The effect of knee joint rotation in the sagittal and axial plane on the measurement accuracy of coronal alignment of the lower limb

Distribution of coronal plane alignment of the knee classification in Chinese osteoarthritic and healthy population: a retrospective cross-sectional observational study

BACKGROUND

Few studies have reported the coronal constitutional alignment of the lower limbs in mainland China. This study aimed to analyse the distribution of the coronal plane alignment of the knee (CPAK) classification in the osteoarthritic (OA) and healthy Chinese populations.

MATERIALS AND METHODS

The CPAK distributions of 246 patients (477 knees) with OA and 107 healthy individuals (214 knees) were retrospectively examined using long-leg radiographs. Radiological measurements and CPAK classification of different Kellgren-Lawrence grades in patients with unilateral total knee arthroplasty (TKA) were compared. The clinical outcomes of patients with CPAK type I who underwent mechanical alignment or restricted kinematic alignment during TKA were examined.

RESULTS

The most common distributions in the OA and healthy groups were type I and type II, respectively. In patients who underwent unilateral TKA, the most common distribution of knees graded as Kellgren-Lawrence 3-4 was type I. However, the most common distributions of contralateral knees graded as Grade 0-2 were type I and II. For patients with CPAK type I, the mechanical alignment and restricted kinematic alignment groups did not differ significantly concerning postoperative clinical outcomes at 3 months.

CONCLUSION

The most common distributions in Chinese osteoarthritic and healthy populations were types I and II, respectively. In addition, OA progression may lead to changes in the CPAK classification.

The Reliability of Preoperative Total Knee Arthroplasty Planning -a Comparison of Two Calibration Markers

BACKGROUND

Preoperative templating is the gold standard in planning elective total knee arthroplasty. This retrospective study analyses preoperative templating by using two different calibration devices.

METHODS

Preoperative radiographic templating with TraumaCad using two different calibration devices was performed in 231 patients.

RESULTS

Overall, 60.6% (n = 140) did not match and 39.4% (n = 91) matched for tibial as well as femoral size. Group I showed significantly more combined matches as well as for just the size of the femoral component.

CONCLUSIONS

In this study, the KingMark calibration should be preferred to standardised ball markers.

The posterior tibial slope affects the measurement reliability regarding the radiographic parameter of the knee

BACKGROUND

Posterior tibial slope (PTS) exhibits considerable variability among individuals and is anticipated to influence the accuracy of radiographic measurements related to the knee. Despite this potential impact, there is a lack of prior research investigating how PTS affects the accuracy of these measurements. Therefore, this study aimed to investigate the effect of PTS on the measurement reliability regarding the radiographic parameter of the knee.

METHODS

The medical records of patients who took full-length anteroposterior radiographs of the lower limb between January 2020 and June 2022 were evaluated retrospectively. Radiographic parameters related to the knee joint characteristics such as osteoarthritis grade, hip-knee-ankle angle, weight-bearing line ratio, medial proximal tibial angle (MPTA), lateral distal femoral angle, joint-line convergence angle (JLCA), and PTS were measured. Subjects were classified into 3 groups according to PTS (group A, PTS < 4°; group B, PTS ≥ 4° and < 8°; group C, PTS ≥ 8°), and the measurement reliability for the radiographic variables was compared between groups. The intra- and inter-observer agreements were assessed using the kappa coefficients, intra-class correlation coefficients (ICC), and Bland-Altman plots.

RESULTS

A total of 175 limbs (86 patients) were included in this study. As the intra- and inter-observer reliability for PTS ranged over 0.9, grouping was performed based on the average of the measured PTSs. The inter-observer reliability of the MPTA and JLCA decreased as the PTS increased (ICCs for MPTA in Groups A, B, and C: 0.889, 0.796, and 0.790, respectively; ICCs for JLCA in Groups A, B and C: 0.916, 0.859, and 0.843, respectively), whereas there were no remarkable differences in other variables. Similar trends were observed in the comparisons of intra-observer reliability and Bland-Altman plots also showed consistent results.

