Comparison of knee kinematics and ligament forces in single and multi-radius cruciate-retaining total knee arthroplasty: A computer simulation study

BACKGROUND

The single-radius design in total knee arthroplasty has been designed to develop a more fixed flexion-extension axis without mid-flexion instability compared with the multi-radius design. It remains unclear whether differences between the multi-radius and single-radius designs can affect kinematics and collateral ligament forces. This study aimed to simulate knee kinematics and kinetics between single-radius and multi-radius models using a musculoskeletal computer model.

METHODS

The single-radius and multi-radius femoral components were virtually implanted in a computer simulation using the same tibial insert. The effects of implant design on kinematics and medial collateral ligament forces during squatting and gait activities were analyzed.

RESULTS

During squatting, the multi-radius model exhibited paradoxical anterior translation on both the medial and lateral flexion facet center where peak anterior translation was 2.4 mm for medial flexion facet center and 2.2 mm for the lateral flexion facet center, while the peak anterior translation of the single-radius model was less than 1 mm at early flexion. A rapid decrease in medial collateral ligament tension was observed in the early flexion phase in the multi-radius model, which occurred simultaneously with paradoxical anterior translation, whereas the relatively constant medial collateral ligament tension was observed in the single-radius model. During gait activity, the single-radius model exhibited a more posterior position than the multi-radius model.

CONCLUSION

These suggest that abrupt changes in the medial collateral ligament force influence anterior sliding of the femur, and that the single-radius design is a reasonable choice for prevention of mid-flexion instability.

A Systematic Review on Lower-Limb Industrial Exoskeletons: Evaluation Methods, Evidence, and Future Directions

Industrial tasks that involve frequent sitting/standing transitions and squatting activities can benefit from lower-limb industrial exoskeletons; however, their use is not as widespread as their upper-body counterparts. In this review, we examined 23 articles that evaluated the effects of using Wearable Chair (WC) and Squat-assist (SA) exoskeletons. Evaluations mainly included assessment of muscular demands in the thigh, shank, and upper/lower back regions. Both types of devices were found to lessen muscular demands in the lower body by 30-90%. WCs also reduced low-back demands (~ 37%) and plantar pressure (54-80%) but caused discomfort/unsafe feeling in participants. To generalize outcomes, we suggest standardizing approaches used for evaluating the devices. Along with addressing low adoption through design upgrades (e.g., ground and body supports/attachments), we recommend that researchers thoroughly evaluate temporal effects on muscle fatigue, metabolic rate, and stability of wearers. Although lower-limb exoskeletons were found to be beneficial, discrepancies in experimental protocols (posture/task/measures) were discovered. We also suggest simulating more realistic conditions, such as walking/sitting interchangeability for WCs and lifting loads for SA devices. The presented outcomes could help improve the design/evaluation approaches, and implementation of lower limb wearable devices across industries.

The anatomy of the hindlimb of Theropithecus brumpti (Cercopithecidae, Papionini): Morphofunctional implications

Theropithecus brumpti is a primate known from numerous craniodental specimens in the Plio-Pleistocene Shungura Formation (Lower Omo Valley, Ethiopia), but the anatomy of its hindlimb is documented only by a few associated and mostly incomplete postcranial specimens. The adaptations of T. brumpti are still debated, with its substrate preferences and its use of squatting postures recently discussed based on anatomical differences when compared with its extant representative, Theropithecus gelada. Here, we describe an associated femur and tibia (L 869-1 and L 869-2) of a presumed T. brumpti male and a partial foot (L 865-1r and L 865-1t) of a male T. brumpti, dated to ca. 2.6 Ma and ca. 2.32 Ma respectively. Based on univariate and bivariate morphometric analyses, we provide new data on the morphological correlates of substrate preferences and postural behaviors of this fossil species. Our results are in agreement with previous analyses and present T. brumpti as a predominantly terrestrial primate. We demonstrate the presence of osteological correlates associated with the use of squatting behaviors in T. brumpti but also point to significant anatomical differences between this paleontological species and T. gelada. These differences blur the functional value of characters previously identified as diagnostic of T. gelada and its postural behavior. We further document the postcranial distinctiveness of the Theropithecus clade in relation to the Papio clade. This study thus provides new insights into the postcranial anatomy and paleoecology of an abundant fossil primate from the Plio-Pleistocene of eastern Africa.

The higher patient-reported outcome measure group had smaller external rotation of the femur in bicruciate-stabilized total knee arthroplasty

PURPOSE

The hypothesis of this study was that the kinematics of patients with higher patient-reported outcome measures (PROMs) differ from those of patients with lower PROMs after bicruciate-stabilized total knee arthroplasty (BCS-TKA).

METHODS

A total of 32 patients with severe knee osteoarthritis were examined 11.2 ± 3.2 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. To estimate the spatial position and orientation of the femoral and tibial components, a 2D-to-3D registration technique was used. This technique uses a contour-based registration algorithm, single-view fluoroscopic images and 3D computer-aided design models. Knee range of motion, varus-valgus alignment, axial rotation of the femur relative to the tibial component, anteroposterior translation of the medial and lateral femorotibial contact points, kinematic paths, and anterior and posterior post-cam engagement were measured. The patients were divided into two groups using hierarchical cluster analysis based on the 1-year postoperative Knee Injury and Osteoarthritis Outcome Score and 2011 Knee Society Score.

