The Midfoot Joint Complex (Foot Arch) Contributes to the Upper Body Position in Bipedal Walking and Coordinates With the Lower Limb Joints.

This study estimated the contribution of the midfoot joint complex (MJC) kinematics to the pelvis anterior-posterior positions during the stance phase of walking and investigated whether the MJC is functionally coordinated with the lower limb joints to maintain similar pelvic positions across steps. Hip, knee, ankle, and MJC sagittal angles were measured in 11 nondisabled participants during walking. The joints' contributions to pelvic positions were computed through equations derived from a link-segment model. Functional coordination across steps was identified when the MJC contribution to pelvic position varied and the summed contributions of other joints varied in the opposite direction (strong negative covariations [r ≤ -.7] in stance phase instants). We observed that the MJC plantarflexion (arch raising) during the midstance and late stance leads the pelvis backward, avoiding excessive forward displacement. The MJC was the second joint that contributed most to the pelvis positions (around 18% of all joints' contributions), after the ankle joint. The MJC and ankle were the joints that were most frequently coordinated with the other joints (≅70% of the stance phase duration). The findings suggest that the MJC is part of the kinematic chain that determines pelvis positions during walking and is functionally coordinated with the lower limb joints.

Reliability of measurements assessing the Lisfranc joint using weightbearing computed tomography imaging.

INTRODUCTION: Subtle Lisfranc joint injuries remain challenging to diagnose in clinical practice. Although of questionable accuracy, bilateral weightbearing radiographs are considered the current gold standard to assess these injuries. However, weightbearing computed tomography (WBCT), which provides clearer visualization of bony landmarks, can also be used for evaluation. This study aims to design a protocol that reliably measures the distance between the medial cuneiform (C1) and second metatarsal (M2) to assess the Lisfranc joint using WBCT imaging. METHODS: Two unique methods of measuring the C1-M2 distance were designed that localize the center of the interosseous Lisfranc ligament (ILL, reference point). This reference point was located by (I) measuring a specific distance at the M2 base, or (II) approximating from nearby bony landmarks, on both axial (Ax) and coronal (Cor) WBCT images. Four parameters (I-Ax, I-Cor, II-Ax, and II-Cor) were evaluated for each of 96 specimens. Measurements were recorded by three independent observers and repeated for inter- and intra-observer agreement. RESULTS: In total, 96 patient image series were included and assessed in our study with an average age of 46 (19-66, SD 16.1) and average BMI of 25.8 (17.8-30.5, SD 4.3). I-Ax showed excellent agreement for intra-observer evaluation (R = 0.802) and good agreement for inter-observer evaluation (R = 0.727). I-Cor demonstrated excellent inter- (R = 0.814) and intra-observer (R = 0.840) agreement. Good agreement was found for both II-Ax and II-Cor for both intra- (R = 0.730, R = 0.708) and inter-observer (R = 0.705, R = 0.645) evaluation. CONCLUSION: Measuring the C1-M2 joint space with coronal WBCT imaging through a protocol that localizes the ILL is reproducible, simple, and can potentially be utilized clinically to evaluate the Lisfranc joint.

Paediatric patients with blood-induced ankle joint arthritis demonstrate physiological foot joint mechanics and energetics during walking.

