A new landmark for measuring tibial component rotation after total knee arthroplasty

BackgroundExisting methods for assessment of total knee arthroplasty (TKA) component rotation on computed tomography (CT) scans are complex, especially in relation to the tibial component. Anecdotal evidence from our practice pointed towards a potential new landmark. The study aims were to check the prevalence of this landmark, define tibial component rotation in relation to it and demonstrate its reliability.MethodsTwo hundred and eleven CTs undertaken following TKA were reviewed for presence of the landmark. A protocol to measure tibial component rotation in relation to this landmark was developed and the rotation measured using this method and Berger's protocol. Thirty one of the 211 CT scans were measured twice by two observers. Reliability was calculated using the Intraclass Correlation Coefficient (ICC).ResultsThe new landmark of a flat area on the lateral cortex of the tibia inferior to the tibial component was identified on all scans. Median tibial component rotation measured using our protocol was 0.0° ± 5.4° and ? 9.2° ± 5.5° using Berger's protocol. Intra-observer reliability with the new method was excellent (ICCs of 0.899 and 0.871) and inter-observer reliability was good (ICCs of 0.734 and 0.836).ConclusionsThe new landmark had a very high prevalence and could be used to define tibial component rotation. This measurement of tibial component rotation had acceptable reliability. This landmark has potential for use in the radiological assessment of tibial component rotation following TKA. Further work is required to determine its relationship to anatomical structures and symptoms of tibial component mal-rotation.     

Three dimensional morphometry of the knee to design the total knee arthroplasty for Chinese population

Anthropometric data on the proximal tibia and distal femur of 172 normal knees (94 male knees, 78 female knees) were obtained using three dimensional computer tomographic measurements. We measured the tibial mediolateral (tML) and tibial anteroposterior (tAP) dimension in resected proximal tibia surface, femoral mediolateral (fML) and femoral anteroposterior (fAP) dimension in resected distal femur surface. The measurements were compared with the similar dimensions of five total knee prostheses conventionally used in China. We found that in the smaller sized prostheses the tibial mediolateral dimension was undersized, while in the larger size prostheses the tibial mediolateral dimension was overhang. For all sizes of prostheses the femoral mediolateral dimension was overhang. We found a progressively decreased in the aspect ratio (ML/AP %) with an increasing anteroposterior dimension both in the tibia and femur, as compared to the constant aspect ratio shown by the conventional total prostheses. Male had larger values in mediolateral dimension and aspect ratio than female under a given anteroposterior dimension both in the tibia and femur. There were strong correlations between measurements of the tibia and femur. The results of this study may provide guidelines for designing suitable total knee prosthesis for the Chinese population, especially for design of gender-specific prostheses.     

Influence of tibial component rotation on short-term clinical outcomes in Oxford mobile-bearing unicompartmental knee arthroplasty

Background

Malposition of tibial components is an important factor for complications in unicompartmental knee arthroplasty (UKA), but the direct relationship between clinical outcomes and position of tibial component remains unknown. We aimed to investigate whether tibial component rotation in the axial plane could affect clinical outcomes after UKA.

External rotation of the tibial component should be avoided in lateral unicompartmental knee arthroplasty

BackgroundLateral unicompartmental knee arthroplasty (UKA) leads to good clinical outcomes for isolated lateral osteoarthritis. However, the impact of the tibial component position on postoperative outcomes in lateral UKA is yet to be determined.PurposeThis study investigated the influence of tibial component malposition on clinical outcomes in lateral UKA.MaterialsThis was a retrospective study of 50 knees (mean age 73.5 years) who underwent lateral UKA between September 2013 and January 2019. The Oxford Knee Score (OKS), Knee Society Score – Knee (KSSK), and Knee Society Score – Function (KSSF) were evaluated. The coronal alignment, posterior slope of tibial component, tibial component rotation relative to Akagi’s line (angle α), and femoral anteroposterior (AP) axis (angle β) were measured postoperatively. The average follow up period was 2.3 (range, 1–4.9) years.ResultsClinical scores were significantly improved after lateral UKA. The mean coronal alignment was 0.9° ± 3.2° varus (range, 9.1° varus to 5.5° valgus), the mean posterior slope was 6.8° ± 3.8° (range, 0.8° to 14.8°). The mean α and β angles, were 4.1° ± 5.8° (range, −9.7° to 16.5°) and 6.7° ± 7.1° (range, −7.0° to 20.5°) external rotation. The angle α had significant negative correlations with postoperative OKS (r = −0.36), KSSK (r = −0.28), and KSSF (r = −0.39), and angle β had significant negative correlations with postoperative OKS (r = −0.34) and KSSK (r = −0.46).ConclusionExcessive external rotation of the tibial component could negatively influence the postoperative outcomes of lateral UKA.     

