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.     

Morphology of the transepicondylar axis and its application in primary and revision total knee arthroplasty

A morphologic anatomic study was done of the lower extremity to investigate various relationships of the transepicondylar axis (TEA). Thirteen cadaver specimens were dissected and mounted to a metal frame with a pin passing through the TEA. The center of the knee was determined as the depth of the anterior intercondylar groove. The ratio of the upper leg to lower leg measured from femoral head center and ankle center to TEA was 1.02. The mean distance of the TEA to the joint line was 3.08 cm medial and 2.53 cm lateral. The mean femoral angle comparing the TEA to mechanical axis was 0.61° varus. The mean tibial angle comparing the TEA to the mechanical axis was 0.4° varus in extension and 0.43° in flexion, with no significant difference in the lower extremity angle with flexion (P < .01). The TEA is an important landmark that, from this study, is virtually perpendicular to the mechanical axis of the lower extremity and parallels the knee flexion axis. Femoral component rotation and joint line positioning in total knee arthroplasty can be determined using the TEA.     

Comprehensive treatment of late-onset tibia vara

BACKGROUND: Late-onset tibia vara (Blount disease) can be difficult to treat because of frequent morbid obesity and associated deformities, including distal femoral varus, proximal tibial procurvatum, and distal tibial valgus, that contribute to lower extremity malalignment. We present a comprehensive approach that addresses all components of the deformity and allows restoration of the anatomic and mechanical axes. METHODS: Fifteen consecutive patients (nineteen lower extremities) with late-onset tibia vara were managed with this comprehensive approach. The mean age of the patients at the time of surgery was 14.9 years, and the mean weight was 113 kg. Standing anteroposterior and lateral radiographs were made preoperatively and at the time of the final follow-up. Preoperatively, the mean mechanical axis deviation was 108 mm, the mean lateral distal femoral angle was 95 degrees , and the mean mechanical medial proximal tibial angle was 71 degrees . In all nineteen extremities, the proximal tibial varus deformity was corrected by means of a valgus osteotomy and application of an Ilizarov ring external fixator. Distal femoral varus was corrected by means of either hemiepiphyseal stapling or valgus osteotomy with blade-plate fixation in thirteen of the nineteen extremities. Distal tibial valgus was treated either with hemiepiphyseal stapling or with varus osteotomy and gradual correction with use of the Ilizarov external fixator in eleven of the nineteen extremities. RESULTS: After a mean duration of follow-up of 5.0 years, the mean mechanical axis deviation had improved to 1 mm (range, 20 to -30 mm), the lateral distal femoral angle had improved to 87 degrees (range, 83 degrees to 98 degrees), and the mechanical medial proximal tibial angle had improved to 88 degrees (range, 83 degrees to 98 degrees ). The mean time required for correction of the proximal tibial varus deformity was thirty-one days, and the external fixator was removed at a mean of 4.5 months postoperatively. All patients had development of one or more superficial pin-track infections (mean, 1.9 pin-site infections per patient). No wound infections, nonunions, or neurovascular complications occurred. Eighteen of the nineteen extremities were pain-free at the time of the final follow-up. CONCLUSIONS: This comprehensive approach allowed restoration of the mechanical and anatomic axes of the lower extremity in patients with late-onset tibia vara, resulting in a resolution of symptoms as a result of normalization of the weight-bearing forces across the knee and ankle. We believe that this approach will decrease the risk of early degenerative arthritis of the knee.     

Radiographic analysis of the axial alignment of the lower extremity

The axial alignment of the lower extremities of twenty-five normal male volunteers whose mean age was thirty years was studied using a standardized radiograph of the entire lower extremity. The extremities were found to be in a mean of 1.5 degrees (right) and 1.1 degrees (left) of varus angulation at the knee between the tibial and femoral mechanical axes. The transverse axis of the knee lacked a mean of 3.0 degrees (right) and 2.6 degrees (left) of being perpendicular to the mechanical axis of the tibia. The anatomical axis of the femur did not pass through the center of the knee.     

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.     

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.     

