Wear of polyethylene against oxidized zirconium femoral components effect of aggressive kinematic conditions and malalignment in total knee arthroplasty

Metallic femoral components with ceramic articulating surfaces can substantially lower polyethylene (PE) wear during walking activities under conditions of normal knee alignment. It is unknown whether these types of components can maintain low wear rates under conditions of knee malalignment and the harsher kinematics associated with younger, athletically active patients. Wear was measured in non-cross-linked, ethylene oxide-sterilized PE inserts against oxidized zirconium or cobalt-chrome femoral components in a knee wear simulator. The vertical load was modified to replicate knee varus malalignment of 3°, and the range of tibial rotation was increased to 20°. Mean gravimetric and volumetric wear rate over 5 million cycles was 55% lower in the oxidized zirconium group. An oxidized zirconium femoral component can significantly reduce PE wear under simulated conditions of athletically active patients with modestly malaligned total knee arthroplasty prostheses.     

Retrieval Analysis of Femoral Zirconium Components in Total Knee Arthroplasty : Preliminary Results

Safety of oxidized zirconium (OxZr) in total knee arthroplasty (TKA) has been supported by biomechanical, clinical, and radiologic data. Retrieved OxZr femoral components and corresponding polyethylene (PE) inserts were examined to rule out patterns leading to early failure. Sixteen retrieved TKA with an OxZr femoral component were included. The PE inlays were analyzed applying an established scoring system for wear and surface damage. Femoral components were screened for scratching, pitting, delamination, and striations. The prostheses were in situ for 16.4 ± 11.9 months. The average wear and damage score for the tibial PE inserts was 36.0 ± 12.7. The average score in the visual analysis of the OxZr femoral components was 1.3 ± 1.3. The data presented in this study did not show major wear of the PE in TKA using OxZr components. In this cohort, there were no failures directly related to this implant.     

Factors affecting the severity of backside wear of modular tibial inserts

BACKGROUND: The use of modular tibial components in total knee arthroplasty introduces a possible source of polyethylene wear at the nonarticulating (backside) surface. However, it is not known whether this phenomenon is an incidental finding observed in unique specimens or is a feature common to all modular components. The purpose of this study was to determine the type and severity of backside wear in retrieved tibial inserts of several common total knee designs. METHODS: One hundred and twenty-four polyethylene tibial inserts of twelve different designs were retrieved at revision total knee replacements after implantation periods ranging from zero to 180 months. Each insert was visually inspected with use of a stereomicroscope for seven different modes of surface damage in four quadrants defining the backside surface. RESULTS: Pitting, burnishing, and measurable polyethylene protrusions were observed on the backside of polyethylene inserts of implant designs with a variety of different capture mechanisms. Across all implant designs, pitting was observed in 90% of the retrieved specimens; burnishing, in 77%; and protrusion, in 61%. Overall, implants of the IB-II (Insall-Burstein-II) design (Zimmer) exhibited the most severe burnishing, whereas those of the Duracon design (Howmedica) had the most severe pitting. Severe protrusions were noted with inserts of one design (AMK [Anatomic Modular Knee]; DePuy). A longer time in situ was associated with larger polyethylene protrusions, but the severity of pitting and burnishing did not increase with increasing duration of implantation. CONCLUSIONS: Moderate-to-severe wear of the nonarticulating surface of the tibial insert was frequently observed in all designs of knee prostheses, independent of the capture mechanism. These results indicate that new designs of modular tibial components are needed to prevent the generation of polyethylene wear debris through backside wear of total knee replacements.     

二期翻修治疗膝关节肿瘤型人工关节感染

目的探讨二期翻修术治疗膝关节肿瘤型人工关节感染的疗效。方法 2003年8月-2010年8月,收治22例保肢术后膝关节肿瘤型人工关节感染患者。男11例,女11例;年龄15～55岁,平均29.6岁。其中20例为初次关节置换术后感染,2例为翻修术后;术后15 d～89个月发生感染。感染按照Coventry和Fitzgerald等人工关节感染分型标准:Ⅰ型3例,Ⅱ型15例,Ⅲ型4例。发生感染至该次入院时间为5～47个月,平均10.2个月。细菌培养提示阳性9例,阴性13例。2例出现发热,白细胞计数升高。一期清创术取出假体,临时骨水泥填充旷置;待感染控制后行二期翻修。结果一期清创术前C反应蛋白及红细胞沉降率均明显高于二期翻修术前,差异有统计学意义(P<0.05)。术后患者均获随访,随访时间5～63个月,平均23.6个月。一期清创术后18例(81.8%)感染控制,其中1例拒绝二期翻修,17例行二期翻修术;17例中1例因术后5个月感染复发,行截肢术。4例(18.2%)感染未控制,行截肢术。保肢率为77.3%(17/22)。1例肾癌骨转移患者因原发病于术后1年6个月死亡。末次随访时16例关节功能采用美国骨与软组织肿瘤学会功能评分(MSTS 93)为(69.4±12.7)分。结论肿瘤型人工关节重建后感染,应根据情况及时行二期翻修手术,可获得较好疗效。     

