Uncemented hip arthroplasty in primary and revision surgery : patterns of bone remodelling and options to influence periprosthetic bone loss

Introduction The incidence of hip arthroplasty surgery in young and active patients is increasing. Consequently, an increasing number of patients will live with hip prostheses for longer periods of time in the future. The mismatch in modulus of elasticity between the stiffer metal components and the surrounding bone will induce periprosthetic adaptive bone remodelling. The clinical importance of this is still uncertain but the risk of late occuring complications, secondary to periprosthetic bone loss, should not be neglected. This thesis focuses on patterns of bone remodelling around uncemented hip implants and on options how to influence the bone remodelling process. Hypotheses We hypothesized that (1) femoral hip revision surgery with a proximally coated uncemented tapered stem is a reliable procedure, with good results, if bone defects at revision are moderate, (2) the femoral adaptive periprosthetic bone remodelling is pronounced after such an operation, (3) oral bisphosphonates, once weekly for six months, will reduce the periprosthetic bone resorption around an uncemented tapered stem up to 2 years after primary hip arthroplasty, (4) an ultra-short wedge shaped uncemented femoral stem gives less periprosthetic bone loss than a conventional uncemented tapered stem, and finally, (5) an acetabular component with a backside coating of a three- dimensional porous titanium construct gives less peri- prosthetic bone loss than a conventional porous- and hydroxyapatite coated titanium acetabular shell. Materials and methods Two different hydroxyapatite coated femoral stems and two titanium acetabular cups, with differing properties regarding shell backside coating and articulating polyethylene, were evaluated. Bone mineral density (BMD) was measured with Dual Energy X-ray Absorptiometry (DEXA). Radiographic assessment was done with consecutive radiographs in study I-III. Implant migration was measured with Einzel-Bild-Röntgen-Analyse (EBRA) in study III and with radiostereometric analysis (RSA) in study IV-V. RSA was also used to analyze polyethylene wear in study V. Clinical outcome was evaluated with self administered score protocols. Results Study I: A retrospective analysis of 60 patients (62 hips), with a mean follow-up of 6 years after unce- mented femoral revision due to aseptic loosening, with moderate bone loss at revision, revealed a stem survival rate of 95%. Radiographical signs of stem osseointegration, as well as diminishing peri-implant osteolysis, were recorded. Study II: In a cross sectional study 22 patients from the cohort in study I, with a healthy hip on the contra- lateral side, were evaluated with DEXA after a mean follow-up of 6 years. We noted a large reduction of 36- 45% in BMD in Gruen zones 1-2 and 6-7 compared to the contralateral hip. Study III: In a randomized, double-blind, placebo- controlled trial of 73 patients operated with an un- cemented stem due to primary osteoarthritis, the treatment group was given risedronate once weekly for 6 months. In the treatment group BMD loss in the proximal femur was reduced with 7% 12 months after surgery but no statistically significant reduction was found after 2 years. Study IV: In a randomized controlled trial of 51 patients periprosthetic bone remodelling was evaluated around an ultra short stem, compared to a convention- al tapered stem, in uncemented THA due to primary osteoarthritis. BMD loss was significantly reduced around the ultra short stem up to 2 years after surgery. Study V: In a randomized controlled trial of 51 patients, comparing two acetabular implants with differing properties regarding shell backside coating and articulating polyethylene, no differences in periproshetic bone remodelling, implant fixation or polyeth- ylene liner wear was found, up to 2 years after surgery. Conclusions Adaptive periprosthetic bone remodelling after uncemented total hip arthroplasty could be reduced with bisphosphonates and with altered stem design. Periacetabular bone demineralization could not be reduced with a new porous titanium construct material. Alpha-tocopherol diffusion of HXLPE liners gave reduced creep but not less polyethylene wear up to 2 years after surgery. An uncemented, proximally porous- and HA- coated tapered stem could be used with good results in femoral revision surgery if bone loss was moderate. Even though stem fixation was excellent, proximal femoral bone demineralization was pronounced

