Dilemmas in Uncemented Total Hip Arthroplasty

In this thesis, different aspects that are related to the survivorship and clinical outcome in uncemented total hip arthroplasty are analysed. In Chapter 2, the survival rate, Harris Hip score and radiographic features of a proximally hydroxyapatite coated titanium alloy femoral stem (Bi-Metric, Biomet) was evaluated. In conclusion, at an average follow-up of 8 years, this proximally HA-coated femoral component showed favorable clinical and radiological outcome and excellent survivorship. In Chapter 3, a systematic review was performed to determine the clinical and radiological benefit of hydroxyapatite coating compared with porous coating in uncemented primary total hip arthroplasty. In conclusion, this meta-analysis demonstrates no clinical nor radiologic benefits on the application of a hydroxyapatite coating on a femoral component in uncemented primary total hip arthroplasty. In Chapter 4, the survival rate, Harris hip score and radiographic features of a low modulus, PTFE (Proplast, Bitek) coated femoral stem was evaluated. In conclusion, the low modulus, PTFE (Proplast coated) femoral stem is associated with a poor clinical and radiological outcome. All patients should be thoroughly screened for radiographic progressive osteolysis or the occurrence of thigh pain. In Chapter 5, we hypothesised that a hemiprosthesis used without cement has a considerable high revision rate, based on aseptic loosening. A hemiprosthesis, which is designed for both cemented and uncemented fixation (Conquest, Smith&Nephew), was used. In conclusion, because of the rather high revision rate, the authors advice not to use this hemiprosthesis without cement. In Chapter 6, a proposed algorithm for surveillance and treatment of silent osteolysis is presented. When a cavitational laesion is observed, even without any clinical symptoms, a helical CT scan should be performed yearly and treatment with bisphosphonates is to be considered. In case of segmental osteolysis or progression of the cavitational laesion, extensive debridement of the osteolytic cysts, bone grafting and replacement of the polyethylene liner is the treatment of choice. In Chapter 7, the rate of polyethylene wear of a cementless acetabular component (Mallory-Head/Ringloc, Biomet) at different periods of follow-up was investigated in order to test the hypothesis than an irrecoverable deformation process (creep) was followed by an initially low, but gradually increasing wear rate. In conclusion, penetration rates of the femoral head into the polyethylene liner of the acetabular component are variable. A significant, increased rate of polyethylene wear can be seen after nine years of implantation, created by a mechanical degradation of the polyethylene surface. In Chapter 8, the femoral penetration rates were measured in inserts, sterilised in oxygen containing air (Ringloc, Biomet) and inserts, sterilised in Argon liners, during a follow-up of 8 (3 to 12) years. In conclusion, it can be stated that the in vivo penetration rate of the femoral head is significantly lower in argon-sterilised than air-sterilised UHMWPE liners. In Chapter 9, the standard posterolateral and anterolateral and minimally invasive approaches were compared in a randomized, blinded trial in 120 patients. This study reveals an improved clinical outcome of the posterolateral MIS compared with the other approaches after six weeks and one year follow-up.