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.     

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。     

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.     

Short-term survival analysis of the all.polyethylene tibial component in total knee arthroplasty

Toourknowledge, thesurvivorshipofall polyethylenetibialcomponentsintotalkneearthroplastyhasnotbeenstudiedinChinapreviously. Wereportaseriesof24 cementedtotalkneearthroplastyusingall polyethylenetibialcomponents.METHODSBetweenDecember2000andDecember2002, 24cementedtotalkneearthroplastyin21 patientswereperformedusingall polyethylenetibialcomponents.Themeanageofthe21 patients( 9 menand 12women) atoperationwas55 years, ranging48 61years. ThemeanpreoperativeHSSscorewas40. 2(range, 36 43 ).…     

Failure of total knee arthroplasty due to loosening and deformation of the tibial component

A series of 100 consecutive UCI knee replacements showed a 7 per cent incidence of reoperation due to loosening of the prosthesis associated with permanent deformation of the tibial component. Analysis of the clinical data, roentgenograms, and removed implants showed associations between failure and radiolucency at the cement-bone interface, prosthetic obliquity, collapse of trabecular bone, change of the alignment of the extremity, and permanent deformation of the tibial component. Although no one of these factors by itself can be responsible for the mechanical failure of the arthroplasty, a predominant failure pattern exists. We think that the sequence of events is as follows: implantation of the tibial component with medial or lateral tilt; lack of firm skeletal stabilization; continual microtrabecular fractures; change in alignment of the extremity; and permanent deformation of the plastic component.     

Internal rotation of the tibial component is frequent in stiff total knee arthroplasty

Background  

Stiffness complicating TKA is a complex and multifactorial problem. We suspected internally rotated components compromised motion because of pain, patellar maltracking, a tight medial flexion gap, and limited femoral rollback on a conforming lateral tibial condyle.     

Stability of initial fixation of the tibial component in cementless total knee arthroplasty

This study measured the vertical displacement of three kinds of cementless tibial components [Porous Coated Anatomical (PCA), Tricon, and Whiteside], under eccentric loading up to 2,225 N. Displacement between the tibial tray and the proximal tibia was measured with linear variable differential transformers at the anterior and posterior side when anteriorly or posteriorly loaded, and at the medial and lateral side when medially or laterally loaded. The general pattern of motion was sinking at the loaded side and lift-off at the opposite side. Lift-off opposite the loaded side was fairly small for all components at all measurement sites. Among the three components, the Whiteside showed the smallest displacements. The Tricon (when anteriorly or posteriorly loaded), and the PCA (when medially or laterally loaded) showed sinking at the loaded side. Anterior screw fixation of the PCA was not effective in preventing anterior lift-off. The tilting motion of the tibial components observed in this study implies instability of the initial fixation, which could possibly compromise bony ingrowth. Furthermore, this tilting could cause uneven distribution of load, and potentially result in fracture of the underlying bone.     

Influence of tibial component posterior slope on in vivo knee kinematics in fixed-bearing total knee arthroplasty.

The relation between prosthesis component kinematics and posterior slope of the tibial component in total knee arthroplasty is much debated. Three-dimensional kinematics of the replaced knee was obtained by video fluoroscopy in 23 knees treated by cruciate-retaining or cruciate-substituting arthroplasty. Relative position and orientation of the metal components were calculated in stair ascending, getting up from and sitting down on a chair, and single step up-and-down. Significant correlations were found between tibial component posterior slope and anteroposterior position of tibiofemoral lateral contact and between this slope and maximum knee flexion. These correlations were task and design specific. However, the average of the tibiofemoral contact positions over all three motor tasks was slightly posterior to the midline of the tibial base plate, reaching at most 84% of its anteroposterior dimension. Performing a posterior slope of the tibial cut does not put total knee arthroplasty with high conforming designs at higher risk of failure, even when large posterior inclinations need to be achieved.     

Synchronisation of tibial rotational alignment with femoral component in total knee arthroplasty

The rotational axis of the tibial component in total knee arthroplasty described by Insall is generally accepted, but rotational mismatch between the femoral and the tibial components can occur because the alignment of each component is determined separately. We developed a connecting instrument to synchronise the axis of the tibia to the axis of the femur. We compared the rotational axis of the tibial component using our method and medial one third of tibial tuberosity (Insall’s reference) in 70 consecutive TKAs. The rotational axis of the tibial component from the femoro-tibial synchronisation was rotated internally 13.8° ± 5.8° (range, 2° – 24°) more than the axis of Insall’s reference. Eighty three percent of patellae tracked centrally and the patellae tilt measured 2.2° on average. More attention should be given to the rotational congruency between the femoro-tibial components, because the recent prosthetic design has more conforming articular surfaces.

