Wear Damage in Mobile-bearing TKA is as Severe as That in Fixed-bearing TKA

Background  

Mobile-bearing TKAs reportedly have no clinical superiority over fixed-bearing TKAs, but a potential benefit is improved polyethylene wear behavior.     

The Mark Coventry Award Articular: Contact Estimation in TKA Using In Vivo Kinematics and Finite Element Analysis

In vivo fluoroscopy is a well-known technique to analyze joint kinematics of the replaced knee. With this method, however, the contact areas between femoral and tibial components, fundamental for monitoring wear and validating design concepts, are hard to identify. We developed and tested a novel technique to assess condylar and post-cam contacts in TKA. The technique uses in vivo motion data of the replaced knee from standard fluoroscopy as input for finite element models of the prosthesis components. In these models, tibiofemoral contact patterns at the condyles and post-cam articulations were calculated during various activities. To test for feasibility, the technique was applied to a bicruciate posterior-stabilized prosthesis. Sensitivity of the finite element analysis, validation of the technique, and in vivo tests were performed. To test for potential in the clinical setting, five patients were preliminarily analyzed during chair rising-sitting, stair climbing, and step up-down. For each task and patient, the condylar contact points and contact line rotation were calculated. The results were repeatable and consistent with corresponding calculations from traditional fluoroscopic analysis. Specifically, natural knee kinematics, which shows rolling back and screw home, seemed replicated in all motor tasks. Post-cam contact was observed on both the anterior and posterior faces. Anterior contact is limited to flexion angle close to extension; posterior contact occurs in deeper flexion but is dependent on the motor task. The data suggest the proposed technique provides reliable information to analyze post-cam contacts.     

In Vitro and In Vivo Evaluation of a Small Caliber Vascular Prosthesis Fixed with a Polyepoxy Compound

Abstract: A small caliber vascular prosthesis obtained from an ovine internal thoracic artery (3. 8–4. 5 mm ID) fixed with a polyepoxy compound and treated with heparin has been evaluated. Cytocompatibility was evaluated in vitro using human endothelial cells (HEC). HEC were obtained from human saphenous vein and cultivated in culture medium supplemented with 25% human serum. Graft segments were rinsed using a standard protocol proposed by the manufacturer. Tissue reaction was tested on a rabbit model of subcutaneous implantation. The patency rate and healing patterns were evaluated comparatively with polytetrafluorethylene (PTFE) 4 mm ID prosthesis in a canine model of carotid interposition. Cytocompatibility assay showed that there was low adhesion on vascular grafts (20 ± 2% of endothelial cells seeded) and no growth of HEC on the graft surface. The graft patency rate was 55% in both groups, and actuarial freedom from occlusion was not different at 3 months (37. 7 ± 15% in Denacol–fixed grafts versus 38. 1 ± 14% in PTFE). Histological studies on the biological grafts shows a frequent neointimal hyperplasia at the anastomosis (5/12), a lack of endothelial cells lining the graft surface, a good preservation of the media, and a moderate inflammatory response in the adventicia. The Denacolfixed graft has presented excellent surgical properties and preservation of the histological structure. Nevertheless, the patency rate was not improved when compared with the PTFE control graft.     

旋转平台全膝关节置换术中胫骨假体的旋转安放及相关研究

目的通过对旋转平台全膝关节置换术（total knee arthroplasty,TKA）术中胫骨假体自行确定的旋转中立位与胫骨结节内侧缘、胫骨结节中内1／3等解剖标志点相互位置关系的比较,探讨TKA术中胫骨假体的正确旋转放置位置。方法2006年3月至2008年3月,对30例患者行初次单膝关节置换术,女21例,男9例;年龄54—77岁,平均62岁。术前诊断：骨关节炎23例,类风湿关节炎7例。所有手术均采用旋转平台膝关节假体。胫骨假体的旋转放置以胫骨前后轴为参照。假体试件安装完毕、关节复位后,全范围内屈伸膝关节数次,使旋转平台在股骨假体的导引下自行确定其伸直位时的旋转中立位。借助于试件前方的刻度标志测量胫骨平台旋转试件相对于金属托中心（胫骨结节内侧缘）的旋转角度。结果胫骨旋转平台试件的中点相对于胫骨结节内侧缘的平均旋转角度为外旋2．3°±3．4°,其中男性平均为2．2°±3．6°,女性平均为2．4°±3．4°,男、女性比较差异无统计学意义。膝内、外翻平均外旋角度分别为2．9°±3．0°和1．4°±3．9°,膝内翻外旋角度大于膝外翻。本次研究的结果显著小于国人胫骨前后轴与后十字韧带中点胫骨结节中内1／3连线的夹角。结论国人TKA术中采用固定平台膝关节假体时,以胫骨结节中内1／3为标准行胫骨假体旋转放置时,有导致胫骨假体相对于股骨假体外旋过度的可能,满意的胫骨假体旋转安放位置应位于胫骨结节内侧缘稍外侧。     

