What should be considered in using standard knee radiographs to estimate mechanical alignment of the knee?

Femorotibial angle on short knee radiographs fails to accurately predict the lower limb mechanical alignment. A systematic review and meta-analysis on different femorotibial angle definitions and short knee radiograph types

Introduction

Hip-knee-ankle angle (HKA) on Full Limb Radiographs (FLRs) is the gold standard for coronal knee alignment assessment. Despite the widespread utilization of the more convenient femorotibial angle (FTA) on either antero-posterior (AP) or postero-anterior (PA) short knee radiographs (SKRs), its definition and correlation with HKA remains controversial. This review is the first to systematically investigate FTA-HKA correlation and the effect of different FTA methods and SKRs.

Methods

Systematic literature search (Pubmed, Scopus, Cochrane Library) followed PRISMA guidelines, to evaluate studies examining the FTA-HKA correlation. Meta-analyses compared the 3 most common FTA methods, knee center determination method and SKR types.

Results

17 studies (2597 patients, 3234 knees) were included. The strongest correlation with HKA (r = 0.78) was found for FTA Method 1 (angle formed by lines drawn from the midpoint of tibial spines to points 10 cm above and below the joint line). No significant differences were observed when grouping the FTA methods by knee center assessment (Group I, r = 0.78; Group II, r = 0.77). AP SKRs showed a trend towards stronger FTA-HKA correlation compared to PA SKRs, in both Method 1 (r = 0.79 vs 0.75) and Method 3 (r = 0.80 vs 0.66).

Conclusion

Irrespective of its definition or type of SKR used, FTA lacks reliable accuracy in predicting the HKA in most knees. FLRs should be used whenever precise estimation of the patient's alignment is necessary. Caution is warranted in interpreting studies investigating knee alignment or knee arthroplasty outcomes based on FTA.

A Comprehensive, Multidisciplinary Assessment for Knee Osteoarthritis Following Traumatic Unilateral Lower Limb Loss in Service Members

INTRODUCTION

Knee osteoarthritis (KOA) is a primary source of long-term disability and decreased quality of life (QoL) in service members (SM) with lower limb loss (LL); however, it remains difficult to preemptively identify and mitigate the progression of KOA and KOA-related symptoms. The objective of this study was to explore a comprehensive cross-sectional evaluation, at the baseline of a prospective study, for characterizing KOA in SM with traumatic LL.

MATERIALS AND METHODS

Thirty-eight male SM with traumatic unilateral LL (23 transtibial and 15 transfemoral), 9.5 ± 5.9 years post-injury, were cross-sectionally evaluated at initial enrollment into a prospective, longitudinal study utilizing a comprehensive evaluation to characterize knee joint health, functionality, and QoL in SM with LL. Presences of medial, lateral, and/or patellofemoral articular degeneration within the contralateral knee were identified via magnetic resonance imaging(for medically eligible SM; Kellgren-Lawrence Grade [n = 32]; and Outerbridge classification [OC; n = 22]). Tri-planar trunk and pelvic motions, knee kinetics, along with temporospatial parameters, were quantified via full-body gait evaluation and inverse dynamics. Concentrations of 26 protein biomarkers of osteochondral tissue degradation and inflammatory activity were identified via serum immunoassays. Physical function, knee symptoms, and QoL were collected via several patient reported outcome measures.

RESULTS

KOA was identified in 12 of 32 (37.5%; KL ≥ 1) SM with LL; however, 16 of 22 SM presented with patellofemoral degeneration (72.7%; OC ≥ 1). Service members with versus without KOA had a 26% reduction in the narrowest medial tibiofemoral joint space. Biomechanically, SM with versus without KOA walked with a 24% wider stride width and with a negative correlation between peak knee adduction moments and minimal medial tibiofemoral joint space. Physiologically, SM with versus without KOA exhibited elevated concentrations of pro-inflammatory biomarker interleukin-7 (+180%), collagen breakdown markers collagen II cleavage (+44%), and lower concentrations of hyaluronic acid (-73%) and bone resorption biomarker N-telopeptide of Type 1 Collagen (-49%). Lastly, there was a negative correlation between patient-reported contralateral knee pain severity and patient-reported functionality and QoL.

CONCLUSIONS

While 37.5% of SM with LL had KOA at the tibiofemoral joint (KL ≥ 1), 72.7% of SM had the presence of patellofemoral degeneration (OC ≥ 1). These findings demonstrate that the patellofemoral joint may be more susceptible to degeneration than the medial tibiofemoral compartment following traumatic LL.

The main cause of tibial prosthesis malalignment after total knee arthroplasty in Southern Chinese population

Objectives

This study aimed to determine the occurrence rate of malalignment of tibial prosthesis and explore the influencing factors.

Methods

296 patients from Southern China who underwent total knee arthroplasty (TKA) were selected as the research objects. Their general demographic data were recorded. The tibial bowing angle (TBA), tibial length, medial proximal tibial angle (MPTA), tibial plateau shift angle (TPSA), tibial bone loss, lateral distal tibial angle, and overall width of tibial plateau and widths of medial and lateral tibial plateau were measured before TKA. The tibial component coronal alignment angle (TCCA) was measured after the operation. Malalignment of the tibial prosthesis was defined as TCCA <87° or TCCA >93°. Tibial bowing was indicated by TBA >2°, and lateral bowing was recorded as +. The correlations of TCCA with demographic data and pre-operation imaging measurement parameters were statistically analyzed.

Results

Bivariate correlation analysis revealed negative correlations between TCCA and TBA (r = -0.602, P < 0.001) and TPSA (r = -0.304, P < 0.001), and a positive correlation with MPTA (r = -0.318, P < 0.001). Multivariate linear regression analysis demonstrated a significant negative correlation between TCCA and TBA (P < 0.001). The occurrence rate of malalignment of tibial prosthesis was 12.37 %. The occurrence rates of malalignment were 22.54 % in the tibial bowing group and 6.87 % in the non-tibial bowing group, showing statistical differences (P < 0.001).

Conclusion

The malalignment rate of tibial prosthesis among Southern Chinese patients is relatively high, possibly attributed to the tibial anatomy anomalies, particularly the tibial bowing. The entry point should be determined based on tibial morphology.

Exploring relationships among multi-disciplinary assessments for knee joint health in service members with traumatic unilateral lower limb loss: a two-year longitudinal investigation

Motivated by the complex and multifactorial etiologies of osteoarthritis, here we use a comprehensive approach evaluating knee joint health after unilateral lower limb loss. Thirty-eight male Service members with traumatic, unilateral lower limb loss (mean age = 38 yr) participated in a prospective, two-year longitudinal study comprehensively evaluating contralateral knee joint health (i.e., clinical imaging, gait biomechanics, physiological biomarkers, and patient-reported outcomes); seventeen subsequently returned for a two-year follow-up visit. For this subset with baseline and follow-up data, outcomes were compared between timepoints, and associations evaluated between values at baseline with two-year changes in tri-compartmental joint space. Upon follow-up, knee joint health worsened, particularly among seven Service members who presented at baseline with no joint degeneration (KL = 0) but returned with evidence of degeneration (KL ≥ 1). Joint space narrowing was associated with greater patellar tilt (r[12] = 0.71, p = 0.01), external knee adduction moment (r[13] = 0.64, p = 0.02), knee adduction moment impulse (r[13] = 0.61, p = 0.03), and CTX-1 concentration (r[11] = 0.83, p = 0.001), as well as lesser KOOSSport and VR-36General Health (r[16] = - 0.69, p = 0.01 and r[16] = - 0.69, p = 0.01, respectively). This longitudinal, multi-disciplinary investigation highlights the importance of a comprehensive approach to evaluate the fast-progressing onset of knee osteoarthritis, particularly among relatively young Service members with lower limb loss.

Effect of Total Hip Arthroplasty on Ipsilateral Lower Limb Alignment and Knee Joint Space Width: Minimum 5-Year Follow-up

BACKGROUND

This study aimed to 1) assess the effect of total hip arthroplasty (THA) on coronal limb alignment, namely, the hip-knee-ankle angle (HKA), 2) identify factors that determine changes in the HKA, and 3) determine whether alignment changes influence the knee joint space width.

METHODS

We retrospectively evaluated 266 limbs of patients who underwent THA. Three types of prostheses with neck shaft angles (NSAs) of 132°, 135°, and 138° were used. Several radiographic parameters were measured in the preoperative and final radiographs (at least 5 years after THA). A paired t-test was used to confirm the effect of THA on HKA change. Multiple regression analysis was performed to identify radiographic parameters related to HKA changes following THA and changes in knee joint space width. Subgroup analyses were performed to reveal the effect of NSA change on the HKA change, and the proportion of total knee arthroplasty usage and changes in radiographic parameters between maintained joint space and narrowed joint space groups were compared.

RESULTS

The preoperative mean HKA was 1.4° varus and increased to 2.7° varus after THA. This change was related to changes in the NSA, lateral distal femoral angle, and femoral bowing angle. In particular, in the group with a decrease in NSA of > 5°, the preoperative mean HKA was largely changed from 1.4° varus to 4.6° varus after THA. The prostheses with NSA of 132° and 135° also led to greater varus HKA changes than those with an NSA of 138°. Narrowing of the medial knee joint space was related to changes in the varus direction of the HKA, decrease in NSA, increase in femoral offset.

CONCLUSION

A large reduction in NSA can lead to considerable varus limb alignment after THA, which can have adverse effects on the medial compartment of the ipsilateral knee.

Proximal external femoral torsion increases lateral femoral shaft bowing: a study based on 3D CT reconstruction models

PURPOSE

Femoral bowing influences the genesis and management of knee osteoarthritis (OA). The aim of this study was to investigate the relationship between the femoral torsion angle (FTA) and femoral bowing angle (FBA) in a southern Chinese population. It was hypothesized that a greater FTA would lead to a greater lateral FBA.

