Periprosthetic femoral fracture within two years after total hip replacement: analysis of 437,629 operations in the nordic arthroplasty register association database.

BACKGROUND: We used the Nordic Arthroplasty Register Association database to evaluate whether age, sex, preoperative diagnosis, fixation, and implant design influence the risk of revision arthroplasty due to periprosthetic fracture within two years from operation of a primary total hip replacement. METHODS: Included in the study were 325,730 cemented femoral stems and 111,899 uncemented femoral stems inserted from 1995 to 2009. Seven frequently used stems (two cemented stems [Exeter and Lubinus SP II] and five uncemented stems [Bi-Metric, Corail, CLS Spotorno, ABG I, and ABG II]) were specifically studied. RESULTS: The incidence of revision at two years was low: 0.47% for uncemented stems and 0.07% for cemented stems. Uncemented stems were much more likely to have this complication (relative risk, 8.72 [95% confidence interval, 7.37 to 10.32]; p < 0.0005). Age had no consistent influence on the risk for revision of cemented stems, but revision in the uncemented group increased with increasing age. A cemented stem was associated with a higher risk in male patients compared with female patients (hazard ratio, 1.95 [95% confidence interval, 1.51 to 2.53]; p < 0.0005), whereas an uncemented stem was associated with a reduced risk in male patients compared with female patients (hazard ratio, 0.74 [95% confidence interval, 0.62 to 0.89]; p = 0.001). The risk for revision due to early periprosthetic fracture increased during the 2003 to 2009 period compared with the 1995 to 2002 period both before and after adjustment for demographic factors and fixation (relative risk, 1.44 [95% confidence interval, 1.18 to 1.69]; p < 0.0005). The hazard ratio for the Exeter stem was about five times higher than that for the Lubinus SP II stem (hazard ratio, 5.03 [95% confidence interval, 3.29 to 7.70]; p < 0.0005). Of the five uncemented stems, the ABG II stem showed an increased hazard ratio of 1.63 (95% confidence interval, 1.16 to 2.28) (p = 0.005), whereas the Corail stem showed a decreased hazard ratio of 0.47 (95% confidence interval, 0.34 to 0.65) (p < 0.0005) compared with the reference Bi-Metric design. CONCLUSIONS: The shape and surface finish of the femoral stem and its fixation could be related to the increased risk of some prosthetic designs. Even if the incidence of early periprosthetic fracture in general is low and other reasons for revision must be considered, specific attention should be given to the choice of fixation and stem design in risk groups. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Fixation and bone remodeling around a low-modulus stem seven-year follow-up of a randomized study with use of radiostereometry and dual-energy x-ray absorptiometer.

Thirty-eight patients (40 hips) randomly received either an uncemented fully porous-coated composite stem (Epoch; Zimmer, Warsaw, Ind) or an uncemented proximally porous-coated solid stem (Anatomic; Zimmer). Patients were followed up for 7 years using radiostereometry, dual-energy x-ray absorptiometry, conventional radiography, the Harris Hip Score, and a pain questionnaire. Both stem designs achieved excellent outcome for fixation (stem subsidence and stem rotations close to zero) and clinical outcome, without any difference between the 2 groups (P > .12). Median wear rates were low despite use of conventionally gamma-sterilized polyethylene. No stem was radiographically loose on the postoperative radiographs. The low-modulus composite stem had positive effects on early proximal bone remodeling in Gruen regions 1, 2, 6, and 7 (P < .04). However, at 7 years, this bone-sparing effect persisted in only the calcar region (Gruen region 7).

Design-related risk factors for revision of primary cemented stems.