RESULTS

The femoral component had significantly more external rotation in the low-score group than in the high-score group (5.1 ± 1.8° vs. 2.2 ± 2.7°, p = 0.02). The high-score group had a medial pivot pattern from 0 to 20° of flexion, without significant movement from 20 to 70°, and final bicondylar rollback beyond 70°. The low-score group had a medial pivot from 0 to 70° of flexion and bicondylar rollback beyond 70°. There were no significant between-group differences in the varus-valgus angle or post-cam engagement.

CONCLUSION

The higher PROM group had smaller external rotation of the femur after BCS-TKA.

LEVEL OF EVIDENCE

Level III.

Influence of toileting behavior on the natural course of anterior vaginal wall prolapse

Background

Many risk factors for pelvic organ prolapse (POP) have been proposed, and the cause is most likely multifactorial. This study aimed to investigate the effect of toileting behaviors on the natural course of anterior vaginal wall prolapse (AVWP).

Methods

Data on 75 women who underwent surgery for symptomatic AVWP were collected. Patients with grade ≥ II AVWP were included in this study and were divided into two groups according to their voiding and defecation position. The volunteers who voided and defecated in a sitting position comprised Group 1, and those who voided and defecated in a squatting position comprised Group 2. The Colorectal-Anal Impact Questionnaire (CRAIQ), Pelvic Floor Impact Questionnaire (PFIQ), Pelvic Organ Prolapse Impact Questionnaire (POPIQ), Urinary Impact Questionnaire (UIQ) and visual analog scale (VAS) pain scores were used to evaluate the patients’ symptoms.

Results

Forty-four patients were included in Group 1 (sitting position), and 31 patients were included in Group 2 (squatting position). The groups were similar in terms of BMI, parity, menopause duration, topical estrogen use, comorbidities, the presence of constipation and urinary incontinence, and the pad count for incontinence. The time from initial symptoms to surgery was shorter in Group 2 than in Group 1 12 (3–73) and 24 (2–182) months (p = 0.001), respectively. The PFIQ, POPIQ and POP-related VAS scores were significantly higher in patients who voided and defecated in a squatting position.

Conclusion

In patients with symptomatic POP, increased IAP while performing the squat position during defecation and voiding may increase the severity of patients' symptoms related to prolapse more than that of sitting position. Therefore, questioning the toileting position of patients with AVWP may help inform management decisions, with changing to a sitting position encouraged.

Three-dimensional motion analysis of ten common Asian sitting positions in daily living and factors affect range of hip motions

BACKGROUND

Sitting involves many activities of daily life and requires most motion in the hip joint. Asians have more hip flexion and external rotation motions than Westerners owing to cultural and lifestyle differences. Being aware of the normal range of hip motion is essential in clinical practice. Limited research has focused on the hip motions of common sitting positions. The objective was to determine the hip motions of 10 common sitting positions, and to determine whether gender or being overweight affects the range of hip motions.

METHODS

An experimental cross-sectional study was conducted to determine hip motions by using a standard, three-dimensional, motion-analysis system. Healthy subjects performed 10 sitting positions during 3 trials. All hip-kinematic data were measured on the dominant leg of each participant, except for the right- and left-monk positions (both hips were analyzed). Density plots were constructed and statistical analyses were performed to detect the differences between groups (male and female; non-overweight and overweight).

RESULTS

The 48 participants comprised 24 males and 24 females. Most were right-leg dominant (45 participants, 93.8%). Of the 22 participants in the overweight group (body mass index ≥23 kg/m²), 18 (75%) were male. Squatting showed the highest flexion angle (99.7°, 47.3°-122°). Cross-legged sitting had the highest abduction angle (28.9°, 9.9°-45.7°) and the largest external rotation angle (62°, 37.6°-81.7°). In the female group, there were trends toward a greater flexion angle (4 out of 10 sitting positions) and a smaller abduction angle (6 out of 9 positions), with P values < 0.05. As to body weight, the overweight participants had a smaller flexion angle but a greater abduction angle, with 5 out of 9 positions having a P value < 0.05. Kinematic data of the transverse plane revealed that the heterogeneity of the rotational angles depended on the sitting position.

CONCLUSIONS

This study provided the functional hip motions of common Asian sitting positions. The kinematic data can be utilized in clinical practice as reference values to determine safe positions. Gender and being overweight affected the hip angles in the sagittal and frontal planes.

TRIAL REGISTRATION

Number TCTR20181021004 , retrospectively registered at the Thai Clinical Trials Registry (http//:www.clinicaltrials.in.th).

Determination of outcomes of complex upper end tibial fractures in squatting and cross leg sitting South Asian population

INTRODUCTION

Treatment of complex upper end tibial fractures has always been a challenge to orthopaedic surgeons. Though the roentgenogram results are satisfactory, the clinical and functional outcomes especially in terms of squatting/cross-leg sitting after long term follow-up are little known. Hence, we have done this study with a primary aim to assess the clinico-radiological and functional outcomes after operative fixation (mostly by locking plates) in complex upper end tibial fractures and a secondary aim to analyze correlation between functional outcome scores/range of motion (ROM) and the ability to squat & sit cross-legged in post-operative period.

MATERIALS AND METHODS

This prospective study included a total of 33 patients who were mainly treated with locking plates. In the follow-up, patients were assessed clinico-radiologically and outcome measurements were determined using the Tegner-Lysholm (T-L) Knee Score. Patients were categorized according to their ability to squat/sit cross-legged and a subgroup analysis was performed by comparing mean ROM and T-L score in each group.

