Changes In Limb Alignment Research Articles

Poster 249: Distal Femoral Coronal Realignment Osteotomies Alter CT-Measured Tibial Tuberosity to Trochlear Groove (TT-TG) Distance in Addition to Mechanical Axis Deviation – A Cadaveric Study

Objectives: Patellar tracking has been shown to be affected by limb alignment. Many patients with underlying valgus deformity with patellar instability have elevated tibial tuberosity–trochlear groove (TT-TG) measurements. Correction of limb alignment improves Q-angle, however, its effect on TT-TG as measured by computed tomography (CT) has yet to be demonstrated. We hypothesize that changing the limb alignment as measured by mechanical axis deviation (MAD) through a distal femoral osteotomy (DFO) would also cause a change in TT-TG distance as measured by CT. Methods: Lateral distal femoral osteotomies were performed on 5 cadaveric specimens (10 limbs) and fixed with an external fixator. The native MAD and baseline TT-TG were measured using a CT scanogram. Subsequent scans were then performed altering the MAD using calibrated radiolucent wedges in 5 mm increments (0-25 mm) on a single side, using the contralateral limb as the control. Repeat measurements of MAD and TT-TG were obtained, and once completed, original alignment was restored, and the contralateral limb was taken through the same protocol with the opposite limb serving as the control. Measurements were performed by two independent observers and averages obtained. Linear regression models were created, and statistical analysis of variance was performed. Results: A CT-scanogram that measured TT-TG distances were significantly altered by changes in limb alignment. According to our linear regression model, each 1° of MAD alteration resulted in TT-TG change of approximately 0.4 mm. With every 5° change in limb alignment, the TT-TG changed by approximately 2 mm (Figure 1). Altering MAD from 6° valgus to 7° varus decreased the TT-TG mean from 14.3 mm to 7.7 mm, p < 0.05. Conclusions: Changes in coronal limb alignment through a distal femoral corrective osteotomy produce significant changes in TT-TG in addition to correcting MAD in a cadaveric model. These findings should be considered when determining appropriate corrective procedures for patients with valgus alignment and patellar instability. [Figure: see text]

Antegrade femoral lengthening and simultaneous hemiepiphysiodesis for congenital femoral deficiency.

Congenital femoral deficiency is characterized by limb length discrepancy and genu valgum. Lengthening of the femur along its anatomic axis increases valgus alignment by medial knee translation. Pairing limb lengthening with simultaneous medial distal femoral hemiepiphysiodesis can simultaneously correct two limb deformities. All skeletally immature patients with congenital femoral deficiency who underwent antegrade femoral lengthening and concomitant guided growth over a 4-year period were reviewed. Length and alignment data were quantified during lengthening, consolidation, and for 1 year after guided growth implants were removed or the patient reached skeletal maturity. Digital simulation was performed for all lengthenings to assess the mechanical alignment that would have been achieved had lengthening been performed without medial distal femoral hemiepiphysiodesis. Nine patients (five males, four females, mean age = 12.3 ± 1.9 years) underwent 10 antegrade intramedullary femoral lengthenings with simultaneous medial distal femoral hemiepiphysiodesis. All had improvement in valgus alignment (average improvement in mechanical axis deviation was 18 ± 11 mm, average change in limb alignment was 6 ± 5°). In simulated lengthenings without guided growth, all limbs would have experienced increased lateral mechanical axis deviation of 5 ± 3 mm. The hemiepiphysiodesis implant and lengthening device were explanted simultaneously in 7 of 10 lengthenings. Simultaneous medial distal femoral hemiepiphysiodesis with antegrade femoral lengthening for ongenital femoral deficiency can minimize the number of surgical episodes for the skeletally immature patient. The lengthening device and guided growth construct can be removed simultaneously in a majority of cases, saving children one or two additional surgical treatments.

