Mats Salemyr

Periprosthetic proximal bone loss after uncemented hip arthroplasty is related to stem size: DXA measurements in 138 patients followed for 2-7 years.

Background Periprosthetic bone loss occurs around uncemented femoral stems and may be influenced by the stem size. Patients and methods We studied 138 consecutive patients, 3 (2–7) years on average after a total hip arthroplasty operation (THA) for unilateral osteoarthritis with the Bi-Metric uncemented femoral stem. We analyzed Harris hip score and bone mineral density. Results The mean Harris hip score was 97 at follow-up. Bone mineral density decreased proximally by 19% in both Gruen zones 1 and 7. Bone loss in zones 1, 2, 6, and 7 was significantly associated with stem size. Distally, a small gain in bone mass was found in zones 3 and 5 for medium femoral sizes. Interpretation We found a marked proximal BMD loss, especially for the larger stems, which may be specific for this particular implant. Long-term studies should reveal whether this proximal bone loss will affect the longevity of the THA.

Continuous bone loss around a tapered uncemented femoral stem: A long-term evaluation with DEXA

Background Periprosthetic bone loss is a well-docu-mented phenomenon after uncemented total hip arthroplasty (THA); however, little is known about how bone mineral density (BMD) changes after 2 years. Patients and methods 14 patients with hip arthrosis (group A) were operated with a proximally porous- and hydroxyapatite-coated stem and followed for 10 years with DEXA, radiographs and Harris hip score (HHS). Another group of 14 patients (group B) was evaluated at 6 and 14 years using the same prosthesis and protocol. Results No stem was revised and all stems were well-Fixed. At final follow-up, HHS was 97 points in group A after 10 years and 94 points in group B after 14 years. Bone mineral changes in group A were greatest in Gruen zones 1 and 7, where the losses were 31% and 26%, respectively, after 2 years on the operated side. The decrease in BMD continued after 2 years and in Gruen zone 7 it was faster than the rate of bone loss on the control side. In group B, the annual change in BMD on the operated side was not significantly different from the bone loss in group A. Interpretation Up to 14 years after implantation of a tapered uncemented stem, the BMD in the calcar region continues to decrease faster than would be expected from normal ageing.

The effect of weekly risedronate on periprosthetic bone resorption following total hip arthroplasty: a randomized, double-blind, placebo-controlled trial.

BACKGROUND Bone loss leading to late-occurring periprosthetic femoral fracture is a mode of failure in cementless total hip arthroplasty. The aim of this trial was to investigate the effect of a bisphosphonate, risedronate, on femoral periprosthetic bone resorption following total hip arthroplasty in patients with osteoarthritis of the hip. METHODS We enrolled seventy-three patients between the ages of forty and seventy years who were scheduled to undergo total hip arthroplasty in a single-center, randomized, double-blind, placebo-controlled trial. Subjects were randomly assigned to receive either 35 mg of risedronate (n = 36) or a placebo (n = 37) orally once weekly for six months. The primary end point was the change in bone mineral density in Gruen femoral zones 1 and 7. Bone mineral density scans were made preoperatively and at two days and three, six, twelve, and twenty-four months postoperatively. Secondary end points included migration of the femoral stem and clinical outcome. RESULTS Seventy of the seventy-three patients (thirty-three in the risedronate group and thirty-seven in the placebo group) were analyzed for the primary end point. The mean bone mineral density in zone 1 was 9.2% higher (95% confidence interval [CI], 4.2% to 14.1%) in the risedronate group than in the placebo group at six months postoperatively and 7.2% higher (95% CI, 1.0% to 13.3%) at one year. The mean bone mineral density in zone 7 was 8.0% higher (95% CI, 2.7% to 13.4%) in the risedronate group than in the placebo group at six months postoperatively and 4.3% higher (95% CI, -1.5% to 10.1%) at one year. Migration of the femoral stem, the clinical outcome, and the frequency of adverse events did not differ between the groups. CONCLUSIONS Risedronate taken once weekly for six months following total hip arthroplasty was effective in reducing periprosthetic bone resorption around an uncemented femoral stem up to one year after surgery but had no discernible effect on implant migration or clinical outcome. Future studies of bisphosphonate treatment following total hip arthroplasty should focus on clinically relevant end points such as the risks of fracture and revision arthroplasty.

