Tibiofemoral Rotation Research Articles

Exploring healthy knee kinematic phenotypes obtained through dynamic CT imaging: A cluster analysis study

Dynamic Computed Tomography (CT) emerges as a pivotal imaging modality for the assessment of knee joint kinematics. However, integrating dynamic CT into clinical practice necessitates a thorough understanding of healthy knee kinematics, as large variation in kinematics has been described within healthy populations. Therefore, this study aims to identify and describe healthy phenotypes with homogenous knee kinematics using a clustering approach. A total of 120 healthy knees from 64 participants underwent dynamic CT scanning during knee extension and flexion. Eight tibiofemoral (TF) and patellofemoral kinematic parameters were extracted, after which K-means clustering was applied to identify homogenous kinematic clusters. Kinematic phenotypes were obtained by calculating the median and interquartile range (IQR) for all kinematic parameters per cluster. Two distinct clusters were found, comprising 53 (Cluster 1) and 67 (Cluster 2) knees. Statistically significant differences between the clusters were found in six out of eight kinematic parameters. The most notable differences were observed in TF rotations, with cluster 1 exhibiting a greater amount of internal and adduction rotation of the tibia compared to cluster 2. The two kinematic phenotypes provide new insights into the nuanced variation within a healthy cohort and can serve as reference for future studies evaluating pathological kinematic phenotypes using dynamic CT.

Variability of three-dimensional knee morphology cannot be effectively assessed using a coronal plane knee alignment classification in total knee arthroplasty patients.

Optimal reproduction of the native three-dimensional (3D) alignment in total knee arthroplasty (TKA) influences outcomes; however, much of the modern TKA alignment research, such as the coronal plane alignment of the knee (CPAK), focuses only on coronal alignment. Tibial, femoral and tibiofemoral measurements on the axial and sagittal planes were evaluated for their relationship to the arithmetic hip-knee-ankle angle (aHKA) and joint-line obliquity (JLO). These 3D anatomical measurements are also evaluated across CPAK groups. A retrospective analysis of the 360 Med Care computed tomography (CT) database was performed. Patient CT scans were segmented and landmarked. Linear regression analysis compared 12 axial and sagittal plane measurements (representing tibial, femoral and tibiofemoral rotation, tibial slope and femoral flexion) with both aHKA and JLO. Nonparametric tests assessed these anatomical measurements across the different CPAK groups, while Cohen's delta (d) determined the effect size. With a sample size of 7450 osteoarthritic knees, significant but weak relationships (r < 0.30) were observed between all 12 anatomical measurements and both aHKA and JLO. Tibiofemoral rotations between Insall's axis and both the posterior condylar and the surgical transepicondylar axes demonstrated large effect sizes (d > 0.80). However, trivial to small effect sizes (d < 0.50) were broadly observed across the 12 axial and sagittal measurements, underscoring their limited clinical significance. While useful for describing coronal knee anatomy, CPAK phenotypes fail to differentiate tibial, femoral and tibiofemoral rotation, tibial slope or femoral flexion-crucial aspects of 3D surgical planning. Therefore, more comprehensive knee phenotyping solutions are required to guide individualised TKA alignment strategies. Level II.

A new method called MiKneeSoTA to minimize knee soft-tissue artifacts in kinematic analysis

The use of marker-based optical motion capture to estimate joint kinematics during gait is currently limited by errors associated with soft-tissue-induced motion artefacts (STIMA) and ambiguity in landmark palpation. This study therefore presents a novel protocol aiming to Minimize Knee Soft-Tissue Artefacts (MiKneeSoTA) and their effect on kinematic estimates. Relying on an augmented marker set and a new inverse kinematics approach, our method leverages frame-by-frame optimization to adjust best-fit cylinders that have been automatically generated based on the relative position of lower limb markers during an initial static trial. Tibiofemoral rotations and translations are then calculated along the anatomical joint axes based on the relative 3D motion of these cylinders. When compared against the conventional Helen-Hayes approach, in vivo assessment of fifteen healthy subjects revealed the MiKneeSoTA approach led to kinematic profiles with significantly lower standard deviations in joint rotations across trials, and even visibly reduced the presence of high frequency fluctuations presumably associated with e.g. soft-tissue vibration. In addition to agreeing with previously published bone pin and fluoroscopy datasets, our results illustrate MiKneeSoTA’s ability to abate the effect of STIMA induced by lateral knee ligaments. Our findings indicate that MiKneeSoTA is in fact a promising approach to mitigate knee joint STIMA and thus enable the previously unattainable accurate estimation of translational knee joint motion with an optoelectronic system.

Habitual patellar dislocation exhibits less severe rotational deformities but poorer trochlear development and higher incidence of patella baja compared with recurrent patellar dislocation in skeletally mature patients.

