Analysis and results of dissociation of the polyethylene liner in the Harris-Galante I acetabular component

The Harris-Galante I modular acetabular components (Zimmer, Warsaw, Ind) were most widely used in the 1980s in primary and revision total hip arthroplasty. We assessed 76 primary total hip arthroplasties performed using Harris-Galante I modular acetabular components. Dissociation of the polyethylene liner occurred in 5 patients and required revision surgery. None of the 76 hips had fractures of the metal locking tines on the metal shell. Liner dissociation was attributed to fatigue fracture of the polyethylene, a result of a gap between the liner and the metal shell. The thin polyethylene liner rim aggravated failure. The revision technique was to cement the polyethylene liner into the well-fixed Harris-Galante metal shell. The average follow-up observation period after revision surgery was 6.4 years; and there was no recurrence of dissociation, which supports the use of our revision technique.     

Fixation of ultrahigh-molecular-weight polyethylene liners to metal-backed acetabular cups

Locking mechanisms and metal-liner interface surfaces of six modular acetabular systems were evaluated to determine their effect on micromotion and backside wear of the polyethylene liner. Rotational and axial motion between the metal shell and polyethylene liner was measured in the Duraloc (DePuy, Warsaw, IN), Harris-Galante (Zimmer, Warsaw, IN), Impact (Biomet, Warsaw, IN), Lip Loc (Biomet). Precision Osteoloc (Howmedica, Rutherford, NJ), and Reflection (Smith & Nephew Orthopaedics, Memphis, TN) designs at the start of each test, and at 1 million, 5 million, and 10 million cycles. At 10 million cycles, the Lip Loc and Reflection cups had significantly lower rim micromotion than the Duraloc and Harris-Galante cups (F < .0010). The Impact, Precision Osteoloc, and Reflection cups had significantly lower rim subsidence than the Harris-Galante cup (F < .0025). The Harris-Galante cup had significantly greater rotational micromotion than the Lip Loc cup (F < .0074), and had significantly greater interface slippage than the Impact and Reflection cups (F < .0070). The Lip Loc produced significantly lower dome micromotion than the Harris-Galante (F < .0300). The Lip Loc and Reflection cups had significantly less backside wear than the Duraloc and Harris-Galante cups (P < .0001), the Impact cup (P < .0243), and the Precision Osteoloc (P < .0027) cup.     

The relationship between increased hip range of motion, wear, and locking mechanism failure in the Harris-Galante acetabular component

We performed both clinical and radiographic evaluations of 178 patients (190 hips) who had undergone cementless total hip arthroplasties using Harris-Galante I/II porous cups after an average 12-year follow-up period (range, 8-18 years). We revised 15 Harris-Galante I/II porous cups (7.8%), and the locking mechanism was broken in 10 revised cups (67%). There was a significant association between locking mechanism failure and linear polyethylene wear. We observed a significant positive correlation between linear polyethylene wear and increased ranges of motion such as flexion, adduction, and external rotation at the last follow-up visit after the primary operation. Increased ranges of motion seen in Asians induced higher linear polyethylene wear and locking mechanism failure due to impingement of the neck and cup.     

Dissociation of the Harris-Galante II polyethylene liner in rheumatoid arthritis patients

Abstract We investigated the dissociation of polyethylene liner from the Harris-Galante II metal shell inarthritis patients with rheumatoid arthritis. A total of 41 total hip arthroplasties using Harris-Galante II cup in 34 patients were reviewed retrospectively. There were three cases with dissociation of the polyethylene liner and locking tine breakage of metal shell, and one case with locking tine breakage without dissociation of the polyethylene liner. In three cases with dissociation of the polyethylene liner, two cups had been placed relatively horizontally while the third had been placed relatively vertically. In general, high activity, heavy body weight, and young age are thought to be risk factors for polyethylene liner dissociation, but these patients generally have lower activity and lighter body weight compared to patients with osteoarthritis or avascular necrosis of the femoral head. The use of small femoral heads and either horizontal or vertical cup placement may have allowed impingement and tine damage, contributing to liner dissociation in these relatively inactive patients.     

