Foot rotational effects on radiographic measures of lower limb alignment.

INTRODUCTION: Surgical planning of high tibial osteotomy (HTO) typically requires the measurement of lower limb alignment from standing anteroposterior radiographs. Although every effort is made to maintain a standardized patient position, factors such as pain or anatomic constraints may necessitate acquiring the radiograph in a less than optimal patient position. One such constraint is natural rotation of the feet with respect to the tibia. The purpose of the present study was to investigate the magnitude of the effect of foot rotation on radiographic measures of lower limb alignment. METHODS: We analyzed 19 lower limbs from radiographs obtained from 10 people who reported to an orthopedic injuries clinic. Each patient was radiographed in 3 positions: 15 degrees of internal foot rotation, no foot rotation and 15 degrees of external foot rotation. We measured and compared the mechanical axis angle (hip-knee-ankle) and the mechanical axis deviation from each position. RESULTS: Compared with the position with no foot rotation, internal foot rotation resulted in less measured varus alignment and less mechanical axis deviation from the knee joint centre, whereas external foot rotation produced greater measured varus alignment and increased mechanical axis deviation from the knee joint centre. CONCLUSIONS: These results indicate that patient positioning is an important factor when measuring lower limb alignment from radiographs. As a result, special care must be taken when acquiring these radiographs for use in planning surgical procedures such as HTO.     

Normal axial alignment of the lower extremity and load-bearing distribution at the knee

Based on a series of 120 normal subjects of different gender and age, the geometry of the knee joint was analyzed using a full-length weight-bearing roentgenogram of the lower extremity. A special computer program based on the theory of a rigid body spring model was applied to calculate the important anatomic and biomechanical factors of the knee joint. The tibiofemoral mechanical angle was 1.2 degrees varus. Hence, it is difficult to rationalize the 3 degree varus placement of the tibial component in total knee arthroplasty suggested by some authors. The distal femoral anatomic valgus (measured from the lower one-half of the femur) was 4.2 degrees in reference to its mechanical axis. This angle became 4.9 degrees when the full-length femoral anatomic axis was used. When simulating a one-legged weight-bearing stance by shifting the upper-body gravity closer to the knee joint, 75% of the knee joint load passed through the medial tibial plateau. The knee joint-line obliquity was more varus in male subjects. The female subjects had a higher peak joint pressure and a greater patello-tibial Q angle. Age had little effect on the factors relating to axial alignment of the lower extremity and load transmission through the knee joint.     

Lower limb alignment in healthy Japanese adults

BackgroundKnowledge regarding the normal alignment of the lower limb is important when considering alignment for total knee arthroplasty. However, few studies have explored the lower limb alignment of healthy Japanese subjects.MethodsBetween July and October 2020, we performed whole leg standing radiography of 120 legs of 60 healthy adult Japanese volunteers aged <50 years in the closed-leg stance. The measurement parameters were hip knee ankle angle (positive for varus), percentage of constitutional varus (hip knee ankle angle ≥ 3°), mechanical axis deviation ratio, mechanical lateral distal femoral angle, medial proximal tibial angle, joint line convergence angle (positive for lateral opening), and tibial joint line angle (positive for medial inclination).ResultsThe mean measured values for all volunteers, men and women, were as follows: hip knee ankle angle (°), 2.3, 2.6, and 2.0; mechanical axis deviation ratio, 35.8, 35.6, and 36.9; mechanical lateral distal femoral angle (°), 86.7, 87.0, and 86.7; medial proximal tibial angle (°), 85.6, 85.0, and 86.2; joint line convergence angle (°), 0.6, 0.3, and 0.8; and tibial joint line angle (°), ?1.0, ?0.7, ?1.4, respectively. The percentage of constitutional varus was 35.8% overall, 35.8% in men and 35.3% in women. Only the medial proximal tibial angle was smaller in men than that in women (p = 0.003).ConclusionsThe mechanical lateral distal femoral and medial proximal tibial angles were smaller, hip knee ankle angle was larger, and percentage of constitutional varus was higher in Japanese subjects than those reported for subjects in other countries. Our findings improve the understanding of Japanese-specific alignments when considering alignment for lower limb surgery, especially, total knee arthroplasty.     

