Cemented Polyethylene Research Articles

Computational assessment of the effect of polyethylene wear rate, mantle thickness, and porosity on the mechanical failure of the acetabular cement mantle

Clinical studies have revealed that aseptic loosening is the dominant cause of failure in total hip arthroplasty, particularly for the acetabular component. For a cemented polyethylene cup, failure is generally accompanied by the formation of fibrous tissue at the cement-bone interface. A variety of reasons for the formation of this tissue have been suggested, including osteolysis and mechanical overload at the cement-bone interface. In this study, a computational cement damage accumulation method was used to investigate the effect of polyethylene cup penetration, cement mantle thickness, and cement porosity on the number of cycles required to achieve mechanical fatigue failure of the cement mantle. Cup penetration was found to increase cement mantle stresses, resulting in a reduction in cement mantle fatigue life of 9% to 11% for a high cup penetration rate. The effect of using a thin (2 mm) over a thick (4 mm) cement mantle also reduced cement mantle fatigue life between 9% and 11%, and greatly raised cancellous bone stresses. Cement porosity was found to have very little effect on cement mantle fatigue life. Failure modes and cement stresses involved suggest that only extreme combinations of a thin cement mantle and high cup penetration may lead to mechanical failure of the cement mantle, thereby allowing wear debris access to the cement-bone interface. A thin cement mantle may also lead to the mechanical overload of the cement-bone interface. In this manner, the authors suggest that the mechanical factors may contribute to the failure mode of cemented polyethylene cups.

High hip center bipolar hemiarthroplasty for non-reconstructable pelvic discontinuity

A 79-year-old woman with bilateral lower extremity weakness due to cervical myelopathy presented at our department in 2002 after multiple reconstructive procedures in both hips for developmental dysplasia of the hip. In 1993, a bulk allograft in combination with an acetabular cage and a cemented cup were used to treat the left massive acetabular bone loss. The defect was type IVb by the classification of the American Academy of Orthopaedic Surgeons (D’Antonio et al. 1989) and Berry et al. (1999). In 2000, the acetabular construct failed mechani-cally while the existing cemented femoral stem remained well fixed (Figure 1A). Removal of the acetabular hardware was followed by implantation of a whole acetabular allograft. The allograft was stabilized with plates and screws, and a new cemented cup was inserted. 2 years later, allograft fracture and acetabular failure occurred again.In 2002, a high hip center bipolar hemiarthroplasty was per-formed via a standard posterior hip approach. Failed acetabu-lar component and hardware were removed but the femoral stem was left in situ as it was found to be stable. Capsular and periacetabular scar tissues were preserved as much as possible to create a soft tissue cavity to seat the bipolar head into. A 60-mm bipolar femoral head was inserted onto the femoral component to articulate with the periacetabular soft tissues in a high hip center mode. Its position was further augmented with capsular repair around the neck of the prosthesis (capsu-lar noose). A femoral condyle allograft was fixed to the ilium to serve as posterior superior acetabular wall. Postoperatively, the patient was advised to gradually increase her weight bearing using a walker or crutches. No casts or braces were applied. Within 6 months, the bipolar component migrated out of the acetabulum and articulated with the iliac soft tissues (Figure 1B). Although the patient had limb shortening, she had no pain and declined further surgery.The right hip required 7 reconstructive procedures, which led to pelvic discontinuity (type IVb) and resection arthroplasty in 1999 (Figure 1A). In 2000, a re-implantation was performed by using a reinforcement ring with a cemented polyethylene cup and a long cemented femoral prosthesis. 4 years later the was inserted onto the previously implanted and stable femo-ral stem and articulated with the soft tissues adjacent to the lateral ilium (Figure 1B). After surgery, the patient was able to transfer independently and ambulate short distances in her home with a walker.At 3 years postoperatively (right hip) and 5 years postop-eratively (left hip) the patient had no pain, relatively equal leg lengths, and could sit comfortably. Due to complete loss of lower extremity motor function associated with failed spine surgery and cervical myelopathy, the patient was non-ambu-latory. However, the Harris hip score (HHS) of the patient’s left hip had improved from 39 preoperatively to 58 postopera-tively. Similarly, the HHS of the patient’s right hip increased from 14 preoperatively to 58 postoperatively.