Porous-coated cups fixed with screws: A 12-year clinical and radiostereometric follow-up study of 50 hips

Background?Excellent mid-term results have stimulated the use of hemispherical porous-coated cups in hip replacement. With longer follow-up, there have been problems related to polyethylene wear and liner fixation, and osteolysis has been documented in reports of selected cases. We evaluated the clinical and radiographic results of 50 patients followed for 12 years.

Patients and methods?58 consecutive patients (58 hips), mean age 55 years, were operated with Harris-Galante (HG) I or II cups using line-to-line fit and additional screw fixation. Polyethylene linersγ-sterilized in air and 32-mm ceramic heads were used. 8 patients died within 12 years, leaving 50 patients with a complete 12year follow-up. 23 of the cups were also evaluated with radiostereometry (RSA) for migration, liner stability, and wear.

Results?All metal shells were still in situ after 12 years. 4 hips had been revised due to femoral loosening. In these revisions, the liner had been exchanged due to wear and/or instability, resulting in a cup survival rate of 89%. 28 cups displayed osteolytic lesions, mainly in relation to screws. RSA revealed minimum translations, but in many cases there were pronounced liner rotations suggesting unstable liners within the metal shell. The annual proximal wear was 0.09 mm and the three-dimensional wear was 0.16 mm.

Interpretation?RSA can predict the long-term performance of cup fixation. Low migration during the initial years after implantation indicates excellent long-term results regarding fixation of the metal shell. The main problem with this design appears to be liner instability and osteolysis, factors that are probably interrelated. Because these phenomena are clinically silent, we recommend regular follow-up of patients with HG cups to avoid sudden loosening and complicated revisions.     

Long-term results of uncemented acetabular cups with an ACS polyethylene liner. A 14–16-year follow-up study

We assessed the clinical and radiographic results of 40 porous-coated acetabular cups with an Acetabular Cup System polyethylene liner over a minimum 14-year follow-up. Femoral head penetration was estimated using a software package. Fifteen cups were revised, 11 due to polyethylene liner rupture. All cups but two were radiographically stable, and 11 hips showed acetabular osteolysis. The overall femoral head penetration rate in hips without liner fracture with reference to the early penetration point was 0.1188+/-0.070 mm per year. Polyethylene liner fractures were associated with higher early femoral head penetration (P<0.0001) and a vertical cup position (P=0.0016). The 14-year survival without cup revision for any reason was 63.9%, 71.8% with no ACS polyethylene liner fracture and 65.3% with no acetabular osteolysis. Most cups showed a good clinical outcome in general, but major Acetabular Cup System liner failure and osteolysis were frequent. Patients with the ACS cups still in place should be monitored closely.     

A long-term follow-up study of the cementless THA with anatomic stem/HGPII cup with 22-mm head

The anatomic femoral component and Harris-Galante porous II (HGPII) cup were developed to provide more reliable bone ingrowth. We performed 20 cementless total hip arthroplasties (THAs) with anatomic stem/HGPII cup with 22-mm head in 14 consecutive patients, and evaluated the clinical and radiological results for a mean follow-up of 12.8 years. The all-anatomically designed stem provided excellent clinical and radiographic results. Four acetabular components underwent revision: three for fracture of the locking mechanism and wear of the polyethylene liner and one for the locking mechanism failure with dislocation of the HGPII cup. The abduction angles of the four revised acetabular components were apparently higher. The survivorship 13 years after surgery was 78%. Our findings show good long-term results using the anatomic femoral component, while the HGPII cup combined with 22-mm head seems to have poor durability due to locking mechanism failure.     

Porous-coated cups fixed with screws: a 12-year clinical and radiostereometric follow-up study of 50 hips

Background Excellent mid-term results have stimulated the use of hemispherical porous-coated cups in hip replacement. With longer follow-up, there have been problems related to polyethylene wear and liner fixation, and osteolysis has been documented in reports of selected cases. We evaluated the clinical and radiographic results of 50 patients followed for 12 years.