Effect of limb alignment correction on medial meniscus extrusion under loading condition in high tibial osteotomy

BackgroundThis study aimed to investigate the effect of high tibial osteotomy (HTO) on medial meniscus extrusion (MME) and the association between the changes in limb alignment and MME under weight-bearing (WB) conditions after HTO. MethodsWe included 17 patients with knee osteoarthritis (OA) who underwent HTO. MME was evaluated using ultrasonography in supine and unipedal standing positions. Knee alignment was evaluated radiographically using WB, whole-leg radiographs with the hip-knee-ankle angle (HKAA), percentage of the mechanical axis (%MA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA). All measurements were performed serially at four time points: preoperative and 3, 6, and 12 months postoperative. Clinical outcomes were assessed by knee injury and osteoarthrosis outcome score (KOOS) and visual analogue scale (VAS) value for pain. ResultsMean MME in the WB position was significantly greater than that in the supine position in the preoperative condition; however, MME in both supine and WB positions was significantly lowered postoperatively. The ΔMME, difference of MME between supine and WB positions, was significantly lowered postoperatively and maintained for up to 1 year. MME change in the WB position between preop and postoperative conditions was significantly correlated with change in HKAA and %MA at 1 year postoperative. KOOS and VAS score were significantly improved after HTO. ConclusionsHTO correcting varus alignment can decrease MME in WB position and minimise the change in MME between supine and WB positions. The changes in MME after HTO were correlated with changes in the mechanical alignments.

Limb alignment changes with knee flexion: A study based on CAS data

BackgroundRecent evidence has questioned the value of standing limb alignment for predicting the adduction moment and forces exerted on healthy and prosthetic knees. The purpose of this study was to assess the lower limb alignment of OA knee patients at various knee flexion angles.The main hypothesis was that lower limb alignment measured throughout knee flexion does not significantly differ between patients displaying different extension alignment (neutral, varus or valgus). Methods206 arthritic knee patients undergoing computer-assisted total (CAS) knee prosthesis were included. Frontal limb alignment was assessed in a systematic manner by CAS at three knee positions: extension, 90 degrees of flexion and maximal flexion. The HKA angle at each knee position and the change in HKA angle between two knee positions (delta value) were reported and compared. ResultsA large proportion of OA patients had significant variation in their lower limb alignment (32% with Δ HKA > 5°). The extended limb deformity tended to reduce with knee flexion: mean of 5° and 6° deformity reduction for varus and valgus patients, 40% and 66% of varus and valgus patients progressed to neutral alignment with 90° knee flexion. Forty percent of neutral extended lower limb did not maintain their neutral alignment but rather progressed to either varus or valgus at 90° knee flexion. ConclusionsLimb alignment in extension is a poor predictor of limb alignment in flexion in OA patients.Only considering the traditional frontal alignment of an extended lower limb for planning knee arthroplasty or osteotomy is likely insufficient.

Alignment analysis of Brainlab knee 3 navigation-guided total knee arthroplasty using the adjusted mechanical method.

