Patient characteristics differently affect early cup and stem loosening in THA: a case-control study on 7,535 patients

We postulated that certain patient characteristics have different effects on early THA component loosening. With two matched case-control studies we assessed 3,028 cups and 5,224 stems. Loosening was defined using signs of mechanical component failure on routine follow-up radiographs or revision for aseptic loosening. Women and men had similar cup-loosening odds, but women had lower odds for stem loosening (p < 0.0001). Odds for cup loosening decreased by 2.1% per additional year of age (p = 0.0004), those for stem loosening by 2.4% (p < 0.0001). Each additional kilogram of weight decreased cup loosening odds by 1.3% (p = 0.0051). Each additional unit of BMI increased stem loosening odds (p = 0.0109). Charnley classes B and C were protective factors against loosening of both components. There were no risk differences for the various main diagnoses. Certain patient characteristics differently affected early cup and stem loosening, although some characteristics had the same protective or harmful effect on component survival.     

Medium-term results of the Charnley low-offset femoral stem

A reduced femoral offset in total hip replacement has been thought to be disadvantageous. We reviewed the results of 54 consecutive primary total hip replacements in 49 patients (mean age of 68 years) performed between August 1990 and December 1994, with a mean follow-up of 8.8 years (sd 2.1). The mean pre-operative femoral offset for these hips was 41 mm (sd 7.4). All patients received a low-offset Charnley stem and a polyethylene cup inserted by a single surgeon. At their latest follow-up, surviving patients had a significant improvement in the performance of their hip. Three had undergone revision, one each for deep infection, recurrent dislocation and late pain with subluxation. No hips had been revised, or were at risk of revision, for aseptic loosening. The mean annual linear rate of wear was 0.2 mm (sd 0.08) for the whole group. There was no correlation between the pre-operative femoral offset and the post-operative rate of wear. Our survivorship estimate was 91% when revision for any reason was taken as an end-point, but 100% if aseptic loosening was considered as the end-point. Our study demonstrates that a low-offset femoral stem can produce good, medium-term results.     

18 years of results with cemented primary hip prostheses in the Norwegian Arthroplasty Register: Concerns about some newer implants

Background and purpose Few studies have compared the long-term survival of cemented primary total hip arthroplasties (THAs), and several prostheses have been used without adequate knowledge of their endurance. We studied long-term outcome based on data in the Norwegian Arthroplasty Register.Patients and methods The 10 most used prosthesis brands in 62,305 primary Palacos or Simplex cemented THAs reported to the Register from 1987 through 2007 were included. Survival analyses with revision as endpoint (for any cause or for aseptic loosening) were performed using Kaplan-Meier and multiple Cox regression with time-dependent covariates. Revision rate ratios (RRs) were estimated for the follow-up intervals: 0–5, 6–10, and > 10 years.Results 5 prosthesis brands (cup/stem combinations) (Charnley, Exeter, Titan, Spectron/ITH, Link IP/Lubinus SP; n = 24,728) were investigated with 0–20 year follow-up (inserted 1987–1997). After 18 years, 11% (95% CI: 10.6–12.1) were revised for any cause and 8.4% (7.7–9.1) for aseptic loosening. Beyond 10 years of follow-up, the Charnley cup had a lower revision rate due to aseptic loosening than Exeter (RR = 1.8) and Spectron (RR = 2.4) cups. For stems, beyond 10 years we did not find statistically significant differences comparing Charnley with Titan, ITH, and SP stems, but the Exeter stem had better results (RR = 0.5). 10 prosthesis brands (9 cups in combination with 6 stems; n = 37,577) were investigated with 0–10 years of follow-up (inserted from 1998 through 2007). The Charnley cup had a lower revision rate due to aseptic loosening than all cups except the IP. Beyond 5 years follow-up, the Reflection All-Poly cup had a 14 times higher revision rate. For stems, beyond 5 years the Spectron-EF (RR = 6.1) and Titan (RR = 5.5) stems had higher revision rates due to aseptic loosening than Charnley. The analyses also showed a marked improvement in Charnley results between the periods 1987–1997 and 1998–2007.Interpretation We observed clinically important differences between cemented prosthesis brands and identified inferior results for previously largely undocumented prostheses, including the commonly used prosthesis combination Reflection All-Poly/Spectron-EF. The results were, however, satisfactory according to international standards.     