AIM: To compare foot joint kinetics and energetics in male paediatric boys with and without blood-induced ankle joint destruction to these of matched control groups. METHODS: A cross-sectional study was conducted in which 3D gait analysis data were collected from thirty-five male children (6-21 years) with severe or moderate haemophilia and twenty-six typically developing boys. Structural integrity of the tarsal foot joints of all haemophilic patients was assessed using the IPSG-MRI scale. All participants walked barefoot while adopting a physiological gait pattern. Three subgroups were created based on the IPSG-MRI scores: a group with no joint involvement (HealthyHaemo), with uni- or bilaterally involvement (PathoHaemo) and with only unilaterally involvement (Haemo_Unilateral_Patho). RESULTS: The PathoHaemo group presented a significant lower Lisfranc peak dorsiflexion angular velocity (34.7°/s vs 71.4°/s, P = .000, Cohen d = 1.31) and a significantly higher Lisfranc peak plantarflexion angular velocity (-130.5°/s vs -51.8°/s, P = .000, Cohen d = 0.98) compared to the control group. The Haemo_Unilateral_Patho side had a significant higher Chopart peak dorsiflexion angular velocity compared to the Haemo_Unilateral_Healthy side (41.7°/s vs 31.9°/s, P = .002, Cohen d = 1.16). CONCLUSION: No evidence for mild and severe gait deviations could be demonstrated. Internal moments, used as a surrogate measure of joint loading, quantified by the multi-segment foot model were found to be similar within the three subanalyses. We suggest that the ongoing musculoskeletal development in children compensates for structural damage to the ankle joint.

The Impact of a Foot-Toe Orthosis on Dynamic Balance: An Exploratory Randomized Control Trial.

CONTEXT: The influence of custom and over-the-counter foot orthoses on dynamic balance has been investigated in the past. However, there has not been an exploration of the use of a foot-toe orthosis for improving balance. The ability of clinicians to influence balance could have important implications for injury prevention and rehabilitation. OBJECTIVE: To determine the impact of a foot-toe orthosis on dynamic balance in healthy, young adults. DESIGN: Randomized control trial. SETTING: Athletic training laboratory. PARTICIPANTS: In total, 64 healthy, recreationally active participants aged 18-29 years were randomly allocated to one of the following groups: the foot-toe orthosis and laboratory-issued shoe group, the laboratory-issued shoe only (SO) group, or the control group. INTERVENTIONS: Subjects in the intervention group wore the foot-toe orthosis and laboratory-issued shoe with activities of daily living for 4 weeks. Subjects in the SO intervention group wore the laboratory-issued shoe with activities of daily living for 4 weeks. Participants in the control group did not receive any intervention. MAIN OUTCOME MEASURES: The instrumented version of the Star Excursion Balance Test, known as the Lower Quarter Y-Balance Test, was used to quantify the dynamic balance at baseline and follow-up. Reaches were normalized for leg length. RESULTS: There were statistically significant differences in postintervention scores on the Lower Quarter Y-Balance Test for both the dominant (P = .03, effect size = 0.84; 95% confidence interval, 0.25 to 1.43) and nondominant (P = .002, effect size = 0.74; 95% confidence interval, 0.15 to 1.32) legs when comparing dynamic balance scores of the foot-toe orthosis and laboratory-issued shoe group with the SO and control groups. No significant differences were observed when comparing dynamic balance between the SO and control groups. CONCLUSIONS: A 4-week intervention with a foot-toe orthosis and laboratory-issued shoe resulted in improved dynamic balance in a healthy young adult population. These findings suggest a novel intervention for increasing balance.

Pearls and pitfalls of fluoroscopic-guided foot and ankle injections: what the radiologist needs to know.

OBJECTIVE: This article provides a comprehensive, joint-by-joint review of fluoroscopic-guided foot and ankle injections and emphasizes pre-procedural planning, relevant anatomy, appropriate technique, troubleshooting the difficult procedure, and the importance of communicating unexpected findings with the referring clinician. The interrogation of pain generators including variant ossicles, fractures, and post-surgical/traumatic findings is also described. CONCLUSIONS: Even the most challenging foot and ankle injections may be successfully completed with a solid anatomical understanding and thoughtful approach.

Closing the Wearable Gap-Part II: Sensor Orientation and Placement for Foot and Ankle Joint Kinematic Measurements.

