计算机导航在全膝关节置换中的应用

文题释义：导航下全膝关节置换：术中在患肢股骨侧及胫骨侧分别安装红外线反射球,通过红外线原理将信息传输到计算机里面,通过计算机重建患者的下肢力线及空间结构,从而指导医师正确截骨。该系统能降低医生的主观判断产生的失误,能够提高假体植入的准确性,改善患者膝关节功能及提高假体使用寿命。导航的优势：与传统膝关节置换手术相比,导航下膝关节置换能够提高术后下肢力线的准确性;能够有更好的伸屈间隙平衡;且术中不要打开股骨髓腔,减少了术后引流量。背景：随着精准医疗的发展,导航下膝关节置换越来越受到重视,其能够使假体植入更加准确,获得有更好精确的下肢力线,但同时也延长了手术时间。目的：探讨Aesculap Ortho-Pilot非影像依赖无线导航在全膝关节置换中的应用价值。方法：回顾性收集2017年4至11月安徽医科大学第一附属医院收治的42例单侧膝关节骨性关节炎患者病历资料,经同一手术医师完成初次全膝关节置换,按照手术方式分为2组：导航组在Ortho-Pilot非影像依赖无线导航辅助下进行全膝关节置换,非导航组进行常规的全膝关节置换,每组21例。记录两组手术时间、术后引流量;术后12个月拍摄负重X射线片,观察下肢机械轴线、胫骨机械轴近端内侧角、股骨机械轴远端外侧角、矢状面胫骨组件角与下肢力线偏差>3°的患者数量,同时评估患者膝关节活动度与膝关节功能HSS评分。试验获得安徽医科大学第一附属医院伦理委员会批准。结果与结论：①导航组手术时间长于非导航组(P < 0.05),术后引流量少于非导航组(P < 0.05);②术后12个月,导航组下肢机械轴线、股骨机械轴远端外侧角、矢状面胫骨组件角分离变量的误差均小于非导航组(P < 0.05),两组胫骨机械轴近端内侧角分离变量与下肢力线>3°的病例数比较差异无显著性意义(P > 0.05);③术后12个月,导航组膝关节活动度大于非导航组(P < 0.05),两组膝关节功能HSS评分比较差异无显著性意义(P > 0.05);④结果表明,计算机导航辅助全膝关节置换能够提高下肢力线的准确性、假体安放的准确性及膝关节活动度,但增加了手术时间,应用时应综合考虑其利弊。ORCID: 0000-0003-1243-9574(江正)中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

Radiographic outcome of limb-based versus knee-based patient specific guides in total knee arthroplasty

BackgroundPatient specific guides (PSG's) were developed to improve overall component alignment in total knee arthroplasty (TKA). The aim of this study was to undertake a comparative radiographic study of two commonly used PSG and determine whether the radiographic technique used to construct the PSG had a significant effect on overall alignment.MethodsThis prospective cohort study examined the accuracy of limb-based (n = 112) versus knee-based (n = 105) MR PSG in restoring the mechanical axis in three planes according to post-operative Perth CT scan protocol.ResultsLimb-based MR and knee-based MR PSG systems both restored overall hip–knee–ankle angle (HKAA), femoral coronal alignment, tibial coronal alignment, femoral sagittal alignment, tibial sagittal alignment and femoral rotation alignment to within 3° of a neutral mechanical axis with similar precision (91.1% vs. 86.7% p = 0.30, 97.3% vs. 96.2% p = 0.63, 97.3% vs. 97.1% p = 0.94, 94.6% vs. 89.4% p = 0.16, 90.2% vs. 81.0% p = 0.05, 91.1% vs. 86.7% p = 0.30, respectively). However, when the secondary outcome measure of alignment within 2° was assessed, limb-based MR PSG restored HKAA, femoral coronal and tibial sagittal alignment with greater precision than knee-based MR PSG (73.2% vs. 64.8% p = 0.016, 93.8% vs. 80.8% p = 0.004 and 82.1% vs. 62.9% p = 0.001, respectively).ConclusionsThe findings of this study recommend the use of limb-based MR PSG for improved precision in the restoration of neutral mechanical alignment over knee-based MR PSG in TKA.Level of EvidenceTherapeutic level III     

Contact kinematics of patient-specific instrumentation versus conventional instrumentation for total knee arthroplasty