Outcome in design-specific comparisons between highly crosslinked and conventional polyethylene in total hip arthroplasty

Background and purpose — Most registry studies regarding highly crosslinked polyethylene (XLPE) have focused on the overall revision risk. We compared the risk of cup and/or liner revision for specific cup and liner designs made of either XLPE or conventional polyethylene (CPE), regarding revision for any reason and revision due to aseptic loosening and/or osteolysis.

Patients and methods — Using the Nordic Arthroplasty Register Association (NARA) database, we identified cup and liner designs where either XLPE or CPE had been used in more than 500 THAs performed for primary hip osteoarthritis. We assessed risk of revision for any reason and for aseptic loosening using Cox regression adjusted for age, sex, femoral head material and size, surgical approach, stem fixation, and presence of hydroxyapatite coating (uncemented cups).

Results — The CPE version of the ZCA cup had a risk of revision for any reason similar to that of the XLPE version (p = 0.09), but showed a 6-fold higher risk of revision for aseptic loosening (p < 0.001). The CPE version of the Reflection All Poly cup had an 8-fold elevated risk of revision for any reason (p < 0.001) and a 5-fold increased risk of revision for aseptic loosening (p < 0.001). The Charnley Elite Ogee/Marathon cup and the Trilogy cup did not show such differences.

Interpretation — Whether XLPE has any advantage over CPE regarding revision risk may depend on the properties of the polyethylene materials being compared, as well as the respective cup designs, fixation type, and follow-up times. Further research is needed to elucidate how cup design factors interact with polyethylene type to affect the risk of revision.     

Medium-term result of Elite Plus hip arthroplasty: the second modular evolution of the original Charnley low-friction arthroplasty

BackgroundThe Elite Plus total hip arthroplasty (THA) system was introduced as the second modular evolution of the original Charnley low-friction arthroplasty. However, the results of the Elite Plus THA are currently considered to be inconsistent. The aim of this study was to clarify the medium-term results and the factors affecting the results of Elite Plus THA.MethodsThe results of 97 Elite Plus THAs in 87 patients at 5 years or more postoperatively were reviewed. The patients’ mean age was 65 years, and follow-up averaged 8.0 years. The Elite Plus stem was used in all hips, and three designs of socket, Hylamer Ogee in 40 hips, Wroblewski Offset Bore in 38, and Charnley Ogee in 19, were implanted. The survival rates with loosening and revision as endpoints were analyzed. To clarify the risk factors affecting the survival rates, Charnley’s functional classification, Bombelli’s classification, Crowe’s classification, structural bone grafting of the acetabulum, cup design, stem position, and grading of the cement mantle were evaluated.ResultsThe stem survival rate with aseptic loosening as the endpoint was 96 %, and the rate with revision was 100 %. The cup survival rate with aseptic loosening as the endpoint was 80 %, and the rate with revision was 93 %. Using a Cox proportional hazards model, cup design was a potential confounding factor for acetabular loosening (p = 0.001). The loosening rates were 31 % for Hylamer Ogee sockets at 9.4 years, 8 % for Wroblewski Offset Bore sockets at 7.4 years, and 0 % for Charnley Ogee sockets at 5.6 years. No factors were significantly related to acetabular revision and femoral loosening.ConclusionsThe results of Elite Plus stem THA were excellent in the medium term. The cup design was a potential confounding factor for acetabular loosening, and the Hylamer Ogee socket was associated with a poor result.     