Long-term Radiographic Assessment of Cemented Polyethylene Acetabular Cups

In vitro studies demonstrating excessive wear in polyethylene cups sterilized using gamma irradiation and stored in air led to the abandonment of this sterilization technique. We evaluated the clinical wear performance of a metal femoral component on a polyethylene cup in a hip prosthesis from a selected subset of implants in a group of patients followed for at least 20 years and assessed the time dependency of variation in penetration rates. We measured penetration in 33 polyethylene cups in 25 patients who had a Charnley low-friction arthroplasty between 1982 and 1984. All patients had Charnley Ogee cups implanted for more than 20 years and sterilized using the gamma irradiation in air technique. If degradation occurred over time in vivo, it was not reflected by an increased penetration rate with increasing time in vivo; even after 20 years of implantation, the degree of wear remained low. This suggests gamma irradiation affects wear on ultra-high-molecular-weight polyethylene by reducing wear secondary to the crosslinking, by increasing wear as shown through in vitro studies of heavily oxidized samples, or by oxidation resulting from prolonged shelf life. The effect of progressive oxidation in vivo does not appear to affect wear in vivo. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Le frottement métal-métal en arthroplastie de hanche : aspect de matériovigilance

This study is dedicated to the problems met with metal-metal bearing prostheses. We have analysed the results of the reports sent to the AFSSAPS relating incidents described with this interface. Only 11 incidents were reported during the last 4 years by surgeons from different centers in France. At a mean follow-up of 7 years, we collected 2614 total hip arthroplasties with metal-metal bearings and among them only 5 cases of unusual osteolysis and 10 cases of impingement. The bibliographic analysis did not show any severe specific complication due to the release of Cobalt or Chromium ions. The increased levels of Co an Cr in the patients’ blood is now a well established notion (with more than 10 years follow up) and no special carcinogenetic effect has been correlated with the metal-metal bearings. Small diameter cemented cups can provide complications with high rates of acetabular loosening and metallosis; the same is true for some cementless cups also with loosening and a high revision rate. Among 143 hip prosthesis with a cemented polyethylene cup, at a mean follow-up of 42 months there were 22% of evolutive radiolucencies around the cups concerning all three De Lee and Charnley zones. Furthermore there was a statistically significant difference between small and large diameter cups (loosening of cups less than 46 mm in diameter). The same problem has been described for some cementless cups with loosening at the metal-bone interface due to a failure of osteointegration at the implant surface. However no failures were observed with an hydroxyapatite coating on the same cup. An other matter of concern is the skirted metal head: this design is responsible for a high rate of impingement and of prosthetic revision (2.3% among 642 THA). In these cases the increase of Cobalt serum levels was well correlated with the failure of the metal-metal interface. Large diameter heads decrease significantly the risks of dislocation. This is correlated with the increase in size. The release of ions in the blood was not affected by the large diameter compared to the regular size. So this overview confirms that if we respect some basic rules for the indications there are no specific complications related to the use of metal-metal bearings. In prospective studies the results of ceramic-ceramic and metal-metal bearings are similar but we must keep on observing prospectively the patients as for the release of Co and Cr.

Shoulder replacement: emerging trends

Purpose of review Total shoulder arthroplasty is a highly effective and predictable treatment for degenerative conditions of the glenohumeral joint. Improving implant survival by limiting complications, such as component loosening, has been the focus of a great deal of recent research. Recent findings Despite advances in component design and fixation, glenoid loosening remains a common indication for revision. Modern cement techniques, convex backing and pegged designs have been shown to improve radiographic results for cemented polyethylene components. Despite the theoretical advantage of permanent biologic fixation, metal-backed glenoid components have not had recent clinical success, and continued research in this area is necessary. Materials such as porous tanatalum may offer improved ingrowth fixation and increased component longevity. Humeral surface replacement is an alternative to traditional stemmed shoulder arthroplasty, and clinical studies are promising. Regional anesthesia is being used safely and effectively in shoulder surgery, and may allow shoulder arthroplasty to be performed on an outpatient basis. Summary The overall complication rate of total shoulder arthroplasty may be decreasing, but issues such as glenoid loosening remain problematic. Advances will aim to improve patient function and implant longevity. This review discusses current trends and areas of recent research in the field of shoulder replacement.