BackgroundThe goal was to evaluate the joint contact kinematics of total knee arthroplasties implanted using patient-specific instrumentation (PSI) compared to conventional instrumentation (CI). We hypothesized that use of PSI would not significantly alter contact kinematics.MethodsThe study was a prospective randomized controlled trial, with equal allocation of fifty patients to PSI and CI groups. At two years post-operation, patients underwent weight-bearing stereo X-ray examinations at 0°, 20°, 40°, 60°, 80°, and 100° of flexion. The shortest tibiofemoral distance on each condyle determined the contact location. Magnitude of the shortest distance was measured and condylar separation was analyzed using thresholds of 0.5 and 0.75 mm. Kinematic measurements derived from the shortest distance included anteroposterior (AP) translation, excursion, axial rotation, and paradoxical anterior motion. Pivot position and cam/post contact were also investigated.ResultsThere were no differences (p > 0.05) in medial and lateral AP contact locations, excursions, and magnitude of anterior motion, or in axial rotation, pivot patterns, frequency of cam/post engagement, frequency of medial anterior motion, and condylar separation at a 0.75 mm threshold. Significant differences were found in frequency of lateral anterior motion (p = 0.048) and condylar separation at a 0.5 mm threshold (p = 0.010). Both groups displayed typical kinematics for a fixed-bearing posterior-stabilized implant.ConclusionsWe found no major differences in knee kinematics between PSI and CI groups, which suggest that PSI does not provide a significant kinematic advantage over conventional instruments.     

Little clinical advantage of computer-assisted navigation over conventional instrumentation in primary total knee arthroplasty at early follow-up

PurposeEven though computer-assisted navigation systems have been shown to improve the accuracy of implantation of components into the femur and tibia, long-term results are lacking and there is little evidence yet that navigation techniques also improve functional outcomes and implant longevity following total knee arthroplasty (TKA). The aim of this study was to summarize and compare the clinical outcomes of total knee arthroplasties (TKAs) performed using navigation-assisted and conventional techniques.MethodsThe study was conducted according to the guidelines described in the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statements. Methodological features were rated independently by two reviewers. A meta-analysis of randomized controlled trials (RCTs) or quasi- randomized controlled trials (qRCTs) was carried out to evaluate the efficacy of CAS versus conventional TKA. Data were pooled in fixed and random effects models and the weighted mean difference (WMD) and odds ratio (OR) were calculated. Heterogeneity across studies was determined, and subgroup analyses by the type of navigation system (image-based or image-free navigation system) were conducted.ResultsTwenty-one studies that included 2333 knees were collected from different countries. The surgical time was longer for CN TKA than for the conventional procedure. There was no significant difference in the Knee Society Score between the two groups at the 3-month and 6-month follow-up. The rates of postoperative complications in patients who had CN TKA were similar to those in the patients who had conventional TKA.ConclusionNo significant differences in short-term clinical outcomes were found following TKAs performed with and without computer navigation system. However, there is clearly a need for additional high-quality clinical trials with long-term follow-up to confirm the clinical benefits of computer-assisted surgery.     

Clinical alignment variations in total knee arthroplasty with different navigation methods

BackgroundWe compared the resulting alignment in 90° of flexion and in full extension after total knee arthroplasty (TKA) with two navigation systems using different techniques: a measured resection (MR) system and a gap — balancing (GB) system.MethodsVarus and valgus alignment in extension and flexion was compared in 100 consecutive patients who had TKA with an MR distal–femoral-cut-first technique at one institution and 100 consecutive patients in whom a GB tibial-cut-first technique was used at another institution. Alignment deviation of three degrees or more from neutral was considered an outlier.ResultsNo significant difference between the groups in coronal alignment in extension or flexion was found, but there were three times the number of outliers for clinical alignment in flexion for the MR group compared to the GB group.ConclusionsThe use of the GB tibial-cut-first computer-assisted TKA navigation may provide a more consistent clinical alignment in flexion than systems using an MR technique.Level of evidenceTherapeutic study. Level 2.     

股内侧肌入路计算机辅助设计全膝关节置换与传统方案的对比

BACKGROUND: In the treatment of primary knee osteoarthritis, total knee arthroplasty is a common treatment, but there are some shortcomings in the traditional operation, which may lead to early failure of the prosthesis.     