The Ringloc liner compared with the Hexloc liner in total hip arthroplasty

The aim of this study was to compare the 10-year survival rate, pelvic osteolysis frequency and linear head penetration rate of the Hexloc and Ringloc liners used together with a partially threaded porous and hydroxyapatite coated cup and the Bi-Metric uncemented femoral stem. The 15-year results for the cup with the Hexloc liner are also reported. We included 332 consecutive hips (166 Hexloc and 166 Ringloc) on 281 patients in the study. Revisions of prosthesis components were recorded and pelvic osteolytic lesions were assessed using radiographs and computed tomography. The linear head penetration rate was measured using the Martell method. The 10-year survival rate of the liner with revision due to liner wear and/or osteolysis as endpoint was 88% for the Hexloc liner and 98% for the Ringloc liner. The 15-year survival rate of the Hexloc liner was 67%. Pelvic osteolysis was found in 27% of the Hexloc and 19% of the Ringloc hips. After 15 years, 53% of the Hexloc hips had developed an osteolytic lesion. The linear head penetration rate was 0.16 mm/year for the Hexloc liner and 0.12 mm/year for the Ringloc liner. This paper is the first to describe the rapidly deteriorating survival up to 15 years with the old generation gamma-in-air sterilized polyethylene used in Hexloc liners. The newer Ringloc liner with the ArCom™ polyethylene has superior clinical results but a linear wear rate and frequency of osteolytic lesions that is higher than expected

The Ringloc liner compared with the Hexloc liner in total hip arthroplasty

The aim of this study was to compare the 10year survival rate, pelvic osteolysis frequency and linear head penetration rate of the Hexloc and Ringloc liners used together with a partially threaded porous and hydroxyapatite coated cup and the Bi-Metric uncemented femoral stem. The 15-year results for the cup with the Hexloc liner are also reported. We included 332 consecutive hips (166 Hexloc and 166 Ringloc) on 281 patients in the study. Revisions of prosthesis components were recorded and pelvic osteolytic lesions were assessed using radiographs and computed tomography. The linear head penetration rate was measured using the Martell method. The 10-year survival rate of the liner with revision due to liner wear and/or osteolysis as endpoint was 88 % for the Hexloc liner and 98 % for the Ringloc liner. The 15-year survival rate of the Hexloc liner was 67%. Pelvic osteolysis was found in 27 % of the Hexloc and 19 % of the Ringloc hips. After 15 years, 53 % of the Hexloc hips had developed an osteolytic lesion. The linear head penetration rate was 0.16 mm/year for the Hexloc liner and 0.12 mm/year for the Ringloc liner. This paper is the first to describe the rapidly deteriorating survival up to 15 years with the old generation gamma-in-air sterilized polyethylene used in Hexloc liners. The newer Ringloc liner with the ArCom ™ polyethylene has superior clinical results but a linear wear rate and frequency of osteolytic lesions that is higher than expected

HOPE-trial : hemiarthroplasty compared to total hip arthroplasty for displaced femoral neck fractures in the elderly-elderly, a randomized controlled trial

Background: A femoral neck fracture (FNF) is a common cause of suffering and premature death in the elderly population. Optimizing the treatment for improved outcome and a reduced need for secondary surgery is important both for the patient and the society. The choice of primary total or hemiarthroplasty in patients over eighty years are controversial. We hypothesized that total hip arthroplasty has an equal or better outcome in patient-reported outcome compared with hemiarthroplasty. Methods/Design: A prospective, randomized, single-blinded trial will be conducted. We will include 120 patients, 80 years of age and over with an acute (<36 h) displaced femoral neck fracture. The patients will be randomized in a 1: 1 ratio to either total hip arthroplasty or hemiarthroplasty. The primary endpoints are Harris hip Score and EQ-5D. Secondary endpoints include pain measured with visual analogue scale, surgical time, reoperations, complications and radiological measurement of erosion in patients operated with hemiarthroplasty. Follow-up will be performed postoperatively after three months, 1, 2, 4 and 10 years. Discussion: To our knowledge, this is the first randomized controlled trial comparing total hip arthroplasty and hemiarthroplasty for displaced femoral neck fracture in patients age 80 years and over