In vivo roughening of retrieved total knee arthroplasty femoral components

BackgroundJoint registry data highlights the higher rates of cumulative revision for younger patients undergoing TKR. One of the reasons associated with this higher revision rate may be due to the wear of the UHMWPE leading to loosening. Alternate bearing surfaces have been developed to address this problem; however, roughening of the metal bearing surface has not been demonstrated in vivo.MethodWe recorded roughness measurements of retrieved femoral components.ResultsAverage lateral condyle roughness was 0.032 μm, compared to control values of 0.020 μm, p = 0.002; average medial condyle roughness was 0.028 μm, compared to a control value of 0.019, p < 0.001.ConclusionThere was a small but statistically significant roughening of femoral components in vivo compared to controls. This may have important implications for aseptic loosening of knee arthroplasty components and the decision to use scratch resistant components.     

Surface roughness quantification of CoCrMo implant alloys.

The articulating surfaces of CoCrMo alloy wear specimens and retrieved femoral components of artificial total knee joints are subject to uneven wear. A repeatable and reliable measurement method is necessary to evaluate the surface damage. In this study, the surface roughness of CoCrMo alloy specimens subjected to in vitro third-body wear, and retrieved femoral components of knee joints were analyzed using a white light interference surface profilometer. Each third-body wear specimen was divided into a 19x19 grid of 1-mm(2) squares (361 squares) and each femoral condyle of retrieved specimens was divided into two 10x10 grids of 1-mm(2) squares (100 squares). The surface roughness average (Ra) and root mean square roughness (RMS) were measured for each of the squares. The average of all points measured was defined as the true surface roughness mean (TSRM). Measurements were then performed on 40-60 (in vitro specimens) or 30 (retrieved specimens) randomly selected points on each surface and a cumulative average was calculated. The cumulative average surface roughness value from only a few (5-15) measurement points generated large deviations (>40%) from the TSRM, but converged to the TSRM as the number of measurements increased. The number of randomly selected points necessary for the cumulative average roughness to be within 10% of the TSRM was defined as the representative measurement number (RMN). The RMN for the third-body wear specimens (surface area of 573 mm(2)) was 40 points, and the RMN for the retrieved femoral components (surface area of 100 mm(2)) was 20 points. To obtain the cumulative surface roughness average within a desired percentage of the TSRM, it is important to define or experimentally determine the critical minimum number of measurements, RMN. Several types of measurements may be necessary to understand wear and damage on metal components of artificial knee joints. The TSRM represents a consistent and reproducible measure of surface damage, and a starting point to develop appropriate measurement protocols to quantify damage on a specific surface.     

TEM observation of seven retrieved total knee joints made of Co-Cr-Mo and Ti-Al-V alloys

We demonstrate that a myriad of fine particles produced by the abrasion of both cobalt-chromium-molybdenum (Co-Cr-Mo) and titanium-aluminum-vanadium (Ti-Al-V) alloys accumulate in the synovial cells next to surgical implants made from these alloys. The metallic particles were of various sizes, and were observed within the lysosomes. Energy dispersive X-ray spectroscopy studies revealed that the fine spherical particles consisted solely of Cr, and that other larger particles were composed of the Co-Cr-Mo alloy. We measured the size of the metallic particles using the public domain NIH image program, and found that most of the fine spherical particles were 10-15 nm in diameter (n=1000). Eighty percent of the large particles were 30-35 nm in length and 20-25 nm in width (n=300). In addition, EDS examination clarified that all of the fine particles of the Ti-Al-V alloy were composed of that alloy. For this alloy, when discounting the larger particles, the fine metal deposits were 20-25 nm in length and 10-15 nm in width (n=1000).From these findings, we conclude that the Co-Cr-Mo alloy is easily corroded and that Co is released from the cells. In contrast, the Ti-Al-V alloy is very stable and does not corrode, although the Ti-Al-V alloy does produce particles that are smaller than those produced by the Co-Cr-Mo alloy.     

