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1.  Increased risk of revision of acetabular cups coated with hydroxyapatite 
Acta Orthopaedica  2010;81(1):53-59.
Background
Hydroxyapatite (HA) is the main inorganic component of bone, and HA coating is widely used on acetabular cups in hip arthroplasty. It has been suggested that this surface finish improves cup survival.
Methods
All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 with an uncemented acetabular implant that was available either with or without HA coating were identified. 8,043 total hip arthroplasties (THAs) with the most common cup types (Harris-Galante, Romanus, and Trilogy) were investigated. A Cox regression model including type of coating, age, sex, primary diagnosis, cup type, and type of stem fixation was used to calculate adjusted risk ratios (RRs) for the risk of revision.
Results
HA coating was a risk factor for cup revision due to aseptic loosening (adjusted RR 1.7; 95% CI: 1.3–2). Age at primary arthroplasty of < 50 years, a diagnosis of pediatric hip disease, the use of a cemented stem, and the Romanus and Harris-Galante cup types were also associated with statistically significantly increased risk of cup revision due to aseptic loosening.
Interpretation
Our findings question the routine use of HA-coated cups in primary total hip arthroplasty. With some designs, this practice may even increase the risk of loosening—resulting in revision surgery.
doi:10.3109/17453670903413178
PMCID: PMC2856204  PMID: 19968603
2.  Dual-mobility cups for revision due to instability are associated with a low rate of re-revisions due to dislocation 
Acta Orthopaedica  2012;83(6):566-571.
Background and purpose
Revision total hip arthroplasty (THA) due to recurrent dislocations is associated with a high risk of persistent instability. We hypothesized that the use of dual-mobility cups would reduce the risk of re-revision due to dislocation after revision THA.
Patients and methods
228 THA cup revisions (in 228 patients) performed due to recurrent dislocations and employing a specific dual-mobility cup (Avantage) were identified in the Swedish Hip Arthroplasty Register. Kaplan-Meier survival analysis was performed with re-revision due to dislocation as the primary endpoint and re-revision for any reason as the secondary endpoint. Cox regression models were fitted in order to calculate the influence of various covariates on the risk of re-revision.
Results
58 patients (25%) had been revised at least once prior to the index cup revision. The surgical approach at the index cup revision was lateral in 99 cases (44%) and posterior in 124 cases (56%). Median follow-up was 2 (0–6) years after the index cup revision, and by then 18 patients (8%) had been re-revised for any reason. Of these, 4 patients (2%) had been re-revised due to dislocation. Survival after 2 years with the endpoint revision of any component due to dislocation was 99% (95% CI: 97–100), and it was 93% (CI: 90–97) with the endpoint revision of any component for any reason. Risk factors for subsequent re-revision for any reason were age between 50–59 years at the time of the index cup revision (risk ratio (RR) = 5 when compared with age > 75, CI: 1–23) and previous revision surgery to the relevant joint (RR = 1.7 per previous revision, CI: 1–3).
Interpretation
The risk of re-revision due to dislocation after insertion of dual-mobility cups during revision THA performed for recurrent dislocations appears to be low in the short term. Since most dislocations occur early after revision THA, we believe that this device adequately addresses the problem of recurrent instability. Younger age and prior hip revision surgery are risk factors for further revision surgery. However, problems such as potentially increased liner wear and subsequent aseptic loosening may be associated with the use of such devices in the long term.
doi:10.3109/17453674.2012.742395
PMCID: PMC3555442  PMID: 23116439
3.  Uncemented and cemented primary total hip arthroplasty in the Swedish Hip Arthroplasty Register 
Acta Orthopaedica  2010;81(1):34-41.
Background and purpose
Since the introduction of total hip arthroplasty (THA) in Sweden, both components have most commonly been cemented. A decade ago the frequency of uncemented fixation started to increase, and this change in practice has continued. We therefore analyzed implant survival of cemented and uncemented THA, and whether the modes of failure differ between the two methods of fixation.
Patients and methods
All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 who received either totally cemented or totally uncemented THA were identified (n = 170,413). Kaplan-Meier survival analysis with revision of any component, and for any reason, as the endpoints was performed. Cox regression models were used to calculate risk ratios (RRs) for revision for various reasons, adjusted for sex, age, and primary diagnosis.
Results
Revision-free 10-year survival of uncemented THA was lower than that of cemented THA (85% vs. 94%, p < 0.001). No age or diagnosis groups benefited from the use of uncemented fixation. Cox regression analysis confirmed that uncemented THA had a higher risk of revision for any reason (RR = 1.5, 95% CI: 1.4–1.6) and for aseptic loosening (RR = 1.5, CI: 1.3–1.6). Uncemented cup components had a higher risk of cup revision due to aseptic loosening (RR = 1.8, CI: 1.6–2.0), whereas uncemented stem components had a lower risk of stem revision due to aseptic loosening (RR = 0.4, CI: 0.3–0.5) when compared to cemented components. Uncemented stems were more frequently revised due to periprosthetic fracture during the first 2 postoperative years than cemented stems (RR = 8, CI: 5–14). The 5 most common uncemented cups had no increased risk of revision for any reason when compared with the 5 most commonly used cemented cups (RR = 0.9, CI: 0.6–1.1). There was no significant difference in the risk of revision due to infection between cemented and uncemented THA.
Interpretation
Survival of uncemented THA is inferior to that of cemented THA, and this appears to be mainly related to poorer performance of uncemented cups. Uncemented stems perform better than cemented stems; however, unrecognized intraoperative femoral fractures may be an important reason for early failure of uncemented stems. The risk of revision of the most common uncemented cup designs is similar to that of cemented cups, indicating that some of the problems with uncemented cup fixation may have been solved.
doi:10.3109/17453671003685400
PMCID: PMC2856202  PMID: 20180715
4.  Survival of uncemented acetabular monoblock cups 
Acta Orthopaedica  2012;83(3):214-219.