RESULTS

Majority of patients were in young and adult age group with a male to female ratio of 4.5:1. The average age was 42.39 ±14.64 years. Road traffic accident was the most common mode of injury. Average time interval between injury and surgery was 5.8±4.4 days. All the fractures united by 5-9 months. Mean ROM and T-L score at last follow-up were 120.94°±13.63° and 88.12±7.24 respectively. Average shortening, varus and valgus deformity were 0.43±0.09 cm, 2.12°±0.62° and 1.06°±0.45° respectively. 14 patients (42.42%) were able to squat and 15 (45.45%) were able to sit cross-legged postoperatively. Upon subgroup analysis, difference of mean ROM in those who could squat/sit cross-legged was found statistically significant (p≤0.05), however the difference in mean functional scores was not significant (p≥0.05).

CONCLUSION

Complex upper tibial fractures are a difficult entity to deal with. Anatomical locking plates take care of the alignment, articular congruity as well as ligamentous balancing thus giving good mid-term outcomes after ORIF/MIPO. However, applicability of the present functional outcome scores in assessing squatting/cross leg sitting remains doubtful. More weightage needs to be given to these activities to evaluate the outcome in South Asian population.

Intraoperative kinematics of bicruciate-stabilized total knee arthroplasty during high-flexion motion of the knee

BACKGROUND

It is unknown whether intraoperative kinematics of bicruciate-stabilized total knee arthroplasty (BCS-TKA) are different for different activities. It has also not been established whether intraoperative high-flexion motions correlate with postoperative patient-reported outcome measures (PROMs). We aimed to clarify the intraoperative kinematics of BCS-TKA during high-flexion activities and describe the relationship between intraoperative and postoperative patient-reported outcomes.

METHODS

We examined 33 knees from 31 patients who underwent BCS-TKA and measured intraoperative knee kinematics, passive knee flexion, and cross-legged flexion using a navigation system. We also calculated knee flexion, varus-valgus, and rotation angles. As a secondary evaluation, we divided the patients into two clusters based on the PROMs and compared the kinematics between them.

RESULTS

The valgus moved by 1.3 ± 1.3° beyond 90° knee flexion during passive flexion. In contrast, during cross-legged flexion, the varus moved by 4.6 ± 5.1° beyond 30° flexion. This indicated significantly increased varus alignment in the cross-legged flexion as compared with passive flexion. Beyond 60° of flexion, the femur displayed 8.8 ± 4.8° of external rotation relative to the tibia. In cross-legged flexion, the femur displayed 9.2 ± 6.5° of external rotation relative to the tibia beyond 45° of flexion. At 90° of flexion, the cross-legged knees rotated more externally. There were no significant postoperative differences between the high- and low-score clusters.

CONCLUSION

The intraoperative knee kinematics after BCS-TKA during high-flexion motions differed depending on the performance of an individual. This will be useful for physicians who might recommend BCS-TKA to new patients.

Squatting position in the second stage of labor: A systematic review and meta-analysis

OBJECTIVES

The influence of squatting during delivery on maternal and fetal outcomes remains unclear. We performed a systematic review and meta-analysis to evaluate the benefits and risks of adopting a squatting position during the second stage of labor.

STUDY DESIGN

Search Strategy: A systematic search in the three major electronic databases (CENTRAL, PubMed and Embase) was performed, from their respective inception dates to the 14th of December 2019, using 'squatting', and a combination of keywords to identify delivery. Eligibility criteria: Randomized controlled trials comparing squatting position to any supine position during the second stage of labor.

STATISTICAL ANALYSES

Risk ratio for dichotomous outcomes, mean difference for continuous outcomes, with 95 % confidence intervals. Fixed-effects meta-analysis (Mantel-Haenszel method) or random-effects model (inverse variance method), for low and high heterogeneity between trials, respectively. PROSPERO Registration number: CRD42018093244 RESULTS: Seven randomized controlled trials (n = 1219) were included. Three studies were assessed as low risk of bias, three others as moderate and one study as high risk of bias. The main limitation is the lack of reporting on the methods to achieve randomization and concealment of allocation in most of the studies. There was no difference in the duration of the second stage of labor (mean -11.09 min; 95 %CI -38.85 to 16.68). In the squatting group, the risk of caesarean section was increased (RR 2.26, 95 %CI 1.07-4.80) and the risk of instrumental delivery was decreased (RR 0.60, 95 %CI 0.45-0.81), which results in a similar probability of spontaneous delivery. There were no differences regarding the other maternal and fetal outcomes.

CONCLUSIONS

The available evidence does not show the squatting position during childbirth to be beneficial. As there is no evidence for or against squatting, women should be able to choose the position they prefer.

Bicruciate-retaining total knee arthroplasty reproduces in vivo kinematics of normal knees to a lower extent than unicompartmental knee arthroplasty

PURPOSE

This study aimed to clarify the natural knee kinematics provided by bicruciate-retaining total knee arthroplasty (BCR-TKA) compared with those of unicompartmental knee arthroplasty (UKA) and normal knees.

METHODS

Volunteers and patients who had undergone UKA and BCR-TKA with anatomical articular surface performed squatting motion under fluoroscopy. To estimate the knee's spatial position and orientation, a two-dimensional/three-dimensional registration technique was used. The rotation angle and anteroposterior translation of the medial and lateral sides of the femur relative to the tibia in each flexion angle were directly evaluated using the same local coordinate system and their differences amongst the three groups were analysed using two-way analysis of variance and Bonferroni post hoc pairwise comparison.

RESULTS

From 0° to 10° of flexion, the femoral external rotation angle of BCR-TKA knees was significantly greater than that of normal and UKA knees and the medial side of BCR-TKA knees was significantly more anteriorly located than that of normal and UKA knees. From 40° to 50° of flexion, the medial side of UKA knees was significantly more posteriorly located than that of normal and BCR-TKA knees. From 30° to 120° of flexion, the lateral side of BCR-TKA knees was significantly more anteriorly located than that of normal and UKA knees.