Patellar resurfacing in total knee replacement

A series of 100 consecutive osteoarthritic patients was randomised to undergo total knee replacement using a Miller-Galante II prosthesis, with or without a cemented polyethylene patellar component. Knee function was evaluated using the American Knee Society score, Western Ontario and McMaster University Osteoarthritis index, specific patellofemoral-related questions and radiographic evaluation until the fourth post-operative year, then via questionnaire until ten years post-operatively. A ten-point difference in the American Knee Society score between the two groups was considered a significant change in knee performance, with alpha and beta levels of 0.05. The mean age of the patients in the resurfaced group was 71 years (53 to 88) and in the non-resurfaced group was 73 years (54 to 86). After ten years 22 patients had died, seven were suffering from dementia, three declined further participation and ten were lost to follow-up. Two patients in the non-resurfaced group subsequently had their patellae resurfaced. In the resurfaced group one patient had an arthroscopic lateral release. There was no significant difference between the two treatment groups: both had a similar deterioration of scores with time, and no further patellofemoral complications were observed in either group. We are unable to recommend routine patellar resurfacing in osteoarthritic patients undergoing total knee replacement on the basis of our findings.

Bone remodelling around a cemented polyethylene cup

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery. The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years. Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.

Pitfalls in the use of acetabular reinforcement rings in total hip revision

For the reconstruction of acetabular bone defects different types of acetabular reinforcement rings are being used. In clinical practice, these implants showed to some extent good long-term results. In the present work pitfalls and complications after the implantation of acetabular reinforcement rings as well as possible solutions are being discussed. In the first case recurrent dislocation was caused by the malposition of the acetabular component with an impingement of the protruding bone cement and the anterior edge of the acetabular ring as well as muscle insufficiency as a result of the shortening of the leg length. The second case revealed an impingement of the iliopsoas tendon due to a protruding acetabular reinforcement ring. During revision, bone cement was used to smoothen the protruding anterior edge of the acetabular reconstruction ring in order to obtain a relieved sliding of the tendon. Furthermore, we report on the case of a delayed neuropathy of the sciatic nerve after reconstruction of the acetabulum with an acetabular reinforcement ring. Intraoperatively an impingement of the sciatic nerve at the protruding dorsal edge of the acetabular reinforcement ring and the surrounding scar tissue was found. In a further case an aseptic loosening of an acetabular reinforcement ring caused the formation of an excessive granuloma with a large intrapelvic portion. The granuloma led to persisting senso-motoric deficits of the femoral nerve. In summary, based on these clinical cases possible pitfalls, associated with the use of acetabular reinforcement rings, are shown. The mal-positioning and the intra-operative re-shaping of the implant by the surgeon are pointed out as the substantial factors for the occurrence of an impingement phenomenon and total hip instability. Furthermore, in case of an adequate orientation of the cemented polyethylene insert an improper position of the acetabular ring which results in protruding edges has to be considered as a cause of a prosthetic impingement. The cases presented emphasize the necessity of prevention of such pitfalls intra-operatively as well as accurate analysis of implant failures. Furthermore, they suggest explicit preoperative planning before deciding on the strategy of revision surgery of acetabular reinforcement rings.

Radiographic and Computed Tomography Analysis of Cemented Pegged Polyethylene Glenoid Components in Total Shoulder Replacement

Glenoid loosening continues to be the primary reason for failure of total shoulder arthroplasty. The purpose of this study was to evaluate, with use of a sensitive and reproducible imaging method, the radiographic and clinical results of total shoulder replacement with a pegged, cemented polyethylene glenoid implant. Forty-three patients (forty-seven shoulders) underwent a total shoulder replacement with a cemented polyethylene glenoid component with four threaded pegs. The patients were examined clinically, with fluoroscopically guided radiographs, and with computed tomography at an average of forty months. In addition to conventional scoring of radiographic lucency, an 18-point scoring system was used to quantify cement-peg lucencies in six zones of the back surface of the glenoid component as seen on computed tomography scans. On the average, the absolute Constant score improved from 39 points preoperatively to 70 points at the time of follow-up (p = 0.0001) and the pain score improved from 5 to 13 points (p = 0.001). The mean active anterior elevation improved by 34 degrees (p = 0.001) and the mean abduction, by 46 degrees (p = 0.006). Two patients had symptomatic glenoid loosening requiring revision. Twenty-one of the forty-seven shoulders had radiographic lucency around the glenoid pegs, and nine had progression of the lucency by at least two grades. Computed tomography detected lucencies, primarily at the bone-cement interface, in thirty-six shoulders. The scores for the lucencies seen on the computed tomography scans were associated with the radiographic lucency scores (p < 0.001), pain scores (p = 0.04), and abduction strength (p = 0.02). Computed tomography was more sensitive than radiography with regard to identifying the number of pegs associated with lucency and the size of the lucencies. The overall reproducibility of the scoring based on the computed tomography was higher than that of the radiographic scoring. Computed tomography provided a more sensitive and reproducible tool for the assessment of loosening of pegged glenoid components than did fluoroscopically guided conventional radiography. Further improvement in implant design and fixation technique appears to be necessary for long-term success of cemented glenoid components.