Background and purpose
Monoblock acetabular cups represent a subtype of uncemented cups with the polyethylene liner molded into a metal shell, thus eliminating—or at least minimizing—potential backside wear. We hypothesized that the use of mono​block cups could reduce the incidence of osteolysis and aseptic loosening, and thus improve survival compared to modular designs.
Patients and methods
We identified all 210 primary total hip arthroplasty (THA) procedures in the Swedish Hip Arthroplasty Register that used uncemented monoblock cups during the period 1999–2010. Kaplan-Meier and Cox regression analyses with adjustment for age, sex, and other variables were used to calculate survival rates and adjusted hazard ratios (HRs) of the revision risk for any reason. 1,130 modular cups, inserted during the same time period, were used as a control group.
Results
There was a nearly equal sex distribution in both groups. Median age at the index operation was 47 years in the monoblock group and 56 years in the control group (p < 0.001). The cumulative 5-year survival with any revision as the endpoint was 95% (95% CI: 91–98) for monoblock cups and 97% (CI: 96–98) for modular cups (p = 0.6). The adjusted HR for revision of monoblock cups compared to modular cups was 2 (CI: 0.8–6; p = 0.1). The use of 28-mm prosthesis heads rather than 22-mm heads reduced the risk of cup revision (HR = 0.2, CI: 0.1–0.5; p = 0.001).
Interpretation
Both cups showed good medium-term survival rates. There was no statistically significant difference in revision risk between the cup designs. Further review of the current patient population is warranted to determine the long-term durability and risk of revision of monoblock cup designs.
doi:10.3109/17453674.2012.688726
PMCID: PMC3369144  PMID: 22574820
5.  Ceramic-on-ceramic THA Associated With Fewer Dislocations and Less Muscle Degeneration by Preserving Muscle Progenitors 
Background
Dislocation is a common complication after total hip arthroplasty (THA). Although the etiology of dislocation is multifactorial, longer-term changes in muscle such as atrophy may influence the risk of prosthetic dislocation. Biological differences in wear products generated by different bearing surfaces may influence differences in the appearance of periarticular muscle after THA; however, such bearing-associated differences to our knowledge have not been studied in vivo, and few studies have evaluated bearing-associated differences in dislocation risk.
Questions/purposes
(1) Is there a correlation between the postoperative risk of dislocation at revision and the bearing surfaces of the primary arthroplasty? (2) Is there a higher extent of fatty muscle atrophy on CT scan in hips with osteolysis (polyethylene hips) as compared with hips without osteolysis (ceramic-on-ceramic hips)? (3) Are these two abnormalities (bone osteolysis and fatty atrophy) associated with a decrease of mesenchymal stem cells (MSCs) in bone and in muscle?
Methods
We retrospectively evaluated 240 patients (240 hips) who had a THA revision (98% of which, 235 of the 240, were isolated acetabular revisions) and a normal contralateral hip. All patients had received the same implants for the primary arthroplasty (32-mm head) except for bearing surfaces (80 hips with ceramic-on-ceramic, 160 with polyethylene). No differences were noted between the groups in terms of age, sex, body mass index, proportion of patients who had a dislocation after the index arthroplasty but before the revision, and proportion of the patients with stem loosening in addition to acetabular loosening. Indications for revision generally were cup loosening. The revisions in the hips with polyethylene bearings generally had more acetabular bone loss, but the position of the center of the cup and the orientation of the cup were similar after reconstruction in the two groups. Before revision, osteolysis, muscle atrophy, and fatty degeneration were evaluated on CT scan and compared with the contralateral side. Bone muscle progenitors were evaluated by bone marrow MSCs and satellite cells for muscle. At revision, all the hips received the same implants with the same head diameter (32 mm) and a standard liner. Revisions were performed between 1995 and 2005. The followup after revision was at a mean of 14 years (range, 10–20 years) for ceramic revision and 12 years (range, 10–20 years) for polyethylene hips, and there was no differential loss to followup between the groups.
Results
More hips with polyethylene liners at the time of index arthroplasty dislocated after revision than did hips with ceramic liners (18% [29 of 160] compared with 1% [one of 80]; odds ratio, 17.5; 95% confidence interval, 2.3363–130.9100; p = 0.005). For the 80 hips with ceramic-on-ceramic, no osteolysis was detected before revision; there was no muscle fatty degeneration of the gluteus muscles on CT scan or histology. For the 160 hips with polyethylene liners, osteolytic lesions on the acetabulum and femur were observed in 100% of the hips. The increased atrophy of the gluteus muscles observed on CT scan correlated with the increase of osteolysis (r = 0.62; p = 0.012). The surgical limbs in the patients with polyethylene hips as compared with ceramic-on-ceramic hips demonstrated a greater reduction in cross-sectional area (respectively, 11.6% compared with 3%; odds ratio, 3.82; p < 0.001) and radiological density (41% [14.1/34.1] compared with 9%; odds ratio, 6.8; p = 0.006) of gluteus muscles when compared with the contralateral normal side. (41% compared with 9%; odds ratio, 6.8; p = 0.006).
Conclusions
Ceramic bearing surfaces were associated with fewer dislocations after revision than polyethylene bearing surfaces. The reasons of the lower rate of dislocation with ceramic-on-ceramic bearings may be related to observed differences in the periarticular muscles (fat atrophy or not) with the two bearing surfaces.
Level of Evidence
Level III, therapeutic study.
doi:10.1007/s11999-015-4378-7
PMCID: PMC4626505  PMID: 26054482
6.  Method of Fixation Does Not Influence the Overall Risk of Rerevision in First-time Cup Revisions 
Background
During the last two decades, uncemented fixation has been increasingly preferred worldwide during cup revision surgery. In Sweden, the number of uncemented cup revisions has been increasing during the last decade. However, it is unclear whether the risk of rerevision differs between cemented and uncemented cups.