Surface extraction can provide a reference for micro-CT analysis of retrieved total knee implants

BackgroundQuantitative measurements of damage and wear in orthopaedic components retrieved from patients during revision surgery can provide valuable information. However, to perform these measurements there needs to be an estimate of the original, unworn geometry of the component, often requiring multiple scans of the various sizes of components that have been retrieved. The objective of this study was to determine whether the articular and backside surfaces could be independently segmented from a micro-CT reconstruction of a tibial insert, such that a tibial insert of one thickness could be used as a reference for a tibial insert of a different thickness.MethodsNew tibial inserts of a single width but with six different thicknesses were obtained and scanned with micro-CT. An automated method was developed to computationally segment the articular and backside surfaces of the components. Variability between intact and extracted components was determined.ResultsThe deviations between the comparisons of the extracted surfaces (range, 0.0004 to 0.010 mm) were less (p < 0.001) than the baseline deviation between the intact surfaces (range, 0.0002 to 0.053 mm).ConclusionsAn extracted surface from one insert thickness could be used to accurately represent the surface of an insert of a different thickness. This greatly enhances the feasibility of performing retrieval studies using micro-CT as a quantitative tool, by reducing the costs and time associated with acquiring, scanning, and reconstructing multiple reference tibial insert geometries.Clinical relevanceThis will add greater detail to studies of retrieved implants, to better establish how implants are functioning in vivo.     

Analysis of retrieved alumina ceramic components from Mittelmeier total hip prostheses.

This study analyses explanted prostheses from a single surgeon's 16-yr series of Mittelmeier cementless total hip replacements. The patient group was young (patients aged 15-60, average 40) and active. Revision was related to various factors. All components were measured using a Kemco 3D coordinate measurement machine. Wear surfaces and linear wear penetrations of 11 retrieved Mittelmeier Autophor ceramic hip components (average implantation time 8.6 yr, range 1-13 yr) were analysed and the different types of wear identified. Surface analysis was then performed using Talysurf contacting profilometry and scanning electron microscopy. Three types of wear were identified: low wear (1 case), stripe wear (6 cases) and severe wear (4 cases). Stripe wear was characterised as a stripe of worn area on the head up to 150 microns deep whilst the rest of the head showed very low wear. The cups in the stripe wear cases were worn over about 40-50% of the surface. Severe wear cases had very large areas of heavy wear and visible volume loss on both heads and cups. The four cases of severe wear were associated with abnormal clinical histories.     

Surface engineering of prosthetic knee components

Conventional total and uni-compartmental knee replacement designs usually incorporate metal femoral and tibial components with an ultra high molecular weight polyethylene (UHMWPE) bearing surface. The tibial components can be modular or monobloc and are of the fixed bearing type in the majority of cases. Mobile bearings are also in common use with a modular meniscal insert with either rotation only or a combination of rotation and translation. Wear of the UHMWPE components remains of primary concern in these prosthetic devices. Catastrophic wear and delamination has been largely addressed by improvements in UHMWPE quality and manufacturing methods, however, abrasive and adhesive wear of the UHMWPE components remains a concern for long-term survivorship of total knee replacement. This review very briefly covers published long-term survivorship of primary knee arthroplasties, primary wear mechanisms present in knee replacements and the potential for wear reduction by surface engineering of the metal wear counterfaces. There are several methods and materials available, which offer the potential for significantly reduced wear.     

Influence of the distal femoral resection angle on the principal stresses in ceramic total knee components

PurposeA certain failure mode using a newly developed cemented ceramic femoral component in total knee replacement was observed in clinical application, i.e. fracture of the femoral component during intraoperative impaction. This may be caused by unintentional deflection of the saw blades during cutting with consecutive higher resection angle of the distal femur than desired, leading to bending of the femoral component during implantation. A finite-element-analysis was carried out to simulate implantation of the femoral component and to evaluate the influence of distal femur preparation on implant stress.ScopeWe developed and validated a numerical model of the ceramic femoral component including a contact formulation which allowed calculating the principal stresses of the implant during implantation onto the resected femur. The analysis considered different anterior and posterior resection angles with a total of 17 variations. By increasing the femoral resection angle in the finite-element-model it could be shown that a deviation of three degrees from the intended resection angle can cause critical stress amounts during implantation.ConclusionsWhen implanting the ceramic component in total knee arthroplasty, the femoral resection angles should be prepared very precisely, in particular anterior saw blade deflection has to be avoided. The implant manufacturer increased implant safety through an additional resection template. Moreover, the impaction of the ceramic femoral component during cementing was not further recommended by using a hammer.     

MRI analysis for rotation of total knee components

PurposeThe aim of this study was to analyze rotation of total knee (TKA) implant components using magnetic resonance imaging (MRI) and to assess the reproducibility of results. It was hypothesized that rotation of both femoral and tibial implants would be reliably reproduced.MethodsA retrospective analysis of 55 MRI studies in subjects with painful TKA implants was conducted. There were 27 zirconium and 28 cobalt/chrome/molybdenum alloy (CoCrMo) femoral components in the group. The rotation angle of femoral and tibial components was measured and determined. Statistical analysis included tests for reliability, variance between implant groups, standard deviations and confidence intervals.ResultsThere was a sufficient inter- and intra-observer reliability determined for rotation in all implants. The inter-observer reliability was notably higher in the zirconium femur group with significant less variance and lower standard deviations than the CoCrMo femoral component comparison group. Standard deviations for femoral rotational analysis were within a clinically acceptable range. The standard deviations were considerably higher in the tibial component rotational analysis.ConclusionMRI analysis of the rotation of femoral implants after TKA allows good reproducibility, especially with review of zirconium implants. There is less reproducibility for tibial components related to the applied geometric method to quantify rotation and not to the MRI technique.     

