Ankylosing spondylitis is a chronic progressive disease that mainly affects the mid-axis skeleton, mainly affecting the sacroiliac joint, spine and hip joint, etc. The involvement of the hip joint is prone to joint deformity, and in severe cases, it even causes non-functional ankylosis, which prevents patients from taking care of themselves and has a significant impact on their quality of life. Total hip arthroplasty can effectively improve the quality of life of patients with ankylosing spondylitis who are disabled by hip disorders. In this paper, THA was performed on 18 cases (25 hips) of AS with fibrous or bony ankylosis of the hip joint from March 2003 to October 2008 in our department, and the results were satisfactory.
Clinical data
Case data: 18 patients with AS (according to the revised diagnostic criteria in 1984), 12 males and 6 females; aged 26-42 years, average 31.2 years, 16 hips had bony ankylosis with 0° mobility and 10°-30° hip flexion deformity, 9 hips had fibrous ankylosis with 10°-30° mobility, the first symptoms in all cases were low back pain and morning stiffness, from the onset of AS The time from the onset of AS to the appearance of severe deformity of the hip joints bilaterally ranged from 5 to 11 years, with an average of 6.5 years. The patients were unable to take care of themselves or were only partially self-caring. Among them, 7 cases were combined with knee and lower back pain.
Preoperative preparation
Before surgery, the soft tissues around the hip joint were carefully examined to understand the muscle strength around the hip, and X-ray films of the spine, pelvis, upper femur and both knees were taken to fully understand the fusion and deformity of the hip joint and the traces of the original acetabulum, so as to facilitate the selection of the artificial prosthesis. Laboratory examinations were performed in all patients with leukocyte and platelet counts in the normal range, negative for rheumatoid factor, and positive for HLA-B27. 13 patients had a slightly faster sedimentation rate (ESR) of 25-30 mm/h, and 9 patients had an increased C-reactive protein (CRP).
Surgical method
A tracheal intubation anesthesia was used, and a posterior-lateral hip incision was made. For non-osseous ankylosis, osteotomy followed by acetabuloplasty was used to release the soft tissues around the joint. For bony ankylosis of the hip joint, two osteotomies were performed, firstly, the femoral neck was osteotomized 1.0-1.5 cm above the lesser trochanter, and then the femoral neck was osteotomized 15º anteriorly at the acetabular rim, using the fat layer between the femoral head and the acetabulum as the basis for identifying the true socket. The acetabular and femoral stem prostheses were all non-cemented HA-coated prostheses.
Results
The follow-up was 1-6 years. The postoperative evaluation criteria were based on the Harris scoring system for clinical outcome evaluation. It included joint pain, joint mobility and overall functional evaluation. The score was 100. 90-100 was excellent, 80-89 was good, and 70-79 was moderate. < 70 is poor. Preoperative hip mobility was 0° in 16 hips and 1° in 9 hips. After surgery, the hip flexion deformity disappeared, and the range of hip movement reached 80°~105° in forward flexion, with an average of 85.5° and 5°~15° in back extension, with an average of 9.5°. 25 hips had no deformity after surgery; no dislocation and other complications occurred.
The overall functions of the patients were not self-care before surgery, 5 patients were bedridden or wheelchair-bound for a long time, 13 patients were partially self-care, and 13 patients needed to support double crutches; after surgery, all patients could walk up and down stairs without obvious limp, could put on shoes or sit on the toilet by themselves, and were basically self-care. All patients were able to walk outdoors, and the original pain partially or completely disappeared.
The postoperative efficacy evaluation of Harris score ranged from 8 to 56 preoperatively, with an average of 32 points. The postoperative scores ranged from 60 to 96, with a mean of 83, an average increase of 51 points compared with the preoperative scores. Among them, 14 hips were excellent, 7 hips were good, and 4 hips were moderate, with an excellent rate of 81.8%. Imaging evaluation of the femoral and acetabular prostheses was performed using Grucn et al. and the DeeleandChamley partition method. Imaging evaluation of 2 hips showed translucent lines <2 mm in zone 1 of the socket cup, and 2 femoral stem prostheses had discontinuous translucent lines <2 mm in zones 2,and 6. 3 hips ( 13.6%) had heterotopic ossification, 2 hips according to Brooker classification grade I; 1 hip grade III. By the last 1 follow-up, there were no signs of infection, dislocation, or prosthesis loosening in any of the 25 medullary joints.
DISCUSSION
The age of patients with AS hip ankylosis is usually young, mostly in older children, and the peak is usually between 12 and 16 years old.
Therefore, early diagnosis and treatment of AS should be emphasized, and patients at high risk for AS who develop hip lesions at a younger age should be actively prevented from being bedridden, have their pain controlled, and maintain the functional position of their limbs. Avoid failure to maintain the correct position due to pain in the early stage of the lesion, which may cause the joint to straighten in a non-functional position. Long-term ankylosis of the limb in a non-functional position is more likely to result in muscle atrophy near the joint and disuse osteoporosis, which will have a negative impact on future surgery and postoperative functional exercise.
The longer the time, the more serious the atrophy of the muscles around the hip joint, which often results in bony ankylosis of the hip joint in the middle and late stages. In the middle and late stages, it often causes osteoarthritic ankylosis of the hip joint, which can be accompanied by multiple joint involvement and osteoporosis. This makes it different from other hip disorders.
