Showing papers in "Journal of Arthroplasty in 2005"

Obesity and Perioperative Morbidity in Total Hip and Total Knee Arthroplasty Patients

Abstract: The incidence of obesity in 1071 total hip arthroplasty (THA) patients and 1813 total knee arthroplasty (TKA) patients and its effect on perioperative morbidity were evaluated prospectively. Fifty-two percent of TKA and 36% of THA patients were obese (body mass index ≥30). The obese patients were significantly younger, with a higher proportion of obese TKA patients being women. Higher rates of diabetes and hypertension were found in obese patients. Higher postoperative infection rates were observed in patients with body mass index 35 or higher. The odds ratio was 6.7 times higher risk for infection in obese TKA patients and 4.2 times higher for obese THA patients. The increased risk of infection in obese patients undergoing total joint arthroplasty must be realized by both the patient and surgeon.

Periprosthetic femoral fractures classification and demographics of 1049 periprosthetic femoral fractures from the Swedish National Hip Arthroplasty Register.

Abstract: Postoperative femoral periprosthetic fracture is an uncommon complication of total hip arthroplasty surgery, but several centers worldwide have recently reported an increase in total numbers of such fractures. This severe complication is costly for society and results in high morbidity. Our analysis of 1049 periprosthetic fractures occurring in Sweden between 1979 and 2000 and recorded in the Swedish National Hip Arthroplasty Register focuses on patient- and implant-related factors, fracture classification, and fracture frequency. These were our 3 major findings: (1) a majority of the patients who sustained a late periprosthetic femoral fracture had a loose stem. (2) Implant-related factors are significantly associated with occurrence of a periprosthetic fracture. (3) Since the 1980s in Sweden, treatment results for periprosthetic fractures have been poor, with low long-term survivorship and a high frequency of complications. We have initiated further studies of this important problem.

Range of Motion and Stability in Total Hip Arthroplasty With 28-, 32-, 38-, and 44-mm Femoral Head Sizes An In Vitro Study

Abstract: The purpose of this study was to evaluate, via experimental models, the effect of larger head sizes for total hip arthroplasty on the type of impingement, range of motion (ROM), and joint stability. Testing was conducted using an anatomic full-size hip model (anatomic goniometer) and a novel anatomic dislocation simulator with 28-, 32-, 38-, and 44-mm diameter femoral heads within a 61-mm acetabular shell. Femoral heads >32-mm provided greater ROM and virtually complete elimination of component-to-component impingement. A significant increase in both flexion before dislocation and displacement between the femoral head and acetabulum to produce dislocation occurred with femoral heads >32-mm in diameter. These data indicate that larger femoral heads offer potential in providing greater hip ROM and joint stability.

Long-Term Results of Total Condylar Knee Arthroplasty

Abstract: From 1979 to 1984, 126 consecutive Total Condylar (Howmedica, Rutherford, NJ) knee arthroplasties were performed at a hospital in Taiwan, of which 64 knees were available for evaluation. The patients' average weight was 58 kg. The average Hospital for Special Surgery knee score at the latest follow-up was 86 points. Using revision for mechanical failure as an end point, the 20-year overall survival was 91.9%. The survival for the all-polyethylene tibial component was 96.4% and for the metal-backed tibial component was 88.4%. The difference was statistically significant (P < .001). We recommend the use of the more cost-effective and durable all-polyethylene tibial component for a primary cemented total knee arthroplasty, particularly in Asians with a relatively low weight and who are relatively inactive, especially in elderly people.

Leg axis after computer-navigated total knee arthroplasty: a prospective randomized trial comparing computer-navigated and manual implantation.

Abstract: To compare the alignment after computer-navigated total knee arthroplasty, 52 patients were randomly allocated to 2 groups. Twenty-seven patients received a total knee arthroplasty with the aid of a kinematic computer-navigation system, and 25 patients received a total knee arthroplasty with the conventional method. Both groups were well balanced concerning demographic data and preoperative scores. At 3-month follow-up, the mechanical alignment of the leg reached the desired straight axis in more cases with the computer-navigated implantation. This difference was statistically significant. The femoral and tibial mechanical anteroposterior axis and the femoral and tibial sagittal tilt (slope) measured on sagittal x-rays were not significantly improved in this patient group.