CONCLUSION

The in vivo kinematics of BCR-TKA knees reproduces those of normal knees to a lower extent than those of UKA knees. Thus, BCR-TKA with anatomical articular surface reproduces in vivo kinematics of normal knees to a lower extent than UKA.

LEVEL OF EVIDENCE

III.

Knee kinematics of severe medial knee osteoarthritis showed tibial posterior translation and external rotation: a cross-sectional study

BACKGROUND

Knee osteoarthritis (OA) gradually reduces knee function and limits activities of daily living with age. However, the progression of abnormal kinematics of the knee in knee OA is unclear.

AIMS

This study aimed to clarify the relationship between stage of knee OA and abnormal knee kinematics and to identify a strategy for prevention of knee OA.

METHODS

A total of 112 knees of 99 patients (45 men/54 women; 55.9 ± 18.2 years), comprising 28 (27/1) in Kellgren-Lawrence grade 0, 18 (8/10) in grade 1, 27 (2/25) in grade 2, 28 (6/22) in grade 3, and 11 (3/8) in grade 4, were enrolled in this cross-sectional study. In vivo knee kinematics was obtained using a three-dimensional-to-two-dimensional registration technique utilizing CT-based bone models and lateral fluoroscopy during knee extension-flexion in an upright sitting position and squatting.

RESULTS

The external rotation angle of the tibia relative to the femur was greater in grade 3/4 knees than in grade 0/1 knees and tibial posterior translation was greater in grade 3/4 knees than in grade 0-2 knees.

DISCUSSION

Age-related changes in muscle activity and joint instability are considered to be the cause of these abnormal kinematics.

CONCLUSIONS

As the stage of knee OA progresses, there was a tendency toward increasing tibial external rotation and tibial posterior translation during knee extension-flexion in sitting position and squatting. Prevention of the progress of the abnormal knee kinematics may prevent the progression of the knee OA.

In vivo length change of ligaments of normal knees during dynamic high flexion

Background

Few studies compared the length change of ligaments of normal knees during dynamic activities of daily living. The aim of this study was to investigate in vivo length change of ligaments of the normal knees during high flexion.

Methods

Eight normal knees were investigated. Each volunteer performed squatting, kneeling, and cross-leg motions. Each sequential motion was performed under fluoroscopic surveillance in the sagittal plane. The femoral, tibial, and fibular attachment areas of the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), deep medial collateral ligament (dMCL), superficial medial collateral ligament (sMCL), and lateral collateral ligament (LCL) were determined according to osseous landmarks. After 2D/3D registration, the direct distance from the femoral attachment to the tibial or fibular attachment was measured as the ligament length.

Results

From 20° to 90° with flexion, the ACL was significantly shorter during cross-leg motion than during squatting. For the PCL, dMCL, sMCL, and LCL, there were no significant differences among the 3 motions.

Conclusion

The ACL was shorter during cross-leg motion than during squatting in mid-flexion. This suggests that the ACL is looser during cross-leg motion than during squatting. On the other hand, the length change of the PCL, MCL, and LCL did not change even though the high flexion motions were different.

Effects of Knee Savers on the quadriceps muscle activation across deep knee bending postures

Workers who kneel or squat frequently are at a high risk of developing knee pathologies. Knee Savers^® are wedge-shaped pads, worn on the lower calf by baseball catchers that aim to reduce this risk. This study examined how Knee Savers^® change the bilateral quadriceps muscle activity during dorsiflexed kneeling, and heels-up and flat-foot squatting. For twenty participants, integrated and peak electromyography (EMG) during descent and ascent phases, mean EMG during a 10-s static phase, and participants' subjective perception of muscle fatigue were compared between equipment conditions (with (W) and without (WO) Knee Savers^®). Knee Savers^® did not significantly reduce integrated or peak EMG during transitions into and out of the postures; however, they significantly reduced (p < .03) mean EMG in five of six muscles during the static phase. These findings indicate potential for Knee Savers^® to reduce cumulative muscular effort and fatigue in applications where prolonged static kneeling or squatting are required.

The effects of foot position on lower extremity kinematics during single leg squat among adolescent male athletes

Objectives

The purpose of this study was to investigate the effect of transverse plane foot position on lower limb kinematics during a single leg squat.

Methods

This was a cross-sectional study conducted among highly-trained male athletes. Only participants who showed normal knee valgus during a drop landing screening test were recruited. Twelve junior athletes performed single leg squats while maintaining a knee flexion angle of 60°. The squats were executed in three foot positions: neutral (0°), adduction (−10°), and abduction (+10°). Three-dimensional motion analysis was used to capture the lower extremity kinematics of the participants’ preferred limb. The hip and knee kinematics in the sagittal, frontal, and transverse planes during squatting were compared across the three foot positions using one-way ANOVA.

Results

The participants showed a normal range of dynamic knee valgus (5.3°±1.6). No statistically significant differences were observed in hip flexion (p = 0.322), adduction (p = 0.834), or internal rotation (p = 0.967) across different foot positions. Similarly, no statistically significant differences were observed in knee flexion (p = 0.489), adduction (p = 0.822), or internal rotation (p = 0.971) across different foot positions.

Conclusion

Small changes in transverse plane foot position do not affect lower extremity kinematics during single leg squat in highly trained adolescent males with normal dynamic knee valgus. Our findings may provide guidance on safer techniques for landing, pivoting, and cutting during training and game situations.