华南人胫骨平台后倾角的三维测量及临床意义

目的　测量华南成人正常胫骨平台后倾角数据,为改进及设计适合中国人（尤其华南人）的膝关节假体和在全膝关节置换术中行合理的胫骨截骨,提供参考和依据。 方法　对80例华南志愿者膝关节行薄层螺旋CT扫描后,用Mimics软件重建出三维模型,导入Unigraphics NX软件中测量其胫骨内外侧平台的后倾角。 结果　胫骨内侧平台后倾角,左侧（8.47±3.42）°,右侧（7.84±3.30）° ;男性（7.69±　2.89）°,女性（8.62±3.74）°;平均（8.16±3.37）°;胫骨外侧平台后倾角,左侧（6.89±3.42）°,右侧（6.82±2.78）°;男性（6.84±2.82）°,女性（6.87±3.01）°;平均（6.85±2.90）°。胫骨内、外侧平台后倾角在不同性别、侧别间无显著性差异（P＞0.05）,但胫骨内侧平台后倾角明显大于胫骨外侧平台后倾角（P＜0.05）。 结论　华南成人正常胫骨平台后倾角的个体差异较大,均值小于国内其他地区报道和国外大多数同类研究。     

Anthropometric measurements of knee joints in Thai population: Correlation to the sizing of current knee prostheses

Anthropometric data on the distal femoral condyle and the proximal tibia of 200 knees in 200 Thai subjects were measured using magnetic resonance imaging (MRI). The data including the resected femoral anterior-posterior (AP) length, the resected femoral medial-lateral (ML) width, the resected tibial AP length and the resected tibial ML width were measured. A characterization of the aspect ratio (the ML to AP dimensions) was made for the distal part of the femur and the aspect ratio (the AP to ML dimensions) was made for the proximal part of the tibia. All parameters were compared to the size of the total knee prosthesis with four prosthetic systems which currently used in Thailand: NexGen (Zimmer), P.F.C. Sigma (Depuy-Johnson & Johnson), Genesis II (Smith & nephew), and Scorpio (Stryker). The results of this study could provide fundamental data for the design of knee prostheses suitable for the Thai population.     

Proximal tibial morphology is associated with risk of trauma to the posteromedial structures during tibial bone resection reproducing the anatomical posterior tibial slope in bicruciate-retaining total knee arthroplasty

BackgroundA tibial cut with the native posterior tibial slope (PTS) is a theoretical prerequisite in bicruciate-retaining total knee arthroplasty (BCRTKA) to regain physiological knee kinematics. The present study reveals tibial morphological risk factors of trauma to the posteromedial structures of the knee during tibial bone resection in BCRTKA.MethodsFifty patients undergoing BCRTKA for varus knee osteoarthritis were analyzed. A three-dimensional tibial bone model was reconstructed using a computed tomography-based preoperative planning system, and the coronal tibial slope (CTS) and medial PTS (MPTS) were measured. Then, we set the simulated tibial cutting plane neutral on the coronal plane, posteriorly inclined in accordance with the MPTS on the sagittal plane, and 9 mm below the surface of the subchondral cortical bone (i.e., 11 mm below the surface of the cartilage) of the lateral tibial plateau. The association between the tibial morphology and the distance from the simulated cutting plane to the semimembranosus (SM) insertion (Dsm) was analyzed.ResultsOf the 50 patients, 19 (38%) had negative Dsm values, indicating a cut into the SM (namely, below the posterior oblique ligament) insertion. The MPTS was negatively correlated with Dsm (r = −0.396, p = 0.004), whereas the CTS was positively correlated with Dsm (r = 0.619, p < 0.001). On multivariate linear regression analysis, the MPTS and CTS were independent predictors of Dsm.ConclusionIn the setting of tibial cuts reproducing the native MPTS in BCRTKA, patients with larger PTS and smaller CTS had more risk of trauma to the posteromedial structures.     