Reconstructed hip joint position and abductor muscle strength after total hip arthroplasty.

Abstract: We evaluated 60 limbs in 30 patients with unilateral primary total hip arthroplasty and nondiseased contralateral hip. The ratio of femoral offset (FO) to the body weight lever arm (FO ratio) and the ratio of the height of hip center (HC) to pelvic height (HC ratio) were calculated on radiographs. Isometric hip abductor strength was measured by dynamometer. The ratio of normalized strength of the reconstructed side to that of the nonoperated side was calculated (strength ratio). The FO ratio correlated positively to the strength ratio (r = 0.491; P = .0059), whereas the HC ratio correlated negatively (r = -0.568; P = .0011). Slight increase of FO ratio along with restoration of normal hip joint center erring on the side of slight inferomedial cup positioning appeared to optimize hip abductor function.

Computer assisted navigation in total knee arthroplasty: comparison with conventional methods.

Abstract: The success of knee arthroplasty is dependent on many factors. Postoperative extremity and component alignment are important determinants of outcome and longevity. Malalignment (>3 degrees ) results in higher failure rates. Computer-assisted navigation devices were developed to improve implant positioning. This study evaluated the early outcomes of a high-volume fellowship-trained surgeon relative to component positioning and limb alignment using an image-free navigation system. The navigation group consisted of 116 consecutive patients, and the conventional group consisted of 51 consecutive patients. The postoperative mechanical axis was within 3 degrees of neutral mechanical alignment in 95% of the navigation cases vs 84% of the conventional cases (P < .02). The range of the alignment and component position measurements narrowed, and the undesired outliers decreased. Accuracy was improved with navigation. Navigation was a viable device to improve the outcome of total knee arthroplasty relative to limb and component alignment.

Randomized control trial comparing radiographic total knee arthroplasty implant placement using computer navigation versus conventional technique.

Abstract: The aim of this study is to assess the radiological outcome of conventional techniques versus computer-navigated surgery for total knee arthroplasty. Ninety patients with knee arthritis were prospectively randomized into 3 groups: conventional technique: extramedullary (EM) and intramedullary (IM) tibia guide versus computer navigation surgery (CAS). Two surgeons performed all procedures. Standardized long leg coronal and sagittal x-rays were evaluated by a blinded assessor. Our results showed that CAS had greater consistency and accuracy in implant placement. In the coronal view, 93.3% in the CAS group had better outcomes compared with EM (73.4%) and IM (60.0%). In the sagittal axis, 90.0% CAS also had better outcomes compared with EM (63.3%) and IM (76.7%). Computer-navigated total knee arthroplasty helps increase accuracy and reduce "outliers" for implant placement.

Consistency of implantation of a total knee arthroplasty with a non-image-based navigation system: a case-control study of 235 cases compared with 235 conventionally implanted prostheses.

Abstract: The aim of the study was to assess the consistency of the non–image-based navigation system OrthoPilot®, Aesculap, Tuttlingen, Germany, in total knee arthroplasty (TKA) implantation in 5 European centers Two hundred thirty-five TKAs implanted with this navigation system were matched (according to severity of the preoperative coronal deformation and body mass index) to a historical control group of 235 TKAs implanted with a conventional technique Consistency of implantation was studied on a 3-month postoperative radiological control with coronal long-leg and sagittal standard x-rays The use of the OrthoPilot® navigation system allowed a statistically significant improvement in the consistent placement of both tibial and femoral components In accordance with current literature, survival of the navigated implanted prostheses is expected to be longer

Outpatient total knee arthroplasty with a minimally invasive technique.

