Research SummaryA randomized controlled study comparing Computer Aided Design (CAD) model vs conventional technique for Total Hip Arthroplasty in patients with fused hips and spinopelvic deformit
Total Hip Arthroplasty (THA) ranks as one of the most rewarding surgeries yet devised. It has afforded pain relief and improved quality of life for millions of patients worldwide. The number is increasing in an exponential manner even in India. Being an apex institute, a number of complex Hip replacement surgeries are performed routinely in All India Institute of Medical Sciences. One of those challenging surgeries is Total Hip Arthroplasty in patients with fused hips due to Ankylosing Spondylitis. Most of the patients are young adults and the stability remains the most important factor in its outcome after Total Hip Arthroplasty in them. One of the major intraoperative challenges in total hip arthroplasty (THA) in these patients with bony ankylosis is to find a correct balance between hip biomechanics, tribology and post-operative functionality. In cases with fused hips, it is difficult to prepare an adequate surgical plan for acetabular replacement. The normal anatomy is jeopardized along with hip ankylosis in patients with Ankylosing Spondylitis. In addition to this, there is spinopelvic deformity. The stability of Total Hip Arthroplasty primarily depends on the positioning of acetabular component. The orientation of acetabular component in turn is influenced by several factors such as the pelvic tilt, body position and individual variation in pelvic parameters. Most of the post-operative adverse events occur as a result of malpositioning of components in functional position. Conventionally, the component positioning is done in static lying position during the surgery but the dislocation occurs in these patients due to the dynamic phenomenon that is seen with the change of position like sitting and walking which are the movements executed in daily living. So, even an anatomically oriented cup placed in supine position may functionally prove to be wrongly oriented favoring subsequent instability and poor outcome while the patient stands and walks. A thorough pre-operative planning is imperative for total hip arthroplasty (THA) in these patients so as to decrease the possible adverse outcome. It could be obtained by a technique called rapid prototyping (RP) modeling using a three-dimensional Computer Aided Design (CAD) data. These models can be used as an essential tool to plan for the surgery and preoperative rehearsal prior to the surgery. In total hip arthroplasty for ankylosed hips, such models would be helpful in determining the level and direction of the femoral neck osteotomy, the depth of acetabular reaming, and most importantly, positioning and placing of the components taking into account the distorted pelvifemoral anatomy and spatial orientation of the pelvis and spine so as to obtain functionally stable hip. We wish to compare the clinical and radiological outcome in patients undergoing Total Hip Arthroplasty for fused hips using the model with those without using it (control group). We wish to find out that whether the pelvic parameters get changed or not in these patients after the surgery. We also wish to find out an algorithm (specific protocol) for the cases with fused hips whereby the optimum component position can be defined independent of the bony anatomy. This will be done by calculating the relationship between the magnitude and the direction of the spinopelvic deformity, and, change required in the position of components to achieve a stable hip This protocol will help the fellow surgeons in planning the Total Hip replacement surgery in fused hips with optimum component positioning adequate stability with functional range of motion and minimal wear of bearing surfaces. We encounter a number of patients with fused hips who need Total Hip Replacement in our institute. No such study has ever been designed and conducted in India.