The performance of two hydroxyapatite-coated acetabular cups compared with Charnley cups. From the Norwegian Arthroplasty Register

We have compared the survival of two hydroxyapatite (HA)-coated cups, 1208 Atoll hemispheric and 2641 Tropic threaded, with cemented Charnley all-polyethylene cups (16 021) using the Cox regression model. The Tropic cup used in combination with an alumina ceramic femoral head, had good results, similar to those of the Charnley cup. When used in combination with a stainless-steel head, however, the risk of revision beyond four years was increased 3.4 times for the Tropic cup compared with the Charnley cup (p < 0.001). Over the same period, the Atoll cup had an increased risk of revision of 3.8 times when used with the alumina heads (p < 0.001) and an increased risk of 6.1 times when used with stainless-steel heads (p < 0.001). Revision because of wear and osteolysis was more common with both types of HA-coated cup than with the Charnley cup. The rate of revision of the Atoll cup because of aseptic loosening was also increased. We found that HA-coated cups did not perform better than the Charnley cup.     

Wear and periprosthetic osteolysis of modular, hemispheric acetabular cups]

Osteolysis associated with polyethylene wear has become one of the most prevalent complications associated with uncemented modular, hemispherical cups. Sixty-five consecutive total hip arthroplasties (ABG i, Howmedica, Stryker) were followed 6-12 years. Cumulative survivorship for the cup was 55.7% after 10 years. There were 20 cups revisions because of polyethylene wear and periprosthetic osteolysis (14 cups) or cup loosening (6 cups). Stability was assessed intraoperatively, 14 cups were revised, whereas 6 new polyethylene cups were cemented into stable metal-back of acetabular component. The average annual wear of revised cups was 0.32 mm. The annual wear of not revised cups was 0.12 mm. The differences were statistically significant (p = 0.002). The mean area of osteolysis was 472 mm2 (SD 257 mm2). There was no significant correlation between wear and area of osteolysis. There was significant correlation R = 0.54, p = 0.014) between time to revision and area of osteolysis. There were no significant differences of wear of polyethylene inlay or area of osteolysis between stable and unstable acetabular cups.     

Long-Term Survival of the Cemented Exeter Universal Stem in Patients 50 Years and Younger: An Update on 130 Hips

BackgroundThere is variable evidence regarding survivorship beyond 20 years of total hip arthroplasties in young patients. We report the long-term results of the Exeter cemented hip system in patients ≤50 years at minimum of 20 years.MethodsClinical and radiological outcomes of 130 consecutive total hip arthroplasties in 107 patients aged 50 years or younger at primary operation were reviewed; 77% had a diagnosis other than osteoarthritis. All patients were followed at 5-year intervals, no patients were lost to follow-up, and the status of every implant is known.ResultsMean age at surgery was 41.8 (17-50) years. Mean follow-up was 22.0 (20.0-26.1) years. There were 79 hips surviving, 14 hips (11 patients) deceased, and 37 hips revised. Reasons for revision: 29 hips for aseptic cup loosening (26 stems revised using cement-in-cement, three left in-situ); three stems for femoral osteolysis, two related to acetabular polyethylene wear (14.1 and 17.0 years), one with Gaucher’s disease (21.1 years); one broken stem (12.9 years); one cup for instability (4.3 years–stem revised using cement-in-cement); and two hips with infection (8.5 and 23.8 years). There were no cases of aseptic loosening of the Exeter stem. There were no radiologically loose stems although eight patients had radiological evidence of loosening of the cemented cup. Survivorship at 22 years was 74.9% for revision for all causes and 96.3% for revision of the stem for aseptic loosening or lysis.ConclusionThe Exeter cemented stem has excellent survivorship at minimum 20 years in young patients. Acetabular component survivorship was less favorable, but the advent of highly cross-linked polyethylene may improve this in the long term.     

Effect of reduced diameter neck stem on incidence of radiographic cup loosening and revisions in Charnley low-frictional torque arthroplasty

Previous studies of the Charnley low-frictional torque arthroplasty have established an exponential correlation between the depth of cup penetration and the incidence of ultrahigh molecular weight polyethylene cemented cup migration. Impingement of the neck of the stem on the rim of the cup was considered to be the cause. We compared the incidence of radiographic loosening and revision of the cup in 2 groups of patients: those with 12.5-mm-diameter neck stem (972 hips) and those with 10-mm-diameter neck stem (261 hips) over a 20-year period, at comparable depths of cup penetration. The benefit of the 10-mm-diameter neck could be expressed as delaying radiographic loosening and revision of the cup by approximately 2 mm of cup penetration because loosening occurred at 2 mm penetration with a 12.5-mm-diameter neck but not until 4-mm penetration with a 10-mm-diameter neck. When a particular depth of cup penetration is reached will clearly depend on factors affecting wear.     