With the application of navigation technology in Total Knee Arthroplasty (TKA), TKA procedures have become various. Studies have shown that navigation can improve the alignment of patients' lower limbs. To verify this conclusion, we collected the clinical data from patients who underwent Brainlab knee 3 navigation-guided TKA. Brainlab knee 3 is a completely new software that takes a different approach to address the current challenges of navigated TKA. During the procedure, we applied the Adjusted Mechanical Alignment (AMA) principle and took soft tissue balance as a priority. We aim to explore the patients' lower limb alignment changes who underwent the Brainlab knee 3 navigation-guided TKA using the AMA method. Fifty consecutive patients who underwent total knee arthroplasty using the Brainlab knee3 knee navigation system (Smith&Nephew) from January to August 2021 by the same doctor (Yunsu Chen) in the Department of Joint Surgery of the Shanghai Sixth People's Hospital were included. Hip-Knee-Ankle Angle (HKAA), anatomic Femur Tibia Angle (FTA), Lateral Distal Femoral Angle (LDFA), and medial proximal tibia angle (MPTA) were measured on preoperative and postoperative full-length lower-limbs x-ray films or weight-bearing anterior and lateral knee radiographs for observational and descriptive study. The preoperative and postoperative knee alignment changes were analyzed through paired t-test or nonparametric Wilcoxon test using SPSS 25.0 software. Pre-operative and post-operative HKAA both obeyed normal distribution. The mean preoperative HKAA was 169.8° (154.9-178.7°) with a standard deviation of 5.41; the postoperative HKAA was 175.7° (168.4-180.0°) with a standard deviation of 2.81. Using the two-sample paired t-test to analyze, the result showed P = 0.000 < 0.05; a statistically significant difference exists. The preoperative and postoperative FTA obeyed normal distribution as well. The mean preoperative FTA was 174.7° (163.4-179.9°) with a standard deviation of 3.90; postoperative 175.6° (167.0-179.9°) with a standard deviation of 2.77. Using the two-sample paired t-test to analyze, the result showed P = 0.140 > 0.05, the difference was not statistically significant. The preoperative LDFA was normally distributed, while postoperative LDFA was not. The mean preoperative LDFA was 90.7° (83.5-99.6°) with a standard deviation of 3.83; the median of postoperative LDFA was 91.6° (86.0-103.2°) with an interquartile range of 2.93. Using the two-sample paired Wilcoxon test, the result showed P = 0.052 > 0.05; the difference was not statistically significant. Preoperative MPTA obeyed normal distribution, while postoperative MPTA did not. The mean preoperative MPTA was 83.5° (72.7-92.9°), with a standard deviation of 3.66; the median of postoperative MPTA was 89.3° (84.6-95.6°), with an interquartile range of 1.45. Using the two-sample paired Wilcoxon test, the result shows P = 0.000 < 0.05; a statistically significant difference exists. In our study, AMA alignment was applied in Brainlab Knee3 computer navigation-assisted total knee arthroplasty. The femoral and tibial osteotomy angles were minimally adjusted according to soft tissue situations to reduce soft tissue release. We found AMA alignment provides good control of knee alignment in the coronal plane of the lower limbs, which is a reliable technique.

Foot and/or ankle problems following limb alignment changes in uni-compartmental knee arthroplasty

Objective Foot and/or ankle (F/A) problems may be encountered in medial uni-compartmental knee (UKA) patients postoperatively due to the limb alignment changes and alterations in weight bearing of F/A. This study aimed to evaluate the risk factors and the incidence of foot and ankle (F/A) problems in (UKA) arthroplasty patients. Methods Patients who underwent UKA between 2016 and 2019 in our clinic were evaluated and the presence of F/A problems was recorded. Radiologic evaluations included hip knee ankle angle (HKA), medial proximal tibial angle, posterior tibial slope angle, talar tilt angle, talar inclination, talar dome to mechanical axis (TDMA), and talocrural angle (TCA) measured on preoperative and follow-up long-leg standing radiographs. The range of motion, Q angles, and muscle strengths were measured. Visual analog scale, physical performance limitations, and patient-reported activity limitations were evaluated for all patients. Patients with reported F/A problems were additionally evaluated with Foot Functional Index. Results Forty-four patients (38 female, 6 male; mean age 58.66 ± 8.6 years; mean BMI 31.30 ± 3.81, mean follow-up period 34.22 ± 18.95 months) were included in the study. There were 13 patients (29.5%) with reported F/A problems. Postoperative comparison of patients with and without F/A problems showed statistically significant differences in only WOMAC and SF12 physical health sub-scores ( p = 0.002, p = 0.003, respectively). There was no significant postoperative change in TDMA in patients with F/A problems ( p &gt; 0.05) in contrast to patients without F/A problems ( p = 0.006). There was no statistically significant difference in preoperative TCA measurements between groups ( p = 0.79). Comparison of knee and ankle radiologic measurements between groups demonstrated significant difference only in postoperative HKA measurements (−2.82 ± 2.53 vs. −0.80 ± 3.12, p = 0.033). Conclusion F/A problems adversely affecting the functional status were frequent in our cohort of UKA patients. Postoperative residual varus deformity may be a risk factor for this. Therefore, if slight varus alignment is aimed at UKA patients, preoperative F/A status should be evaluated.