Postoperative morbidity and mortality following total knee arthroplasty with computer navigation

The incidence of postoperative complications following computer navigated total knee arthroplasty is unknown. There is no published evidence to support decreased morbidity compared to standard conventional technique. The Nationwide Inpatient Sample database was used to identify 101,596 patients who underwent total knee arthroplasty in 2005. Of these patients, 1156 were coded as having a computer-assisted procedure. Bivariate analysis and regression modeling were used to compare postoperative in-hospital outcomes between the computer-assisted and non-navigated cohorts. We found no differences in postoperative mortality or complications for the majority of our measured outcomes. Under multivariate regression analysis, computer navigation was associated with a lower rate of postoperative cardiac complications (odds ratio 0.40, p = 0.042), a shorter length of stay, and a trend towards fewer hematomas. Further clinical study is required to examine the possible association of computer navigation with postoperative morbidity following knee arthroplasty.     

Postoperative alignment in revision total knee arthroplasty,a comparison between intra and extra-medullary tibial alignment

BackgroundRevision total knee arthroplasty commonly involves stemmed components. If the diaphysis is engaged, this technique may be problematic for mechanical alignment (MA) in cases of tibial bowing, which are not infrequent (up to 30%).The aim of this study is to compare an intra-medullary(IM) and extra-medullary(EM) alignment method. We hypothesized that IM technique and canal-filling stems may result more frequently in valgus MA. On the other hand, an EM technique could produce less valgus knees but is at risk of creating MA outliers.MethodA retrospective radiographic analysis of revision TKAs was performed. The patients were divided to either the EM or IM alignment group and compared on the overall post-operative MA. The following parameters were measured on standing, long leg x-rays: Hip-knee-Ankle angle (HKA), mechanical lateral distal femoral angle and mechanical medial proximal tibial angle (mMPTA).Results119 cases of revision TKAs were included (EM = 80, IM = 39). There was a difference between the EM and IM group for the mean mMPTA (89.94° vs 90.92°, effect size = 0.45, p = 0.013) and HKA angle (1.64° vs 0.05°, effect size = 0.52, p = 0.0064). A higher proportion of IM patients were in overall valgus alignment (16/39, 41%) vs EM group (16/80, 20%, p = 0.0134). Both techniques showed the same proportion of outliers, defined as HKA angle more than 5 degrees from neutral mechanical alignment (11/80 vs 5/39, p = 0.286).ConclusionThe extra-medullary alignment method with short cemented stems creates less valgus mechanical alignment than the intra-medullary technique with press-fit stems, without creating more MA outliers.     

Patient specific cutting guides versus an imageless,computer-assisted surgery system in total knee arthroplasty

BackgroundPatient specific cutting guides (PSC) in total knee arthroplasty (TKA) have recently been introduced, in which preoperative 3-dimensional imaging is used to manufacture disposable cutting blocks specific to a patient's anatomy. The purpose of this study was to compare the alignment accuracy of PSC to an imageless CAS system in TKA.MethodsThirty-seven patients (41 knees), received a TKA using an imageless CAS system. Subsequently, 38 patients (41 knees), received a TKA using a MRI-based, PSC system.Postoperatively, standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, tibial component varus/valgus, and femoral component varus/valgus mechanical alignment were digitally measured. Each measurement was performed by two blinded, independent observers, and interclass correlations were calculated. A student's two-tailed t test was used to compare the two cohorts (p-value < 0.05 = significant).ResultsIn the PSC cohort, 70.7% of patients had an overall alignment within 3° of a neutral mechanical axis (vs. 92.7% with CAS, p = 0.02), 87.8% had a tibial component alignment within 2° of perpendicular to the tibial mechanical axis (vs. 100% with CAS, p = 0.04), and 90.2% had a femoral component alignment within 2° of perpendicular to the femoral mechanical axis (vs. 100% with CAS, p = 0.2). Interclass correlation coefficients were good to excellent for all radiographic measurements.ConclusionWhile PSC techniques appear sound in principle, this study did not demonstrate patient specific cutting guides to obtain the same degree of overall mechanical and tibial component alignment accuracy as a CAS technique.Level of evidenceIII: Retrospective cohort study.     