Sagittal alignment of the lower extremity while standing in Japanese male

There is little information available regarding the sagittal mechanical axis of the lower extremity of normal subjects under weight-bearing conditions. The purpose of this study was to determine the sagittal alignment of the lower extremity under such conditions. Anteroposterior and lateral radiographs were taken of the 20 lower extremities of 10 healthy male Japanese volunteers (mean age, 27 years) while standing. The coronal mechanical axis passed through 33.9% medial to the proximal tibial articulating surface. The sagittal mechanical axis passed through 38.0% anterior to the distal femoral condyle and 27.9% anterior to the proximal tibial articulating surface, and also passed 5.2 mm anterior to the intercondylar notch. Our study therefore showed that the coronal and sagittal mechanical axes of the lower extremity do not always pass through the center of the knee. This has important implications for alignment in surgery of lower extremities such as total knee arthroplasty and osteotomy. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.     

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.     

Axial alignment of the lower extremity in Chinese adults

BACKGROUND: The restoration of normal axial alignment of the lower extremity is important to surgeons who perform reconstructive surgery of the knee. However, data on the normal alignment of the lower extremity in Chinese adults are not available. METHODS: The axial alignment of the lower extremity in twenty-five adult male and twenty-five adult female volunteers of southern Chinese origin was measured on weight-bearing radiographs of the entire lower limb. The mean age was twenty-four years for the male volunteers and twenty-three years for the female volunteers. The results were compared with those of two similar studies of white volunteers in the United States. RESULTS: The medial inclination of the tibial plateau in the Chinese subjects (mean and standard deviation, 5.4 +/- 2.5 degrees for women and 4.9 +/- 2.3 degrees for men) was greater than the commonly reported 3 degrees. The extremities of the Chinese women were found to have a mean of 2.2 +/- 2.5 degrees of varus alignment, and those of the Chinese men had a mean of 2.2 +/- 2.7 degrees of varus alignment. CONCLUSIONS: Compared with the white subjects described in the studies by Moreland et al. and Hsu et al., the Chinese subjects had significantly larger medial inclination of the knee joint (knee-joint obliquity) (p < 0.005) and the female Chinese subjects had significantly more varus alignment of the lower extremity (p < 0.025). CLINICAL RELEVANCE: Five degrees of external rotation of the femoral component, instead of the commonly reported 3 degrees, may be required to obtain a rectangular flexion gap in total knee arthroplasty in Chinese patients. The racial difference in the knee-joint obliquity may contribute to the racial difference in the ratio of knee osteoarthritis to hip osteoarthritis. Additional studies are necessary to confirm this relationship.     

Integrating various common indexes of bony alignment in femoral supracondyle

Objective

Indexes, which can optimally represent the bony alignment around the knee, are still controversial. Three common indexes, mechanical axis (MA), anatomic axis (AA), and anatomic lateral distal femoral angle (aLDFA), were integrated to simplify patient follow-up in the femoral supracondylar region.

Materials and methods

Eighty consecutive adult patients (40 men, 40 women; age range 19–40 years) were studied using a full-length standing scanogram. Thirteen indexes, including MA, AA, and aLDFA, were measured and integrated. The relationships among these indexes were analyzed.

Results

The MA of the lower extremity passed with an average of 6.6 mm (9.2 % of the tibial articular surface width) medial to the knee center. The supracondylar axis (SA) was an average of 2.0° more valgus than the AA in the femoral supracondyle. An average 1.1° deviation was noted in the AA, as measured by the femoral shaft axis or a line connecting the piriformis fossa to the knee center.

Conclusion

The femoral MA may be more favorable than the MA of the lower extremity in order to represent an ideal weight-bearing line. The AA and aLDFA may be measurable via the SA in the anteroposterior view of the plain knee radiograph. Thus, patient follow-up becomes much more convenient.     

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.     

Factors Correlated with the Reducibility of Varus Deformity in Knee Osteoarthritis: An Analysis Using Navigation Guided TKA

Background

We hypothesized that a number of clinical and radiologic parameters could influence the reducibility of varus deformity in total knee arthroplasty. The aim of this study was to identify the factors correlated with reducibility of varus deformity and predict more accurately the amount of medial soft tissue release required in varus deformity total knee arthroplasty.

Methods

One hundred forty-three knees with preoperative varus alignment and medial osteoarthritis were included in this retrospective study. The total knee arthroplasties were performed using a navigation system (OrthoPilot) by single surgeon. To assess varus deformity, the authors measured preoperative mechanical axis angles and valgus stress angles. Mechanical tibial angles, mechanical femoral angles, femoral osteophyte sizes, and tibial osteophyte sizes were measured. The Ahlbäck grading scale was applied for radiologic parameters, and clinical parameters (age, body mass index, sex, duration of pain, and preoperative range of motion) were documented. Correlations between these factors and preoperative valgus stress angle were analyzed.