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Résumé La rotation axiale du composant tibial dans la prothèse totale du genou décrite par Insall est généralement acceptée mais elle peut poser problème lorsqu’il existe un trouble de rotation sur le composant fémoral et le composant tibial du fait d’une détermination séparée de la position de chaque composant au moment de l’implantation. Nous avons pour cela développé un instrument qui permet de synchroniser l’axe du tibia et l’axe du fémur. Nous avons comparé la rotation axiale du composant tibial en utilisant notre méthode à propos de 70 prothèses totales consécutives du genou. L’axe de rotation après synchronisation des deux composants a été noté en rotation interne. Cette rotation interne est plus importante que celle prévue par l’axe de référence d’Insall qui est représenté par le tiers interne de la tubérosité tibio-intérieure. 83% des rotules avaient une course normale et un accrochage rotulien a été noté dans 2,2% en moyenne. Une attention particulière doit être portée à la congruence en rotation des éléments fémoro-tibiaux pendant l’implantation d’une PTG d’autant que cette congruence est plus importante dans les nouveaux dessins de prothèses totales du genou récentes.

     

人工全膝关节置换术中胫股关节旋转对线不良的影像学分析

目的分析和探究造成全膝置换术中胫股关节旋转对线不良的可能原因,指导术中选择正确的确定假体部件旋转的方法,以减少术后并发症。方法选择40例正常人的膝关节作为研究对象,男、女各20例,年龄18～42岁。应用螺旋CT扫描(层厚0.5mm)获取膝关节的横断面图像,采用Autocad2004软件测量股骨假体的旋转轴与胫骨假体的旋转轴之间的关系,运用统计学方法分析临床上选择临床上髁轴、外科上髁轴、股骨后髁轴等方法可能存在的潜在的胫股旋转对线不良及其影响程度。结果术中胫骨假体旋转以胫骨结节内、中1/3交界处来确定,而股骨假体旋转分别以临床上髁轴、外科上髁轴、股骨后髁轴外旋3°来确定,可能产生的胫股旋转对线不良的交角平均值分别为2.94°、6.50°、6.83°。结论全膝置换术中利用骨性解剖标志各自独立地确定胫骨假体、股骨假体的旋转对线必然会产生胫股旋转对线不良,而临床上髁轴产生的影响较小。     

Review of the all-polyethylene tibial component in total knee arthroplasty. A minimum seven-year follow-up period

A retrospective analysis of 144 total knee arthroplasties was performed between 1975 and 1981 with a minimum follow-up period of seven years. A posterior cruciate condylar prosthesis was used in each procedure. Patients were followed clinically and roentgenographically, and a set of statistical variables was established based on elevation in joint line, tibial component angular alignment, overall limb alignment, and position of the tibial component on anteroposterior and lateral roentgenograms. Review of the study group found that the Hospital for Special Surgery knee scores improved from a preoperative score of 55 to a postoperative score of 88, with 94.5% having good or excellent results. The mean postoperative range of motion was 106 degrees with a mean extension of -0.3 degrees. Radiolucencies developed in 41% of the knees with 5% of the knees having progressive radiolucencies. Eight knees were considered failures based on clinical and roentgenographic evaluations. Factors found to significantly affect the formation of radiolucent lines included a shift of the tibial component medially by greater than 4 mm, a varus tilt of the tibial component greater than 2 degrees, and the diagnosis of rheumatoid arthritis. The only variable associated with aseptic loosening was an elevation of the joint line by greater than 8 mm.     

Effect of tibial component position on patellar strain following total knee arthroplasty

Patellar fracture following total knee arthroplasty has been related to component alignment and tibiofemoral joint-line position. The purpose of this study was to determine the effect of anteroposterior displacement of the tibial component and inferosuperior displacement of the tibiofemoral joint line on patellar strain following total knee arthroplasty with a cruciate-subsituting design. Patellar strain increased (decreased) with anterior and inferior (posterior and superior) displacement. When averaged across all flexion angles, the strain changed approximately 1.7%/mm of anteroposterior displacement and 1.0%/mm of inferosuperior displacement. For individual specimens, changes in strain as high as 3.2%/mm of inferosuperior displacement of the joint line were seen. These changes in strain may be associated with changes in the patellofemoral contact force seen for similar changes in tibiofemoral joint-line position. These changes in strain may be a biomechanical indicator of the efficacy of retaining the preoperative position of the tibiofemoral joint line.     

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.     

The accuracy of extramedullary guides for tibial component placement in total knee arthroplasty

Anteroposterior radiographs that included the whole tibia were taken before and after 75 total knee arthroplasties in 48 patients. The same tibial extra-medullary alignment guide system was used in every knee. The average tibial component alignment was 0.4 (SD 2.5, range -4.9 to 6.4) degrees of valgus post-operatively. 59 tibial components (78.7%) had a tibial cut within 3 degrees from being perpendicular to the mechanical axis, ten were too valgus (13.3%) and six were too varus (8%). The chance of the tibial components becoming too varus was higher if there was lateral tibial bowing, compared with no tibial bowing (p = 0.048). A smaller lateral width of the leg increased the chance of the tibial components becoming too valgus (p = 0.047).     

Optimizing femoral component rotation in total knee arthroplasty.