Reduced dislocation rate after hip arthroplasty for femoral neck fractures when changing from posterolateral to anterolateral approach

Background and purpose Recent studies have shown that compared to the posterolateral approach, the anterolateral approach reduces the risk of dislocation after hip arthroplasty in patients with femoral neck fractures. We have therefore started to use the anterolateral approach on these patients and we now report the consequences of this change for the dislocation rate. Patients and methods We chose two 1-year time periods, 2007 (n = 199) and 2008 (n = 173), the former being before and the latter after the implementation of the anterolateral approach as the standard incision for hip arthroplasties in patients with femoral neck fractures. During 2007, 77% of the hips were operated on with the posterolateral approach and in 2008, 78% of the hips were operated on using the anterolateral approach. Results The dislocation rate was reduced from 8% (16/199) in 2007 to 2% (3/173) in 2008. A multivariable logistic regression analysis showed that the posterolateral approach was the only factor associated with an increased risk of dislocation, with an odds ratio of 8 (2–35). Age, sex, ASA classification, type of arthroplasty, cognitive dysfunction, or the experience of the surgeon had no effect on the risk of dislocation. Interpretation Since most of our surgeons had earlier used the posterolateral approach when performing hip arthroplasties in patients with a femoral neck fracture, this study shows our surgical learning curve. We conclude that a collective policy change regarding surgical approach for these patients is both feasible and to be recommended, as it leads to a substantial reduction in dislocation rate.

Lower periprosthetic bone loss and good fixation of an ultra-short stem compared to a conventional stem in uncemented total hip arthroplasty: A randomized clinical trial with DXA and RSA in 51 patients

Background and purpose — We hypothesized that an ultra-short stem would load the proximal femur in a more physiological way and could therefore reduce the adaptive periprosthetic bone loss known as stress shielding. Patients and methods — 51 patients with primary hip osteoarthritis were randomized to total hip arthroplasty (THA) with either an ultra-short stem or a conventional tapered stem. The primary endpoint was change in periprosthetic bone mineral density (BMD), measured with dual-energy x-ray absorptiometry (DXA), in Gruen zones 1 and 7, two years after surgery. Secondary endpoints were change in periprosthetic BMD in the entire periprosthetic region, i.e. Gruen zones 1 through 7, stem migration measured with radiostereometric analysis (RSA), and function measured with self-administered functional scores. Results — The periprosthetic decrease in BMD was statistically significantly lower with the ultra-short stem. In Gruen zone 1, the mean difference was 18% (95% CI: −27% to −10%). In zone 7, the difference was 5% (CI: −12% to −3%) and for Gruen zones 1–7 the difference was also 5% (CI: −9% to −2%). During the first 6 weeks postoperatively, the ultra-short stems migrated 0.77 mm more on average than the conventional stems. 3 months after surgery, no further migration was seen. The functional scores improved during the study and were similar in the 2 groups. Interpretation — Up to 2 years after total hip arthroplasty, compared to the conventional tapered stem the ultra-short uncemented anatomical stem induced lower periprosthetic bone loss and had equally excellent stem fixation and clinical outcome.

A new uncemented hydroxyapatite-coated femoral component for the treatment of femoral neck fractures: two-year radiostereometric and bone densitometric evaluation in 50 hips.

Our aim in this pilot study was to evaluate the fixation of, the bone remodelling around, and the clinical outcome after surgery of a new, uncemented, fully hydroxyapatite-coated, collared and tapered femoral component, designed specifically for elderly patients with a fracture of the femoral neck. We enrolled 50 patients, of at least 70 years of age, with an acute displaced fracture of the femoral neck in this prospective single-series study. They received a total hip replacement using the new component and were followed up regularly for two years. Fixation was evaluated by radiostereometric analysis and bone remodelling by dual-energy x-ray absorptiometry. Hip function and the health-related quality of life were assessed using the Harris hip score and the EuroQol-5D. Up to six weeks post-operatively there was a mean subsidence of 0.2 mm (-2.1 to +0.5) and a retroversion of a mean of 1.2° (-8.2° to +1.5°). No component migrated after three months. The patients had a continuous loss of peri-prosthetic bone which amounted to a mean of 16% (-49% to +10%) at two years. The mean Harris hip score was 82 (51 to 100) after two years. The two-year results from this pilot study indicate that this new, uncemented femoral component can be used for elderly patients with osteoporotic fractures of the femoral neck.

