Influence of shoes and foot orthoses on lower extremity muscle activation onset times in healthy subjects during the transition from double-leg stance to single-leg stance

AIM

The aim of this study was to evaluate the influence of shoes and foot orthoses on lower extremity muscle activation patterns in healthy subjects during the transition from double-leg stance to single-leg stance.

METHODS

Eight male and seven female young asymptomatic adults who wear foot orthoses were recruited. Muscle activation onset times of 9 lower extremity muscles were recorded using surface electromyography during the transition from double-leg stance to single-leg stance, performed with eyes open and with eyes closed. This was tested in 4 experimental conditions: 1) barefoot (BF); 2) shoes only (SO); 3) shoes with standardized FO (SSFO); and 4) shoes with customized FO (SCFO).

RESULTS

Based on a four-way (condition-region-leg-vision) linear model for repeated measures, we found a significant condition effect (P=0.025). Differences between conditions did not depend on the leg and/or the vision condition, but on the region (ankle-knee-hip). Based on a two-way (condition-muscle) linear model within each region, only significant differences between conditions for peroneus longus (P=0.003) were found. The onset times of peroneus longus were significantly earlier in SO (P=0.029) and SCFO (P=0.001) compared to BF.

CONCLUSION

These results indicate that SO and SCFO can accelerate peroneus longus muscle activation onset times during the transition from double-leg stance to single-leg stance. Further research is required to determine how these adaptations may develop over time.

Acute injury in the peripheral nervous system triggers an alternative macrophage response

BACKGROUND

The activation of the immune system in neurodegeneration has detrimental as well as beneficial effects. Which aspects of this immune response aggravate the neurodegenerative breakdown and which stimulate regeneration remains an open question. To unravel the neuroprotective aspects of the immune system we focused on a model of acute peripheral nerve injury, in which the immune system was shown to be protective.

METHODS

To determine the type of immune response triggered after axotomy of the sciatic nerve, a model for Wallerian degeneration in the peripheral nervous system, we evaluated markers representing the two extremes of a type I and type II immune response (classical vs. alternative) using real-time quantitative polymerase chain reaction (RT-qPCR), western blot, and immunohistochemistry.

RESULTS

Our results showed that acute peripheral nerve injury triggers an anti-inflammatory and immunosuppressive response, rather than a pro-inflammatory response. This was reflected by the complete absence of classical macrophage markers (iNOS, IFN γ, and IL12p40), and the strong up-regulation of tissue repair markers (arginase-1, Ym1, and Trem2). The signal favoring the alternative macrophage environment was induced immediately after nerve damage and appeared to be established within the nerve, well before the infiltration of macrophages. In addition, negative regulators of the innate immune response, as well as the anti-inflammatory cytokine IL-10 were induced. The strict regulation of the immune system dampens the potential tissue damaging effects of an over-activated response.

CONCLUSIONS

We here demonstrate that acute peripheral nerve injury triggers an inherent protective environment by inducing the M2 phenotype of macrophages and the expression of arginase-1. We believe that the M2 phenotype, associated with a sterile inflammatory response and tissue repair, might explain their neuroprotective capacity. As such, shifting the neurodegeneration-induced immune responses towards an M2/Th2 response could be an important therapeutic strategy.

The Weil osteotomy of the lesser metatarsals: a clinical and pedobarographic follow-up study

The clinical results with pedobarographic analysis were assessed in 32 patients (59 metatarsals) who underwent a distal metatarsal shortening (Weil) osteotomy for either intractable plantar keratoses or chronically dislocated lesser metatarsal phalangeal joints. All patients had increased pressure under the involved metatarsal heads. Thirty three of the 59 metatarsophalangeal (MTP) joints were chronically dislocated. At an average follow-up of 30 months, patients rated the result as excellent or good for 32 of the 37 feet (86%). The mean preoperative AOFAS score was 59 (maximum 100), which improved to 81 post-operatively. This difference is significant: p = 0.00001 (with t-test). Comparison of the pre and post-operative pedobarographic measurements showed a significant decreased load under the affected metatarsal heads (p = 0.05). A complete disappearance of the callus was noted under 44 operated metatarsals (75%) and partial disappearance under 12 metatarsals (20%). Two symptomatic transfer lesions occurred under an adjacent metatarsal head. Recurrent dislocations occurred in 5 joints (15%). While metatarsophalangeal joint range of motion was significantly diminished, toe strength was maintained. Average metatarsal shortening was 5.9 mm with no nonunions, delayed unions, or malunions. The Weil shortening osteotomy is a simple and reliable procedure which can effectively reduce the load under the lesser metatarsophalangeal joints and is helpful for the reduction of dorsally dislocated MTP joints.