Varus tibial joint line obliquity: a potential cause of femoral component malrotation.

In 60 consecutive total knee arthroplasties done in 52 patients with primary osteoarthritis and varus or neutral tibiofemoral alignment, the posterior condylar angle was calculated intraoperatively and averaged 3.98 degrees (range, 0 degrees-9 degrees). Eighteen knees had a posterior condylar angle value less than 3 degrees whereas 27 knees had a posterior condylar angle value of 5 degrees or greater. Final rotational alignment of the femoral component was set parallel to the transepicondylar axis. Only one of these 60 knees required a lateral retinacular release for proper patellar tracking during the knee arthroplasty. When compared with three previously defined angles measured on the radiographs taken preoperatively, only the tibial plateau-tibial shaft angle values were correlated significantly with the value of the posterior condylar angle. As the tibial varus joint line obliquity increased, there was a distinct tendency for the transepicondylar axis to be rotated more externally relative to the posterior condylar axis. This variance suggests that the use of the posterior condylar axis as a rotational reference is inappropriate in many knees with arthritis with varus or neutral tibiofemoral alignment. In particular, varus tibial joint line obliquity of more than 4 degrees increases the likelihood of femoral component malrotation when the posterior femoral condyles are used to reference femoral component rotation.     

Computer-Assisted Total Knee Arthroplasty for Significant Tibial Deformities

Computer-assisted total knee arthroplasty has been demonstrated to provide reproducible limb mechanical alignment within 3° from the neutral mechanical axis. However, restoring proper implant and extremity alignment remains a significant challenge with proximal tibial deficiencies. In this prospective study, we describe the use of computer navigation to quantify the amount of bone loss on the medial or lateral tibial plateau and the use of these data to assess the need for augmentation with metallic tibial wedges. In this study, we demonstrate that computer-assisted total knee arthroplasty in patients with significant tibial deformities can accurately measure severe tibial deformities, predict tibial augment thickness, and provide excellent mechanical alignment and restore the joint line without excessive bony resection, repeated osteotomies, and repeated augment trialing.     

Effect of the foot on the mechanical alignment of the lower limbs

The authors evaluated the effect of the foot on the loading axis of the lower limb measured from radiographs in 30 pediatric patients. Deviation at the knee was calculated for the hip-ankle (traditional) and the hip-foot lines (heel lined up with a metal wire). A trigonometric model of the limb loading axis was developed with predicted mechanical axis deviations at the knee. Statistics were based on the methods of Bland and Altman. Mechanical axis deviation at the knee in the frontal plane varies with foot height, foot-tibial angle, and genu valgum. The predicted trigonometric model was found to be in agreement with measured radiographic values. Including the foot in the radiographic measurement of limb alignment may increase validity of surgical planning for correction of malalignment and for evaluation of degenerative arthritis risk at the knee level.     

The importance of tibial alignment: finite element analysis of tibial malalignment

The influence of the tibial plateau orientation on cancellous bone stress was examined by finite element analysis for a cemented device. The objectives of the study were i) to examine the effect of the plateau-ankle angle on the cancellous bone stress, ii) to analyze the significance of the anteroposterior angles of the tibial component on these stresses, and iii) to compare the finite element predictions with clinical data. In general, positioning the tibial plateau in valgus resulted in lower cancellous bone stresses. These results support previous clinical studies, which suggest that overall alignment in valgus results in lower migration rates and lower incidence of loosening.     

The importance of tibial alignment

The influence of the tibial plateau orientation on cancellous bone stress was examined by finite element analysis for a cemented device. The objectives of the study were i) to examine the effect of the plateau-ankle angle on the cancellous bone stress, ii) to analyze the significance of the anteroposterior angles of the tibial component on these stresses, and iii) to compare the finite element predictions with clinical data. In general, positioning the tibial plateau in valgus resulted in lower cancellous bone stresses. These results support previous clinical studies, which suggest that overall alignment in valgus results in lower migration rates and lower incidence of loosening.     