The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: Prospective control trial

BackgroundThe purpose of this study was to assess whether custom cutting blocks improve accuracy of component alignment compared to conventional TKA instrumentation.MethodsEighty primary TKA patients were enrolled in an open-label randomized prospective clinical trial and were divided into two groups, 40 custom cutting blocks and 40 conventional TKA instrumentations. The primary outcome was prosthetic alignment with respect to mechanical axis and epicondylar axis. Secondary outcomes included operative time, 24-hour postoperative blood loss and hemoglobin at discharged.ResultsThere were no statistical significant differences in the postoperative mechanical axis between the custom cutting blocks group and conventional TKA group, (95% vs. 87.5% within 3° of neutral mechanical alignment, p = 0.192). The average rotational alignment was statistically significantly different in the custom cutting blocks group (1.0° ± 0.6° vs. 1.6° ± 1.8° external rotation from epicondylar axis, p < 0.001). There were statistical significant differences in operation time between custom cutting blocks group and conventional group, skin to skin [57.5 ± 2.3 min vs. 62.1 ± 1.5,p < 0.001]. We found an improvement in group 1 compared with group 2 regarding the proportion of patients with postoperative blood loss within 24 h.ConclusionsCustom cutting blocks technique was a surgical procedure which provided better accuracy in rotational alignment but no statistical differences in mechanical axis, less operative time and reduced blood loss than the conventional TKA instrumentation in the majority of patients.     

A comparison of patient based outcome following knee arthrodesis for failed total knee arthroplasty and revision knee arthroplasty

Arthrodesis of the knee is an infrequently performed operation perceived by both patient and surgeon to have a poor outcome. This study compares functional outcome of knee arthrodesis following failed primary arthroplasty with that of revision knee arthroplasty in a matched patient group. Outcome was measured using the SF12 and Oxford Knee Score. Twelve patients underwent arthrodesis, of which eight were available for functional review at a mean of 53 months. No significant difference was found between the outcome scores of the two groups, although it is recognised that the numbers involved were low. Arthrodesis of the knee may be considered as a surgical option following failed arthroplasty when factors are present that may mitigate against an optimal result following revision knee arthroplasty.     

全膝关节置换过程中的假体旋转对位

背景：在全膝关节置换过程中对假体旋转对位争论的焦点目前仍集中在旋转对位的参照地标如何设定。 目的：综述全膝关节置换手术中假体旋转对位的相关临床和基础研究进展。 方法：广泛查阅全膝关节置换手术中假体旋转对位的解剖定位标志、定位方法、旋转对位的匹配、手术精确度等临床上遇到的相关文献。 结果与结论：许多研究表明,旋转对位不良,会导致膝前痛,胫股骨和髌股关节间的稳定性失衡,髌骨的运动轨迹失调,步态异常,胫骨侧聚乙烯平台的磨损加速,假体过早松动,出现关节半脱位和脱位,甚至需进一步手术翻修等问题。术中胫股骨侧假体的旋转对位时要综合利用所获得的各种信息,个别校正,必要时结合置换前的CT扫描来进行,以改善全膝关节置换疗效和远期生存率。     

Measurement of soft tissue imbalance in total knee arthroplasty using electronic instrumentation

The existence of soft tissue contractures in arthritis and the presence of soft tissue imbalance at the time of a total knee arthroplasty causing deformity in the coronal plane has been debated extensively. This discussion was based on the use of instrumentation which tensed the medial and lateral soft tissues in an uncontrolled manner during the operation. Previous work by this research team has developed a surgical instrument to quantify soft tissue imbalance independently of the compressive passive loads through the knee. In order to validate this assumption, an electronic measuring system was developed to record the soft tissue imbalance at 0.25 mm distraction intervals of the knee. This soft-tissue measuring system consists of a surgical instrument containing electronic transducers, an analogue conditioning unit and a portable computer. The surgical instrument introduces a pivot to the centre of the knee in the coronal plane so that the clockwise and counterclockwise moments produced by the collateral soft tissues produce an angular deviation at the equilibrium position. Measurements of angular deviation and separation gap are recorded by the electronic transducers. Eight patients were measured whilst undergoing total knee replacement at Bretby Hall Orthopaedic Hospital. The mean change in angular deviation over an average distraction of the knee of 7.15 mm was 0.4° with a standard deviation of 0.4. It is concluded that this is an acceptable error band for surgical measurement, and soft tissue imbalance can be defined as angular deviation independently of the passive compressive loads through the knee.     