Question/purposes
We determined (1) the risk of rerevision after cemented and uncemented fixation; (2) the influence of concomitant stem revision on the risk of rerevision of the cup; (3) the difference in risk of rerevision of an uncemented cup revision compared with liner revision only; and (4) whether the surgical incision influenced the risk of rerevision.
Methods
Between 1979 and 2010, 19,342 first-time cup revisions were reported to the Swedish Hip Arthroplasty Register. From these, 749 were excluded (hip resurfacing, cases with tumor diagnoses, and missing data) leaving 18,593 (73% cemented) for further analysis. We used a Cox regression model adjusted for age, sex, primary diagnosis, method of fixation, concomitant stem revision, and cemented/uncemented fixation to assess risk of rerevision.
Results
The relative risk for rerevision for any reason did not differ between cemented and uncemented fixation (relative risk [RR], 0.94). If the stem was not revised at index revision, the risk of further cup revision increased twofold (RR, 1.91). Liner revisions were associated with a 70% increased risk for rerevision of the cup as a result of any reason and especially because of dislocation (RR, 2.94). The surgical incision did not influence the overall risk for rerevision (direct lateral/posterolateral: RR, 1.02) or the risk of rerevision resulting from dislocation (RR, 0.91).
Conclusions
We found no difference in the overall risk of rerevision between cemented and uncemented fixation. Liner exchange had a higher risk for rerevision when compared with cases being rerevised with a new uncemented cup.
Level of Evidence
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-2872-3
PMCID: PMC3825907  PMID: 23440618
7.  Outcomes of dual-mobility acetabular cup for instability in primary and revision total hip arthroplasty 
Background
The concept of a dual-mobility hip socket involves the standard femoral head component encased in a larger polyethylene liner, which in turn articulates inside a metal shell implanted in the native acetabulum. The aim of this study was to assess outcomes from using a Serf Novae® Dual Mobility Acetabular cup (Orthodynamics Ltd, Gloucestershire, UK) to address the problem of instability in primary and revision total hip arthroplasty (THA).
Materials and methods
A retrospective review was carried out of all hip arthroplasties performed in a District General Hospital utilising the dual-mobility socket from January 2007 to December 2012. Clinical and radiological outcomes were analysed for 44 hips in 41 patients, comprising 20 primary and 24 revision THA. The average age of the study group was 70.8 years (range 56–84 years) for primary and 76.4 years (range 56–89 years) for revision arthroplasty. Among the primary THA, always performed for hip osteoarthritis or in presence of osteoarthritic changes, the reasons to choose a dual mobility cup were central nervous system problems such as Parkinson’s disease, stroke, dementia (10), hip fracture (5), failed hip fracture fixation (2), severe fixed hip deformity (2) and diffuse peripheral neuropathy (1). The indications for revisions were recurrent dislocation (17), aseptic loosening with abductor deficiency (4), failed hemiarthroplasty with abductor deficiency (2) and neglected dislocation (1).
Results
At a mean follow-up of 22 months (range 6–63 months), none of the hips had any dislocation, instability or infection and no further surgical intervention was required. Radiological assessment showed that one uncemented socket in a revision arthroplasty performed for recurrent dislocation had changed position, but was stable in the new position. The patient did not have complications from this and did not need any surgical intervention.
Conclusions
Even though postoperative hip stability depends on several factors other than design-related ones, our study shows promising early results for reducing the risk of instability in this challenging group of patients undergoing primary and revision hip arthroplasty.
Level of evidence
IV.
doi:10.1007/s10195-014-0324-9
PMCID: PMC4348500  PMID: 25330736
Hip arthroplasty; Dislocation; Instability; Dual-mobility socket
8.  Outcomes of dual-mobility acetabular cup for instability in primary and revision total hip arthroplasty 
Background
The concept of a dual-mobility hip socket involves the standard femoral head component encased in a larger polyethylene liner, which in turn articulates inside a metal shell implanted in the native acetabulum. The aim of this study was to assess outcomes from using a Serf Novae® Dual Mobility Acetabular cup (Orthodynamics Ltd, Gloucestershire, UK) to address the problem of instability in primary and revision total hip arthroplasty (THA).
Materials and methods
A retrospective review was carried out of all hip arthroplasties performed in a District General Hospital utilising the dual-mobility socket from January 2007 to December 2012. Clinical and radiological outcomes were analysed for 44 hips in 41 patients, comprising 20 primary and 24 revision THA. The average age of the study group was 70.8 years (range 56–84 years) for primary and 76.4 years (range 56–89 years) for revision arthroplasty. Among the primary THA, always performed for hip osteoarthritis or in presence of osteoarthritic changes, the reasons to choose a dual mobility cup were central nervous system problems such as Parkinson’s disease, stroke, dementia (10), hip fracture (5), failed hip fracture fixation (2), severe fixed hip deformity (2) and diffuse peripheral neuropathy (1). The indications for revisions were recurrent dislocation (17), aseptic loosening with abductor deficiency (4), failed hemiarthroplasty with abductor deficiency (2) and neglected dislocation (1).
Results
At a mean follow-up of 22 months (range 6–63 months), none of the hips had any dislocation, instability or infection and no further surgical intervention was required. Radiological assessment showed that one uncemented socket in a revision arthroplasty performed for recurrent dislocation had changed position, but was stable in the new position. The patient did not have complications from this and did not need any surgical intervention.
Conclusions
Even though postoperative hip stability depends on several factors other than design-related ones, our study shows promising early results for reducing the risk of instability in this challenging group of patients undergoing primary and revision hip arthroplasty.
Level of evidence
IV.
doi:10.1007/s10195-014-0324-9
PMCID: PMC4348500  PMID: 25330736
Hip arthroplasty; Dislocation; Instability; Dual-mobility socket
9.  Effects of hydroxyapatite coating on survival of an uncemented femoral stem 
Acta Orthopaedica  2011;82(4):399-404.