RADIOGRAPHIC AND COMPUTED TOMOGRAPHY ANALYSIS OF CEMENTED PEGGED POLYETHYLENE GLENOID COMPONENTS IN TOTAL SHOULDER REPLACEMENT

Background: Glenoid loosening continues to be the primary reason for failure of total shoulder arthroplasty. The purpose of this study was to evaluate, with use of a sensitive and reproducible imaging method, the radiographic and clinical results of total shoulder replacement with a pegged, cemented polyethylene glenoid implant. Methods: Forty-three patients (forty-seven shoulders) underwent a total shoulder replacement with a cemented polyethylene glenoid component with four threaded pegs. The patients were examined clinically, with fluoroscopically guided radiographs, and with computed tomography at an average of forty months. In addition to conventional scoring of radiographic lucency, an 18-point scoring system was used to quantify cement-peg lucencies in six zones of the back surface of the glenoid component as seen on computed tomography scans. Results: On the average, the absolute Constant score improved from 39 points preoperatively to 70 points at the time of follow-up (p = 0.0001) and the pain score improved from 5 to 13 points (p = 0.001). The mean active anterior elevation improved by 34° (p = 0.001) and the mean abduction, by 46° (p = 0.006). Two patients had symptomatic glenoid loosening requiring revision. Twenty-one of the forty-seven shoulders had radiographic lucency around the glenoid pegs, and nine had progression of the lucency by at least two grades. Computed tomography detected lucencies, primarily at the bone-cement interface, in thirty-six shoulders. The scores for the lucencies seen on the computed tomography scans were associated with the radiographic lucency scores (p < 0.001), pain scores (p = 0.04), and abduction strength (p = 0.02). Computed tomography was more sensitive than radiography with regard to identifying the number of pegs associated with lucency and the size of the lucencies. The overall reproducibility of the scoring based on the computed tomography was higher than that of the radiographic scoring. Conclusions: Computed tomography provided a more sensitive and reproducible tool for the assessment of loosening of pegged glenoid components than did fluoroscopically guided conventional radiography. Further improvement in implant design and fixation technique appears to be necessary for long-term success of cemented glenoid components. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Uncemented Glenoid Component in Total Shoulder Arthroplasty&lt;sbt aid="1012619"&gt;Survivorship and Outcomes&lt;/sbt&gt;

Glenoid component loosening continues to be a major factor affecting the long-term survivorship of total shoulder replacements. Radiolucent lines, cement fracture, migration, and loosening requiring revision are common problems with cemented glenoid components. The purpose of this study was to evaluate the results of total shoulder arthroplasty with an uncemented glenoid component and to identify predictors of glenoid component failure. One hundred and forty-seven consecutive total shoulder arthroplasties were performed in 132 patients (mean age, 63.3 years) with use of an uncemented glenoid component fixed with screws between 1988 and 1996. One hundred and forty shoulders in 124 patients were available for follow-up at an average of 7.5 years. One shoulder in which the arthroplasty had failed at 2.4 years and for which the duration of follow-up was four years was also included for completeness. The preoperative diagnoses included osteoarthritis in seventy-two shoulders and rheumatoid arthritis in fifty-five. Radiolucency was noted around the glenoid component and/or screws in fifty-three of the 140 shoulders. The mean modified ASES (American Shoulder and Elbow Surgeons) score (and standard deviation) improved from 15.6 +/- 11.8 points preoperatively to 75.8 +/- 17.5 points at the time of follow-up. Eighty-five shoulders were not painful, forty-two were slightly or mildly painful, ten were moderately painful, and three were severely painful. Fifteen (11%) of the glenoid components failed clinically, and ten of them also had radiographic signs of failure. Eleven other shoulders had radiographic signs of failure but no symptoms at the time of writing. Three factors had a significant independent association with clinical failure: male gender (p = 0.02), pain (p < 0.01), and radiolucency adjacent to the flat tray (p < 0.001). In addition, the annual risk of implant revision was nearly seven times higher for patients with radiographic signs of failure. Clinical survivorship was 95% at five years and 85% at ten years. The failure rates of the total shoulder arthroplasties in this study were higher than those in previously reported studies of cemented polyethylene components with similar durations of follow-up. Screw breakage and excessive polyethylene wear were common problems that may lead to additional failures of these uncemented glenoid components in the future.

