Late onset osteoarthritis secondary to hip dysplasia is the most common hip disorder among young people. Reconstruction of the acetabulum and femur is the most difficult part of total hip replacement surgery. Since the patient is relatively young, has an active lifestyle, and has high expectations for the surgery, the surgeon should have a good understanding of the fundamentals of the disease, the surgical technique, and the risks of the procedure.
Staging
Crowe Staging
Stage I <50% Stage II 50-75% Stage III 75-100% Stage IV >100%
Anatomy of acetabular dysplasia
- Bone deformity
C Acetabular changes.
- Shallow
- Tilted acetabulum
- short anterior-posterior diameter
- Increased anterior tilt of the acetabulum
- Superior and anterior acetabular rim defects
C Femoral changes.
- Developmental immaturity
- Left and right diameters of the medullary cavity > anterior and posterior diameters
- Increased anterior femoral tilt angle
- Abnormal position of the greater trochanter of the femur
- Abnormal soft tissues around the hip joint
C Displacement or shortening of muscle tissue
- Abductor muscle
- Iliopsoas muscle
- N cord muscle
- Rectus femoris muscle
C thickening of the joint capsule
Indications for total hip replacement.
- Crowe stage I, II, III with advanced osteoarthritis, severe pain, affecting daily life
- Conservative treatment is ineffective
- Crowe stage IV with only claudication and no pain, especially bilateral lesions, should not be considered for total hip replacement surgery, and joint replacement surgery should only be considered if it is associated with severe pain and dysfunction.
- Surgery should not be considered in cases where claudication is the main complaint
Preoperative preparation
Physical examination
Hip joint deformity or difficulty in movement
Pelvic tilt
Deformity of lumbar spine
Inequality of lower limbs
Surgical scars around the hip joint
Radiological examination
Anterior-posterior hip radiographs
Lateral hip radiographs
Judet radiographs to evaluate bone volume and anterior tilt of the acetabulum
CT evaluation of bone volume and femoral anteversion
Prosthesis and surgical preparation
Acetabulum
Small diameter cup
22 mm femoral head to increase lining thickness
Acetabular reconstruction ring
Preparation of the acetabular implant
Femur
Small straight cemented femoral stem
Non-cemented prosthesis for epiphyseal fixation
Large trochanteric osteotomy or femoral shortening
Surgical methods
Conventional surgical methods and prostheses can be applied in most cases. Four approaches can be used for severe lesions and high dislocations: 1. acetabular dysplasia 2. femoral dysplasia and rotational deformity 3. reconstruction of the adductor muscle 4. management of lower limb inequalities.
Surgical approach
- Posterolateral approach
- Anterolateral approach
- Selective soft tissue release
- Expose the sciatic nerve if necessary
- Transcolumbar approach
- Femoral shortening
Acetabular reconstruction
- Place the cup in the anatomical center of the hip joint as much as possible
Preserve as much bone volume as possible
Obtain initial stability
Avoid the use of structural implants as much as possible
Internal displacement of the acetabular prosthesis to increase femoral deflection moment and increase abductor function
Reconstruction of the acetabular center increases the bony coverage of the acetabular prosthesis
Reconstruction of the acetabular center of rotation is key to long-term outcomes. johnsten found that if the acetabular prosthesis is placed in an internally displaced, narrowly defined, and anteriorly offset position it can significantly reduce the stress load on the acetabulum. stans reported a significantly higher failure rate in patients with CROWE type III if the acetabular prosthesis is placed laterally. linde reported mean 9-year follow-up results for laterally placed Linde reported that 42% of Charnley cemented acetabular prostheses placed laterally failed, while only 13% failed when placed inside the true socket.
Internal acetabular wall penetration technique
The penetration technique of the acetabular prosthesis was introduced by Hess and Umber in 1976 to increase bony coverage of the prosthesis and to avoid the use of bone grafting.Dorr further developed this technique using a non-cemented acetabulum, placing an average of 40% of the acetabular prosthesis medial to the Kohler’s.19 cases (24 hips) of CROWE types II to IV at postoperative The results were good at 5 to 13 years of follow-up. However, this technique sacrifices bone volume in the acetabulum and has a negative impact on future revision surgery.
