Foot orientation and lower limb kinematics during running

Early results and complication rate of the LapiCotton procedure in the treatment of medial longitudinal arch collapse: a prospective cohort study

INTRODUCTION

Instability/collapse of the medial column has been associated with many conditions, particularly progressive collapsing foot deformity (PCFD), hallux valgus (HV), and midfoot arthritis (MA). Restoration of first ray length and sagittal plane alignment to restore the foot tripod is essential when treating these deformities. This study aimed to assess early results, healing, and complication rate of a distraction dorsal opening plantarflexion wedge allograft first tarsometatarsal joint fusion (LapiCotton Procedure) in patients with collapse/instability of the medial column.

METHODS

In this prospective cohort study, we included PCFD, HV, and MA patients that underwent a LapiCotton procedure. Fusion site healing was defined by > 50% bone bridging in both interfaces between allograft wedge and host bone using weight-bearing computed tomography (WBCT) after 3 months. First ray collapse radiographic correction and minor and major complications (deep dehiscence, deep infection, and reoperation) were assessed.

RESULTS

A total of 22 patients (22 feet) were included (11 PCFD, 6 MA, and 5 of HV patients). Mean follow-up was 5.9 months (range 3-12) and median allograft size was 8 mm (range 5-19 mm). Bone healing was observed in 91% of cases. Two minor complications (9%, both superficial dehiscence) and one major complication (4.5%, deep infection) were observed. Statistically significant improvement of the sagittal plane talus-first metatarsal angle was observed, with mean improvement of 9.4° (95% CI 6.7-12.1°; p < 0.0001).

CONCLUSION

In this prospective cohort study of 22 patients treated with the LapiCotton procedure for medial longitudinal arch collapse/instability, we observed a low complication rate (9% minor, 4.5% major), high healing rate after 3 months (91%), one clinically stable radiographic non-union (4.5%) and one unstable non-union (4.5%) needing reoperation. Our results demonstrate promising initial results for LapiCotton technique in treating collapse of the medial longitudinal arch in patients with PCFD, MA and HV deformities. Long-term results are needed to confirm these promising results.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Effect of Strike Pattern and Orthotic Intervention on Tibial Shock during Running

The main purpose of this study was to investigate the effects of both strike pattern (forefoot vs. rearfoot strike pattern) and orthotic intervention on shock to the lower extremity. Semi-rigid orthotic devices were manufactured for 15 injury-free recreational runners. Tibial accelerometry, ground reaction force, and 3D kinematic data were collected on their right leg in four conditions: forefoot strike (FFS) and rearfoot strike (RFS) with and without orthotics. Two-way repeated-measures analysis of variance tests were used to assess the effects of strike pattern and orthotic intervention on tibial acceleration; angular excursions of the ankle and knee; ground reaction force (GRF) vertical and anteroposterior peaks and load rates; and ankle, knee, and leg stiffness. There was a significant increase in tibial acceleration for the FFS pattern compared to the RFS pattern. This may be explained in part by the significantly greater peak vertical GRF, peak anteroposterior GRF, anteroposterior GRF load rates, knee stiffness, and leg stiffness found in the FFS pattern compared to the RFS pattern. Tibial acceleration and rearfoot eversion excursions were similar between the orthotic and no-orthotic conditions. Knee flexion excursion and average GRF vertical load rates were significantly decreased while dorsiflexion excursion and knee stiffness were significantly increased in the orthotic condition. No significant interactions were found between strike pattern and orthotic condition for any variables assessed.

Rotational foot placement specifies the lever arm of the ground reaction force during the push-off phase of walking initiation

The lever arm of the ground reaction force (GRF) about the talocrural joint axis is a functionally important indicator of the nature of foot loading. Walking initiation experiments (ten subjects; age, 23-29 years) were completed to demonstrate that rotational foot placement is a possible strategy to specify the lever arm. Externally-rotated foot placement resulted in larger lever arms during push-off. A computer simulation of push-off revealed that a decreased lever arm reduces the plantarflexion moment necessary to maintain a constant forward velocity, while increasing the required plantarflexion velocity. Shortening of the foot thus diminishes the muscular force demand but also requires high muscle fiber shortening velocities that may limit the force generating capacity of plantar flexors. Decreased plantar flexion moment and slow walking previously noted in partial-foot amputees may result from shortened lever arms in this manner.

Integrated pressure-force-kinematics measuring system for the characterisation of plantar foot loading during locomotion

Plantar pressure, ground reaction force and body-segment kinematics measurements are largely used in gait analysis to characterise normal and abnormal function of the human foot. The combination of all these data together provides a more exhaustive, detailed and accurate view of foot loading during activities than traditional measurement systems alone do. A prototype system is presented that integrates a pressure platform, a force platform and a 3D anatomical tracking system to acquire combined information about foot function and loading. A stereophotogrammetric system and an anatomically based protocol for foot segment kinematics is included in a previously devised piezo-dynamometric system that combines pressure and force measurements. Experimental validation tests are carried out to check for both spatial and time synchronisation. Misalignment of the three systems is found to be within 6.0, 5.0 and 1.5 mm for the stereophotogrammetric system, force platform and pressure platform, respectively. The combination of position and pressure data allows for a more accurate selection of plantar foot subareas on the footprint. Measurements are also taken on five healthy volunteers during level walking to verify the feasibility of the overall experimental protocol. Four main subareas are defined and identified, and the relevant vertical and shear force data are computed. The integrated system is effective when there is a need for loading measurements in specific plantar foot subareas. This is attractive both in clinical assessment and in biomechanics research.

Leg stiffness and foot orientations during running

This study was done to determine whether leg stiffness (Kleg) during running was related to rearfoot-to-forefoot angle in standing (RFAst) and running (RFArun). Footprints obtained from 32 subjects were used to calculate RFAst and RFArun, defined as positive when forefoot axis was abducted from rearfoot axis. A spring-mass model was used to calculate Kleg in running from ground reaction forces, measured by a force platform. The Kleg of runners (13.0 +/- 2.7 kN x m(-1)) was negatively correlated with RFAst (-8.4 degrees +/- 6.4 degrees) and RFArun (-0.4 degrees +/- 7.2 degrees). When runners were divided into opened foot (RFArun > 0; N = 19) and closed foot (RFArun < 0; N = 12) groups, the Kleg of opened foot runners was less than that of the closed runners. We suggest that foot structure is a factor responsible for the differences in leg stiffness observed in runners.