Aims. We aimed to assess the reliability and validity of OpenPose, a posture estimation algorithm, for measurement of knee range of motion after total knee arthroplasty (TKA), in comparison to radiography and goniometry. Methods. In this prospective observational study, we analyzed 35 primary TKAs (24 patients) for knee osteoarthritis. We measured the knee angles in flexion and extension using OpenPose, radiography, and goniometry. We assessed the test-retest reliability of each method using intraclass correlation coefficient (1,1). We evaluated the ability to estimate other measurement values from the OpenPose value using linear regression analysis. We used intraclass correlation coefficients (2,1) and Bland–Altman analyses to evaluate the agreement and error between radiography and the other measurements. Results. OpenPose had excellent test-retest reliability (intraclass correlation coefficient (1,1) = 1.000). The R. 2. of all regression models indicated large correlations (0.747 to 0.927). In the flexion position, the intraclass correlation coefficients (2,1) of OpenPose indicated excellent agreement (0.953) with radiography. In the extension position, the intraclass correlation coefficients (2,1) indicated good agreement of OpenPose and radiography (0.815) and moderate agreement of goniometry with radiography (0.593). OpenPose had no systematic error in the flexion position, and a 2.3° fixed error in the extension position, compared to radiography. Conclusion. OpenPose is a reliable and valid tool for measuring flexion and extension positions after TKA. It has better accuracy than goniometry, especially in the extension position. Accurate measurement values can be obtained with low error, high reproducibility, and no contact, independent of the examiner’s skills. Cite this article: Bone Joint Res 2023;12(5):313–320

Knee injuries in cyclists are often thought to result from an imbalance of load during the cycling motion as a consequence of inappropriate bike set-up. Recently, it has been postulated that incorrect foot positioning may be a significant factor in lower limb injury and poor cycling performance. The purpose of this study is to assess the effect of changing the foot position at the shoe-pedal interface on Vastus Medialis (VM) and Vastus Lateralis (VL) activity (mean and mean peak), knee angle and knee displacement. Maximum power tests were completed on a first visit, with data collection on a second visit recorded at 60% of the subjects maximum. Video footage and surface electromyography (SEMG) from VM and VL muscles was obtained. Data was recorded over 10 crank cycles in 3 experimental conditions; neutral, 10 degrees inversion and 10 degrees eversion using Ethylene Vinyl Acetate (EVA) wedges fitted between the cyclists shoe and the shoe cleat. Raw data (mean SEMG, mean peak SEMG) was obtained using Noraxon and SiliconCOACH measured knee angle and knee displacement. Data was analyzed using Friedmans test with appropriate post hoc tests. 12 male subjects (range 26-45, mean 35.9 years) completed the study. Mean and mean peak SEMG data showed no significant differences between the 3 experimental conditions for VM and VL. VM:VL ratios from raw mean SEMG data demonstrated a decrease in synchronicity in inversion and eversion compared to neutral. Pronators demonstrated most synchronicity in inversion and least synchronicity in eversion. There were statistically significant differences in knee angle and knee displacement between neutral, inversion and eversion (p<0.05). Inversion promoted smaller knee valgus angles and greater knee displacement from the bike. Eversion promoted larger knee valgus angles and a smaller displacement from the bike. By altering the foot position to either 10 degrees inversion or 10 degrees eversion, knee angle and knee displacement can be significantly influenced. Clinically, subjects who foot type is classified as pronating may benefit from some degree of forefoot inversion posting. Further research on subjects with knee pain needs to be undertaken