This study compared the radiological characteristics between habitual and recurrent patellar dislocation in skeletally mature patients. From 2017 to 2019, 77 skeletally mature patients with habitual patellar dislocation were surgically treated at a single institution and reviewed retrospectively. A total of 55 knees from these patients were included in the habitual patellar dislocation group. During the same period, 55 knees with recurrent patellar dislocation were randomly selected from 242 patients and included in the recurrent patellar dislocation group. Various bony deformities were measured and compared between the two groups. Additionally, a subgroup analysis was conducted among patients with habitual patellar dislocation, comparing those with and without an 'invisible patella' observed on true lateral views with 30° of knee flexion. The femoral anteversion angle (21.8° vs. 26.3°, p = 0.041), tibiofemoral rotation angle (9.7° vs. 12.4°, p = 0.042) and external tibial rotation angle (24.3° vs. 29.6°, p = 0.001) in the habitual patellar dislocation group were significantly lower than those in the recurrent patellar dislocation group. 54% of knees in the habitual patellar dislocation group had a patella baja, and this was in sharp contrast to the recurrent patellar dislocation group in which none of the knees had a patella baja. 49.1% of knees in the habitual patellar dislocation group showed 'invisible patella' at 30° of knee flexion, and knees with 'invisible patella' had significantly higher tibial tubercle-trochlear groove (TT-TG) distance (30.4 vs. 19.8, p < 0.001) and tibiofemoral rotation angle (13.2° vs. 6.4°, p < 0.001) than knees with a visible patella. A distinct difference in bony anatomical features was observed between habitual and recurrent patellar dislocation in skeletally mature patients. Habitual patellar dislocation exhibited less severe rotational deformities of the lower extremity but showed poorer trochlear and patellar development, a larger TT-TG distance and a higher incidence of patella baja compared with recurrent patellar dislocation. Level III.

Trochlear Dysplasia Is Associated With Increased Sagittal Tibial Tubercle Trochlear-Groove Distance in Patients With Patellar Instability

To compare the sagittal position of the tibial tubercle in relation the trochlea groove in patients with and without trochlear dysplasia (TD). Patients with high-grade TD show a significantly increased sagittal position of the tibial tubercle in relation to the trochlear groove (sTTTG) compared with patients without TD. This may affect patellofemoral loading and contribute to the increased prevalence of cartilage lesions seen in the patellofemoral joint of patients with dysplasia of the trochlear groove. All patients between January 2017 and December 2020 with high-grade TD (Dejour type B, C, and D) who underwent patellar-stabilizing surgery for patellar instability at a single institution were included in the current study. Patients without preoperative magnetic resonance imaging (MRI), any previous osteotomy on the affected lower extremity, or cruciate ligament insufficiency were excluded. Patients who underwent knee arthroscopy for meniscal repair/debridement without any signs of TD or any of the aforementioned criteria served as the control group. Preoperative MRI was retrospectively assessed to compare common patellofemoral anatomic parameters including patellar angle, patellar tilt, patella morphology according to Wiberg, Caton-Deschamps index, PF index, trochlear sulcus angle, sulcus depth, lateral inclination angle of the trochlea, tibiofemoral rotation, TTTG, and sTTTG distance between both groups. The sTTTG is measured as the distance between the nadir point of the cartilaginous trochlear groove and the most anterior point of the tibial tubercle on an axial MRI. Independent predictors for the sTTTG were assessed for patients with TD. Patients with high-grade TD (n= 82) showed an increased patellar tilt, Caton-Deschamps index, trochlear sulcus angle, lateral tibiofemoral rotation angle, TTTG, and sTTTG (9.16 ± 4.47 mm vs 2.66 ± 4.21 mm) compared with the control group (n=83) (P < .001). Patellar angle, PF index, sulcus depth, and lateral inclination angle of the trochlear were significantly decreased in the TD group (P < .001). The sTTTG was similar in all TD groups (n.s.). Among patients with TD, both tibiofemoral rotation and patellar height were independent predictors of the sTTTG (P < .05). Patients with high-grade TD show not only abnormal values in common patellofemoral instability risk factors but also a significantly increased sTTTG compared with patients without TD. Level III, retrospective case comparative study.

No significant change of tibiofemoral rotation after femoral rotational osteotomy in patients with patellofemoral instability.

An increased value of tibiofemoral rotation is frequently observed in patients with patellofemoral instability or maltracking. Nevertheless, the appropriate approach for addressing this parameter remains unclear so far. One potential approach for correcting tibiofemoral rotation is femoral rotational osteotomy. We hypothesized that femoral rotational osteotomy affects tibiofemoral rotation. All patients who underwent femoral rotational osteotomy between January 2018 and May 2022 were included in this study. Pre- and postoperative tibiofemoral rotation and the degree of femoral rotation were measured using two-dimensional (2D) and three-dimensional (3D) measurements. The effect of femoral rotation on tibiofemoral rotation was assessed. Forty knees (18 rightand 22 left) of 36 patients (28 femalesand 8 males) were included. Mean preoperative femoral torsion was 32.1 ± 10.1° in 2D and 30.8 ± 10.1° in 3D. Femoral rotation was performed by -14.1 ± 8.3° using 2D measurements and -15.0 ± 8.0° using 3D measurements. Tibiofemoral rotation changed from 9.9 ± 6.2° to 9.7 ± 6.0° (p = n.s.) in 2D, and from 10.2 ± 5.5° to 9.4 ± 5.4° (p = n.s.) in 3D. Tibiofemoral rotation showed no significant changes after femoral rotational osteotomy. Hence, femoral rotational osteotomy cannot be used to correct tibiofemoral rotation in addition to correcting the femoral version. Other surgical techniques need to be evaluated if correction of tibiofemoral rotation is required. Level III.