The Charnley versus the Spectron hip prosthesis: clinical evaluation of a randomized, prospective study of 2 different hip implants.

Prospective, randomized studies must be performed when new surgical techniques or implants are evaluated. In this study, a new implant system was compared with the Charnley prosthesis, which over the years has been the most used hip implant in Sweden. Between 1985 and 1989, 410 hips were randomized to treatment with a Charnley or a Spectron total hip arthroplasty: 206 Charnley and 204 Spectron prostheses were implanted. The patients were operated on by a standardized procedure using a contemporary cementing technique. The patients were followed prospectively by an independent observer after 1, 3, 5 to 6, and 10 years. Harris Hip Score and patient satisfaction were recorded in the outcome evaluation. A total of 144 patients with 164 hips were deceased, and 15 patients (8 Charnley and 7 Spectron) have required a revision. Nine hips were revised because of aseptic loosening (5 Charnley stems and 4 Spectron metal-backed cups). The Charnley stem as well as the metal-backed Spectron cup had a higher risk for revision because of aseptic loosening. The Charnley ogee cup and the Spectron stem have performed remarkably well with no revision of these components. Seven Charnley prostheses dislocated, but no dislocation was recorded in the Spectron group. Survivorship calculations with a mean follow-up of 10 years revealed an overall 11-year survivorship of 94.5% +/- 3.4% (Charnley, 93.2% +/- 5.8%; Spectron, 95.9% +/- 3.0%). The clinical outcome did not differ between the 2 systems. The overall results in this old population, using a contemporary surgical technique, illustrate that cemented hip arthroplasty is an excellent treatment alternative for elderly patients.     

Fracture of the hip after knee arthroplasty--an unusual case with pain in the knee

Background?The long-term results of uncemented total hip arthroplasties vary widely due to differences in design, metal alloy, coating, surface structure, and porosity.

Patients and methods?We retrospectively studied 75 cementless Zweymüller SL stems in combination with Endler titanium-backed threaded cups (Z-E) in 70 patients. 35 patients were women, and the mean age at surgery was 52 (24–68) years. 16 patients died and 1 emigrated, 7 patients (of which 1 later died) subsequently underwent revision, and the remaining 47 patients with 50 original arthroplasties were followed up after a median of 16 (15–18) years.

Results?Revision of 8 hips resulted in an 18-year Kaplan-Meier estimated overall survival rate of 88% (CI: 79–96). 6 of 7 cup revisions were due to liner wear and osteolysis, and 1 was due to aseptic loosening. 2 of 3 stem revisions were due to femoral loosening and 1 was due to fracture of the neck of the stem. The clinical results were good, with a mean Harris hip score of 89 (54–100). Half of 70 hips in 65 patients had ectopic bone formation. All unrevised implants were radiographically stable, with a mean liner wear of 0.07 mm/year.

Interpretation?These long-term results demonstrate that the combination of a Zweymüller SL stem and an Endler titanium-backed screw cup is a good hip arthroplasty in young and active patients. A prefixed polyethylene liner is a drawback, necessitating exchange of the whole cup in cases with polyethylene wear.     