Abstract: Fifty consecutive patients were enrolled in this prospective study. This was 37% of the 135 patients undergoing primary total knee arthroplasty (TKA) by one surgeon. The average patient age was 68 years (50-79 years). A comprehensive perioperative management pathway was developed and was implemented, which combined regional anesthesia with a minimally invasive, TKA technique in which the only incision in the capsule and extensor mechanism is a capsular incision from the joint line to the superior pole of the patella. Postoperatively, patients received oral analgesia. After specific discharge criteria were met, 48 patients (96%) chose to go home the day of surgery. No intraoperative complications occurred. There were 3 readmissions, none related to early discharge: gastrointestinal bleed at 8 days, superficial irrigation and debridement at 21 days, and a closed manipulation at 9 weeks. This study demonstrates that, in these selected patients, outpatient TKA was safe with no short-term readmission or complications related to early discharge. This comprehensive pathway may make it possible for this minimally invasive TKA to be done as an outpatient in specialized surgicenters in the future.

Impingement in total hip arthroplasty a study of retrieved acetabular components.

Abstract: Impingement can damage the acetabular liner, create polyethylene wear, and cause dislocation. We determined the prevalence of impingement, its relation with dislocation, and the influence of patient, surgical, and design factors in 162 components randomly selected from a larger group retrieved between 1990 and 1999. Impingement arc, severity, and wear damage were measured; patient data were obtained from medical records, and component position was determined from radiographs. More than half (56%) showed impingement, including 94% of those removed for dislocation. The occurrence of impingement was significantly increased if the revision diagnosis was dislocation, if the component had a large outer diameter or an elevated rim, and if the femoral component had an extended flanged neck. Implant design, in particular head/neck ratio, can help reduce the prevalence of impingement.

Health Outcome Measures in the Evaluation of Total Hip Arthroplasties—A Comparison Between the Harris Hip Score and the Oxford Hip Score

Abstract: There has been an increasing need for the sensitive and reproducible measurement of the outcome after hip surgery. Numerous hip scoring systems, varying in their complexity and disease specificity, have been designed to achieve a measure of outcome-some rely ultimately on the judgement of the surgeon, whereas others rely on the patients' perceptions. The Oxford hip score (OHS) has been found to be easier to administer and achieves a much higher follow-up rate than that of the Harris hip score (HHS). Unfortunately, with the availability of numerous scoring systems and the publication of data in these systems, it has been difficult to compare results. Our aim was to compare the more widely used HHS to the shorter OHS. We followed 200 consecutive primary total hip arthroplasties (196 patients between January 1994 and May 1995) for an average of 5 years. All patients had a preoperative HHS recorded. At the 5-year review, assessment was made using OHS and the HHS. There were 115 hips that had full OHS and HHS available. The mean OHS was 19.1 (range 12-52, SD 9.5), and HHS was 89.4 (range 47-100, SD 13.3) at follow-up. The Spearman correlation showed good negative correlation between the 2 results (Spearman rank -0.712, P 33) outcomes which correlate well with the HHS. This study enables the case for the Oxford data with its easier analysis and higher compliance rate to be used more directly to compare studies that use the HHS.

In vivo comparative wear study of traditional and highly cross-linked polyethylene in total hip arthroplasty.

Abstract: In this study, we compare the in vivo wear performance of electron beam–irradiated, postirradiation-melted, highly cross-linked polyethylene (HXLPE) and traditional UHMWPE via the Martell method. Seventy hips with HXLPE performed at the Massachusetts General Hospital had 138 radiograph pairs for wear analysis and a 31.2-month average follow-up (range, 24-44 months). An age-matched, sex-matched, and body mass index–matched subgroup of 111 hips with 214 acceptable radiograph pairs and a 4-year follow-up from our previously published study on traditional polyethylene performed at Rush-Presbyterian–St. Luke's Medical Center served as a control group. Martell wear analysis was performed for each group. Overall and steady-state wear rates were compared via a specialized t test. The steady-state wear in the HXLPE arm was observed after 2.0 years, was 0.007 mm/y, and was significantly less than the steady-state wear in the traditional arm (0.174 mm/y) ( P = .003). Highly cross-linked polyethylene penetration rate was not affected by sex, age, activity, or body mass index by Mann-Whitney analysis.