The effect of movement system impairment-based classification treatment compared to routine physiotherapy on pain, disability, alignment, and movement impairments in individuals with tibiofemoral rotation syndrome: a randomized controlled trial

BackgroundKnee pain is a common musculoskeletal problem. Lower extremity movement impairments could alter stresses in different planes and contribute to knee pain. Classifying these impairments may be helpful in the diagnosis and treatment of knee problems. Movement system impairment (MSI)-based classification is a system to evaluate movement impairments. Trials that involve this classification are limited. Therefore, it will be of interest to examine the effect of movement system impairment-based classification treatment compared to routine physiotherapy in individuals with tibiofemoral rotation syndrome.MethodsTwenty-two individuals with knee pain aged 18–40 years (2 males, 20 females) diagnosed with tibiofemoral rotation (TFR) syndrome were included. After initial evaluation, individuals were randomly assigned into two treatment groups (MSI-based treatment and routine physiotherapy). Both treatment groups contained 8 treatment sessions over 4 weeks. Alignment and movement impairments data form, a numeric rating scale (NRS), and the Kujala Disability Questionnaire were assessed at baseline and after a four-week intervention. Independent samples t-test and Mann-Whitney U test were used for quantitative variables, and Fisher’s exact test was employed for qualitative variables to compare the groups. One-way Analysis of variance (ANOVA) and paired samples t-test were utilized to within-group changes of quantitative variables, and qualitative variables were analyzed with the McNemar test.ResultsThe results showed that pain intensity and disability significantly decreased within and between groups after intervention (P > 0.05). There were also statistically significant differences between treatment groups for 3 out of 6 alignment and movement impairments (PS-FAdd/IR, Step down-Add/Valgus, and STS-Add/Valgus) (P > 0.05). Within-group differences for alignment and movement impairments were significant only for the MSI-based treatment group (P > 0.05).ConclusionsThe findings suggest that a specific MSI-based treatment, considering a homogenous group of individuals with knee pain, may contribute to pain, disability, and alignment and movement impairments improvement. Therefore, it is important to notice the classification-based treatment for individuals with knee pain.Trial Registration Number (TRN) and date of registrationThe trial was registered at the (https://www.irct.ir), (IRCT20210505051181N3) on 17/7/2021.

Recurrent patellar dislocation patients with high-grade J-sign have multiple structural bone abnormalities in the lower limbs.

To explore the relationship between preoperative J-sign grading and structural bone abnormalities in patients with recurrent patellar dislocation (RPD). A retrospective study was conducted on RPD patients over 5 years. Patients were categorised based on J-sign grade into low (J- and J1+), moderate (J2+) and high groups (J3+). Trochlear dysplasia (TD) and osseous structures (femoral anteversion angle [FAA], knee torsion, tibial tuberosity-trochlear groove [TT-TG] distance, Caton-Deschamps index) were assessed and grouped according to risk factor thresholds. The χ2 test was used to compare composition ratio differences of structural bone abnormalities among the groups. A total of 256 patients were included, with 206 (80.5%) females. The distribution of J-sign grade was as follows: 89 knees (34.8%) of low grade, 86 moderate (33.6%) and 81 high (31.6%). Among the five structural bone abnormalities, TD was the most common with a prevalence of 78.5%, followed by increased TT-TG at 47.4%. Excessive tibiofemoral rotation had the lowest occurrence at 28.9%. There were 173 (67.6%) patients who had two or more abnormalities, while 45 (17.6%) had four to five bony abnormalities. Among patients with any bony abnormality, the proportion of high-grade J-sign surpassed 40%. Patients with moderate and high-grade J-sign had more increased FAA and more pronounced patella alta (all p < 0.001). The proportion of excessive knee torsion and TD increased with increasing each J-sign grade, with the more notable tendency in knee torsion (high vs. moderate vs. low-grade: 61% vs. 22% vs 7%, p < 0.001). Furthermore, the higher J-sign grade was also associated with more combined bony abnormalities (p < 0.001). In the high-grade J-sign group, 90.2% of the knees had two or more bony risk factors and 40.7% had four or more, which were significantly higher than the moderate and low-grade J-sign groups (40.7% vs. 11.6% vs. 2.2%, p < 0.001). In patients with a high-grade J-sign, over 90% of the lower limbs had two or more structural bone risk factors, and more than 40% had four or more. These proportions were significantly higher compared to knees with low-grade and moderate J-sign. In clinical practice, when treating high-grade patellar mal-tracking, it is important to focus on and correct these strongly correlated abnormal bone structures. Level III.

