Trabecular metal tibia still stable at 5 years

Background and purpose Clinical results of total knee replacement (TKR) are inferior in younger patients, mainly due to aseptic loosening. Coating of components with trabecular metal (TM) is a new way of enhancing fixation to bone. We have previously reported stabilization of TM tibial components at 2 years. We now report the 5-year follow-up of these patients, including RSA of their TM tibial components.

Patients and methods 22 patients (26 knees) received an uncemented TM cruciate-retaining tibial component and 19 patients (21 knees) a cemented NexGen Option cruciate-retaining tibial component. Follow-up with RSA, and clinical and radiographic examinations were done at 5 years. In bilaterally operated patients, the statistical analyses included only the first-operated knee.

Results Both groups had most migration within the first 3 months, the TM implants to a greater extent than the cemented implants. After 3 months, both groups stabilized and remained stable up to the 5-year follow-up.

Interpretation After a high initial degree of migration, the TM tibia stabilized. This stabilization lasted for at least 5 years, which suggests a good long-term performance regarding fixation. The cemented NexGen CR tibial components showed some migration in the first 3 months and then stabilized up to the 5-year follow-up. This has not been reported previously.     

Preliminary results of an uncemented trabecular metal tibial component in total knee arthroplasty

Trabecular metal has several theoretical advantages for the long-term survival of a tibial component. We report the results of a prospective cohort of 105 consecutive primary total knee arthroplasties using an uncemented trabecular metal (tantalum) tibial component at a minimum 3-year follow-up (range, 36-56 months). There was a significant improvement in Oxford Knee scores and Short Form-12 scores postoperatively. There was no radiolucency at the implant-bone interface on any postoperative radiograph. There has been one (1%) revision of the tibial component for trauma. The 3-year results using this prosthesis are as good as those published for the commonly used cemented prostheses. Longer follow-up is required to see whether these results are maintained over time.     

胫骨高位截骨术治疗膝关节骨性关节炎随访10年的临床观察

目的:探讨外侧闭合胫骨高位截骨术治疗随访10年膝关节骨性关节炎患者的长期临床疗效。方法 :自2005年6月至2015年12月,采用外侧闭合胫骨高位截骨螺钉钢丝内固定术治疗20例膝关节内侧间室骨性关节炎患者,男3例,女17例,年龄43～76(57.80±8.05)岁。分别在术前,术后1、5、10年采用疼痛视觉模拟评分(VAS)和美国膝关节协会评分(KSS)评价膝关节疼痛、功能恢复情况,并观察术后并发症情况。结果:20例患者中16例获得随访,4例失访,随访时间9～11(10.0±0.8)年。VAS评分由术前的7.88±1.15降至术后1、5、10年的3.19±0.91、3.44±0.96、3.69±1.20,术后各时间点与术前比较差异有统计学意义(P0.05)。KSS临床评分由术前的61.94±5.74增加至术后1、5、10年的75.50±4.62、80.13±3.97、77.38±6.40,术后各时间点与术前比较差异有统计学意义(P0.05)。KSS功能评分由术前的62.81±13.03增加至术后1、5、10年的77.50±8.56、81.88±6.55、76.88±10.78,术后各时间点与术前比较差异有统计学意义(P0.05)。所有患者术后伤口愈合良好,无腓总神经损伤及截骨不愈合的并发症。结论:外侧闭合胫骨高位截骨螺钉钢丝内固定术治疗膝关节骨关节炎具有较好效果,可以阻止或延缓膝关节骨性关节炎进展,长期随访能达到与关节置换相当的效果。     

Fracture of a fenestrated metal backing of a tibial knee component. A case report

The case of a metal-backed tibial component that failed by metal fracture is reported. Fracture occurred through fenestrations in the metal plate surrounding the central metal stem. The fracture followed loss of bony support beneath the medial tibial plateau, which had allowed varus deformity of the replaced joint. A high tibial osteotomy procedure had preceded replacement of the joint.     