In Vitro and In Vivo Responses to High and Low Doses of Nitrogen-Containing Bisphosphonates Suggest Engagement of Different Mechanisms for Inhibition of Osteoclastic Bone Resorption

The effects of nitrogen-containing bisphosphonates (N-BPs) on osteoclasts (Ocs) may differ with dose and regimen. N-BPs reduce Oc bone resorption by inhibiting the enzyme farnesyl diphosphate synthase (FPPS), an effect counteracted by geranylgeraniol (GGOH), which restores geranylgeranylation downstream of FPPS. We assessed GGOH effects on inhibition of bone resorption by the N-BPs alendronate (ALN), ibandronate (IBN), and zoledronate (ZOL) in an assay of rabbit Oc resorption of bovine cortical bone. GGOH blocked inhibition of resorption at low, but not high, N-BP concentrations, with a 14- to 20-fold increase in IC₅₀ values for each N-BP. In vivo, growing male rats were administered doses calculated to mimic bioavailable exposures in daily (ALN, IBN), weekly (ALN), monthly (IBN), and yearly (ZOL) clinical regimens. Tibiae were harvested at 48 h, and metaphyses were analyzed. With lower ALN and IBN doses, Oc numbers rose by 26–48 %, morphology was normal, and there was no increase in apoptotic Ocs. In contrast, with higher IBN and ZOL doses, bone-associated Ocs were generally rounded in appearance and numbers of nuclei/Oc versus vehicle increased 42 and 31 %, respectively (P < 0.05). With ZOL, there was no rise in Oc number, but there was a 6.5-fold increase in apoptotic Ocs versus vehicle and a ≥13.5-fold increase versus lower-dose ALN or IBN (P < 0.05). With higher-dose IBN there was no rise in Oc number but 7- and 14-fold increases in Oc apoptosis versus low-dose ALN and IBN (P < 0.02). These results suggest that different mechanisms may come into play across the dosing spectrum of N-BPs.     

Determination of Fat-Free Mass Density and its Components in Older Hispanic Adults by In Vivo Methods

The densitometry method estimates body composition based on cadaver reference values, mainly the fat-free mass density value of 1.100 g/cm³. However, several changes in fat-free mass components by aging, ethnicity, and excess adiposity could influence their density and affect body composition estimations. The present study aimed to compare the mean fat-free mass component values in older Hispanic adults to cadaver reference values. This cross-sectional study included a sample of 420 subjects aged ≥60 yr from northern Mexico. Fat-free mass was determined by the four-compartment model using air displacement plethysmography, the deuterium dilution technique, and dual-energy X-ray absorptiometry for body density, aqueous and mineral fractions of body weight, respectively. A 1-sample t test was used to compare the fat-free mass density and aqueous, mineral, and residue fractions of fat-free mass from subjects in the study to the assumed cadaver reference values. The mean fat-free mass density value for the total sample of older Hispanic adults (1.096 ± 0.011 g/cm³) was significantly (p < 0.001) lower than the assumed value of 1.100 g/cm³, except in obese older men. The mean aqueous fraction of fat-free mass (74.8 ± 3.3%) was higher than the assumed value of 73.8%, and the mean residue fraction of fat-free mass value was lower (18.3 ± 3.4%) than the reference value of 19.4%. Indeed, only the mean mineral fraction of fat-free mass value (6.8 ± 0.8%) was similar to the reference value. In the total sample, all characteristic mean fat-free mass values in these older Hispanic adults differed from cadaver reference values, except the mineral fraction of fat-free mass value.     

Letter to the Editor: Early Outcome of TKA with a Medial Pivot Fixed-bearing Prosthesis is Worse than with a PFC Mobile-bearing Prosthesis