The Functional Flexion-Extension Axis of the Knee Corresponds to the Surgical Epicondylar Axis: In Vivo Analysis Using a Biplanar Image-Matching Technique

Abstract: We investigated the concept that the knee has a fixed flexion-extension axis in the posterior femoral condyles and that this functional axis corresponds to the surgical epicondylar axis in vivo. We used a biplanar image-matching technique to perform the in vivo analysis of 9 normal knees to determine the location of the functional flexion-extension axis of the knee using an optimization technique. The functional flexion-extension axis passed through the sulcus of the medial epicondyle and the prominence of the lateral epicondyle. Flexion and extension of the knee could be represented as a rotation around a fixed axis, and this functional axis corresponded to the surgical epicondylar axis during a 0° to 90° flexion. This study assists more understanding of knee kinematics and provides useful information for the design and positioning of the prostheses used in total knee arthroplasty.

Evaluation of a porous tantalum uncemented acetabular cup in revision total hip arthroplasty: clinical and radiological results of 60 hips.

Abstract: Long-term survival of the acetabular component in revision total hip arthroplasty (THA) is determined by initial implant stability and bone ingrowth. Highly porous Trabecular Metal (TM, Zimmer, Inc, Warsaw, Ind) facilitates ingrowth and may be an ideal material for revision THA. The outcome and survivorship of a TM, nonmodular, uncemented acetabular cup were assessed in 60 consecutive patients undergoing revision THA (mean follow-up, 42 months; range, 14-68 months). Most (55/60) acetabular cups were implanted without screw fixation. Mean Harris Hips Scores improved from 74.8 preoperatively to 94.4 at last follow-up. Serial radiographs demonstrated excellent bone apposition and bone graft incorporation. Complications were limited to 7 cases of dislocation and 1 revision for aseptic loosening. The TM acetabular cup appears suitable for use in revision THA and warrants further study.

Metal-on-Metal total hip replacement: what does the literature say?

Abstract: Second-generation metal-on-metal (M/M) total hip replacements were introduced into clinical use in the late 1980s and demonstrate equivalent survivorship to conventional metal-on-polyethylene prostheses. Wear rates are comparable to those of first-generation designs that survived for a long time in the body. Biological effects from metal ions remain a concern. Patients with both first- and second-generation M/M hips have higher levels of cobalt and chromium in their blood and urine than either patients with metal-on-polyethylene devices or unoperated patients. Concerns include the potential for acquired hypersensitivity, mutagenicity, and carcinogenicity. However, reports of proven adverse effects are scant. Prospective, randomized trials with follow-up in excess of 15 years will be needed to differentiate between the performance and effects of M/M and other bearing combinations. Key words: totalhip arthroplasty, metal-on-metal, wear, biological effects, clinical results.

The Long-term Outcome of 755 Consecutive Constrained Acetabular Components in Total Hip Arthroplasty: Examining the Successes and Failures

Abstract: Constrained acetabular components can treat or prevent instability after total hip arthroplasty (THA). We examine long-term results of 755 consecutive constrained THA in 720 patients (1986-1993; 62 primary, 59 conversion, 565 revision, 60 reimplantation, and 9 total femur). Eighty-three patients (88 THAs) were lost before 10-year follow-up, leaving 639 patients (667 THAs) available for study. Dislocation occurred in 117 hips (17.5%), in 37 (28.9%) of 128 constrained for recurrent dislocation, and 46 (28.2%) of 163 with dislocation history. Other reoperations were for aseptic loosening (51, 7.6% acetabular; 28, 4.2% stem; 16, 2.4% combined), infection (40, 6.0%), periprosthetic fracture (19, 2.8%), stem breakage (2, 0.3%), cup malposition (1, 0.1%), dissociated insert (1, 0.1%), dissociated femoral head (1, 0.1%), and impingement of 1 broken (0.1%) and 4 (0.6%) dissociated constraining rings. Although constrained acetabular components prevented recurrent dislocation in 71.1%, they should be used cautiously, with a 42.1% long-term failure rate observed in this series. Dislocation was common despite constraint with previous history as a significant risk.

The early results of high-flex total knee arthroplasty: a minimum of 2 years of follow-up.

