Dynamic in-vivo tibio-femoral and bearing motions in mobile bearing knee arthroplasty

To determine the tibio-femoral and bearing motions in well functioning mobile bearing total knee arthroplasties, a quantitative analysis by means of fluoroscopy was carried out during stair ascending, chair rising-sitting and step up-down motor tasks. Femoral and tibial component positions were obtained using a CAD-model-based shape matching technique. Direct measurement of mobile bearing motion was carried out by tracking previously inserted tantalum beads. A relatively small motion of the bearing was observed. The advantage of self-alignment claimed for the mobile bearing arthroplasty seems to be confirmed by subject-specific ranges of motion exhibited by these patients. It has also been demonstrated that these total knee arthroplasties, which are not fully conforming in flexion, provide little constraint to antero-posterior motion, leading to a kinematic pattern very similar to an ACL deficient knee.     

The immediate effect of navigation on implant accuracy in primary mini-invasive unicompartmental knee arthroplasty

The success of unicompartmental knee arthroplasty (UKA) is highly dependent on the accuracy of the component alignment. Objective of the present study was to evaluate the immediate effect of image-free computer navigation technology on implant accuracy in primary mini-invasive UKA. This study reviews 40 patients with primary isolated arthritis of the medial compartment of the knee that underwent unicompartmental knee arthroplasty through a minimally invasive approach. A cohort of the 20 most recent consecutive UKA's implanted with standard instrumentation was followed by a cohort of the very first 20 consecutive cases after conversion to the navigated technique. There was no variability regarding implant (Oxford meniscal unicompartmental knee system--Biomet Orthopedics, Inc., Warsaw, Indiana 46580, USA), surgeons and surgical technique, except for the use of the navigation system (Treon plus--Medtronic Inc., Minnesota, MI, USA). The axis alignment and accuracy of implant positioning was measured on postoperative long-leg standing radiographs and standard lateral X-rays with regard to the valgus angle and the coronal and sagittal component angle. In addition, preoperative deformities of the mechanical leg axis, tourniquet time, age, gender, and body mass index were correlated. Statistical analyses were performed using the SPSS 14.0 (SPSS Inc., Chicago, IL, USA) software package. Optimal implant alignment including all measurements in the desired angular range was significantly (P=0.041) higher in the navigated cohort. Navigation eliminated outliers in the frontal mechanical alignment and coronal orientation of the femoral component totally and significantly (P<0.02). Furthermore, navigation narrowed the range of outliers in all other planes of component orientation. There were no statistically significant differences in the mean numerical values between the cohorts, except for the frontal mechanical alignment (P<0.009) and coronal tibial alignment (P<0.037). The average tourniquet time was increased by 10.95 min in the navigated cohort. Our results indicate that navigation immediately improves accuracy of bone cuts and reduces the number of outliers with implementation in UKA.     

Necrotizing fasciitis of the knee following primary total knee arthroplasty

Necrotizing fasciitis is a rare, life-threatening and rapidly spreading soft-tissue infection that results in necrosis of the muscle, fascia and surrounding tissue. It can be result of a polymicrobial synergistic infection or a streptococcal infection. The authors report a case of necrotizing fasciitis occurring in the knee of a 65-year-old woman following an uneventful primary total knee arthroplasty and resulting in above-the-knee amputation. Having in mind severe infections like necrotising fasciitis, one should be aware of the possibility of such postoperative complications especially in patients with risk factors even in routine procedures like a total knee arthroplasty.     

The effect of posterior tibial slope on knee flexion in posterior-stabilized total knee arthroplasty

Purpose

To evaluate and quantify the effect of the tibial slope on the postoperative maximal knee flexion and stability in the posterior-stabilized total knee arthroplasty (TKA).

Methods

Fifty-six patients (65 knees) who had undergone TKA with the posterior-stabilized prostheses were divided into the following 3 groups according to the measured tibial slopes: Group 1: ≤4°, Group 2: 4°–7° and Group 3: >7°. The preoperative range of the motion, the change in the posterior condylar offset, the elevation of the joint line, the postoperative tibiofemoral angle and the preoperative and postoperative Hospital for Special Surgery (HSS) scores were recorded. The tibial anteroposterior translation was measured using the Kneelax 3 Arthrometer at both the 30° and the 90° flexion angles.