Effect of Limb Alignment in Medial Unicompartmental Knee Arthroplasty on Functional Outcomes and Patient Satisfaction

Background: Unicompartmental knee arthroplasty (UKA) is effective in the treatment of symptomatic unicompartmental knee osteoarthritis. However, ideal limb alignment and acceptable changes of alignment remains contentious. Purpose: The purpose of this study is to look at the impact of post-operative mechanical limb alignment on short term functional outcomes in an Asian population. Methods: We performed a retrospective review of all mobile bearing, Oxford UKAs performed from July 2016 to January 2019 by a single-surgeon (43 patients, 47 knees). Pre- and post-operative weight bearing radiographic parameters were measured, as well as functional assessments via Oxford knee society (OKS) scores and the original Knee society score (KSS). Results: The post-operative mechanical axis mean was varus 4.3° (range valgus 2° to varus 10°), with a mean correction of 4.4° towards valgus. All our patients had an improvement in functional scores and range of movement post-operatively, however, patients with pre-operative alignment of varus 15° did not meet the cut off for minimal important change (MIC) in OKS scores. More varus pre-operative alignment resulted in a larger degree of change in limb alignment post-operatively. A larger change in alignment was also associated with higher satisfaction scores in patients. Conclusion: Post-operative limb alignment of up to 10° varus does not compromise short term functional outcome scores in medial UKA. Caution is advised when selecting patients with varus 15° and above for UKA as they may not be able to achieve a minimal important change in functional scores post-operatively.

Trampoline-related fractures of the proximal tibia in children

BackgroundTrampoline-related fractures of the proximal tibial metaphysis are common in children and have been linked to subsequent valgus deformity of the tibia. The purpose of this study was to investigate the characteristics of trampoline-related proximal tibial fractures in young children.MethodsWe evaluated 40 patients with proximal tibial fracture after trampolining between 2013 and 2019. The median duration of follow-up was 18 months. Standing long leg radiographs were obtained at the last follow-up to evaluate angular deformity and limb length inequality in the patients. The measurements recorded include the lower limb length, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), mechanical axis deviation (MAD), and anatomical tibio-femoral angle (aTFA). The anterior tilt angle (ATA) was measured using a lateral radiograph of the tibia.ResultsThe median age at injury was 40.0 months. Using trampoline with a heavier person was the most common mechanism of injury. aTFA and MAD were found to be increased towards the valgus at the last follow-up in our patient; however, the increase was not statistically significant (p = 0.692 and p = 0.973, respectively). The anterior tilt angle was increased in the injured leg at the last follow-up. But the change was not statistically significant (p = 0.09).ConclusionsUsing trampoline with a heavier person carries the risk of trampoline-related proximal tibial fracture in young children. We did not find a significant change in limb alignment at a minimum of one year of follow-up.

Varus deformity in the proximal tibia and immediate postoperative varus alignment result in varus progression in limb alignment in the long term after total knee arthroplasty.

The aim of this study was to examine and evaluate the factors associated with changes in limb alignment 10years after total knee arthroplasty (TKA). The hypothesis was that bone morphology and immediate postoperative alignment could be correlated with long-term post-operative alignment changes following TKA. This study retrospectively analysed 136 consecutive primary TKA cases for varus deformity, performed from 2006 to 2008, that could be followed for at least 10years postoperatively. Anteroposterior long-leg weight-bearing radiographs were obtained within 1month and at least 10years after surgery. The hip-knee-ankle (HKA) angle immediately after surgery was compared with that 10years later; factors correlating with the change in HKA angle (δHKA) were evaluated. The mean HKA angles were significantly different between immediate and long-term postoperative assessments (0.1° ± 1.9° vs. 1.2° ± 2.9°, p < 0.001). Furthermore, a significant difference was observed in the outlier ratio (> 3° deviation from the 0° of HKA angle) (10% vs. 24%, p = 0.002). δHKA strongly correlated with a higher preoperative tibial plateau tip-to-proximal tibial shaft (TPTPS) angle, higher postoperative HKA angle, lateral distal femoral angle, and lower postoperative medial proximal tibial angle. Varus deformity in the proximal part of the tibia, immediate postoperative varus alignment, and varus position of the femoral and tibial components may lead to varus progression in limb alignment in the long term, even 10years after TKA; the surgeon should, therefore, weigh the risks of leaving a varus alignment during surgery. Moreover, if the preoperative TPTPS angle is high, the alignment may become varus after TKA, even in patients who have acquired neutral alignment. IV.