个性化截骨工具辅助下人工全膝关节置换与传统人工全膝关节置换手术精确度及临床疗效比较

目的比较3D打印个性化截骨工具辅助(patient-specific instrumentation,PSI)下人工全膝关节置换术(total knee arthroplasty,TKA)与传统TKA的手术精确度和临床疗效。方法自2017年9月至2018年12月,将40例拟接受初次膝关节置换患者随机分为2组,每组均为20人。一组应用个性化截骨工具辅助TKA手术(PSI组),另一组接受传统TKA(对照组)。比较两组患者的冠状面下肢机械轴线、手术时间、术中出血量、术后引流量以及HSS评分。结果对照组和PSI组的手术时间分别为(103.3±18.7) min和(91.3±15.7) min;术中出血量分别为(372.0±53.0)mL和(332.8±47.0)mL;术后引流量分别为(378.8±97.2)mL和(315.0±89.0)mL。两组手术时间、术中出血量、术后引流量比较差异均有统计学意义(P0.05)。对照组和PSI组术后2周HSS评分分别为(89.3±2.8)分和(88.7±2.9)分,两组比较差异无统计学意义(P0.05)。对照组和PSI组术后全下肢力线差值分别为(1.9±1.1)°和(1.2±1.0)°,冠状面股骨假体角度(frontal femoral component angle,FFC)差值分别为(2.1±1.1)°和(1.1±0.9)°,两组比较差异有统计学意义(P0.05)。冠状面胫骨假体角度(frontal tibia component angle,FTC)差值分别为(1.3±0.8)°和(1.4±0.8)°,两组比较差异无统计学意义(P0.05)。结论PSI辅助TKA较传统TKA手术时间更短、术中出血量更少,并且术后冠状面全下肢力线及股骨力线的改善优于传统TKA手术。     

Sequential versus automated cutting guides in computer-assisted total knee arthroplasty

The accuracy and efficiency of automated cutting guides in CAS systems have not been previously compared with conventional CAS techniques. Therefore, it is not yet clear if these more advanced technologies are warranted. We hypothesized that a novel automated cutting guide with CAS for total knee arthroplasty would be more efficient and more accurate than conventional navigation with sequential cutting blocks. Twelve cadaver legs were used in total. Each leg was randomly assigned to either an automated guide positioning or a conventional freehand computer-navigated guide positioning. The guide positions postosseous fixation and the final bone-cut surfaces were digitized and compared to the targeted cutting planes. The final location of the impacted trial implant was also digitized and compared to the planned implant location. The time for each step and the total time taken to prepare the femur were measured for both groups. The mean femoral preparation time was shorter with the automated cutting guide than the conventional method (5.5 min versus 13.8 min, p < 0.001). The average deviation in the final bone resections from the planned resections was significantly lower for the automated cutting guide in the frontal/rotational plane (0.55° versus 1.1°), sagittal plane (0.75° versus 2.0°), and cut height direction (0.56 mm versus 1.6 mm). Therefore, based on these results, we concluded that automated cutting-guide positioning resulted in more efficient and more accurate femoral cuts in comparison to the conventional navigation method in a cadaveric model.     

计算机导航技术辅助全髋关节置换的系统分析

背景：传统手术方法依赖术者的经验和目测解剖标志来安置髋臼假体往往会产生偏差,而在术中应用计算机导航技术可以很好地提高髋臼假体位置的精确度。 目的：研究全髋关节置换应用计算机导航系统对髋臼假体植入位置精度的影响及临床意义。 方法：计算机检索Cochrane Library、MEDLINE、EMBASE、中国生物医学文献数据库、中国期刊全文数据库,手工检索相关的中文杂志,纳入符合要求的临床试验,用RevMan5.0.18软件进行统计分析。 结果与结论：共纳入9篇临床试验合计695例。Meta分析结果显示：与传统手术相比,计算机导航技术在全髋关节置换后髋臼假体位置放置更精准超[RR=0.22,95%CI(0.14~0.34),P < 0.000 01]、双下肢不等长较传统手术轻[RR=-4.61,95%CI(-7.74~-1.48),P=0.004];而外展角度[RR=-1.76,95%CI(-5.02~1.50),P=0.29]、前倾角度[RR=-1.28,95%CI(-5.68~3.12),P=0.57]、术后脱位率[RR=1.25,95%CI(0.05~31.66),P=0.89]差异均无显著性意义。提示导航技术与传统手术在髋臼位置的精确度方面差异并无显著性意义。     