Patients and methods 58 consecutive patients (58 hips), mean age 55 years, were operated with Harris-Galante (HG) I or II cups using line-to-line fit and additional screw fixation. Polyethylene linersγ-sterilized in air and 32-mm ceramic heads were used. 8 patients died within 12 years, leaving 50 patients with a complete 12year follow-up. 23 of the cups were also evaluated with radiostereometry (RSA) for migration, liner stability, and wear.

Results All metal shells were still in situ after 12 years. 4 hips had been revised due to femoral loosening. In these revisions, the liner had been exchanged due to wear and/or instability, resulting in a cup survival rate of 89%. 28 cups displayed osteolytic lesions, mainly in relation to screws. RSA revealed minimum translations, but in many cases there were pronounced liner rotations suggesting unstable liners within the metal shell. The annual proximal wear was 0.09 mm and the three-dimensional wear was 0.16 mm.

Interpretation RSA can predict the long-term performance of cup fixation. Low migration during the initial years after implantation indicates excellent long-term results regarding fixation of the metal shell. The main problem with this design appears to be liner instability and osteolysis, factors that are probably interrelated. Because these phenomena are clinically silent, we recommend regular follow-up of patients with HG cups to avoid sudden loosening and complicated revisions.     

A Case of Pseudarthrosis of the Neck of the Femur,Treated by the Method of Extra-Articular Ostesynthesis

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 monoâ€?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.     

Cementless hemispheric acetabular components: 2–4-year results

A retrospective clinical and radiographic analysis was performed on 99 patients (106 hips) undergoing total hip arthroplasty with noncemented Harris-Galante (Zimmer, Warsaw, IN) or Optifix (Smith Nephew Richards, Memphis, TN) acetabular components. There were 94 primary and 12 revision procedures with a minimum follow-up period of 24 months (range, 24–52 months). The cups were evaluated for evidence of vertical and horizontal migration, as well as the presence of radiolucencies at the bone-implant interface. Age, sex, component inclination and medialization, cup coverage, and number of fixation screws used were examined to determine the influence of these factors on the incidence of cup migration or radiolucent line formation. A radiolucent line was present in at least one zone in 60% of the Harris-Galante and 45% of the Optifix cups. Progressive radiolucent lines were noted in two of the Optifix and three of the Harris-Galante components. Two Harris-Galante cups (1.9%) were revised. There were no Optifix cup migrations or evidence of instability in the Optifix or remaining Harris-Galante cups. Although there was a trend toward an increased incidence of radiolucencies in those cups lacking complete coverage, no statistically significant radiographic predictors for failure or impending failure could be determined from this short-term follow-up study. With the exception of the two revisions, all acetabular components performed well clinically over the study period.     

The Harris-Galante Porous acetabular component at intermediate follow-up

Outcome of the acetabular component in 90 consecutive primary noncemented total hip arthroplasties (THAs) was prospectively studied. The acetabular cup consisted of a hemispherical titanium alloy shell with a titanium fiber-mesh porous coating and a modular polyethylene liner (Harris-Galante Porous-1, Zimmer, Warsaw, Ind). The cup was implanted using line-to-line reaming with adjunctive dome screw fixation. The femoral component consisted of a titanium alloy stem with titanium fiber-mesh porous coating and a 28-mm cobalt-chrome modular head. Mean patient age was 53 years (range: 27-75 years); male:female ratio was 48:42; and mean follow-up was 6 years (range: 4.5-8 years). One acetabular component was revised for aseptic loosening. Of 81 unrevised hips available for follow-up, mean Harris hip score was 57 preoperatively and 96 at final follow-up (72% excellent, 15% good, 1 3% fair, and none poor). Of 61 unrevised hips with adequate radiographic follow-up, radiographic failure (complete periprosthetic radiolucency) was evident in 3 (4.9%) and periacetabular osteolysis in none. Radiographic failure did not correlate with poor clinical outcome. Linear polyethylene wear rate (mean: 0.13 mm/year) did not correlate with age, gender, weight, outcome, or cup abduction angle, but did correlate with the presence of femoral periprosthetic osteolysis (0.18 mm/year with femoral osteolysis versus 0.11 mm/year without; P= .01). This series of porous-coated hemispherical cups demonstrated excellent intermediate-term clinical and radiographic outcome, comparable with similarly favorable results reported by the prosthesis designers. A potentially adverse effect of polyethylene wear on the longevity of a THA was supported by a positive correlation between polyethylene wear rate and femoral osteolysis.     