A new technique for determining the rotational alignment of the tibial component during total knee arthroplasty

BackgroundWe evaluated the effectiveness of our new technique “Range of motion-anatomical (ROM-A) technique” which is the combination of the self-positioning technique “Range of motion (ROM) technique” and the anatomical landmarks technique in determining the tibial component (TC) rotation alignment in total knee arthroplasty (TKA) using a navigation system.MethodsThis retrospective study included 103 knees who underwent TKA. The ROM-A technique was consisted of two steps. First, the TC was set and marked by the ROM technique in knee extension. Second, the TC was set according to the marking in the knee flexion and the component rotational angle relative to the anatomical tibial anteroposterior (AP) axis was adjusted between 0° and 10° external rotation using the navigation system. The rotational angle of TC relative to the anatomical AP axis was measured using postoperative computed tomography. Moreover, the hypothetical rotational angle of the TC in the ROM technique was calculated only from the intraoperative difference between the two techniques.ResultsThe actual rotational angle by the ROM-A technique was externally rotated 3.0°, and the rotational outlier occurred in 3.0%. A significant difference in outlier rate was observed between the two techniques (p = 0.03). The hypothetical rotational angle of TC determined by the ROM technique (the first step only in the ROM-A technique) was externally rotated 4.6° and the TC rotational outlier (difference to AP axis: >10°) occurred in 11.7%.ConclusionUsing the ROM-A technique, the TC was finally fixed in almost all targeted rotational positions, and this technique could reduce the anatomical rotational outlier compared with the ROM technique.     

Effect of tibial component overhang on survivorship in medial mobile-bearing unicompartmental knee arthroplasty

BackgroundSome studies have shown that the position of the tibial component in Oxford unicompartmental knee arthroplasty with a mobile bearing will affect the clinical outcome of patients. Hence, our study aimed to investigate the relationship between the overhang distance of the tibial component and the survival of the implant.MethodsA retrospective analysis of patients who underwent unicompartmental knee arthroplasty at the same institution from 2014 to 2018 was presented. The study was divided into three groups: minor underhang group (underhang between −3 and 0 mm); minor overhang group (overhang 0–3 mm); and major overhang group (overhang ≥ 3 mm). Demographic and clinical profile characteristics of each group were compared, and survival curves of each group were also compared using Kaplan–Meier and modeled using multivariate Cox regression.ResultsA total of 351 knees were included in this study with a minimum follow up of three years and a mean follow up of 4.8 ± 1.5 years. The revision rates in each group were 3.6% (minor underhang group), 2.7% (minor overhang group), and 20.9% (major overhang group) (P < 0.001). From the three groups’ cumulative survival rates, the major overhang group was significantly lower than the other two groups (log rank P < 0.001). Multivariate Cox regression showed an association between the major overhang group and implant survival rate (hazard ratio = 7.515, 95% confidence interval = 2.500–22.593, P < 0.001)ConclusionThe risk of revision will increase if the tibial component overhangs more than 3 mm medially. Moreover, the reasons for revision are generally bearing dislocation and aseptic loosening.     

Preoperative rotational assessment of the distal femur with CT may cause femoral component malrotation in TKA

BackgroundBefore total knee arthroplasty (TKA), rotational assessment of the distal femur can be performed using either magnetic resonance imaging (MRI) or computed tomography (CT). Until now, there has been no study comparing the two modalities regarding rotational assessment of the distal femur in the same patients.MethodsWe retrospectively reviewed the preoperative CT and MRI images of 110 knees in 110 patients who underwent TKA. In the axial planes of CT and MRI scan, the posterior condylar axis (PCA), anatomical transepicondylar axis (aTEA), and perpendicular line to anteroposterior axis (pAPA) were identified; the angles between these studied lines were calculated. During TKA, the angles measured on the preoperative CT and MRI were compared with the measurements obtained in the intraoperative field.ResultsThe mean aTEA-PCA angle was 6.2 ± 1.9° with CT and 5.1 ± 1.8° with MRI. The mean pAPA-PCA angle was 4.7 ± 2.1° with CT and 3.5 ± 2.0° with MRI. The mean aTEA-PCA (1.1 ± 1.3°, p = 0.001) and pAPA-PCA (1.2 ± 1.2°, p = 0.012) angles significantly differed between CT and MRI. Intra-operatively, the mean aTEA-PCA angle was 4.7 ± 1.1° and the mean pAPA-PCA angle was 3.2 ± 0.9°. Reliability analysis between the preoperative CT/MRI and the intraoperative measurements gave kappa values of 0.72 for aTEA-PCA and 0.66 for pAPA-PCA with CT, and 0.82 for aTEA-PCA and 0.84 for pAPA-PCA with MRI.ConclusionsPreoperative rotational assessment of the distal femur with CT may cause higher external rotation of femoral component in TKA.     