METHODS

A total of 381 lower extremities from 381 osteoarthritic patients (298 women, 83 men; 201 left, 180 right; mean age 66.5 ± 8.9 years) were retrospectively reviewed. Age, sex, body mass index (BMI), side, height, femoral length (FL), hip-knee-ankle angle (HKA) and FTA were set as FBA-related factors. The three-dimensional (3D) FBA, the angle between the anatomical axis of the proximal femur and the anatomical axis of the distal femur in the plane they form, and its projection on the coronal (lateral FBA) and sagittal (anterior FBA) planes were measured on 3D computed tomography (CT) models. The correlation of the 3D, lateral and anterior FBAs with each of the FBA-related factors was explored using multiple linear regression analysis. The correlation between the FBA and FTA was explored and verified after using propensity score matching to control for the other FBA-related factors.

RESULTS

The mean lateral and anterior FBAs were 5.5°, with 53.5% greater than 5°, and 12.7°, with 70.3% greater than 11°, respectively. 3D FBA was positively correlated with age (Std.Co = 0.113, P < 0.05) and HKA (Std.Co = 0.129, P < 0.05). Lateral FBA was positively correlated with age (Std.Co = 0.118, P < 0.05), female sex (Std.Co = 0.206, P < 0.05), HKA (Std.Co = 0.184, P < 0.05) and FL (Std.Co = 0.220, P < 0.05). Anterior FBA was positively correlated with age (Std.Co = 0.108, P < 0.05) and male sex (Std.Co = 0.108, P < 0.05). When the related factors were balanced between the two groups (NS), FTA did not significantly affect 3D FBA or anterior FBA (NS), while FTA was positively correlated with lateral FBA (Std.Co = 0.165, P < 0.05).

CONCLUSION

External torsion of the proximal femur increases the lateral FBA by twisting a partial anterior FBA into a lateral FBA, especially in the female population. If a patient is found to have a large lateral FBA preoperatively, one should be alert to the possibility of a concomitant large FTA, as there are implications for femoral orthopedics, TKA and patellofemoral pressure distribution.

LEVEL OF EVIDENCE

III.

Visual Inspection for Lower Limb Malalignment Diagnosis Is Unreliable

OBJECTIVE

Visual inspection of the lower limb is often part of standard clinical practice during a physical examination at the outpatient clinic. This study aims to investigate how reliable visual inspections are in terms of detecting lower limb malalignments without additional tools and physical examinations.

DESIGN

This study enrolled 50 patients. Each patient underwent a whole leg radiograph (WLR); in addition, a standardized digital photograph was taken of the lower limbs. Four persons (different experience levels) visually rated the digital photograph twice (unaware of the hip knee angle [HKA] on the WLR) and placed them in the category: severe valgus (>5°); moderate valgus (2°-5°); neutral, moderate varus (2°-5°); and severe varus (>5°). Visual ratings were compared with the measured HKA on WLRs for correlation using Spearman's rho. Linear ordinal regression models with significance when P < 0.05 were used to test whether body mass index (BMI), age, gender, and HKA were possible risk factors for incorrect visual HKA assessment.

RESULTS

Spearman's rho between the visual assessment and measured HKA on the WLR was moderate with 0.478 (P < 0.01). Women had an increased odds ratio of 3.7 (P = 0.001) for incorrect visual assessment. Higher HKA also increased the odds ratio for erroneous visual assessment with 1.4 (P = 0.003). BMI and age did not significantly increase the odds of erroneous visual leg axis assessments in this study.

CONCLUSIONS

Visual assessment of the lower limb alignment does not provide clinically relevant information. Lower limb malalignment diagnoses cannot be performed using only a visual inspection. Physical examination tests and radiographical assessments are advised.

LEVEL OF EVIDENCE

Diagnostic level II.

High femoral anteversion in osteoarthritic knees, particularly for severe valgus deformity

Objective

Increased femoral anteversion (FA) has been correlated with less varus deformities in osteoarthritic (OA) knees, but the relationship between FA and the degree of valgus deformity in osteoarthritic (OA) knees is still largely unknown. We aimed to thoroughly analyze the distribution of FA in relation to varus or valgus deformities of the lower extremity in OA knees, and to further clarify the relationship between FA and trochlear morphology.

Methods

235 lower extremities with OA knees were divided into five groups according to the mechanical tibiofemoral angle: excessive valgus (< − 10°), moderate valgus (− 10° to − 3°), neutral (− 3° to 3°), moderate varus (3° to 10°), and excessive varus (> 10°). FA (measured using the posterior condylar axis [pFA] and the transepicondylar axis [tFA]) was measured, and the relationships of FA to the mechanical tibiofemoral angle and femoral trochlear morphology were identified.

Results

Excessive FA (pFA ≥ 20°) was observed in 30.2% of all patients and in 58.8% of patients in the excessive valgus group. pFA showed a strong correlation with mechanical tibiofemoral angle (p = 0.018). Both the pFA and the tFA of patients in the excessive valgus group were greater than those in other four groups (all p ≤ 0.037). There were significant correlations between tFA and trochlear parameters, including the sulcus angle (SA), lateral trochlear slope (LTS), and medial trochlear slope (MTS) (all p ≤  0.028).

Conclusion

High FA is prevalent, particularly in severe valgus knees, and FA is significantly related to the femoral trochlear morphology in OA knees. With the aim of improving the patellofemoral prognosis and complications, high FA should be considered during total knee arthroplasty.

Correlation of short knee and full-length X-rays in evaluating coronal plane alignment in total knee arthroplasty

Background

Coronal alignment after total knee arthroplasty (TKA) would influence the implant survival. Coronal alignment could be measured on short and full-length X-rays. The goal of the current study was to assess the correlation of short and full-length X-rays to accurate prediction of the true Hip-Knee-Ankle alignment after TKA in the Iranian population.

Methods

Lateral distal femoral and medial proximal tibial angles, FTA, HKA, in 180 Iranian patients (243 knees without extra-articular deformities) were measured and compared on short and full-length standing X-rays of primary TKA pre/postoperatively.

Results

The correlation between the preoperative FTA-short and FTA-long, FTA-short and HKA, and FTA-long and HKA values in degrees were fair, good and good (r = 0.64) (r = 0.73), (r = 0.76), respectively. This correlation for postoperative aMPTA and mMPTA (r = 0.73), and FTA-short and HKA (r = 0.76) values were good and significant (P = 0.001). Also, assessing coronal alignment based on short and full-length measurements would result in varying pre/postoperative alignments (varus, neutral and valgus).

Conclusion

Full length X-rays could not be replaced by short knee X-rays to asses true coronal alignment in TKA; considerable portion of our cases were missorted as varus, neutral or valgus based on the FTA versus the HKA. Intraoperative fixed 5° valgus angle cut of distal femur did not result in postoperative favorable neutral alignment in all cases.

Level of evidence

IV.

Effect of anterior tibial bowing on measurement of posterior tibial slope on conventional X-rays

PURPOSE

The posterior tibial slope (PTS) has different biomechanical effects on the knee. Especially in revision ACL reconstruction, a precise analysis is essential. Therefore, we investigate the influence of the anterior tibial bowing angle on the posterior slope measurement. Our hypothesis of the present study is that the short tibial X-rays underestimate the PTS in cases with increased anterior bowing of the tibia.

METHODS

The PTS was measured on 162 true longitudinal radiographs of the complete tibia (lateral mechanic axis). The average age of the patients was 35.7 years (range 19-59 years) and the most common diagnosis was failed anterior cruciate ligament reconstruction. Using this X-ray, the slope on the short axis and the slope on the entire axis were measured. In addition, the angle of the anterior bowing was determined.

RESULTS

The mean PTS for the lateral mechanic axis of the tibia was 10.6° (± 3.5) in contrast to 11.6° (± 3.5) for the short tibial axis. These two measurements differ significantly. (p  < 0.001). The mean anterior tibial bowing angle on the lateral X-rays of the whole tibia was 2.3° (± 2.0). There is a significant positive, relationship between tibial bowing angle and PTS as referenced by the lateral mechanic axis (Spearman's correlation, r = 0.273 and p < 0.001).

CONCLUSION

With increasing anterior tibial bowing, the posterior tibial slope on the short knee radiograph is underestimated compared to the slope measurement on the lateral mechanic axis.

Non-weight-bearing short knee radiographs to evaluate coronal alignment before total knee arthroplasty

Background

Whole leg radiograph (WLR) is the gold standard in assessing lower limb alignment before total knee arthroplasty (TKA) although in practice, non-weight-bearing short knee radiographs (NWB SKRs) are used by most medical institutions. The objective of this study was to determine whether the femorotibial angle (FTA) could be used to evaluate lower limb alignment on limited NWB SKRs. We also investigated whether FTA alignment measurements on NWB SKRs and WLRs differed depending on the direction of knee deformity.

Methods

In all, 105 knees which underwent both NWB SKR and WLR were included. Measurement of hip-knee-ankle angle (HKA) was obtained through WLR, while the FTA was found using NWB SKR (FTA_SKR) and WLR (FTA_WLR). All knees were divided into three groups based on the HKA. The Kappa statistic was used to compare the agreement of categorical alignment variables between the HKA and FTA_SKR. The agreement of the measurements obtained from the two radiographs was made using Bland-Altman plots and intraclass correlation coefficient (ICC). Pearson correlation coefficient and simple linear regression analysis were also conducted to evaluate the correlation between different angles.

Results

The agreement for categories of lower limb deformity was rated excellent (kappa =0.804, P<0.001). The Bland-Altman plot showed that the mean difference for the FTA_SKR and FTA_WLR was 4.4°. There was an excellent correlation (r=0.861, P<0.001) and good reliability (ICC, 0.607) between the FTA_SKR and HKA. For the varus group, there was a good correlation between the FTA_SKR and HKA (r=0.650, P<0.001); however, there were no significant correlations between the FTAS KR and HKA in the neutral (r=0.106, P=0.543) and valgus groups (r=0.322, P=0.102).

Conclusions

For outpatient follow-up, we found that the FTA on NWB SKRs is an acceptable means for classifying knee alignment (varus, neutral, or valgus). The measurement on NWB SKR also showed excellent correlation and good agreement with the HKA. For varus knees, NWB SKR measurements showed the best correlation with the HKA. However, for neutral and valgus knees, NWB SKR measurements were insufficient for conducting a reliable calculation and quantification of coronal alignment of the lower limb.