BACKGROUND AND PURPOSE: Even small design variables of the femoral stem may influence the outcome of a hip arthroplasty. We investigated whether design-related factors play any role in the risk of non-aseptic revision of the 3 most frequently used primary cemented stem designs in the Swedish Hip Arthroplasty Register. PATIENTS AND METHODS: We studied 71,184 primary cemented femoral stem implants (21,008 Exeter polished stems, 43,036 Lubinus SPII stems, and 7,140 Spectron EF Primary stems) that were inserted from 1999 through 2006. Design-specific characteristics were analyzed using separate Cox regression models that were adjusted for sex, age, diagnosis, incision, and number of operations (first vs. second). RESULTS: The crude revision rate varied between 0.8% (Lubinus SPII) and 1.4% (Spectron Primary). For the Exeter stem, the smallest femoral head diameter (22 mm) was associated with a higher risk of revision. No other design-specific parameters influenced the risk of revision of the Exeter stem. The smallest Lubinus stem size, a stem with extended neck length combined with a femoral head with increasing neck length, or the use of a cobalt-chromium head had a negative influence on the outcome. For the Spectron stem, the risk of revision was elevated for the smallest stem and for increasing offset calculated as the combined effect of high offset design and increasing neck length. INTERPRETATION: Overall revision rates were low, but for two of the stems studied design factors such as size and neck length or offset influenced the risk of non-aseptic revision.

Randomized comparison between 3 surface treatments of a single anteverted stem design: 84 hips followed for 5 years.

Eighty patients (84 hips) randomly received an anteverted cobalt-chromium stem (Lubinus SP2; Waldemar Link, Hamburg, Germany) with matte, polymethyl methacrylate-coated, or polished surface (uncollared). Radiostereometry was used to study migration and wear; and the bone mineral density was studied with dual-energy x-ray absorptiometry at 6 months, 1 year, 2 years, and 5 years. The polished stems had subsided 0.1 to 0.2 mm more at 6 months and 0.3 to 0.4 mm more at 5 years than the matte and precoated versions (P < .0001) and subsided mainly inside the cement mantle. The rotations of the stem and the migration and wear of the cemented cup did not differ between the 3 groups. After 1 and 2 years, the polished stems had lost significantly less bone mineral in Gruen zones 1, 2, 6, and 7 (P = .004 to .03); but this difference had disappeared after 5 years. The period of improved bone remodeling around the polished version coincided with the early period of increased subsidence, suggesting that stem motions inside the mantle resulted in a favorable loading of the proximal femur. Our observations suggest that alternative shapes could be possible on future polished femoral stem designs.

Acetabular revision with impacted morselized cancellous bone graft and a cemented cup in patients with rheumatoid arthritis. A concise follow-up, at eight to nineteen years, of a previous report.

We previously reported our results at a minimum of three years after thirty-five revisions of total hip arthroplasty acetabular components in twenty-eight patients with rheumatoid arthritis. The revisions were performed with use of impacted morselized bone graft and a cemented cup. This update report presents the results at eight to nineteen years after the surgery, which, to our knowledge, is the longest follow-up available in the literature. No patient was lost to follow-up. Since our previous report, there were two additional cup failures due to aseptic loosening, at ten and sixteen years postoperatively. Kaplan-Meier analysis showed the probability of survival of the acetabular component at twelve years to be 80% (95% confidence interval, 65% to 95%) with removal of the cup for any reason as the end point and 85% (95% confidence interval, 71% to 99%) with aseptic loosening as the end point. Cup revisions performed with cement and use of impaction bone-grafting in patients with rheumatoid arthritis led to acceptable long-term prosthetic survival rates. This technique is attractive from a biological standpoint because of the possibility of maintaining acetabular bone stock.

Immediate weight bearing after uncemented total hip arthroplasty with an anteverted stem: a prospective randomized comparison using radiostereometry.