CONCLUSION

The larger the PTS, the lower the measurement reliability regarding the radiographic parameters of the knee that includes the joint line, such as MPTA and JLCA. Given the occasional challenge in accurately identifying the knee joint line in patients with a relatively large PTS, careful measurement of radiographic parameters is crucial and utilizing repetitive measurements for verification may contribute to minimizing measurement errors.

Linear correlation between patellar positioning and rotation of the lower limb in radiographic imaging: a 3D simulation study

PURPOSE

The purpose of this study was to quantify changes in rotation of the lower limb between image pairs based on patellar position. Additionally, we investigated the differences in alignment between centralized patellar and orthograde-positioned condyles.

METHODS

Three-dimensional models of 30 paired legs were aligned in neutral position with condyles orthogonal to the sagittal axis and then rotated internally and externally in 1° increments up to 15°. For each rotation, the deviation of the patella and the subsequent changes in alignment parameters were calculated and plotted using a linear regression model. Differences between neutral position and patellar centralization were analysed qualitatively.

RESULTS

A linear relationship between lower limb rotation and patellar position can be postulated. The regression model (R2 = 0.99) calculated a change of the patellar position of - 0.9 mm per degree rotation and alignment parameters showed small changes due to rotation. The physiological lateralization of the patella at neutral position was on average - 8.3 mm (SD: ± 5.4 mm). From neutral position, internal rotation that led to a centralized patella was on average - 9.8° (SD: ± 5.2°).

CONCLUSION

The approximately linear dependence of the patellar position on rotation allows an inverse estimation of the rotation during image acquisition and its influence on the alignment parameters. As there is still no absolute consensus about lower limb positioning during image acquisition, data about the impact of a centralized patella compared to an orthograde condyle positioning on alignment parameters was provided.

LEVEL OF EVIDENCE

IV.

Patellar medial-lateral position can be used to correct the effect of leg rotation on preoperative planning in total knee arthroplasty for varus knees

BACKGROUND

Lower limb malrotations can be observed in long leg radiographs, affecting the measurement of the angle between the mechanical and anatomical axes. The purposes were to analyze the effect of limb rotation and to evaluate the accuracy of the corrected angle between the mechanical and anatomical axes based on the patellar ML position.

HYPOTHESIS

The hypothesis was that the correction of the angle between the mechanical and anatomical axes according to the patellar ML position can reduce the error from the angle in the true AP view in most of the knees.

PATIENTS AND METHODS

A total of 100 consecutive knees with varus deformity undergoing primary total knee arthroplasty were included. Computed tomography images were digitally reconstructed in the neutral position, and internally and externally rotated at 10° and 20°, respectively. The patellar ML position relative to the medial (0%) and lateral (100%) epicondyles and the angle between the mechanical and anatomical axes of the femur were measured. The corrected angle between the mechanical and anatomical axes was calculated using the averaged translational ratio.

RESULTS

In the neutral position, the patellar center position was 56.1% (standard deviation [SD]=4.7%), which was 31.4% (SD=7.2%) and 80.2% (SD=5.4%) in the 20° internal and external rotation, respectively. The angle between the mechanical and anatomical axes was 2.6° (SD=2.0°) and 8.1° (SD=2.1°) in the 20° internal and external rotation, respectively. On average, if the patellar center shifted 10%, the change of the angle between the mechanical and anatomical axes of the femur was 1.13°. Applying the corrected angle, a discrepancy from the neutral position decreased.

CONCLUSION

The method to correct the angle between the mechanical and anatomical axes according to the patellar ML position can be used to reduce the measurement error for preoperative planning using a long leg radiograph.

LEVEL OF EVIDENCE

III.