Evaluation of the Kinesio Taping and Real-Time External Feedback Effects on Lower Extremity Function During Single-Leg Squat in Individuals With Tibiofemoral Varus Alignment

Background and Aims People with postural malalignment such as tibiofemoral varus (TFRV) may experience movement patterns dysfunction during functional activities that are related to non-contact lower extremity injuries. Training protocols should be designed for these people to control and improve their functional dysfunctions. The present study aimed to investigate the effect of posterior X-taping (PXT) and real-time external feedback (RTF) on kinematic and electromyographic indices of the lower extremities during the single-leg squat task in individuals with TFRV. Methods Electromyographic and kinematic information of the lower extremities of 24 recreational athletes with TFRV (PXT=12, RTF=12) were recorded while participants in both groups performed single-leg squat 5 times consecutively and took a 2-minute rest between two different conditions (before and after the intervention). To analyze the data, 2-way analysis of variance and Bonferroni post hoc test were used at the significant level of P≤0.05. Results The present study results indicated an increase in gluteus medius muscle activity (P=0.013) in the eccentric phase and a decrease in hip adduction (P=0.001) in maximal knee flexion (P=0.034) after the intervention compared to before the intervention in the RTF group. Also, there was a reduction in external tibiofemoral rotation of the knee after the intervention compared to before intervention in maximal knee flexion (P=0.034), eccentric phase (P=0.001), and concentric phase (P=0.001) in the PXT group. In addition, there was a decreased ankle pronation after the intervention compared to before the intervention in the eccentric phase (P=0.001) and concentric (P=0.001) in the PXT group and in the eccentric phase (P=0.004) in the RTF group. Besides, there was an increased ankle abduction after the intervention compared to before the intervention in the concentric phase (P=0.001), eccentric phase (P=0.001), and maximum knee flexion (P=0.004) in the PXT group, and in the eccentric phase in the RTF group (P=0.006). Finally, there was a decrease in ankle flexion dorsiflexion at maximum knee flexion after the intervention compared to before the intervention (P=0.017) in the RTF group. Conclusion The results of the present study showed that PXT and RTF interventions can affect the kinematic parameters of individuals with TFRV malalignment in different ways and can be used to correct immediately postural defects during the single-leg squat task.

Measurement of TT-TG can change with sequential MRIs due to variations in tibiofemoral rotation in patellofemoral instability patients.

There are various anatomic risk factors for patellofemoral instability (PFI) that help guide surgical treatment, including the tibial tubercle to trochlear groove (TT-TG) distance. However, no study has analysed the temporal changes in TT-TG prior to surgical intervention. This study sought to understand the variations in TT-TG over time for pediatric patients suffering from PFI prior to surgical intervention. The authors hypothesised that the TT-TG would substantially change between time points. Patients undergoing medial patellofemoral ligament (MPFL) reconstruction between 2014 and 2019 by one of two fellowship-trained orthopaedic surgeons were identified. Patients were included if they had two preoperative magnetic resonance imaging (MRI) performed on the same knee within 7.5 months of each other prior to any surgical intervention and had an initial TT-TG greater than 10 mm. After considering 251 patients for inclusion, 21 patients met the final inclusion criteria. The mean age was 14.5 ± 2.5 years and 61.9% were female. TT-TG was initially noted to be 15.1 ± 1.8 mm. At mean time aftersequential MRIs of 5.0 ± 1.9 months, TT-TG was noted to be 16.7 ± 3.2 mm. The differences between initial and subsequent TT-TG ranged from a 21.2% decrease to a 61.1% increase, with a mean difference of an 11.3% increase. Comparison between initial and subsequent TT-TG values demonstrated a significant difference (p = 0.017). Change in tibiofemoral rotation ranged from -9.2° to 7.5°. When comparing the change in TT-TG to change in tibiofemoral rotation, a significant correlation was found (p = 0.019). Despite only a mean time between MRIs of 5 months, variations in TT-TG ranged from a decrease of 21.2% to an increase of 61.1%. The significant relationship between the changes in TT-TG and changes in tibiofemoral rotation between MRIs suggest that TT-TG measurements may vary due to variations in tibiofemoral rotation at the time of individual MRIs. Level IV.

Intraoperative Kinematics in Posterior Cruciate Ligament Retaining Total Knee Arthroplasty Using Different Inserts.