Introduction. The influences of posterior tibial slope on the knee kinematics have been reported in both TKA and UKA. We hypothesized the posterior tibial slope (PTS) would affect the sagittal knee alignment after UKA. The influences of PTS on postoperative knee extension angle were investigated with routine lateral radiographies of the knee after UKA. Materials & Methods. Twenty-four patients (26 knees; 19 females, 7 males) underwent medial UKA were involved in this study. Average age was 74.8 ± 7.2 years. The mean preoperative active range of motion were − 4.1° ± 6.3°in extension and 123.2° ± 15.5° in flexion. All UKAs were performed using fixed bearing type UKA (Zimmer Biomet, ZUK), with adjusting the posterior slope of the proximal tibial bone cut according to the original geometry of the tibia. Routine lateral radiographies of the knee were examined preoperatively, 6 months after the surgery. PTS and knee extension angles with maximal active knee extension (mEXT) and one-leg standing (sEXT) were radiographically measured. We used the fibular shaft axis (FSA) for the sagittal mechanical axis of the tibia. PTS was defined as the angle between the medial tibial plateau and the perpendicular axis of FSA. Extension angles (mEXT and sEXT) were defined as the angles between FSA and distal femoral shaft axis (positive value for hyperextension). The changes of PTS and the influences of PTS on sEXT at each time period were analyzed using simple linear regression analysis (p<0.05). Results. The mean PTSs were 10.0° ± 3.0° and 9.9° ± 2.7° preoperatively, 6m after surgery respectively. The mean mEXTs were −4.1° ± 6.3° and −2.0° ± 5.4°, and sEXTs were −9.4° ± 7.6° and −7.3° ± 6.7° at each time period. Preoperative and postoperative PTS had positive correlation (r = −0.65). PTS significantly negatively correlated to sEXT at 6 months after the surgery (r = −0.63). Discussions. We found patient tended to stand with slight knee flexion (sEXT) which was smaller than the flexion contracture measured by mEXT. Interestingly, postoperative PTS significantly correlated to the knee flexion angle during one-leg standing. Patients with the higher PTS after UKA were more likely to stand with the higher knee flexion. The higher PTS had been reported to increase tibial anterior translation and strain or tear of the anterior cruciate ligament with load bearing in the normal knee. Slight knee flexion during one-leg standing would be beneficial to keep the joint surface parallel to the ground depending on PTS and reduce the anterior shearing force on the tibia after UKA. Conclusion. Postoperative posterior tibial slope reduced knee extension angle during one-leg standing after UKA. For any figures or tables, please contact authors directly

The aim is to investigate if there is a relation between patellar height and knee flexion angle. For this purpose we retrospectively evaluated the radiographs of 500 knees presented for a variety of reasons.

We measure knee flexion angle using a computer-generated goniometer. Patellar height was determined using computer generated measurement for the selected ratios, namely, the Insall–Salvati (I/S), Caton–Deschamps (C/D) and Blackburne–Peel (B/P) indices and Modified I/S Ratio.

A search of an NHS hospital database was made to identify the knee x rays for patients who were below the age of forty. A senior knee surgeon (DC) supervised three trainee trauma and orthopaedics doctors (HA, JM, ES) working on this research. Measurements were made on the Insall–Salvati (I/S), Caton–Deschamps (C/D) and Blackburne–Peel (B/P) indices and Modified I/S Ratio. The team leader then categorised the experimental measurement of patients’ knee flexion angle into three groups. This categorisation was according to the extent of knee flexion. The angles were specifically, 10.1 to 20, 20.1 to 30, and 30.1 to 40 degrees of knee flexion.

Out of the five-hundred at the start of the investigation, four hundred and eighteen patients were excluded because they had had either an operation on the knee or traumatic fracture that was treated conservatively.

Background: The influence of the knee angle on plantarflexion moments after Achilles tendon repair has yet to be analyzed. It was hypothesized that flexion of the knee joint will disproportionately influence isometric plantarflexion moments after Achilles tendon repair. Methods: Isometric plantarflexion moments and functional heel rise performance were retrospectively assessed in 32 patients at a mean follow-up of 36.9 (±17.83) months after open or percutaneous repair of acute Achilles tendon rupture. Plantarflexion moments were measured with the knee joint in 0, 30, and 60 degrees of flexion and the ankle joint positioned in neutral, 15 degrees plantar flexion and 15 degrees dorsiflexion. Data were compared between the involved and the noninvolved leg as well as between open and percutaneous repair. Results: Flexion of the knee had no significant effect on isometric plantarflexion moments in either the involved or the noninvolved leg, while at any knee angle, plantarflexion moments decreased from dorsiflexion to plantar flexion. In accordance, dynamic heel rise performance revealed no significant strength deficits between the involved and the noninvolved limb. No overall differences in plantarflexion strength were observed between open and percutaneous Achilles tendon repair. Conclusions: The flexion angle of the knee had no influence on plantarflexion moments when comparing the involved with the noninvolved leg after open or percutaneous Achilles tendon repair. Weakness of plantarflexion after open or percutaneous Achilles tendon repair is determined by the position of the ankle joint rather than by the flexion angle of the knee

INTRODUCTION

Measurement of range of motion is a critical item of any knee scoring system. Conventional measurements used in the clinical settings are not as precise as required. Smartphone technology using either inclinometer application or photographic technology may be more precise with virtually no additional cost when compared to more sophisticated techniques such as gait analysis or image analysis. No comparative analysis between these two techniques has been previously performed. The goal of the study was to compare these two technologies to the navigated measurement considered as the gold standard.