Changes in Parameters after High Tibial Osteotomy: Comparison of EOS System and Computed Tomographic Analysis

Unintended rotation of the distal tibia occurs during medial open-wedge high tibial osteotomy (MOWHTO). Computed tomography (CT) is the standard method of measuring lower limb alignment; however, the new low-dose EOS system allows three-dimensional limb modeling with automated measurements of lower limb alignment. This study investigated the differences between the changes in lower limb alignment profiles obtained using the EOS system and CT in patients who underwent MOWHTO. We investigated whether any factors contributed to the degree of deformation. Thirty patients were prospectively enrolled between October 2019 and February 2023. Changes in femoral and tibial torsion, femorotibial rotation, and posterior tibial slope were measured using pre- and post-MOWHTO CT and EOS images. We found no significant difference in pre- and postoperative tibial torsion or posterior tibial slope between CT and EOS. No variables showed a significant correlation with changes in the tibial torsion or posterior tibial slope. This study confirmed the possibility that the EOS system could replace CT in measuring changes in several parameters pre- and postoperatively. Furthermore, we confirmed that the distal tibia tended to be internally rotated after MOWHTO; however, we found no significantly related parameters related to deformation caused by MOWHTO.

The effect of weight-bearing positions on coronal lower limb alignment: A systematic review

BACKGROUND

The coronal alignment of the lower limb is generally accepted as a major determinant of surgical outcome in total knee arthroplasty (TKA). To achieve the ideal post-operative alignment, surgeons need to be aware of the influence that weight-bearing positions have on the final knee alignment. Therefore, this review aims to define the effect of varying weight-bearing positions on the coronal alignment of the lower limb. We hypothesized that a coronal alignment deformity increases with loading.

METHODS

The PubMed, Medline and google scholar databases were searched systematically in June 2022. Only studies which compared coronal alignment with a standardized radiographic protocol in the single leg, double leg and supine positions were included. To obtain pooled estimates of the effect of different weight-bearing positions, random-effect analysis were fitted using SAS.

RESULTS

Compared to the supine position, double leg weight-bearing positions were found to be associated with a more pronounced varus deformity (mean difference in HKA is 1,76° (95% CI 1,32: 2,21), p < 0.0001)). The mean difference in HKA between double leg and single leg weight-bearing conditions was 1.43° (95% CI (-0,042;2,90), p = 0.0528).

CONCLUSION

The overall knee alignment was found to be influenced by the weight-bearing position. An average difference of 1.76° in HKA-angle was found between a double leg-stance and supine position, tending to increased varus in the former weight-bearing position. It is therefore possible that the deformity could increase by 1.76° if knee surgeons only follow a pre-op planning based on double-leg stance full length radiographs.

Comparison of CT and EOS in assessing coronal lower limb alignment when planning total knee arthroplasty

BACKGROUND

As surgical technologies and alignment strategies develop, accuracy of lower limb alignment assessment gains increasing importance. The current gold standard remains long leg (4ft) radiographs. Other measures include computed tomography (CT) and EOS scans. This study aimed to compare CT and EOS long leg views to determine the reliability of assessment of hip-knee-angle (HKA) in arthritic knees.

MATERIALS AND METHODS

A retrospective study of 96 knees in patients undergoing total knee arthroplasty (TKA) was performed comparing HKA alignment data from EOS and CT. Coronal HKA and sagittal flexion angle were assessed by two independent observers. Inter-observer correlation was calculated.

RESULTS

The coronal alignment on EOS was strongly positively correlated to coronal alignment on CT (r = 0.927, p = 0.001). 12 knees (13 %) exceeded CT vs EOS difference of 3°. Inter-rater reliability was excellent (intra-class coefficients >0.9). The mean difference between CT and EOS was significantly greater for patients with fixed flexion >10° (0.68) vs <10° (-0.2) p = 0.004. Mean difference in HKA did not differ between those 0-10° varus and >10° varus (p = 0.273). Valgus HKA had a higher mean difference (1.9°) compared to varus knees (-0.4°) (p = 0.001).