Relationship between radiographic measurements and knee adduction moment using 3D gait analysis

BACKGROUND

Radiographic factors estimate the state of the static knee joint, and it is questionable how well these parameters reflect the dynamic knee condition. The external knee adduction moment (KAM) during gait is known to be a kinetic variable contributing to osteoarthritis progression. This study aims to investigate the effects of static radiographic parameters on the dynamic KAM during gait.

METHODS

Overall, 123 patients (mean age, 65.7 years; standard deviation, 8.1 years; 34 men and 89 women) were included. Seven radiographic parameters including the mechanical tibiofemoral angle (mTFA), Kellgren-Lawrence grade, and ankle joint line orientation (AJLO) were measured on radiographs, and the maximum KAM and KAM-time integral in the stance phase were obtained using three-dimensional gait analysis. The correlation and multiple regression analyses were performed for identifying significant radiographic measurements associated with the KAM.

RESULTS

Most of the radiographic measurements correlated with the maximum KAM and KAM-time integral. As a result of multiple regression analysis, the mTFA (p < 0.001) and AJLO (p = 0.003) were identified as significant factors associated with the KAM-time integral (R² = 0.450); the mTFA (p < 0.001) and AJLO (p = 0.003) were identified as a significant factor associated with the maximum KAM (R² = 0.352) in multiple regression analysis. The discriminant validity of KAM was highest at varus 5.7 degree of the mTFA and 7.5 degree of the AJLO.

SIGNIFICANCE

The mTFA and AJLO were significantly associated with the KAM. However, to be used as a surgical indication for corrective osteotomy, a longitudinal study is needed to validate whether the mTFA and AJLO values directly cause osteoarthritis progression as we have suggested.

LEVEL OF EVIDENCE

III.

Association of Machine Learning-Based Predictions of Medial Knee Contact Force With Cartilage Loss Over 2.5 Years in Knee Osteoarthritis

OBJECTIVE

The relationship between in vivo knee load predictions and longitudinal cartilage changes has not been investigated. We undertook this study to develop an equation to predict the medial tibiofemoral contact force (MCF) peak during walking in persons with instrumented knee implants, and to apply this equation to determine the relationship between the predicted MCF peak and cartilage loss in patients with knee osteoarthritis (OA).

METHODS

In adults with knee OA (39 women, 8 men; mean ± SD age 61.1 ± 6.8 years), baseline biomechanical gait analyses were performed, and annualized change in medial tibial cartilage volume (mm³ /year) over 2.5 years was determined using magnetic resonance imaging. In a separate sample of patients with force-measuring tibial prostheses (3 women, 6 men; mean ± SD age 70.3 ± 5.2 years), gait data plus in vivo knee loads were used to develop an equation to predict the MCF peak using machine learning. This equation was then applied to the knee OA group, and the relationship between the predicted MCF peak and annualized cartilage volume change was determined.

RESULTS

The MCF peak was best predicted using gait speed, the knee adduction moment peak, and the vertical knee reaction force peak (root mean square error 132.88N; R² = 0.81, P < 0.001). In participants with knee OA, the predicted MCF peak was related to cartilage volume change (R² = 0.35, β = -0.119, P < 0.001).

CONCLUSION

Machine learning was used to develop a novel equation for predicting the MCF peak from external biomechanical parameters. The predicted MCF peak was positively related to medial tibial cartilage volume loss in patients with knee OA.

Association of osteoporosis and varus inclination of the tibial plateau in postmenopausal women with advanced osteoarthritis of the knee

Background

Although varus inclination of the tibial plateau has increasingly been recognized as a major risk factor in the progression of Osteoarthritis of the knee (OA knee), little attention has been placed on the development of the varus inclination of the tibial plateau. Osteoporosis is a disease characterized by low bone mass and may increase the risk of a stress fracture in the proximal tibia. To date, risk factors for varus inclination of the tibial plateau are rarely reported. In this study, we investigated Bone Mineral Density (BMD) as a risk factor of varus inclination of the tibial plateau in postmenopausal women with advanced OA knee.

Methods

A total of 90 postmenopausal women with varus OA knee who had received a total knee arthroplasty in our department between January 2016 and December 2019 were reviewed. Certain factors may correlate to inclination of the tibial plateau (Medial Tibial Plateau Angle, MTPA), including age, operation side, Kellgren-Lawrence grade of OA knee, BMD, Body Mass Index (BMI), Lateral Distal Femur Angle (LDFA), lower extremity alignment (Hip-Knee-Ankle angle, HKAA), and history of both spinal compression fracture and hip fracture were collected and analyzed.

Results

Osteoporosis, lower extremity varus malalignment and age were significantly associated with varus inclination of the tibial plateau (MTPA) (P = 0.15, 0.013 and 0.033 respectively). For patients with a lower extremity varus malalignment (HKAA < 175°), osteoporosis (T-score ≤ -2.5) was significantly associated with inclination of the tibial plateau. For patients with a normal lower extremity alignment (HKAA ≥ 175°), no significant association was found between osteoporosis (T-score ≤ -2.5) and varus inclination of the tibial plateau.

Conclusions

Osteoporosis, lower extremity varus malalignment and age are major risk factors for inclination of the tibial plateau in postmenopausal women with OA knee. More attention needs to be given to the progression of varus OA knee in postmenopausal women who simultaneously has osteoporosis and lower extremity varus malalignment.

True Mechanical Alignment is Found Only on Full-Limb and not on Standard Anteroposterior Radiographs

Purpose

The purpose of this study was to compare alignment measured on standard anteroposterior (AP) radiographs versus full-length weight-bearing radiographs.

Methods

Patients were prospectively enrolled from June 2019 to August 2019 from a single orthopedic surgeon's practice if they were ≥ 18 years of age, obtained both AP and full-length alignment radiographs and were capable of full weight-bearing with appropriate positioning. Patients were excluded if they were < 18 years of age, had previous knee arthroplasty, previous knee or hip osteotomy, were unable to bear full weight on both limbs, and if the patient's body habitus precluded appropriate visualization of necessary landmarks on the radiographs. Tibiofemoral angles were measured on AP radiographs using 2 techniques (AP angles 1 and 2). Linear regression and paired t tests were used to compare measurements. The minimal clinically important difference was defined as < 2°.

Results

There were 120 patients (62 males, 58 females) with an average age of 45 ± 17 years who were enrolled. There were positive correlations between average alignment on full-length weight-bearing and AP radiographs for AP angle 1 (r = 0.72) and AP angle 2 (r = 0.76) measurement techniques (P < .001). There was a significant difference in mean alignment between full-length weight-bearing and AP measurements (AP angle 1: 2.5° difference; AP angle 2: 4.4° difference; P < .001). Frequency distributions for the minimal clinically important difference between true mechanical alignment and AP views demonstrated that 46.7% of patients had ≥ 2° difference for AP angle 1, and 78.3% of patients had ≥ 2° difference for AP angle 2.

Conclusion

The average absolute difference in alignment measured between standard AP radiograph and full-length weight-bearing radiograph views was significant, with 46.7% to 78.3% of patients having a greater than 2° absolute difference between these 2 views. In cases where precise objective alignment measurement is necessary, full-length weight-bearing radiographs are recommended over standard AP radiographs for presurgical planning so as to reduce potential error in over- or underestimation of the true mechanical alignment.

Study Design

Prospective case-comparison; Level of evidence, 1.

Dome-shaped high tibial osteotomy with semi-circular Ilizarov pin fixator: Mid- to long-term results of a novel technique

BACKGROUND

The aim of this study was to assess the clinical and radiological results of the dome-shaped high tibial osteotomy (HTO) which was fixed with a novel construct comprised of semi-circular Ilizarov frames and pins.

METHODS

The patients with at least five years of follow-up were evaluated. One-hundred and thirty-two knees of 114 patients were included in the final analysis. The clinical evaluation included range of motion and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Anatomical femorotibial angle (aFTA), anatomical medial proximal tibial angle (aMPTA), tibial slope and Insall-Salvati ratio were calculated on standard weight-bearing radiographs.

RESULTS

The average aFTA was improved from 1.6° varus to 8.7° valgus (P < 0.001). The average WOMAC score (P < 0.001) and flexion value (P = 0.014) were improved at the latest follow-up (WOMAC: 17.2, flexion: 142.5) compared with the preoperative period (WOMAC: 59.6, flexion: 129.2). The sagittal radiological parameters were not significantly affected. The five-year survival was 96.2%, and 10-year survival was 83.3%.

CONCLUSIONS

The semi-circular Ilizarov pin construct provided satisfactory outcomes both clinically and radiologically at mid- to long-term follow-up.

Factors related to femoral bowing among Korean female farmers: a cross-sectional study

Background

Female farmers have a high prevalence of knee osteoarthritis (KOA) in South Korea. Femoral bowing has been reported to be related to KOA by increasing load on the mechanical axis. This study aimed to investigate factors related to femoral bowing in Korean female farmers.

Methods

We analyzed the legs of 264 female farmers registered with the Korea farmers' knee cohort of Jeonnam Center for Farmers' Safety and Health. A structured questionnaire was used to determine sociodemographic variables, agricultural career, cumulative squatting working time (CSWT), and cumulative heavy lifting working time. Femoral bone density was measured and Kellgren-Lawrence (KL) grades were obtained from the knee radiographs. Mechanical axis angle (MAA), femoral bowing angle (FBA), anatomical lateral distal femoral angle (aLDFA), anatomical medial proximal tibial angle (aMPTA), and condylar-plateau angle (CPA) were measured. We examined the relationship between the FBA and related factors by using multiple linear regression.

Results

The proportion of individuals with radiographic KOA (≥ KL grade 2) in this study was 37.9%. As KL grades increased, MAA, FBA, and CPA increased, whereas aLDFA and aMPTA decreased. FBA increased with age. Multiple linear regression analyses using FBA as a dependent variable showed relationship with higher age, lower height, higher BMI, lower bone mineral density, longer CSWT, and longer agricultural careers.