Trabecular bone strength patterns at the proximal tibial epiphysis

The longitudinal compressive strength of trabecular bone from the human proximal tibial epiphysis was investigated in 12 autopsy specimens using multiple penetration tests with a small diameter indentor. Strength profiles were visualized by three-dimensional computerized reconstruction as a function of location on the resection surfaces. There were large variations of the maximal values between individuals, but the patterns obtained were remarkably uniform. The medial condyle showed the highest peak value in all but one knee with a mean medial-to-lateral peak value-ratio of 1.7. At the medial condyle the high strength area was relatively large with peak values being obtained centrally and anteriorly; the lateral condyle showed a more restricted, posteriorly localized area of high strength. Beneath the menisci, bone strength gradually decreased toward the margins of the condyles; likewise, bone strength decreased to reach very low values at the intercondylar region. There was a significant reduction of bone strength with the distance from the subchondral resection surface. This reduction was most pronounced at the high strength areas.     

Dissociation of the tibial component in total knee replacements

Dissociation of the polyethylene component from its metal backing in total knee arthroplasty is a recognized problem regarding the patella. Two cases of dissociation of the metal-backed tibial component from its polyethylene articulating surface presented symptoms of prosthesis failure: persistent pain, swelling, sensations of instability, and gait difficulty. Investigations ruled out prosthesis malalignment, loosening, and sepsis. Precise diagnosis of dissociation of the tibial component was made by diagnostic arthroscopy.     

Removal of a well-fixed trabecular metal monoblock tibial component

The use of porous tantalum (Trabecular Metal; Zimmer, Inc, Warsaw, Ind) in hip and knee reconstruction has become increasingly popular over the past few years. Widespread clinical use of porous tantalum tibial components for primary total knee arthroplasty has been tempered in part by the perceived difficulty in removing this implant after bone ingrowth has occurred. We present an easy, reproducible, and inexpensive technique for removal of a well-fixed Trabecular Metal Monoblock Tibial Component (Zimmer), which has been used in 4 revision knees. This technique does not require the use of any specialized equipment and results in the production of minimal metallic debris.     

Ceramic coating improves tibial component fixation in total knee arthroplasty

Forty uncemented total knee arthroplasties (36 patients) were randomly allocated to a Miller-Galante II prosthesis with or without hydroxyapatite/tricalcium phosphate (HA/TCP) coating on the titanium fiber mesh on the undersurface of the tibial component. The patients were followed for 2 years with repeated radiostereometric examinations. After 2 years, the HA/TCP tibial components displayed smaller anterior-posterior tilt and less subsidence. The mean value of maximal total point motion was small: 0.5 mm in both groups. At 24 months, there were more radiolucent lines under the tibial tray and around the stem in the uncoated group, but the clinical results did not differ. HA/TCP coating on the undersurface of the tibial component improved the stability and seemed to improve the quality of the interface between the tibial component and the bone.     

全聚乙烯胫骨假体在全膝人工关节置换中的应用

目的探讨全聚乙烯胫骨假体在全膝人工关节置换术后的临床效果。方法对21例24膝施行全聚乙烯胫骨假体的全膝人工关节置换,平均术前HSS评分为40.2分,单侧置换18例,双侧置换3例。结果术后随访2.5~4.5年,失访3例,平均随访HSS评分为86.5分(范围:80~89分),其中临床疗效优18膝,良3膝,中0膝,差3膝,优良率达87.5%。结论全聚乙烯胫骨假体的全膝人工关节置换短期疗效满意,手术技术与带金属底托胫骨假体的全膝人工关节置换术基本一致,对经济较为困难的患者是一种可供选择的假体。     

Influence of polyethylene constraint on tibial component fixation in total knee arthroplasty: follow-up report after 5 years

The influence of articulating surface design of AMK total knee prosthesis (DePuy, Johnson & Johnson) on migration and radiographic outcome at 5 years was evaluated. The knees were randomly allocated to receive a flat or a concave insert with retention of the posterior cruciate ligament when preoperative deformity was less severe and either a concave or a posterior-stabilized insert with resection of the posterior cruciate ligament when deformity was more pronounced. In 64 knees, migration was measured with radiostereometry. The posterior-stabilized component displayed more varus-valgus tilting than the concave insert. Other statistically significant differences in migration were not seen. Radiolucent lines were frequently seen without differences between prosthesis groups.     