Cementless total hip arthroplasty with a close proximal fit and short tapered distal stem (third-generation) prosthesis

This study presents the results of a prospective, consecutive series of 50 patients (60 hips) who were observed for a minimum of 6 years after they had a primary total hip arthroplasty with a cementless Duraloc 100 series cup (DePuy, Warsaw, IN) with a close proximal fit and short tapered distal stem prosthesis (IPS hip; DePuy, Leeds, UK). There were 37 men and 13 women; the mean age was 46.6 years (range, 26 to 70 years). The mean follow-up was 6.3 years (range, 6 to 7 years). The mean preoperative Harris hip score was 42 points, which improved to 96 points at the final follow-up examination. The prevalence of transitory thigh pain was 2%. All hips had a satisfactory fit of the femoral stem in coronal (average, 88%) and sagittal (average, 94%) planes. There was no aseptic loosening or revision of the components. The wear rate per year was 0.23 mm. Four hips (7%) had osteolysis in the calcar femorale <1 cm in diameter. Although there was no aseptic loosening of the components, a low incidence of osteolysis, and a low incidence of thigh pain, a high rate of polyethylene liner wear in these young patients is a problem.     

Long-term survivorship of the Charnley Elite Plus femoral component in young patients

We studied prospectively the long-term results of the Charnley Elite-Plus femoral stem in 184 consecutive young patients (194 hips). There were 130 men and 54 women with a mean age of 49.1 years (21 to 60). The predominant diagnosis was osteonecrosis of the femoral head (63.6%, 117 patients). Clinical and radiological evaluation was undertaken at each follow-up. The mean follow-up was 11.2 years (10 to 12). The mean pre-operative Harris hip score was 43.4 (12 to 49) which improved to 91 (59 to 100) at the final follow-up. The survival of the femoral stem at 12 years was 99% with revision as the end-point. The mean annual linear wear of the polyethylene liner was 0.17 mm (0.13 to 0.22). The prevalence of acetabular osteolysis was 10.8% (21 hips) and osteolysis of the calcar femorale 12.9% (25 hips). A third-generation cementing technique, accurate alignment of the stem and the use of a 22 mm zirconia head were important factors in the prevention of aseptic loosening of the Elite Plus femoral stem in these high-risk young patients.     

Acetabular reconstruction with impaction bone-grafting and a cemented cup in patients younger than fifty years old: a concise follow-up, at twenty to twenty-eight years, of a previous report

In a previous report, we presented our results of forty-two acetabular reconstructions, performed with use of impaction bone-grafting and a cemented polyethylene cup, in thirty-seven patients who were younger than fifty years and had a minimum of fifteen years of follow-up. The present update study shows the results after twenty to twenty-eight years. Eight additional cups had to be revised--four because of aseptic loosening, three because of wear, and one during a revision of the stem. Three additional cups were considered loose on radiographs. Survivorship of the acetabular reconstructions, with an end point of revision for any reason, was 73% after twenty years and 52% after twenty-five years. With revision for aseptic loosening as the end point, survival was 85% after twenty years and 77% after twenty-five years; for signs of loosening on radiographs, survival was 71% at twenty years and 62% at twenty-five years. In conclusion, our previous results have declined but the technique of using impacted morselized bone graft and a cemented cup is useful for the purpose of restoring bone stock in young patients whose acetabular defects require primary or revision total hip arthroplasty.     

Long-term follow-up of a hydroxyapatite ceramic-coated threaded cup: an analysis of survival and fixation at up to 15 years

We evaluated the survival of 112 consecutive JRI hydroxyapatite ceramic-coated threaded acetabular components (JRI Ltd, London, UK). Follow-up was for a minimum of 13 years (range, 13-15 years). Patients were assessed clinically and radiographically using the Merle d'Aubigné and Postel scoring systems and the De Lee and Charnley zones. Cup angle, migration, and signs of radiolucency were used to assess loosening. The criteria for failure were revision or impending revision due to pain and septic or aseptic loosening. The mean results of the Merle d'Aubigné and Postel score for pain, motion, and ability to walk were 2.2/2.7/2.2 preoperatively and 5.6/4.3/5.1 postoperatively. There was 100% endosteal bone formation in De Lee and Charnley zones 1 and 3 and 87% in zone 2. No reactive lines were seen in any zone in any cup. There were no cases of migration, change in cup angle, or revision for loosening. Our survival was 99% at 13 years (95% confidence interval, 96-100).     