Results

A negative correlation was found between preoperative mechanical axis angle and preoperative valgus stress angle (p < 0.01, r = -0.38), and a positive correlation was found between the preoperative mechanical tibial angle and preoperative valgus stress angle (p = 0.01, r = 0.19).

Conclusions

The present study shows that preoperative varus deformity and proximal tibial vara (measured by preoperative mechanical axis angle and mechanical tibial angle, respectively) are correlated with reducibility of varus deformity (measured by preoperative valgus stress angle), and clinical parameters (age, range of motion, duration of pain and body mass index) and other radiologic parameters (osteophyte size, severity of osteoarthritis and angulation of distal femoral joint surface) were not significantly correlated with reducibility of varus deformity.     

膝骨性关节炎下肢负重位等比例全长X线片测量与分析

目的 :对膝骨性关节炎患者的下肢负重位等比例全长X线片进行测量与分析,明确该组人群下肢解剖和力学轴线的特征性变化。方法:收集自2015年6月至2016年5月膝骨性关节炎患者下肢负重位等比例全长X线片数据和具有血管病变而无膝关节病史患者下肢CTA扫描数据。将具有血管病变而无膝关节病史患者作为正常人组,共20例40膝,男7例,女13例,年龄24~72岁,平均63.2岁;将膝骨性关节炎患者作为关节炎组,并将关节炎组分为内翻膝组和外翻膝组,共53例100膝,男10例,女43例,年龄52~80岁,平均64.7岁。测量股骨角(F角)、胫骨角(T角)、关节间隙角(JS角)、股胫角(FT角)、髋-膝-踝角(HKA角)、膝生理外翻角(KPV角)及股骨头颈偏距(offset)。对测量数据进行统计分析。结果 :正常人组F角(79.9±2.3)°,T角(93.8±3.7)°,JS角(1.7±1.0)°,FT角(175.4±4.0)°,HKA角(181.4±4.1)°,KPV角(6.0±1.0)°,offset(38.5±6.5)mm;骨关节炎组F角(81.4±3.5)°,T角(94.6±2.7)°,JS角(2.1±2.5)°,FT角(178.1±6.3)°,HKA角(184.3±6.9)°,KPV角(6.2±1.5)°,offset(38.1±9.2)mm。KPV角在内翻膝(6.5±1.4)°和外翻膝(5.5±1.5)°之间差异有统计学意义(t=2.956,P=0.005);KPV角与患者年龄之间有相关性(r=0.241,P=0.016);股骨偏心距与KPV角之间有相关性(r=0.946,P=0.000)。结论 :膝骨性关节炎平均膝关节生理外翻角为6.2°,并且与年龄、股骨偏心距呈正相关。内翻膝的平均膝关节生理外翻角大于外翻膝约1°。膝骨性关节炎下肢力学参数的改变可能与膝骨性关节炎的发生和发展有关。在TKA术前对下肢全长等比例X线片进行测量评估,取得下肢力学数据作为参考,可使得术中截骨变得更加合理、个体化。     

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.     

Changes in Hip,Knee, and Ankle Coronal Alignments After Total Hip Arthroplasty With Transverse Femoral Shortening Osteotomy for Unilateral Crowe Type IV Developmental Dysplasia of the Hip

Background

To investigate changes in lower extremity coronal alignment in patients with unilateral Crowe type IV developmental dysplasia of the hip who underwent total hip arthroplasty with transverse femoral shortening osteotomy.

Anatomical analysis of the femoral condyle in normal and osteoarthritic knees.

It is important to understand anatomical feature of the distal femoral condyle for treatment of osteoarthritic knees. Detailed measurement of the femoral condyle geometry, however, has not been available in osteoarthritic knees including valgus deformity. This study evaluated femoral condyle geometry in 30 normal knees, 30 osteoarthritic knees with varus deformity, and 30 osteoarthritic knees with valgus deformity using radiographs and magnetic resonance imaging (MRI). In radiographic analysis in the coronal plane, the femoral joint angle (lateral angle between the femoral anatomic axis and a tangent to femoral condyles) was 83.3 degrees in the normal knees, 83.8 degrees in the varus knees, and 80.7 degrees in the valgus knees. In MRI analysis in the axial plane, the posterior condylar tangent showed 6.4 degrees of internal rotation relative to the transepicondylar axis in the normal knees, 6.1 degrees in the varus knees, and 11.5 degrees in the valgus knees. These results suggested that there was no hypoplasia of the medial condyle in the varus knees, but the lateral condyle in the valgus knees was severely distorted. Surgeons should take this deformity of the lateral femoral condyle into account when total knee arthroplasty is performed for a valgus knee.     