Plantar force distribution in Parkinsonian gait: a comparison between patients and age-matched control subjects

This study aimed to ascertain whether roll-off of the feet during gait was essentially different in patients with Parkinson's disease from that of elderly control subjects. Twenty-two patients, belonging mainly to Hoehn & Yahr grades III and IV, and 30 elderly people participated in the study. Plantar force distribution data were collected of two consecutive strides using pressure-sensitive insoles as part of the pododynograph system. Results showed that when correcting for gait speed and sex differences, patients with Parkinson's disease walked with significantly lower relative peak forces at the forefoot and heel and increased load at the midfoot. The onset of peak forces indicated slower load acceptance on the heel and early forefoot loading which was confirmed by a reduced amplitude of the centre of force along the length of the foot compared with healthy controls. Roll-off was significantly reduced in patients with Parkinson, a feature which was specific for the disease rather than a result of reduced gait speed alone.

Forefoot reconstruction in rheumatoid arthritis patients: Keller-Lelièvre-Hoffmann versus arthrodesis MTP1-Hoffmann

The aim of this study was to compare the subjective, clinical and pedodynographic results of two large groups of patients operated on in our department. From January 1987 to December 1992, 38 rheumatoid patients (59 feet) underwent a Keller-Lelièvre arthroplasty of the first metatarsophalangeal (MTP1) joint and a Hoffmann resection of the lesser metatarsal heads. The mean follow-up was 35 months. From June 1992 to August 1997 48 patients (62 feet) with rheumatoid arthritis underwent an arthrodesis of the MTP1 joint and Hoffmann resection of the lesser metatarsal heads. The mean follow-up was 25 months. In 10 feet the arthrodesis was performed as a revision procedure of a failed Keller-Lelièvre arthroplasty. The patients of both series were assessed in the same way: personal interview, clinical examination, radiographs, bilateral footprints, and pedodynographic measurements. Static and dynamic pedodynographic measurements were taken with a 64-sensor matrix insole in a standard shoe. Six of our patients had an arthrodesis-Hoffmann procedure performed on one foot and a Keller-Lelièvre-Hoffmann procedure on the contralateral side. Although there is better loadbearing of the first ray with relative unloading of the central metatarsal heads in the arthrodesis MTP1-Hoffmann group, subjective evaluation of the procedure was slightly better in the Keller-Lelièvre-Hoffmann group. Ninety-three percent of the patients in the Keller group were satisfied or satisfied with minor reservations versus 87 percent in the arthrodesis group. This difference is not statistically significant. Recurrent deformity was not more prominent in the Keller-Lelièvre-Hoffmann group; however, it may be that with a longer follow-up, the feet in the arthrodesis-Hoffmann group hold up better over time. The arthrodesis MTP1-Hoffmann procedure can be used as a revision procedure for a failed Keller- Hoffmann operation, although these procedures were more difficult and needed a longer recovery time than the primary MTP1 arthrodesis.

Results after cheilectomy in athletes with hallux rigidus

From 1987 to 1993, 20 athletes (22 feet) underwent cheilectomy for Regnauld grade I, grade II hallux rigidus. Average age was 31 years (10 men and 12 women); mean follow-up was at 5.1 years. All patients performed high-level sports (judo, track & field, soccer, and skating). Indications for surgery included failure of nonsurgical treatment with persistent pain during sports activities, shoefitting problems, and recurrent bursitis. The aim of our study was to evaluate the results clinically, radiographically, and objectively, using dynamic and static pedodynographic measurements. After a mean follow-up of 5 years, cheilectomy was demonstrated to be a reliable treatment method in athletes with Regnauld grades 1 and 2 hallux rigidus. Functionally, 14 excellent, seven good, and one fair result were noted. Radiological progression was noted in 7 of 13 patients, with a follow-up of >4 years. Postoperative dynamic pedodynographic findings demonstrated moderate but significant changes in peak pressures under the first metatarsal head, the hallux, and in the center of pressure distribution under the forefoot.