We analyzed the intraoperative kinematics of total knee arthroplasty (TKA) using a navigation system to investigate the influence of different inserts on kinematics. This was a retrospective observational study. The Vanguard individualized design (33 patients, 33 knees) XP and anterior-stabilized (AS) inserts were used in TKA for osteoarthritis. Kinematic data were intraoperatively recorded. The range of motion, tibiofemoral rotational angle, anteroposterior translation of the femur, and varus-valgus laxity were compared between the two inserts (XP vs. AS). There was no significant difference in the range of motion (extension: XP, 3.7° ± 3.3° vs. AS, 3.8° ± 3.3°, p = 0.84; flexion: XP, 138.1° ± 10.2° vs. AS, 139.0° ± 13.3°, p = 0.73). With the AS insert, the tibia was gradually internally rotated as the knee was flexed. At maximum extension, the internal rotation was smallest with AS (XP 6.5° ± 4.0° vs. AS 5.1° ± 3.4°, p = 0.022), which was also associated with smaller anterior femoral translation (maximum extension: XP, 14.1 ± 4.8 mm vs. AS, 11.3 ± 4.7 mm, p = 0.00036; 30°: XP, 23.7 ± 5.6 mm vs. AS, 20.7 ± 5.1 mm, p = 0.000033; 45°: XP, 24.4 ± 4.9 mm vs. AS, 23.2 ± 4.5 mm, p = 0.0038). The AS was associated with a lower varus-valgus laxity (30° XP 4.1° ± 3.4 vs. AS 3.3° ± 2.7°, p = 0.036; 60°: XP, 3.2° ± 3.0° vs. AS, 2.4° ± 3.3°, p = 0.0089). The AS insert facilitated sequential tibiofemoral rotation with varus-valgus stability in mid-flexion without restricting the range of motion.

QUANTIFICATION OF THE ACCURACY OF IN VIVO TIBIOFEMORAL KINEMATICS CALCULATED USING MAGNETIC RESONANCE IMAGING AND BIPLANE VIDEO X-RAY

AbstractObjectivesInvestigate Magnetic Resonance Imaging (MRI) as an alternative to Computerised Tomography (CT) when calculating kinematics using Biplane Video X-ray (BVX) by quantifying the accuracy of a combined MRI-BVX methodology by comparing with results from a gold-standard bead-based method.MethodsWritten informed consent was given by one participant who had four tantalum beads implanted into their distal femur and proximal tibia from a previous study. Three-dimensional (3D) models of the femur and tibia were segmented (Simpleware Scan IP, Synopsis) from an MRI scan (Magnetom 3T Prisma, Siemens). Anatomical Coordinate Systems (ACS) were applied to the bone models using automated algorithms1. The beads were segmented from a previous CT and co-registered with the MRI bone models to calculate their positions. BVX (60 FPS, 1.25 ms pulse width) was recorded whilst the participant performed a lunge. The beads were tracked, and the ACS position of the femur and tibia were calculated at each frame (DSX Suite, C-Motion Inc.). The beads were digitally removed from the X-rays (MATLAB, MathWorks) allowing for blinded image-registration of the MRI models to the radiographs. The mean difference and standard deviation (STD) between bead-generated and image-registered bone poses were calculated for all degrees of freedom (DOF) for both bones. Using the principles defined by Grood and Suntay2, 6 DOF kinematics of the tibiofemoral joint were calculated (MATLAB, MathWorks). The mean difference and STD between these two sets of kinematics were calculated.ResultsThe absolute mean femur and tibia ACS position differences (Table 1) between the bead and image-registered poses were found to be within 0.75mm for XYZ, with all STD within ±0.5mm. Mean rotation differences for both bones were found to be within 0.2º for XYZ (Table 1). The absolute mean tibiofemoral joint translations (Table 1) were found to be within ±0.7mm for all DOF, with the smallest absolute mean in compression-distraction. The absolute mean tibiofemoral rotations were found to be within 0.25º for all DOF (Table 1), with the smallest mean was found in abduction-adduction. The largest mean and STD were found in internal-external rotation due to the angle of the X-rays relative to the joint movement, increasing the difficulty of manual image registration in that plane.ConclusionThe combined MRI-BVX method produced bone pose and tibiofemoral kinematics accuracy similar to previous CT results3. This allows for confidence in future results, especially in clinical applications where high accuracy is needed to understand the effects of disease and the efficacy of surgical interventions. Acknowledgements: This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) doctoral training grant (EP/T517951/1).Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Does Rotation and Anterior Translation Persist as Residual Instability in the Knee after Anterior Cruciate Ligament Reconstruction? (Evaluation of Coronal Lateral Collateral Ligament Sign, Tibial Rotation, and Translation Measurements in Postoperative MRI).