Injury patterns of medial meniscus posterior root tears

INTRODUCTION

Medial meniscus posterior root tear (MMPRT) can occur in middle-aged patients who have a posteromedial painful popping during light activities. MMPRTs are more common in patients with increased age, female gender, sedentary lifestyle, obesity, and varus knee alignment. However, injury mechanisms of minor traumatic MMPRTs are still unclear. We hypothesized that high flexion activities are the major cause of MMPRTs. The aim of this study was to clarify injury patterns of MMPRTs.

MATERIALS AND METHODS

One hundred patients were diagnosed having MMPRTs after posteromedial painful popping episodes. Details of posteromedial painful popping episode, situation of injury, and position of injured leg were obtained from the patients by careful interviews. Injury patterns were divided into 8 groups: descending knee motion, walking, squatting, standing up action, falling down, twisting, light exercise, and minor automobile accident.

RESULTS

A descending knee motion was the most common cause of MMPRTs (38%) followed by a walking injury pattern (18%) and a squatting action related to high flexion activities of the knee (13%). The other injury patterns were less than 10%.

DISCUSSION

Descending knee motions associated with descending stairs, step, and downhill slope are the most common injury pattern of MMPRTs. High flexion activities of the knee are not the greatest cause of MMPRTs. Our results suggest that the descending action with a low knee flexion angle may trigger minor traumatic MMPRTs.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

A lower extremity model for muscle-driven simulation of activity using explicit finite element modeling

A key strength of computational modeling is that it can provide estimates of muscle, ligament, and joint loads, stresses, and strains through non-invasive means. However, simulations that can predict the forces in the muscles during activity while maintaining sufficient complexity to realistically represent the muscles and joint structures can be computationally challenging. For this reason, the current state of the art is to apply separate rigid-body dynamic and finite-element (FE) analyses in series. However, the use of two or more disconnected models often fails to capture key interactions between the joint-level and whole-body scales. Single framework MSFE models have the potential to overcome the limitations associated with disconnected models in series. The objectives of the current study were to create a multi-scale FE model of the human lower extremity that combines optimization, dynamic muscle modeling, and structural FE analysis in a single framework and to apply this framework to evaluate the mechanics of healthy knee specimens during two activities. Two subject-specific FE models (Model 1, Model 2) of the lower extremity were developed in ABAQUS/Explicit including detailed representations of the muscles. Muscle forces, knee joint loading, and articular contact were calculated for two activities using an inverse dynamics approach and static optimization. Quadriceps muscle forces peaked at the onset of chair rise (2174 N, 1962 N) and in early stance phase (510 N, 525 N), while gait saw peak forces in the hamstrings (851 N, 868 N) in midstance. Joint forces were similar in magnitude to available telemetric patient data. This study demonstrates the feasibility of detailed quasi-static, muscle-driven simulations in an FE framework.

How to squat? Effects of various stance widths, foot placement angles and level of experience on knee, hip and trunk motion and loading

Background

Squatting is a core exercise for many purposes. The tissue loading during squatting is crucial for positive adaptation and to avoid injury. This study aimed to evaluate the effect of narrow, hip and wide stance widths, foot position angles (0°, 21°, and 42°), strength exercise experience, and barbell load (0 and 50% body weight, experts only) during squatting.

Methods

Novice (N = 21) and experienced (N = 21) squatters performed 9 different variations of squats (3 stance widths, 3 foot placement angles). A 3D motion capture system (100 Hz) and two force plates (2000 Hz) were used to record mediolateral knee displacement (ΔD*), range of motion (RoM) at the hip and knee joints, and joint moments at the hip, knee, and lower back.

Results

Both stance width and foot placement angles affected the moments at the hip and knee joints in the frontal and sagittal planes. ΔD* varied with stance width, foot placement angles and between the subjects’ level of experience with the squat exercise as follows: increasing foot angle led to an increased foot angle led to an increased ΔD*, while an increased stance width resulted in a decreased ΔD*; novice squatters showed a higher ΔD*, while additional weight triggered a decreased ΔD*.

Conclusions

Suitable stance width and foot placement angles should be chosen according to the targeted joint moments. In order to avoid injury, special care should be taken in extreme positions (narrow stand-42° and wide stance-0°) where large knee and hips joint moments were observed.

Electronic supplementary material

The online version of this article (10.1186/s13102-018-0103-7) contains supplementary material, which is available to authorized users.

Dynamic hip kinematics during squatting before and after total hip arthroplasty

Background

The difference in in vivo kinematics before and after total hip arthroplasty (THA) for the same subjects and the clearance between the liner and neck during squatting have been unclear. The purpose of the present study was to clarify (1) the changes in the in vivo kinematics between prosthetic hips and osteoarthritis hips of the same subjects and (2) the extent of the liner-to-neck clearance during squatting under weight-bearing conditions.

Methods

This study consisted of 10 patients who underwent unilateral THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, we obtained continuous radiographs during squatting. We analyzed the hip joint’s movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also quantified the minimum distance at maximum flexion and extension, and the minimum angle at maximum flexion between the liner and stem neck.

Results

The maximum hip flexion angles post-THA (80.7° [range, 69.4–98.6°]) changed significantly compared with the pre-THA values (71.7° [range, 55.2°–91.2°]). The pelvic tilt angle (posterior +, anterior−) at the maximum hip flexion post-THA (10.4° [range, − 6.7° to 26.9°]) was significantly smaller than that at pre-THA (16.6° [range, − 3° to 40.3°]). The minimum anterior and posterior liner-to-neck distances averaged 10.9 and 8.0 mm, respectively, which was a significant difference. The minimum liner-to-neck angle at maximum flexion averaged 34.7° (range, 20.7°–46.3°). No liner-to-neck contact occurred in any of the hips.