Abstract: We retrospectively reviewed our first 25 cases of high-flex total knee arthroplasty (TKA) with an average follow-up of 28 months. The results were compared to a matched group of posterior stabilized (PS) TKA. There was no significant difference in Knee Society Scores between the 2 groups. The high-flex group had an averaged 138 degrees of knee flexion, which was significantly higher than the PS group (average, 126 degrees). Eighty percent of patients in high-flex group were able to squat, which was significantly higher than in PS group (32%). In patients with a small bone frame, occasionally, their bone stock of the posterior femoral condyle is inadequate for high-flex TKA. For the patients without special demands, the additional knee flexion from high-flex design made no significant difference on the results.

Computer assisted navigation in total knee arthroplasty: improved coronal alignment.

Abstract: The use of a computer navigation system is intended to optimize implant positioning This study compares prospectively followed total knee arthroplasty (TKA) done with imageless computer-assisted navigation with a cohort of TKA done with manual instruments Primary TKAs were performed on 147 knees, with 78 in the manual group and 69 in the navigated group Coronal alignment was determined by postoperative full-length standing radiographs The 2 groups had similar mean values for radiographic mechanical axis at 04° There was a larger variation in alignment in the manual group, with 58% of the manual group within 2° of neutral compared with 78% of the navigated group ( P = 008) The navigation system reproducibly resulted in a more reliable reproduction of the mechanical axis

In Vivo Kinematic Comparison of Posterior Cruciate-Retaining and Posterior Stabilized Total Knee Arthroplasties Under Passive and Weight-Bearing Conditions

Abstract: An in vivo comparison of flexion kinematics for posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasty (TKA) was performed. Twenty patients who underwent bilateral paired TKAs were included in this prospective study. Both PCR and PS prostheses were from the same TKA series with comparable surface geometries, and all were implanted by a single surgeon. Of these 20 patients, 3-dimensional kinematics during flexion could be analyzed using a computer model fitting technique in 18 patients. The follow-up period ranged from 18 to 53 months. In the PCR TKA, an anterior femoral translation from 30 degrees to 60 degrees of flexion was observed in the weight-bearing condition. In contrast, flexion kinematics for the PS TKA was characterized by the maintenance of a constant contact position under weight-bearing conditions and posterior femoral rollback in passive flexion.

The precision and usefulness of preoperative planning for cemented and hybrid primary total hip arthroplasty.

Abstract: We evaluated the utility of a preoperative planning technique with a review of preoperative radiographs, templates, plans, charts and 6-week postoperative radiographs of 139 total hip arthroplasties (THAs) (116 cemented and 23 hybrid) to determine size, orientation of the implants, and cement column mantle, location of the planned and achieved center of rotation, and limb-length discrepancy. The acetabular component size was predicted exactly in 116 hips (83%) (within +/-1 size in 138 hips [99%]); the femoral component size was predicted exactly in 108 hips (78%) (within +/-1 size in 138 [99%]). In 75 arthroplasties (45%), the center of rotation was within 2 mm of horizontal and vertical distance from the plan, and in 127 (91%) arthroplasties, it was within 4 mm. The inclination of the cup averaged 44 degrees (range, 30 degrees -58 degrees ). The stem was in a neutral alignment in 122 hips (88%), varus in 11 hips (8%), and in 2 degrees of valgus in 6 hips (4%). In 103 arthroplasties with a normal contralateral hip or a THA, the average limb-length discrepancy was 1.71 mm. Preoperative planning is useful to predict the implant size, position, and alignment, to restore the center of rotation, and to equalize limb length.