Introduction / Purpose

Many factors can influence postoperative knee flexion angle after total knee arthroplasty (TKA), and range of flexion is one of the most important clinical outcomes. Although many studies have reported that postoperative knee flexion is influenced by preoperative clinical conditions, the factors which affect postoperative knee flexion angle have not been fully elucidated. As appropriate soft-tissue balancing as well as accurate bony cuts and implantation has traditionally been the focus of TKA success, in this study, we tried to investigate the influence of intraoperative soft-tissue balance on postoperative knee flexion angle after cruciate-retaining (CR) TKA using a navigation system and offset-type tensor.

INTRODUCTION

The magnitude of knee flexion angle is a relevant information during clinical examination of the knee, and this item is a significant part of every knee scoring system. It is generally performed by visual analysis or with manual goniometers, but these techniques may be neither precise nor accurate. More sophisticated techniques are only possible in experimental studies. Smartphone technology might offer a new way to perform this measurement with increased accuracy.

A prospective clinical investigation to determine the optimum knee flexion angle for the ‘skyline’ patellofemoral joint radiograph.

Plain radiography of the patello-femoral joint includes the axial or ‘skyline’ radiograph. The optimum knee flexion angle for making this image remains unclear.

We therefore performed a prospective clinical study in which patients underwent three skyline radiographs with knee flexion angles of 30(or minimal flexion), 50 and 90 degrees. The patients were new patients, aged between 12 and 30, presenting to a knee clinic with anterior knee pain. Two observers evaluated the radiographs, making a standardised series of measurements. Blinding was organised so that the observers were unable to use any information other than the radiographic image alone. One observer evaluated all the films on two separate occasions to allow calculation of intra- and interassessor agreement.

There were 67 knees from 46 patients. There was a high level of intra- and inter-observer agreement. There were a number of patients in which the radiographic appearance of the patello-femoral varied markedly between the different views; in all cases the abnormality was best demonstrated by the 30-degree view. There were however a number of minimal flexion views in which the film contained incomplete information because part of the patello-femoral joint was missing from the image.

We conclude that whilst a minimal flexion skyline view is the most sensitive method for the detection of patellar tilt and subluxation, not all knees can be successfully imaged at the required position. A flexible approach is therefore needed, to obtain satisfactory images at minimal flexion.

Objective

In Total Knee Arthroplasty (TKA), it is important to adjust the difference of the flexion-extension gap (gap difference) to get the good range of motion and the sufficient stability. However the effect of the gap adjustment on the post-operative knee flexion angle(KFA) is unknown. We investigated the relationship between the gap difference and the postoperative KFA improvement rate.

Movement dysfunction resulting in a knee valgus position during weight bearing activity is associated with increased risk of Anterior Cruciate Ligament injury and Patellofemoral Pain Syndrome especially in young active females. In clinical practice determining the critical knee flexion angle (CKFA) during a single leg squat (SLS) test is used to assess this dysfunction, yet its reliability is unknown. This study aimed to determine rater agreement in determining the presence of knee valgus movement (yes/no) during a SLS test in recreational females (n = 16, age 24.3 ±7.9 yrs, height 165.7±4.8m, mass 62.5±6.4kg) and the intra and inter-rater reliability of measuring CKFA using SiliconCoach™. Three experienced physiotherapists viewed 48 randomised SLS test videos. One physiotherapist repeated the viewing for test-retest analysis. Test-retest agreement for rating SLS test was acceptable (weighted kappa (k) = 0.667). Inter-rater agreement was moderate to substantial (weighted k = 0.284–0.613). Intra-rater reliability of CKFA was acceptable for all three raters (ICC>0.6). Inter-rater absolute reliability was below 5% of the mean CKFA (SEM 4.26 degrees). As previous research reports intra-rater agreement is better than inter-rater agreement when assessing movement dysfunction during functional activity via visual rating. Intra-rater within session and between session reliability for measuring the CKFA using SiliconCoach™ was acceptable and better than inter-rater reliability. Further research is needed to assess the concurrent and construct validity of the protocols used in this study. It is recommended that qualitative research be performed to identify factors that affect physiotherapist's rating of functional activities.