Catastrophic fracture of a stable metal acetabular component

Various modes of failure of primary and revision total hip arthroplasty have been well documented in the literature over the past 30 years. Concerns over polyethylene wear, osteolysis, and hypersensitivity reactions leading to component loosening and early revision have been evaluated and reported in the literature. Routine follow-up is important to monitor for postoperative issues that might lead to the subsequent need for revision.This article describes a case of a 64-year-old man who initially presented 11 years prior with an intertrochanteric fracture, which failed secondary to varus alignment and femoral head osteonecrosis. The fixation was converted to a total hip replacement using the S-ROM system (DePuy, Warsaw, Indiana). Subsequently, the patient was lost to follow-up after primary total hip arthroplasty and presented with a catastrophic fracture of the metal acetabular cup system. The failure was suggested by clinical presentation and confirmed by imaging studies showing a fractured acetabular shell with femoral head prosthesis resting in the superolateral ileum. The contributing factors that resulted in mechanical failure were polyethylene wear and component fracture. The acetabular component was revised with an in-growth cementless trabecular metal multihole cup (Zimmer, Warsaw, Indiana) with bone grafting of acetabular defects.Routine assessments help educate patients and allow careful monitoring by physicians while establishing a radiographic timeline for the identification, progression, or lack of postoperative complications.     

Rotational alignment of the tibial component in total knee arthroplasty is better at the medial third of tibial tuberosity than at the medial border

Background  

Correct rotational alignment of the femoral and tibial component is an important factor for successful TKA. The transepicondylar axis is widely accepted as a reference for the femoral component. There is not a standard reference for the tibial component. CT scans were used in this study to measure which of 2 tibial landmarks most reliably reproduces a correct femoro-tibial rotational alignment in TKA.     

Unilateral tibial polyethylene liner failure in bilateral total knee arthroplasty--bilateral retrieval analysis at 8 years

This is a report of a unique case of bilateral simultaneous total knee arthroplasties in which one tibial liner failed dramatically, whereas the other liner showed minimal evidence of wear. This unique case allows isolation of component factors as the primary contributing etiology to failure. The differentiating characteristic was the method of sterilization and the shelf life of the polyethylene liner. The insert that showed minimal wear was sterilized with gamma radiation in a barrier package and had a shelf life of less than 1 year, whereas the insert that failed dramatically was sterilized in air and had a shelf life of more than 5 years. This case provides a dramatic example of the potential detrimental effects of manufacturing details on the performance of orthopedic implants, particularly polyethylene inserts.     

Gradual-radius femoral component with s-curve post-cam provides stable kinematics at mid-flexion after total knee arthroplasty

BackgroundMid-flexion instability is the one of the reasons for patient dissatisfaction after total knee arthroplasty (TKA). The purposes of this study were to evaluate in vivo knee kinematics and clinical outcomes using a novel TKA design with a gradual femoral radius component and s-curve post-cam, which are intended to prevent the instability initiated by sudden reductions in the femoral radius observed with conventional components.MethodsWe used radiographic-based, image-matching techniques to analyze femorotibial anteroposterior translation, axial rotation, and anterior/posterior cam-post contact during two dynamic movements, squatting and stair climbing, in 20 knees that had undergone posterior-stabilized fixed-bearing TKA with an improved sagittal profiles of the femoral component and post-cam mechanism. We also evaluated patient-reported outcomes assessed by the 2011 Knee Society Score (KSS 2011).ResultsSquatting and stair climbing produced a similar trend in anteroposterior translation and a relatively small standard deviation at mid-flexion. Although the rotation angles varied widely during squatting and stair climbing, the femoral component was consistently externally rotated. Anterior/posterior cam-post contact during squatting and stair climbing were observed in 0/17 knees and 0/0 knees, respectively. The “Symptoms”, “Satisfaction”, and “Functional activities” subscales of the KSS 2011 were significantly (P < 0.05) improved postoperatively compared to preoperatively (“Symptoms”, 10 to 21; “Satisfaction”, 15 to 26; “Functional activities”, 25 to 71).ConclusionA gradual femoral radius component with an s-curve post-cam provided stable kinematics and favorable clinical results during squatting and stair climbing at 1 year after surgery.     