Comparison of Mobile-Bearing and Fixed-Bearing Total Knee Arthroplasty: A Prospective Randomized Study

Abstract: The purpose of this prospective randomized study was to compare the postoperative recovery and early results of 2 groups of patients undergoing total knee arthroplasty: 107 patients received an established fixed-bearing posterior- stabilized prosthesis (Legacy Posterior Stabilized (LPS)), and 103 patients the meniscal-bearing prosthesis (Meniscal Bearing Knee (MBK)). Surgical procedures were the same for both groups except for posterior cruciate ligament management, which was sacrificed in the LPS group and spared but completely released from the tibia in the MBK group. At an average follow-up of 36 months, knee, function, and patellar scores were comparable in both groups. The LPS group showed a significantly higher maximum flexion than the MBK group (1128 vs 1088). Using a fixed-bearing or a mobile-bearing design did not seem to influence the short-term recovery and early results after knee arthroplasty. Key words: total knee arthroplasty, mobile bearing, knee prosthesis, meniscal-bearing knee, posterior stabilized, prospective randomized. n 2005 Published by Elsevier Inc.

Ten-year experience using an articulating antibiotic cement hip spacer for the treatment of chronically infected total hip.

Abstract: Infection is a devastating complication after total-hip arthroplasty. Between June 1991 and December 2001, 42 patients were treated at our center for chronically infected total-hip arthroplasty using a 2-stage articulating antibiotic hip spacer technique. Of the 27 patients available for review, 26 (94%) remain clinically free of infection at an average 76 months (range, 28-148 months) postoperatively. Twenty-two (81%) patients had a positive identification of the infecting organism. All patients received a minimum of 6 weeks of intravenous antibiotics and the Harris Hip Scores improved from 53 (range, 36-68) to 92 (range, 81-99) postoperatively. Advantages of this technique include improved patient function, maintenance of bone stock and soft tissue tension, thus simplifying reimplantation.

The infected total knee: management options.

Abstract: The management of infection after total knee arthroplasty depends on the chronicity of the infection, host factors, and sensitivity of the infecting bacteria. Two-stage salvage consisting of removal of implants and cement, placement of an antibiotic spacer, and appropriate intravenous antibiotic therapy followed by reimplantation with an antibiotic-impregnated cement appears to be the predominant approach to managing this complication. The use of articulated spacers consisting of the sterilized femoral and polyethylene components with antibiotic cement allows maintenance of motion and bone stock. This report details the author's experience with 44 infected knee arthroplasties.

Simultaneous bilateral versus unilateral total hip arthroplasty an outcomes analysis.

Abstract: This study compared the morbidity, mortality, and outcomes of 900 simultaneous bilateral total hip arthroplasties in 450 patients and 450 unilateral total hip arthroplasties. Pulmonary complications were significantly higher in the simultaneous bilateral group (1.6% vs 0.7%; P < .0312). Fourteen (3.1%) patients in the simultaneous bilateral group and 18 (4%) patients in the unilateral group died within the first postoperative year. Patients with mortality in the first postoperative year were significantly older (69.8 vs 62.3 years; P < .0012). Long-term patient survival, the prosthetic survival, and functional outcomes were not significantly different between groups. Simultaneous bilateral total hip arthroplasty has advantages where both hips are symptomatic and has less risk in younger patients with understanding of the increased risk of pulmonary complications.

Total knee arthroplasty for profound varus deformity: technique and radiological results in 173 knees with varus of more than 20 degrees.

Abstract: One hundred seventy-three knees in 117 patients with varus deformity exceeding 20° were prospectively evaluated. Using selective posteromedial release, reduction osteotomy of posteromedial tibial flare, and extra-articular tibial osteotomy, with the preservation of medial collateral ligament integrity, mean tibiofemoral angle of 22.7° varus preoperatively (range, 15°-62°) was corrected to 5.3° valgus (range, 2°-9°) postoperatively. Eighty-six percent of the knees were in 4° to 10° valgus postoperatively. Mean Knee Society score improved from 22.8 (range, 0-64) to 91.1 (range, 52-99), and function score from 22.8 (range, 0-64) to 72.1 (range, 5-100) at 2.6 years (range, 2-9 years). Mean femoral component valgus was 95.5° (range, 92°-98°), and mean tibial component valgus was 89.8° (range, 86°-94°). Of 30 grafts for posteromedial tibial defects, 28 were successfully incorporated. No patient reported significant instability. Three knees (1.7%) showed tibial component loosening with recurrence of deformity. Correction of severe varus deformity by the technique reported can successfully restore alignment, pain-free motion, and stability.