CONCLUSION

CT and EOS showed excellent inter-rater reliability and correlated well. Increased sagittal plane deformity does effect coronal HKA assessment. Extreme varus did not affect the mean difference significantly, while valgus did. For the majority of patients either CT or EOS will give a reliable assessment of HKA but beware those with significant valgus or sagittal deformity where both modalities may be necessary to plan TKA.

Correlation of knee laxity with alignment and repetitive physical activity in patients with knee osteoarthritis: A cross-sectional study

BACKGROUND

Malalignment, knee laxity, and repetitive physical activity are considered biomechanical risk factors for knee osteoarthritis (KOA), though the correlation among these factors is poorly understood. The purpose of this study was to elucidate the relationship between knee laxity and alignment, and to determine the effects of repetitive physical activity on knee laxity in patients with KOA.

METHODS

The study subjects were 68 patients with radiographic tibiofemoral KOA and 68 control subjects. Each participant underwent clinical evaluation, muscle strength test, radiography, and knee laxity test. Laxity was evaluated before and after repetitive stepping exercise using tri-axial accelerometer.

RESULTS

Mediolateral acceleration correlated (P < 0.01) with two coronal alignments (mechanical axis: hip-knee-ankle angle (HKA); and joint line convergent angle (JLCA)). Pearson correlation coefficient was small (r = 0.23-0.24) before but increased after stepping (r = 0.28-0.33). Increased mediolateral acceleration after stepping correlated with JLCA (r = 0.37, P < 0.001). There were significant differences in coronal alignments, gait speed, mediolateral acceleration, and accelerations in all directions between the control and KOA groups. Anteroposterior acceleration did not correlate with sagittal knee alignment. Multiple logistic regression analysis identified HKA/JLCA, and increased mediolateral acceleration after stepping as significant diagnostic predictors of KOA.

CONCLUSIONS

We found a direct relationship between knee laxity and alignment or repetitive physical activity. Repetitive stepping activity significantly increased mediolateral acceleration in KOA patients, compared with the control. Stepping increased the correlation between mediolateral acceleration and coronal alignment. In knees with large JLCA, repetitive stepping caused much larger mediolateral laxity.

Factor affecting the discrepancy in the coronal alignment of the lower limb between the standing and supine radiographs

BACKGROUND

Conflicting results have been reported regarding the factors that can predict the discrepancy in the coronal alignment of the lower limb between radiographs taken in the standing and supine positions. Therefore, this study aimed to investigate factors that can predict discrepancies in the coronal alignment of the lower limb between radiographs taken in the standing and supine positions.

METHODS

We retrospectively evaluated the medical records of patients who underwent full-length anteroposterior radiographs of the lower limb in both standing and supine positions between January 2019 and September 2021. The discrepancy in the coronal alignment of the lower limb between the standing and supine radiographs was defined as the absolute value of the difference in the hip-knee-ankle (HKA) angle between the two radiographs, which is presented as the ΔHKA angle. Correlation and regression analyses were performed to analyse the relationship among ΔHKA angle, demographic data, and several radiographic parameters.

RESULTS

In total, 147 limbs (94 patients) were included in this study. The mean ΔHKA angle was 1.3 ± 1.1° (range, 0-6.5°). The ΔHKA angle was significantly correlated with body mass index and several radiographic parameters, including the HKA angle, joint line convergence angle, and osteoarthritis grade. Subsequent multiple linear regression analysis was performed using the radiographic parameters measured on the supine radiographs with the two separate models from the two observers, which revealed that body mass index and advanced osteoarthritis (Kellgren-Lawrence grades 3 and 4) had a positive correlation with the ΔHKA angle.