Purpose: The aim of this study was to evaluate the presence of residual instability in the knee after ACL reconstruction through the analysis of MRI findings. Methods: This study included patients who underwent isolated ACL reconstruction between December 2019 and December 2021, and had preoperative and postoperative MRI, clinical scores, and postoperative isokinetic measurements. The anterior tibial translation (ATT) distance, coronal lateral collateral ligament (LCL) sign, and femorotibial rotation (FTR) angle were compared preoperatively and postoperatively. The correlation between the changes in preoperative-postoperative measurements and postoperative measurements with clinical scores and isokinetic measurements was examined. The clinical outcomes were compared based on the presence of a postoperative coronal LCL sign. Inclusion criteria were set as follows: the time between the ACL rupture and surgery being 6 months, availability of preoperative and postoperative clinical scores, and objective determination of muscle strength using isokinetic dynamometer device measurements. Patients with a history of previous knee surgery, additional ligament injuries other than the ACL, evidence of osteoarthritis on direct radiographs, cartilage injuries lower limb deformities, and contralateral knee injuries were excluded from this study. Results: This study included 32 patients. After ACL reconstruction, there were no significant changes in the ATT distance (preoperatively: 6.5 ± 3.9 mm, postoperatively: 5.7 ± 3.2 mm) and FTR angle (preoperatively: 5.4° ± 2.9, postoperatively: 5.2° ± 3.5) compared to the preoperative measurements (p > 0.05). The clinical measurements were compared based on the presence of a postoperative coronal LCL sign (observed in 17 patients, not observed in 15 patients), and no significant differences were found for all parameters (p > 0.05). There were no observed correlations between postoperative FTR angle, postoperative ATT distance, FTR angle change, and ATT distance change values with postoperative clinical scores (p > 0.05). Significant correlations were observed between the high strength ratios generated at an angular velocity of 60° and a parameters FTR angle and ATT distance (p-values: 0.028, 0.019, and r-values: -0.389, -0.413, respectively). Conclusions: Despite undergoing ACL reconstruction, no significant changes were observed in the indirect MRI findings (ATT distance, coronal LCL sign, and FTR angle). These results suggest that postoperative residual tibiofemoral rotation and tibial anterior translation may persist; however, they do not seem to have a direct impact on clinical scores. Furthermore, the increase in tibial translation and rotation could potentially negatively affect the flexion torque compared to the extension torque in movements requiring high torque at low angular velocities.

Increased TT-TG distance caused by excessive tibiofemoral rotation predicts poor clinical outcomes after tibial tubercle osteotomy in recurrent patellar dislocation.

To compare clinical outcome between recurrent patellar dislocation (RPD) with or without actual tibial tubercle lateralisation (TTL) after medial patellofemoral ligament reconstruction (MPFL-R) combined with tibial tubercle transfer. From 2015 to 2018, a total of 172 knees with RPD and a tibial tubercle-trochlear groove (TT-TG) distance of > 20 mm were treated with MPFL-R combined with tibial tubercle transfer. Patients were divided into the lateralisation group (TT-PCL > 24 mm, n = 74) and the nonlateralisation group (TT-PCL ≤ 24 mm, n = 60) based on the presence or absence of actual TTL (TT-PCL > 24 mm). Clinical outcomes were assessed postoperatively at a minimum of 2 years. Second-look arthroscopic evaluations were available for 84 knees to assess cartilage damage. A total of 134 knees with a median follow-up time of 32 months were included. Tibiofemoral rotation (TFR) was significantly higher in the nonlateralisation group than in the lateralisation group (15.4° vs. 9.4°, P < 0.001). At the final follow-up, the nonlateralisation group had significantly lower Kujala (78.2 vs. 86.4, P = 0.001) and Lysholm (80.3 vs. 88.2, P = 0.003) scores than the lateralisation group. At the time of the second-look arthroscopic assessment, 38.9% of the patients in the nonlateralisation group showed cartilage worsening in the medial patellar facet that was significantly higher than that in the lateralisation group (38.9% vs. 12.5%, P = 0.015). Patients with RPD and an increased TT-TG distance of > 20 mm but without actual tibial tubercle lateralisation benefit less from tibial tubercle transfer than patients with actual tibial tubercle lateralisation, which may be related to the significantly higher tibiofemoral rotation angle of the former. III.

Bone morphology features associated with knee kinematics may not be predictive of ACL elongation during high-demand activities.

Bony morphology has been proposed as a potential risk factor for anterior cruciate ligament (ACL) injury. The relationship between bony morphology, knee kinematics, and ACL elongation during high-demand activities remains unclear. The purpose of this study was to determine if bone morphology features that have been associated with ACL injury risk and knee kinematics are also predictive of ACL elongation during fast running and double-legged drop jump. Nineteen healthy athletes performed fast running and double-legged drop jump within a biplane radiography imaging system. Knee kinematics and ACL elongation were measured bilaterally after using a validated registration process to track bone motion in the radiographs and after identifying ACL attachment sites on magnetic resonance imaging (MRI). Bony morphological features of lateral posterior tibial slope (LPTS), medial tibial plateau (MTP) depth, and lateral femoral condyle anteroposterior width (LCAP)/lateral tibial plateau anteroposterior width (TPAP) were measured on MRI. Relationships between bony morphology and knee kinematics or ACL elongation were identified using multiple linear regression analysis. No associations between bony morphology and knee kinematics or ACL elongation were observed during fast running. During double-legged drop jump, a greater range of tibiofemoral rotation was associated with a steeper LPTS (β = 0.382, p = 0.012) and a deeper MTP depth (β = 0.331, p = 0.028), and a greater range of anterior tibial translation was associated with a shallower MTP depth (β = -0.352, p = 0.018) and a larger LCAP/ TPAP (β = 0.441, p = 0.005); however, greater ACL elongation was only associated with a deeper MTP depth (β = 0.456, p = 0.006) at toe-off. These findings indicate that observed relationships between bony morphology and kinematics should not be extrapolated to imply a relationship also exists between those bone morphology features and ACL elongation during high-demand activities. These new findings deepen our understanding of the relationship between bony morphology and ACL elongation during high-demand activities. This knowledge can help identify high-risk patients for whom additional procedures during ACL reconstruction are most appropriate.