The linearity of soft robotic sensors (SRS) was recently validated for movement angle assessment using a rigid body structure that accurately depicted critical movements of the foot-ankle complex. The purpose of this study was to continue the validation of SRS for joint angle movement capture on 10 participants (five male and five female) performing ankle movements in a non-weight bearing, high-seated, sitting position. The four basic ankle movements-plantar flexion (PF), dorsiflexion (DF), inversion (INV), and eversion (EVR)-were assessed individually in order to select good placement and orientation configurations (POCs) for four SRS positioned to capture each movement type. PF, INV, and EVR each had three POCs identified based on bony landmarks of the foot and ankle while the DF location was only tested for one POC. Each participant wore a specialized compression sock where the SRS could be consistently tested from all POCs for each participant. The movement data collected from each sensor was then compared against 3D motion capture data. R-squared and root-mean-squared error averages were used to assess relative and absolute measures of fit to motion capture output. Participant robustness, opposing movements, and gender were also used to identify good SRS POC placement for foot-ankle movement capture.

The Receptive and Propulsive Behavior of Human Foot Joints During Running With Different Striking Strategies.

Foot structure and kinematics have long been considered as risk factors for foot and lower-limb running injuries. The authors aimed at investigating foot joint kinetics to unravel their receptive and propulsive characteristics while running barefoot, both with rearfoot and with midfoot striking strategies. Power absorption and generation occurring at different joints of the foot in 6 asymptomatic adults were calculated using both a 3-segment and a 4-segment kinetic model. An inverse dynamic approach was used to quantify mechanical power. Major power absorption and generation characteristics were observed at the ankle joint complex as well as at the Chopart joint in both the rearfoot and the midfoot striking strategies. The power at the Lisfranc joint, quantified by the 4-segment kinetic model, was predominantly generated in both strategies, and at the toes, it was absorbed. The overall results show a large variability in the receptive and propulsive characteristics among the analyzed joints in both striking strategies. The present study may provide novel insight for clinical decision making to address foot and lower-limb injuries and to guide athletes in the adoption of different striking strategies during running.

Foot and Ankle Joint Biomechanical Adaptations to an Unpredictable Coronally Uneven Surface.

Coronally uneven terrain, a common yet challenging feature encountered in daily ambulation, exposes individuals to an increased risk of falling. The foot-ankle complex may adapt to improve balance on uneven terrains, a recovery strategy which may be more challenging in patients with foot-ankle pathologies. A multisegment foot model (MSFM) was used to study the biomechanical adaptations of the foot and ankle joints during a step on a visually obscured, coronally uneven surface. Kinematic, kinetic and in-shoe pressure data were collected as ten participants walked on an instrumented walkway with a surface randomly positioned ±15 deg or 0 deg in the coronal plane. Coronally uneven surfaces altered hindfoot-tibia loading, with more conformation to the surface in early than late stance. Distinct loading changes occurred for the forefoot-hindfoot joint in early and late stance, despite smaller surface conformations. Hindfoot-tibia power at opposite heel contact (@OHC) was generated and increased on both uneven surfaces, whereas forefoot-hindfoot power was absorbed and remained consistent across surfaces. Push-off work increased for the hindfoot-tibia joint on the everted surface and for the forefoot-hindfoot joint on the inverted surface. Net work across joints was generated for both uneven surfaces, while absorbed on flat terrain. The partial decoupling and joint-specific biomechanical adaptations on uneven surfaces suggest that multi-articulating interventions such as prosthetic devices and arthroplasty may improve ambulation for mobility-impaired individuals on coronally uneven terrain.

Segmented Forefoot Plate in Basketball Footwear: Does it Influence Performance and Foot Joint Kinematics and Kinetics?

This study examined the effects of shoes' segmented forefoot stiffness on athletic performance and ankle and metatarsophalangeal joint kinematics and kinetics in basketball movements. Seventeen university basketball players performed running vertical jumps and 5-m sprints at maximum effort with 3 basketball shoes of various forefoot plate conditions (medial plate, medial + lateral plates, and no-plate control). One-way repeated measures ANOVAs were used to examine the differences in athletic performance, joint kinematics, and joint kinetics among the 3 footwear conditions (α = .05). Results indicated that participants wearing medial + lateral plates shoes demonstrated 2.9% higher jump height than those wearing control shoes (P = .02), but there was no significant differences between medial plate and control shoes (P > .05). Medial plate shoes produced greater maximum plantar flexion velocity than the medial + lateral plates shoes (P < .05) during sprinting. There were no significant differences in sprint time. These findings implied that inserting plates spanning both the medial and lateral aspects of the forefoot could enhance jumping, but not sprinting performances. The use of a medial plate alone, although induced greater plantar flexion velocity at the metatarsophalangeal joint during sprinting, was not effective in improving jump heights or sprint times.