CONCLUSIONS

Body mass index and advanced osteoarthritis affected the discrepancy in the coronal alignment of the lower limb between standing and supine radiographs. A discrepancy in the coronal alignment of the lower limb could be more prominent in patients with an increased body mass index and advanced osteoarthritis, corresponding to Kellgren-Lawrence grades 3 and 4.

Sagittal femoral bowing contributes to distal femoral valgus angle deviation in malrotated preoperative radiographs

Background

The coronal whole-leg radiograph is generally used for preoperative planning in total knee arthroplasty. The distal femoral valgus angle (DFVA) is measured for distal femoral bone resection using an intramedullary guide rod. The effect of coronal and sagittal femoral shaft bowing on DFVA measurement in the presence of malrotation or knee flexion contracture has not been well reported. The objectives of this study were: (1) to investigate the effects of whole-leg malrotation and knee flexion contracture on the DFVA in detail, (2) to determine the additional effect of coronal or sagittal femoral shaft bowing.

Methods

We studied 100 consecutive varus and 100 valgus knees that underwent total or unicompartmental knee arthroplasty. Preoperative CT scans were used to create digitally reconstructed radiography (DRR) images in neutral rotation (NR, parallel to the surgical epicondylar axis), and at 5° and 10° external rotation (ER) and internal rotation (IR). The images were also reconstructed at 10° femoral flexion. The DFVA was evaluated in each DRR image, and the angular variation due to lower limb malposition was investigated.

Results

The DFVA increased as the DRR image shifted from IR to ER, and all angles increased further from extension to 10° flexion. The DFVA variation in each position was 1.3° on average. A larger variation than 2° was seen in 12% of all. Multivariate regression analysis showed that sagittal femoral shaft bowing was independently associated with a large variation of DFVA. Receiver operating characteristic analysis showed that more than 12° of sagittal bowing caused the variation.

Conclusion

If femoral sagittal bowing is more than 12°, close attention should be paid to the lower limb position when taking whole-leg radiographs. Preoperative planning with whole-leg CT data should be considered.

Coronal and sagittal alignment of the lower limb in Caucasians: Analysis of a 3D CT database

INTRODUCTION

Lower limb alignment is a major determinant of long-term outcomes after osteotomy or total knee replacement. The aim of this paper is to define the mean values of coronal and sagittal lower limb alignment for Caucasians as a function of sex using 3D reconstructions from CT-scans.

MATERIALS AND METHODS

The analysis involved 586 Caucasian patients (269 males and 317 females) who had their hip-knee-ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior proximal tibial angle (PPTA), lateral and medial proximal posterior tibial angles (LPPTA/MPPTA), posterior distal femoral angle (PDFA), and non-weightbearing joint convergence angle (nwJLCA) measured. This analysis was performed using a CT-scan-based modelling system (SOMA). Differences between sexes and morphotypes (neutral, varus and valgus) were analyzed statistically.

RESULTS

The mean HKA was 180±2.57°, LDFA 86.1±1.87°, MPTA 86.1±2.15°, PPTA 84.6±2.58°, LPPTA 84.9±3.17°, MPPTA 85.1±3.21°, PDFA 85.3±1.50° and nwJLCA 0.82±1.32°. There was a significant difference between sexes for the HKA (180.3±2.46° and 179.0±2.52°), LDFA (85.6±1.90° and 86.8±1.61°), MPPTA (84.7±3.06° and 85. 6±3.31°). The neutral morphotype was more frequent in women than men (78% vs. 73%), the varus morphotype was more frequent in men than women (20% vs. 7.6%) and the valgus morphotype was more frequent in women than men (15% vs. 6.7%).