Surface damage analysis of retrieved highly crosslinked polyethylene tibial components after short-term implantation

The use of highly crosslinked polyethylene (PE) in the knee remains controversial, because of reduced fatigue fracture properties of the material. The current study investigated postmelt surface damage as well as potential contributors to this damage in retrieved highly crosslinked PE tibial components, after short-term in vivo durations. Retrieved conventional PE tibial components were examined for comparison, as well as unused time zero highly crosslinked and conventional PE tibial components for inherent manufacturing surface characterization. Predominant surface damage modes on highly crosslinked PE components were machine mark loss and abrasion, while conventional PE components primarily had machine mark loss, abrasion, and delamination. In vivo duration, PE thickness, and conformity of the design were significant predictors of surface damage on retrieved conventional PE components. Donor weight and the conformity of the design were significant predictors of surface damage on retrieved highly crosslinked PE components. This retrieval data on highly crosslinked PE tibial components suggest that in vivo wear occurred, observed as postmelt surface damage. The highly crosslinked Durasul material examined in this retrieval study appeared to outperform the conventional PE components made from 4150 resin, ram-extruded and gamma-sterilized in air, but not the conventional components made from 1020 resin, compression molding and gamma sterilization in nitrogen. Early retrieval data of highly crosslinked PE tibial components are important to serve as a benchmark to be compared with future longer-term retrieval studies investigating whether surface damage translates to clinically relevant particulate wear debris generation and PE clinical performance.     

Rotational mismatch between femoral and tibial components should be avoided in JOURNEY II bi-cruciate stabilized total knee arthroplasty

BackgroundJOURNEY II bi-cruciate stabilized (BCS) knee system, a guided motion total knee arthroplasty (TKA), has been reported to reproduce physiological knee kinematic motion with good clinical outcomes. However, this guided system may be sensitive to the femorotibial rotational alignment.MethodForty-four patients (50 knees) who underwent JOURNEY II BCS TKA were included in this retrospective study. The 2011 Knee Society Score (KSS) and range of motion were assessed pre-operatively and one year postoperatively. The femoral component rotational angle relative to the surgical epicondylar axis and the tibial component rotational angle relative to Akagi’s line were measured postoperatively. The absolute difference between the femoral and tibial component rotational angles was defined as femorotibial component rotational mismatch. The correlation between the parameters of these rotational alignments and postoperative clinical outcomes was evaluated. Additionally, receiver operating characteristic curve analysis was performed to determine the optimal cut-off point of the femorotibial component rotational mismatch.ResultsMean femoral and tibial component rotational angles were 0.4° (internal rotation) and 0.7° (external rotation), respectively. The rotational mismatch of the femorotibial component was 3.2°. There were negative correlations between femorotibial rotational mismatch and clinical outcomes, including objective knee indicators, patient satisfaction, functional activities, and total 2011 KSS. The area under the curve of the femorotibial component rotational mismatch was 0.768 and the cut-off value identified by the Youden index was 2.8°.ConclusionsExcessive rotational mismatch between the femoral and tibial components can negatively influence the clinical outcomes of JOURNEY II BCS TKA.     

Failures of yttria-stabilised tetragonal zirconia: 52 retrieved ceramic femoral heads of total hip prostheses

Fifty two ceramic femoral heads have been investigated after implantation. All heads had articulated against ultra high molecular weight polyethylene (UHMWPE) cups. Examination of the heads shows changes in sphericity and surface roughness due to the wear. The behaviour of these retrieved heads after clinical use confirms the problems derived from the use of yttria-stabilised tetragonal zirconia heads. In this paper, a failure mechanism for this type of ceramic is proposed. The slow yttria dissolution produces the transformation from tetragonal to monoclinic phase with a volume change. This fact provokes an important decrease in mechanical properties favouring wear. The yttria dissolution and the zirconia solid transformation were confirmed by X-ray diffraction.     