Conclusions

The results of this study suggest that external factors related to agricultural work in female farmers was associated with femoral bowing, in addition to internal factors such as age, bone density, height, and obesity.

Anatomical axis validation of lower extremity for different deformities: A radiological study

Aim:

The aim of this study was to derive a pure, unbiased, reliable and accurate objective relationship between the local knee axis measurements through a short knee anteroposterior roentgenogram and the lower limb axis measurement through an orthoroentgenogram.

Patients and Methods:

Radiographs of 114 patients (114 knees) were evaluated by two independent raters for measurement of lower limb axis on an orthoroentgenogram and the local knee axis on short knee anteroposterior X-ray, which was derived by cropping the orthoroentgenogram by a blinded radiology assistant. The raters measured at two different time-points separated by an interval of 30-day period. Intra-rater and inter-rater reliabilities were calculated by intra-class correlation coefficients and three models were built to establish the relationships of X-ray anatomical axis with orthoroentgenogram anatomical axis, orthoroentgenogram anatomical axis with orthoroentgenogram mechanical axis and X-ray anatomical axis with orthoroentgenogram mechanical axis.

Results:

For three different measurements, intra-class correlation coefficients of Rater 2 were higher than 0.90 which shows perfect reliability, while that for Rater 1 was low. Furthermore, first measurements were more consistent than the second measurement. There was a strong positive correlation in all the three models except for varus cases in the last.

Conclusion:

The standardized correlation derived between the two different techniques for measuring knee alignment is fairly comparable with the studies in the past and would serve as a reliable template for future studies concerning relationships between the two, in addition to helping knee surgeons make more reliable and accurate interpretations through local knee axis measurements.

The entry point of intramedullary tibia cutting guide should vary according to the individual tibia morphology in TKA

INTRODUCTION

In total knee arthroplasty (TKA) using the intramedullary tibial cutting guide (IMTCG), the positioning of the IMTCG is important for accurate tibial bone resection. The aim of this study was to evaluate the ideal entry point of IMTCG and affecting radiologic factors.

MATERIALS AND METHODS

From May 2017 to February 2018, 91 consecutive TKAs for osteoarthritis were included. From preoperative full-length radiographs, we measured the medial proximal tibia angle (MPTA), lateral distal tibia angle (LDTA), tibial bowing angle (TBA), medial to lateral width of the tibial plateau, tibial length, and ideal coronal entry point. In preoperative short knee lateral radiographs, we measured the anterior to posterior length of the tibial plateau, tibial posterior slope angle (TPSA), metaphysio-diaphyseal angle (MDA), and ideal sagittal entry point. The ideal coronal and sagittal entry points were defined as the points crossing the tibial plateau and tibial anatomical axis on the coronal and sagittal radiographs, respectively.

RESULTS

The ideal entry point was 51.4 ± 4.3% (SD) from the medial margin and 27.0 ± 5.8% (SD) from the anterior margin of the tibial plateau. However, the range varied from 39.8 to 60.5% on the coronal plane and from 9.6 to 37.7% on the sagittal plane, respectively. As the MPTA (rho = - 0.490) and TBA (rho = - 0.433) were increased, the coronal entry point moved medially. As TPSA (rho = - 0.761) and MDA (rho = - 0.495) were increased, the sagittal entry point moved anteriorly.

CONCLUSIONS

The ideal entry point of IMTCG should vary according to the individual tibial morphology.

Short knee radiographs can be inadequate for estimating TKA alignment in knees with bowing

Purpose

The aim of this study was to compare the discrepancy of alignment categorization in total knee arthroplasty (TKA) between the anatomical femorotibial angle (aFTA) measured on short knee radiographs and the mechanical hip–knee–ankle axis angle (mHKA) measured on full-length radiographs in knees with and without bowing.

Methods

From January 2014 to June 2017, 107 of 526 osteoarthritic knees at our hospital were found to have femoral or tibial bowing. Bowing was defined as a femoral bowing angle (FBA) > 3° or < − 3° or a tibial bowing angle (TBA) > 2° or < − 2° in full-length preoperative radiographs. Among 419 knees without bowing, we selected 107 knees as a control group using propensity-score matching. Postoperative alignments were categorized by aFTA in short knee radiographs and mHKA in full-length radiographs into neutral (2° ≤ aFTA≤7°, − 3° ≤ mHKA≤3°), varus (aFTA< 2°, mHKA<− 3°), and valgus (aFTA> 7°, mHKA> 3°) alignments. We compared the categorization of alignments between knees with and without bowing using the McNemar test and used logistic regression to find factors for the alignment discordance.

Results

Coronal alignment was discordant in 26.2% of the knees with bowing and 13.1% of the knees without bowing (p < 0.001). FBAs were a significant factor affecting the discordance of alignment categorization (OR = 1.152, 95%CI 1.038–1.279, p = 0.008).

Conclusion

Short knee radiographs are insufficient for estimating coronal alignment after TKA, particularly in knees with femoral bowing.

Level of evidence: III

Retrospective comparative study.

Accuracy of tibial positioning in the frontal plane: a prospective study comparing conventional and innovative techniques in total knee arthroplasty

BACKGROUND

Coronal alignment of the tibial component determines functional outcome and survival in total knee arthroplasty (TKA). Innovative techniques for tibial instrumentation have been developed to improve accuracy and reduce the rate of outliers.

METHODS

In a prospective study, 300 patients were allocated to four different groups using a randomization process (two innovative and two conventional) techniques of tibial instrumentation (conventional: extramedullary, intramedullary; innovative: navigation and patient-specific instrumentation (PSI); n = 75 for each group). The aims were to reconstruct the medial proximal tibial angle (MPTA) to 90° and the mechanical tibio-femoral axis (mTFA) to 0°. Both angles were evaluated and compared between all groups three months after the surgery. Patients who presented with a postoperative mTFA > 3° were classified as outliers.

RESULTS

The navigation and intramedullary technique both demonstrated that they were significantly more precise in reconstructing a neutral mTFA and MPTA compared to the other two techniques. The odd's ratio (OR) for producing outliers was highest for the PSI method (PSI OR = 5.5, p < 0.05; extramedullary positioning OR = 3.7, p > 0.05; intramedullary positioning OR = 1.7, p > 0.05; navigation OR = 0.04, p < 0.05). We could only observe significant differences between pre- and postoperative MPTA in the navigation and intramedullary group. The MPTA showed a significant negative correlation with the mTFA in all groups preoperatively and in the extramedullary, intramedullary and PSI postoperatively.

CONCLUSION

The navigation and intramedullary instrumentation provided the precise positioning of the tibial component. Outliers were most common within the PSI and extramedullary technique. Optimal alignment is dependent on the technique of tibial instrumentation and tibial component positioning determines the accuracy in TKA since mTFA correlated with MPTA pre- and postoperatively.

Variation of three-dimensional femoral bowing and its relation to physical status and bone mineral density: a study with CT

PURPOSE

Anatomically, the femoral bone shows sagittal and coronal bowing. Pronounced bowing would affect femoral implant surgery accuracy, but factors associated with degrees of three-dimensional (3D) femoral bowing have not yet been identified. This study measured 3D femoral bowing and examined the correlation between 3D femoral bowing and risk factors.

METHODS

3D femoral bone models of unaffected legs from 125 patients were reconstructed from computed tomography data. A trans-epicondylar axis (TEA)-based coordinate system was introduced into bone models and the reproducibility of this coordinate system was evaluated. The cross-sectional contours of the femoral canal were extracted along the vertical axis of the TEA-based coordinate system, and the angles of 3D femoral bowing were examined.

RESULTS

The reproducibility to set the coordinate was very high. Total, sagittal, and coronal femoral bowing were 8.9 ± 1.8°, 8.7 ± 1.8°, and 0.1 ± 1.9°, respectively. There was no significant difference in the degrees of femoral bowing between males and females. Total, coronal, and sagittal femoral bowing correlated with age, height, and femoral length, but only femoral coronal bowing correlated with bone mineral density (BMD) of the femur and lumbar spine.

CONCLUSIONS

We introduced a highly reproducible method for measuring femoral sagittal and coronal bowing by constructing a femoral 3D coordinate system. Anterior femoral bowing was the dominant direction of bowing in our Japanese cohort, whereas the degree of lateral bowing correlated with age, height, femoral length, and BMD. Our results suggest that lateral femoral bowing could increase with aging and decreasing BMD.

Association between bone mineral density distribution and various radiographic parameters in patients with advanced medial osteoarthritis of the knee

PURPOSE

Patients with severe osteoarthritis (OA) of the knee have changes in bone mineral density (BMD) of the distal femur and proximal tibia. Correlations between the medial-to-lateral BMD (M/L-BMD) ratio (which normalizes the potentially confounding effects of body size and sex on BMD) and radiographic parameters that indicate OA progression have not been adequately studied. The purpose of this study was to evaluate correlations between radiographic indicators of OA progression and femoral and tibial M/L-BMD ratios.

METHODS

A consecutive series of 182 knees in 156 patients with advanced medial knee OA who underwent total knee arthroplasty were included. We evaluated correlations between the femoral and tibial M/L-BMD ratios and various radiographic parameters, including tibiofemoral angle (TFA), mechanical axis angle (MAA), tibial coronal angle, tibiofemoral subluxation (%), load-bearing axis deviation at the tibial plateau (%), and medial and lateral laxity.

RESULTS

Univariate analyses using Spearman's correlation coefficient revealed significant positive correlations between femoral and tibial M/L-BMD ratios and both TFA and MAA and negative correlations with tibial coronal angle and load-bearing axis deviation. Multivariate analyses showed significant associations between TFA and the femoral M/L-BMD ratio (β = 0.434, p < 0.001) and between MAA and the tibial M/L-BMD ratio (β = 0.384, p < 0.001).

CONCLUSION

BMD distribution around the knee might be predictable with radiographic parameters such as the TFA for the femur and MAA for the tibia. The findings of this study provide in vivo data on the evaluation of preoperative femoral and tibial M/L-BMD ratios without dual-energy X-ray absorptiometry.