Patellofemoral pain syndrome (PFPS) is a common knee disorder in active individuals. Movement dysfunction of valgus positioning at the knee during weight-bearing is frequently seen in PFPS. A single-leg squat (SLS) is a test commonly used in physiotherapy to assess for movement dysfunction. Kinesio-Tape (KT) is gaining in popularity in treating PFPS and claims to alter muscle recruitment and motor control, however evidence is weak. Objective: To evaluate the effect of KT applied to the quadriceps on muscle activity with electromyography (EMG) of the rectus femoris, vastus lateralis and vastus medialis oblique and motor control via the frontal plane projection angle (FPPA) using 2-dimensional video analysis.

A convenience sample of healthy females were recruited and performed 5 single-leg squats with and without KT. EMG of the quadriceps was recorded and dynamic valgus assessed via the FPPA using Dartfish video analysis software. Eccentric and concentric EMG data was recorded and the FPPA measured in single-leg stance and the depth of the squat. Institutional ethical approval was obtained for the study.

16 active females were assessed (mean age 28.94 +6.58 years). Wilcoxon signed-rank tests found no significant change in eccentric or concentric EMG of the quadriceps (%MVC) with KT compared to without (p values 0.35–0.86). Paired-sample t-tests found no significant difference in FPPA between conditions in single-leg stance (p=1.00) or the depth of the squat (p=0.871).

KT did not affect EMG activity of the quadriceps or the FPPA in a SLS when applied to the quadriceps of healthy females, questioning proposed effects of KT on normal muscle tissue. Further research is required into the efficacy of using KT in physiotherapy.

Abstract. Rehabilitation exercise is critical for patients’ recovery after knee injury or post-surgery. Unfortunately, adherence to exercise is low due to a lack of positive feedback and poor self-motivation. Therefore, it is crucial to monitor their progress and provide supervision. Inertial measurement unit (IMUs) based sensing technology can provide remote patient monitoring functions. However, most current solutions only measure the range of knee motion in one degree of freedom. The current IMUs estimate the orientation-angle based on the integrated raw data, which might lack accuracy in measuring knee motion. This study aims to develop an IMU-based sensing system using the absolute measured orientation-angle to provide more accurate comprehensive monitoring by measuring the knee rotational angles. An IMU sensing system monitoring the knee joint angles, flexion/extension (FE), adduction/abduction (AA), and internal/external (IE) was developed. The accuracy and reliability of FE measurements were validated in human participants during squat exercise using measures including root mean square error (RMSE) and correlation coefficient. The RMSE of the three knee angles (FE, AA, and IE) were 0.82°, 0.26°, and 0.11°, which are acceptable for assessing knee motion. The FE measurement was validated in human participants and showed excellent accuracy (correlation coefficient of 0.99°). Further validation of AA and IE in human participants is underway. The sensing system showed the capability to estimate three knee rotation angles (FE, AA, and IE). It showed the potential to provide comprehensive continuous monitoring for knee rehabilitation exercises, which can also be used as a clinical assessment tool

Introduction and Objective. Gait variability is the amplitude of the fluctuations in the time series with respect to the mean of kinematic (e.g., joint angles) or kinetic (e.g., joint moments) measurements. Although gait variability increases with normal ageing or pathological mechanisms, such as knee osteoarthritis (OA). The purpose was to determine if a patient who underwent a total knee arthroplasty (TKA) can reduce gait variability. Materials and Methods. Twenty-five patients awaiting TKA were randomly assigned to receive either medial pivot (MP, m=7/f=6, age=62.4±6.2 years) or posterior stabilized (PS, m=7/f=5, age=63.7±8.9 years) implants, and were compared to 13 controls (CTRL, m=7/f=6, age=63.9±4.3 years). All patients completed a gait analysis within one month prior and 12 months following surgery, CTRLs completed the protocol once. A waveform F-Test Method (WFM) was used to compare the variance in knee biomechanics variables at each interval of the gait cycle. Results. Preoperatively, the PS group had greater sagittal knee angle variability compared to the MP (32–58% gait cycle) and CTRL (21–53% gait cycle) groups. Postoperatively, no difference in sagittal knee angle variability existed between any of the groups. Preoperatively, sagittal knee moment variability was greater in the MP (2–39% gait cycle) and PS (5–19% and 42–57% gait cycle) groups compared to the CTRL. Postoperatively, sagittal knee moment was lower in the MP (49–55% gait cycle) and greater in the PS (23–36% gait cycle) compared to the CTRL. Knee power variability was greater preoperatively in the MP (52–61% gait cycle) and PS (52–62% gait cycle) compared to the CTRL. Postoperatively, knee power variability was lower in the MP (17–22% and 45–50% gait cycle) and PS (6–23%, 34–41% and 45–49% gait cycle) compared to the CTRL group. Conclusions. Preoperatively, knee OA patients have greater variability in knee moments than CTRLs during the transition from double-limb support to single-limb support on the affected limb. This indicates knee instability as patients are adopting a gait strategy that refers to knee muscle contraction avoidance. The MP group showed greater knee stability postoperatively as they had lower knee moment and power variability compared to the CTRL. The significance of having less variability than CTRLs is not well understood at this time. Future research on muscle activity is needed to determine if neuromuscular adaptations are causing these reductions in variability after TKA