Chimpanzee ankle and foot joint kinematics: Arboreal versus terrestrial locomotion.

OBJECTIVES: Many aspects of chimpanzee ankle and midfoot joint morphology are believed to reflect adaptations for arboreal locomotion. However, terrestrial travel also constitutes a significant component of chimpanzee locomotion, complicating functional interpretations of chimpanzee and fossil hominin foot morphology. Here we tested hypotheses of foot motion and, in keeping with general assumptions, we predicted that chimpanzees would use greater ankle and midfoot joint ranges of motion during travel on arboreal supports than on the ground. METHODS: We used a high-speed motion capture system to measure three-dimensional kinematics of the ankle and midfoot joints in two male chimpanzees during three locomotor modes: terrestrial quadrupedalism on a flat runway, arboreal quadrupedalism on a horizontally oriented tree trunk, and climbing on a vertically oriented tree trunk. RESULTS: Chimpanzees used relatively high ankle joint dorsiflexion angles during all three locomotor modes, although dorsiflexion was greatest in arboreal modes. They used higher subtalar joint coronal plane ranges of motion during terrestrial and arboreal quadrupedalism than during climbing, due in part to their use of high eversion angles in the former. Finally, they used high midfoot inversion angles during arboreal locomotor modes, but used similar midfoot sagittal plane kinematics across all locomotor modes. DISCUSSION: The results indicate that chimpanzees use large ranges of motion at their various ankle and midfoot joints during both terrestrial and arboreal locomotion. Therefore, we argue that chimpanzee foot anatomy enables a versatile locomotor repertoire, and urge caution when using foot joint morphology to reconstruct arboreal behavior in fossil hominins.

New urate depositions on dual-energy computed tomography in gouty arthritis during urate-lowering therapy.

Reduction of urate depositions in the joints, on dual-energy computed tomography (DECT), in patients with gout during urate-lowering therapy (ULT) was demonstrated in previous studies. The aim of this study was to further investigate the changes in distribution of urate deposits during ULT. This randomized controlled trial enrolled 46 patients diagnosed with gout from Zhongshan Hospital, China, between October 2013 and June 2014. Epidemiological data, serum uric acid level, and arthritis attacks were recorded at monthly follow-up visits. DECT of bilateral feet and ankles was performed at baseline and after 6 months of ULT. Overall, 163 areas of urate deposition were found in the 46 patients; of these, 133/163 (81.6%) areas were associated with former arthritis attacks. On DECT at 6 months, the number of urate deposits decreased to 126, with 68 areas disappearing and 31 new deposits areas. The mean volume of urate deposits at baseline was 1.3 ± 3.8 cm3, decreasing to 0.6 ± 2.1 cm3 at the end of 6 months (P = 0.01), with 3/46 (6.5%) patients showing complete disappearance of urate deposits. New urate depositions were found in 21/46 (45.7%) patients, while urate depositions in some joints disappeared in some joints in 31/46 (67.4%) patients. High-sensitivity C-reactive protein was significantly lower in patients with new deposits (4.6 ± 9.3 vs. 7.1 ± 7.6 mg/dL; P = 0.01). There is dynamic redistribution of urate depositions in gout patients receiving ULT.

Joint Mechanics After Total Knee Arthroplasty While Descending Stairs.

