Porous-coated Acetabular Component Research Articles

The press-fit technique without screws and bone graft can be used as an alternative method in Crowe type II and III hip dysplasia.

Developmental dysplasia of the hip (DDH) is the most common cause of secondary hip arthrosis. The primary purpose of this study was to assess the results of an oversized hemispherical cup via the press-fit technique used for Crowe type II and III DDH without screws and to determine if adequate medialization and initial stability of the acetabular component would allow us to avoid screw and graft use. Between February 2012 and May 2020, the current study analyzed 43 hips with Crowe type II and III DDH treated with a porous-coated cup by placing the press-fit technique or screw. The acetabular cup was fixed with the press-fit technique without additional screws in 27 hips and with screws in 16 hips. The inclusion criterion in this study was a minimum 2-year-period after the surgery. The mean duration of follow-up was 6.83 ± 2.67 years in the press-fit group and 6.21 ± 2.01 years in the screw group. The mean age of the patients was 47.96 ± 12.37 years in the press-fit group and 50.5 ± 12.37 years in the screw group. Measurements revealed that the hip center of rotation (HCR) was located more medially and superiorly postoperatively than preoperatively in both groups. The mean cup coverage in the screw group was 85.58% ± 7.51% (75.3%-97.2%), while it was less than 90.41% ± 6.15% (76.3%-98.2%) in the press-fit group (p = 0.038). No component was revised because of loosening, and all of the implants were radiologically stable within the observation period. No statistically significant differences were observed regarding the postoperative limp-length discrepancy between the groups (p = 0.496). Press-fit implantation of a porous-coated acetabular component without screws can also be used as an alternative method for THA in Crowe type II and III DDH. The initial stability was obtained using the press-fit technique with a small cup positioned more medially and superiorly, which may allow the surgeon to avoid screw and graft use.

HOW MUCH STABILITY DO WE NEED IN THE 1 MM PRESS-FIT IMPLANTATION OF A POROUS-COATED ACETABULAR COMPONENT WITHOUT SCREWS DURING SURGERY?

Background: Press-fit implantation of a porous-coated acetabular component without screws can be used for total hip arthroplasty (THA). The purpose of this report is to determine adequate initial stability of the acetabular component by applying a novel method would allow us to avoid screw use and to evaluate the outcomes of an oversized hemispherical cup using the 1 mm press-fit technique. Methods: We retrospectively evaluated 119 consecutive patients who underwent THA from February 2011 to June 2015. The intra-operative stability of fixation was checked by trying to pull the metal shell out of the acetabulum using the shell holder (pull-out test). We confirmed these tests using a digital hand scale. When we reached 9 to 10 kg (1 kg = 9.81 N), we showed that the acetabular shell achieved good stability. Kaplan-Meier survivorship analysis was performed to calculate the survival rate of the acetabular component. Results: The mean follow-up was 6.9 years (5–10 years). No component was revised because of loosening, and all implants were radiologically stable within the observation period. One socket had been revised because of failure of dislocation, which had [Formula: see text] acetabular inclination. There was an acetabular fracture in one hip, which was operated on prior to THA. Conclusions: We used a new method to assess the initial stability gained using the press-fit technique, which may allow the surgeon to determine whether adequate initial stability is achieved. Cup position has a significant impact on the risk of revision of press-fit cementless acetabular component. The risk for early failure can be decreased by optimal cup positioning during primary implantation. In addition, while a stable bone-implant connection is desirable, fracture of the acetabulum can be avoided using the 1 mm press-fit technique.