Results

The mean values of the postoperative maximal knee flexion were 101° (SD 5), 106° (SD 5) and 113° (SD 9) in Groups 1, 2 and 3, respectively. A significant difference was found in the postoperative maximal flexion between the 3 groups (P < 0.001). However, no significant differences were found between the 3 groups in the postoperative HSS scores, the changes in the posterior condylar offset, the elevation of the joint line or the tibial anteroposterior translation at either the 30° or the 90° flexion angles. A 1° increase in the tibial slope resulted in a 1.8° flexion increment (r = 1.8, R ² = 0.463, P < 0.001).

Conclusion

An increase in the posterior tibial slope can significantly increase the postoperative maximal knee flexion. The tibial slope with an appropriate flexion and extension gap balance during the operation does not affect the joint stability.

Level of evidence

Retrospective comparative study, Level III.     

Legion假体在膝外翻畸形初次全膝关节置换手术中应用疗效

目的探讨Legion假体在膝外翻畸形初次全膝关节置换手术中的临床应用疗效。方法回顾性分析沈阳军区总医院骨科2012年1月至2015年12月收治的膝外翻畸形患者32例(37膝)。记录患者术后髌股轨迹、切口愈合情况、膝外翻矫正角度、膝关节Harris评分(HSS)。结果所有患者术后均获得随访。32例患者膝关节髌股轨迹良好,切口愈合情况佳,无感染发生。34膝完全矫正了膝外翻畸形,仅余3膝存在3°~5°膝外翻遗留。患者HSS评分由术前34.5分提升至术后87.0分。结论在膝外翻畸形患者的初次膝关节置换手术中应用Legion假体可以达到满意的手术疗效,术后患者膝关节稳定,大部分患者的膝外翻畸形得到了纠正,患者在术后早期功能锻炼即可达到屈曲90°、伸直0°。     

Revision after early aseptic failures in primary total knee arthroplasty

The purpose of this study was to evaluate cases of early aseptic failures presented during the first 5-year follow-up in a group of 981 primary total knee arthroplasty (primary TKA). Predisposing factors as well causes of failures and postoperative complications in different groups of aseptic failures were re-assessed and compared to a control group. A retrospective and cohort study compared one group of 944 primary TKA without surgical revision (890 patients) (Group A) with 22 primary TKA (22 patients) (Group B) that had revision TKA secondary to aseptic failure during the first five years follow-up. The cases of isolated patellar button replacement (n = 8) and infection (n = 7) were not considered in this study. All patients underwent a systematic assessment that included clinical and radiographic examinations, and IKS scores. Aseptic failure was more prevalent at the first 2-year follow-up (63%). TKA loosening (n = 11) and undiagnosed pain (n = 7) were considered the most frequent modes of failures, and laxity (n = 1) was a very rare early cause of failure. The aseptic failure group was characterized as average 5 years younger with a greater number of previous knee surgeries, lower IKS scores improvement, and more postoperative pain compared to control group, despite the fact that the aseptic failure group showed a prevalence of cases during the first 2-year follow-up. Inside this group, the undiagnosed pain group had lower improvement of IKS scores, a remarkable prevalence in prior surgical procedure (71%) and a minor mean interval between primary and revision TKA (11.6 months).     

The effect of patellar thickness changes on patellar tilt in total knee arthroplasty

We hypothesized that changes in patellar thickness following patellar resurfacing affect patellar tilt in total knee arthroplasty (TKA) patients. The study enrolled 272 TKAs and categorized them into four groups according to change in patellar thickness: (A) thinner by 1 mm or more, (B) equal or thinner by less than 1 mm, (C) thicker by 1 mm or less, and (D) thicker by more than 1 mm. Patellar tilt angle was measured postoperatively using Merchant radiography. There were no significant differences in postoperative patellar tilt among groups A, B, and C (n.s). However, the postoperative patellar tilting angle of group D was significantly higher than that of all other groups (P < 0.05). Postoperative patellar tilt increased when the postoperative patella was >1 mm thicker than the preoperative patella.     

The effect of knee position on blood loss and range of motion following total knee arthroplasty

Purpose  

This study prospectively assessed the effects of knee position on blood loss and range of motion after primary total knee arthroplasty (TKA).     