Internal Acetabular Wall Osteotomy
Internal displacement osteotomy of the acetabulum (Prof. Yoo 1989). Features of the medial acetabular wall transfer osteotomy: Expanding the volume of the bony acetabulum and increasing the bony coverage of the prosthesis. Medial displacement of the acetabular prosthesis. Maintain the center of rotation of the hip joint and improve the biomechanical environment of the artificial joint. Preserve the bony acetabular floor as much as possible. Create conditions to avoid the use of small diameter non-cemented external cups.
Small uncemented cup with screw fixation
In patients with CROWE type IV high dislocation, the true acetabulum is often small and shallow with a large tilt. Because of the severe reduction in bone volume, the use of a small cup and screw fixation may have to be considered. hanssen proposed the use of acetabular file reversal to preserve bone volume. The use of a 22 mm diameter femoral head may increase the thickness of the liner, preferably using high cross-linked polyethylene. hampton and harris reported the results of using a hemispherical microporous coated prosthesis in 20 patients with a mean survival rate of 92% at 16 years of follow-up.
Acetabular hypercenter
Harris and other authors have described the use of high-center placement of the acetabulum, which can also be used with good results when there is a severe lack of bone mass. It has been shown that high-center placement of the prosthesis avoids outward migration and does not affect the biomechanical properties of the hip prosthesis. The use of microporous coated non-cemented socket cups with high cross-linked polyethylene allows for a smooth procedure. pagnano For CROWE type II if the acetabular prosthesis is moved up 15 mm, although there is no outward migration, there is a significant increase in loosening for the acetabular and femoral prosthesis.
Structural acetabular implant
Short-term (5 years) results of autologous or allogeneic structural implants in the external superior acetabular rim are satisfactory. Harris reported revision in 60% of cases after 15 years and failure of autologous femoral head implants in 30%. Therefore, the use of structural implants is currently avoided as much as possible.
Consider implant solution when more than 30% of acetabular prosthesis is exposed
Autologous femoral head has better results than allogeneic femoral head
Non-cemented prosthesis has better results than cemented prosthesis due to good stress transfer performance
Initial stability and precise placement of the implant are essential for a good outcome
Despite a high failure rate, bone grafting can increase bone volume to facilitate revision surgery
Acetabular reconstruction ring
Gill reported satisfactory results with the acetabular reconstruction ring in CROWE type III patients. This approach allows for reconstruction of the hip center, increased coverage of the cemented prosthesis, and increased fixation strength. If reconstruction for 25% does not yield bony coverage, bone grafting should be used to resolve the problem.
Femoral reconstruction
Lateral femoral reconstruction: patients with mild deformity
- Femoral morphology is basically normal, and hip valgus and increased anterior femoral tilt can be seen
- Both cemented and uncemented stems have good fixation
- A special type of prosthesis should be prepared as a backup
Lateral reconstruction of the femur: patients with more severe deformities
- Abnormal stem angle of the femoral neck and abnormally increased anterior tilt angle
- Stenosis of the medullary cavity of the proximal femur
- Inequality of both lower limbs
Bone cement type DDH prosthesis
Small femoral stem diameter, straight stem type
Particularly suitable for inferior transposition of the greater trochanter via the greater trochanter approach
Assembled proximal fixation prosthesis
Facilitates intraoperative correction of the anterior tilt angle
Addresses rotational deformity or facilitates fixation of subtrochanteric osteotomy
Good short-term postoperative follow-up results
Subtrochanteric osteotomy
Excessive inferior displacement of the femur in patients with high dislocation can result in nerve strain and complications. This complication can be prevented by using a subtrochanteric osteotomy.
Advantages: femoral shortening and de-rotation
Reconstruction of the adductor muscle by repositioning the greater trochanter
The degree of shortening is determined by preoperative and intraoperative conditions
Preferably a non-cemented femoral stem
Stepped osteotomy for rotational stability
Complications
- Sciatic nerve injury
- Femoral nerve injury
- Non-healing proximal femoral shortening after osteotomy
- Dislocation
- High failure rate
- Increased rate of infection
- Non-union of the greater trochanter or subtrochanter
- Acetabular fracture and central dislocation of the prosthesis
- Intraoperative femoral fracture
Summary
Total hip replacement for severe dysplasia and complete dislocation is a great challenge for the initial surgery
A thorough understanding of the indications for the procedure, following the principles of reconstruction, and careful handling will increase the success rate of the procedure