Influence of Lower Limb Alignment Changes before and after Total Knee Arthroplasty on Kinematic Characteristics during Walking

Influence of Lower Limb Alignment Changes before and after Total Knee Arthroplasty on Kinematic Characteristics during Walking

Medial joint line elevation of the tibia measured during surgery has a significant correlation with the limb alignment changes following medial unicompartmental knee arthroplasty.

This study aimed to determine the correlation between the change in joint line height calculated from the resected bone and insert thickness during surgery and the change in limb alignment following unicompartmental knee arthroplasty (UKA). It was hypothesized that joint line elevation is correlated with the change in limb alignment. A total of 74 consecutive patients diagnosed with either isolated medial compartmental osteoarthritis (38 patients) or spontaneous osteonecrosis of the knee (36 patients) were included. The thickness of the proximal tibial and distal femoral bony cuts was measured during surgery; using these values, the medial joint line elevation of the tibia (MJLET) and medial joint line reduction of the femur (MJLRF) were defined. The correlation between the amount of change in the hip-knee-ankle (HKA) angle before and after surgery (δHKA) and the thickness of the tibial insert (TI), MJLET, or MJLRF were evaluated. The mean values of δHKA, TI, MJLET, and MJLRF were 5.0° ± 2.6°, 8.5 ± 0.8, 4.4 ± 1.3, and 0.0 ± 1.1mm, respectively. The δHKA had a significant, but weak-positive correlation with the TI (P = 0.02), and moderate-positive correlation with MJLET (P < 0.001). However, no correlation was observed between δHKA and MJLRF. The MJLET measured during surgery had a significant moderate-positive correlation with the change in limb alignment following medial UKA. For clinical relevance, the surgeon can predict postoperative limb alignment after UKA by considering, intraoperatively, both the insert thickness and the depth of resection at the proximal tibia thus minimizing technical error to obtain an optimal alignment after UKA. Diagnostic study, level II.

Biomechanical Implications of an Oblique Knee Joint Line.

Surgical correction of multiapical deformities of the lower limb requires careful preoperative planning. Surgeons must account for the potential creation of secondary deformity, such as knee joint line obliquity, and the risks associated with accepting these changes in limb alignment. In this study, we evaluate the effect of knee joint obliquity on tibial plateau contact pressures and knee instability. Three cadaveric knees were dissected and put through biomechanical testing to simulate loading of an oblique knee joint. We observed < 1 mm femoral displacement (proxy measure of instability) between 15 degrees of varus tilt and 10 degrees of valgus tilt, and greater increases in tibial plateau contact pressures with valgus tilt than with varus tilt. Our results suggest that, if the creation of a secondary coronal plane deformity at the knee joint cannot be avoided, up to 15 degrees of varus or 10 degrees of valgus alignment can be tolerated by an otherwise structurally normal knee.

Reinforcement strategy for lateral rafting plate fixation in posterolateral column fractures of the tibial plateau: The magic screw technique