Fracture of titanium nitride-coated femoral component after total knee arthroplasty

We report a case of fracture of a titanium nitride-coated femoral component 3 years after primary total knee arthroplasty (TKA). The fracture was at the medial condylar area just posterior to the medial peg of the femoral component. The backside of the broken medial condylar portion of the femoral component was devoid of cement. Debonding of the component is a possible cause of the stress fracture. To our knowledge, this is the first case report of the fracture of the femoral component manufactured from titanium alloy.Level of evidenceIV     

Fatigue fracture of the femoral component in total knee replacement

BackgroundFracture of femoral component in total knee arthroplasty (TKA) has become a rare complication with improvements in metal alloy manufacturing technology.MethodologyWe report two cases of fracture of femoral components 9 and 10 years after primary TKA. The Buechel-Pappas (BP) knee system used in our two cases were designed by the same team who designed the LCS TKA implants. The femoral component is made of cobalt chromium alloy. The break in the femoral component noted in both the cases were at a similar site, at the distal medial flange just posterior to the peg of the femoral component.ResultBoth these cases underwent revision surgery using stemmed implants with good results. Implants retrieved were analysed with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) to study the fracture pattern and material properties respectively. Fractography analysis of both our cases showed that the crack initiated laterally from the thin edge (1mm) around the sharp angulated corner of the medial femoral condyle and spread medially towards the thicker segment.ConclusionWe feel two fractures of femoral component out of 9000 TKA in ten years is significant. We recommend a re-evaluation of the femoral component of the BP knee system to ensure that the edges, specifically the sharp corners, have adequate thickness to avoid a fatigue fracture.     

Fracture of the oxidized zirconium femoral component after total knee arthroplasty

BackgroundFemoral component fracture is a rare complication of total knee arthroplasty (TKA).CaseWe report a case of oxidized zirconium (Oxinium) femoral component fracture after total knee arthroplasty. The fracture site was the junction of the central and medial flanges. The patellar component and polyethylene insert had delamination at the contact point of the fracture line, and the tibial tray had loosening at the medial side. There was no cement adherence at the component fracture site, suggesting that debonding had occurred at the cement-implant interface in this area. Examination with a scanning electron microscope revealed beach marks, which are characteristic findings of metal fatigue.ConclusionWe considered that the cause of femoral component fracture was a fatigue fracture due to poor fixation of the component to the bone caused by poor osteotomy technique or poor cementing technique. To our knowledge, this is the first case of Oxinium femoral component fracture.     

Surface micro-analyses of long-term worn retrieved "Osteal" alumina ceramic total hip replacement

We analyzed wear pattern of long-term retrieved alumina-alumina hip prostheses from Osteal, which were implanted for 15-19 years. A comparison was carried out with our previous study of 17-year Biolox alumina-on-alumina hip prostheses, (Shishido et al., J Biomed Mater Res B 2003;67:638-647) and all-alumina total hip replacement run under microseparation simulator tests. Of particular interest was the occurrence of stripe wear in these first generation alumina ceramic bearings. Two balls of Osteal revealed only one stripe wear as did the respective liners on their rim areas. In these latter balls, the stripes were shallower than those previously observed in Biolox implants. A microscopic analysis of the bearing surface was carried out using scanning electron microscopy and fluorescence microprobe spectroscopy. On average, the Osteal retrievals had one grade lower wear than Biolox retrievals. Fluorescence microprobe maps showed that Biolox ball surfaces had higher compressive stress than the Osteal likely due to severe impingement and microseparation promoted by the bulky implant design.     

Change in UHMWPE properties of retrieved ceramic total knee prosthesis in clinical use for 23 years

The alumina-ceramic total knee prosthesis developed by Kyocera Corp. was implanted in 1979, and was in clinical use for 23 years until total knee arthroplasty revision surgery in January 2002. It is believed that this is the longest clinical period of a ceramic total knee prosthesis reported to date in the world. In the present study, we gave consideration to the long-term clinical stability of the alumina-ceramic femoral component as well as the mechanism of in vivo degradation of ultrahigh molecular weight polyethylene (UHMWPE) based on the evaluated wear, oxidation, and fracture toughness of the retrieved UHMWPE. We concluded that the degradation of UHMWPE by progressive oxidation is an issue to be solved in the future. To moderate stress concentration, use of a thin UHMWPE insert should be avoided. The low wear rate and the mild wear pattern observed this time suggest the possibility of reduced wear of the UHMWPE against the alumina-ceramic femoral component, and the usefulness of the alumina-ceramic total knee prosthesis component was recognized even after long clinical use.     