Impingement of the patellar component against the tibial post depends on the design of the post-cam mechanism: Comparison between 12 posterior stabilized total knee prostheses

Background

Patella–post impingement (PPI), contact of the patellar component with the tibial post, occurs during deep knee flexion after posterior stabilized total knee arthroplasty (TKA). In a previous pilot study, only two product lines were investigated. The aim of this study was to compare PPI between 12 contemporary posterior stabilized knee prostheses.

Unicompartmental knee arthroplasty for spontaneous osteonecrosis of the medial tibial plateau

Background

There have been very few reports on isolated medial tibial plateau osteonecrosis, and the condition has not been clearly described. Unicompartmental knee arthroplasty (UKA) may be an appropriate treatment method for this condition. The aims of this study were to report our experience of using mobile-bearing knee implants for osteonecrosis of the medial tibial plateau and to discuss the etiology and treatment of this type of osteonecrosis.

三维模型中踝关节中心定位的研究

目的　应用不同方法在三维重建模型上定位踝关节中心,并判断各方法的可行性,准确定位踝关节中心,进而为三维模拟下肢膝关节置换术提供形态学基础。 方法　对33例正常成人踝关节行CT扫描,数据导入三维重建软件Mimics,重建出踝关节三维立体模型,在逆向工程软件Geomagic Studio中分别采用距骨顶部中点（A点）、距骨顶部点云质心（B点）和内外踝间距中点（C点）3种方法对踝关节中心进行定位,并在冠状面上对三中心点之间的距离进行测量,应用统计软件SPSS对数据进行分析。 结果　成功建立了踝关节的三维立体模型,并用不同方法定位出踝关节中心。测量结果显示A点与B点之间的距离为(1.058±0.741)mm, B点与C点之间的距离为(1.684±1.283)mm, A点与C点之间的距离为(1.484±1.040)mm。且每个中心点之间的距离差异不具有显著性(P>0.05)。 结论　基于三维重建模型上的踝关节中心定位方法具有可行性,且与二维平面上的定位相比稳定性更高,其中距骨顶部点云质心作为踝关节中心较其他两种方法更简便易行。     

膝关节软骨负荷运动前后磁共振T_2时间与容积变化研究

目的通过比较分析负荷运动前后膝关节软骨磁共振T2时间和软骨容积变化,探讨利用T2时间和容积变化反映负荷作用下软骨形态变化的可行性。方法选择20例健康志愿者,其中男性16例,女性4例;年龄为20.1~30.4岁,平均年龄25.7岁。在同等运动负荷前后进行软骨T2mapping序列成像,测量股骨内外侧髁、胫骨平台和髌软骨T2时间;以三维脂肪抑制快速扰相梯度回波(3D-FS-SPGR)序列扫描并采用最大信号强度投影法(MIP)重建后测量髌软骨及股骨髁软骨容积。比较负荷前后软骨T2时间变化、软骨容积差异,并分析软骨容积与T2时间变化间的相关性。结果运动前与运动后髌软骨T2时间最长,胫骨外侧平台最短;运动后不同部位软骨T2时间均降低(P=0.000),股骨内侧髁软骨下降幅度最大(t=-27.96,P=0.000);运动后膝关节软骨容积减小(P=0.000),股骨髁软骨容积变化程度(t=-86.71,P=0.000)大于髌软骨(t=-9.42,P=0.000);软骨容积与T2时间变化间无线性相关性(P0.05)。结论运动后膝关节软骨各部位T2时间和局部软骨容积均减少,但软骨容积与T2时间变化间无相关性;软骨T2mapping和软骨容积变化磁共振成像技术对评价负荷作用下软骨形态变化有一定的意义。     

Cost-effectiveness of magnetic resonance imaging of the knee for patients presenting in primary care

Background

Musculoskeletal problems generate high costs. Of these disorders, patients with knee problems are commonly seen by GPs. Magnetic resonance imaging (MRI) of the knee is an accurate diagnostic test, but there is uncertainty as to whether GP access to MRI for these patients is a cost-effective policy.