Fixed Distal Femoral Cut of 6° Valgus in Total Knee Arthroplasty: A Radiographic Review of 788 Consecutive Cases

BACKGROUND

In place of the mechanical axis (MA), the use of the variable tibiofemoral angle is frequently used to plan measured resection bony cuts during total knee arthroplasty (TKA). This angle, coupled with operator-dependent variability of intramedullary distal femoral cutting guides, has the potential for catastrophic outcomes. Therefore, a simpler, fixed femoral cut of 6° valgus may be more appropriate when direct measurement of the MA is not possible.

METHODS

This was a retrospective study of 788 consecutive TKAs, in which the distal femoral cut was set to 6° valgus. The preoperative and 6-week postoperative MA were measured on hip-to-ankle radiographs. Data were evaluated as a group as well as grouped by preoperative deformity (MA < -3°, -3° < MA < 3°, 3° < MA).

RESULTS

Following TKA, MA alignment for all patients was 0.0° ± 2.3° (range, -7.0° to 8.0°). When grouped by pre-TKA alignment, 548 patients were considered varus (MA < -3°), 137 were neutral (-3° < MA < 3°), and 103 patients were valgus (3° < MA). When evaluating the post-TKA alignment achieved in the 3 groups, neutral alignment (-3° < MA < 3°) was established in 86.5% of varus patients, 86.1% of neutral patients, and 82.5% of valgus patients.

CONCLUSION

A standard distal femoral cut of 6° resulted in a neutral MA in 86% of patients. While no single technique will be correct for all deformities, in the absence of sophisticated preoperative planning aids, this simple technique could provide a more reliable surgical technique than the measured tibiofemoral angle.

Predictive factors for satisfaction after contemporary unicompartmental knee arthroplasty and high tibial osteotomy in isolated medial femorotibial osteoarthritis

INTRODUCTION

Both high tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) are viable treatment options for early osteoarthritis (OA). Although a substantial proportion of the patient selection criteria for HTO and UKA are now shared, the factors related to satisfaction following each procedure remain unclear.

HYPOTHESIS

We hypothesized that patient factors associated with satisfaction following contemporary HTO and UKA would be different.

MATERIAL AND METHODS

We retrospectively reviewed the records of consecutively enrolled medial opening-wedge HTOs (n=123) and Oxford mobile-bearing UKAs (n=118) with satisfactory postoperative alignment. Preoperative demographics, physical activity levels, varus deformity status, and degree of OA were recorded. Postoperative radiographs, frequency of combined procedures and patient-reported outcomes (PROs) including pain, Western Ontario and McMaster Universities Osteoarthritis Index score, and patient satisfaction were assessed.

RESULTS

Severe OA (p<0.01) was associated with an increased risk of dissatisfaction following HTO, whereas young age (p<0.01) and severe varus deformity (p=0.045) were related to dissatisfaction after UKA. In addition, patient satisfaction following UKA was higher than that following HTO in individuals with highly physically demanding activity. All UKA PROs were superior to those of the HTO group, except pain level.

CONCLUSION

Despite the shared patient selection criteria for contemporary HTO and UKA, severe OA was associated with dissatisfaction following HTO, whereas young age and varus deformity were associated with dissatisfaction following UKA. Age, varus deformity and OA severity should be considered when deciding whether to perform HTO or UKA.

TYPE OF STUDY AND LEVEL OF PROOF

Retrospective cohort study, Level III.

Is Regular Knee Radiograph Reliable Enough to Assess the Knee Prosthesis Position?

BACKGROUND

Proper knee alignment and prosthesis position may theoretically provide better surgical results and increase longevity of total knee arthroplasty. The 3-feet standing long radiograph (LR) is the gold standard for assessment of these parameters. However, the conventional standing regular knee radiograph (RR) is still being used because of convenience and lower cost. We conducted a study to investigate the accuracy of RR compared to LR in assessing the coronal plane prosthesis position.

METHODS

We conducted a retrospective cross-sectional study in 100 knee radiographs in 88 patients with knee prostheses. The picture archiving and communications system was used to produce digitized radiographs and perform the angle measurements. LR images were cropped to the same size as the RRs to eradicate rotation error. The femoral component angle (FCA), tibial component angle (TCA), and tibiofemoral angle (TFA) were measured and analyzed by Student t-test. Pearson's correlation coefficient was used to assess interobserver and intraobserver reliability.

RESULTS

The RR measurements resulted in a mean increment of 1.3° (95% confidence interval [CI], 0.9°-1.6°; P < .001) for FCA and 1.4° (95% CI, 1.0°-1.9°; P < .001) for TFA compared to LR. The TCAs were similar between 2 techniques (0.2° mean difference; 95% CI, 0°-0.4°; P = .11). RR provided very strong intraobserver reproducibility but only strong interobserver reliability for FCA and TCA while LR provided very strong correlation for all angles.

CONCLUSION

RR overestimation of FCA and TFAs in a valgus alignment was minimal, suggesting RR could be an acceptable alternative to LR.

Femoral Component Varus Malposition is Associated with Tibial Aseptic Loosening After TKA

BACKGROUND

The notion that neutral alignment is mandatory to assure long-term durability after TKA has been based mostly on short-film studies. However, this is challenged by recent long-film studies.

QUESTIONS/PURPOSES

We conducted this long-film study to know (1) whether the risk of aseptic revision for nontraumatic reasons was greater among knees with greater than 3° varus or valgus (defined as "outliers") than those that were aligned within 3° of neutral on long-standing mechanical axis (hip to knee) radiographs; and (2) what the failure mechanisms were and whether the malalignment was femoral or tibial in origin, or both, among those in the outlier group.

METHODS

Between November 1998 and January 2009 we performed 1299 cemented, posterior cruciate ligament-substituting TKAs in 867 patients for primary osteoarthritis. We had inadequate long-standing radiographs to analyze postoperative alignment for 124 of those knees, and an additional 24 were excluded for prespecified reasons. Consequently, 1151 knees were enrolled in our study. Of these, 982 (85%) in 661 patients (620 women and 41 men) who had followup greater than 24 months were analyzed. The knees were divided according to whether the postoperative mechanical axis was neutral (0° ± 3°), varus (> 3°), or valgus (< -3°) alignment on long-standing radiographs. The survivorships free from aseptic revision for nontraumatic reasons were compared among groups. The mechanical femoral and the tibial component alignment (MFCA and MTCA, respectively) were investigated to know the origin of overall mechanical malalignment of the outlier knees. The mean duration of followup was 8 ± 4 years (range, 2-17 years). Thirty-five knees (4%) showed aseptic loosening at 7 ± 4 years (range, 0.1-14 years) and five (1%) showed polyethylene wear at 12 ± 1 years (range, 10-13 years). Tibial loosening (73%) was the most common reason for aseptic revision followed by femoral loosening (30%). Of this cohort, 687 (70%), 250 (25%), and 45 (5%) knees had overall mechanical neutral, varus, and valgus alignment, respectively. Factors associated with the risk of aseptic revision were identified by Cox regression.

RESULTS

The varus outliers (but not the valgus outliers) failed more often than the neutral knees (10% [25 of 250] versus 2% [13 of 687]; odds ratio [OR], 5.8, 95% CI, 2.9-11.5; p < 0.001). Ten-year survivorship free from aseptic revision was lower among varus outliers than among knees with neutral alignment (87% [95% CI, 80%-93%] versus 98% [95% CI, 97%-99%]; p = 0.001). Femoral component varus malpositioning was the main origin of the varus outliers (MFCA = 4.2° ± 2.0°; MTCA = 0.9° ± 1.7°) and was a risk factor for aseptic revision compared with neutral femoral positioning (OR, 14.0; 95% CI, 1.9-105.6; p < 0.001).

CONCLUSIONS

This long-film study corresponds to previous short-film studies for the notion that varus malalignment is associated with inferior long-term implant survivorship. Although aseptic loosening occurred most commonly on the tibial side, the primary origin of the overall varus malalignment was femoral component varus malpositioning. Aiming for neutral alignment in TKA still seems to be a reasonable strategy in clinical practice.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Annual trends in knee arthroplasty and tibial osteotomy: Analysis of a national database in Japan

BACKGROUND

Various nationwide studies have reported differing annual trends in utilization of knee arthroplasty and tibial osteotomy. Using the Diagnosis Procedure Combination database in Japan, the present series examined annual trends and demographics in total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA) and tibial osteotomy.

METHODS

All patients were identified who underwent TKA, UKA or tibial osteotomy for osteoarthritis, osteonecrosis or rheumatoid arthritis of the knee between July 2007 and March 2015.

RESULTS

A total of 170,433 cases of TKA, 13,209 cases of UKA and 8760 cases of tibial osteotomy were identified. The proportion of patients undergoing UKA rose from 4.0% in 2007 to 8.1% in 2014 (P<0.001), and that of tibial osteotomy from 2.6% in 2007 to 5.5% in 2014 (P<0.001); the proportion undergoing TKA fell from 93.4% in 2007 to 86.3% in 2014 (P<0.001). Between 2007 and 2014 the proportions of patients with osteonecrosis who underwent UKA and tibial osteotomy increased from 34.7% and 11.6% to 38.6% and 16.2%, respectively (P=0.001 for UKA and P=0.004 for tibial osteotomy). The proportions of patients with osteonecrosis undergoing UKA or tibial osteotomy were significantly greater than those with other diagnoses (P<0.001 for both).

CONCLUSIONS

The popularity of UKA and tibial osteotomy in Japan increased during the period 2007-2014 at the expense of TKA. The proportions of UKA and tibial osteotomy in patients with osteonecrosis also increased, and were larger than those in patients with other causative diseases.

[Should we use hip-ankle radiographs to assess the coronal alignment after total knee arthroplasty?]

BACKGROUND

There is no consensus on whether hip-ankle radiographs or rather standardized a‑p knee-radiographs should be used to assess implant position and coronal alignment after total knee arthroplasty (TKA). This study investigates whether implant position and alignment after TKA can reproducibly be assessed using a‑p knee-radiographs rather than hip-ankle radiographs.