The use of an advanced reciprocating gait orthosis by paraplegic individuals: a follow-up study

This article describes the results of a follow-up study of 14 paraplegic individuals who were fitted with the ARGO (Advanced Reciprocating Gait Orthosis--STEEPER) at least 1 year previously. It was found that 85% were still using the apparatus on a regular basis. The general satisfaction of the users was high, although the functional use was limited. Therapeutic reasons appeared to be the main reason for wearing the ARGO. The points that were most appreciated were the psychological and physiological benefits of standing and walking. Discussion with the users who were paraplegic provided valuable information concerning possible technical improvements to the ARGO.

Pedodynographic measurements after forefoot reconstruction in rheumatoid arthritis patients

From January 1987 to December 1992, 38 patients (59 feet) with rheumatoid arthritis underwent reconstruction of the forefoot using Keller-Lelièvre arthroplasty of the first metatarsophalangeal joint and Hoffman resection of the lesser metatarsal heads. The average age of the patients was 61.3 years, with both feet involved in 21 patients and 17 with single foot involvement. The aim of our study was to evaluate the results both on a functional and an objective basis using dynamic and static pedodynographic measurements. Attention was given to dynamic pressure measurements under the metatarsal heads, the center of pressure distribution, gait analysis, and peak loads taken on different areas of the forefoot during normal walking. Correlations were made between these measurements and symptoms. After a mean follow-up time of 35 months, the clinical results were satisfactory in 54%, satisfactory with some reservations in 39%, satisfactory with major reservations in 3%, and unsatisfactory in 3% of patients.

Development of an above-knee prosthesis equipped with a microcomputer-controlled knee joint: first test results

The shortcomings of conventional above-knee prostheses are due to their lack of adaptive control. Implementation of a microcomputer controlling the knee joint in a passive way has been suggested to enhance the patient's gait comfort, safety and cosmesis. This approach was used in the design of a new prosthetic system for the above-knee amputee, and tested on one patient. The knee joint of a conventional, modular prosthesis was replaced by a knee joint mechanism, equipped with a controllable brake on the knee joint axis. Sensors and a microcomputer were added, keeping the system self-contained. The modularity of the design permits the use of an alternative, external, PC-based control unit, emulating the self-contained one, and offering extended data monitoring and storage facilities. For both units an operating environment was written, including sensor/actuator interfacing and the implementation of a real-time interrupt, executing the control algorithm. A double finite state approach was used in the design of the control algorithm. On a higher level, the mode identification algorithm reveals the patient's intent. Within a specific mode (lower level), the relevant mode control algorithm looks for the current phase within the gait cycle. Within a particular phase, a specific simple control action with the brake replaces normal knee muscle activity. Tests were carried out with one prosthetic patient using a basic control algorithm for level walking, allowing controlled knee flexion during stance phase. The technical feasibility of such a concept is illustrated by the test results, even though only flexion during early stance phase was controlled during the trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of EMG-based mode and intent recognition algorithms for a computer-controlled above-knee prosthesis

Conventional above-knee prostheses are unable to replace normal leg function due to the lack of adaptive control. Computer-controlled prostheses offer the possibility to implement such adaptive control. For a particular locomotion mode, control algorithms can generate appropriate damping profiles as a function of selected sensory inputs and stored information on normal walking. However, it is essential in such systems that the locomotor modes can be determined accurately from the inputs of the control system. Recognition of the intent to change from one mode to another is also a necessity because the control system has to account for such transitions. The possibility of using EMG signals from hip muscles and muscle residuals of the stump for this purpose is investigated. The modes tested are level walking, ramp ascent and ramp descent with slopes of 6 degrees and 9 degrees. EMG activity curves for three muscles: gluteus maximus, gluteus medius and tensor fasciae latae, are presented for the different modes. The results are obtained from two reference groups of 12 normal individuals and from a prosthetic patient. The results show the possibility of discriminating between modes. A discussion is made of the implementation of the results obtained by a finite state approach and the difficulties relating to the use of EMG signals for control purposes.