Identifying and restoring alignment is a primary aim of total knee arthroplasty (TKA). In the coronal plane, the pre-pathological hip knee angle can be predicted using an arithmetic method (aHKA) by measuring the medial proximal tibial angle (MPTA) and lateral distal femoral angle (aHKA=MPTA - LDFA). The aHKA is shown to be predictive of coronal alignment prior to the onset of osteoarthritis; a useful guide when considering a non-mechanically aligned TKA. The aim of this study is to investigate the intra- and inter-observer accuracy of aHKA measurements on long leg standing radiographs (LLR) and preoperative Mako CT planning scans (CTs). Sixty-eight patients who underwent TKA from 2020–2021 with pre-operative LLR and CTs were included. Three observers (Surgeon, Fellow, Registrar) measured the LDFA and MPTA on LLR and CT independently on three separate occasions, to determine aHKA. Statistical analysis was undertaken with Bland-Altman test and coefficient of repeatability. An average intra-observer measurement error of 3.5° on LLR and 1.73° on CTs for MPTA was detected. Inter-observer errors were 2.74° on LLR and 1.28° on CTs. For LDFA, average intra-observer measurement error was 2.93° on LLR and 2.3° on CTs, with inter-observer errors of 2.31° on LLR and 1.92° on CTs. Average aHKA intra-observer error was 4.8° on LLR and 2.82° on CTs. Inter-observer error of 3.56° for LLR and 2.0° on CTs was measured. The aHKA is reproducible on both LLR and CT. CT measurements are more reproducible both between and within observers. The difference between measurements using LLR and CT is small and hence these two can be considered interchangeable. CT may obviate the need for LLRs and may overcome difficulties associated with positioning, rotation, body habitus and flexion contractures when assessing coronal alignment

Anterior cruciate ligament (ACL) ruptures are debilitating injuries, often managed via ACL reconstruction (ACLR). Reduced range of motion (ROM), particularly loss of extension (LOE), is the most significant contributor to post-operative patient dissatisfaction. LOE may preclude return to sport, increase re-rupture rates and precipitate osteoarthritis. Passive LOE rates following ACLR have been reported at 15%. However, LOE incidence during active tasks are poorly characterised. Our review sought to determine knee extension angles for active tasks following an ACL injury or ACLR. We hypothesised greater incidences of active LOE following ACL injury or ACLR, compared to uninjured contralateral limbs or controls. We systematically searched MEDLINE, Embase, Cochrane Library, Scopus, SPORTDiscus, and relevant trials databases for English articles. Included were cohort, cross-sectional, case-controlled or randomised controlled trials analysing adults with ACL injury treated surgically or otherwise, with at least 12-weeks follow-up and reporting either active knee extension angle, active LOE angles or incidence of active knee LOE during functional tasks. The protocol was registered on PROSPERO (CRD42018092295). Subsequent meta-analysis was performed. After screening, 71 eligible articles were included. Studies were heterogenous in design and quality. Included tasks were overground walking (n=44), running (n=3), hopping/jumping/cutting (n=11) single-leg landing (n=7), and stair climbing (n=6). LOE incidence varied depending on functional activities (33.95-92.74%). LOE incidence did not vary depending on ACL status (67.26% vs. 65.90% vs. 62.57% for ACL intact, ACLD and ACLR, respectively). We observed no difference in active LOE incidence according to ACL status. Importantly, the observed incidence for active LOE was reliably higher than previously reported rates for passive measures. Given the discrepancy between active and passive LOE incidence, clinicians may advisably prioritise active ROM during ACL rehabilitation