人工全膝关节置换术中髌股关节轨迹不良的处理策略及疗效

目的　总结人工全膝关节置换（total knee arthroplasty,TKA）术中,纠正髌股关节轨迹不良的方法及效果。 方法　2012年6月-2014 年12 月,对52例58膝TKA术中出现髌骨向外侧脱位倾向髌股关节轨迹不良的患者,针对发生原因,通过单纯调整髌骨内、外侧支持带张力,髌骨修整成形或调整胫骨假体位置等方法,或者联合应用上述两种或两种以上方法进行纠正。 结果 术中无拇指试验髌股关节轨迹恢复正常,术后髌骨未出现向外脱位倾向。术后切口均Ⅰ期愈合,2例因外翻明显,术中外侧支持带松解范围较大,术后出现关节积血,经对症处理后好转,无其他并发症发生。所有患者术后均获随访,随访时间 17-47个月,平均32个月。膝关节内、外翻畸形均获得矫正,4例残留 5-10°(平均8°）左右的屈曲畸形。随访末期KSS评分78-89分,平均84分,膝关节KSS功能评分为82-91分,平均86分。术后至随访期末X线片均显示人工关节位置正常,无松动及感染迹象。 结论 TKA术中出现髌股关节轨迹不良时,通过单纯调整髌骨内、外侧支持带张力,髌骨修整成形或调整胫骨假体等方法,或者联合应用上述两种或两种以上方法等进行调整,是处理髌股轨迹不良的有效方法,有利于术后膝关节的功能恢复。     

Migration of polyethylene particles around nonloosened cemented femoral components from a total hip arthroplasty-an autopsy study

Three cemented femoral components from total hip arthroplasties retrieved at autopsy were examined in regard to the migration of birefringent polyethylene particles across the fixation interfaces. They were obtained from two patients who died from unrelated causes. They had been in place, respectively, for 8 and 9 years (first patient) and for 9 years (second patient). Osteolysis was present in the acetabular side only. The femoral components were not loosened. Histologic sections were performed at four levels of the femoral components, and polyethylene particles were counted with the use of a semiautomatic image analyzer. Sections below the tip of the stem were treated by deorganification and the lysate was centrifuged in the attempt to isolate wear debris. Particles were found at both interfaces (bone-cement and metal-cement) and in the cancellous bone between the trabeculae. They were also present in the Haversian canals of the cortical bone. Particles of various sizes were found in the medullary canal beneath the tip of the stem. In scanning electron microscopy, they appeared to have irregular shapes. Wear debris can migrate across the cement-bone interface of nonloosened implants. They appear to progress through the porosity of the cancellous bone.     

Varus/valgus alignment of the femoral component in total knee arthroplasty

The position of the femoral component in 362 total knee replacements was assessed radiologically. A subgroup of 32 knees, 18 of which had perfect alignment and 14 with imperfect alignment underwent CT scout scans of the femur from which the mechanical axis of the femur could be measured. Radiologically 92% of all components were implanted within 3 degrees of the target value. There was close correlation between the CT and X-ray measurements in the subgroup. Deviation from the mechanical axis was 1.16 degrees (range -2.5 to +2) in the perfectly aligned knees, validating both surgical technique and radiological assessment. Causes for inaccuracy in femoral placement and future likely developments are discussed.     

膝关节置换时股骨髓内定位对假体排列的影响

BACKGROUND: The femoral intramedullary guides in total knee arthroplasty require high precision, complex operation, it is very important for prosthesis and joint function to choose more precise positioning method and determine the correct needle point. OBJECTIVE: To study the effect of needle point position on prosthesis arrangement when applying different femoral intramedullary guides methods in total knee arthroplasty. METHODS: Totally 80 patients who received the treatment of total knee arthroplasty in Changshu No.1 People’s Hospital from January 2012 to July 2015 were selected and divided into test and control groups according to random number table (n=40/group). The patients in the test group accepted CT scan for femoral   intramedullary guides. The theoretical position of femoral intramedullary guides entry point was marked using radiographic parameters. In the control group, the traditional total knee arthroplasty technology was used to mark the entry point of femoral intramedullary guides. The needle point position when applying different femoral intramedullary guide methods was observed. The effect of femoral intramedullary guides on prosthesis arrangement in total knee arthroplasty was discussed. RESULTS AND CONCLUSION: Compared with the control group, the distance from entry point to femoral anatomic line on positive and lateral X-ray film in the test group was shorter, femoral prosthesis lateral angle and physiological valgus angle were closer to the theoretical value, distance from intersection of femur axis and femoral condyle to block center was shorter; the differences were statistically significant (P < 0.05). These results demonstrate that compared with the traditional two-dimensional intramedullary positioning, the needle point position of three-dimensional CT scan stimulative positioning is more accurate. The location more concentrates on within intercondylar fossa 2-5 mm, more front of intercondylar fossa 3-10 mm, three-dimensional CT scan stimulative positioning is a reliable choice for femoral intramedullary guides.