CONCLUSION

Normal parameters for lower limb alignment in Caucasian patients were described in the coronal and sagittal planes. There was a significant influence of sex in the coronal plane, which was not found in the sagittal plane.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Rapid X-Ray-Based 3-D Finite Element Modeling of Medial Knee Joint Cartilage Biomechanics During Walking

Finite element (FE) modeling is becoming an increasingly popular method for analyzing knee joint mechanics and biomechanical mechanisms leading to osteoarthritis (OA). The most common and widely available imaging method for knee OA diagnostics is planar X-ray imaging, while more sophisticated imaging methods, e.g., magnetic resonance imaging (MRI) and computed tomography (CT), are seldom used. Hence, the capability to produce accurate biomechanical knee joint models directly from X-ray imaging would bring FE modeling closer to clinical use. Here, we extend our atlas-based framework by generating FE knee models from X-ray images (N = 28). Based on measured anatomical landmarks from X-ray and MRI, knee joint templates were selected from the atlas library. The cartilage stresses and strains of the X-ray-based model were then compared with the MRI-based model during the stance phase of the gait. The biomechanical responses were statistically not different between MRI- vs. X-ray-based models when the template obtained from X-ray imaging was the same as the MRI template. However, if this was not the case, the peak values of biomechanical responses were statistically different between X-ray and MRI models. The developed X-ray-based framework may pave the way for a clinically feasible approach for knee joint FE modeling.

Association of alignment variables, posteromedial tibial cartilage wear and anterior cruciate ligament insufficiency in participants with varus knee osteoarthritis: a cross-sectional study

PURPOSE

Total knee arthroplasty (TKA) and unicompartment knee arthroplasty (UKA) are among the most important treatment options for end-stage knee osteoarthritis. Previous papers have noted the importance of knowing the type of medial tibial wear in deciding to manage varus knee osteoarthritis patients with TKA vs UKA. But few studies have delineated the pre-operative variables predicting the type of tibia wear.

METHODS

This study assessed individuals with varus knee osteoarthritis planned for knee arthroplasty. After recording the demographic variables, hip-knee-ankle joint alignment views were taken from all patients. Finally, the type of tibial wear encountered during the surgery (posteromedial, non-posteromedial) was documented.

RESULTS

A total of 325 knees and 301 participants were evaluated in the study. Participants aged 67.12 (± SD 8.14) and the male to female ratio was 0.20. Between either non-posteromedial/posteromedial wear or insufficient/sufficient ACL cases, there was a statistically significant difference with regard to MPTA, LDFA, VA, and JCA (P value < 0.05). Sixty-three percent of knees had non-posteromedial wear in the tibia plateau and 37% had posteromedial wear. Posteromedial wear was associated with 95% chance of ACL tear. Non-posteromedial knee had nearly 50% chance of having ACL insufficiency. Among non-posteromedial cases, VA of 14.5 as cut-off value had 65% sensitivity, 90% specificity, 73% negative predictive value, 87% positive predictive value, and 78% accuracy in detecting ACL insufficiency.

CONCLUSION

Posteromedial tibial wear is associated with ACL insufficiency. However, regarding non-posteromedial cases, varus angle > 14.5 is highly predictive of ACL tear (87% positive predictive value).

Comparison of Lower-Limb Alignment in Patients with Advanced Knee Osteoarthritis: EOS Biplanar Stereoradiography versus Conventional Scanography

Background

Accurate measurement of the lower limb alignment is one of the most crucial factors in advanced knee osteoarthritis patients scheduled for surgery. Recently, EOS biplanar stereoradiography with three-dimensional reconstruction was developed. The purpose of this study was to compare radiographic parameters between conventional scanography and EOS in patients with advanced knee osteoarthritis who need surgical treatment.

Methods

A total of 52 consecutive patients (104 knees) with bilateral knee osteoarthritis of advanced stage (Kellgren-Lawrence [KL] grade 3 or 4) were retrospectively reviewed. We measured the hip-knee-ankle angle (HKA) on conventional scanograms. In EOS, we measured HKA, hip-knee-shaft angle, mechanical lateral distal femoral angle, and mechanical medial proximal tibial angle. To evaluate sagittal and axial plane alignment, knee flexion angle (KFA), and knee joint rotation (KJR) were also measured.