Previous studies have identified the anterolateral complex (ALC) as having an important role in controlling anterolateral rotatory laxity following anterior cruciate ligament injury and subsequent reconstruction. In particular, injury to the iliotibial band (ITB) and its component deep (dITB) and capsulo-osseous (coITB) layers, have been shown to significantly correlate with different grades of the pivot-shift test in patients with acute ACL injuries. However, the kinematic properties of the capsulo-osseous layer of the ITB, throughout knee range of motion, are not fully understood. The purpose of this study was to quantify the kinematic behaviour of the capsulo-osseous layer of the ITB through various degrees of knee flexion. Ten fresh-frozen cadaveric knee specimens were dissected to expose the capsulo-osseous layer of the iliotibial band. Radiopaque beads were embedded, at standardized increments (12.5%, 25%, 50% and 75% of total length from proximal to distal), into the tissue and fluoroscopic images were taken from 0o to 105o of knee flexion in 15° increments. The positions of the beads were identified in each image and the length, width, and area changes of the capsulo-osseous layer were calculated. Comparisons of the total length of the anterior and posterior borders of the coITB through knee ROM were conducted using a two-way (8 knee angles by 2 borders) repeated measures analysis of variance (rm-ANOVA), whereas the effect of knee angle on isometry and total area changes was assessed using one-way rm-ANOVAs (α=0.05). There was a significant increase in the length of the anterior capsulo-osseous layer at flexion angles greater than 15o and on the posterior border at angles greater than 75 o with changes occurring primarily at 12.5 % of the total length. In addition, at all flexion angles the length changes were significantly larger in the anterior border compared to the posterior border. Meanwhile, non-homogenous decreases in width and area were found with increasing flexion angle. The distance between the capsulo-osseous layer insertion on the distal femur and proximal tibia significantly increased from 60o-105o, maximal changes occurred at 105o (9.64 [4.12] %, p = 0.003). The primary finding of this study was that the coITB behaved in a non-isometric fashion, with significant increases in length occurring at flexion angles greater than 15o. Moreover, these changes in length were non-homogenous across the different regions of the coITB that were investigated, with the greatest changes occurring in the proximal segments (0–25%). The data presented here suggest that coITB in flexion angles from 0o to 105o behaves in a non-isometric fashion, with the majority of its length change occurring in its proximal segment. Further quantification of the pathway that the coITB takes with respect to osseous landmarks may result in improvements in ALC procedures as an augmentation to ACL reconstruction, thereby potentially improving rotational stability and clinical outcomes

Introduction and Objective. Clinically, it is considered that spastic muscles of patients with cerebral palsy (CP) are shortened, and produce higher force in shorter muscle lengths. Yet, direct quantification of spastic muscles’ forces is rare. Remarkably, previous intraoperative tests in which muscle forces are measured directly as a function of joint angle showed for spastic gracilis (GRA) that its passive forces are low, and only a small percentage of its maximum active force is measured in flexed knee positions. However, the relationship of force characteristics of spastic GRA with its muscle-tendon unit length (l. MTU. ) is unknown. Combining intraoperative experiments with participants’ musculoskeletal models developed based on their gait analyses, we aimed to test if spastic GRA muscle (1) operates at short l. MTU. compared to that of typically developing (TD) children, and exerts higher (2) passive and (3) active forces at shorter lengths, within gait-relevant l. MTU. range. Materials and Methods. Ten limbs of seven children with CP (GMFCS-II) were tested. Pre-surgery, gait analyses were conducted. Intraoperatively, isometric spastic GRA distal forces were measured in ten hip-knee joint angle combinations, in two conditions: (i) passive state and (ii) maximal activation of the GRA exclusively. In OpenSim, gait_2392 model was used for each limb to calculate l. MTU. 's per each hip and knee angle combination and the gait-relevant l. MTU. range, and to analyze gait relevant spastic muscle force - l. MTU. data. l. MTU. values were normalized for the participants’ thigh lengths. Two-way ANOVA was used to compare the patients’ l. MTU. to those of the seven age-matched TD children to test the first hypothesis. In order to test the second and the third hypotheses, Spearman's rank correlation coefficient (ρ) was calculated to seek a correlation between the muscle's operational length (represented by mean l. MTU. within gait cycle) and muscular force characteristics (the percent force at shortest l. MTU. of peak force, either in passive or in active conditions) within gait-relevant l. MTU. range. Results. ANOVA showed that l. MTU. 's of spastic GRA are shorter (on average by 15.4%) compared to those of TD. At the shortest gait-relevant l. MTU. , the GRA passive force was 84.6 (13.7)% of the peak passive force; and the active force was 55.8 (33.9)% of the peak active force. Passive state forces show an increase at longer lengths, whereas active state force characteristics vary in a patient-specific way. Spearman's rank correlation indicated weak correlations between muscle's operational length and muscular force characteristics (ρ= −0.30 P= 0.40, and ρ= −0.27 P= 0.45, for passive and active states, respectively). Therefore, only the first hypothesis was confirmed. Conclusions. Novel muscle force - l. MTU. data for spastic GRA were obtained using intraoperative data and modelling combined. The modelling showed in concert with the clinical considerations that spastic GRA may be a shortened muscle. However, because the model does not distinguish the muscle-belly and tendon lengths, it cannot isolate shorter muscle belly length and how this compares to the data of TD children remains unknown. Moreover, the absence of a strong correlation between shorter operational muscle length and higher force production either in passive or in active conditions highlights the influence of other factors (e.g., muscle structural proteins, and muscle mechanical characteristics including intermuscular interactions etc.) on the pathology rather than ascribing it solely to the length of a spastic muscle itself