Polyethylene liner dissociation in Harris-Galante acetabular components: a report of 7 cases.

Harris-Galante modular acetabular components (Zimmer, Warsaw, IN) have been used widely for primary and revision total hip arthroplasties. The survivorship of this implant has been well documented in the literature. Failure of the liner locking mechanism and subsequent dissociation of the polyethylene liner from the metal-backed shell is a potential cause of failure, however. We report 7 cases of liner dissociation and propose the mode of failure. The result in all cases was a well-fixed metal acetabular shell with a failed locking mechanism, which usually is managed by revision of the entire component. This procedure may be accompanied by the potential loss of acetabular bone stock, which should be replenished.     

Revision for aseptic loosening of uncemented cups in 4,352 primary total hip prostheses: A report from the Norwegian Arthroplasty Register

From September 1987 until January 1994 the Norwegian Arthroplasty Register recorded 5,021 primary total hip replacements performed with uncemented acetabular components. We compared the survival until revision for aseptic loosening of the cup, in the 11 commonest types (n 4,352).

The overall cumulative revision rate for the acetabular components was 3.2% after 5 years and 7.1 YO after 6 years, with large differences among the designs.

With the hydroxyapatite (HA)-coated cups and the hemispheric porous-coated cups, the failure rate was less than 0.1 YO. Of the unthreaded hemispheric porous-coated cups, Harris-Galante and Gemini (n 626), none had been revised, and of the HA-coated cups, Atoll and Tropic (n 1,943), only 1 had been revised.

For the threaded uncoated metal-backed cups, the results varied from no revisions of the PM cups (n 148) to a cumulative 6-year revision rate of 21 YO for the Ti-Fit (n 300). The all-polyethylene Endler cups (n 334) had a cumulative revision rate of 14%.

Women and patients with inflammatory arthritis had poorer results. However, the type and the design of the cups were of far greater importance for the results than patient-related factors.     

Revision for aseptic loosening of uncemented cups in 4,352 primary total hip prostheses: A report from the Norwegian Arthroplasty Register

From September 1987 until January 1994 the Norwegian Arthroplasty Register recorded 5,021 primary total hip replacements performed with uncemented acetabular components. We compared the survival until revision for aseptic loosening of the cup, in the 11 commonest types (n 4,352).

The overall cumulative revision rate for the acetabular components was 3.2% after 5 years and 7.1 YO after 6 years, with large differences among the designs.

With the hydroxyapatite (HA)-coated cups and the hemispheric porous-coated cups, the failure rate was less than 0.1 YO. Of the unthreaded hemispheric porous-coated cups, Harris-Galante and Gemini (n 626), none had been revised, and of the HA-coated cups, Atoll and Tropic (n 1,943), only 1 had been revised.

For the threaded uncoated metal-backed cups, the results varied from no revisions of the PM cups (n 148) to a cumulative 6-year revision rate of 21 YO for the Ti-Fit (n 300). The all-polyethylene Endler cups (n 334) had a cumulative revision rate of 14%.

Women and patients with inflammatory arthritis had poorer results. However, the type and the design of the cups were of far greater importance for the results than patient-related factors.     