Conclusion

THA increased the range of hip joint motion and the pelvis tilted anteriorly more after than before THA, with sufficient liner-to-neck clearance during squatting. These data may be beneficial for advising patients after THA regarding postoperative activity restrictions in daily life.

In vivo kinematics of early-stage osteoarthritic knees during pivot and squat activities

Kinematic changes have been shown to accompany severe knee osteoarthritis, but no studies have analyzed early-stage osteoarthritic knee kinematics in the transverse plane during functional activities. The purpose of this study was to analyze kinematics of early-stage osteoarthritic knees using model registration techniques. Fifteen early-stage osteoarthritic knees from eight females with a mean age of 52 years old (range, 43-57years old) were involved in this study. A radiologist confirmed with plain radiographs that knees had Kellgren-Lawrence grade-1 or -2 arthritic changes. Fluoroscopic images of squat and pivot activities were recorded for each subject. Three-dimensional surface models of the distal femur and proximal tibia were created from CT images, and anatomic coordinate systems were embedded in each model. The three-dimensional position and orientation of the femur and the tibia were determined using model-image registration techniques, and tibial anteroposterior translation and internal/external rotation relative to the femur were calculated. The contact points of the medial and lateral femoral condyle were also computed. Compared to healthy knees, osteoarthritic knees showed lateral contact points that were significantly shifted anteriorly in both pivot (P<0.001) and squat (P=0.001) activities and greater tibial external rotation in pivot activity (P=0.007). The medial contact point location was similar to healthy knees, but the amount of anteroposterior translation was smaller (P<0.001). These kinematic changes might change stress distributions in the medial compartment during weight-bearing activities. The changes in kinematics possibly have some influence on initiation or progression of knee osteoarthritis.

Stooping, crouching, and standing - Characterizing balance control strategies across postures

BACKGROUND

While stooping and crouching postures are critical for many activities of daily living, little is known about the balance control mechanisms employed during these postures. Accordingly, the purpose of this study was to characterize the mechanisms driving net center of pressure (COP_Net) movement across three postures (standing, stooping, and crouching) and to investigate if control in each posture was influenced by time.

METHODS

Ten young adults performed the three postures for 60s each. Kinetic signals were collected via a force platform under each foot. To quantify mechanisms of control, correlations (Correl_LR) were calculated between the left and right COP trajectories in the anterior-posterior (AP) and medio-lateral (ML) directions. To examine the potential effects of time on balance control strategies, outcomes during the first 30s were compared to the last 30s.

RESULTS

Correl_LR values did not differ across postures (AP: p = 0.395; ML: p = 0.647). Further, there were no main effects of time on Correl_LR (AP: p = 0.976; ML: p = 0.105). A significant posture-time interaction was observed in the ML direction (p = 0.045) characterized by 35% decreases in Correl_LR over time for stooping (p = 0.022).

CONCLUSION

The dominant controllers of sway (i.e., AP: ankle plantar/dorsi flexors; ML: hip load/unload mechanism) are similar across quiet stance stooping, and crouching. Changes in ML control strategies over time suggests that fatigue could affect prolonged stooping more so than crouching or standing.

The role of interaction torque and muscle torque in the control of downward squatting

[Purpose] The purposes of this study were first to analyze the multijoint dynamics of downward squatting, and to examine the contribution of interaction torque and muscle torque to net torque, and second, to examine mechanisms of movement control. [Subjects] The subjects were 31 healthy men with a mean age of 21.0 ± 1.2 years (range, 19-24 years). [Methods] Squatting tasks with the trunk in two positions, an erect and anterior tilt position, were performed by the subjects. Net, interaction, muscle, and gravity torque were calculated according to the Lagrange equation using 3D tracking data. [Results] The contribution ratio of interaction torque to net torque was approximately 90%, irrespective of the joint and task. In contrast, muscle torque showed complicated behavior to compensate for gravity torque. A combined muscle and gravity torque profile showed flexion or dorsiflexion immediately after the initiation of the movement, and it later changed to extension or plantar flexion. [Conclusion] The torque that contributes almost exclusively to the net torque was interaction torque. The combination of muscle and gravity torque at the knee joint and the hip joint is important for movement control, independent of the starting position.

Two different gracilis loops in graciloplasty of congenital fecal incontinence: comparison of the therapeutic effects

PURPOSE

The aim of this study was to compare the clinical effect of graciloplasty using two different gracilis encircled loops for the treatment of fecal incontinence after anoplasty for imperforate anus.

METHODS

From January 2009 to January 2012, 38 patients were treated by graciloplasty. The patients were randomly divided into two groups, one group consisting of 18 cases underwent the "γ-loop" and the other group consisting of 20 cases underwent the "υ-loop." All patients underwent postoperative defecation training and regular follow-up. All patients were evaluated via Wexner score and anal manometry (including anal resting pressure, anal maximal squeeze pressure, duration of anal squeeze, and rectal maximum tolerable volume) before and after graciloplasty. In addition, it was assessed whether the patients had difficulty defecating while squatting after surgery.