Multi-Planar Expansion of the Coronal Plane Alignment of the Knee Classification? A Computed Tomographic Study Indicates No Significant Correlation With Alignment Parameters in Other Planes

BackgroundThe Coronal Plane Alignment of the Knee (CPAK) classification categorizes knee phenotypes based on constitutional limb alignment (arithmetic hip-knee-ankle angle or aHKA) and joint line obliquity (JLO). This study aimed to determine if sagittal and rotational knee alignments vary among CPAK types in order to establish whether this classification should be expanded beyond coronal plane assessment. MethodsCoronal, sagittal, and rotational alignment measurements were made and CPAK types were calculated from computed tomographic data of 437 patients (509 knees) who underwent robotic-assisted total knee arthroplasty (TKA). Differences in femoral, tibial, and tibio-femoral angular measurements were compared across CPAK types, and correlations were made to aHKA and JLO. Nonparametric and linear regression tests were used to analyze between-type differences. ResultsThere were no differences in tibial slope or femoral rotational measures across CPAK phenotypes. However, CPAK Type III knees had a greater tibio-femoral rotation mean difference than CPAK Type I, II, IV, and V knees (P < .05). We also found increased femoral flexion in Type I knees when compared to Type VI knees (P = .01). The aHKA had a weak correlation with femoral flexion angle, and JLO had a weak correlation with femoral posterior condylar axis to tibial antero-posterior axis angle. ConclusionFew clinically important differences in sagittal and rotational alignments were found between CPAK types, indicating that CPAK phenotype has little correlation to 3-dimensional alignment characteristics. Need for an expansion of the CPAK classification beyond coronal plane alignment is not supported from these results.

Effect of Tibiofemoral Rotation Angle on Graft Failure After Anterior Cruciate Ligament Reconstruction

Background: Coronal and sagittal malalignment of the knee are well-recognized risk factors for failure after anterior cruciate ligament (ACL) reconstruction (ACLR). However, the effect of axial malalignment on graft survival after ACLR is yet to be determined. Purpose: To evaluate whether increased tibiofemoral rotational malalignment, namely, tibiofemoral rotation angle (TFA) and tibial tubercle–trochlear groove (TT-TG) distance, is associated with graft failure after ACLR. Study Design: Cohort study; Level of evidence, 3. Methods: In this retrospective matched control study of a single center’s database, 151 patients who underwent revision ACLR because of graft failure (ACLR failure group, defined as symptomatic patients with anterior knee instability and an ACL graft tear appreciated on magnetic resonance imaging [MRI] and confirmed during arthroscopic surgery) were compared with a matched control group of 151 patients who underwent primary ACLR with no evidence of failure after ≥2-year follow-up (intact ACLR group). Patients were matched by sex, age, and meniscal injury during primary ACLR. Axial malalignment was assessed on preoperative MRI through the TFA and the TT-TG distance. Sagittal alignment was measured through the posterior tibial slope on MRI. The optimal TFA cutoff associated with graft failure was identified by a receiver operating characteristic curve. The Kaplan-Meier curve with log-rank analysis was performed to evaluate the influence of the TFA on ACLR longevity. Results: The mean age was 25.7 ± 10.4 years for the ACLR failure group and 25.9 ± 10.0 years for the intact ACLR group. Among all the included patients, 174 (57.6%) were male. In the ACLR failure group, the mean TFA was 5.8°± 4.5° (range, −5° to 16°), while it was 3.0°± 3.3° (range, −3° to 15°) in the intact ACLR group (P < .001). Neither the TT-TG distance nor the posterior tibial slope presented statistical differences between the groups. The receiver operating characteristic curve suggested an optimal TFA cutoff of 4.5° for graft failure (area under the curve = 0.71; P < .001; sensitivity, 68.2%; specificity, 75.5%). Considering this a threshold, patients who had a TFA ≥4.5° had 6.6 times higher odds of graft failure compared with patients with a TFA <4.5° (P < .001). Survival analysis demonstrated a 5-year survival rate of 81% in patients with a TFA <4.5°, while it was 44% in those with a TFA ≥4.5° (P < .001). Conclusion: An increased TFA was associated with increased odds of ACLR failure when the TFA was ≥4.5°. Measuring the TFA in patients with ACL tears undergoing reconstruction may inform the surgeon about additional factors that may require consideration before ACLR for a successful outcome.