Wear of the acetabular socket. Comparison of polyacetal and polyethylene

Frictional characteristics of polyacetal (Delrin) sockets and of ultra-high molecular weight polyethylene sockets retrieved in revision after aseptic loosening were compared with measurements of friction in new sockets. Friction in retrieved polyacetal sockets was twice as great as in retrieved polyethylene sockets. We also found that frictional characteristics of polyacetal changed as the material aged in vivo. In contrast, friction in polyethylene sockets remained fairly constant, even though most of them contained bone-cement particles. Friction in polyacetal sockets may be important for the relatively high incidence of socket loosening of the Christiansen prosthesis. Measurements of wear of the polyacetal sockets showed a mean annual dimensional change of 240 mm3, four times greater than that reported for the Charnley polyethylene acetabular prosthesis.     

Results of cemented metal-backed acetabular components: A 10-year-average follow-up study

The clinical and radiographic results of 86 primary total hip arthroplasties performed in 74 patients from 1983 to 1987 with a cemented metal-backed acetabular component and a cemented collared straight femoral stem with a 32-mm head were reviewed at a mean follow-up of 10.1 years. Seven patients (9.2%) underwent acetabular component revision at a mean of 9.0 years after implantation; an additional 24 components (31.6%) demonstrated evidence of radiographic loosening, resulting in a total failure rate of 40.8%. Periacetabular radiolucencies were noted in Charnley zones at the following rates: 34.2% in zone I, 18.4% in zone II, and 27.6% in zone III. In addition, 18.4% and 38.2% of implants demonstrated evidence of migration and excessive polyethylene wear. Excessively vertical cup placement (>49° inclination) at the time of initial arthroplasty was statistically correlated with polyethylene wear, implant migration, and fixation failure. A trend of increasing implant failure was also noted with decreasing polyethylene liner thickness. Periacetabular cement mantle thickness was not statistically correlated with subsequent component loosening or failure. Results of Kaplan-Meier survivorship analysis using revision as an endpoint showed 93.6% survivorship at 10 years and 88.4% at 12 years. The mean modified Harris hip scores were 46.9 preoperatively and 81.8 at final follow-up. The significant overall rates of radiographic loosening, migration, polyethylene wear, and implant revision confirm the suspected trend of increasing failure rates of cemented metal-backed acetabular components over time.     

Migration of the Duraloc cup after 5 years

The Duraloc cup is a frequently used metal-backed, porous-coated, hemispherical, press-fit acetabular component. Published data on loosening rates are contradictory. In this study we investigated migration patterns with computer-assisted Einzel-Bild-Roentgen-Analyse (EBRA) of 67 Duraloc 100 cups. Cup migration and clinical scores were analysed over a 5-year follow-up period. Median total migration of the Duraloc 100 cup was 1.21 mm at 5 years. Seventy-five percent of implants were radiologically stable at 2 years and 90% at 4 years. One cup loosened aseptically at 60 months, requiring revision. Cup diameters > or = 54 mm migrated significantly more than cups < 54 mm in diameter (p = 0.029 at 4 years). There was a significant correlation between high polyethylene wear and further migrating cups within the first post-operative year (p = 0.035 at 12 months). Our analysis revealed significantly higher wear in males (p = 0.029 at 4 years). Radiological loosening at two years could be calculated using receiver-operating characteristic curve analysis, and 1.2 mm as an adequate threshold value (sensitivity = 100%, specificity = 89%).     

Eight-year results of hydroxyapatite-coated hip arthroplasty

Ninety hips in 82 patients using Omnifit hydroxyapatite (HA)-coated prosthesis were followed for at least 7 years. All stems were stable at the final follow-up. However, aseptic loosening was found in 8 cups and 6 of them were revised. Two polyethylene wear were treated with inserts exchanged. The mechanical failure rate was 11.4% and the combined failure rate was 14.3% for HA-coated cup. Four other cups with wear and osteolysis without loosening or pain and 2 cups with polyethylene wear without osteolysis were still under observation. Our findings suggest that hip arthroplasties with HA coating on the smooth surface of a titanium cup is not reliable. The mid-term result of HA-coated stem is as good as that of porous-coated stem.