Aim

To investigate the cost-effectiveness of GP referral to early MRI and a provisional orthopaedic appointment, compared with referral to an orthopaedic specialist without prior MRI for patients with continuing knee problems.

Design of study

Cost-effectiveness analysis alongside a pragmatic randomised trial.

Setting

Five-hundred and thirty-three patients consulting their GP about a knee problem were recruited from 163 general practices at 11 sites across the UK.

Method

Two-year costs were estimated from the NHS perspective. Health outcomes were expressed in terms of quality-adjusted life years (QALYs), based on patient responses to the EQ–5D questionnaire administered at baseline, and at 6, 12, and 24 months’ follow-up.

Results

Early MRI is associated with a higher NHS cost, by £294 ($581; €435) per patient (95% confidence interval [CI] = £31 to £573), and a larger number of QALYs, by 0.050 (95% CI = −0.025 to 0.118). Mean differences in cost and QALYs generated an incremental cost per QALY gained of £5840 ($11 538; €8642). At a cost per QALY threshold of £20 000, there is a 0.81 probability that early MRI is a cost-effective use of NHS resources.

Conclusion

GP access to MRI for patients presenting in primary care with a continuing knee problem represents a cost-effective use of health service resources.     

Accuracy of 2D CT-Based Measurements of Rotational Alignment of the Femoral Component for Total Knee Arthroplasty

PurposeWe aimed to investigate the accuracy of two-dimensional computed tomography (2D-CT)-based methods for measuring rotational alignment of the femoral component during total knee arthroplasty in comparison to reference values for three-dimensional (3D) reconstruction.Materials and MethodsWe selected the “most protruding transepicondylar axis section,” “most protruding posterior condylar line section,” and “distal femoral cut section” on 2D-CT images for 100 knees. We investigated posterior condylar angle (PCA) and condylar twist angle (CTA) values using three different methods on 2D-CT and compared to these values to those obtained using a 3D model.ResultsThe mean PCA and CTA values were 2.8° and 7.0° on the 3D model and 2.0° to 2.1° and 5.9° to 6.0° on 2D-CT, respectively. Errors in PCA and CTA measurement included internal rotation of 0.8° and 1.1° with the 1-plane and 2-plane methods and 0.9° and 1.0° with the assumed resection method, respectively.ConclusionMean errors in PCA and CTA values measured using three different methods on 2D-CT were not significantly different. However, PCA and CTA values measured on 2D-CT were approximately 1° smaller than their 3D values. Thus, we suggest that adding 1° to the mean PCA and CTA values obtained from a single plane of 2D-CT would provide values similar to those obtained from 3D reconstruction.     

3D打印辅助微创治疗AO/OTA-43C型胫骨远端骨折早期疗效观察

目的 探讨3D打印模型辅助微创手术治疗AO/OTA-43C型胫骨远端骨折的早期疗效.方法 回顾性分析2014年1月至2018年6月本科收治的AO/OTA-43C型胫骨远端骨折56例,术前3D打印模型辅助微创经皮钢板技术(3D打印微创手术组)24例,其中男14例,女10例;左侧8例,右侧16例;年龄为45～68岁,平均(...     

基于独立成分分析的青年吸烟者大脑静息态执行网络功能连接变化研究

采用独立成分分析方法探索40名青年吸烟者和40名年龄与性别相匹配的非吸烟者的静息态功能磁共振数据,并结合“双重回归”方法探索吸烟者执行网络功能连接变化,同时将有变化的脑区与吸烟统计学数据进行Pearson’s双变量相关分析,例如年龄、包年、FTND、烟龄等。通过研究发现,青年吸烟者的大脑右中央执行网络的功能连接性增强,相关分析表明执行网络包含的背外侧前额叶皮质与烟龄呈显著性负相关（r=-0.339, P=0.032）。此项研究结果表明,吸烟对右侧中央执行网络的功能连接有一定的影响,研究结果可能为青年吸烟成瘾者的神经机制的特征提供额外的新见解。