultaneously reduce excess body fat, which leads to a reduction in the load on the prosthesis. Thus, if the patient is overweight or manifest obesity, he should specifically lose weight before surgery. However, this is complicated by the fact that those affected often have difficulty losing weight due to mobility restrictions.
  • In addition to the reduction of weight, it is also essential that the attending specialist is informed both about the medication and chronic diseases such as diabetes mellitus or cardiovascular disease. The same applies to existing allergies or acute infections.
  • Before the planned insertion of a hip arthroplasty, the treating physician should be aware of whether osteoporosis is present in elderly patients. If in doubt, osteodensitometry (bone density measurement) should be performed. The overall risk in patients with osteoporosis for intraoperative and postoperative complications, especially periprosthetic fractures (bone fractures), is up to 20%. If necessary, osteoporosis patients with osteoarthritis should receive systemic therapy with bisphosphonates.
  • From an infectiological point of view, it is considered particularly important that the patient’s bedtime before surgery is as short as possible, so as to minimize the risk of infection.
  • In many cases, medications that inhibit blood clotting, such as acetylsalicylic acid (ASA), must be discontinued before surgery.
  • Before a hip prosthesis can be performed, various preparatory measures are required, such as optimally adapting the prosthesis to be implanted to the physiological and anatomical conditions of the patient. Based on this, a so-called planning sketch is primarily created. This is prepared using a computer-assisted system to produce a digital X-ray image. Following this, it is necessary that the prosthesis components are optimally adapted to the patient. Both the stem thickness and cup size as well as the head size and optimal position of the prosthesis must be determined and prescribe the selection of components for the following surgical procedure.
  • In addition to the individual components of the prosthesis, it is essential to determine the leg length. Furthermore, spinal statics should be performed and evaluated on a patient-specific basis. With the help of the measurement of the spine, it becomes possible to correct malpositions of the lower limb(s), if necessary.

The surgical procedure

The operation can be performed either under general anesthesia or with spinal anesthesia (form of regional anesthesia close to the spinal cord). However, spinal anesthesia cannot be performed in every patient because anatomic conditions do not always allow it. At the beginning of the procedure, the atrophic (worn) joint surfaces and the femoral head of the thigh bone (head of the femur) are removed. The remainder of the femur bone is now used to hold the implant in place. After removal, the implantation and anchoring of the two joint components now takes place. Depending on the age, weight and general condition of the respective patient, various endoprostheses can be inserted. A distinction is made between cemented and cementless prostheses:

Cemented endoprostheses are usually used in older patients. The anchoring in the femur bone of the prosthesis is done with the help of bone cement. The bone cement is a two-component adhesive used to fix the steel prosthesis made of chromium-cobalt-molybdenum. The advantage of this technique is the short rehabilitation time, which is made possible by the immediate load-bearing capacity of the new joint and thus early mobilization. The short rehabilitation phase is an important argument in favor of a cemented endoprosthesis, especially for older persons. However, the increased risk of prosthesis loosening must be regarded as a disadvantage. Another disadvantage is the low aging resistance of the two-component adhesive. This means that it cracks over time, reducing the strength of the prosthesis. For these reasons, cemented prostheses are used today almost exclusively in osteoporotic bone. This is done with the aid of the idea that the cement penetrates far between the remaining bone bellows and thus enables a safe transmission of force. Other disadvantages are the possible toxicity (toxicity) and allergy to the bone cement, as well as the need to remove the cement in case of “replacement surgery”. Even with a cemented arthroplasty, the socket can be implanted without cement. In this case, it is referred to as a hybrid system. A completely cementless surgical technique is also possible. Cementless endoprostheses are usually used in younger patients (< 60 years). Anchorage in the femur bone of the prosthesis is achieved by clamping and a sponge-like metal surface (“pressfit”) into which the bone grows. As an advantage of this technique, durability is the first priority!The only disadvantage of this technique is that the relief or partial relief may be required for a few weeks. In addition to the invasive surgical technique, there is also the option of minimally invasive hip arthroplasty. Today, modern minimally invasive surgical techniques allow a tissue-sparing type of implantation and, if necessary, a faster recovery from the operation. However, this only applies to the first few days after the operation. In the further course, there is no difference between the individual techniques in the mobility or load-bearing capacity of the hip joint. There are specific indications for the minimally invasive technique, so this procedure should not be used for every hip joint condition.

After surgery

  • After surgery, pain-relieving medications such as diclofenac (a drug from the group of non-opioid analgesics) are usually applied in combination with a proton pump inhibitor (“acid blocker”) to protect the gastric mucosa, depending on the patient’s pain level.
  • Start of thromboprophylaxis: for physical and drug prophylaxis of venous thromboembolism (VTE), see below Pulmonary Embolism/Prevention/Prophylaxis of Venous Thromboembolism (VTE).
  • After the operation, the hip must be loaded less for a few days. In contrast, the other joints should be moved a lot. Based on this, physiotherapy is to be considered useful. Even later, the patient should not carry large weights and also do not let their own body weight too large.
  • The joint should not be moved excessively far. Sporting activity should be exercised only in consultation with a doctor. The risk of complications from sports varies depending on the type of sport and the level of performance.
  • Two weeks after a hip TEP, the patient can drive again, because then already normal braking reaction times are again detectable.