Long-Term Outcome of Small Head Metal-On-Metal Total Hip Arthroplasty: A 15-to-22 Year Follow-Up

BackgroundThe Metasul articular interface was a second-generation metal-on-metal (MoM) total hip arthroplasty (THA) that was introduced as a promising interface with improved manufacturing technology, better clearances, and enhanced metal hardness. In December 2001, the manufacturer recalled these implants due to the failure of cup osseointegration. MethodsBetween 1997 and 2004, 168 consecutive primary Metasul THAs were performed in 144 patients. Most patients received a cementless femoral and porous-coated acetabular component with 28 mm head. A competing risk analysis was performed for determination separately for bearing surface-related, recalled bearing failure, and end point revision for any reason. For clinical patient evaluation, we used Harris hip score and University of California at Los Angeles scores. Cobalt and chromium ion level measurement and standard radiographic assessment was performed. ResultsOf the 168 THAs, 19 hips were revised at a mean period of 15 years as follows: 12 of them were due to recalled acetabular component, five hips had noninterface-related complication, and two true interface surface failure. The survival distribution function of all hips with revision for any reason was 88.4%, for bearing interface relation 98.8%, and 92.6% for recalled cups. The mean Harris hip score and University of California at Los Angeles scores were 85 and 6, respectively, and the median Co and Cr blood levels were 1.0 and 0.91 μg/L. ConclusionExcluding the recalled components, Metasul articular interface has performed extremely well at a minimum follow-up of 15 years in this relatively young population. There were two interface-related revisions in the entire cohort.

Outcome of a hemispherical porous-coated acetabular component with a proximally hydroxyapatite-coated anatomical femoral component: an update at 23 to 26 years’ follow-up

We previously reported the long-term results of the cementless Duraloc-Profile total hip arthroplasty (THA) system in a 12- to 15-year follow-up study. In this paper, we provide an update on the clinical and radiological results of a previously reported cohort of patients at 23 to 26 years´ follow-up. Of the 99 original patients (111 hips), 73 patients (82 hips) with a mean age of 56.8 years (21 to 70) were available for clinical and radiological study at a minimum follow-up of 23 years. There were 40 female patients (44 hips) and 33 male patients (38 hips). All acetabular and femoral components were well fixed and showed signs of bone ingrowth. Nine acetabular components were revised due to wear-osteolysis-related problems and four due to late dislocation. The probability of not having component revision at 25 years was 83.2% (95% confidence interval (CI) 74.5 to 91.8; number at risk 41). Acetabular osteolysis was observed in ten hips. The mean femoral head penetration was 1.52 mm (sd 0.8) at 15 years and 1.92 mm (sd 1.2) at 25 years. Receiver operating characteristic (ROC) analysis revealed that mean femoral penetration with a value of 0.11 mm/year or more was associated with the appearance of osteolysis. The 25-year Kaplan-Meier survival with different endpoints was 89.9% for acetabular osteolysis (95% CI 83.3 to 96.5), 92.1% for proximal femoral osteolysis (95% CI 86.1 to 98.2), and 75.5% for femoral osteopenia (95% CI 66.5 to 84.5). The Duraloc-Profile THA system showed excellent long-term bone fixation. Nevertheless, monitoring is recommended in order to detect wear and late dislocations in this population that was relatively young at the time of surgery. Cite this article: Bone Joint J 2019;101-B:378-385.

L’adhésion bactérienne n’est pas plus faible sur les céramiques que sur les autres biomatériels. Analyse in vitro

BackgroundAlthough there is some clinical evidence of ceramic bearings being associated with a lower infection rate after total hip arthroplasty (THA), available data remains controversial since this surface is usually reserved for young, healthy patients. Therefore, we investigated the influence of five commonly used biomaterials on the adhesion potential of four biofilm-producing bacteria usually detected in infected THAs. HypothesisCeramic biomaterials exhibit less bacterial adherence than other biomaterials. Material and methodsIn this in-vitro research, we evaluated the ability of Staphylococcus. aureus, Staphylococcus. epidermidis ATCC 35984, Escherichia. coli ATCC 25922 and Pseudomonas. aeruginosa to adhere to the surface of a cobalt-chromium metal head, a fourth-generation ceramic head, a fourth-generation ceramic insert, a highly-crossed linked polyethylene insert and a titanium porous-coated acetabular component. After an initial washing step, bacterial separation from the surface of each specimen was done with a vortex agitator. The colony-forming units were counted to determine the number of viable adherent bacteria. ResultsWe found no differences on global bacterial adhesion between the different surfaces (p=0.5). E. coli presented the least adherence potential among the analysed pathogens (p<0.001). The combination of E. coli and S. epidermidis generated an antagonist effect over the adherence potential of S. epidermidis individually (58±4% vs. 48±5%; p=0.007). The combination of P. aeruginosa and S. aureus presented a trend to an increased adherence of P. aeruginosa independently, suggesting an agonist effect (71% vs. 62%; p=0.07). DiscussionCeramic bearings appeared not to be related to a lower bacterial adhesion than other biomaterials. However, different adhesive potentials among bacteria may play a major role on infection's inception. Level of evidenceIV, in-vitro study.