Poster 285: MRI Measurement of TT-TG Can Change Without Intervention: An Analysis of Sequential Pre-Operative MRIs in PFI patients

Objectives: Following a patella dislocation event, the patella can remain unstable, leading to patellofemoral instability (PI). There are various anatomic risk factors for PI that help guide surgical treatment including the tibial tubercle to trochlear groove (TT-TG) distance. However, to the authors knowledge, no study has analyzed the temporal changes in TT-TG prior to any surgical intervention. This study, therefore, sought to understand the variations in TT-TG for pediatric patients suffering from patellar instability prior to any surgical intervention. The authors hypothesized that the TT-TG would not substantially change between timepoints. Methods: Patients undergoing medial patellofemoral ligament (MPFL) reconstruction using CPT code 27427 between January 1, 2014 and December 31, 2019 by one of two orthopedic surgeons were identified. Patients were included if they 1) had two pre-operative MRIs performed of the same knee within 8 months of each other prior to any surgical intervention and 2) had an initial TT-TG between 10 mm and 20 mm. Exclusion criteria were previous ipsilateral knee surgery or planned MPFL reconstruction with tibial tubercle osteotomy. Initial and subsequent TT-TG measurements were compared using paired-samples t-tests with two-tailed statistical significance set at p ≤0.05. IBM SPSS Statistics version 22 (Armonk, NY) was used for all statistical analysis. Results: After considering 251 patients for inclusion, 26 patients met inclusion criteria and were analyzed. Mean age of the cohort was 14.5±2.4 years and 42.3% were male. TT-TG was initially noted to be 15.3±1.8 mm. At mean time between sequential MRI’s of 4.8±1.9 months, TT-TG was noted to be 17.1±3.5 mm. The differences between initial and subsequent TT-TG ranged from a 21% decrease to a 61% increase, with a mean difference of a 12.1% increase. Comparison between initial and subsequent TT-TG values demonstrated a significant difference (p=0.006). Conclusions: At a mean time between MRIs of 4.8 months, variations in TT-TG ranged from a decrease of 21% to an increase of 61%. These findings suggest that TT-TG measurements may vary in patients on sequential MRIs and could be due to variations in tibiofemoral rotation during imaging. Surgeons should be aware of these variations when planning surgical correction for patellar instability. [Table: see text]

Poster 316: Increased tibiofemoral rotation angle is associated with graft failure after anterior cruciate ligament reconstruction

Objectives: Coronal and sagittal malalignment of the knee are well-recognized risk factors for failure after anterior cruciate ligament reconstruction (ACLR). However, the effect of axial malalignment on ACLR graft survival is yet to be determined. This study aimed to evaluate whether increased tibiofemoral rotational malalignment, namely tibiofemoral rotation angle (TFA) and tibial tubercle-trochlear groove (TT-TG) distance, is associated with ACLR graft failure. Methods: In this matched-control study, 151 patients who underwent revision ACLR due to graft failure (failure ACLR group) were compared to a matched-control group of 151 patients who underwent primary ACLR with no evidence of failure after at least 2-years follow-up (intact ACLR group). Patients were matched by sex, age, and meniscal injury during primary ACLR. Axial malalignment was assessed on preoperative magnetic resonance imaging (MRI) through the TFA and the TT-TG distance. Sagittal alignment was measured through posterior tibial slope (PTS) on MRI. Optimal TFA cutoff associated with graft failure was identified by a receiver operating characteristic (ROC) curve. Kaplan-Meier curve with log-rank analysis was performed to evaluate the influence of TFA on ACLR longevity. Results: In the failure ACLR group, mean TFA was 5.8 ± 4.5 (range, -5 to 16) degrees while this mean was 3.0 ± 3.3 (range, -3 to 15) degrees in the intact ACLR group (p&lt;0.001). Neither TT-TG distance nor PTS presented statistical differences between the groups. ROC curve suggested an optimal TFA cutoff of 4.5 degrees for ACLR graft failure. Considering this as a threshold, patients who presented TFA ≥ 4.5 degrees had 6.6-times higher likelihood of graft failure compared to patients with TFA &lt; 4.5 degrees (p&lt;0.001). Survival analysis demonstrated a 5-years survival of 81% in patients with TFA &lt; 4.5 degrees, while it was 44% when TFA ≥ 4.5 degrees (p&lt;0.001). Conclusions: Increased TFA was associated with increased odds of ACLR failure when the TFA was ≥ 4.5 degrees. Measuring the TFA in patients with ACL tears undergoing reconstruction may inform the surgeon about additional factors that may require consideration prior to ACL reconstruction for a successful outcome.

Increased Tibiofemoral Rotation Angle is Associated With Graft Failure After Anterior Cruciate Ligament Reconstruction

Increased Tibiofemoral Rotation Angle is Associated With Graft Failure After Anterior Cruciate Ligament Reconstruction