There is a significant difference in the efficacy of THA compared to early and late stage AS, and the longer the duration of the disease, the more severe the atrophy. The more severe the atrophy. The more advanced the disease, the more severe the atrophy, and the more difficult the surgery. The later the hip ankylosis surgery is performed, the more difficult it is to recover the function of the hip joint after surgery, and the worse the functional recovery. It is now believed that THA can be performed when the patient has pain and stiffness in the hip joint and the efficacy of pharmacological treatment is uncertain; elevated ESR and active lesions are not contraindications to surgery, and age is no longer a threshold for THA in these patients.
The femoral neck was resected and the acetabular joint was bony ankylosis in AS. It was difficult to identify the true boundary between the femoral head and the acetabulum.
The femoral neck was then osteotomized twice at the acetabular rim with an anterior tilt angle of 15°. With bony ankylosis, the femoral head is completely fused with the acetabular rim, and finding the original acetabular rim is sometimes difficult. The joint capsule, which is already tightly united with the bone, should be completely removed, and its union on the acetabular side is the original acetabular rim. Special attention should be paid to the identification of the true acetabulum before acetabuloplasty.
The boundary between the true acetabulum and the femoral head can be made by identifying the transverse acetabular ligament after osteotomy of the femoral neck. After the identification is clear, the femoral head can be removed. We use an acetabular file to remove the femoral head directly, i.e., a small acetabular file is aimed directly at the residual femoral head, and the diameter of the acetabular file is increased in turn; until the femoral head and the completely ossified residual cartilage are completely filed out, the original femoral head must be completely removed, and the fatty tissue in the original acetabular fossa can also be used as a marker.
In this group of cases, regardless of the duration of bony ankylosis of the hip joint, none of the cases had complete ossification of the fatty tissue in the original acetabular fossa, which can be used as a reference for filing out the bone. During the operation, we should pay attention to the patient’s body position and adjust the direction of the acetabular file at any time so that the acetabular file is completely aligned with the center of the original acetabulum; because of the long-term braking of AS patients, osteoporosis is common, so when grinding the acetabulum and installing the acetabular prosthesis, do not use excessive force to avoid perforation and fracture of the acetabulum
In conventional total hip arthroplasty, the acetabular prosthesis should be placed with 40±10° of abduction and 15-20° of anteversion, and the femoral prosthesis should be placed with 10-5° of anteversion. Patients with ankylosing spondylitis often have a variety of hip deformities, such as flexion deformity, abduction or adduction deformity, internal or external rotation deformity, etc. In patients with severe hip deformities, although the deformity can be corrected to normal during surgery, there is still a tendency for the deformity to recur after surgery.
If the prosthesis is placed according to the conventional method, it will increase the possibility of postoperative hip dislocation. In order to ensure the stability of the hip joint after surgery, the angle of intraoperative prosthesis placement should be adjusted according to the specific situation of the hip deformity. For simple hip flexion deformity, the anterior tilt angle of the acetabular prosthesis should be increased, and the anterior tilt angle of the femoral prosthesis should be reduced.
For combined lower limb internal rotation deformity, the anterior tilt angle of the acetabular prosthesis should be appropriately reduced and the anterior tilt angle of the femoral prosthesis should be appropriately increased. For the combined lower limb external rotation deformity, the anterior tilt angle of the acetabular prosthesis should be increased appropriately, and the anterior tilt angle of the femoral prosthesis should be reduced appropriately or kept at 0° anterior. In cases of combined adduction deformity, in addition to cutting off part of the contracted adductor muscle, the abduction angle of the acetabular prosthesis should be appropriately reduced, which may affect the abduction of the hip joint, but can increase the stability of the joint.
Intraoperative soft tissue release and protection of nerves and blood vessels For patients with hip ankylosis in the extension position, soft tissue release is not possible, while in the flexion position, the soft tissue in front of the joint must be released, otherwise it will affect the recovery of postoperative function.
The tissues to be released include the anterior joint capsule, iliopsoas muscle, rectus femoris, iliotibial bundle, sutures muscle, and sometimes the adductor muscle group. For patients with severe preoperative deformity, the release of the joint capsule and soft tissues should be adequate and moderate. When passively straightening the hip joint after releasing the above-mentioned tissues, do not use violence, and do not fully straighten the affected hip to avoid strains on the femoral artery, vein and nerve. After recovery from anesthesia, the hip joint was gradually straightened according to the patient’s sensation.
The selection of the prosthesis was based on the patient’s orthopantomogram of the hip joint, and different sizes of prosthesis were prepared. For patients <55 years old, a non-cemented prosthesis should be used for the first total hip arthroplasty, because most patients with advanced ankylosing spondylitis are young and have active bone proliferation,
If the prosthesis is mechanically stabilized immediately during surgery, the new bone can grow more into the surface micropores of the artificial joint prosthesis and achieve long-term stability of the prosthesis.
The loosening rate in the long term is lower than that of cemented prostheses. A ten-year interim survey showed that uncemented total hips provide excellent fixation. Furthermore, the initial use of a non-cemented prosthesis leaves a good foundation for subsequent revision of the artificial joint.
However, for older patients with obvious osteoporosis, cemented prostheses can be used; for those with osteoporosis in the acetabulum and no obvious osteoporosis in the femur, cemented acetabular and non-cemented femoral prostheses are used. In this group of cases, which are relatively young, we used non-cemented prosthesis to treat ankylosing spondylitis and hip ankylosis, and no loosening or displacement of the prosthesis occurred in 18-47 months of follow-up, but its long-term follow-up results need to be further observed.