No lower bacterial adhesion for ceramics compared to other biomaterials: An in vitro analysis.

Although there is some clinical evidence of ceramic bearings being associated with a lower infection rate after total hip arthroplasty (THA), available data remains controversial since this surface is usually reserved for young, healthy patients. Therefore, we investigated the influence of five commonly used biomaterials on the adhesion potential of four biofilm-producing bacteria usually detected in infected THAs. Ceramic biomaterials exhibit less bacterial adherence than other biomaterials. In this in vitro research, we evaluated the ability of Staphylococcus aureus, Staphylococcus epidermidis ATCC 35984, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa to adhere to the surface of a cobalt-chromium metal head, a fourth-generation ceramic head, a fourth-generation ceramic insert, a highly-crossed linked polyethylene insert and a titanium porous-coated acetabular component. After an initial washing step, bacterial separation from the surface of each specimen was done with a vortex agitator. The colony-forming units were counted to determine the number of viable adherent bacteria. We found no differences on global bacterial adhesion between the different surfaces (p=0.5). E.coli presented the least adherence potential among the analysed pathogens (p<0.001). The combination of E.coli and S.epidermidis generated an antagonist effect over the adherence potential of S.epidermidis individually (58±4% vs. 48±5%; p=0.007). The combination of P.aeruginosa and S.aureus presented a trend to an increased adherence of P.aeruginosa independently, suggesting an agonist effect (71% vs. 62%; p=0.07). Ceramic bearings appeared not to be related to a lower bacterial adhesion than other biomaterials. However, different adhesive potentials among bacteria may play a major role on infection's inception. IV, in vitro study.

State-of-the-art on reconstruction of massive acetabular defects in revision total hip arthroplasty: a commentary on “Comparable results with porous metal augments in combination with either cemented or uncemented cups in revision hip arthroplasty: an analysis of one hundred forty seven revisions at a mean of five years”

Complex acetabular bone defects are challenging even for the most experienced hip reconstructive surgeons. Paprosky type IIIA and IIIB defects, which present both peripheral and cavitary deficiencies, can be managed with numerous options: high placement of porous-coated acetabular component; Burch-Schneider anti-protrusio cages; customized triflange cups; standard-size cemented or uncemented cups along with either bulk structural allograft, impaction grafting over a metal mesh, or metal augments and, more recently, tantalum trabecular-metal cups, frequently used as jumbo cups at our institution (with or without metal-porous augments).

Minimum Lateral Bone Coverage Required for Securing Fixation of Cementless Acetabular Components in Hip Dysplasia.

Objectives. To determine the minimum lateral bone coverage required for securing stable fixation of the porous-coated acetabular components (cups) in hip dysplasia. Methods. In total, 215 primary total hip arthroplasties in 199 patients were reviewed. The average follow-up period was 49 months (range: 24–77 months). The lateral bone coverage of the cups was assessed by determining the cup center-edge (cup-CE) angle and the bone coverage index (BCI) from anteroposterior pelvic radiographs. Further, cup fixation was determined using the modified DeLee and Charnley classification system. Results. All cups were judged to show stable fixation by bone ingrowth. The cup-CE angle was less than 0° in 7 hips (3.3%) and the minimum cup-CE angle was −9.2° (BCI: 48.8%). Thin radiolucent lines were observed in 5 hips (2.3%), which were not associated with decreased lateral bone coverage. Loosening, osteolysis, dislocation, or revision was not observed in any of the cases during the follow-up period. Conclusion. A cup-CE angle greater than −10° (BCI > 50%) was acceptable for stable bony fixation of the cup. Considering possible errors in manual implantation, we recommend that the cup position be planned such that the cup-CE angle is greater than 0° (BCI > 60%).