MATERIALS AND METHODS

This study was performed on 100 weight-bearing hip-ankle radiographs after conventional primary TKA. The true mechanical and anatomical femorotibial angle as well as coronal implant position was assessed on hip-ankle radiographs. The radiographs were then cropped to 80, 60 and 40 % of the leg-length and tibial coronal implant position, and the anatomical axis and a surrogate mechanical axis were obtained. The difference in the alignment parameters between the hip-ankle radiographs were statistically compared with the cropped radiographs and the inter-observer correlation coefficient (ICC) was calculated.

RESULTS

The ICC for measurement of the mechanical femorotibial angle was higher in hip-ankle radiographs (0.95) when compared with a radiograph cropped to 40 % (0.61). There was a significant difference in the mechanical femorotibial angle between hip-ankle radiographs and any cropped radiograph. However, there were no significant differences in coronal implant position and the anatomical femorotibial angle between hip-ankle radiographs and any cropped radiograph.

CONCLUSIONS

We conclude that standard a‑p knee-radiographs are insufficient to assess the mechanical alignment following TKA. However, standard a‑p knee-radiographs are appropriate to assess the implant position when referenced against the anatomical axes. Weight-bearing hip-ankle radiographs should be questioned as a routine after TKA.

Standard Radiographs Are Not Sufficient for Assessing Knee Mechanical Axis in Patients With Advanced Osteoarthritis

BACKGROUND

The use of standard radiographs, and measured tibiofemoral angle (TFA), to assess lower extremity alignment is commonly practiced despite limited knowledge of its relationship to the mechanical axis (MA), as measured on hip-to-ankle (HTA) radiographs. This study assessed the predictive accuracy of previously developed equations, developed gender-specific regression equations using predictors from standard radiographs, and the clinical effectiveness of these equations in a large sample of cases using HTA radiographs as a gold standard.

METHODS

The MA was measured on HTA radiographs, whereas TFA and femoral angle were measured on standard radiographs in 788 cases diagnosed with knee osteoarthritis.

RESULTS

Multiple regression analyses indicated that TFA, femoral angle, and height were the strongest factors associated with the predicting MA, accounting for 83% of the variance for men and 86% for women, but were able to predict only the actual MA within ±3° in 66% of men and 69% of women. When applied to previously reported regression equations with similar results, the best predicative accuracy obtained within ±3° was 61% and 63% of men and women, respectively.

CONCLUSION

Standard radiographs are not sufficient for determining MA, and HTA radiographs should be used while making surgical decisions aimed at correcting alignment to within ±3° or for assessing alignment post-total knee arthroplasty. In addition, surgical alignment outcomes reported in previous research using standard radiographs should be viewed with caution.

Semimembranosus Release for Medial Soft Tissue Balancing Does Not Weaken Knee Flexion Strength in Patients Undergoing Varus Total Knee Arthroplasty

BACKGROUND

The sequential medial release technique including semimembranosus (semiM) release is effective and safe during varus total knee arthroplasty (TKA). However, there are concerns about weakening of knee flexion strength after semiM release. We determined whether semiM release to balance the medial soft tissue decreased knee flexion strength after TKA.

METHODS

Fifty-nine consecutive varus knees undergoing TKA were prospectively enrolled. A 3-step sequential release protocol which consisted of release of (1) the deep medial collateral ligament (dMCL), (2) the semiM, and (3) the superficial medial collateral ligament based on medial tightness. Gap balancing was obtained after dMCL release in 31 knees. However, 28 knees required semiM release or more after dMCL release. Isometric muscle strength of the knee was compared 6 months postoperatively between the semiM release and semiM nonrelease groups. Knee stability and clinical outcomes were also compared.

RESULTS

No differences in knee flexor or extensor peak torque were observed between the groups 6 months postoperatively (P = .322 and P = .383, respectively). No group difference was observed in medial joint opening angle on valgus stress radiographs (P = .327). No differences in the Knee Society or Western Ontario and McMaster Universities Osteoarthritis Index scores were detected between the groups (P = .840 and P = .682, respectively).

CONCLUSION

These results demonstrate that semiM release as a sequential step to balance medial soft tissue in varus knees did not affect knee flexion strength after TKA.

Inter-observer variability and its correlation to experience in measurement of lower limb mechanical axis on long leg radiographs

INTRODUCTION

Restoration of mechanical axis (MA) is one of the most important aims of treatment of knee arthritis. The measurement of MA is often done on hip knee ankle (HKA) radiographs (LLR), but its measurement is often difficult and variable. We studied to check if inter-observer variability in the measurement of MA is dependent on the experience of the observer.

MATERIALS AND METHODS

48 patients (70 knees) underwent measurement of MA on HKA radiographs. The measurement was done by five observers of different experience. All the results were tested for inter-observer variability.

RESULTS

The overall intra-class correlation was 0.70. The two full time consultants had good agreeability among them (p < 0.456). All the surgeons who had less than five years of experience among them also had good agreeability amongst them (all p values >0.005). All the other groups (except senior consultant and senior registrar) had statistically significant difference amongst them (all p values <0.005).

CONCLUSION

There is an inter-observer variability in the measurement of MA on the HKA radiographs. The agreeability between the observers increases as the experience of the personnel increases. Although long leg radiographs can be used for assessment for HKA, this variability should be kept in mind while using this as a tool for planning management of the arthritic knee.

A comparison of radiographic anatomic axis knee alignment measurements and cross-sectional associations with knee osteoarthritis

OBJECTIVE

Malalignment is associated with knee osteoarthritis (KOA), however, the optimal anatomic axis (AA) knee alignment measurement on a standard limb radiograph (SLR) is unknown. This study compares one-point (1P) and two-point (2P) AA methods using three knee joint centre locations and examines cross-sectional associations with symptomatic radiographic knee osteoarthritis (SRKOA), radiographic knee osteoarthritis (RKOA) and knee pain.

METHODS

AA alignment was measured six different ways using the KneeMorf software on 1058 SLRs from 584 women in the Chingford Study. Cross-sectional associations with principal outcome SRKOA combined with greatest reproducibility determined the optimal 1P and 2P AA method. Appropriate varus/neutral/valgus alignment categories were established using logistic regression with generalised estimating equation models fitted with restricted cubic spline function.

RESULTS

The tibial plateau centre displayed greatest reproducibility and associations with SRKOA. As mean 1P and 2P values differed by >2°, new alignment categories were generated for 1P: varus <178°, neutral 178-182°, valgus >182° and for 2P methods: varus <180°, neutral 180-185°, valgus >185°. Varus vs neutral alignment was associated with a near 2-fold increase in SRKOA and RKOA, and valgus vs neutral for RKOA using 2P method. Nonsignificant associations were seen for 1P method for SRKOA, RKOA and knee pain.

CONCLUSIONS

AA alignment was associated with SRKOA and the tibial plateau centre had the strongest association. Differences in AA alignment when 1P vs 2P methods were compared indicated bespoke alignment categories were necessary. Further replication and validation with mechanical axis alignment comparison is required.

Using the Anatomical Axis as an Alternative to the Mechanical Axis to Assess Knee Alignment

The treatment of knee osteoarthritis and the preparation for total knee arthroplasty require repetitive imaging to guide preoperative planning and operative technique. Full-length standing anteroposterior images are the gold standard in assessing the alignment of the limb via the measurement of the mechanical axis of the knee. The anatomical axis can be obtained from a more limited image of the knee, and as such is less expensive and exposes the patient to less ionizing radiation. The objective of this cross-sectional prospective study was to examine the extent to which the anatomical axis measured on a fixed-flexed posteroanterior (Rosenberg view) radiograph correlates with the mechanical axis. The data of 209 total knee arthroplasty radiographs were analyzed to compare the preoperative correlation between the mechanical and anatomical axis. The anatomical axis correlated with the mechanical axis when it was measured from both the standing full-length anteroposterior radiograph and from a fixed-flexed posteroanterior radiograph. Using an angle of offset found from linear regression, these correlations become closer. Body mass index and Kellgren-Lawrence grade were not found to have a significant effect. It is the conclusion of this study that the anatomical axis, as measured from a limited knee radiography, may serve as a plausible estimate of the mechanical axis when done with a neutral angle of offset, and that offset angle depends on gender and the imaging technique used to determine the anatomical axis.

Atypical fractures of the femur: effect of anterolateral bowing of the femur on fracture location

INTRODUCTION

Bisphosphonate therapy has been associated with the development of atypical femoral fractures. The most common sites of bisphosphonate-associated fractures are at the subtrochanteric region followed by the femoral shaft. This retrospective study hypothesizes that increasing anterolateral femoral bow is associated with more distal diaphyseal fractures. Awareness of this relationship is essential in the pre-operative planning and successful surgical management of these fractures.

MATERIALS AND METHODS

We retrospectively reviewed twenty-one atypical subtrochanteric and femoral diaphyseal fractures and stress reactions within a 5-year period at our institution. Radiographs were assessed by two independent investigators for the degree of anterior and lateral femoral bow, and how distal the fracture was from the lesser trochanter. The relationship between the fracture position or stress reaction and degree of anterior and lateral bowing was analysed.

RESULTS

There was a statistically significant linear relationship between anterior and lateral femoral bowing, and the fracture position along the diaphysis (correlation coefficient 0.63 (p = 0.002) and 0.684 (p = 0.001), respectively). Inter-observer reliability was highly correlated (Kappa value >0.8).

CONCLUSION

In atypical femoral fractures associated with bisphosphonate use, more distal diaphyseal fractures occurred with a higher degree of anterior and lateral femoral bow.

How accurate is anatomic limb alignment in predicting mechanical limb alignment after total knee arthroplasty?

BACKGROUND

Anatomic limb alignment often differs from mechanical limb alignment after total knee arthroplasty (TKA). We sought to assess the accuracy, specificity, and sensitivity for each of three commonly used ranges for anatomic limb alignment (3-9°, 5-10° and 2-10°) in predicting an acceptable range (neutral ± 3°) for mechanical limb alignment after TKA. We also assessed whether the accuracy of anatomic limb alignment was affected by anatomic variation.