Bone Loss During Revision of Unicompartmental to Total Knee Arthroplasty : An Analysis of Implanted Polyethylene Thickness From the National Joint Registry Data

Using the National Joint Registry (UK) database, we compared the thickness of polyethylene (PE) and the level of constraint used during primary total knee arthroplasty (TKA) versus the revision of unicondylar knee arthroplasty (UKA) to TKA. A total of 251,803 TKA procedures and 374 revision UKA–TKA procedures between 2003 and 2009 were reviewed. The commonest PE size used in TKA was 10 mm, compared to 12.79 mm in the revision group. The use of constrained knee implant was required in 2.15% of primary TKA and 4.19% of UKA to TKA revisions. The revision of UKA to TKA is a more complex procedure compared to primary TKA, with a higher incidence of using constrained implants and thicker PE inserts. These findings may be useful for surgeons in their decision making.     

Polyethylene thickness is a risk factor for wear necessitating insert exchange

Purpose

The aim of this observational study was to investigate the optimal minimal polyethylene (PE) thickness in total knee arthroplasty (TKA) and identify other risk factors associated with revision of the insert due to wear.

Methods

A total of 84 TKA were followed for 11–16 years. All patients received the same prosthesis design (Interax; Howmedica/ Stryker) with halfbearings: separate PE-inserts medially and laterally. Statistical analysis comprised Cox-regression to correct for confounding.

Results

Eight knees (9.5%) had been revised due to thinning inserts and an additional patient is scheduled for revision. PE thickness, diagnosis, BMI and weight are risk factors for insert exchange. For each millimetre decrease in PE thickness, the risk of insert exchange increases 3.0 times, which remains after correction for age, gender, weight, diagnosis and femoral-tibial angle. Insert exchange was 4.73 times more likely in OA-patients compared to RA-patients. For every unit increase in BMI and weight the risk for insert exchange increases 1.40 times and 1.14 times, respectively.

Conclusions

In conclusion we therefore advise against the use of thin PE inserts in modular TKA and recommend PE inserts with a minimal 8-mm thickness.     

No Detectable Polyethylene Wear 15 Years After Implantation of a Mobile–Bearing Total Knee Arthroplasty With Electron Beam–Irradiated Polyethylene

BackgroundThe present study was designed to evaluate the risk of significant polyethylene (PE) wear 10 years or more after implantation of a total knee arthroplasty (TKA) using electron beam–irradiated highly cross-linked PE component.MethodsAll patients operated between 2001 and 2004 for implantation of this particular TKA in the two participating centers were eligible for this study. All patients were contacted after the 10-year follow-up for repeat clinical examination and radiological evaluation. The occurrence of a revision prior to the final evaluation and its reason were recorded. The thickness of the PE piece was measured on plain X-rays.ResultsFive hundred seventy-eight TKAs were implanted during the study time-frame. One hundred sixteen patients deceased prior to the 10-year follow-up (20%). An additional 121 patients were lost to follow-up prior to the 10-year follow-up (21%). Complete follow-up at 10 years or more (including death or revision) was obtained for 448 cases (78%). Ten prosthetic revisions were performed for mechanical reasons during the follow-up time (2%). One single revision was performed because PE wear after 13 years. No significant PE wear was detected at the final radiographic evaluation for nonrevised cases. The 10-year survival rate for mechanical revision only was 98.0% and decreased to 96.2% at 15 years.ConclusionThe use of electron beam–irradiated PE was associated with an extremely low incidence of wear. This technology may be considered as safe regarding PE behavior for TKA after more than 10 years. Further improvement of PE manufacturing may be not required.     

