The concept of an artificial joint is simply an artificial organ designed to restore joint motion in the human body. And it is an artificial organ that is now widely and successfully used in clinical practice.
Most artificial joints have been used successfully worldwide. The hallmark of this is that the 20-year survival rate of a well-designed prosthesis has exceeded 90% after placement in the human body, and some have even survived more than 30 years in the human body.
History and Development
Initially, people wanted to regain the function of their joints after they had been injured and straightened. Many very useful attempts were made to do so. For example, arthrodesis was devised, which may have restored some of the range of motion of the joint, but the strength and stability of the joint motion was poor, so the function of the joint obtained was not very satisfactory.
Various attempts were made later.
In 1880, Ollier used the soft tissue around the joint to make a “joint surface”;
In 1908, Lexer used fascia to make “articular surfaces”;
In 1919, Beer made a “joint surface” from the bladder of a pig;
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In 1891, Gluck used ivory to make the form of a human hip joint to be inserted into the human body. Although unsuccessful, his attempt was undoubtedly a “revolution” in the history of artificial joints;
It was not until around the Second World War that people had more and better options in the selection of materials for prosthesis due to the continuous progress of materials.
In 1937, Smith-Petersen chose cobalt-chromium-molybdenum alloy to make the “joint surface”, which was successfully used in clinical practice; in 1939, Wiles designed an all-metal total hip joint, which was also successfully used in clinical practice. They are known as the pioneers of modern artificial joints.
In the 1960s, Charnley in England made revolutionary advances in artificial total hip replacements. Charnley is also known as the “father of artificial joints”.
1, the use of metal and ultra-high polymer polyethylene, and the use of a smaller diameter of the femoral head (22.5 mm diameter), so that the artificial joint wear greatly reduced. So-called low wear principle.
2.Adopted bone cement (polymethyl methacrylate) to fix the artificial hip joint, which makes the success rate of artificial total hip joint greatly improved.
3.The adoption of laminar flow purification operating room is advocated, which makes the infection rate greatly reduced.
With the deepening understanding of human biomechanics and the rapid development of material science, the design of artificial joint is more and more in line with the physiological and anatomical characteristics of human body; the wear and tear of prosthesis is getting lower and lower; and the life span of prosthesis is getting longer and longer. For example: anatomical hip prosthesis; knee prosthesis with rotation function, etc.
Materials of artificial joints
The materials currently used for artificial joints are: cobalt-chromium-molybdenum, titanium, ultra-high polymer polyethylene and ceramics. Cobalt-chromium-molybdenum alloy is stronger and is mostly used for cemented prostheses and femoral head prostheses, and allergies are rare. Titanium alloy is the closest metal to human cortical bone in terms of elastic modulus and has good histocompatibility. It is mostly used for non-cemented prostheses. UHMWPE has good wear resistance and histocompatibility, and has good cushioning. Wear interface in combination with cobalt-chromium-molybdenum alloy or ceramics. Ceramics have a very good smooth surface and are hard and brittle at the same time. They are mostly used for femoral head prostheses.
Surface of the prosthesis
In order to obtain a better fixation of the prosthesis with the surrounding bone cement or bone, special treatments are usually applied to the surface of the prosthesis. For example: rough surface, microporous surface, macroporous surface, coral surface, titanium wire surface, HA coating
(hydroxyapatite) bone cement pre-coating, etc. When two materials with different modulus of elasticity are fixed together under stress, the contact interface will produce certain micro-movement, and over-emphasis on the fixation of the interface will produce stress concentration instead.
After long-term clinical observation, the surface of cemented prosthesis is rough (1.5um), which can form a good microscopic strand lock with the bone cement and avoid the cutting effect on the bone cement caused by the micro-movement at the interface. The surface of the non-cemented prosthesis should be microporous, with pores between 50 and 200 um, which is most conducive to bone ingrowth and vascular ingrowth. HA coating (hydroxyapatite) has been shown in animal experiments and clinical applications to allow rapid osseointegration of the prosthesis with bone.