RESULTS

The surgeries on the 38 patients were accomplished successfully. There were no differences in postoperative complications between the two groups (P > 0.05). The Wexner score and anal manometry parameters of the two groups were gradually improved after operation. The generalized estimating equation results of the Wexner score indicated that the difference of measurement time was statistically significant (P < 0.05) but the difference of measurement group was not statistically significant (P > 0.05). The results of anal manometry parameters using repeated measures ANOVA indicated that differences between different time points were statistically significant (all P < 0.05) but differences between different surgery groups were not statistically significant (all P > 0.05). Regarding the postoperative defecating difficulties while squatting, the probability of occurrence in the "γ-loop" group was significantly higher than that in the "υ-loop" group. The difference between the two groups was statistically significant (P < 0.05).

CONCLUSIONS

Graciloplasty with different gracilis loops can improve anal function in patients. However, "υ-loop" can significantly improve difficulties in defecating while squatting.

Comparison of two methods of determining patellofemoral joint stress during dynamic activities

BACKGROUND

Joint specific models rely on muscle force estimates to quantify tissue specific stresses. Traditionally, muscle forces have been estimated using inverse dynamics alone. Inverse dynamics coupled with static optimization techniques allow for an alternative method in estimating muscle forces. Differences between these two techniques have not been compared for determining the quadriceps force for estimating patellofemoral joint stress.

METHODS

Eleven female participants completed five squats and ten running trials. Motion capture and force platform data were processed using both solely inverse dynamics and inverse dynamics with static optimization to estimate the quadriceps force in a patellofemoral joint model.

FINDINGS

Patellofemoral joint stress calculations were consistently higher when using the combination of inverse dynamics and static optimization as compared to the inverse dynamics alone (p<0.05) yielding estimates that were 30-106% greater.

INTERPRETATION

When implementing joint models to estimate tissue specific stresses, the choice of technique used to estimate muscle forces plays an important role in determining the magnitude of estimated stresses in patellofemoral joint models.

Moving beyond quiet stance: applicability of the inverted pendulum model to stooping and crouching postures

BACKGROUND

Currently, it is unknown whether the inverted pendulum model is applicable to stooping or crouching postures. Therefore, the aim of this study was to determine the degree of applicability of the inverted pendulum model to these postures, via examination of the relationship between the centre of mass (COM) acceleration and centre of pressure (COP)-COM difference.

METHODS

Ten young adults held static standing, stooping and crouching postures, each for 20s. For both the anterior-posterior (AP) and medio-lateral (ML) directions, the time-varying COM acceleration and the COP-COM were computed, and the relationship between these two variables was determined using Pearson's correlation coefficients. Additionally, in both directions, the average absolute COM acceleration, average absolute COP-COM signal, and the inertial component (i.e., -I/Wh) were compared across postures.

RESULTS

Pearson correlation coefficients revealed a significant negative relationship between the COM acceleration and COP-COM signal for all comparisons, regardless of the direction (p<0.001). While no effect of posture was observed in the AP direction (p=0.463), in the ML direction, the correlation coefficients for stooping were different (i.e., stronger) than standing (p=0.008). Regardless of direction, the average absolute COM acceleration for both the stooping and crouching postures was greater than standing (p<0.002).

CONCLUSION

The high correlations indicate that the inverted pendulum model is applicable to stooping and crouching postures. Due to their importance in completing activities of daily living, there is merit in determining what type of motor strategies are used to control such postures and whether these strategies change with age.

A preliminary study on the differences in male and female muscle force distribution patterns during squatting and lunging maneuvers

In the United States, 250,000 people tear their anterior cruciate ligament (ACL) annually with females at higher risk of ACL failure than males. By predicting muscle forces during low impact maneuvers we may be able to estimate possible muscle imbalances that could lead to ACL failure during highly dynamic maneuvers. The purpose of this initial study was to predict muscle forces in males and females similar in size and activity level, during squat and lunge maneuvers. We hypothesized that during basic low impact maneuvers (a) distribution of quadriceps forces are different in males and females and (b) females exhibit quadriceps dominance when compared to males. Two males and three females performed squatting and lunging maneuvers while electromyography (EMG) data, motion capture data, and ground reaction forces were collected. Nine individual muscle forces for muscles that cross the knee were estimated using an EMG-driven model. Results suggest that males activate their rectus femoris muscle more than females, who in turn activate their vastus lateralis muscle at their maximum flexion angle, and more their vastus medialis muscle when ascending from a squat. During the lunge maneuver, males used greater biceps femoris force than females, throughout the lunge, and females exhibited higher semitendinosus force. Quadriceps dominance was evident in both males and females during the prescribed tasks, and there was no statistical difference between genders. Understanding individual muscle force distributions in males and females during low impact maneuvers may provide insights regarding failure mechanisms during highly dynamic maneuvers, when ACL injuries are more prevalent.

Comparison of quasi-static and dynamic squats: a three-dimensional kinematic, kinetic and electromyographic study of the lower limbs

Numerous studies have described 3D kinematics, 3D kinetics and electromyography (EMG) of the lower limbs during quasi-static or dynamic squatting activities. One study compared these two squatting conditions but only at low speed on healthy subjects, and provided no information on kinetics and EMG of the lower limbs. The purpose of the present study was to contrast simultaneous recordings of 3D kinematics, 3D kinetics and EMG of the lower limbs during quasi-stat ic and fast-dynamic squats in healthy and pathological subjects. Ten subjects were recruited: five healthy and five osteoarthritis subjects. A motion-capture system, force plate, and surface electrodes respectively recorded 3D kinematics, 3D kinetics and EMG of the lower limbs. Each subject performed a quasi-static squat and several fast-dynamic squats from 0° to 70° of knee flexion. The two squatting conditions were compared for positions where quasi-static and fast-dynamic knee flexion-extension angles were similar. Mean differences between quasi-static and fast-dynamic squats were 1.5° for rotations, 1.9 mm for translations, 2.1% of subjects' body weight for ground reaction forces, 6.6 Nm for torques, 11.2 mm for center of pressure, and 6.3% of maximum fast-dynamic electromyographic activities for EMG. Some significant differences (p<0.05) were found in internal rotation, anterior translation, vertical force and EMG. All differences between quasi-static and fast-dynamic squats were small. 69.5% of compared data were equivalent. In conclusion, this study showed that quasi-static and fast-dynamic squatting activities are comparable in terms of 3D kinematics, 3D kinetics and EMG, although some reservations still remain.