Results

Ninety knees were KL grade 4, and 14 knees were grade 3. The average HKA was 10.14° ± 6.16° on conventional scanograms and 11.26° ± 6.21° in EOS. HKA was greater in EOS than on conventional scanograms, and the difference (1.12°; range, −1.07° to 3.22°) was statistically significant (p < 0.001). Significant correlations were observed on the difference in HKA and mechanical medial proximal tibial angle (r = –0.198, p = 0.044), KFA (r = 0.193, p = 0.049), and KJR (r = 0.290, p = 0.003). In multivariable linear regression analysis, the difference in HKA had significant relationship with KFA (β = 0.286, p = 0.003) and KJR (β = 0.363, p < 0.001).

Conclusions

HKA measured on conventional scanograms and in EOS differed significantly and the difference had a significant correlations with KFA, KJR, and medial proximal tibial angle. Surgeons can consider these results before orthopedic surgery in patients who have advanced knee osteoarthritis.

A 2021 consensus statement on osteotomies around the knee by the UK Knee Osteotomy consensus Group (KOG)

BACKGROUND

There are significant deficiencies in the evidence base of modern-day osteotomy which result in significant variation in practice between surgeons. The purpose of this statement was to develop a consensus statement on the practice of osteotomy so that a more standardized approach to the indications, surgical technique, and postoperative care could be outlined. The article is also intended to educate and inform the practice of individuals who are early in their experience and/or clinical practice.

METHOD

A group of 29 specialist knee surgeons who regularly perform osteotomy was convened to form the Knee Osteotomy consensus Group (KOG). Consensus was determined utilizing the consensus group technique described by List. A total of 37 questions were asked covering all aspects of clinical practice.

RESULTS

20 statements were generated and debated until a criterion level of 70% was met.

CONCLUSIONS

Consensus was achieved regarding 20 statements concerning Indications for surgery, decision making, surgical planning, technique, post-operative assessment and recovery.

Evaluation of the reliability of lower extremity alignment measurements using EOS imaging system while standing in an even weight-bearing posture

This study aimed to analyze the reproducibility and reliability of the alignment parameters measured using the EOS image system in both limbs while standing with an even weight-bearing posture. Overall, 104 lower extremities in 52 patients were analyzed retrospectively. The patients stood with an even load over both lower extremities then rotated 15° in both directions. Two EOS images were acquired and 104 pairs of lower extremities were compared according to the position of the indexed lower extremities. Then, the inter-observer reliability of the EOS system and the inter-modality reliability between EOS and computed tomography (CT) were evaluated. Femoro-tibial rotation (FTR) and tibial torsion demonstrated a significant difference between the anterior and posterior positions of the indexed lower extremity. In the inter-observer reliability analysis, all values except for FTR and tibial torsion demonstrated good or very good reliability. In the anterior position, FTR demonstrated moderate, and tibial torsion demonstrated poor reliability. In the posterior position, both FTR and tibial torsion demonstrated poor reliability. In the reliability analysis between the three-dimensional (3D) EOS model and 3D CT images, all measurements of the femur demonstrated very good reliability, but measurements of the tibia did not. For the coronal and sagittal alignment parameters measured by the EOS 3D system with rotated standing posture, except for the measurement including tibial torsion., there were no significant difference for either position of the indexed extremities with high agreement between the observers as well as with the CT 3D model.

Custom TKA enables adequate realignment with minimal ligament release and grants satisfactory outcomes in knees that had prior osteotomies or extra-articular fracture sequelae

PURPOSE

To report the early clinical and radiographic outcomes of custom total knee arthroplasty (TKA) in knees that had prior osteotomies and/or extra-articular fracture sequelae.