Clinical Orthopaedics and Related Research® -     

Pharmacokinetics of Certoparin During In Vitro and In Vivo Dialysis

The efficacy and safety of certoparin in the prophylaxis of clotting during hemodialysis have recently been proven. Different to other low‐molecular weight heparins (LMWHs), certoparin does not accumulate in maintenance dialysis patients for unknown reasons. The purpose of the present study was to examine the impact of the dialysis procedure on the removal of certoparin. In a subgroup of the MEMBRANE study consisting of 12 patients, the pharmacokinetics of certoparin during hemodialysis was determined by means of the anti‐Xa activity. In addition, the elimination of certoparin into continuously collected dialysate was assessed. Further, in vitro experiments with human blood‐simulating high‐flux hemodialysis and hemofiltration were performed to quantify the elimination and the sieving coefficients S_K of the two LMWHs certoparin and enoxaparin compared with unfractionated heparin (UFH). The surrogate marker middle molecules inulin and myoglobin served as reference solutes during the experiments. Finally, the adsorption of ¹²⁵iodine‐radiolabeled certoparin onto the synthetic dialysis membrane was quantified. The clinical study reconfirmed the absence of bioaccumulation of certoparin with anti‐Xa activities between <0.01 and 0.02 IU/mL after 24 h. A short plasma half‐life time of 2.0 ± 0.7 h was determined during hemodialysis. Of the total certoparin dose injected intravenously prior to hemodialysis, only 2.7% was eliminated into dialysate. The in vitro experiments further revealed only 6% of certoparin to be adsorbed onto the dialysis membrane. The anti‐Xa activities of certoparin and enoxaparin slowly declined during in vitro hemofiltration to 87.3 ± 5.5 and 82.5 ± 9.4% of baseline, respectively, while inulin and myoglobin concentrations rapidly decreased. The anti‐Xa activity of UFH remained unchanged. The S_K of both LMWH and UFH was very low in hemofiltration and particularly in hemodialysis with values ≤0.1. The elimination kinetics during hemodialysis suggests strong protein‐binding of certoparin. Different from LMWH significantly cleared by the kidneys, the relatively short half‐life time of certoparin of only 2 h during hemodialysis allows a more reliable control of the anti‐coagulatory effects and decreases the risk of bleeding complications. Dialytic removal does not significantly contribute to the clearance of certoparin in maintenance dialysis patients.     

In Vivo and In Vitro Comparison of Densitometers in the NOREPOS Study

The purpose of this study was to assess the agreement of in vivo hip scans on 3 densitometers (1 GE Lunar DPX-IQ and 2 GE Lunar Prodigy scanners) and to evaluate whether the European Spine Phantom (ESP) was able to reproduce the in vivo variability. Sixteen subjects had 3 repeated scans (with repositioning) on each densitometer, and the ESP was measured on each densitometer at least 40 times. Mean differences between hip scans on the Prodigy scanners were small and insignificant, and the in vivo results were not significantly different from the in vitro results. Bland and Altman plots showed no systematic differences between the Prodigy scanners over the range of bone mineral density (BMD). On the other hand, differences between Prodigy and DPX-IQ changed systematically over the range of BMD. The ESP did not fully reproduce the in vivo difference between Prodigy and DPX-IQ. In conclusion, the ESP is a valid substitute when assessing agreement between Prodigy scanners. However, when assessing agreement between different types of scanners, substitution of in vivo with in vitro measurements should be made with caution.     

Lack of Axial Rotation in Mobile-bearing Knee Designs

It has often been assumed rotational kinematics are improved with mobile-bearing TKA designs as the terms mobile-bearing and rotating platform imply. We tested this assumption by assessing the in vivo axial rotation magnitudes and patterns of 527 knees implanted with 12 different mobile-bearing TKA designs. Implants were grouped and compared by type—posterior stabilized (PS), posterior cruciate retaining (PCR), and posterior cruciate sacrificing (PCS)—and by specific design. We hypothesized all three mobile-bearing types (PS, PCR, and PCS) would achieve greater than 10° average axial rotation and we would find no differences in axial rotation between types. Only 14% of PS knees, 3% of PCS knees, and 17% of PCR knees attained greater than 10° axial rotation when measured from 0° to 90°. The percentage of PCS knees with greater than 10° axial rotation was less compared with the other two groups. Axial rotation averaged 4.3°, 2.5°, and 3.8° for the PS, PCS, and PCR knees, respectively. Incidences of reverse rotation were observed in 17% of PS knees, 32% of PCS knees, and 28% of PCR knees. Compared with the PCS group, the PS group achieved greater average axial rotation and had a lower percentage of knees displaying incidences of reverse rotation. The data refuted the hypotheses. Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.     

Reply to Letter to the Editor: Early Outcome of TKA with a Medial Pivot Fixed-bearing Prosthesis is Worse than with a PFC Mobile-bearing Prosthesis