运动学对线和机械力学对线指导全膝关节置换效果的Meta分析

文题释义： 运动力学对线：是行全膝关节置换时的一种下肢对线方法,尽可能还原膝关节患关节炎前的运动状态。 机械力学对线：该对线方法已指导全膝关节置换手术近30年,机械力学对线技术的目标是恢复髋-膝-踝0°角,从而使整个下肢恢复到中立位,近些年研究发现该方法指导的全膝关节置换术后1/5患者对置换效果不满意。 背景：机械力学对线技术虽然保证了膝关节假体的长期生存率,但是仍有部分全膝关节置换患者对置换效果及术后膝关节功能不满意。 目的：采用Meta分析的方法评价运动学对线技术和机械力学对线技术指导全膝关节置换的效果。 方法：检索运动学对线和机械力学对线指导全膝关节置换的临床对照研究文献,检索范围包括中国生物医学文献数据库、万方数据、中国知网、维普数据、PubMed、Cochrane图书馆及Embase,检索年限为建库日期至2019年7月。对检索到的文献进行筛选、质量评价及数据提取,并采用Review Manager 5.3软件进行统计分析。 结果与结论：①共纳入12篇文献,包括945例患者,其中运动学对线组470例,机械力学对线组475例;②荟萃分析结果显示,手术时间方面运动学对线组比机械力学对线组更短[MD=-15.44,95%CI(-27.16,-3.71)],西安大略和麦克马斯特大学骨关节炎指数运动学对线组优于机械力学对线组[MD=-8.40,95%CI(-15.39,-1.40)],牛津大学膝关节评分运动学对线组优于机械力学对线组[MD=4.72,95%CI(0.24,9.21)],机械力学对线组术后的机械外侧股骨远端角及机械内侧胫骨近端角显著大于运动学对线组,以上研究P均< 0.05;③运动学对线组与机械力学对线组在平均住院日、出院前最远行走距离、膝关节协会评分、膝关节伸直角度、术后并发症方面差异无显著性意义(P均> 0.05);④提示运动学对线指导全膝关节置换后的膝关节功能优于机械力学对线,但影像学和围术期结果类似,且术后未增加并发症发生率。说明运动学对线可作为一种下肢力线对线方法来指导全膝关节置换。 ORCID: 0000-0002-3786-6305(赵春涛) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

Comparison of MRI- and CT-based patient-specific guides for total knee arthroplasty

BackgroundThe patient-specific guide for total knee arthroplasty (TKA) is created from the data provided by magnetic resonance imaging (MRI) or computed tomography (CT) scans. It remains unknown which imaging technology is suitable for the patient-specific guide. The purpose of this study was to compare the accuracy of implant positioning and operative times between the two types of patient-specific guides for TKA.MethodsForty arthritic knees were divided into two treatment groups using MRI-based (PS-MRI group) or CT-based (PS-CT group) patient-specific guides in this prospective, comparative study. The guide in the PS-MRI group had a cutting slot, whereas that in the PS-CT group only had a pin locator. The operative times were compared between the two groups. The angular error and number of outliers (deviations > 3°) of the implant position using pre- and postoperative CT were investigated in both groups.ResultsThe mean operative time was significantly shorter in the PS-MRI group (109.2 ± 16.5 min) than in the PS-CT group (129.5 ± 19.4 min) (p < 0.001). There were no significant differences in the accuracy of the implant position regarding the coronal, sagittal, and axial planes between the groups (p > 0.05).ConclusionsTo reduce the operative time, guides with additional functions, such as cutting and positioning, should be used. Both CT- and MRI-based-guides would result in the same accuracy in three planes but high inaccuracy in the sagittal plane. The use of patient-specific guide based on MRI might not be cost-effective.Level of evidence: level 2.     

Training benefits of computer navigated total knee arthroplasty

BackgroundComputer navigation aims to improve the surgical accuracy of total knee replacement by more reliably placing the cutting blocks in the optimum location in order to create a neutral mechanical axis. Aside from the obvious clinical benefit to the patient, we believe computer navigation has a valuable role as a training tool. The aim of this study is to demonstrate the effectiveness of computer navigation as a training tool in total knee arthroplasty.MethodsWe performed a training exercise using Sawbone plastic models to simulate four common sources of error in the saw technique; 1. cutting guide movement due to inadequate fixation, 2. the effect of using slotted or open cutting guides, 3. the effect of bending the saw blade, and 4. the effect of recutting on the accuracy of the intended resection.ResultsWe found that bony resection errors resulted from; use of less than three pins to fix the cutting guide, use of open cutting guides, deliberate and inadvertent “hanging” or “lifting” of the saw on the cutting guide and recutting after moving the cutting guide.ConclusionThe immediate feedback provided by computer navigated TKA allows surgeons and trainee surgeons the opportunity to improve the accuracy of their technique and increase awareness of their individual sources of error in TKA.Clinical relevanceUsed as a teaching tool, computer navigation can immediately identify errors in surgical technique and target subsequent training to minimise these errors. Training can be conducted whilst ensuring there is no detriment to patient safety.     

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.