Cemented polyethylene and cementless porous-coated acetabular components have similar outcomes at a mean of seven years after total hip replacement

The aim of this prospective randomised study was to compare the clinical and radiological results of a cemented all-polyethylene Ultima acetabular component with those of a cementless porous-coated acetabular component (PFC) following total hip replacement (THR). A total of 287 patients received either a polyethylene acetabular component (groupA) or a cobalt-chromium porous-coated component (group B) with an identical cemented femoral component and 28 mm cobalt-chromium head, thus making it the largest study of its type. Patients were evaluated radiologically and clinically using the Harris hip score (HHS). Group A comprised 183 patients (73 male, 110 female) with a mean age of 71.3 years (55 to 89). Group B comprised 104 patients (48 male, 56 female) with a mean age of 69.8 years (56 to 89). A total of 16 patients (13 in Group A, three in Group B) did not have post-operative data for analysis. The mean follow-up in group A was 7.52 years (0.4 to 15.0) and in Group B 7.87 years (0.5 to 14.0). At final follow-up the mean HHS was similar between groups A and B (74.5 (25 to 100) and 78.0 (37 to 100), respectively; p = 0.068). The total number of revisions for any cause was 28, 17 of which were in group A and 11 in group B. The ten-year survivorship was 86.8% (95% confidence interval (CI) 78.4 to 92.1) and 89.2% (95% CI 78.3 to 94.8) for groups A and B, respectively (log-rank p-value = 0.938). A total of 20 cemented and two cementless acetabular components had evidence of acetabular radiolucencies or acetabular component migration at last follow-up (p = 0.001). These results indicate that patients with a cemented all-polyethylene and cementless porous-coated polyethylene lined acetabular component have similar long-term clinical outcomes.

The Acetabular Component in Primary Total Hip Arthroplasty

The cemented all-polyethylene acetabular component has almost completely been replaced by the cementless porous-coated acetabular component. A variety of different designs, incorporating several types of porous coatings, have proven to be reliable and durable. The ability to reposition a cementless cup to optimize component orientation allows the joint replacement surgeon to minimize impingement and maximize component stability. This is essential to prevent dislocation and damage to bearing surface of the acetabular component. Insertion of a hemispherical cementless cup with 1 mm of under-reaming typically allows for secure interference fit, good apposition of the implant to the underlying bone, an insignificant risk of pelvic fracture, and a rare risk of ingrowth failure.