The femoral sulcus in total knee arthroplasty

The position of the femoral sulcus relative to the midline of the distal femoral resection in total knee arthroplasty (TKA) was studied to determine if centralized placement of the femoral component on the distal femur was justified in terms of aligning the prosthetic sulcus with the native femoral sulcus. The location of the femoral sulcus was studied in 112 consecutive patients undergoing TKA. The mean sulcus position was 0.7 mm lateral to the midline of the distal femoral resection (SD 1.4, 95% CI, 0.5–1.0 mm). However, the variation in sulcus positions ranged from 4 mm medial to 4 mm lateral to the midline. The mean sulcus position in valgus knees was 1.0 mm lateral to the midline (SD 1.8), and that in varus knees was 0.7 mm lateral to the midline (SD 1.2) (P = 0.501). It appears prudent to centre the femoral component on the native sulcus rather than the midline of the distal femoral resection, so as to ensure accurate alignment of the prosthetic sulcus with the native sulcus and to encourage normal patella tracking.     

Causes of failure and etiology of painful primary total knee arthroplasty

The review provides an overview of the causes of failure and the many different aetiologies of a painful primary total knee arthroplasty (TKA). They can be classified into extra- and intraarticular disorders, the latter being divided into biological and mechanical origins. Whereas biological aetiologies like infections have remained stable over time, other causes of failure have changed. In the early times of knee arthroplasty, they were mainly related to technical insufficiencies. A better understanding of knee arthroplasty, patients’ increasing functional demands as well as a continuous development of TKA techniques generated newer problems, which are increasingly related to the functioning of the soft-tissue envelope of the knee. From a therapeutic point of view, three situations can be considered: functional problems not needing reoperations, causes of reoperations not needing an exchange of prosthetic components as well as reoperations with exchange of at least one prosthetic component.     

Shed blood re-transfusion provides no benefit in computer-assisted primary total knee arthroplasty

Purpose  

This matched case-cohort retrospective study examined the effectiveness of shed blood re-transfusion in reducing the need for allogeneic blood transfusion in computer-assisted primary cemented total knee arthroplasty (TKA).     

Effects of total knee arthroplasty for primary knee osteoarthritis on postural balance: A systematic review

BackgroundKnee osteoarthritis is often related to physical function impairment. Although total knee arthroplasty is considered effective for advanced cases of knee osteoarthritis, its effects on postural balance is a topic of debate.Research questionWhat are the effects of total knee arthroplasty for primary knee osteoarthritis on postural balance compared to preoperative status and/or to healthy controls?.MethodsLongitudinal studies (with more than 1-month follow-up) assessing postural balance measures (either clinical-based such as balance scales or laboratory-based such as postural sway) were considered eligible and selected in a 2-phase process. Six main electronic databases were searched, complemented by 3 grey literature sources. The risk of bias was evaluated using the Joanna Briggs Institute Critical Appraisal Tools.ResultsA total of 19 studies were included for qualitative synthesis, of which 14 had low and 5 had a moderate risk of bias. The follow-up period ranged from 1–24 months. Most studies (n = 11) presented comparisons to preoperative status only. From these, 7 studies reported relevant improvements in postural balance, 2 reported partial improvements, and 2 no improvements. The remaining studies (n = 8) presented comparisons to healthy controls and, although improvements following total knee arthroplasty were consistently observed, only one study reported postural balance measures comparable to that of controls.ConclusionsThe majority of studies reported relevant improvements (especially in clinical-based measures) compared to preoperative evaluations, although inconsistencies were found possibly due to variability in studies' populations, assessment tools, and follow-up times. Despite this, persistent deficits in postural balance were commonly observed when compared to healthy controls.SignificanceThis evidence synthesis could better inform clinicians and researchers about the therapeutic effects and limitations of total knee arthroplasty concerning postural balance. Standardization of assessment tools is recommended to strengthen the certainty of cumulative evidence.     

The effect of total synovectomy in total knee arthroplasty: a prospective randomized controlled study

Purpose  

The apparent synovial hypertrophy in some cases of noninflammatory knee osteoarthritis suggests that total synovectomy may provide beneficial inflammatory and pain relief after total knee arthroplasty. The aim of the study was to compare the effect of synovectomy on the postoperative pain, bleeding and functional outcome after surgical treatment of knee osteoarthritis.