Comparison of knee gait kinematics of workers exposed to knee straining posture to those of non-knee straining workers

Workers exposed to knee straining postures, such as kneeling and squatting, may present modifications in knee gait kinematics that can make them vulnerable to osteoarthritis. In this study, knee kinematics of workers exposed to occupational knee straining postures (KS workers) were compared to those of non-knee straining (non-KS) workers. Eighteen KS workers and 20 non-KS workers participated in the study. Three-dimensional gait kinematic data were recorded at the knee using an electromagnetic motion tracking system. The following parameters were extracted from flexion/extension, adduction/abduction and internal/external rotation angle data and used for group comparisons: knee angle at initial foot contact, peak angles, minimal angles and angle range during the entire gait cycle. Group comparisons were performed with Student t-tests. In the sagittal plane, KS workers had a greater knee flexion angle at initial foot contact, a lower peak knee flexion angle during the swing phase and a lower angle range than non-KS workers (p<0.05). In the frontal plane, all parameters indicated that KS workers had their knees more adducted than non-KS workers. External/internal rotation range was greater for KS workers. This study provides new knowledge on work related to KS postures and knee kinematics. The results support the concept that KS workers might exhibit knee kinematics that are different from those of non-KS workers.

The effect of McConnell taping on vastus medialis and lateralis activity during squatting in adults with patellofemoral pain syndrome

This study aims to examine the effect of McConnell taping to patients with patellofemoral pain syndrome on the change of the muscle activity of vastus medialis and vastus lateralis during squatting. The total numbers of participants are 16 patients with pain in their knee. There are three different experiments: no-taping, placebo taping, and McConnell taping. As a result, both the muscle activity of vastus medialis and muscle activity ratio of vastus medialis to vastus lateralis increased in placebo taping compared to no-taping, which wasn't statistically significant. However, the muscle activity of vastus medialis and muscle activity ratio of vastus medialis to vastus lateralis increased in McConnell taping compared to no-taping, which was statistically significant. These results suggest that McConnell taping affects the activity of quadriceps by changing the position of the patella, and thus can effectively be applied in the treatment of patellofemoral pain syndrome.

Effects of the off-loading brace on the activation of femoral muscles -a preliminary study-

Objective

To provide the off-loading knee brace was designed relief for the pain associated with osteoarthritis by reduce loads on the degenerative compartment of the knee. This study examined the effects of the off-loading knee brace on activation of femoral muscles during squatting, slow and fast walking exercise in healthy young individuals.

Method

Ten healthy male subjects without a history of knee pain were recruited. Each subject was asked to do squatting, slow and fast walking exercises with a brace secured to the dominant leg. The same exercises were repeated without the brace. Surface electromyographic (sEMG) data was collected from the vastus medialis oblique (VMO), vastus lateralis (VL) and biceps femoris (BF) muscles from the dominant side of the leg. All dynamic root mean squre (RMS) values of sEMG were standardized to static RMS values of the maximal isometric contraction and expressed as a percentage of maximal activity.

Results

We found that VMO activity was significantly decreased with application of the off-loading knee brace during squatting and fast walking exercise. However there were no significant differences in VMO activity with application of the off-loading knee brace during slow walking exercise.

Conclusion

These results suggest that the external moment of the brace which effectively stabilized the patella in the movement in which the knee joints become relatively unstable. The brace could be useful in the short term, but for long-term use, weakening of the VMO is predicted. Therefore the program of selective muscular strength strengthening for the VMO should be emphasized.

Does squatting worsen lower limb ischemia in patients with peripheral arterial disease?

Peripheral arterial disease (PAD) is an important cause of morbidity and mortality in the world affecting up to 20% in people over 70 years of age. The prevalence is increasing in India due to combined effects of increased life expectancy, increased tobacco smoking and increased prevalence of diabetes mellitus. The aim of the study was to examine the hypothesis whether squatting posture reduces blood flow to lower limbs resulting in worsening of symptoms of lower limb ischemia in patients with PAD. 10 patients with arterial disorders due to thromboangiitis obliterans (TAO), atherosclerosis and diabetic macro vascular disease were selected for patients and were compared with 10 healthy volunteers as controls. Clinical examination and duplex scan of posterior tibial artery (PTA) and dorsalis pedis artery (DPA) performed in standing and squatting position in a clinical environment. They were asked about symptoms of numbness, ischemic pain and the results were noted. Results were tabulated and analysed using Microsoft Excel®. Members in the control group complained of numbness of both the limbs after a period of 30 min on an average. In the patients group, members while squatting complained of numbness in the involved limb within 5 min. They complained of ischemic pain in the involved limb within 10 min and developed numbness in the opposite limb in within 15 min. Posterior tibial artery and dorsalis pedis artery pulsations disappeared for the entire duration of squatting in both groups as confirmed by duplex scanning. It may be recommended that patients with established peripheral vascular disease should avoid squatting position, even if it is for a very short period of time. It is desirable to advice such patients to use appropriate structures as supports which will allow them to work without squatting. This may also necessitate a change in occupation.