Does axial limb rotation affect the alignment measurements in deformed limbs?

The long-term outcome of total knee arthroplasty and femoral or tibial osteotomy is related to the ability of the surgeon to achieve the desired alignment based on preoperative planning. This study evaluates the effect of axial rotation on measured tibiofemoral angles and the angle formed between the anatomic and mechanical axes of the femur in lower extremities with valgus and varus deformities. A comparison study of the measured tibiofemoral angles indicated a statistically significant effect in models with severe vagus or varus deformity when rotated 10 degrees internally or externally. In the second part of the study, the measured angle between the anatomic and mechanical axes of the femur never varied by more than 1 degree, despite a 40 degrees are of rotation. The results of the study indicate the tibiofemoral angle measurements are more sensitive to axial limb rotation in lower extremities with valgus or varus deformity than are normally aligned limbs. In preoperative planning of total knee arthroplasty, the measured angle between the anatomic and mechanical axes of the femur is less effected by limb rotation, regardless of the degree of valgus or varus deformity.     

股骨远端旋转对线参考轴线与胫骨机械轴关系的研究

目的 研究股骨远端旋转对线参考轴线与胫骨机械轴的关系,确定最为可靠参考轴线,并探讨其优越性.方法 对30例下肢尸体标本分别在膝关节伸直位、屈膝90°进行数码照相,照片经计算机处理后,分别测量股骨机械轴、临床髁上轴的垂线、外髁髁上轴的垂线、Whiteside线与胫骨机械轴的夹角,并将其相比较进行统计学分析.结果 临床髁上轴的垂线、外髁髁上轴的垂线、Whiteside线、股骨机械轴相对于胫骨机械轴分别为内翻0.6°、内翻3.9°、外翻0.2°、内翻3.0°.临床髁上轴、外髁髁上轴、Whiteside线在伸膝时与屈膝时比较分别为外翻2.3°、内翻0.9°、外翻3.1°.股骨机械轴与胫骨机械轴的夹角大于临床髁上轴垂线、Whiteside线与胫骨机械轴的夹角,其差异具有统计学意义(P0.05).结论 外髁髁上轴是较临床髁上轴、Whiteside线更为可靠的股骨假体旋转对线参考标志,术中参考外髁髁上轴行股骨后髁切骨时可获得相对良好的胫股关节、髌股关节运动轨迹.     

Reliability of the hip-to-ankle radiograph in determining the knee and implant alignment after total knee arthroplasty

Hip-to-ankle radiographs have been used to evaluate lower limb alignment before and after total knee arthroplasty. However, earlier studies have inappropriately used correlation to assess the reproducibility of the radiographs. We determined the reliability of the hip-to-ankle radiograph using the Bland-Altman analysis. Two consecutive hip-to-ankle radiographs were obtained in 52 patients (52 knees) after total knee arthroplasty. There was an excellent agreement between mechanical axis angles, tibiofemoral angles, and femoral and tibial component alignment in the two radiographs. There was also an excellent agreement between all intra and interobserver analyses. The hip-to-ankle radiograph appears to be a reliable and reproducible means for determining the alignment of the knee in the coronal plane after total knee arthroplasty. In routine follow-up, the short anteroposterior knee radiograph may provide sufficient information. However, only the hip-to-ankle radiograph provides accurate information on the weightbearing mechanical axis in patients with suspected lower limb malalignment.     

Optimization of the fixed-flexion knee radiograph

PURPOSE: To develop a user-friendly method of achieving optimal radiographs for measurement of joint space width of the knee with minimal radiation exposure. In order to accomplish this the X-ray technologist must (1) be able to identify the anterior and posterior rims of the tibial plateau at a variety of X-ray head angles and (2) be able to choose the direction to adjust the head angle to get a better view based on the criteria for acceptable radiographs. METHODS: We have developed a training manual and materials to instruct investigators and radiology technologists in a method that uses a commercially available Plexiglas positioning frame (Synaflexer) and standard X-ray equipment to achieve optimal X-rays with regard to tibial plateau alignment of the knee. This should be accomplished with four or fewer radiographs. RESULTS: Optimized radiographs for joint space width measurements are achieved without the need for fluoroscopy or foot maps. CONCLUSIONS: This method is readily understood and instituted by radiology technologists in the field.     