The effect of geometry and abduction angle on the stresses in cemented UHMWPE acetabular cups – finite element simulations and experimental tests

BackgroundContact pressure of UHMWPE acetabular cup has been shown to correlate with wear in total hip replacement (THR). The aim of the present study was to test the hypotheses that the cup geometry, abduction angle, thickness and clearance can modify the stresses in cemented polyethylene cups.MethodsAcetabular cups with different geometries (Link®: IP and Lubinus eccentric) were tested cyclically in a simulator at 45° and 60° abduction angles. Finite element (FE) meshes were generated and two additional designs were reconstructed to test the effects of the cup clearance and thickness. Contact pressures at cup-head and cup-cement interfaces were calculated as a function of loading force at 45°, 60° and 80° abduction angles.ResultsAt the cup-head interface, IP experienced lower contact pressures than the Lubinus eccentric at low loading forces. However, at higher loading forces, much higher contact pressures were produced on the surface of IP cup. An increase in the abduction angle increased contact pressure in the IP model, but this did not occur to any major extent with the Lubinus eccentric model. At the cup-cement interface, IP experienced lower contact pressures. Increased clearance between cup and head increased contact pressure both at cup-head and cup-cement interfaces, whereas a decreased thickness of polyethylene layer increased contact pressure only at the cup-cement interface. FE results were consistent with experimental tests and acetabular cup deformations.ConclusionFE analyses showed that geometrical design, thickness and abduction angle of the acetabular cup, as well as the clearance between the cup and head do change significantly the mechanical stresses experienced by a cemented UHMWPE acetabular cup. These factors should be taken into account in future development of THR prostheses. FE technique is a useful tool with which to address these issues.

Inter- and intraobserver assessment of periacetabular osteodensitometry after cemented and uncemented total hip arthroplasty using computed tomography

This study was initiated to evaluate the reproducibility of a novel method for measuring the periacetabular bone density after insertion of cemented and uncemented acetabular cups using CT in vivo. CT scans were obtained from 20 patients after cemented polyethylene cup implantation (ZCA, Zimmer, USA) and 20 patients after uncemented titanium alloy cup fixation (Cerafit, Ceraver, France). A manual segmentation of cancellous and cortical pelvic bone ventral, dorsal and cranial to the cup was undertaken. Values are given in Hounsfield units. Inter- and intraobserver studies were conducted using a special analysis software tool. To define the reproducibility of the method, all measurements were evaluated according to Bland and Altman. For both cemented and uncemented acetabular cups, reproducibility of bone density measurement for cortical and cancellous bone cranial, ventral and dorsal to the cup was high. There was no significant difference between the intraobsever study (two repeated measurements) and the interobserver study (two investigators), indicating the reproducibility of the method independent of the investigator. In conclusion, the periacetabular bone density measurement as conducted in this CT study is a new reproducible method for in vivo evaluation of cortical and cancellous pelvic bone after cemented and uncemented acetabular cup implantation. In vivo CT measurements will allow a thorough assessment of periacetabular stress-shielding phenomena.