Background and purpose
Hydroxyapatite (HA) is widely used as a coating for uncemented total hip arthroplasty components. This has been suggested to improve implant ingrowth and long-term stability. However, the evidence behind the use of HA coating on femoral stems is ambiguous. We investigated survival of an uncemented, tapered titanium femoral stem that was available either with or without HA coating (Bi-Metric).
Patients and methods
The stem had been used in 4,772 total hip arthroplasties (THAs) in 4,169 patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2009. 59% of the stems investigated were coated with HA and 41% were uncoated. Kaplan-Meier survival analysis and a Cox regression model with adjustment for age, sex, primary diagnosis, and the type of cup fixation were used to calculate survival rates and adjusted risk ratios (RRs) of the risk of revision for various reasons.
Results
The 10-year survival rates of the HA-coated version and the uncoated version were about equal when we used revision for any reason as the endpoint: 98% (95% CI: 98–99) and 98% (CI: 97–99), respectively. A Cox regression model adjusting for the covariates mentioned above showed that the presence of HA coating did not have any influence on the risk of stem revision for any reason (RR = 1.0, 95% CI: 0.6–1.6) or due to aseptic loosening (RR = 0.5, CI: 0.2–1.5). There was no effect of HA coating on the risk of stem revision due to infection, dislocation, or fracture.
Interpretation
The uncemented Bi-Metric stem showed excellent 10-year survival. Our findings do not support the use of HA coating on this stem to enhance implant survival.
doi:10.3109/17453674.2011.597699
PMCID: PMC3237027  PMID: 21751858
10.  Satisfying Results of Primary Hip Arthroplasty in Patients With Hip Dysplasia at a Mean Followup of 20 Years 
Background
Developmental dysplasia of the hip (DDH) is a common cause of secondary osteoarthritis (OA) in younger patients, and when end-stage OA develops, a THA can provide a solution. Different options have been developed to reconstruct these defects, one of which is impaction bone grafting combined with a cemented cup. To determine the true value of a specific technique, it is important to evaluate patients at a long-term followup. As there are no long-term studies, to our knowledge, on THA in patients with DDH using impaction bone grafting with a cemented cup, we present the results of this technique at a mean of 15 years in patients with previous DDH.
Questions/purposes
We wished to determine (1) the long-term probability of cup revision at a minimum followup of 15 years for cemented acetabular impaction bone grafting in patients with DDH; (2) the radiographic appearance of the bone graft and radiographic signs of implant loosening; and (3) the complications and pre- and postoperative Harris hip scores with cemented THA combined with impaction bone grafting in patients with previous DDH.
Methods
Between January 1984 and December 1995 we performed 28 acetabular impaction bone grafting procedures for secondary OA believed to be caused by DDH in 22 patients; four patients died before 15 years, leaving 24 hips in 18 patients for retrospective analysis at a minimum of 15 years (mean, 20 years; range, 16–29 years). The diagnosis of DDH was made according to preoperative radiographs and intraoperative findings. All grades of dysplasia were included; five patients had Crowe Group I, eight had Group II, nine had Group III, and two had Group IV DDH. No patients were lost to followup. In all cases the acetabular defects were combined cavitary and segmental. Owing to the high number of deaths, we performed a competing-risk analysis to determine the probability of cup revision surgery.
Results
The competing-risk analysis showed cumulative incidences at 15 and 20 years, with endpoint revision for any reason of 7% (95% CI, 0%–17%), whereas this was 4% (95% CI, 0%–11%) with endpoint revision of the cup for aseptic loosening. Three revision surgeries were performed. Two cup revisions were performed for aseptic loosening at 12 and 26 years. Another cup revision was performed owing to sciatic nerve problems at 2 years. A stable radiographic appearance of the graft was seen in 19 of the 25 unrevised hips. Four hips showed acetabular radiolucent lines and two showed acetabular osteolysis. None of the unrevised cups showed migration or radiographic failure. Postoperative complications included a pulmonary embolus and a superficial wound infection. The Harris hip score improved from 37 (range, 9–72) preoperatively to 83 (range, 42–99) at latest followup.
Conclusions
Cemented primary THA with the use of impaction bone grafting shows satisfying long-term results in patients with previous DDH. For future research it is important to evaluate this technique in a larger cohort with a long-term followup. Other techniques also should be evaluated at long-term followup to be able to compare different techniques in this important and specific patient group.
Level of Evidence
Level IV, therapeutic study.
doi:10.1007/s11999-016-4998-6
PMCID: PMC5052201  PMID: 27492686
11.  Does a Titanium-coated Polyethylene Press-fit Cup Give Reliable Midterm Results? 
Background
Uncemented acetabular components have demonstrated low revision rates and high patient satisfaction but with concerns regarding increased costs compared with monoblock cups. Some newer lower-cost uncemented monoblock options have become available in the last decade, but limited data are available on their performance.
Questions/purposes
(1) Does an uncemented, titanium-backed all-polyethylene acetabular cup provide reliable fixation? (2) What is the frequency and what are the causes for revision with this cup?
Methods
Between 2004 and 2008, we elected to use an uncemented, titanium-backed all-polyethylene acetabular cup in older patients with limited physical demands. We performed 615 hip replacements in 550 patients with greater than 5 years of clinical and radiographic followup. When patients who were dead (80 hips in 75 patients), lost to followup (98 hips in 93 patients), or revised (three hips in three patients) were excluded, there were 434 hips in 379 patients for comparison of the postoperative and 5-year radiographs. Two observers not involved in the index surgical procedures (NH, HS) assessed radiographs for signs of migration or loosening. Some degree of early movement sometimes is seen before cup stabilization; however, to be conservative, we defined cups with greater than 3° of change of position (even if they subsequently stabilized) as potentially at risk and report them separately. Revision surgery, time from the index procedure, and the reason for revision were recorded from the New Zealand Joint Registry.