Clinical and radiographic results of the total condylar III and constrained condylar total knee arthroplasty

The Total Condylar III (Johnson and Johnson, Braintree, MA) and Constrained Condylar (Zimmer, Warsaw, IN) knee prostheses are nonlinked, semi-constrained prosthetic alternatives to rigid or rotating hinge prostheses for use in complex knee reconstructions. Forty-six Total Condylar III or Constrained Condylar prostheses were implanted with cement in 36 patients and followed for a mean of 5 years (range, 2–9 years). There were 25 primary total knee arthroplasties and 21 revision total knee arthroplasties. The knees were evaluated using The Hospital for Special Surgery 100-point knee rating system. Overall, 40 knees (87%) had a good or excellent clinical result, 2 knees (4%) had a fair result, and 4 knees (9%) had a poor result. There was one revision for loosening of a cemented, nonmodular Constrained Condylar prosthesis, and one knee had a debridement for a late, metastatic infection, but the components were retained. There were no mechanical failures in those knees that were primary arthroplasties, but two mechanical failures occurred in those knees that were revision arthroplasties. Radiographic review showed one asymptomatic loosening of a Constrained Condylar tibial component with an uncemented press-fit stem, and only 8 knees had scattered nonprogressive tibial bone—cement radiolucent lines. The Total Condylar III and Constrained Condylar semiconstrained prostheses are successful when used in complex knee reconstructions.     

Polyethylene wear of metal-backed tibial components in total and unicompartmental knee prostheses.

We examined 86 polyethylene inserts, retrieved from total and unicompartmental knee prostheses after an average of 39.5 months in situ, grading them from 0 to 3 for seven modes of polyethylene degradation. Severe wear, with delamination or deformation, was observed in 51% of the implants, and was associated with time in situ, lack of congruency, thin polyethylene, third-body wear debris, and heat-pressed polyethylene. Significant under-surface cold flow was identified in some areas of unsupported polyethylene, and was associated with delamination in the load-bearing areas of thin inserts above screw holes in the underlying metal tray. We recommend the use of thicker polyethylene inserts, particularly in young, active patients and in designs with screw holes in the tibial baseplate. Thin polyethylene inserts which are at risk for accelerated wear and premature failure should be monitored radiographically at annual intervals.     

Oxidized zirconium femoral components reduce polyethylene wear in a knee wear simulator

Polyethylene wear remains a major problem that can jeopardize the long-term durability of prostheses used in total knee arthroplasty. Oxidized zirconium is a material that combines the strength of a metal with the wear properties of a ceramic. This study evaluated the wear rates of polyethylene inserts against oxidized zirconium femoral components. Three oxidized zirconium femoral components and three Co-Cr femoral components of identical geometry used in total knee arthroplasty were articulated against standard tibial components with modular tibial inserts made of noncross-linked ultra-high molecular weight polyethylene. Gravimetric and volumetric polyethylene wear rates were calculated after 5 million gait cycles on an AMTI knee wear simulator. Oxidized zirconium reduced polyethylene wear by 42% compared with Co-Cr alloy. This study shows that oxidized zirconium can reduce polyethylene wear substantially when used for fixed-bearing total knee arthroplasty.     

Clinical results of modular polyethylene insert exchange with retention of total knee arthroplasty components

BACKGROUND: Modular polyethylene inserts have enabled surgeons to perform an isolated tibial insert exchange while retaining well fixed components. The purpose of this study was to review the results of insert revision and to clarify the role of this option compared with that of revision total knee arthroplasty. METHODS: Fifty-six patients (sixty-three knees) were managed with revision of a tibial polyethylene insert and retention of well aligned and stable femoral and tibial components. The implants had been in situ for an average of fifty-nine months (range, two to 108 months) at the time of the insert exchange. The inserts that were removed at the time of exchange were evaluated with regard to wear of the articular surface according to the classification system of Hood et al. and with regard to undersurface wear according to the method described by Wasielewski et al. Forty-eight knees were followed for an average of 7.4 years (range, 3.0 to 12.2 years) after the insert exchange. Knees that did not require an additional operation were considered to have had a successful exchange. RESULTS: Seven of the forty-eight exchanges failed, at an average of fifty-four months, because of accelerated wear of the new insert. All seven knees required complete revision of all components. Of the twenty-two exchanges that were performed because of severe wear of the primary insert, six (27 percent) failed at an average of less than five years; thus, knees in which the exchange was performed because of advanced wear were more likely to fail again (p < 0.05). In addition, primary inserts that were removed from knees in which the exchange procedure subsequently failed had higher delamination scores than those that were removed from knees in which the exchange was successful (p < 0.05). Most of the primary inserts had substantial undersurface wear at the time of the exchange procedure. Metallosis (thirty knees) and osteolysis (nineteen knees) were unrelated to failure of the exchange. CONCLUSIONS: An isolated revision of the tibial polyethylene insert should not be performed when there is accelerated wear of the insert with severe delamination and grade-3 or 4 undersurface wear within ten years after the primary procedure. Because a variety of patient-related, implant-related, and technical factors influence polyethylene wear, the orthopaedist must consider multiple variables whenever contemplating a limited revision.     