BACKGROUND: Modern knee designs do not fully restore the anatomy and kinematics of the natural knee. This study evaluates the kinematic and kinetic changes of well-functioning patients with total knee arthroplasty (TKA) in comparison to a healthy age-matched control group while descending stairs and level walking. The aim was to have a baseline for further investigations of TKA patients with problems. METHODS: Fifteen patients satisfied with TKA (8♀/7♂; 66.8 ± 7.4 years; body mass index (BMI) 25.9 ± 2.8 kg/m2; 2.1 ± 1.3 years postop, LCS Complete) and 17 healthy control subjects (7♀/10♂; 66.6 ± 6.8 years; BMI 25.0 ± 2.2 kg/m2) participated in the study. Kinematic (upper and lower body) and kinetic (lower body) data were collected during stair descending (step height 17 cm) and level walking, using an 8-camera Vicon system and 2 force plates. Parameters were compared using a Student t test. RESULTS: Patients after TKA showed significantly lower frontal knee moments and a more externally rotated hip during stance for both level walking and stair descent. There were 31% more significantly different parameters during level walking than during stair descent. CONCLUSION: The analysis of stair descending in addition to level walking for satisfied patients does not add additional information for the understanding of the kinematic and kinetic changes after TKA. It seems more important to include the kinematics and kinetics of the hip and ankle joint in all 3-dimensional planes.

Biomechanics of the Ageing Foot and Ankle: A Mini-Review.

Foot pain is highly prevalent in older people and has a significant detrimental impact on mobility and quality of life. In recent years, there has been increased interest in exploring the biomechanical factors that may contribute to the development of foot disorders and the associated impairment of mobility in this age group. Studies have shown that with advancing age, there is a general tendency for the foot to exhibit increased soft tissue stiffness, a decreased range of motion, decreased strength and a more pronated posture as well as to function in a more pronated position with reduced joint mobility and less efficient propulsion when walking. These changes may contribute to the development of foot pain, impair performance in functional weight-bearing activities and increase the risk of falls. However, plantar pressure analysis technology has considerable potential to assist in optimising the design of interventions to redistribute load away from high-pressure areas, thereby alleviating foot symptoms and improving mobility in older people.

Coordination of intrinsic and extrinsic foot muscles during walking.

PURPOSE: The human foot undergoes complex deformations during walking due to passive tissues and active muscles. However, based on prior recordings it is unclear if muscles that contribute to flexion/extension of the metatarsophalangeal (MTP) joints are activated synchronously to modulate joint impedance, or sequentially to perform distinct biomechanical functions. We investigated the coordination of MTP flexors and extensors with respect to each other, and to other ankle-foot muscles. METHODS: We analyzed surface electromyographic (EMG) recordings of intrinsic and extrinsic foot muscles for healthy individuals during level treadmill walking, and also during sideways and tiptoe gaits. We computed stride-averaged EMG envelopes and used the timing of peak muscle activity to assess synchronous vs. sequential coordination. RESULTS: We found that peak MTP flexor activity occurred significantly before peak MTP extensor activity during walking (P < 0.001). The period around stance-to-swing transition could be roughly characterized by sequential peak muscle activity from the ankle plantarflexors, MTP flexors, MTP extensors, and then ankle dorsiflexors. We found that foot muscles that activated synchronously during forward walking tended to dissociate during other locomotor tasks. For instance, extensor hallucis brevis and extensor digitorum brevis muscle activation peaks decoupled during sideways gait. CONCLUSIONS: The sequential peak activity of MTP flexors followed by MTP extensors suggests that their biomechanical contributions may be largely separable from each other and from other extrinsic foot muscles during walking. Meanwhile, the task-specific coordination of the foot muscles during other modes of locomotion indicates a high-level of specificity in their function and control.

The foot core system: a new paradigm for understanding intrinsic foot muscle function.