Possible complications during surgery

Possible complications after surgery

  • Risk of thrombosis (very high) – obese and women are particularly affected.
  • Risk of embolism (occlusion of a blood vessel) when inserting the bone cement and hammering the prosthesis stem into the femur bone (thigh bone)
  • Myocardial infarction (heart attack) (up to 6 weeks after implantation of a hip replacement).
  • Pneumonia (pneumonia)
  • Pulmonary edema
  • Renal insufficiency (kidney weakness)
  • Apoplexy (stroke)
  • Wound healing disorders; active smokers are more likely to have wound complications; deep wound infections occurred twice as often in smokers.
  • Abscesses
  • Periarticular ossification (ossification of the joint due to new bone formation in the area of the artificial joint space).
  • Pain due to periarticular ossification.
  • Abrasion between the head and cup material of the prosthesis.
  • Aseptic (without involvement of pathogens) prosthesis loosening – prosthesis change required.
  • Difference in leg length
  • Implant fracture
  • Infection of the prosthesis – late infection requires replacement of the prosthesis
  • Dislocation tendency of the hip joint
  • Periarticular (around a joint) calcifications – up to 50% of patients are affected; function is usually not impaired
  • Periprosthetic fracture (the bone in which the prosthesis is anchored is broken) – especially in patients with osteoporosis (bone loss)
  • Periprosthetic infection (infection of the peri-implant tissue (“around the implant”) of an artificial joint placed in the body) – results in a mean annual replacement rate of 0.09 per 1,000 person-years (per thousand); risk factors were:
    • Men: incidence rate 1.18 per thousand; obesity: 1.82 per thousand; patient age <60 years: 1.07 per thousand;
    • Concomitant diseases: chronic lung disease (incidence rate, 1.15), diabetes mellitus (incidence rate, 1.37), dementia (incidence rate, 1.49), chronic heart failure (incidence rate, 1.42), and liver disease (incidence rate, 2.53)
    • Surgical aspects: Fractures of the femur (incidence rate, 1.52), avascular necrosis (incidence rate, 1.36), early hip infections (incidence rate, 7.20)
  • Loosening of the prosthesis
  • Dislocation of components of the prosthesis
  • Myocardial infarction (heart attack) – in the first postoperative month after surgery, the risk of infarction was higher by a factor of 4.33; thereafter, the differences were not significant

Further notes

  • Patients with total hip arthroplasty (hip TEP) replacement and a body mass index ≥ 30 have an increased rate of complications-especially an increased risk of infection (2.71-fold); dislocations were 72% more common, reoperations 61% more common, revisions 44% more common, and readmissions 37% more common. The rate of complications was even higher in the group with a BMI of 40 or more.
  • A study of young, active patients showed, after total knee arthroplasty (TEP) in cementless procedures, that the proximal femur (thigh) increased in bone mineral density in Gruen zones 1, 2, and 7, i.e., laterally (“laterally”) at the greater trochanter (ie. the large rolling mound; this is located in the transition area between the femoral body (corpus femoris) and the femoral neck (collum femoris)) and in the underlying area, and medially (“located in the middle”) in the area of the lesser trochanter (small rolling mound; this is located at the posterior lower end of the femoral neck), decreased.
  • Analysis of the service life of 2,000 hip TEPs (Mayo Clinic in Rochester; period: 1969-1971; mean age, 63 years; procedure: cemented Charnley-low-friction prostheses with metal-polyethylene bearing couple) showed the following: 13% of patients required revision surgery (men <50: 46%; women >70: 4%); likelihood of revision decreased with patient age at first TEP implantation; lifetime risk related to age:
    • <50 years: 35%
    • 50-59 years: 20%
    • 60-69 years: 9%
    • > 70: 5 %
  • For postoperative care of geriatric patients with hip fracture, intensive mobilization is required immediately after hip surgery, i.e., full weight-bearing without restriction. In the geriatric group, no patient managed a 40-m walk distance under partial weight-bearing. Limitations small collective with fractures of different localizations.
  • Sports:
    • Yoga exercises sometimes expose the hip to extreme stress.
    • Breaststroke and whole body vibration training lead to high stress on the joint; furthermore, lead to high stress:
      • Standing on one leg and simultaneous movements of the extended other leg and
      • Standing on two legs and simultaneous muscle contraction.
  • 6 out of 10 knee replacements today have a durability of ≥ 25 years.