Prediction of total knee arthroplasty polyethylene wear using the wear index

The predictive value of the wear index for total knee arthroplasty polyethylene wear was determined using a numeric and in vitro model. The wear index was defined as the deformation x the sliding velocity. Four commercially available total knee prostheses were modeled for this study. Deformation and sliding velocity were calculated from the 3-dimensional geometry of the components and the gait kinematic inputs using Hertz's formula. A knee simulation test was performed under the same conditions, and the surface of the inserts was compared with the wear index. This study showed good agreement between the numeric model and the simulation test, suggesting that the wear index is a reliable predictor of total knee arthroplasty polyethylene wear through its incorporation of contact stress and kinematics.     

Achskorrektur bei Knietotalendoprothesenrevisionen

Implant malalignment is a major cause for early loosening, increased wear, painful limitation of motion, and patient dissatisfaction in total knee arthroplasty. Validated diagnostic algorithms and a deeper understanding of the pathological mechanisms underlying functional deficits and pain resulting from malalignment explain the increasing number of revision operations on unloosened prostheses, which are now nearly as common as revisions for implant loosening. Common reasons are component malpositioning are a shifted joint line, or a non-physiological patella position. The success of any revision procedure basically depends on: (1) correct component positioning, (2) equal and symmetrical flexion and extension gaps, (3) restoration of joint line, and (4) a physiological patella height. The adequate grade of implant constraint has to be determined intra-operatively. A higher loosening rate of constrained implants as well as increased wear and painful limitation of motion in case of instability have to be taken into account.In the present work, a diagnostic and therapeutic algorithm for malalignment of knee prostheses is presented.     

Long-term results of low contact stress mobile-bearing total knee replacements

Five hundred ninety-eight consecutive primary low contact stress total knee replacements were done in 502 patients between 1985 and 1990. Clinical review was available for 495 knees (406 patients), 228 knees with meniscal-bearing prostheses and 267 knees with rotating-platform prostheses. The average followup was 12 years (range, 10-15 years). The average postoperative knee and functional scores were 87 points and 75 points, respectively. The average postoperative range of motion was 110 degrees. Fifty-six knees (11%) required revision for excessive wear of the tibial insert (41), dislocation (10), patellar polyethylene breakage (one), component loosening (one patellar, one tibial), and infection (two). During revision, osteolysis (20 knees), patellar polyethylene failure (33), and femoral component fracture (one) were seen. The overall survivorship was 88.1% at 15 years using Kaplan-Meier analysis. The survival rate was 83% for the meniscal-bearing prostheses and 92.1% for the rotating-platform prostheses. The Low Contact Stress mobile-bearing knee prosthesis has no superiority over that of fixed-bearing knees, especially for the meniscal-bearing design in prevention of polyethylene failure or revision. Based on the results of this study, the use of the LCS meniscal-bearing prosthesis does not appear to be justified.     

Linear and volumetric wear of tibial inserts in posterior cruciate-retaining knee arthroplasties.

Linear and volumetric wear was measured in 33 tibial polyethylene inserts from three different cruciate-retaining knee systems retrieved at the time of revision surgery. Wear patterns also were evaluated and classified. Eccentric and asymmetric wear patterns were seen in 78% of inserts with flat articulating geometry versus 12% in inserts with curved anteroposterior geometry. The mean linear wear rate was .35 mm/year (range, .05-1.68 mm/year) and the mean volumetric wear rate was 794 mm3/year (range, 24-4088 mm3/year). Linear and volumetric wear rates showed a negative correlation with the length of implantation. Linear wear rates also showed a negative correlation with patient weight.     

Ceramic versus cobalt-chrome femoral components; wear of polyethylene insert in total knee prosthesis

The present study aimed to determine the effect of femoral component materials and sterilization methods on wear properties of total knee prostheses by using a knee simulator test and retrieval analysis. The simulator test revealed that ultrahigh molecular weight polyethylene (UHMWPE) inserts had remarkably lower wear against the ceramic femoral component than against the Co-Cr femoral component. However, the retrieval study revealed no significant difference in the linear wear between the former and the latter. The alumina ceramic/UHMWPE insert combination showed a mild wear. However, whether cross-linking by gamma-ray sterilization reduces wear remained unconfirmed. In contrast, oxidative degradation and/or delamination was confirmed. Thus, we conclude that alumina ceramic/ethylene oxide gas-sterilized UHMWPE insert in a total knee prosthesis might exhibit a good wear resistance.     