The Harris-Galante cementless THA: a 19- to 25-year follow-up study

The goal of this study was to evaluate the long-term survivorship of primary cementless total hip arthroplasty (THA) using Harris-Galante porous I acetabular and Harris-Galante porous femoral components. From July 1985 to December 1991, we performed primary cementless THA on 76 hips (70 patients). Twenty-nine patients (31 hips) died due to causes unrelated to the THA, and 6 patients (7 hips) were lost to follow-up. Of 76 hips (70 patients) studied, 38 hips (35 patients) were available for follow-up at a mean 22.5 years (range, 19-25 years) postoperatively. Mean patient age at index procedure was 51.2 years (range, 42-65 years). Average Harris Hip Score was 40.5 points preoperatively and 85.8 points at final follow-up. No patient had an early or late postoperative deep infection. Radiographically, the acetabular component fixation was stable in all 38 hips. The femoral component was bone-ingrown in 26 hips, stable-fibrous in 10, and unstable in 2. One unstable hip required revision of the femoral component. Dissociation of the polyethylene liner occurred in 3 hips without fractures of the metal locking tines and required revision of the polyethylene liner and the articular head. A total of 4 hips had documented revision, and 1 femoral component failed radiographically. The survival rate with the endpoint defined as revision surgery and radiographic loosening was 86.8% at 22.5 years of follow-up. Mean polyethylene wear was 0.085 mm/year (range, 0.031-0.15 mm). This study found that the Harris-Galante porous I acetabular and Harris-Galante porous femoral components produce excellent long-term results.     

Catastrophic failure of a modular revision total hip polyethylene insert

Early catastrophic failure of a modular polyethylene component is a potential problem after revision total hip arthroplasty. We describe an unusual case of polyethylene failure that occurred within 18 months of implantation in which no obvious technical error or mechanical failure was identified. The acetabular polyethylene insert was prepared with gas plasma sterilization, and the shelf life was 4 months. Radiographic evaluation used generalized Hough transforms to assess the cup articulation. We identified cup penetration of 2.8 mm before revision and catastrophic destruction of the polyethylene liner at the time of revision. Possible factors implicated for failure included a thin polyethylene liner, increased hip separation, femoral head mismatch, and the high activity level of a younger patient. We believe that this case report highlights the need for future investigations of these subtle factors.     

Polyethylene liner dislocation in Harris Galante acetabular components

AIM: Dislocation and subsequent dissociation of the polyethylene liner as a result of failure of the acetabular locking mechanism is a potential source of failure in the Harris-Galante acetabular component. The purposes of this study are to present seven cases with a liner dislocation due to failure of the liner locking mechanism. METHOD: Between March 1997 and December 2001, seven patients who had had a total hip arthroplasty presented with clinical and radiologic signs of liner dislocation and signs of polyethylene wear of the liner from a Harris Galante acetabular shell. In all cases the intraoperative findings showed evidence of failure of the liner locking mechanism and subsequent dislocation. The medical records, radiographs, operative notes and explanted retrieved components were reviewed. RESULTS: The components had been in situ for an average of 5.3 years (range 1-9 years). Two components were first generation, five were second generation. The symptoms developed spontaneously in five patients, the other two patients described a minor trauma. Radiographs showed eccentric position of the head in all cases. All acetabular components showed an excellent stability intraoperatively, nevertheless we had to remove the well fixed acetabular shell due to complete destruction of the liner locking mechanism in two cases. Treatment consisted of revision of the shell in two patients and exchange of the liner in five patients. All retrieved liners showed severe deformation and/or fracture of the rim. CONCLUSION: Harris Galante modular acetabular components have been used widely for primary and revision arthroplasty. The survival of this implant has been well documented in the literature. Failure of the liner locking mechanism and following dislocation or fracture of the polyethylene liner is a potential cause of failure which may possibly occur more often than the literature to date has documented. We report seven cases of liner dislocation, in which two acetabular components had to be removed completely due to destruction of the liner locking mechanism. In the other five cases exchange of the liner was possible thanks to well timed revision. We believe that, as the liner wears and becomes loose due to an inefficient locking mechanism, the load increases on the polyethylene rim until it deforms or fractures. As a consequence of the prosthetic design at that stage nothing can prevent the liner from rotating out of the shell.     