Results
By 5 years there was a median change in inclination of 2° (range, 0°–13°; 95% confidence interval [CI], 2.0–2.4; p < 0.001) and 2° of anteversion (range, 0°–11°; 95% CI, 2.0–2.4; p < 0.001). Although at last followup all cups appeared to have stabilized with no radiolucent lines or medial migration, 22% of the cups (94 of 434) had moved more than 3° and so were deemed to be potentially at risk. There were 11 revision procedures (of 429 hips; 2.5%) of which six were for recurrent dislocation, four for femoral fracture, and one for femoral loosening to give an overall all-cause revision rate for all components of 0.25 per 100 component years (95% CI, 0.13–0.43). No revisions were performed for acetabular loosening.
Conclusions
The short- to medium-term results of this all-polyethylene monoblock cup demonstrated a low frequency of revision. However, 94 cups were identified as potentially at risk based on movement of > 3° before apparent stabilization. Although those patients seem to be doing well enough now, the current duration of followup may not be sufficient to know that these cups will be durable, because other ongrowth designs have demonstrated a high frequency of late failure after apparent early success.
Level of Evidence
Level IV, therapeutic study.
doi:10.1007/s11999-015-4556-7
PMCID: PMC4626495  PMID: 26373851
12.  Cemented Polyethylene Cups in Patients Younger Than 40 Years 
Although uncemented cup implants frequently are used in young patients, we believe long-term survival rates of cups in these patients are somewhat disappointing, and therefore we have continued to use cemented cups in primary THA, even in young patients. However, in cases of acetabular bone stock defects, we also use bone impaction grafting. We prospectively followed 130 patients with 175 cemented cups; no patients were lost to followup. The mean age of the patients at surgery was 31 years (range, 16–39 years). An acetabular reconstruction with bone impaction grafting was performed in 84 hips (48%). The minimum followup was 2 years (average, 8.1 years; range, 2.0–18.5 years). Twenty-one of the 175 cups (12%) were revised at an average of 8.1 years (range, 2.0–18.5 years). Reasons for revision were infection (one early, seven late), recurrent dislocations (two), traumatic loosening (one), and aseptic loosening (10). The 10-year survival rate of all cemented cups with end point of revision for any cause was 85%. Survival with end point of aseptic loosening of all cups was 92%. Survival with end point of revision for aseptic loosening was 90% for the cups without impaction grafting and 95% for the cups with impaction grafting. We believe cemented acetabular cups in young patients have acceptable midterm survival; however, in the case of acetabular bone defects, we recommend reconstruction with impaction grafting.
Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-009-0837-3
PMCID: PMC2690764  PMID: 19370384
13.  Short-term survival of the trabecular metal cup is similar to that of standard cups used in acetabular revision surgery 
Acta Orthopaedica  2015;86(1):26-31.
Background and purpose
The use of trabecular metal (TM) cups in revision surgery has increased worldwide during the last decade. Since the introduction of the TM cup in Sweden in 2006, this design has gradually replaced other uncemented designs used in Sweden. According to data from the Swedish Hip Arthroplasty Register (SHAR) in 2012, one-third of all uncemented first-time cup revisions were performed using a TM cup. We compared the risk of reoperation and re-revision for TM cups and the 2 other most frequently used cup designs in acetabular revisions reported to the SHAR. The hypothesis was that the performance of TM cups is as good as that of established designs in the short term.
Patients and methods
The study population consisted of 2,384 patients who underwent 2,460 revisions during the period 2006 through 2012. The most commonly used cup designs were the press-fit porous-coated cup (n = 870), the trabecular metal cup (n = 805), and the cemented all-polyethylene cup (n = 785). 54% of the patients were female, and the median age at index revision was 72 (19–95) years. Reoperation was defined as a second surgical intervention, and re-revision—meaning exchange or removal of the cup—was used as endpoint. The mean follow-up time was 3.3 (0–7) years.
Results
There were 215 reoperations, 132 of which were re-revisions. The unadjusted and adjusted risk of reoperation or re-revision was not significantly different for the TM cup and the other 2 cup designs.
Interpretation
Our data support continued use of TM cups in acetabular revisions. Further follow-up is necessary to determine whether trabecular metal cups can reduce the re-revision rate in the long term, compared to the less costly porous press-fit and cemented designs.
doi:10.3109/17453674.2014.984114
PMCID: PMC4366676  PMID: 25399966
14.  Clinical and radiographic results and wear performance in different generations of a cementless porous-coated acetabular cup 
International Orthopaedics  2007;32(2):181-187.
We compared clinical results and wear performance in two different generations of a cementless porous-coated cup, analysing the long-term results of 83 uncemented Harris-Galante I cups (32-mm femoral head) and 93 uncemented Harris-Galante II cups (28-mm femoral head). All polyethylene liners were gamma irradiated in air. Polyethylene linear wear was estimated using a software package. The minimum follow-up was 10 years. Nine Harris-Galante I cups and two Harris-Galante II cups were revised due to aseptic loosening or polyethylene problems. The mean femoral head penetration at 6 weeks after surgery was 0.15 ± 0.05 mm for the Harris-Galante I cups and 0.12 ± 0.03 for the Harris-Galante II cups (p < 0.001);but mean wear was 0.13 ± 0.23 mm per year for the Harris-Galante I cups and 0.11 ± 0.10 for the Harris-Galante II cups (p = 0.740). Most of the metallic shells in both groups showed stable fixation. The so-called second-generation cups had lower initial polyethylene wear that resulted in less polyethylene wear at the latest the follow-up, but the overall wear rate was similar in both groups despite the different femoral head sizes and the improved locking mechanism.