METHODS

This retrospective study included 314 primary TKAs. The alignment of the limb was measured with both anatomic and mechanical methods of measurement. We also measured anatomic variation, including the femoral bowing angle, tibial bowing angle, and neck-shaft angle of the femur. All angles were measured on the same full-length standing anteroposterior radiographs. The accuracy, specificity, and sensitivity for each range of anatomic limb alignment were calculated and compared using mechanical limb alignment as the reference standard. The associations between the accuracy of anatomic limb alignment and anatomic variation were also determined.

RESULTS

The range of 2-10° for anatomic limb alignment showed the highest accuracy, but it was only 73 % (3-9°, 65 %; 5-10°, 67 %). The specificity of the 2-10° range was 81 %, which was higher than that of the other ranges (3-9°, 69 %; 5-10°, 67 %). However, the sensitivity of the 2-10° range to predict varus malalignment was only 16 % (3-9°, 35 %; 5-10°, 68 %). In addition, the sensitivity of the 2-10° range to predict valgus malalignment was only 43 % (3-9°, 71 %; 5-10°, 43 %). The accuracy of anatomical limb alignment was lower for knees with greater femoral (odds ratio = 1.2) and tibial (odds ratio = 1.2) bowing.

CONCLUSIONS

Anatomic limb alignment did not accurately predict mechanical limb alignment after TKA, and its accuracy was affected by anatomic variation. Thus, alignment after TKA should be assessed by measuring mechanical alignment rather than anatomic alignment.

Radiographic assessment of leg alignment and grading of knee osteoarthritis: A critical review

Knee osteoarthritis (OA) is a progressive joint disease hallmarked by cartilage and bone breakdown and associated with changes to all of the tissues in the joint, ultimately causing pain, stiffness, deformity and disability in many people. Radiographs are commonly used for the clinical assessment of knee OA incidence and progression, and to assess for risk factors. One risk factor for the incidence and progression of knee OA is malalignment of the lower extremities (LE). The hip-knee-ankle (HKA) angle, assessed from a full-length LE radiograph, is ideally used to assess LE alignment. Careful attention to LE positioning is necessary to obtain the most accurate measurement of the HKA angle. Since full-length LE radiographs are not always available, the femoral shaft - tibial shaft (FS-TS) angle may be calculated from a knee radiograph instead. However, the FS-TS angle is more variable than the HKA angle and it should be used with caution. Knee radiographs are used to assess the severity of knee OA and its progression. There are three types of ordinal grading scales for knee OA: global, composite and individual feature scales. Each grade on a global scale describes one or more features of knee OA. The entire description must be met for a specific grade to be assigned. The Kellgren-Lawrence scale is the most commonly-used global scale. Composite scales grade several features of knee OA individually and sum the grades to create a total score. One example is the compartmental grading scale for knee OA. Composite scales can respond to change in a variety of presentations of knee OA. Individual feature scales assess one or more OA features individually and do not calculate a total score. They are most often used to monitor change in one OA feature, commonly joint space narrowing. The most commonly-used individual feature scale is the OA Research Society International atlas. Each type of scale has its advantages; however, composite scales may offer greater content validity. Responsiveness to change is unknown for most scales and deserves further evaluation.

Femoral shaft bowing in the coronal plane has more significant effect on the coronal alignment of TKA than proximal or distal variations of femoral shape

PURPOSE

The aim of this study was to determine (1) variations in the shape of the proximal, middle, and distal femur in a series of Korean patients who had undergone total knee arthroplasty (TKA), (2) the preoperative relationship between these three parameters and the distal valgus cutting angle referenced off the femoral intramedullary guide, and (3) whether there was any relationship between femoral bowing and variations in the shape of the proximal or distal femur in the coronal plane.

METHODS

The preoperative long-standing anteroposterior radiographs of 316 consecutive osteoarthritis patients who underwent primary TKA from 2009 to 2011 were examined. The femoral neck shaft angle, the femoral shaft bowing angle, and the mechanical lateral distal femoral angle were measured to assess the shape of the proximal, middle, and distal femur, respectively. The valgus cutting angle of the femur was defined as the angle between the distal anatomical and mechanical axes of the femur.

RESULTS

The study population showed large variations in femoral shape. The mean femoral intramedullary guide angle was 6.5° ± 1.3° (range: 4°-13°). The femoral shaft bowing angle was the factor that showed the strongest correlation with this angle (P < 0.001). The mechanical lateral distal femoral angle showed only a weak correlation (P = 0.001), and the femoral neck shaft angle showed no correlation (n.s.). The femoral shaft bowing angle showed a weak correlation with the mechanical lateral distal femoral angle (P = 0.001), but was not significantly correlated with the femoral neck shaft angle (n.s.). Apparent femoral bowing (>3° of lateral or medial bowing) was found in 42 (13.3 %) of cases (37 cases of lateral bowing and five of medial bowing). Cases with lateral apparent femoral bowing >3° had a distal cutting angle of 8.6° ± 2.2° relative to the femoral intramedullary guide.

CONCLUSION

The femoral intramedullary guide angle was mainly influenced by femoral shaft bowing among femoral deformities in the coronal plane. Therefore, to increase the accuracy of distal femoral cut during TKA, it is necessary to confirm femoral deformities and to measure the femoral intramedullary guide angle preoperatively from coronal radiographs covering the whole femur.

LEVEL OF EVIDENCE

IV.

Trends in High Tibial Osteotomy and Knee Arthroplasty Utilizations and Demographics in Korea From 2009 to 2013

We analyzed the records of 29,895 high tibial osteotomies (HTOs), 12,589 unicompartmental knee arthroplasties (UKAs) and 363,386 total knee arthroplasties (TKAs) performed from 2009 to 2013 in Korea. They were compared with the latest nationwide registry reports of seven Western countries. Over the last 5 years, in Korea, the number of HTO, UKA and TKA increased by 210%, 138%, and 18%, respectively. The largest increase was observed in 55-64 year olds in HTO and UKA, while the largest increase in TKA was in ≥75 year olds. Females commonly had a three- to seven-fold higher rate in all procedures. Worldwide, the use of HTO and UKA decreased or remained stable, whereas that of TKA increased steadily, even in younger patients.

A radiographic analysis of alignment of the lower extremities--initiation and progression of varus-type knee osteoarthritis

OBJECTIVE

This study aimed to investigate alignment based on age in normal knees and alignment based on deformity in osteoarthritis (OA) knees using detailed radiographic parameters.

DESIGN

Various parameters were measured from weight-bearing long leg radiographs of 1251 legs (797 normal and 454 OA knees) as a cross-sectional study. Normal knees were classified by age (young, middle aged, aged, and elderly) and symptomatic OA knees on the basis of the alignment (femorotibial angle (FTA): mild, moderate, severe and profound). The mean measurements in each group were calculated and compared within each group.

RESULTS

The femoral shaft showed medially bowed curvature (femoral bowing) of approximately 2° in the young normal group, which shifted to lateral bowing with age. However, OA knees showed larger lateral bowing with OA grade, which might reduce the condylar-shaft angle and subsequently shifted the mechanical axis medially. Progression of mild to moderate OA might be associated with a decreasing condylar-shaft angle (femoral condylar orientation) and widening condylar-plateau angle (joint space narrowing) rather than decreasing tibial plateau flattering. Steeping of the tibial plateau inclination due to increasing tibial plateau shift (tibial plateau compression) rather than medial tibial bowing might be the main contributor to worsening of varus deformity in knees with severe and profound OA.

CONCLUSIONS

This cross-sectional study might provide the possibility of OA initiation and progression. The lateral curvature of the femoral shaft associated with aging may contribute to the initiation of varus-type OA of the knee. These changes in the femur may be followed by secondary signs of OA progression including varus femoral condylar orientation, medial joint space narrowing, and tibial plateau compression.

Changes of knee joint and ankle joint orientations after high tibial osteotomy

OBJECTIVE

We sought to determine (1) whether change in the tibial plateau inclination (TPI) after high tibial osteotomy (HTO) is different from change in the knee joint line orientation (KJLO) relative to the ground; (2) whether, in varus knee OA patients before and after HTO, these radiographic measures are different from those in normal control; and (3) whether the postoperative values of the TPI and KJLO relative to the ground are associated with short term clinical outcome scores after HTO.

DESIGN

Fifty patients who underwent HTO and 75 normal controls were assessed with four radiographic measures. We compared the measures before HTO with those after HTO and with those of the normal controls, then examined associations between the postoperative radiographic measures and clinical outcome scores 1-year after HTO.

RESULTS

After HTO, TPI increased 9.0°, whereas KJLO relative to the ground only increased 4.1°, with a compensatory change of the ankle joint line orientation. However, the postoperative KJLO relative to the ground in the HTO group was significantly different from that of the normal controls (mean difference, 4.9°; P < 0.001). In the multiple regression analyses, the postoperative radiographic measures were not associated with outcome clinical scores 1 year after HTO.

CONCLUSION

After HTO the relative KJLO changed significantly less than did the anatomical geometry of the proximal tibia. Although the KJLO after the HTO was still significantly different from that of normal knees, its value did not adversely affect clinical outcome scores 1 year after HTO.

Relationships among foot position, lower limb alignment, and knee adduction moment in patients with degenerative knee osteoarthritis

[Purpose] The aim of this study was to determine the relationships among the foot progression angle, foot rotation angle, lower limb alignment, and knee adduction moments in patients with degenerative knee osteoarthritis (OA). [Subjects] Forty-eight patients diagnosed with degenerative knee OA (Kellgren-Lawrence grades 2 and 3) were included. [Methods] To assess the lower extremity alignment and weight-bearing ratio, static radiographic measurement was used. Foot progression angle, foot rotation angle, and knee adduction moments were measured by using a three-dimensional motion analysis system. [Results] The results of this study were as follows: the foot progression angle in the early and late stance phase was significantly correlated with the first and second peak knee adduction moments; the weight-bearing ratio was significantly correlated with the first and second peak knee adduction moments; and the tibiofemoral angle was significantly correlated with the first and second peak knee adduction moments. [Conclusion] The results of the present study indicated that as the foot progression angle and the foot lateral rotation angle increased, the knee adduction moment decreased. The weight-bearing ratio and tibiofemoral angle assessment with mechanical axis alignment were correlated with the knee adduction moments. These parameters may be helpful for selecting therapeutic options for patients with degenerative knee OA.