BackgroundA posterolateral column fracture of the tibial plateau (PLCF) is not uncommon, especially lateral and bicondylar tibial plateau fractures. Currently, there is no consensus on the methods of surgical treatment for PLCF, including the surgical approach or the fixation strategy. Though various posterior approaches have been explored and can allow posterior buttress plate fixation, the necessity of a posterior approach with fixation for PLCFs is increasingly questioned. Meanwhile, there is no literature to analyse the morphological features of PLCFs. None of the available surgical techniques can solve all of the problems of PLCFs. MethodsFrom February 2016 to June 2016, an inconsecutive series of 16 patients who suffered Schatzker type II tibial plateau fractures involving the posterolateral column were selected based on an analysis of the morphological characteristics of PLCFs. The patients were all treated by lateral rafting plate fixation with magic screw implantation through the extended lateral approach. ResultsAccording to PLCF morphology, 4 patients had mild slope-type depression fractures (MSDF) of the articular surface, and the other 12 patients had block-type splitting fractures (BSF). After a 12-month follow-up period, there were no complications related to the fixation technique and no significant changes in limb alignment. At the final follow-up, the average range of motion (ROM) of the affected knees was 2.3°−125°, and the average HSS score was 94.2. ConclusionsThe selected patients who suffered Schatzker type II fractures involving the posterolateral column could be successfully treated via lateral rafting plate fixation with the magic screw technique. For PLCF treatment, magic screw fixation is a valuable technique that may reduce the utilization of posterior approaches and posterior fixations.

The influence of surgical factors on dislocation of the meniscal bearing after Oxford medial unicompartmental knee replacement: a case-control study.

The aim of this study was to evaluate the risk factors for dislocation of the bearing after a mobile-bearing Oxford medial unicompartmental knee replacement (UKR) and to test the hypothesis that surgical factors, as measured from post-operative radiographs, are associated with its dislocation From a total of 480 UKRs performed between 2001 and 2012, in 391 patients with a mean age of 66.5 years (45 to 82) (316 female, 75 male), we identified 17 UKRs where bearing dislocation occurred. The post-operative radiological measurements of the 17 UKRs and 51 matched controls were analysed using conditional logistic regression analysis. The post-operative radiological measurements included post-operative change in limb alignment, the position of the femoral and tibial components, the resection depth of the proximal tibia, and the femoral component-posterior condyle classification. We concluded that a post-operative decrease in the posterior tibial slope relative to the pre-operative value was the only significant determinant of dislocation of the bearing after medial Oxford UKR (odds ratio 1.881; 95% confidence interval 1.272 to 2.779). A post-operative posterior tibial slope < 8.45° and a difference between the pre-operative and post-operative posterior tibial slope of > 2.19° may increase the risk of dislocation.

Rotational limb alignment changes following total knee arthroplasty

The aim of the present study was to assess the changes in rotational alignment introduced by total knee arthroplasty (TKA) and the reproducibility of pre- and postoperative CT measurements of rotational limb alignment. For this purpose we analyzed data from 196 consecutive cruciate-retaining, fixed bearing Columbus TKA procedures. Both pre- and postoperative scans torsion difference CT scans were available for measurements in 89 cases. Using these CT scans the neck-malleolar angle (NMA), the femoral posterior condylar angle (fPCA), the tibial posterior condylar axis (tPCA) and the tibial torsion angle (TTA) were independently assessed by three raters. CT scans were re-evaluated 8 weeks later by the most experienced rater for assessment of intraobserver agreement. Measurements of all angles were prone to high standard deviations reflecting interindividual variability. Mean fPCA changed from 1.3° to 2.7° internal rotation preoperatively to 0.1°-1.9° internal rotation postoperatively. Based on a relative external rotation of the tibial base plate as compared to the preoperative situation, we found a relative internal rotation of the postoperative NMA and tibial torsion of 3°-5.4° and 6°-7.5°, respectively. Intra- and interobserver agreement was strong for all angles assessed (ICCs 0.7-1.0) except for fPCA (ICC 0.2-0.6). However, mean absolute measurement differences for fPCA were clinically acceptable (1.2°-2.6°). Reproducibility of CT rotational limb alignment measurements was found to be clinically acceptable. Rotational alignment of the femoral and even more so of the tibial component will ultimately affect the rotational alignment of the entire limb-at least when fixed bearings are used. Diagnostic study, Level III.