Effects of hydroxyapatite coating of cups used in hip revision arthroplasty: A Swedish Hip Arthroplasty Register study of 1,780 revisions

Background and purpose

Coating of acetabular revision implants with hydroxyapatite (HA) has been proposed to improve ingrowth and stability. We investigated whether HA coating of revision cups can reduce the risk of any subsequent re-revision.

Methods

We studied uncemented cups either with or without HA coating that were used at a primary acetabular revision and registered in the Swedish Hip Arthroplasty Register (SHAR). 2 such cup designs were identified: Harris-Galante and Trilogy, both available either with or without HA coating. These cups had been used as revision components in 1,780 revisions of total hip arthroplasties (THA) between 1986 and 2009. A Cox proportional hazards model including the type of coating, age at index revision, sex, cause of cup revision, cup design, the use of bone graft at the revision procedure, and the type of cup fixation at primary THA were used to calculate adjusted risk ratios (RRs with 95% CI) for re-revision for any reason or due to aseptic loosening.

Results

71% of the cups were coated with HA and 29% were uncoated. At a mean follow-up time of 6.9 (0–24) years, 159 (9%) of all 1,780 cups had been re-revised, mostly due to aseptic loosening (5%), dislocation (2%), or deep infection (1%). HA coating had no significant influence on the risk of re-revision of the cup for any reason (RR = 1.4, CI: 0.9–2.0) or due to aseptic loosening (RR = 1.1, 0.6–1.9). In contrast, HA coating was found to be a risk factor for isolated liner re-revision for any reason (RR = 1.8, CI: 1.01–3.3). Age below 60 years at the index cup revision, dislocation as the cause of the index cup revision, uncemented cup fixation at primary THA, and use of the Harris-Galante cup also increased the risk of re-revision of the cup. In separate analyses in which isolated liner revisions were excluded, bone grafting was found to be a risk factor for re-revision of the metal shell due to aseptic loosening (RR = 2.1, CI: 1.05–4.2).

Interpretation

We found no evidence to support the notion that HA coating improves the performance of the 2 studied cup designs in revision arthroplasty. In contrast, patient-related factors such as younger age and dislocation as the reason for cup revision, and technical factors such as the choice of revision cup were found to influence the risk of subsequent re-revision of the cup. The reason for inferior results after revision of uncemented cups is not known, but it is possible that these hips more often had pronounced bone loss at the index cup revision.The most common cause of re-revision of the hip after revision surgery is failure of the acetabular component (Swedish Hip Arthrolasty Register (SHAR) 2010). Acetabular revision with cemented implants has shown up to 20% failure at 10 years of follow-up, whereas contemporary designs of uncemented acetabular cups have substantially reduced this failure rate (Callaghan et al. 1985, Kavanagh et al. 1985, Katz et al. 1997, Lie et al. 2004). Loosening of the primary acetabular component often leaves substantial bone loss and a sclerotic acetabular bed. Fixation of revision cups is therefore demanding, and several techniques have been used to restore bone loss and achieve long-term fixation of the revision cup—such as screw fixation, bone grafting, and different cup designs (Palm et al. 2007, Pulido et al. 2011). The use of hydroxyapatite (HA) coating on cups used as revision implants has been proposed to be an improvement over uncoated cups (Dorairajan et al. 2005, Geerdink et al. 2007).HA is the main inorganic component of human bone. It has therefore been hypothesized that coating of metallic implants with HA enhances ingrowth of bone and thus leads to improved stability (Soballe et al. 1999). Indeed, some HA-coated cups perform well and are still in use, while other HA-coated cups have shown high failure rates in the long term. For instance, inferior results were achieved with the Romanus cup where the combination of an inferior locking mechanism of the liner with an inferior type of polyethylene resulted in excessive osteolysis in the acetabular region (Puolakka et al. 1999, Lyback et al. 2004, Lazarinis et al. 2010, SHAR 2010). Due to the relatively small numbers of revision procedures, very few authors have reported results after hip revision arthroplasty using HA-coated implants. To our knowledge, there have been no registry studies specifically investigating the performance of HA-coated hip revision implants. Thus, the question of whether the use of HA coating on revision cups is beneficial remains to be answered.In this study, we analyzed the outcome of acetabular revision surgery using uncemented cups with or without HA coating recorded in the Swedish Hip Arthroplasty Register (SHAR). Our hypothesis was that coating of revision acetabular cups with HA reduces the risk of re-revision of the acetabular component inserted. The primary endpoint was re-revision of the acetabular component for any reason and the secondary endpoint was re-revision of the cup due to aseptic loosening.     