Total Shoulder Arthroplasty With an Uncemented Glenoid Component

Progressive radiolucencies, radiographic failure, and clinical loosening requiring revision remain a concern with cemented polyethylene glenoids. The purpose of this study was to evaluate the results associated with the use of an uncemented glenoid component during total shoulder arthroplasty. Eighty-two consecutive total shoulder arthroplasties in 73 patients were performed using an uncemented glenoid component. Seventy-seven shoulders in 69 patients (40 females and 29 males) were available for follow-up. Diagnoses included osteoarthritis in 44 shoulders, rheumatoid arthritis in 29, and avascular necrosis in 4 shoulders. The mean age at TSA was 65.8 years (S.D. = 9.7, range 37-89). The average duration of follow-up was 6.5 years (S.D. = 2.7, range 3.5-10 years). Radiolucencies were noted around the glenoid component and/or screws in 45% of shoulders. Modified ASES scores improved from 18.4 ± 10.4 preoperatively to 77.6 ± 16.5 at follow-up (P < 0.0001). Ten of the glenoids (13.1%) had clinical failure, and 8 of these glenoids also had radiographic failure. Four significant independent predictors of clinical failure were noted on multivariate analysis: male gender (P = 0.02), pain (P < 0.01), major cuff tear (P < 0.008), and radiographic failure (P < 0.001). Clinical survivorship according to Kaplan-Meier method was 98% at 5 years, 83% at 8 years, and 77% at 10 years. Radiographic survivorship was 98% at 5 years and 79% at 10 years. While the radiographic and functional results of total shoulder arthroplasty utilizing an uncemented glenoid component appear to be comparable to those of cemented polyethylene components, both clinical and radiographic failure are an ongoing concern and mandate continued close scrutiny.

Acetabular Reconstruction with Impaction Bone-Grafting and a Cemented Cup in Patients Younger Than Fifty Years Old

Acetabular bone deficiency can present a challenge during total hip arthroplasty, especially in young patients. The purpose of the present study was to evaluate the long-term clinical and radiographic outcomes of primary and revision acetabular reconstruction with use of an impaction bone-grafting technique and a cemented polyethylene cup in young patients who had preexisting acetabular bone deficiency. Forty-two consecutive acetabular reconstructions were performed in thirty-seven patients who were younger than fifty years old (average, 37.2 years old). The impaction bone-grafting technique was used for twenty-three primary and nineteen revision acetabular reconstructions. Twenty-eight patients (thirty-one hips) were available for review after a minimum duration of follow-up of fifteen years. Clinical and radiographic results were assessed, and survivorship analysis was performed with the Kaplan-Meier method. Eight hips were revised at a mean of twelve years (range, three to twenty-one years) after a primary reconstruction (four hips) or revision reconstruction (four hips). The revision was performed because of aseptic loosening of the acetabular component in four hips and because of culture-proven septic loosening in two. Two additional cups (both in hips that had had a revision reconstruction) were revised, during revision of the femoral stem, because of wear (one hip) or because of persistent intraoperative instability (one hip). Twenty-eight hips (in twenty-five patients) had retention of the acetabular component for a minimum of fifteen years. The mean Harris hip score for that group was 89 points. Twenty-six of these twenty-eight hips had no or slight pain. Kaplan-Meier analysis revealed a twenty-year survival rate of 80% (95% confidence interval, 67% to 94%) with acetabular revision for any reason as the end point and of 91% (95% confidence interval, 80% to 100%) with acetabular revision because of aseptic loosening as the end point. Acetabular reconstruction with use of impaction bone-grafting and a cemented polyethylene cup is a reliable and durable technique that is associated with good long-term results in young patients with acetabular bone-stock defects.

Secondary stability of cemented and non-cemented acetabular implants ex-vivo under dynamic load

To measure the bone-prosthetic implant interface micromovement during the application of physiological load by using a material testing system (MTS). The cadaveric hip specimens were used to simulate a single leg stance and the joint in the neutral position. Micromovement was recorded via a 3-dimensional transducer in the acetabula of postmortem specimens, which had been preserved in formalin. The study data of the cemented and uncemented prosthsis refereed to the lone-term clinical process and the radiological status and experimental results. Cemented cups showed higher transverse relative motion up to 90 microm, whereas the maximum transverse movement of the non-cemented cup was 60 microm. Orthogonal motion perpendicular to the implant surface showed compression for all cups at all sites. The results indicate that there are large differences in survival time between 2 groups. That could not be compared statistically in secondary stability. Nevertheless, according to the results, the amount of micromotion of press-fit cup is relatively less than that of cemented polyethylene cup, which is instrumental in bone ingrowth and secondary stability.