Proximal femur shape differs between subjects with lateral and medial knee osteoarthritis and controls: the Osteoarthritis Initiative

OBJECTIVE

This study examined the association of proximal femur shape with ipsilateral medial and lateral compartment knee osteoarthritis (OA).

DESIGN

Radiographs were obtained from the NIH-funded Osteoarthritis Initiative (OAI). Cases of isolated radiographic lateral compartment knee OA were defined on baseline radiographs as Kellgren/Lawrence (K/L) Grade ≥ 2 and joint space narrowing (JSN) > 0 in the lateral compartment and JSN = 0 in the medial compartment; isolated medial compartment knee OA had K/L ≥ 2 and JSN > 0 medially with JSN = 0 in the lateral compartment. Controls had K/L < 2 and JSN = 0 in both compartments. Controls were frequency matched to cases by sex and 10-year age intervals. We characterized the shape of the proximal femurs on radiographs using Active Shape Modeling (ASM) and determined the association of proximal femur shape with knee OA using logistic regression.

RESULTS

There were 168 lateral compartment knee OA cases (mean body mass index (BMI) 29.72 ± 5.26), 169 medial compartment knee OA cases (mean BMI 29.68 ± 4.83) and 168 controls (mean BMI 26.87 ± 4.2). Thirteen modes were derived for femur shape which described 95.5% of the total variance in proximal femur shape in the population. Modes 6, 8 and 12 were associated with prevalent lateral compartment knee OA. Medial compartment knee OA was associated with proximal femur modes 1, 5, 8, and 12.

CONCLUSIONS

Prevalent lateral and medial compartment knee OA are associated with different ipsilateral proximal femur shapes. Additional studies are needed to better define how the shape of the proximal femur influences compartment-specific knee OA.

How effective is multiple needle puncturing for medial soft tissue balancing during total knee arthroplasty? A cadaveric study

We investigated the quantitative effect and risk factors for over-release during multiple needle puncturing (MNP) for medial gap balancing in varus total knee arthroplasty (TKA). Of the ten pairs of cadaveric knees, one knee from each pair was randomly assigned to undergo MNP in extension (E group), while the other knee underwent MNP in flexion (F group). The increased extension and 90° flexion gaps after every five needle punctures were measured until over-release occurred. The extension gap (< 4mm) and the 90° flexion gap (< 6mm) gradually increased in both groups. The 90° flexion gaps increased more selectively than did the extension gaps. MNP in the flexed knee, a narrow MCL, and severe osteoarthritis were associated with a smaller number of MNPs required to over-release.

Novel unidirectional porous hydroxyapatite used as a bone substitute for open wedge high tibial osteotomy

PURPOSE

The purpose of this study was to clinically and radiologically evaluate the availability, osteoconductivity, and resorption of a novel unidirectional porous hydroxyapatite (UDPHAp) used as an artificial substitute for open wedge high tibial osteotomy (OWHTO). Our hypothesis was that UDPHAp is a safe and useful bone substitute for OWHTO.

MATERIALS AND METHODS

Seven patients (2 men and 5 women aged 34-72years) who underwent OWHTO and were followed up for more than 12months were retrospectively studied. After the osteotomy, the gap created was filled with UDPHAp(REGENOS® Kuraray Co.Ltd). Radiography and computed tomography(CT) were performed, and gap healing was assessed postoperatively. The Japanese Orthopaedic Association (JOA) knee score was determined pre- and post-operatively for clinical evaluation.

RESULTS

Neither gross displacement nor collapse of the UDPHAp block graft was observed within 12 months after surgery. Both radiographs and CT showed attenuation of lucency and increasing sclerosis over time. JOA score improved from 71.2 (65-80) to 95.8 (85-100).

CONCLUSIONS

Short term results for OWHTO using UDPHAp was satisfactory. Clinical improvement of JOA scores were seen, besides osteogenesis was progressing in and around the artificial bone grafts.

Causes, risk factors, and trends in failures after TKA in Korea over the past 5 years: a multicenter study

BACKGROUND

Failure after total knee arthroplasty (TKA) may be related to emerging technologies, surgical techniques, and changing patient demographics. Over the past decade, TKA use in Korea has increased substantially, and demographic trends have diverged from those of Western countries, but failure mechanisms in Korea have not been well studied.

QUESTIONS/PURPOSES

We determined the causes of failure after TKA, the risk factors for failure, and the trends in revision TKAs in Korea over the last 5 years.

METHODS

We retrospectively reviewed 634 revision TKAs and 20,234 primary TKAs performed at 19 institutes affiliated with the Kleos Korea Research Group from 2008 to 2012. We recorded the causes of failure after TKA using 11 complications from the standardized complication list of The Knee Society, patient demographics, information on index and revision of TKAs, and indications for index TKA. The influences of patient demographics and indications for index TKA on the risk of TKA failure were evaluated using multivariate regression analysis. The trends in revision procedures and demographic features of the patients undergoing revision TKA over the last 5 years were assessed.

RESULTS

The most common cumulative cause of TKA failure was infection (38%) followed by loosening (33%), wear (13%), instability (7%), and stiffness (3%). However, the incidence of infections has declined over the past 5 years, whereas that of loosening has increased and exceeds that of infection in the more recent 3 years. Young age (odds ratio [OR] per 10 years of age increase, 0.41; 95% confidence interval [CI], 0.37-0.49) and male sex (OR, 1.88; 95% CI, 1.42-2.49) were associated with an increased risk of failure. The percentage of revision TKAs in all primary and revision TKAs remained at approximately 3%, but the annual numbers of revision TKAs in the more recent 3 years increased from that of 2008 by more than 23%.

CONCLUSIONS

Despite a recent remarkable increase in TKA use and differences in demographic features, the causes and risk factors for failures in Korea were similar to those of Western countries. Infection was the most common cause of failure, but loosening has emerged as the most common cause in more recent years, which would prompt us to scrutinize the cause and solution to reduce it.

The patterns of limb length, height, weight and body mass index changes after total knee arthroplasty

The objective of this retrospective review of 466 patients was to document changes in limb length, leg length discrepancy (LLD), height, weight, and body mass index (BMI) 1 year after TKA and the patterns of height, weight, and BMI during 5 years. To determine change patterns over 5 years, the data of 291 patients were analyzed and compared with those of age and gender-matched normal subjects. Limb length, height, and weight increased, BMI remained unchanged, and LLD decreased 1 year after TKA. The bilateral group had a greater height increase and lower rate of LLD. Preoperative mechanical tibiofemoral angle was related to limb length increase, and patients with a smaller preoperative BMI showed more weight gain. During the 5 years, weight and BMI at 1 year were maintained, but height diminished, while the healthy population showed a decreasing trend in weight.

Femoral lateral bowing and varus condylar orientation are prevalent and affect axial alignment of TKA in Koreans

BACKGROUND

Coronal alignment is considered key to the function and longevity of a TKA. However, most studies do not consider femoral and tibial anatomical features such as lateral femoral bowing and the effects of these features and subsequent alignment on function after TKA are unclear.

QUESTIONS/PURPOSES

We therefore determined (1) the prevalence of lateral femoral bowing, varus femoral condylar orientation, and severe tibia plateau inclination in female Koreans undergoing TKA; (2) whether postoperative alignments are affected by these anatomical features and improved by the use of navigation; and (3) whether postoperative coronal alignments are associated with function.

METHODS

We measured alignment in 367 knees that underwent TKA and 60 sex- and age-matched normal knees (control group). We determined patterns and degrees of femoral bowing angle, femoral condylar orientation, and tibial plateau inclination on preoperative full-limb radiographs. Postoperatively, coronal alignment of limbs and of femoral and tibial components was measured. We compared American Knee Society scores, WOMAC scores, and SF-36 scores in aligned knees and outliers (beyond ± 3° or ± 2°) at 1 year.

RESULTS

The prevalence of lateral femoral bowing was 88% in the TKA group and 77% in the control group. Mean femoral condylar orientation angle was varus 2.6° in the TKA group and valgus 1.1° in the control group, and mean tibial plateau inclination was varus 8.3° in the TKA group and varus 5.4° in the control group. Femoral lateral bowing and varus femoral condylar orientation were associated with postoperative alignments. Several clinical outcome scales were inferior in the outliers in mechanical tibiofemoral angle, anatomical tibiofemoral angle, and tibial coronal alignment but not in femoral coronal alignment outliers.

CONCLUSIONS

Lateral femoral bowing, varus condylar orientation, and severe varus inclination of the tibia plateau should be considered when performing TKA in Korean patients or patients with otherwise similar anatomical features.

The radiographic predictors of symptom severity in advanced knee osteoarthritis with varus deformity

Information concerning the abilities of radiographic parameters to predict the symptoms of advanced osteoarthritis (OA) of the knee would be valuable, because plain knee radiographs are used as one of the primary tools for the selection of treatment modalities. We aimed to identify the radiographic predictors of symptom severity in patients with varus knee OA advanced enough to warrant total knee arthroplasty (TKA). In 341 knees with primary varus OA warranting TKA, pertinent radiographic features of the medial and lateral tibiofemoral joint (TFJ), and the patellofemoral joint (PFJ) were assessed separately and scored. In addition, TF alignment was assessed on standing full-limb radiographs. Symptoms and functions were evaluated using WOMAC pain and function scores. In the univariate analyses with generalized estimating equations (GEE), multiple radiographic features (subluxation of the TFJ, overall severity of the medial TFJ, and degree of TF varus alignment) were associated with poorer WOMAC function scores, whereas only the degree of TF varus alignment was associated with poorer WOMAC pain scores. None of radiographic parameters in the PFJ or lateral TFJ (except TFJ subluxation) was associated with WOMAC scores. Multivariate analyses revealed that the degree of TF varus alignment was the strongest predictor of poorer WOMAC pain and function scores. We propose that extent of TF varus malalignment should be considered as the primary indicator of objective disease severity when selecting treatment options for patients with advanced knee OA.