Surgical Approaches to OA Therapy: Osteotomy and Arthroplasty

Total hip and knee replacement are among the most successful surgical procedures in medicine. The long-term survival of total hip replacements for which both the femoral and acetabular components were fixed to the surrounding bones with cement demonstrates durable results [1, 3], even in young patients [11]. For example, 35-year follow-up of cemented total hip replacements revealed a survival rate of 78% with the need for revision surgery for any reason as the end point [3]. In younger patients, the 25-year survival is 93% for the femoral component, though only 77% for the cemented acetabular component [11]. The introduction of newer designs that relies on biologic fixation through bone ingrowth into porous coatings on the metallic components has also proven durable. Twenty-year survival of porous-coated acetabular components has been reported at 86% [6] with revision for any reason associated with the acetabular component as the end point. In a direct comparison of cemented and cementless acetabular components performed by the same surgeon [8], survival at 18 years improved from 81% to 94%. Long-term results for porous-coated femoral components are just as impressive [2, 7, 9]. Joint replacement patients enjoy function which is comparable to their peers without osteoarthritis. Patient-reported outcomes such as the short-form health outcomes survey (the SF-36), together with objective functional measures, such as the 6-min walk, show no meaningful differences between total hip patients and normative values (Fig. 1). Fig. 1 SF-36 scores for total hip replacement patients (“Study”), those patients with two or more comorbidities, and normative values (“Norm”) demonstrate that total hip patients reach levels found in the normal age-matched population ... The major problem remaining in total hip replacement is the bearing surface. Osteolysis caused by the biological reaction to wear debris remains a common mode of failure. Considerable improvement has been made in the wear resistance of bearing surfaces, most recently by the widespread adoption of highly cross-linked polyethylene for acetabular components. Randomized clinical trials comparing cross-linked to conventional polyethylene show reductions in wear and osteolysis [13], though follow-up is not long enough at this time to determine the impact of these improvements on the need for revision surgery. Like total hip replacement, total knee replacement has similar durable results up to 10 to 20 years [4, 8–20]. Unicondylar knee replacement, in which only one compartment is replaced, has similar outstanding results, at least in older patients, though younger patients have not fared as well at long-term follow-up [17]. As with hip replacement, wear and osteolysis are major issues, particularly with modular designs for which backside wear between the polyethylene insert and the metallic tray provides an added source of debris [14]. This appears to apply especially in young, active osteoarthritis patients [16]. Similarly, mobile-bearing designs which incorporate a second bearing surface between the tibial insert and the tibial tray have an excellent long-term survival, but osteolysis secondary to an increased burden of wear debris appears to increase with time [4]. Cementless fixation has not gained acceptance in total knee replacement as it has in total hip replacement, despite promising long-term results [10]. Osteotomies are another surgical treatment for osteoarthritis, aimed at realigning joint surfaces and thus delaying disease progression. Newer procedures for osteotomies around the hip are encouraging at mid-term follow-up, with acceptable complications when performed by well-trained surgeons [5]. Knee procedures include closing and opening wedge osteotomies performed in the proximal tibia. Closing wedge osteotomies have produced unpredictable results that are not always durable [15]. Newer opening wedge osteotomies may provide more durable and more predictable results, but no long-term follow-up is available.

Dual Poly Liner Mobility Optimizes Wear and Stability in THA: Affirms

A dual-mobility acetabular component consists of a large, fixed, porous-coated acetabular component and a bipolar femoral component. These components are often called tripolar components. This configuration provides a stable, well-fixed implant platform against bone and 2 articular interfaces, a large polyethylene surface directly apposed to a highly polished metal implant, and a standard-sized (28- or 32-mm) femoral head captured within polyethylene. The dual-mobility cup appears to offer a safe, effective, durable solution to hip instability. The concept has extensive laboratory and clinical support. Although the long-term durability of these implants is unknown, the tested wear rates of a dual-mobility design with the current generation of highly cross-linked polyethylene are significantly lower than any previously reported wear rates. The recently introduced modular dual-mobility shell offers surgeons substantial flexibility in addressing the issue of hip instability with a cost-efficient, familiar option.

Migration pattern of cementless press fit cups in the presence of stabilizing screws in total hip arthroplasty

The aim of this study was to evaluate the initial acetabular implant stability and late acetabular implant migration in press fit cups combined with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary total hip arthroplasty. One hundred and seven hips were available for follow-up after primary THA using a cementless, porous-coated acetabular component. A total of 631 standardized radiographs were analyzed digitally by the "single-film-x-ray-analysis" method (EBRA). One hundred 'and one (94.4%) acetabular components did not show significant migration of more than 1 mm. Six (5.6%) implants showed migration of more than 1 mm. Statistical analysis did not reveal preoperative patterns that would identify predictors for future migration. Our findings suggest that the use of screw fixation for cementless porous- coated acetabular components for primary THA does not prevent cup migration.