METHODS

The authors retrospectively analysed a consecutive series of 444 knees that received custom TKA between 2016 and 2019 and identified 41 knees that had prior extra-articular events (osteotomies or fracture sequelae). Patients responded to pre- and post-operative (> 12 months) questionnaires, including Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Net improvements were calculated by subtracting pre- from post-operative scores. In addition to a preoperative CT scan, pre- and post-operative long-leg weight-bearing radiographs were obtained, on which the hip-knee-ankle (HKA) angle, femoral mechanical angle (FMA, between femoral mechanical axis and joint line) and tibial mechanical angle (TMA, between tibial mechanical axis and joint line) angles were measured, and alignment was planned within a 'target zone' of FMA and TMA within 85°-95° and HKA angle within 175°-183°. Agreements between preoperative, planned and post-operative angles were calculated using intra-class correlation coefficients (ICC).

RESULTS

From the initial 41 knees, 3 had incomplete post-operative data and 1 was revised for painful stiffness due to uncorrected rotational malunion, leaving 37 knees for analysis. Twenty had prior osteotomies (tibia, n = 18, femur, n = 2), 8 had isolated fractures (tibial, n = 3; femoral, n = 5), and 9 had both osteotomies and fractures. Postoperative coronal alignments were 90.4° ± 2.4° for FMA, 89.3° ± 2.6° for TMA and 179.9° ± 3.0° for HKA angle. Agreements between planned and achieved alignments were fair to excellent, and 29 (78%) knees were within the 'target zone'. At a mean follow-up of 15 ± 5 months, all clinical scores had improved significantly (p < 0.001).

CONCLUSIONS

Custom TKA granted satisfactory clinical outcomes and a low complication rate in knees that had prior osteotomies and/or extra-articular fracture sequelae. Using custom implants and strategies for coronal alignment, 29 (78%) of the 37 knees were successfully aligned within the 'target zone', and 35 (95%) of the 41 knees did not require ligament release.

LEVEL OF EVIDENCE

IV.

An Increase in Medial Joint Space Width After Medial Open-Wedge High Tibial Osteotomy Is Associated With an Increase in the Postoperative Weight-Bearing Line Ratio Rather Than With Cartilage Regeneration: Comparative Analysis of Patients Who Underwent Second-Look Arthroscopic Assessment

PURPOSE

To investigate relevant factors influencing increases in medial joint space width (JSW) after medial open-wedge high tibial osteotomy (MOWHTO).

METHODS

Between January 2010 and December 2018, the electronic medical records of consecutive patients who underwent MOWHTO and subsequent second-look arthroscopic assessment at least 12 months after MOWHTO were retrospectively evaluated. The patients were classified into 2 groups according to changes in the medial JSW of the knee at the time of the second-look operation compared with that at baseline before the initial surgical procedure. Various radiographic parameters, arthroscopic findings, and clinical scores were compared between the groups, and regression analysis was performed to identify factors related to increases in medial JSW.

RESULTS

A total of 114 patients were analyzed. In a bivariate analysis, patients who experienced an increase in medial JSW showed a significantly higher postoperative weight-bearing line ratio (WBLR) (P = .008) and a greater proportion of severe preoperative cartilage lesions in the medial compartment of the knee compared with patients with a maintained or reduced medial JSW (P = .035). In terms of clinical scores, patients with an increased medial JSW showed relatively favorable clinical outcomes at the time of the second-look operation. Regression analysis indicated only postoperative WBLR as a relevant factor associated with an increase in medial JSW after MOWHTO (odds ratio, 1.057; P = .01). Additional analysis with patients reclassified according to the postoperative WBLR showed that as the postoperative WBLR increased, the medial JSW increased, without a significant change in the lateral JSW.

CONCLUSIONS

An increase in the medial JSW of the knee joint after MOWHTO appears to be associated with an increase in the postoperative WBLR, not with cartilage regeneration. Obtaining adequate correction so that the postoperative WBLR is within 60% to 70% would be desirable in terms of postoperative changes in the medial JSW, as well as clinical outcomes.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.