Good results with an uncemented proximally HA-coated stem in hip revision surgery: 62 hips followed for 2–13 years

Background and purpose Proximal bone loss due to stress-shielding is a matter of concern after uncemented femoral hip revision. We have used short, proximally hydroxyapatite-coated prostheses in revision since 1989, and we now report the results. Methods 60 patients (62 hips) were revised because of aseptic loosening. Bone defects prior to revision were mostly of type II according to the Gustilo-Pasternak and Endo-Klinik classifications. Follow-up time was 73 (24–161) months. 9 patients had died before follow-up; 8 of these still had the stem in place. Clinical assessment was performed with the Harris hip score. Radiographs were evaluated for bone defects at revision, postoperative stem fixation, and periprosthetic bone remodeling. Results Mean Harris hip score was 75 (30–100) points. There was no stem loosening or progressive subsidence. 8 patients had mild to moderate thigh pain. Osteolysis, present at revision, had diminished, partially or completely, in four-fifths of the hips at follow-up. 4 hips had required re-revision due to fracture or dislocation. The 6-year prosthesis survival rate was 95% (95% CI: 0.83–0.98). Interpretation Uncemented revision with a short, proximally hydroxyapatite-coated prosthesis is a reliable procedure with encouraging results in the medium term if bone defects at revision are moderate.

No effect of risedronate on femoral periprosthetic bone loss following total hip arthroplasty: A 4-year follow-up of 61 patients in a double-blind, randomized placebo-controlled trial

Background and purpose — We have previously shown that during the first 2 years after total hip arthroplasty (THA), periprosthetic bone resorption can be prevented by 6 months of risedronate therapy. This follow-up study investigated this effect at 4 years. Patients and methods — A single-center, double-blind, randomized placebo-controlled trial was carried out from 2006 to 2010 in 73 patients with osteoarthritis of the hip who were scheduled to undergo THA. The patients were randomly assigned to receive either 35 mg risedronate or placebo orally, once a week, for 6 months postoperatively. The primary outcome was the percentage change in bone mineral density (BMD) in Gruen zones 1 and 7 in the proximal part of the femur at follow-up. Secondary outcomes included migration of the femoral stem and clinical outcome scores. Results — 61 of the 73 patients participated in this 4-year (3.9- to 4.1-year) follow-up study. BMD was similar in the risedronate group (n = 30) and the placebo group (n = 31). The mean difference was −1.8% in zone 1 and 0.5% in zone 7. Migration of the femoral stem, the clinical outcome, and the frequency of adverse events were similar in the 2 groups. Interpretation — Although risedronate prevents periprosthetic bone loss postoperatively, a decrease in periprosthetic BMD accelerates when therapy is discontinued, and no effect is seen at 4 years. We do not recommend the use of risedronate following THA for osteoarthritis of the hip.

Large femoral bone loss after hip revision using the uncemented proximally porous-coated Bi-Metric prosthesis: 22 hips followed for a mean of 6 years.

Background and purpose Periprosthetic bone loss after uncemented femoral hip revision is a matter of concern. We have used a proximally porous- and hydroxyapatite-coated prosthesis (Bi-Metric) in revision since 1989 and now we report the bone changes. This prosthesis is intended to distribute the forces more evenly and to avoid proximal femoral unloading. Methods 22 patients were unilaterally reoperated because of aseptic loosening. Only patients with a healthy contralateral hip were included. Mean age at revision was 69 (55–80) years. Bone defects were graded by Gustilo-Pasternak and Endo-Klinik classifications. Clinical assessment was performed with Harris hip score. We used radiographs and dual-energy X-ray absorptiometry to evaluate migration, femoral remodeling, and bone mineral density after 72 (30–158) months. Results The mean Harris hip score was 74 (30–100) points at follow-up. Mild thigh discomfort was present in 1 patient and moderate thigh pain in 3 patients. There was no loosening or subsidence. Osteolysis seen at revision had diminished in 19 of the 22 hips at follow-up. We noted a large reduction in bone mineral density. It was most pronounced in Gruen regions 1, 2, 6, and 7. Interpretation Revision with this stem is a reliable procedure; however, we noted a large degree of proximal bone loss that could lead to later mechanical complications or fractures.

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.