Ten-Year Results with Hydroxyapatite-Coated Total Hip Femoral Components in Patients Less Than Fifty Years Old

To The Editor: I read with great interest “Ten-Year Results with Hydroxyapatite-Coated Total Hip Femoral Components in Patients Less Than Fifty Years Old” (2003;85:885-9), by Capello et al. I would like to thank the authors for their resolve to publish, together with the good results for the femoral component, the bad results for the cup component. The manufacturer of the Omnifit prosthesis has been concerned that the results of the cup and stem components would be published together, as witnessed by the discussion between the representative of the manufacturer and the board of the Swedish National Hip Arthroplasty Registerl. For the patient, every revision of a total hip replacement is equally unfortunate, be it a revision of the stem or the cup component. Waiting for any kind of revision operation produces equally severe preoperative anguish and stress in the patient. From this perspective, I would like to ask the authors the following questions: First, I believe that the survival of only 53.8% of all cup components during ten years postoperatively is so exceptionally low for a modern total hip prosthesis that the figure should be mentioned in the abstract together with the name of the cup model. I would like to know why the authors abstained from publishing this figure in the abstract. Second, the authors did not publish the combined revision rates for both components of this prosthesis. Was it because the combined revision rates of this prosthesis (for any reason) probably exceeded 50% during the ten years of follow-up? Third, the authors presented nice survivorship “curves” (life tables) for the cup components. Visual assessment of these “curves” indicates that the failure rate of the cup components accelerates with time. In comparison, two recent publications on the twenty-five-year results of cemented monoblock polyethylene total hip … Corresponding author: William N. Capello, MD Department of Orthopaedic Surgery Indiana University School of Medicine Clinical Building, Suite 600 541 Clinical Drive Indianapolis, IN 46202-5111 wcapello{at}iupui.edu

Acetabular revision with impacted morselized cancellous bone graft and a cemented cup in patients with rheumatoid arthritis: three to fourteen-year follow-up.

Acetabular revision in patients with rheumatoid arthritis is often difficult because of the poor quality and quantity of the acetabular bone stock. The purpose of this study was to evaluate the midterm clinical and radiographic outcomes of acetabular revision with use of an impaction bone-grafting technique and a cemented polyethylene cup. Thirty-five consecutive acetabular revisions were performed with impaction bone-grafting and use of a cemented cup in twenty-eight patients with rheumatoid arthritis. The average age at the revision was fifty-seven years. The minimum duration of follow-up of all reconstructions that were still functioning or that were followed until the time of death was three years (mean, 7.5 years; range, three to fourteen years). No patient was lost to follow-up, but five patients (six hips) died before the time of the review. The acetabular bone defects were classified as cavitary in twelve hips and as combined segmental-cavitary in twenty-three. The five patients (six hips) who died had been doing well at the time of their latest follow-up. Of the remaining patients, six (six hips) had a repeat revision. The average Harris hip score of the living patients with a surviving implant at the time of follow-up was 82 points, and there was no or only mild pain in twenty-one of the twenty-three hips. Radiographic analysis of all twenty-nine hips that had not been revised showed loosening in one hip and a nonprogressive radiolucent line in one zone in two others. Kaplan-Meier analysis demonstrated a prosthetic survival rate, with aseptic loosening as the end point, of 90% at eight years. Acetabular revision with impaction bone-grafting and a cemented cup in patients with rheumatoid arthritis had acceptable results at an average of 7.5 years postoperatively.

Retrieval Study of Total Hip Arthroplasty with Use of a Cemented Polyethylene Cup and a Non-cemented Polyethylene Liner in Combination with Zirconia Ceramic Femoral Head: Report of 2 Cases

Catastrophic failure of a zirconia head with Hylamer acetabular component and early failure due to the phase transformation of zirconia ceramic head after total hip arthroplasty have been indebted issues. We report two cases who had failure of the zirconia ceramic head with polyethylene articulations shortly after total hip arthroplasty. Revision retrieval studies were performed subsequently.

Revision of polyethylene acetabular liners with a cemented polyethylene cup: A laboratory study

Various technique parameters for the revision of failed polyethylene acetabular liners using a cemented polyethylene cup were evaluated in this laboratory study. The effects of cement mantle thickness and roughening the inner surface of the shell or outer surface of the cup were determined by measuring cup dissociation strength from the metal shell after cyclic loading of the cup. The use of a cement mantle thickness of 2 to 4 mm provided dissociation strengths 3 to 4 times greater than that of the original, press-fit polyethylene liner. If a failed acetabular liner is revised by a cemented cup within the existing, well-fixed, metal shell, the size of the cup selected should create a cement mantle of <4 mm. Roughening the inside of a smooth shell or one with few screw-holes increases fixation strength approximately 20% but also creates particulate debris. Copyright 2002, Elsevier Science (USA). All rights reserved.