Clinical results in valgus total knee arthroplasty with the "pie crust" technique of lateral soft tissue releases.

Abstract: Numerous methods for creating symmetric flexion and extension gaps during knee arthroplasty in valgus knees have been proposed, and no consensus exists about the optimal technique. The “pie crust” technique for lateral soft tissue releases has been used extensively, yet few clinical results have been published. In this study, the clinical outcomes of 24 consecutive knees in 24 patients in whom this method was used in conjunction with a cemented posterior-stabilized prosthesis were evaluated. At a mean of 54 months' (range 24-69 months) follow-up, the knees were performing well with a mean Knee Society score of 97 (range 87-100) and mean range of motion of 121° (range 100°-145°). Importantly, there were no clinical failures or cases of postoperative instability and no cases of radiographic loosening or wear.

High failure rate of a constrained acetabular liner in revision total hip arthroplasty

Abstract: Fifty-five consecutive revision total hip arthroplasties (THAs) in 51 patients in which a constrained acetabular liner was used (Duraloc Constrained Liner, DePuy, Warsaw, Ind) were reviewed. In these revisions, 41 constrained liners were placed for recurrent instability and 14 for inadequate stability at the time of revision THA. The mean age of the cohort was 62 years, and 38 of the hips were in female patients (69%). At a minimum of 2 years, 9 of the 55 hips (16%) dislocated. Of these 9 dislocations, 8 occurred in patients who had undergone revision to a constrained liner for recurrent instability without femoral or acetabular component revision. Revision THA for recurrent instability by placing a constrained liner without optimizing other aspects of the reconstruction leads to a high rate of recurrent failure.

Radiographic evaluation of a monoblock acetabular component: a multicenter study with 2- to 5-year results.

Abstract: Serial radiographs of a porous tantalum monoblock acetabular cup design were evaluated for cup stability and signs of successful osteointegration. Of 574 primary consecutive total hip replacements in 542 patients performed by 9 surgeons at 7 hospitals, 414 cases were available for minimum 2-year follow-up. Follow-up averaged 33 months and ranged from 24 to 58 months. Postoperative radiographs revealed acetabular gaps in 100 zones in 80 (19%) hips: 29 in zone I, 67 in zone II, and 4 in zone III. At last follow-up, 84 (84%) of the zones with gaps completely filled in, and all 4- and 5-mm gaps filled in. There was no progression of any postoperative gap, no evidence of continuous periacetabular interface radiolucencies, no evidence of lysis, and no revisions for loosening. Although these short-term results are encouraging, further follow-up will be required to assess whether the monoblock design and the low modulus of elasticity of porous tantalum will reduce the incidence of periacetabular stress shielding and occurrence of osteolysis.

Long-term results with cementless Fitek (or Fitmore) cups.

Abstract: Fitek cementless cups have been adopted in our department in 1989. The first 100 consecutive Fitek implants were analyzed clinically (Harris hip score) and radiographically (anteroposterior and lateral x-rays) with a mean follow-up of 9.7 years. We did not have any case of cup loosening or any other problem requiring cup revision. In this series, we had 86 excellent, 10 good, 2 fair, and 2 poor results. The 2 poor results were because of 2 cases of aseptic loosening of the stem (1 cemented and 1 cementless). The x-rays showed an average angle of cup inclination of 36.5 degrees (range 16 degrees -54 degrees ) after surgery and no variations at the last follow-up. Bidimensional linear wear of the acetabular component showed 6 cases of measurable wear with an average wear rate per year of 0.265 mm. The overall wear rate per year was 0.02 mm. At the time of the last follow-up examination, we had 3 femoral osteolysis and no case of acetabular osteolysis. In our series, we observed "lack of contact" zones above the polar depression in 71 cases immediately after surgery. The average thickness of these lines was 1 (range 0.5-3.5) mm. Of these, at the last follow-up, 61 cases (86%) showed a complete "filling" of the "lack of contact," whereas in 10 (24%), the "filling" was incomplete (4 cases still showing a radiolucent line [