The foot is a complex structure with many articulations and multiple degrees of freedom that play an important role in static posture and dynamic activities. The evolutionary development of the arch of the foot was coincident with the greater demands placed on the foot as humans began to run. The movement and stability of the arch is controlled by intrinsic and extrinsic muscles. However, the intrinsic muscles are largely ignored by clinicians and researchers. As such, these muscles are seldom addressed in rehabilitation programmes. Interventions for foot-related problems are more often directed at externally supporting the foot rather than training these muscles to function as they are designed. In this paper, we propose a novel paradigm for understanding the function of the foot. We begin with an overview of the evolution of the human foot with a focus on the development of the arch. This is followed by a description of the foot intrinsic muscles and their relationship to the extrinsic muscles. We draw the parallels between the small muscles of the trunk region that make up the lumbopelvic core and the intrinsic foot muscles, introducing the concept of the foot core. We then integrate the concept of the foot core into the assessment and treatment of the foot. Finally, we call for an increased awareness of the importance of the foot core stability to normal foot and lower extremity function.

The association between hallux valgus and proximal joint alignment in young female dancers.

Very little is known about the relationship between proximal joint alignment and hallux valgus among young dancers. This study sought to determine the extent to which spinal and lower extremity alignments are involved in hallux valgus, and to identify predicting variables for its development in young dancers. A group of 1336 young female dancers aged 8-16 years, and 226 control participants of the same age cohort were screened for the presence of hallux valgus, body physique characteristics, joint range of motion, and anatomical anomalies. Hallux valgus was common in the 2 young female populations studied. Among the dancers, 40.0% had bilateral hallux valgus and 7.3% unilateral. Among the controls, 32.3% had bilateral and 1.8% unilateral hallux valgus (χ2=8.27, df=1, p=0.004). Following logistic regression analysis, age (OR=1.028, 95% CI=0.968-1.091), genu varum (OR=1.514; CI=1.139-2.013) and scoliosis (OR=2.089; CI=1.113-3.921) were found to be significant predicting factors for hallux valgus in the dancer group, whereas in the control group, the predicting factors were age (OR=0.911, 95% CI=0.801-1.036) and ankle plantar flexion range of motion (OR=0.972; CI=0.951-0.992). In conclusion, it was found that spinal deformity, lower extremity alignment, and joint range of motion are strongly related to hallux valgus.

The effects of orthotic intervention on multisegment foot kinematics and plantar fascia strain in recreational runners.

Chronic injuries are a common complaint in recreational runners. Foot orthoses have been shown to be effective for the treatment of running injuries but their mechanical effects are still not well understood. This study aims to examine the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. Fifteen male participants ran at 4.0 m · s(-1) with and without orthotics. Multisegment foot kinematics and plantar fascia strain were obtained during the stance phase and contrasted using paired t tests. Relative coronal plane range of motion of the midfoot relative to the rearfoot was significantly reduced with orthotics (1.0°) compared to without (2.2°). Similarly, relative transverse plane range of motion was significantly lower with orthotics (1.1°) compared to without (1.8°). Plantar fascia strain did not differ significantly between orthotic (7.1) and nonorthotic (7.1) conditions. This study shows that although orthotics did not serve to reduce plantar fascia strain, they are able to mediate reductions in coronal and transverse plane rotations of the midfoot.

Analysis of joint force and torque for the human and non-human ape foot during bipedal walking with implications for the evolution of the foot.

The feet of apes have a different morphology from those of humans. Until now, it has merely been assumed that the morphology seen in humans must be adaptive for habitual bipedal walking, as the habitual use of bipedal walking is generally regarded as one of the most clear-cut differences between humans and apes. This study asks simply whether human skeletal proportions do actually enhance foot performance during human-like bipedalism, by examining the influence of foot proportions on force, torque and work in the foot joints during simulated bipedal walking. Skeletons of the common chimpanzee, orangutan, gorilla and human were represented by multi-rigid-body models, where the components of the foot make external contact via finite element surfaces. The models were driven by identical joint motion functions collected from experiments on human walking. Simulated contact forces between the ground and the foot were found to be reasonably comparable with measurements made during human walking using pressure- and force-platforms. Joint force, torque and work in the foot were then predicted. Within the limitations of our model, the results show that during simulated human-like bipedal walking, (1) the human and non-human ape (NHA) feet carry similar joint forces, although the distributions of the forces differ; (2) the NHA foot incurs larger joint torques than does the human foot, although the human foot has higher values in the first tarso-metatarsal and metatarso-phalangeal joints, whereas the NHA foot incurs higher values in the lateral digits; and (3) total work in the metatarso-phalangeal joints is lower in the human foot than in the NHA foot. The results indicate that human foot proportions are indeed well suited to performance in normal human walking.