Dual Mobility for Chronic Hip Instability: A Solution Option

A dual-mobility acetabular component consists of a large, fixed, porous-coated acetabular component and a bipolar femoral component. These components are often called tripolar components. This configuration provides a stable, well-fixed implant platform against bone and 2 articular interfaces, a large polyethylene surface directly apposed to the highly polished metal shell, and a standard sized (28 mm, 32 mm) femoral head captured within polyethylene. The dual-mobility cup was designed to reduce the incidence of dislocations in patients at increased risk of instability (eg, patients undergoing revision). The cup appears to offer a safe, effective, durable solution to hip instability. The concept has extensive laboratory and clinical support. Although the long-term durability of dual-mobility cups, particularly in young, active, large patients, is not known, the tested wear rates of the dual-mobility design with the current generation of highly cross-linked polyethylene are significantly lower than any previously reported wear rates. The recently released anatomic dual-mobility cup seeks to reduce the potential for iliopsoas impingement while retaining the stability and wear characteristics of the original dual-mobility design.

Porous-Coated Cementless Acetabular Components Without Bulk Bone Graft in Revision Surgery

We previously reported the average 9.3-year (range, 5-13 years) results of 74 patients (83 hips) with porous-coated acetabular components that were placed without bulk bone graft at revision surgery. Since the previous report, 7 patients (7 hips) died before the minimum follow-up of 10 years, and 1 patient (1 hip) was lost to follow-up. We now report the average 15.6-year (range, 10-20 years) results for 66 patients (75 hips). Three additional acetabular components were removed or revised again: 2 for infection and 1 for dislodgement of the polyethylene liner from the metal shell. Overall, 7 (7%) components required removal or repeat revision. No shell was revised for aseptic loosening, and none was categorized as loose during the entire follow-up period.

Polyethylene wear and osteolysis in H/G cementless total hip arthroplasty

To measure the linear polyethylene wear with use of a computer-assisted two-dimensional method, and to evaluate the relationship between wear and long-term clinic-radiological findings. Between December 1991 and December 1995, the senior author performed 40 primary total hip arthroplasties with use of H/G porous-coated acetabular component. Radiographs of 40 H/G cementless total hip arthroplasties were examined for osteolysis, radiolucent line, cup migration and so on. To measure the linear polyethylene wear, migration in the femoral head center relative to the cup shell center was calculated on digitized consecutive radiographs with special computer software program. The minimum follow-up was 10 years. Total linear wear was 2-8 mm, the mean rate of linear polyethylene wear was (0.32+/-0.31) mm/year. Twelve acetabular components (30%) were revised at an average follow-up point of 12 years. Three types of polyethylene liner failure were identified: wear-through of the polyethylene liner with resultant metallosis (5 hips), excessive wear necessitating revision (5 hips), and polyethylene liner dissociation without gross evidence of wear (2 hips). High wear rates and femoral and acetabular osteolysis have been and still are the main problems in uncemented total hip replacement. There is clear relationship between wear and acetabular osteolysis or loosening of the prostheses. The poor long-term results with these uncemented total hip arthroplasties illustrate the necessity of regular radiographic evaluation in order to detect osteolysis and liner failure, which are both generally asymptomatic until catastrophic failure appears.

Primary Total Hip Arthroplasty with a Porous-Coated Acetabular Component

We previously reported the seven and fifteen-year results of the use of a porous-coated acetabular metal shell inserted without cement in a consecutive series of 204 primary total hip arthroplasties. In the present study, we evaluated the longer-term outcomes of these arthroplasties at a minimum follow-up time of twenty years. One hundred and fourteen (92%) of the 124 hips available for study had retained the original acetabular metal shell. A total of five acetabular components had been revised for aseptic loosening or had radiographic evidence of definite loosening. Fourteen hips with well-fixed acetabular shells required a change of the modular acetabular liner because of excessive wear and/or for the treatment of osteolysis, and liner changes have been recommended for another eight hips. The twenty-year rate of survival of the metal shell, with failure defined as revision because of loosening or radiographic evidence of loosening, was 96% (95% confidence interval, 94% to 98%). Cementless acetabular reconstruction continues to provide durable fixation at twenty years postoperatively. Wear-related complications continue to be the major mode of failure.