Dislodgment of polyethylene liners in first and second-generation Harris-Galante acetabular components. A report of eighteen cases

BACKGROUND: Dislodgment of the polyethylene liner is an increasingly common complication following total hip arthroplasty. The purposes of this study are to present the results in a series of patients with this complication and to analyze the mode of failure. METHODS: Between November 1995 and January 2001, eighteen patients who had had a total hip arthroplasty presented with dislodgment of the polyethylene liner from a Harris-Galante metal acetabular shell. The medical records, radiographs, operative notes, and retrieved components were reviewed. In addition, scanning electron microscopy was used to study the fractured surfaces in a shell that had four broken tines. RESULTS: The components had been in situ for an average of seven years (range, three to eleven years). Seventeen components were second generation, and one was first generation. Symptoms developed spontaneously in sixteen patients, during sexual intercourse in one, and following a fall on the hip in one. Radiographs showed eccentric positioning of the head in all of the hips and broken tines in six. All of the shells were well fixed. Treatment consisted of revision of the shell in four patients, exchange of the liner in four, cementation of a new liner into the shell in seven, and cementation of an all-polyethylene cup in three. The liners had severe damage of the rim. Scanning-electron microscopy of the fractured surfaces of four tines revealed a fatigue pattern. CONCLUSIONS: We believe that, as the liner wears and becomes loose because of an inadequate locking mechanism, progressive micromotion occurs and the load increases on the polyethylene rim until it deforms and/or fractures. Subsequently, nothing prevents the liner from rotating out of the shell. As this mechanism of failure appears to include fatigue failure of the locking tines and wear of the liner, this complication is likely to increase as the components age in situ.     

Unsatisfactory results with the cementless Omnifit acetabular component due to polyethylene and severe osteolysis

A high incidence of acetabular osteolysis (43%), associated with osteolytic lesions in the proximal femur (22.6%) and leading to a high revision rate, was experienced with the Omnifit total hip prosthesis. We reviewed the clinical and radiological results with 429 Omnifit total hips in 356 patients after a mean follow-up of 60 months. Time to revision and wear of the polyethylene liner with different acetabular shell types were specifically analysed. Pelvic osteolysis first became manifest in the acetabular bone opposite to the holes in the metal shell. Osteolysis occurred predominantly adjacent to the central hole in the metal shell of threaded cups; widespread and larger defects were found in press fit cups with peripheral screw holes. Kaplan Meier survival analysis demonstrated a higher probability for retaining the threaded cup at 6 years (96%; 95%-confidence interval: 93-99%) compared to the survival of the press fit cup (66%; 95%-CI: 56-77%). The results suggest a negative relationship between backside wear, the larger number of holes in the cup, the extent of osteolysis and survival rate of the press fit cups. Based on these findings and supported by similar reports about osteolysis related to the same cup design, it was hypothesised that backside wear due to the insufficient locking mechanism of the Omnifit acetabular cup was the major cause of the unsatisfactory results in our patients. For this reason we discontinued using this type of uncemented socket.