BACKGROUND: In uncemented total hip arthroplasty with hydroxyapatite coating, early weight bearing is frequently practiced but there is still not much evidence to support this recommendation. METHOD: In a prospective randomized study we evaluated the effect of partial and full weight bearing after cementless total hip arthroplasty (ABG; Stryker-Howmedica) using radiostereometric analysis (RSA). Between February 1996 and February 2000, 43 consecutive patients (mean age 53 (41-63) years, 23 women) with hip osteoarthrosis received an uncemented and hydroxyapatite-coated prosthesis with an anteverted stem. All patients were operated in a standardized way by three experienced surgeons and they were randomized to partial (P) or full (F) weight bearing during the first 6 weeks after surgery. The patients in the partial weight bearing group were equipped with a pressuresensitive insole signaling when their load exceeded the prescribed weight limit. RESULTS: At 3-month follow-up, the mean proximal (+)/ distal (-) migration of the stem was -0.14 mm (-1.93- 0.11) in group P and -0.31 mm (-4.30-0.16) in group F (p=0.6). At 1-year follow-up, the mean migration was -0.17 mm (-2.18-0.21) and -0.28 mm (-4.31-0.11), respectively (p=0.9). There was no significant difference in stem rotations either (p<0.2). The cup translations, rotations, and femoral head penetration were similar in the two groups (p<0.1). There were no re-operations during the first year. INTERPRETATION: We did not find any adverse effect of full weight bearing immediately after operation, which justifies use of this regimen after uncemented total hip arthroplasty of the ABG type.

Acetabular revision with impacted morselized cancellous bone graft and a cemented cup in patients with rheumatoid arthritis: three to fourteen-year follow-up.

BACKGROUND: Acetabular revision in patients with rheumatoid arthritis is often difficult because of the poor quality and quantity of the acetabular bone stock. The purpose of this study was to evaluate the midterm clinical and radiographic outcomes of acetabular revision with use of an impaction bone-grafting technique and a cemented polyethylene cup. METHODS: Thirty-five consecutive acetabular revisions were performed with impaction bone-grafting and use of a cemented cup in twenty-eight patients with rheumatoid arthritis. The average age at the revision was fifty-seven years. The minimum duration of follow-up of all reconstructions that were still functioning or that were followed until the time of death was three years (mean, 7.5 years; range, three to fourteen years). No patient was lost to follow-up, but five patients (six hips) died before the time of the review. The acetabular bone defects were classified as cavitary in twelve hips and as combined segmental-cavitary in twenty-three. RESULTS: The five patients (six hips) who died had been doing well at the time of their latest follow-up. Of the remaining patients, six (six hips) had a repeat revision. The average Harris hip score of the living patients with a surviving implant at the time of follow-up was 82 points, and there was no or only mild pain in twenty-one of the twenty-three hips. Radiographic analysis of all twenty-nine hips that had not been revised showed loosening in one hip and a nonprogressive radiolucent line in one zone in two others. Kaplan-Meier analysis demonstrated a prosthetic survival rate, with aseptic loosening as the end point, of 90% at eight years. CONCLUSION: Acetabular revision with impaction bone-grafting and a cemented cup in patients with rheumatoid arthritis had acceptable results at an average of 7.5 years postoperatively.

The precision of radiostereometric measurements. Manual vs. digital measurements.

The precision of digital vs. manual radiostereometric measurements in total hip arthroplasty was evaluated using repeated stereoradiographic exposures with an interval of 10-15 min. Ten Lubinus SP2 stems cemented into bone specimens and 12 patients with the same stem design were used to evaluate the precision of stem translations and rotations. The precision of translations and rotations of the cup and femoral head penetration was studied in 12 patients with whole polyethylene cups. The use of a measurement method based on digitised radiographs improved the precision for some of the motion parameters, whereas many of them did not change. A corresponding pattern was observed for both the intra- and interobserver error. Of the wear parameters, the most pronounced improvements were the 3D wear and in the proximal-distal direction, although the anterior-posterior precision was also improved. The mean errors of rigid body and elliptic fitting decreased in all evaluations but one, consistent with a more reproducible identification of the markers centres and the edge of the femoral head. Increased precision of radiostereometric measurements may be used to increase the statistical power of future randomised studies and to study new fields in orthopaedics requiring higher precision than has been available with RSA based on manual measurements.