Triple plating of tibia in a complex bicondylar tibial plateau fracture

High-energy tibial plateau fracture poses a significant challenge and difficulty for orthopaedic surgeons. Fracture of tibial plateau involves major weight bearing joint and may alter knee kinematics. Anatomic reconstruction of the proximal tibial articular surfaces, restoration of the limb axis （limb alignment） and stable fixation permitting early joint motion are the goals of the treatment. In cases of complex bicondylar tibial plateau fractures, isolated lateral plating is frequently associated with varus malalignment and better results have been obtained with bilateral plating through dual incisions. However sometimes a complex type of bicondylar tibialplateau fractures is encountered in which medial plateau has a biplaner fracture in posterior coronal plane as well as sagittal plane. In such fractures it is imperative to fix the medial plateau with buttressing in both planes. One such fracture pattern of the proximal tibia managed by triple plating through dual posteromedial and anterolateral incisions is discussed in this case report with emphasis on mechanisms of this type of injury, surgical approach and management.     

The effects of femoral shaft malrotation on lower extremity anatomy

OBJECTIVE: To determine how axial rotation around the anatomic axis of the femur, as would occur with malrotation of a femoral fracture, affects frontal and sagittal plane alignment and knee joint orientation. DESIGN: Computer-generated models of the lower extremity were constructed using standardized dimensions. To simulate a malrotated fracture, these models were rotated in the shaft around the anatomic axis in 15 degrees increments from 60 degrees internal to 60 degrees external rotation. Rotation was performed at the proximal fourth, mid-shaft, and distal fourth. MAIN OUTCOME MEASUREMENTS: At each rotational position, the mechanical axis deviation in millimeters and the changes in mechanical lateral distal femoral angle in degrees were measured to quantify frontal plane malalignment and malorientation, respectively. The mechanical axis deviation in millimeters in the sagittal plane was also measured at each rotatory position. RESULTS: Femoral shaft malrotation greater than 30 degrees internal rotation of a subtrochanteric fracture or more than 45 degrees of a midshaft fracture or external rotation of 30 degrees or greater of a supracondylar fracture resulted in frontal plane malalignment. External rotation of a supracondylar fracture of 45 degrees or more results in knee joint malorientation. Any external rotation at all 3 fracture levels caused posterior displacement of the weight-bearing axis in the sagittal plane. CONCLUSIONS: Malrotation of a femoral shaft fracture is not just a cosmetic problem. Internal and external rotation causes malalignment and malorientation in the frontal plane, depending on the level of the fracture and the magnitude of malrotation. External rotation of any degree at the proximal fourth, mid-shaft, and distal fourth causes a posterior shift of the weight-bearing axis in the sagittal plane.     

Linear mixed modeling on the effects of varus knee surgery on the ankle joint weight-bearing axis

BackgroundVarus knee correction may affect the ankle and subtalar joints and impact the prognosis of ankle arthritis because the weight-bearing load on the lower extremity extends from the hip to the foot. We aimed to evaluate the changes in the mechanical axis and the weight-bearing axis of the ankle after varus knee surgery.MethodsPatients with a varus knee were followed up after undergoing high tibial osteotomy or total knee replacement arthroplasty. The inclusion criteria were age (>18 years) and a history of preoperative and postoperative scanograms. The postoperative change to the ankle joint axis point on the mechanical axis and weight-bearing axis according to the hip–knee–ankle angle correction was adjusted by multiple factors using a linear mixed model.ResultsOverall, 257 limbs from 198 patients were evaluated. The linear mixed model showed that the change in the ankle joint axis point on the mechanical axis was not statistically significant after high tibial osteotomy and total knee replacement arthroplasty (p = 0.223). The ankle joint axis point on the weight-bearing axis moved laterally by 0.9% per degree of postoperative hip–knee–ankle angle decrease (p < 0.001).ConclusionsVarus knee correction could affect the subtalar joint and the ankle joint. Our findings require consideration when utilized during pre- and postoperative evaluations using the weight-bearing axis of patients undergoing varus knee correction.     