Hydroxyapatite-coated total knee replacement: clinical experience at 10 to 15 years

This study describes 146 primary total knee replacements, either fully or partially coated with hydroxyapatite of which 74 knees in 68 patients were available for clinical and radiological assessment at a mean of 11.2 years (10 to 15). The global failure rate was 1.37% and survival rate with mechanical failure as the end-point was 98.14%. Radiological assessment indicated intimate contact between bone and the hydroxyapatite coating. Over time the hydroxyapatite coating appears to encourage filling of interface gaps remaining after surgery. Our results compare favourably with those of series describing cemented or porous-coated knee replacements, and suggest that fixation with hydroxyapatite is a reliable option in primary total knee replacement.     

The influence of metal backing in unicompartmental tibial component fixation

Summary The fixation of the tibial component in 36 patients with conventionally cemented unicompartmental knee arthroplasties for femorotibial gonarthrosis was studied using roentgen stereophotogrammetric analysis (RSA). Twenty-four tibial components were all-polyethylene while 12 were metal-backed. The follow-up was for 6 years. Significant migration was detected for all cases but two and ranged from 0.3 mm to 5.4 mm. The greater part of the migration occurred during the first 1–2 years, after which two-thirds of the prostheses remained stable. Seven all-polyethylene components were subjected to a stress examination after 1–2 years and displacement, induced by external forces, was found in all seven. A strong correlation was found between the extension of the radiolucent line and the migration. Otherwise, neither demographic, clinical, nor radiographic data correlated with the RSA results. In this study metal backing did not have any influence on prosthetic fixation as measured by RSA.This study was financially supported by Stiftelsen Bistånd åt Vanföra i Skåne, Alfred Österlunds Stiftelse, the Crawford Foundation, Konung Gustav V 80-årsfond, the Medical Faculty of Lund University and Medical Research Council 09509     

Radiolucency adjacent to the tibial component in total knee arthroplasty.

This study determined the accuracy of standard radiographs in observing radiolucency adjacent to the tibial component in total knee arthroplasty. A model of the proximal tibia was used. Plastic sleeves of different heights were glued under the tibial tray to imitate radiolucency. By tilting the x-ray tube 1degrees at a time, an investigation was performed to determine how many degrees it would take to cover the heights of the different plastic sleeves. In a clinical study of patients at standard follow-up, 21 knees were examined using standard radiographs. Radiographs using image intensification were then taken of the same knees to obtain radiographs with views parallel to the plane of the tibial tray. The results of the study on the phantom showed that a 1degrees deviation of the x-ray beam from the optimal position would obscure a 0.5-mm "radiolucency." This was true for radiolucencies of 2, 3, 4, and 5 mm. This was confirmed in the clinical study where < or = 4 mm of radiolucency was obscured on standard radiographs. Therefore, standard radiographs cannot be used to determine radiolucency. The 2-mm radiolucency normally associated with loosening is not clinically valid.     

Hybrid total knee arthroplasty analysis of component failures at an average of 15 years

Hybrid total knee arthroplasty in which the femoral component is cementless and the tibial component is cemented remains controversial. We report on the long-term results of 65 total knee arthroplasties followed for an average of 15 years. There were 18 revisions (27%); of these, 11 were femoral component revisions. The overall implant survival with revision as the end point was estimated as 64% at 15 years. The femoral component survivorship at 15 years was 72%. Because of the high failure rate, hybrid fixation on the femoral side with this design has been abandoned at our institution; but hybrid fixation with a trabecular metal tibia is currently under investigation.     

Rotational alignment of the tibial component in total knee arthroplasty.

This study compares two different methods of aligning the tibial component in a total knee arthroplasty, one by aligning the component with the border between the medial one third and lateral two thirds of the tibial tubercle and the other by allowing the component to seek its own position as the knee is taken through a range of motion. The first technique emphasizes the need to maintain an appropriate quadriceps angle for optimum patellar tracking and the second method optimizes femorotibial kinematics. The two methods suggest different positions for the tibial component, with the tibial component internally rotated an average of 5.6 mm from the border between the medial one third and lateral two thirds of the tibial tubercle when allowed to seek its own rotation. Surgeons must be aware of the choices they are making when selecting a method of aligning the tibial component. The prosthesis used in this study had a relatively high level of rotational constraint. The situation is somewhat different in a less constrained design.