Femoral shaft bowing influences the correction angle for high tibial osteotomy

Background The optimal femorotibial angle (FTA) after high tibial osteotomy (HTO) is still controversial. Our hypothesis was that FTA itself may not be reliable because FTA cannot represent the accurate alignment of the whole lower extremity. Methods Non-weight-bearing radiographs of the lower extremities were taken in 100 Japanese subjects with medial osteoarthritic knees, and seven anatomic parameters were assessed. The correction angle by FTA was calculated so that the postoperative FTA was set at 166° (14° valgus). Another correction angle was calculated so that the mechanical axis passed through the lateral one-fourth of the tibial articular surface after HTO. After the correlation between two correction angles was assessed, influences of anatomic parameters on the discrepancy between two correction angles were assessed. Results There was a high correlation between two correction angles (R ² = 0.777, P < 0.001). The mechanical axis passed through the lateral one-fourth of the tibial articular surface when the postoperative FTA was set at 166° in 80% of subjects. However, discrepancy between the two correction angles was 3° or larger in 20% of subjects. Femoral shaft bowing and tibial shaft bowing significantly influenced the correction angles. Even though FTA was the same, the femoral head shifted medially in cases with lateral bowing of the femoral shaft, and the correction angle by FTA should be set larger. On the other hand, the correction angle by FTA can be set smaller in knees with medial bowing of the femoral shaft. Tibial shaft bowing also influences the correction angle by FTA. Conclusions The correction angle by FTA for HTO should be calculated taking femoral and/or tibial shaft bowing in the frontal plane into account.     

Does proximal femoral?varus osteotomy in Legg–Calvé–Perthes disease predispose to angular mal-alignment of the knee? A clinical and radiographic study at skeletal maturity

Background

Though there is an impression that proximal femoral varus osteotomy (FVO) can result in a valgus deformity at the knee there is no agreement on this issue. This study was undertaken to ascertain whether a FVO predisposes to the development of genu valgum in children with Legg–Calvé–Perthes disease (LCPD).

Methods

One hundred and one children with unilateral LCPD who underwent a FVO during the active stage of the disease and 32 children who were treated non-operatively were followed till skeletal maturity. The FVO was performed with a 20° varus angulation in all the patients and weight-bearing was not permitted till the stage of reconstitution. The alignment of the knee was assessed clinically at skeletal maturity. A subset of 33 operated children also had full length standing radiographs of the limbs. The mechanical axis deviation, femur-tibial angle, lateral distal femoral angle and the medial proximal tibial angle of both limbs were measured on these radiographs.

Results

The frequency of clinically appreciable mal-alignment of the knee was not greater on the affected side in patients who had undergone FVO when compared to the unaffected limb and also when compared to the affected limb in non-operated patients. The mechanical axis of the lower limb of operated children was relatively in more valgus than that of normal limbs but they fell within the normal range.

Conclusion

This study does not support the impression that a proximal femoral osteotomy for LCPD predisposes to clinically discernable degrees of genu valgum in children who have had 20° of varus angulation at the osteotomy site and who have avoided weight-bearing for a prolonged period following surgery. Further studies are needed to clarify if genu valgum would develop if early post-operative weight-bearing is permitted.

Level of evidence

III.     

Knee alignment in professional tennis players

This study determined lower-limb alignment and knee geometry in professional tennis players and compared the data with those from nonathletic individuals. Twenty-four radiographs from 12 asymptomatic players (mean age: 23.4+/-3.8 years) were prospectively studied. The three angles most useful for describing limb alignment and knee geometry in the coronal plane were measured: hip-knee-ankle, condylar-hip, and plateau-ankle. The condylar-plateau angle, frontal foot rotation angle, and the relationship between the mechanical axis and tibial plateau also were calculated. Varus limb alignment was predominant and the mechanical axis passed medially through the knee center; there was increased valgus inclination of the distal femur, varus angulation of the tibial plateau, near parallel alignment of the joint, and exaggerated external foot rotation. Hip-knee-ankle, condylar-hip, plateau-ankle, and frontal foot rotation angles were significantly different (P<.05, two-tailed t test) from previously reported angles of nonathletic individuals. Variations, probably due to repetitive dynamic demands imposed on lower limbs from an early age, seem to involve both femoral condyles and proximal tibial metaphyses, maintaining normal parallel joint alignment.