三维骨建模系统在人工全膝关节置换时旋转对位的作用

目的 为了进行人工全膝关节置换时假体旋转对位的量化研究,探讨三维骨建模的计算机辅助手术系统对量化操作的精确性和有效性. 方法 2002年11月 - 2003年6月,采用三维骨建模 Ceravision 系统对 21 例 21 膝保守治疗无效的三间隔骨性关节炎患者行人工全膝关节置换术.男5例5膝,女16例16膝;年龄64～79岁,平均 72.4 岁.左膝10例,右膝11例.主要临床表现为膝关节疼痛和活动受限.病程2～10年.14例膝内翻,7例膝外翻.根据相关的临床体检、影像学和导航系统资料,对术中假体旋转对位量值,并对术后3个月膝关节活动度、膝关节松弛度和髌骨稳定性进行分析. 结果 全部患者术后切口均Ⅰ期愈合.21 例患者均获随访12～16个月,平均13.3个月.术中股骨假体旋转对位内旋 1°～外旋 5°,胫骨假体旋转对位内旋 0°～外旋5°.其中膝内翻患者,股骨假体旋转对位外旋 1°～外旋5°,胫骨假体旋转对位外旋2°～外旋5°膝外翻患者,股骨假体旋转对位内旋1°～外旋4°,胫骨假体旋转对位内旋0°～外旋 4°.术后3个月膝关节活动度,最大屈膝度为 105～130°,平均 115°;膝关节额面松弛度,内侧 0.2～0.5 cm,平均 0.27 cm,外侧 1.0～2.5 cm,平均 1.7 cm.无膝痛、髌骨失稳和脱位等并发症发生. 结论 应用三维骨建模的计算机辅助手术系统,可针对患者个体精确地进行假体旋转对位.     

Distal Femoral Rotation Correlates With Proximal Tibial Joint Line Obliquity: A Consideration for Kinematic Total Knee Arthroplasty

Background

We hypothesized that there is a correlation between the distal femoral rotation and proximal tibial joint line obliquity in nonarthritic knees. This has significance for kinematic knee arthroplasty, in which the target knee alignment desired approximates the knee before disease.

Significance of static prosthesis alignment for standing and walking of patients with lower limb amputation

The influence of three alignment parameters of a transtibial prosthesis (sagittal foot position, plantar flexion, mediolateral foot position) on the load and motion of the lower extremity joints was investigated in 13 unilateral transtibial amputees. The aim was to determine whether a correlation exists between static prosthetic alignment and gait pattern that would allow an optimal biomechanical prosthetic alignment. The gait pattern was measured using kinematic, kinetic, and electromyographic methods. Statics was defined using the alignment apparatus L.A.S.A.R. Posture. The electromyogram of the m. vastus lateralis and m. biceps femoris was recorded on both sides. The motion of joints is described by joint angles. External joint moments define the mechanical loads. Alignment has almost no influence on muscle activity and joint mechanics of the contralateral leg. In contrast, prosthetic alignment affects clearly and systematically the load and motion of the knee joint during the stance phase on the ipsilateral side. The sagittal foot position influences the maximal flexion angle in the stance phase. The plantar flexion of the foot affects the temporal structure of knee motion. The mediolateral foot position causes correspondingly different varus and valgus moments acting on the knee. Swing phase motion does not depend on prosthetic alignment. The iEMG of the m. vastus lateralis is reduced. Innervation characteristics of the m. biceps femoris on the prosthetically fitted leg has completely changed. The ischiocrural muscles take over the neuromuscular action of the m. gastrocnemius to compensate for the external knee extension moment during the second part of the stance phase. Prosthetic statics determines if the knee joint is physiologically stressed in a standing posture and during walking. Statics will be correct if the anatomical knee axis of the standing amputee is located about 15 mm posterior to the load line in the sagittal plane. In the frontal plane, the load line touches the lateral patella border and strikes the middle of the foot about 5 cm anterior to the adapter. During walking, attention should be paid to performance of knee flexion in the stance phase.