doi:10.1007/s00264-006-0305-6
PMCID: PMC2269018  PMID: 17265157
15.  Isolated Polyethylene Exchange versus Acetabular Revision for Polyethylene Wear 
Polyethylene wear and osteolysis are not uncommon in THA mid- and long-term. In asymptomatic patients the dilemma faced by the orthopaedic surgeon is whether to revise the cup and risk damage to the supporting columns and even pelvic discontinuity or to perform isolated polyethylene exchange and risk a high rate of postoperative recurrent instability and dislocation that will necessitate further surgery. We retrospectively reviewed 62 patients (67 hips) who underwent revision arthroplasty for polywear and osteolysis. Thirty-six hips had isolated polyethylene exchange, while 31 had full acetabular revision. The minimum followup was 2 years (mean, 2.8 years; range, 2–5 years). Three of 36 hips with a retained cup grafted through the cup holes failed within 5 years due to acetabular loosening. One of 31 hips with full revision underwent re-revision for aseptic cup loosening at 5 months postoperatively. Although we do not recommend prophylactic revision of all cups for polywear and osteolysis, the patient may be warned of the possibility of an approximate 10% failure rate when retaining the acetabular component. We do, however, advocate cup extraction in the following situations: damage to the locking mechanism, erosion of the femoral head through the liner and into the cup damaging the metal, and a malpositioned component that may jeopardize the stability of the revision.
Level of Evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-008-0533-8
PMCID: PMC2600972  PMID: 18846409
16.  Long-term (20- to 25-year) Results of an Uncemented Tapered Titanium Femoral Component and Factors Affecting Survivorship 
Background
Uncemented femoral components in primary total hip arthroplasty (THA) are commonly used today, but few studies have evaluated their survival into the third decade.
Questions/purposes
We evaluated (1) survivorship using femoral revision for any reason as the end point; (2) survivorship using femoral revision for aseptic loosening as the end point; and (3) patient-related and surgical risk factors for aseptic stem loosening at a minimum 20-year followup with an uncemented tapered titanium stem.
Methods
We reviewed the clinical and radiographic results of 354 THAs in 326 patients performed between January 1985 and December 1989 using an uncemented grit-blasted, tapered titanium femoral stem. Mean age at surgery was 57 years (range, 13–81 years). Kaplan-Meier survivorship analysis was used to estimate long-term survival. Minimum followup evaluation was 20 years (mean, 22 years; range, 20–25 years); at that time, 120 patients (127 hips) had died, and four patients (five hips) were lost to followup. Multivariate survival analysis using a Cox regression model was performed.
Results
Survivorship at 22 years with revision of the femoral component for any reason as the end point was 86% (95% confidence interval [CI], 81%–90%). Survivorship for femoral revision for aseptic loosening as the end point was 93% at 22 years (95% CI, 90%–96%). Undersized stems (canal fill index ≤ 80%) and stems in hips with cup revision were at higher risk for aseptic loosening (hazard ratio, 4.2 and 4.3, respectively). There was a high rate of acetabular revision in this series (38%), mostly related to smooth-threaded, cementless sockets.
Conclusions
Uncemented femoral fixation was reliable into the third decade. Age, male sex, and diagnosis were not associated with a higher risk of aseptic loosening.
Level of Evidence
Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3033-4
PMCID: PMC3773148  PMID: 23670671
17.  Increased migration of uncemented acetabular cups in female total hip arthroplasty patients with low systemic bone mineral density 
Acta Orthopaedica  2015;87(1):48-54.
Background and purpose
Low bone mineral density (BMD) may jeopardize the initial component stability and delay osseointegration of uncemented acetabular cups in total hip arthroplasty (THA). We measured the migration of uncemented cups in women with low or normal BMD.
Patients and methods
We used radiostereometric analysis (RSA) to measure the migration of hydroxyapatite-coated titanium alloy cups with alumina-on-alumina bearings in THA of 34 female patients with a median age of 64 (41–78) years. 10 patients had normal BMD and 24 patients had low systemic BMD (T-score ≤ −1) based on dual-energy X-ray absorptiometry (DXA). Cup migration was followed with RSA for 2 years. Radiographic follow-up was done at a median of 8 (2–10) years.
Results
Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03). These differences in cup migration persisted at 24 months. Based on the perceived risk of cup revision, 14 of the 24 cases were “at risk” (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the10 cases were “at risk” in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3–48). The radiographic follow-up showed no radiolucent lines or osteolysis. 2 cups have been revised for fractures of the ceramic bearings, but none for loosening.
Interpretation
Low BMD contributed to cup migration beyond the settling period of 3 months, but the migrating cups appeared to osseointegrate eventually.
doi:10.3109/17453674.2015.1115312
PMCID: PMC4940591  PMID: 26569616
18.  Acetabular cup positioning in revision total hip arthroplasty with Paprosky type III acetabular defects: Martell radiographic analysis 
International Orthopaedics  2013;37(10):1905-1910.
Purpose
This study evaluates acetabular cup position in the setting of revision total hip arthroplasty (THA) with severe acetabular bone defects.
Methods
With a definition of safe zone of abduction (30–50°) and anteversion (5–25°), acetabular cup position was measured by a digital image analysis program for 34 patients with Paprosky type III acetabular bone defects.
Results
There were 24 cups (71 %) for abduction and 26 cups (76 %) for anteversion located in the safe zone. Nineteen cups (56 %) were within the safe zone for both abduction and anteversion. There was no dislocation, however one cup out of the safe zone resulted in early cup failure due to aseptic loosening.
Conclusions
The acetabular cup positioning in patients with Paprosky type III defects was 'optimal' in half of the cases. The prevalence of optimal acetabular cup position was similar to those reported in primary THA, suggesting that the presence of a large acetabular bone defect may not be a significant risk factor for suboptimal acetabular cup positioning in the setting of revision THA.
doi:10.1007/s00264-013-2008-0
PMCID: PMC3779547  PMID: 23881062
Total hip arthroplasty; Revision; Acetabular bone defect; Paprosky type III; Cup position; Martell technique
19.  Ten-year results with the Morscher press-fit cup: an uncemented, non-modular, porous-coated cup inserted without screws 
International Orthopaedics  2010;35(7):957-963.