Outcome of a hemispherical porous-coated acetabular component with a proximally hydroxyapatite-coated anatomical femoral component

We reviewed 111 hemispherical Duraloc series-500 acetabular components with a minimum follow-up of 12 years. The mean clinical and radiological follow-up was 13.4 years (12 to 15). A Profile hydroxyapatite-coated anatomical femoral component was used in each case. Six patients had a late dislocation, for whom the polyethylene liner was exchanged. Each acetabular component was well fixed and all femoral components showed signs of bone ingrowth. The mean rate of femoral head penetration was 0.10 mm/year (0.021 to 0.481). The probability of not developing femoral cortical hypertrophy and proximal osteopenia by 12 years was 80.2% (95% confidence interval, 72.7 to 87.6) and 77.5% (95% confidence interval, 69.7 to 85.2), respectively. Despite these good clinical results, further follow-up is needed to determine whether these prostheses will loosen with time.

Novel method to evaluate femoral head penetration in the polyethylene liner after total hip arthroplasty: three-dimensional evaluation on standing radiographs

BackgroundAfter total hip arthroplasty, the femoral head penetrates the liner because of polyethylene wear and the so-called bedding-in phenomenon. The head moves three-dimensionally, but few reports have evaluated such movement radiographically Moreover, even fewer reports have evaluated it in a standing position, although the load stress influences the movement. The purpose of the present study was to evaluate the head movement in the liner three-dimensionally using standing images. MethodThe distance between the centers of the metal shells and femoral heads were measured in 29 unilateral hips implanted with porous-coated acetabular components. Standing anteroposterior and lateral radiographs obtained approximately 2 years after operation were photographed by a digital camera, and the data were used. The measured distances divided by the time after operation and enlargement ratio of the radiographs gave linear penetration rates in the frontal and sagittal planes, and three-dimensional linear penetration rates were calculated from the penetration vectors. Frontally evaluated and three-dimensionally calculated penetration rates were compared, and the correlation of age and other factors with the penetration rate was evaluated. ResultsLinear penetration rates were 0.14 ± 0.11 mm/year frontally, 0.18 ± 0.08 mm/year sagittally, and 0.21 ± 0.10 mm/ year three-dimensionally. The mean three-dimensional penetration rate was 42% greater than the frontal rate. An inverse correlation was observed between age and the sagittal penetration rate (r = −0.621), and between age and the three-dimensional penetration rate (r = −0.388). The sagittal and three-dimensional penetration rates were significantly higher (P = 0.0008 and 0.0010, respectively) in patients aged <75 years compared to those aged ≥75 years. ConclusionsThe average three-dimensional penetration rate during the first 2 years after operation was markedly greater than the frontal two-dimensional penetration rate that was conventionally applied for postoperative evaluation. Three-dimensional evaluation using both frontal and sagittal radiographs is necessary to avoid undervaluation of the head movement after total hip arthroplasty.

Incomplete Seating of Press-Fit Porous-Coated Acetabular Components: The Fate of Zone 2 Lucencies

The purpose of this study was to asses the fate of incomplete seating of press-fit acetabular components. From 1990 to 2002, 587 hip arthroplasties were performed using a single-design acetabular component inserted with a press-fit technique with no additional fixation. Complete radiographic follow-up at a mean 9.2 years was available for 343 cases. One hundred thirty-three acetabular components had incomplete seating on the initial postoperative radiograph and 210 cases had complete seating. Of 133 components, 125 (94%) had evidence of complete zone 2 filling. Zone 2 focal osteolysis was present in 22 patients. There were no intraoperative fractures. No acetabular components were revised for loosening. Incomplete seating of press-fit acetabular components is safe and effective in achieving initial and long-term fixation. Zone 2 lucencies when present initially are not associated with increased failure risks. Vigorous attempts to completely seat the acetabular component appear to be unwarranted.