Femoral component rotation is important in total knee arthroplasty to optimize patellofemoral and tibiofemoral kinematics. More recently, the epicondylar axis has been cited as the definitive landmark for femoral component rotation. However, there are few studies to support the validity of this rotational landmark and its effect on the patellofemoral and tibiofemoral articulations. In the current study, a total knee arthroplasty was done in 11 knees from cadavers. The knees were tested with various femoral component rotations from 5 degrees internal rotation to 5 degrees external rotation referenced to the epicondylar axis and to the posterior femoral condyles. Each knee acted as its own internal control. The knees were actively ranged from 0 degrees to 100 degrees by a force on the quadriceps tendon in an Oxford knee simulator. Three-dimensional kinematics of all three components were measured whereas a multiaxial transducer imbedded in the patella measured patellofemoral forces. Femoral component rotation parallel to the epicondylar axis resulted in the most normal patellar tracking and minimized patellofemoral shear forces early in flexion. This optimal rotation also minimized tibiofemoral wear motions. These beneficial effects of femoral rotation were less reproducibly related to the posterior condyles. Rotating the femoral component either internal or external to the epicondylar axis worsened knee function by increasing tibiofemoral wear motion and significantly worsening patellar tracking with increased shear forces early in flexion. Based on the current study, the femoral component should be rotationally aligned parallel to the epicondylar axis to avoid patellofemoral and tibiofemoral complications.     

Improving tibial component coronal alignment during total knee arthroplasty with use of a tibial planing device

BACKGROUND: The outcomes of knee arthroplasty have been shown to be affected by component alignment. Intramedullary and extramedullary alignment instrumentation are fairly effective for achieving the desired mean tibial component coronal alignment. However, there are outliers representing >3 degrees of varus or valgus alignment with respect to the anatomic tibial shaft axis. We measured the efficacy of a custom tibial planing device for reducing the outliers in tibial alignment. METHODS: We designed a tibial planing tool in an effort to improve tibial alignment. In one cohort (100 knees), we used traditional intramedullary alignment instrumentation to make the tibial bone cut. In a second cohort (120 knees), we used intramedullary alignment instrumentation to make the cut and also used a custom tool to check the cut and to correct an inexact cut. Tibial tray alignment relative to the long axis of the tibial shaft was measured in the coronal and sagittal planes on postoperative radiographs. The target coronal alignment was 90 degrees with respect to the tibial shaft axis (with <90 degrees denoting varus alignment). A total of 100 anteroposterior radiographs and sixty-five lateral radiographs were analyzed for the group that was treated with traditional instrumentation alone, and a total of 120 anteroposterior radiographs and fifty-five lateral radiographs were analyzed for the group that was treated with use of the custom tibial planing device. RESULTS: The mean coronal alignment of the tibial component was 89.5 degrees +/- 2.1 degrees in the group that was treated with traditional instrumentation alone and 89.6 degrees +/- 1.4 degrees in the group that was treated with use of the custom planing device. Although the mean coronal alignment was not significantly different, the number of outliers was substantially reduced when the custom planing device was used. All 120 components that had been aligned with use of the custom planing device were within 3 degrees of the target coronal alignment, compared with only eighty-seven of the 100 components that had been implanted with use of traditional intramedullary alignment alone (p = 0.05). CONCLUSIONS: The use of a simple, inexpensive tibial planing device reduced the number of outliers due to tibial tray malalignment. Tibial varus has been associated with a higher risk of failure. Improving the accuracy of tibial component alignment may reduce the potential for poor clinical outcomes.     

Wedged tibial components for total knee arthroplasty

Severe coronal deformity of the knee is frequently associated with erosion of one tibial condyle. This can cause problems with fixation and alignment during total knee arthroplasty. If the tibia is cut to the level of the more worn side, valuable bone is sacrificed; if the less worn side is chosen, the deficiency must be filled with bone-graft, cement, or a prosthesis. Tibial components with an integral polyethylene wedge on the undersurface were introduced in 1980 for use in patients with a bony deficit on one tibial condyle. The authors believe that the Denham prosthesis (Biomet, Wales, U.K.) was the first knee arthroplasty to offer such spacers. Twenty-six patients with preoperative varus deformity in whom a wedged component was used were compared with 29 historic control subjects. None of the wedged components loosened after a median follow-up period of 8 years compared with loosening in five of the control subjects (P = .01). In three of the control subjects a fractured triangle of cement was present on the radiographs. Use of the wedges was not accompanied by an improvement in postoperative alignment. The authors conclude that the wedges resulted in improved fixation that was independent of postoperative alignment.     

Proximal tibial fracture following total knee arthroplasty

The patient was a 74-year-old man, with a history of total knee arthoplasty 14 years earlier, after having sustained a pathological fracture of the proximal diaphysis of the left tibia following a fall. Given the unstable nature of the fracture and the severe osteolysis noted below the total knee arthroplasty, surgical management 1 day after the fall entailed packing cancellous bone graft into the defect and realigning the fracture.