Total hip arthroplasty (THA) with well designed cementless acetabular implants has shown excellent results. The purpose of this study was to assess our clinical and radiological outcomes using an uncemented cup. We conducted a prospective cohort study including all consecutive primary THAs performed with the Morscher press-fit cup, an uncemented non-modular acetabular component, between March 1996 and December 1998. Patients were evaluated at ten years with clinical and radiological follow-up, patient satisfaction and questionnaire assessment using the Harris hip score (HHS), Merle d’Aubigné and Postel score, the UCLA score, the 12-item short-form health survey (SF-12) and a visual analog scale. Five hundred sixty-one THAs were performed in 518 patients. At 120 months (± 7.3 months), 303 patients with 335 THAs were still available for follow-up. None of the patients had required cup revision for aseptic loosening. At ten years, the cup survivorship was 98.8% (95% CI 97.4–99.5) with cup revision for any cause as an endpoint. No radiolucencies were seen around the cups, but osteolytic defects involved 21 stems (8.3%). Mean total linear polyethylene wear was 0.9 mm. The Morscher acetabular replacement cup provides excellent results at ten years. There were no revisions for aseptic loosening of the cup, and no osteolytic defects were found around the cup. Patient satisfaction was high and the clinical results were very good.
doi:10.1007/s00264-010-1059-8
PMCID: PMC3167411  PMID: 20524114
20.  Results of the cementless Plasmacup in revision total hip arthroplasty: a retrospective study of 72 cases with an average follow-up of eight years 
Background
There are multiple revision implant systems currently available for socket revision in revision total hip arthroplasty. Up until now, not all of these systems have been followed up with regards to their long-term use as a revision implantation.
For the first time, this study presents the hemispherical porous-coated socket Plasmacup SC, produced by Aesculap, Tuttlingen, Germany, and the clinical and radiological mid-term results of this revision cup implant.
Methods
Over a period of ten years the Plasmacup SC press-fit-cup was used as a revision implant in 72 consecutive aseptic cases which were included in this retrospective study. The mean follow-up period was 8 years. Bone graft transplantation was performed in 32% of all cases. In 90%, the cup was fixed with additional screws. The follow-up radiographs were analysed with regards to cup migration, osteointegration and osteolysis in the DeLee zones using a computer aided program taking the teardrop figure as a main point of reference. For clinical evaluation the Harris-Hip-Score and the WOMAC-Score were utilized.
Results
At the follow up examination, the mean Harris-Hip-Score was 83.5 points and the mean WOMAC-Score 34.7 points. 93% of all patients were satisfied with the result of the operation. No aseptic cup loosening could be observed and only one cup had to be removed due to infection. No significant longitudinal or transversal cup migration could be observed.
Conclusion
Aesculap's Plasmacup SC is suitable as a cementless cup revision implant. There is stable cup osteointegration, post press-fit implantation, even in the case of major acetabular bone defects.
doi:10.1186/1471-2474-11-101
PMCID: PMC2887774  PMID: 20507578
21.  Recurrence of Dislocation Following Total Hip Arthroplasty Revision Using Dual Mobility Cups Was Rare in 180 Hips Followed Over 7 Years 
HSS Journal  2012;8(3):251-256.
Background
Dual mobility (DM) cups of mobile polyethylene were introduced to prevent total hip arthroplasty (THA) dislocation, but no large series with this design to treat recurrent instability have been reported.
Purpose
Our retrospective investigation ascertained the efficiency of DM cups in correction of recurrent dislocation and assessed any adverse effects.
Methods
One hundred eighty THAs with recurrent instability were revised to DM cups in 180 patients (mean age, 67.4 ± 11.7 years; range, 19 to 92 years). Thirty-one patients (17.2%) underwent at least one earlier THA revision, and 15 (10.3%) incurred non-union of the greater trochanter. Of the initial group in 2009, 145 patients had completed evaluations which included assessment of the Harris Hip Score and a radiographic assessment at a mean follow-up of 7.7 ± 2.2 years (range, 4 to 14 years). The rate of survival was calculated considering any reason for revision as failure.
Results
At follow-up, Harris hip score was 83.9 ± 16.1 (range, 21 to 100). Dislocation of the large articulation occurred in seven hips (4.8%), and only two recurred (1.4%) (one requiring additional revision). In addition, two intra-prosthetic dislocations of the small articulation (1.4%) were observed and needed revision surgery. The large number of earlier surgeries and non-union of the greater trochanter were related to recurrent instability. Two cups (1.4%) showed signs of definite loosening; six (4.1%) presented signs of possible loosening. Twenty-nine hips manifested femoral or acetabular osteolysis (20%), but only three were severe. Eight-year survival rate considering revision for any reason was 92.6% (95% CI, 85.5–96.4%).
Conclusions
This series indicates that DM cups are a viable option to treat recurrent THA instability. Their design provides a low risk of recurrent instability without increasing mechanical complications.
doi:10.1007/s11420-012-9301-0
PMCID: PMC3470678  PMID: 23144637
hip arthroplasty; instability; dual mobility; revision; bearing; wear; polyethylene
22.  Restoration of the Hip Center During THA Performed for Protrusio Acetabuli Is Associated With Better Implant Survival 
Background
Acetabular protrusio is an uncommon finding in hip arthritis. Several reconstructive approaches have been used; however the best approach remains undefined.
Questions/purposes
Our purposes in this study were to (1) describe the THA survivorship for protrusio as a function of the acetabular component, (2) evaluate survivorship of the cup as a function of restoration of radiographic hip mechanics and offset, and (3) report the long-term clinical results.
Methods
One hundred twenty-seven patients (162 hips) undergoing primary THA with acetabular protrusio were retrospectively reviewed. The mean age of the patients at surgery was 66 ± 13 years, and the mean followup was 10 ± 6 years (range, 2–25 years).The cup fixation was uncemented in 107 (83 with bone graft) and cemented in 55 hips (14 with bone graft). Preoperative and postoperative radiographs were reviewed for restoration of hip mechanics and offset.