Interdependence of torque, joint angle, angular velocity and muscle action during human multi-joint leg extension.

PURPOSE: Force and torque production of human muscles depends upon their lengths and contraction velocity. However, these factors are widely assumed to be independent of each other and the few studies that dealt with interactions of torque, angle and angular velocity are based on isolated single-joint movements. Thus, the purpose of this study was to determine force/torque-angle and force/torque-angular velocity properties for multi-joint leg extensions. METHODS: Human leg extension was investigated (n = 18) on a motor-driven leg press dynamometer while measuring external reaction forces at the feet. Extensor torque in the knee joint was calculated using inverse dynamics. Isometric contractions were performed at eight joint angle configurations of the lower limb corresponding to increments of 10° at the knee from 30 to 100° of knee flexion. Concentric and eccentric contractions were performed over the same range of motion at mean angular velocities of the knee from 30 to 240° s(-1). RESULTS: For contractions of increasing velocity, optimum knee angle shifted from 52 ± 7 to 64 ± 4° knee flexion. Furthermore, the curvature of the concentric force/torque-angular velocity relations varied with joint angles and maximum angular velocities increased from 866 ± 79 to 1,238 ± 132° s(-1) for 90-50° knee flexion. Normalised eccentric forces/torques ranged from 0.85 ± 0.12 to 1.32 ± 0.16 of their isometric reference, only showing significant increases above isometric and an effect of angular velocity for joint angles greater than optimum knee angle. CONCLUSIONS: The findings reveal that force/torque production during multi-joint leg extension depends on the combined effects of angle and angular velocity. This finding should be accounted for in modelling and optimisation of human movement.

Minimally invasive reduction and fixation of displaced calcaneal fractures: surgical technique and radiographic analysis.

PURPOSE: The optimal treatment of calcaneal fractures is controversial. A specific subgroup of healthy patients has good outcomes with open reduction and internal fixation using an extensile lateral approach. However, there are many patients who do not fit into this category. Consequently, they are either denied surgical intervention or put at significant risk of developing complications as a result of open surgical intervention. Minimally invasive reduction and fixation (MIRF) of calcaneal fractures can restore the height, width, length and shape of the hindfoot in addition to restoring the orientation of the posterior facet of the calcaneus (Böhler's angle). METHODS: We present a series of 31 patients treated with minimally invasive reduction and fixation technique using threaded K wires and Steinmann pins as an alternative treatment method in patients who are not suitable for open reduction and internal fixation. RESULTS: The mean time to surgery from injury was six days (range one to ten days). The mean duration of surgery was 35 minutes (range 11-52 minutes). The mean followup was 14.9 months (range of seven to 30 months). The mean change in Böhler's angle and length of the calcaneus from intra-operative fixation to final followup were 18.7° and 4.7 mm, respectively. The complication rate was low and there was one case of a superficial wound infection and no cases of deep infection or peroneal impingement in this series. CONCLUSION: The MIRF technique with the use of threaded K wires has not been previously described in the literature. In our experience, the operative time is short and can be safely performed even in the presence of extensive soft tissue swelling in the immediate period following injury. The infection risk is low and calcaneal morphology was improved and maintained in terms of Böhler's angle. This technique is suitable to be considered in patients who have significant medical co-morbidities (smokers, diabetics, peripheral vascular disease) and in those patients who are not suitable for an extensile lateral approach and internal fixation.