Lower Limb Alignment in Children

A full-length standing anteroposterior radiograph of the entire lower extremity has become the standard imaging modality for assessing lower limb alignment. Although reference values of frontal plane deformity parameters based on adult subjects have been established, such values may not be applicable to the pediatric population. The purpose of our study was to establish the reference values of frontal plane alignment and joint orientation angles in children based on a standing full-length radiograph. A database at a single institution was searched for patients who were aged between 1 and 18 years at the time of undergoing a standing full-length radiograph of the lower extremities. Radiographic analysis of lower extremities without any abnormalities was performed by a single observer. Mechanical axis deviation, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibiofemoral angle, joint line convergence angle, and mechanical axis station were calculated at yearly intervals. The data were summarized using descriptive statistics, and simple regression analysis was performed to determine the relationship between the patients' age and the magnitude of LDFA and MPTA. A total of 354 unaffected lower extremities in 253 children were analyzed. Between the ages of 1 and 2 years, the tendency for varus alignment of the lower limb was related to the varus orientation of the distal femur with a mean LDFA of 95 degrees (95% confidence interval [CI], 93-97 degrees). By the age of 3 years, the limb alignment changed to valgus related to a combination of decreasing varus orientation of the distal femur and a mild increase in valgus orientation of the proximal tibia with the mean MPTA changing from 89 degrees (95% CI, 88-90 degrees) to 91 degrees (95% CI, 90-92 degrees). After the age of 7 years, all joint orientation angles were noted to be within the range of reference values that are available for the adult population. Despite changes in limb alignment with growth, the mean mechanical axis of the lower extremity remained within the central half of the knee joint in children older than 1 year of age. The change in alignment of the lower limb from 1 to 4 years of life from varus to valgus is primarily related to a progressive decrease in varus orientation of the distal femur. In children younger than 7 years old, age-specific reference values for joint orientation angles of the lower extremity should be used instead of values derived from adult subjects.

Underestimation of varus angulation in knees with flexion deformity

In order to investigate the change in limb alignment in cases of knee flexion deformity, 17 male volunteers aged from 25 to 35 years with no complaints and no knee disorders were selected. The femorotibial angle (FTA), which is the lateral angle at the intersection between the femoral axis and the tibial axis in an anteroposterior radiograph, was employed as an index of limb alignment. FTA in standing on one leg with and without knee flexion was measured. The mean standing FTA was 179.4±19° in full extension, which decreased to 176.9±2.5° in a mean flexion position of 18±3.3° (range 15–25°) ( P<0.002), and in all cases, standing FTA in flexion was smaller (more valgus-angulated) than that in full extension. There was a significant positive relationship with a straight regression line ( D=0.101KFA+0.296, R=0.8505) between the angle of knee flexion (KFA) and the difference ( D) in standing FTA between full extension and knee flexion. We conclude that limb alignment became more valgus-angulated with an increase in flexion deformity.

Changes in knee alignment after total knee arthroplasty

Changes in limb alignment after total knee arthroplasty were evaluated in 20 knees replaced with the Miller Galante knee system. The mean follow-up period was 87.4 months. Seventeen of the 20 knees were in the varus position on theinitial postoperative radiographs, but the alignment significantly changed to become even more aligned toward varus during the follow-up period. The thickness of the ultra-high-molecular-weight polyethylene (UHMWPE) also decreased significantly in the medial femorotibial joint. The wear of the UHMWPE possibly changed the alignment, and the postoperative alignment had a positive correlation with the wear rate. The components should be implanted so that the mechanical axis intersects the center of the components to prevent worsening of alignment as well as to minimize any such wear.

A quantitative technique for reporting surface degradation patterns of UHMWPE components of retrieved total knee replacements.

A quantitative method of reporting surface degradation of the ultra-high molecular weight polyethylene (UHMWPE) tibial component from retrieved total knee replacements (TKR) was developed. Specific features include a qualitative assessment expressing the patterns in which the damage was detected as well as a quantitative summary of the observed degradation mechanisms. In addition, a method of measuring lower limb alignment changes with time is described and related to the observed damage patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damage observed on the tibial plateau appeared to occur subsequent to the changes in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb alignment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently available. In particular, the collection of temporal alignment data at clinical follow-up visits enhanced the assessment of the retrieved TKR.