The purpose of artificial joint replacement is to.
1.To relieve pain;
2.Improve function;
3. To correct deformities.
Although artificial joint surgery is a very mature technique and has been widely used worldwide, it is not the only option for clinical treatment. At the same time, the surgery itself still carries certain risks and there are many complications. One of the important factors is the longevity of the prosthesis. In addition, the surgeon’s understanding of the artificial joint and surgical technique as well as the general level of the hospital, especially the conditions of the operating room, are important factors that influence the success of the surgery. The patient’s understanding of the need to improve the quality of life and the patient’s cooperation with the surgeon are also important factors in the choice of surgery.
Principles of Artificial Joint Replacement.
1. The selected prosthesis should conform to the local biomechanical characteristics;
2. Minimal osteotomy;
3, as much as possible to preserve the surrounding blood flow;
4.Surgical operation should reflect the design concept of the prosthesis;
5.The installation of the prosthesis should consider the immediate stability and long-term stability;
6.Convenience of possible revision problems;
Contraindications
1, accompanied by other diseases, affecting the process of surgery or recovery; for example: cardiovascular disease, diabetes, blood disease, etc. ;
2.Local or distal foci of infection or potential infection when?
3.It is impossible to reconstruct the function, the limb is not functional due to skeletal, vascular, nerve or muscle reasons, and the bone loses its effective fixation function to the prosthesis;
4.The patient does not cooperate, or has no confidence in the recovery;
5, the surgeon’s reasons: not fully aware of the surgery and prosthesis;
6, the hospital or operating room reasons, such as: when the patient has an accident can not be dealt with in a timely and effective manner, the operating room aseptic conditions are not qualified;
Early complications
I. Nerve and vascular injuries are abundant around each joint, and there are many important nerves and blood vessels. The surgical procedure including access, prosthesis installation and the change of position during surgery may cause damage to the surrounding nerves and blood vessels. Familiarity with local anatomy before surgery, gentle and accurate prosthesis placement, and gentle and reasonable position placement are essential to minimize complications.
The sciatic and common peroneal nerves are more likely to be injured during hip surgery, while injuries to the femoral and foramen ovale nerves are less common. Injuries are often caused by inappropriate use of the pulling hook when exposing the acetabulum, or by soft drills or medullary stems or spillage of bone cement through the medullary cavity during proximal femoral marrow opening. Excessive lengthening of the limb after surgery is also a common cause of vascular nerve injury. In knee surgery it is mainly the posterior slapping nerve and slapping artery of the joint and the lateral common peroneal nerve. The mechanism of injury is largely the same as above.
Second, hematoma formation after surgery can greatly increase the chance of infection. Careful and careful hemostasis during surgery and routine placement and patency of negative pressure drainage tubes after surgery are effective measures to prevent hematoma. Once a hematoma occurs, it should be treated promptly.
Third, bleeding surgery should be closely hemostatic for larger bleeding points. Particular attention should be paid to patients with bleeding tendency, and hematologists should be consulted if necessary. Patients with combined hematologic disease, long-term chronic liver disease, anticoagulant use and family history should be well prepared for surgery.
Pain Pain is the most common complication after surgery. It usually occurs on the first and second day after surgery.
The first and second day after surgery, prolonged pain should be promptly investigated for other causes. The most likely cause is infected loosening.
The conventional treatment is the use of analgesics or placement of analgesic pumps, etc.
Infection after surgery is the most serious complication of prosthetic joint replacement, and its consequences can be catastrophic. It often leads to complete failure of the surgery, or to disability or even death of the patient.
When the patient is combined with other diseases, the chance of infection may be increased. The most common are diabetes mellitus and others.
Long-term use of hormones, immunosuppressants, secondary surgery, and local scarring can increase the chance of infection.
Therefore, when there is an infected lesion in the surgical field or a distant infected lesion in the body it is a contraindication to artificial joint replacement surgery.
Diagnosis and Treatment of Infection I. Diagnosis
Infection is easily diagnosed when typical symptoms such as local redness, swelling, heat, and pain are present. However, when a low toxicity infection or chronic infection occurs, the clinical symptoms are often atypical, and the diagnosis should be combined with other laboratory tests, bacterial cultures, x-rays, and other ancillary tests to assist in the diagnosis.
Differentiation of infected prosthesis loosening and aseptic prosthesis loosening has very important clinical significance for guiding treatment and prognosis.
1, clinical manifestations: pain is one of the important symptoms of infection. Most of the pain occurs with rest pain and activity. And the pain shown by the aseptic loosening of the prosthesis mainly occurs during activity, and can be significantly relieved when resting. Infection can be manifested as low fever.
2, laboratory tests: white blood cell count, blood sedimentation, CRP (C-reactive protein), puncture fluid culture, etc.. Especially the blood sedimentation combined with CRP especially dynamic value changes have greater significance for the diagnosis of hypotoxic infection.
3, X-ray examination: the early X-ray performance of infection is not obvious. Late stage has the manifestation of periostitis and osteomyelitis, but sometimes it is very difficult to distinguish from aseptic loosening.
II. Treatment: Superficial infection is relatively easy to deal with, while the management of deep infection is
The treatment of deep infections is very difficult. Different treatment methods can be chosen depending on the infection.
1. Local irrigation: for acute infections, mostly within 3 weeks after surgery. Infections older than 3 weeks or low-virulence infections are often ineffective with this conservative treatment.
2.Stage I revision: Applicable after the acute infection is controlled, or low toxicity infection, stage I removal of the infected prosthesis along with the placement of a new prosthesis. At the same time, antibiotic bone cement is selected according to the pathogenic condition of the infection.
3, Phase II revision: when the infection is difficult to control, you can first remove the infected prosthesis with therapeutic prosthesis for local treatment and combined with systemic comprehensive treatment, when the infection is controlled and then a new prosthesis is placed.
4.Arthroplasty or amputation: a method used when the patient’s general condition and local conditions of the affected limb do not allow for reinsertion of the prosthesis.
Fracture fracture can occur in the operation, but also can be seen in the postoperative period. The former is mostly related to surgical
The former is mostly related to the operation, such as: intraoperative position changes, the use of the medullary file, reset, etc.; the latter is mostly related to trauma or prosthesis loosening and is a late complication. There are many treatment methods, such as: implantation of internal fixation, bone graft, external fixation, etc. What is more important is to pay attention to the surgical operation method and adopt the correct means of rehabilitation and lifestyle to avoid fracture.
VII. The causes of thrombosis thrombosis are.
1, prolonged bed rest before and after the surgery, the muscle tension decreases causing the venous blood flow to be sluggish;
2, direct or indirect damage to the veins during surgery;
3.Large amount of bleeding during surgery and relatively insufficient water intake cause the blood to be in a hypercoagulable state.
The main manifestation is swelling and muscle pressure pain of the affected limb, which can be accompanied by low fever. In severe cases, cyanosis and edema of the limb may occur. Prevention and treatment of thrombosis. Encourage the patient to do isotonic contraction training of the whole body muscles early. Low molecular dextran, heparin, aspirin and other drugs can be used for prevention. Remove the thrombus surgically if necessary.
VIII. Dislocation: Postoperative prosthesis dislocation is a common complication of total hip arthroplasty in particular, and the common causes are.
1, the same joint has a history of previous surgery;
2, surgical access and dislocation;
3, improper position of the prosthesis;
4.Impact between prostheses;
5, poor periarticular soft tissue tension;
6.Post-operative joint placement (or rehabilitation) is not appropriate;
The methods of preventing and treating postoperative joint dislocation are
1, correct prevention of the position of the prosthesis;
2, try to ensure the tension of the soft tissues around the joint;
3.Make full use of the trial mold to check the mobility of the joint before the intraoperative installation of the prosthesis;
4.Avoid excessive internal flexion of the hip after surgery;
5.If the joint is unstable after surgery, the external fixation time should be extended appropriately;
6.Closed repositioning can be done under anesthesia, combined with external fixation;
7.Surgical incision and reset.
Late complications
I. Prosthesis loosening prosthesis loosening is the most common complication after artificial joint replacement, is the main reason for revision surgery, it directly affects the service life of the prosthesis. How to reduce the occurrence of prosthetic loosening has been the direction of efforts of doctors. Briefly, the main causes of prosthesis loosening are.
1.The effect of adverse stress;
2, osteolysis caused by fragmentation disease.
Second, heterotopic ossification heterotopic ossification refers to the appearance of bone deposits in the soft tissue around the joint after surgery. Its pathogenesis is not clear. Most of them are related to extensive damage to soft tissues or are associated with physical fitness. Commonly used prophylactic medications include nonsteroidal hormones.
Features of the collared prosthesis
1, and the proximal femur osteotomy surface fully anastomosis, so that the distribution and direction of stress transmission more reasonable, that is, to restore the normal physiological load transmission of the femur;
2, at the same time to avoid the sinking of the prosthetic stem also to ensure the correct position of the prosthetic stem;
3. Completely cover the proximal femoral medullary cavity to prevent the entry of joint wear “debris”.
Bone cement type? Non-cemented?
The choice between cemented and uncemented prostheses in hip replacement is a question that is often faced. This is true for both initial replacement and revision surgery. First we need to understand the characteristics of both types of prostheses.
Features of cemented prosthesis.
1, clinical application for a long time, the clinical effect is exact, there are a large number of successful cases.
2.The operation technology has been very mature.
3.The requirements for surgical operation are relatively low.
4.The patient’s recovery time is relatively short.
Features of non-cemented prosthesis.
1.The use of biological fixation, avoiding the side effects caused by the use of bone cement.
2.More options are available for the revision surgery that may be faced.
3.The operation requirements for surgeons are relatively high.
4.Common complications include thigh pain.
However, when faced with a difficult choice, choosing a non-cemented prosthesis may be the wrong choice. The choice of cemented or non-cemented prosthesis should never be based on the patient’s age as the only criterion. The patient’s bone condition; bone growth potential; quality of life requirements; cooperation with rehabilitation, etc., the surgeon’s understanding and skill in handling different types of prostheses are all important factors in the selection of a prosthesis.
In revision surgery, the selection of the type of prosthesis should also take into account the above factors. However, revision surgery has its own characteristics. For example, the condition of the bone defect, whether it is combined with a fracture, whether it is infected or has potential for infection, etc.
The problems faced when revising with cemented prostheses are.
1. Due to the loss of the so-called microscopic strangulation, the bond strength between the bone cement and the hardened bone interface is greatly reduced, reaching only 20% of the initial replacement.
2. The use of bone cement exclusively to fill the large number of bone defects in revision surgery can seriously affect the strength of the bone cement itself.
3.When the integrity of the bone is not present, the bone cement will not be able to fill.
4.When a fracture occurs during surgery, the use of bone cement may spill into the fracture gap and cause the fracture to not heal.
5.When facing multiple revisions, the removal of bone cement is bound to cause more extensive bone loss.
However, cemented prostheses also have advantages for revision surgery, such as good immediate post-operative stability, the use of antibiotic cement in cases of co-infection or potential infection, and the relative simplicity of the procedure. These disadvantages can be avoided when combined with compression implants or structural implants. Non-cemented prostheses can be used for revision surgery to avoid these disadvantages.
It can also show its unique advantages in the face of combined fractures. Its disadvantages are the relatively high operative requirements, the increased risk of surgery due to the presence of potential infection, and the poor immediate postoperative stability.