Clinical Orthopaedics and Related Research® -     

Comparison of Cytotoxic Effects of Bisphosphonates In Vitro and In Vivo

We compared the cytotoxic effects of alendronate (ALN) and incadronate (YM175) on isolated rabbit osteoclasts in vitro and on rats in vivo. In the in vitro experiment, each bisphosphonate was added to the culture of isolated osteoclasts at the final concentration of 3 × 10⁻⁵, 3 × 10⁻⁴, or 3 × 10⁻³ M, and the amount of creatine phosphokinase (CPK) released into the medium was taken as an index of cytotoxicity at 5, 10, and 24 hours after the treatment. Also viability of osteoclasts, measured in terms of trypan blue exclusion, was assessed at 24 hours after the treatment. In YM175-treated groups, CPK activity in the medium increased in a concentration-dependent manner with time, and phase-contrast microscopic observation revealed damaged cell membranes and nuclear deterioration in YM175-treated osteoclasts. As a result, the viability of the osteoclasts was decreased at the concentrations of 3 × 10⁻⁴ and 3 × 10⁻³ M. However, in the ALN-treated groups, neither CPK activity nor viability of isolated osteoclasts changed significantly compared with control levels even at 3 × 10⁻³ M for up to 24 hours. In the in vivo experiment, each bisphosphonate was administered separately to normal rats (7 weeks old, Sprague-Dawley) by intravenous injection at 1, 5, or 25 mmol/kg. Two days after the injection, the animals were euthanized, and the plasma Ca concentration and total CPK activity were measured. In YM175-injected rats, the CPK activity increased at 25 mmol/kg, and a slight decrease in the plasma Ca level was seen at this dose. In contrast, in ALN-injected rats, CPK activity did not increase even at 5 or 25 mmol/kg, and the plasma Ca level did decrease significantly compared with controls. Isozyme analysis revealed that, not only was CPK activity increased in the BB type in YM175-injected rats, it was also increased in the MB and MM types. In conclusion, alendronate, unlike YM175, does not have any cytotoxic effects on osteoclasts either in vitro or in vivo. Received: 14 May 1997 / Accepted: 27 January 1998     

Taurolidine Inhibits Tumor Cell Growth In Vitro and In Vivo

Background: Taurolidine, a derivative of the amino acid taurine, exhibits antiendotoxin, antibacterial, and antiadherence activity. We hypothesized that Taurolidine may inhibit tumor cell growth, both in an in vitro and in vivo setting. Our aim was to examine the effect of Taurolidine on the growth of a rat metastatic colorectal tumor cell line (DHD/K12/TRb) in vitro and in vivo.Methods: In the in vitro experiments, DHD/K12/TRb cells were incubated with 5, 10, 15, 25 g/ml of Taurolidine. Cells incubated in culture medium alone were used as controls. Cell proliferation, cell viability, cell death, and cell apoptosis were measured using commercially available techniques. In the in vivo experiment, BD IX rats were randomized into two groups (n = 10/group). Group A (control) underwent laparotomy and instillation of DHD/K12/TRb tumor cells intraperitoneally followed by phosphate buffered saline (PBS). Group B received Taurolidine (100 mg/kg) instead of PBS. Animals were killed after 24 days and tumor burden assessed by counting the number of tumor nodules in the peritoneal cavity.Results: Incubation of the tumor cells with Taurolidine resulted in a 4-fold decrease in proliferation rates (25 ± 4% vs. 100 ± 28% for controls) and a 4-fold increase in cell necrosis as demonstrated by the increase in LDH release (403 ± 28% vs. 100 ± 26% for controls), at a Taurolidine concentration of 25 g/ml. A dose-dependent decrease in cell viability was also observed. In the in vivo study, local Taurolidine administration resulted in significant decreases in tumor burden (3 ± 1 nodules in Group B animals vs. 649 ± 101 nodules in Group A animals).Conclusions: Taurolidine inhibits the growth of a rat metastatic colorectal tumor cell line in vitro and in vivo and thus may have potential in the prevention of peritoneal metastases.     

In Vivo and In Vitro Evaluation of Bilirubin Removal in Postoperative Hyperbilirubinemia Patients

Abstract: The effect of plasma adsorption (PA) on bilirubin removal by a porous type anion exchange resin (Me-disorba BL, Kuraray) was evaluated in vitro PA and in vivo PA and plasma exchange (PE) in postoperative hyperbilirubinemia patients. Serum and plasma bilirubin were measured by routine biochemical tests, fractionated by high-performance liquid chromatography, and its reduction and rebound were compared. In vitro and in vivo PA indicated the selectivity in bilirubin removal against measured molecules. Changes in bilirubin fractions after PA showed higher adsorbance of conjugated bilirubin (21.4–30.8%) and less adsorbance of delta (85.7%) and unconjugated bilirubin (73.7%). These differences were not observed after PE. But rebound of serum total bilirubin levels after PA was more than that after PE. It is suggested that PA by the resin is selective and has a different metabolic effect on bilirubin during and after PA as compared with PE.     

In Vivo and In Vitro Analysis of Rat Lumbar Spine Mechanics

Background  

Rodent lumbar and caudal (tail) spine segments provide useful in vivo and in vitro models for human disc research. In vivo caudal models allow characterization of the effect of static and dynamic loads on disc mechanics of individual animals with time, but the lumbar models have required sacrifice of the animals for in vitro mechanical testing.