Background. Spastic muscles of patients with cerebral palsy (CP) are considered structurally as shortened muscles, that produce high force in short muscle lengths. Yet, previous intraoperative studies in which muscles’ forces are measured directly as a function of joint angle showed consistently that spastic knee flexor muscles produce a low percentage of their maximum force in flexed knee positions. They also showed effects of epimuscular myofascial force transmission (EMFT): simultaneous activation of different muscles elevated target muscle's force. However, quantification of spastic muscle's force - muscle-tendon unit length (l. MTU. ) data during gait is lacking. Aim. Combining intraoperative experiments with participants’ musculoskeletal models developed based on their gait analyses, we aimed to test the following hypotheses: activated spastic semitendinosus (ST) muscle (1) operates at short l. MTU. 's during gait, forces are (2) low at short l. MTU. 's and (3) increase by co-activating other muscles. Methods. Ten limbs of seven children with CP (GMFCS-II) were tested. Pre-surgery, gait analyses were conducted. Intraoperatively, isometric spastic ST distal forces were measured in ten hip-knee joint angle combinations, in two conditions: (i) activation of the ST individually and (ii) simultaneously with the gracilis, biceps femoris, and rectus femoris muscles endorsing EMFT. In OpenSim, gait_2392 model was used for each limb to (a) calculate l. MTU. per each hip and knee angle combination and the gait relevant l. MTU. range, and (b) analyze gait relevant spastic muscle force - l. MTU. data. Two-way ANOVA was used to compare the patients’ l. MTU. to those of the seven age-matched typically developing (TD) children. l. MTU. values were normalized for the participants’ thigh length. (a) was used to test hypothesis (1) and (b) to test hypotheses (2) and (3): in condition (i), the percent of peak force exerted at the shortest l. MTU. calculated per limb was used as a metric for (2). In condition (ii), mean percent change in muscle force calculated within gait-relevant l. MTU. range was used as a metric for (3). Results. Modeling showed that l. MTU. of spastic ST during gait is shorter on average by 14.1% compared to TD. The ST active force at the shortest gait-relevant l. MTU. was 68.6 (20.6)% (39.9–99.2%) of the peak force. Simultaneous activation of other muscles caused substantial increases in force (minimally by 11.1%, up to several folds, with an exception for one limb). Therefore, only the first and third hypotheses were confirmed. Conclusion. The modeling showed in concert with the clinical considerations that spastic ST may be a shortened muscle that produces high force in short muscle lengths. However, this contrasts intraoperative data, which shows only low forces in flexed knee positions. Note that, the model does not distinguish the muscle-belly and tendon lengths. Therefore, it cannot isolate shorter muscle length and how this compares to the data of TD children remains unknown. Yet, the effects of co-activation of other muscles shown intraoperatively to cause an increase of the spastic ST's force are observed also in muscle force - l. MTU. data characterizing gait. Therefore, if indeed spastic ST produces high forces in short muscle-belly lengths alone, elevated forces due to co-activation of other muscles may be considered as a contributor to the patients’ pathological gait. Otherwise, such EMFT effect may be the main determinant of the pathological condition

Aims

The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients.