Cementless Total Hip Replacement

Bone cement fixation of artificial hip replacement achieved significant results, but there is still a high rate of loosening, especially for young and active patients. In order to solve this problem, artificial joints with porous surfaces have been designed to replace the bone cement fixation with a biological fixation method in which the bone grows into the porous surface. Several requirements for biological fixation: 1 minimally excision of bone during surgery, minimally interfere with the stress conduction of bone structure; 2 implant prosthesis to maximize contact with bone tissue to reduce voids. Animal experiments have shown that bone tissue beyond 1 to 2 mm can not grow into the porous surface; 3 the prosthesis must be three-dimensionally fixed after implantation, and the relative movement between the prosthesis and the bone tissue is minimized. Within 3 weeks after initial fixation, the relative motion does not exceed 30 m, so as to avoid fracture of the trabecular bone in the long hole; 4 physical or chemical damage must be avoided, such as preventing violent impact on the artificial femoral stem; 5 2 to 3 postoperatively There is a limited load at the beginning of the month to stimulate bone growth on the weight bearing surface. However, excessive weight bearing will prevent the bone tissue from growing into the pores of the surface of the prosthesis, and finally the interface forms a fibrous membrane. Intraosseous growth is also affected by the quality of the patient's bone, the condition of the lesion, the age, and the drugs (prednisone, indomethacin, methotrexate, cisplatin, etc.). After the intraosseous growth is fixed, remodeling of the bone or surrounding bone that has grown into the pores will occur. If the diameter of the prosthesis stem is too thick (>13.5mm), the difference from the surrounding elastic modulus is too large, or the full length of the prosthesis stem has a porous surface. The femoral shaft is connected to the porous surface, and most of the stress will be transmitted through the prosthesis. On the femur. All of the above reasons can cause stress shielding to cause poor bone growth in the proximal femur and osteoporosis or femoral distance absorption. At present, the shank transverse diameter and anteroposterior diameter of the cementless artificial hip joint are relatively thick, with or without a cervical collar. The porous surface is designed in the upper third of the prosthesis stem to facilitate bone growth. The distal end of the shank is smooth and embedded in the femoral shaft for initial fixation. The intraosseous growth zone is mainly located at the junction of the porous surface and the smooth surface, and there is a metal reinforcement cup on the back of the plastic acetabular cup. The back of the metal cup is a porous surface that is screwed to the acetabular bone. There are also large hip threads on the back of the hip metal cup that can be screwed into the acetabulum. The commonly used cementless porous surface artificial hip joints in foreign countries include AML (anatomic medullary locking), PCA (porous coated anatomic), H-GP (Harris-Galante Prosthesis), Osteonics, APR (anatomic porous replacement), etc. The pearl face artificial total hip joint macroporous type and porous surface joints. The design of the artificial total hip joint of the pearl surface: in order to ensure that the bone tissue grows into the pores of the joint surface and achieve the biological fixation, it must be done: 1 The surface of the prosthesis is closely matched with the bone tissue. Harris believes that there is a gap of more than 1 mm between the medullary and the prosthesis, and it cannot naturally grow over the bone even under strong fixation conditions. 2 strong initial fixation. In order to meet the maximum area of the bone and the prosthesis, the minimum amount of bone resection and early strong internal fixation, a hemispherical pearl acetabular cup can be used. The back of the metal-reinforced acetabular cup is a pearl face that can be fixed in the acetabulum through a metal cup hole with a screw to achieve a firm initial fixation. The plastic acetabulum is placed in a metal cup. The length of the artificial femoral prosthesis is 13cm, and the body part of the prosthesis is rectangular in shape, which prevents the rotation of the stem in the medullary cavity. The distal part of the shank has a cylindrical shape with diameters of 8 mm, 10 mm, and 12 mm, respectively, to accommodate different diameters of the medullary cavity, and plays a tight fit. The proximal part of the shank is coated with a pearl-like spherical particle of 1 mm in diameter, and a cervical support platform is provided to transmit stress to the upper end of the femur, which promotes bone growth. The diameter of the femoral head ball is 32mm, which is replaceable. It is divided into three types: long, medium and short. The length of the head and neck can be adjusted. After biomechanical determination by animal experiments, the bone-prosthesis combined strength of the pearl prosthesis can exceed the fixation strength of the bone cement one month after the implantation of the pearl prosthesis. Femoral prosthesis selection: Preoperative measurements help to choose the right prosthesis. Preoperatively, a transparent template of the pearl prosthesis can be used in combination with X-ray film measurement. The method is as follows: the X-ray film of the hip is placed on the viewing lamp, and the transparent template of the femoral prosthesis with different models is printed. On the X-ray of the hip joint. Considering that the hip X-ray film has a 15% to 20% magnification, the prosthesis on the mold has a 15% magnification. The neck support platform of the template prosthesis is placed on the plane of the femoral neck osteotomy, and the medial edge of the prosthesis stem is parallel to the femoral cortex on the X-ray film. When selected, the template prosthesis handle is filled with the model of the medullary cavity on the X-ray film, which is the model to be selected. It is not accurate to use the template to select the acetabular cup. It is best to use an appropriate size acetabular cup during surgery. Treatment of diseases: femoral head necrosis of the femoral head Indication Non-cemented total hip arthroplasty is suitable for: Total hip arthroplasty is mainly to relieve hip pain, followed by improved hip function. Hip joint pain caused by hip disease over 60 years old, can not be used for other operations and only for head and neck resection is the main indication for total hip arthroplasty. Total hip arthroplasty may also be considered for young patients who require pain relief or improved functional activity. The specific indications are: 1. Old femoral neck fractures, femoral head and acetabulum have been destroyed and painful and affect the function. 2. Avascular necrosis of the femoral head, including avascular necrosis of the femoral head caused by traumatic, idiopathic, prednisone or alcoholism. For the first and second stages of avascular necrosis of the femoral head, the femoral head and acetabulum are intact, the joint space is normal or slightly narrow, and the pain can not be relieved by non-surgical treatment. Surgery such as rotating osteotomy to improve symptoms. For cases of third- and fourth-stage femoral head necrosis, the femoral head has collapsed and the acetabulum has been destroyed, and total hip arthroplasty is feasible. The effect of double cup joint replacement is not good. 3. In patients with severe pain in osteoarthritis, the effect of artificial femoral head replacement is not good. For patients aged 50 to 60 years with acetabular involvement, severe pain and dysfunction, total hip arthroplasty is feasible. 4. Rheumatoid arthritis and ankylosing spondylitis are mostly younger patients. Due to intolerable hip pain or severely restricted activity due to rigidity, patients' learning, work and marital problems are not easy to solve; hip deformity It often causes concurrent deformities of other joints; soft tissue contracture and fibrosis of hip joint capsules and muscles make the joints have a small range of motion and cannot perform strenuous activities. Although these patients are young, but their physiological age is aging, coupled with the influence of social factors, the age limit should be relaxed, especially those with bilateral hip and spine involvement. Total hip replacement should be performed early. Even a limited joint activity after surgery can make the patient feel more convenient. 5. Hip ankylosis Hip pain is the most important surgical indication; the unilateral hip joint is physiologically rigid and painless, not a surgical indication. A hip joint that is not completely bony and has pain and deformity. The hip joint with complete bony rigidity causes pain and instability due to the deformity of the hip joint caused by degenerative osteoarthritis of the adjacent joint. Hip deformity can be divided into: 1 abduction, flexion, external rotation deformity, moderate abduction deformity easily lead to degenerative changes of the lumbosacral joint, severe abduction deformity can cause contralateral hip joint degeneration; 2 adduction, flexion, Internal rotation deformity, easy to cause instability and degeneration of the ipsilateral knee joint. Total hip arthroplasty should be performed for these patients. 6. Chronic hip dislocation mainly includes congenital dislocation of the hip, acetabular dysplasia, and old dislocation due to traumatic infection. Total hip arthroplasty has special problems due to hip dislocation during early childhood or childhood, resulting in corresponding pathological changes in the acetabulum, femur and surrounding soft tissue. Hip subluxation, hip arthritis, pain or loss of function, patients over the age of 45 may consider replacement surgery. Due to the insufficient depth of the acetabulum, the upper edge of the acetabulum has a large slope, which affects the stability of the acetabular cup. The acetabular or occlusion should be deepened during the operation. High hip dislocation, because the acetabulum is small and shallow, the femoral head is small and deformed, the position is moved up, the femoral bone marrow is thinned, the surrounding soft tissue is contracted, and the replacement surgery is difficult. High hip dislocation and severe secondary osteoarthritis, severe hip pain, may be considered for the use of special artificial joints for total hip arthroplasty. 7. Arthroplasty failure cases include postoperative osteotomy, head and neck resection, and double-cup artificial femoral head and total hip arthroplasty. The main indication for re-surgical surgery is hip pain. Poor joint mobility or to adjust limb length is not a surgical indication. The indications for replacement surgery are: 1 hip pain caused by loosening of the prosthesis; 2 fracture of the prosthesis; 3 dislocation of the prosthesis, failure of the manual reduction; 4 prosthesis caused by acetabular wear and resulting in central dislocation, and Painful. Surgery causes the prosthesis to pass through the femoral shaft. If there is no pain, it is a relative indication for surgery. 8. Bone tumors are located in the low-grade malignant tumors of the femoral head and neck or acetabulum, such as giant cell tumor, chondrosarcoma, etc., and artificial total hip arthroplasty may be considered. If the lesion is affected by large trochanter, a special artificial hip joint is used for replacement surgery. Contraindications 1. Older patients have serious diseases such as heart and lung, kidney, brain and other serious diseases that cannot tolerate major surgery. Patients over the age of 80 should be carefully considered. 2. Those with purulent infection in the hip; those with infection in the urinary system, chest, skin, etc. 3. Neuromuscular disorders affect the hips and surrounding muscles. 4. Local osteopenia (osteopenia) should be identified and considered for surgery. 5. Due to other diseases, it is estimated that patients who cannot be moved to the ground after replacement surgery. Preoperative preparation 1. Fully understand and judge the condition of the patient's vital organs, including electrocardiogram, chest X-ray, erythrocyte sedimentation rate, etc., can tolerate surgery. Understand the condition of the blood vessels (including arteries and veins) of the affected limb, if there is any ischemia or venous thrombosis. 2. Stop the aspirin and anti-infective drugs a few weeks before surgery until the clotting time is normal. Stop steroids. 3. Eliminate the whole body including the skin and infected lesions. 4. Examine the affected limb: the focus is on the hip abductor muscle strength, whether there is muscle contracture causing lower limb deformity, skin scar and so on. Check the length of the lower limbs, hip pain and range of motion, walking function, etc., and accurately record. 5. According to the X-ray film of the double hip pelvis, if necessary, the X-ray film of the spine and knee joint should be taken to understand the defect range of the femoral head and neck injury, the width of the upper femoral medullary cavity and the cortical bone, the acetabular damage and the defect range. 6. Cover the hip X-ray film with a transparent template, determine the size of the artificial prosthesis to be used, and prepare a slightly larger or slightly smaller prosthesis. 7. Applying broad-spectrum antibiotics intravenously 1 to 2 days before surgery, especially those who have undergone surgery or revision surgery on the hips, should be given antibiotics before surgery. Surgical procedure Position and incision The patient was placed on his side, the affected limb was abducted, and the skin was sterilized from the costal margin to the middle of the lower leg. If there is hip flexion deformity, special attention should be paid to the inner thigh and perineal skin sterilization. A sterile towel is placed on the hip and perineum, and the skin edge is sutured and fixed. The upper third of the thigh is wrapped in a sterile towel to the foot, and the large hole is sterile. Cover the trochanter and buttocks with a surgical mask. All participants should be sterilized by iodine, ethanol, and double rubber gloves. The posterolateral incision of the hip was used, starting from the posterior superior iliac spine to the outer 2/3 of the trochanteric line, and the skin was cut in the direction of the trochanter and then folded to the outside of the thigh. Open the gluteus maximus and cut off the attachment point of the gluteal muscle on the femoral shaft, rotate the hip part, reveal the external rotation muscle group, and reveal the piriform muscle closed muscle and upper and lower muscles at the attachment point of the trochanteric space. On the upper and lower edges, a long hemostatic forceps is used to detect between the external rotation muscle group and the hip joint. There are thick blood vessels in the deep outer muscle group, and the external rotation muscle group is clamped, and the hemostasis is cut between the hemostatic forceps and the muscle attachment point. The group of rotator muscles is used to reduce bleeding, and the external rotator muscles are pushed away from the joint capsule to reveal the joint capsule. 2. Acetabular cup replacement Fully expose the acetabulum, remove the joint labrum and posterior joint capsule, and remove the soft tissue in the acetabulum. The cartilage on the underside of the acetabulum is first removed with a slightly smaller acetabulum and directly to the base of the Hoversion notch. Replace the acetabulum 1 to 2 mm smaller than the outer diameter of the metal acetabular cap. The direction of the iliac crest points to the lumbosacral joint, enlarge the acetabulum, and test with a pearl face metal cap until the subchondral bone is slightly bleeding. Bone scraps from under the acetabular bone should be kept for later use. Take the metal acetabular cup test, the pearl face metal cup is best inserted into the acetabulum, or a little tight and gently rubbed into the acetabulum. It can be observed from the metal acetabular cup hole whether the bottom surface of the acetabular cup is closely attached to the bone. If there is a large defect, the cancellous bone should be taken. Remove the metal acetabular cup and apply the bone chips and blood clot mixture that is smashed from the acetabular bone to the surface of the metal acetabular pearl surface, and then gently smash the acetabular cup into the acetabulum. Pay attention to the direction and angle of the acetabular cup. If the shape of the acetabulum is basically normal, the acetabular cup can be placed at the angle of the outer edge of the acetabulum; if the outer edge of the acetabulum is not normal, the acetabular cup can be kept valgus 40° forward and 10° forward. The metal acetabular cup is tight. There are 3 screw holes in the metal acetabular cup. When placing the acetabular cap, the acetabular cup hole should be aligned with the arcuate arch line, pubic symphysis and ischial branch. Use a long drill bit perpendicular to the inner side of the acetabular cup, drill a hole in the hip through the screw hole, and screw the screw vertically. Generally, a screw is placed on the arcuate line, and another screw can be placed on the other side. After the metal acetabular cup is fixed, insert the plastic cap into the metal cup. 3. Artificial femoral head replacement Artificial femoral head replacement should pay attention to three points: 1 artificial femoral head should be placed in the valgus position, avoiding being placed in the varus position; 2 the selected prosthesis stem should be filled with the femoral shaft cavity to avoid swinging; 3 artificial femoral head should be inserted once Be successful and avoid repeating operations. The femoral neck section is the same as the cemented hip replacement. A pre-selected medullary cavity expander with the same distal diameter as the artificial femoral head shank was inserted into the medullary cavity along the proximal trochanteric section of the femoral neck section, the depth slightly exceeding the length of the artificial femoral stem by 1 cm. Remove the medullary cavity expander, take the corresponding model of the artificial femoral head or the small medullary cavity into the medullary cavity, until the medullary cavity all the teeth enter the medullary cavity, pay attention to maintain the anteversion angle. The stalk of the medullary cavity is removed, the iliac cavity is placed on the platform, the femoral section is smoothed, and the femoral head sample is placed on the medullary cavity. The hip was repositioned and the length of the selected femoral head sample was observed to be appropriate. After appropriate, the medullary cavity is removed, and the surface of the pearl surface of the scalloped artificial femoral head is applied to the bone. Insert into the medullary cavity, maintain the anteversion angle, and gently poke in. When invading, each artificial femoral head should advance into the medullary cavity. If the artificial femoral stem is no longer invaded when slamming, do not violently slam, in order to avoid bone fracture, the prosthesis should be removed to enlarge the medullary cavity again. The cervical collar platform of the artificial femoral head after implantation should be in close contact with the femoral neck section. The rest of the operation is the same as the cemented total hip arthroplasty. In order to better achieve the growth of intraosseous tissue into the interfacial space of the pearl, a method of applying the acetabular cup and the pearl surface of the femoral stem can be used. Its role is two: 1 to help fill the gap between the prosthesis and the bone; 2 to facilitate the bone growth of the porous surface, to achieve biological fixation. Animal experiments have shown that, whether it is the acetabular cup or the femoral stem, the intra-osseous growth and interfacial bonding strength of the pearl face applied to the bone mud are better than those without the bone mud group. The source of the bone mud can be taken from the acetabular wear debris or the resected femoral head, if necessary by the acetabulum (bone preserving reamer). complication 1. If there is difficulty in dislocation of the hip joint, the femoral neck can be cut first, then the femoral head can be removed, and the femoral trochanteric truncation can be performed if necessary. 2. The length of femoral neck osteotomy has a regulating effect on the length of the lower limbs, but it is not appropriate to remove too many femoral necks. The length of the lower limb can be adjusted with the length of the prosthetic neck.