Results
The THA survival from aseptic cup revision at 15 years was 89% (95% CI, 75%–96%) for uncemented compared with 85% (95% CI, 68%–94%) for cemented cups. The risk of aseptic cup revision significantly increased by 24% (hazards ratio, 1.24; 95% CI, 1.02–1.5) for every 1 mm medial or lateral distance away from the native hip center of rotation to the prosthetic head center. Harris hip scores were improved by mean of 27 ± 20 points (n = 123) with a higher postoperative score for uncemented bone grafted compared with solely cemented cups (81 ± 16 versus 71 ± 20 points).
Conclusions
Restoring hip center of rotation using an uncemented cup with or without bone graft was associated with increased durability in our series. There was a 24% increase in the risk of aseptic cup revision for every 1 mm medial or lateral distance away from the native hip center to the prosthetic head center.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3072-x
PMCID: PMC3773116  PMID: 23703532
23.  Results of 3,668 primary total hip replacements for primary osteoarthritis in patients under the age of 55 years 
Acta Orthopaedica  2011;82(5):521-529.
Background and purpose
In a previous study based on the Finnish Arthroplasty Register, the survival of cementless stems was better than that of cemented stems in younger patients. However, the survival of cementless cups was poor due to osteolysis. In the present study, we analyzed population-based survival rates of the cemented and cementless total hip replacements in patients under the age of 55 years with primary osteoarthritis in Finland.
Patients and methods
3,668 implants fulfilled our inclusion criteria. The previous data included years 1980–2001, whereas the current study includes years 1987–2006. The implants were classified in 3 groups: (1) implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group 1); (2) implants with a cementless, anatomic, proximally circumferentially porous-coated stem, with or without hydroxyapatite, and a porous-coated press-fit cup with or without hydroxyapatite (cementless group 2); and (3) a cemented stem combined with a cemented all-polyethylene cup (the cemented group). Analyses were performed separately for 2 time periods: those operated 1987–1996 and those operated 1997–2006.
Results
The 15-year survival for any reason of cementless total hip replacement (THR) group 1 operated on 1987–1996 (62%; 95% CI: 57–67) and cementless group 2 (58%; CI: 52–66) operated on during the same time period was worse than that of cemented THRs (71%; CI: 62–80), although the difference was not statistically significant. The revision risk for aseptic loosening of cementless stem group 1 operated on 1987–1996 (0.49; CI: 0.32–0.74) was lower than that for aseptic loosening of cemented stems (p = 0.001).
Interpretation
Excessive wear of the polyethylene liner resulted in numerous revisions of modular cementless cups. The outcomes of total hip arthroplasty appear to have been relatively unsatisfactory for younger patients in Finland.
doi:10.3109/17453674.2011.618908
PMCID: PMC3242947  PMID: 21992084
24.  10-year results of the uncemented Allofit press-fit cup in young patients 
Acta Orthopaedica  2014;85(4):368-374.
Background and purpose
Uncemented acetabular components in primary total hip arthroplasty (THA) are commonly used today, but few studies have evaluated their survival into the second decade in young and active patients. We report on a minimum 10-year follow-up of an uncemented press-fit acetabular component that is still in clinical use.
Methods
We examined the clinical and radiographic results of our first 121 consecutive cementless THAs using a cementless, grit-blasted, non-porous, titanium alloy press-fit cup (Allofit; Zimmer Inc., Warsaw, IN) without additional screw fixation in 116 patients. Mean age at surgery was 51 (21–60) years. Mean time of follow-up evaluation was 11 (10–12) years.
Results
At final follow-up, 8 patients had died (8 hips), and 1 patient (1 hip) was lost to follow-up. 3 hips in 3 patients had undergone acetabular revision, 2 for deep infection and 1 for aseptic acetabular loosening. There were no impending revisions at the most recent follow-up. We did not detect periacetabular osteolysis or loosening on plain radiographs in those hips that were evaluated radiographically (n = 90; 83% of the hips available at a minimum of 10 years). Kaplan-Meier survival analysis using revision of the acetabular component for any reason (including isolated inlay revisions) as endpoint estimated the 11-year survival rate at 98% (95% CI: 92–99).
Interpretation
Uncemented acetabular fixation using the Allofit press-fit cup without additional screws was excellent into early in the second decade in this young and active patient cohort. The rate of complications related to the liner and to osteolysis was low.
doi:10.3109/17453674.2014.925351
PMCID: PMC4105767  PMID: 24875058
25.  Reconstruction of the rotation center of the hip after oblong cups in revision total hip arthroplasty 
Background
The preoperative bone defect and the reconstruction of the center of rotation of the hip are critical in acetabular revision surgery. Uncemented oblong cups are employed in order to manage these issues. We analyzed the clinical results and rates of revision of two different uncemented oblong cups, the reconstruction of the center of rotation of the hip, as well as the rate of radiological loosening and possible risk factors.
Materials and methods
Forty-five patients (46 hips) underwent acetabular revision surgery using two different uncemented oblong cups. We assessed the clinical results and the survival rate for revision and aseptic loosening. Intraoperative bone loss was classified according to Paprosky, and acetabular reconstruction was assessed according to Ranawat. The mean follow-up was 7.2 years (range 4–11 years).
Results
There were four re-revisions (three due to aseptic loosening); the survival rate for re-revision due to aseptic loosening was 60.1 % at seven years. The mean distance between the center of the femoral head prosthesis and the approximate center of the femoral head improved from 21.5 to 10.2 mm. Thirteen cups showed radiological loosening; the survival rate for radiological loosening at seven years was 40.54 %. A smaller postoperative horizontal distance was correlated with cup loosening.
Conclusions
Although optimal acetabular reconstruction can be achieved by using oblong uncemented cups in revision hip surgery, the clinical and radiological results are not encouraging. Excessive medialization of the cup may increase the rate of loosening.
doi:10.1007/s10195-012-0217-8
PMCID: PMC3585906  PMID: 23160803
Revision hip arthroplasty; Cementless cup; Reconstruction; Outcome

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