Analysis of wear and oxidation on retrieved bipolar polyethylene liner

BACKGROUND: For bipolar prostheses, most of the previous studies attributed the occurrence of osteolysis to wear debris generated from the bearing surface. We looked closely into the wear debris and reported on our findings with respect to the oxidation index and the rate of wear in ultra-high molecular weight polyethylene (UHMWPE) inserts retrieved from bipolar prostheses after various spans of time in vivo. METHOD: The inserts were retrieved from the heads of three types of bipolar prosthesis (UH1, UPF1, UPF2). We retrieved 24 bipolar prostheses from 23 patients whose mean implantation period was 10.0 years (2.7-15.4 years). RESULTS: All the retrieved polyethylene had a burnished bearing surface. In all, 92% (22/24) of these inserts had indentation and roughness at the rim and flange, suggesting neck-cup impingement; periprosthetic fracture occurred in the other two inserts. The mean linear wear rate was 0.035 mm per year. The average maximum oxidation index for the inserts with osteolysis was 3.34, and it was was 3.49 for the inserts without osteolysis. We, therefore, could not detect any significant difference between the aforesaid groups of inserts. CONCLUSIONS: The results strongly suggest that most of the polyethylene wear debris was not generated from the bearing surface. Moreover, the wear debris generated from neck-cup impingement may well be the cause of an inflammatory reaction, which in turn has a strong potential to become the primary cause of osteolysis.     

Investigation on wear of knee prostheses under fixed kinematic conditions

Abstract:  Although polyethylene components have been used in the human joint for over 30 years, wear simulation studies are fundamental to assess wear resistance of total joint replacements. This assessment will help to obtain quality control and acquire further knowledge of the tribological processes that involve joint prostheses. As a result, the risk of implant failure of innovative prostheses will be reduced. The aim of the present study was to investigate the influence on wear of the polyethylene tibial inserts against metallic femoral components using a knee simulator following a standardized kinematics protocol (ISO/CD 14243-3.2). Four intact "small" size specimens of the tibial MP 913 were tested in a four-station knee wear simulator for two million cycles. The volumetric weight loss for the ultra-high-molecular-weight-polyethylene (UHMWPE) tibial inserts was 44 ± 2, 45 ± 3, and 47 ± 3 mg for the specimens #1–3, respectively. This study demonstrated a good repeatability among the stations of the knee simulator obtaining weight loss values congruent with those found by other authors using similar test conditions.     

The clinical significance of proximal tibial resection level in total knee arthroplasty

Clinical and radiographic data were collected in 139 patients with 195 posterior cruciate retaining total condylar knee prostheses to evaluate the relationship of the proximal tibial resection level with long term results. Among the 139 patients were 75 patients with 106 total knee replacements observed for more than 8 years. All patients underwent biyearly routine examinations, including radiographs and clinical evaluations. The average medial tibial resection for the 139 patients with 195 total knee replacements was 2.95 mm, and in the subset of 75 patients (106 knees) observed for more than 8 years, it was 3.3 mm; both groups had a maximum of 14 mm. Sixty-three percent or 67 knees had medial resection levels of 3 mm or less. The average lateral tibial resection for the 195 knees was 5.48 mm and in the 106 knees was 5.71 mm, with a maximum of 22 mm. Fifty-one percent of 104 knees had lateral resection levels of 5 mm or less. Statistical analysis showed that there was no significant correlation between the level of proximal tibial resection and Knee Society knee score, range of motion, radiolucencies, or loosening or revision. These long term results suggest that minimal proximal tibial resection is not necessary for a successful arthroplasty, and problems associated with minimal resection, such as joint line elevation and thin polyethylene inserts, can be avoided.     

Arthroscopy for evaluation of polyethylene wear after total knee arthroplasty

BACKGROUND: The purpose of this report is to demonstrate the severity of polyethylene wear by arthroscopy after total knee arthroplasty (TKA). METHODS: Polyethylene wear of TKA prostheses was evaluated endoscopically in eight knees (six patients). Arthroscopy was indicated when the patients had persistent but slight hydroarthrosis and instability confirmed by stress radiography, but these findings were insufficient for a consensus on polyethylene revision. The average interval between primary TKA and arthroscopy was 9 years 3 months. RESULTS: All knees had unexpectedly widespread, severe polyethylene wear characterized by delamination. Based on arthroscopic visualization of the damage to the polyethylene, all patients consented to undergo isolated polyethylene surface revision surgery. The severity of polyethylene wear was worse than anticipated at the evaluation arthroscopy. After a mean follow-up of 5 years 6 months, all knees were stable and symptom-free. CONCLUSIONS: The usefulness of arthroscopy is validated in certain groups of patients with polyethylene wear when diagnosed with careful clinical examination and stress radiography.