A voluntary activation deficit in m. abductor hallucis exists in asymptomatic feet.

M. abductor hallucis (AbH) is the strongest intrinsic foot muscle and its dysfunction underlies various foot disorders. Attempts to strengthen the muscle by voluntary exercises are constrained by its complex morphology and oblique mechanical action, which leads to an inability even in asymptomatic individuals to fully activate AbH. This study investigated the extent and magnitude of this inability whilst also providing preliminary evidence for the virtue of targeted sub-maximum neuromuscular electrical stimulation (NMES) as a countermeasure for an AbH activation deficit. The voluntary activation ratio (VAR) was assessed via the twitch interpolation technique in the left AbH of 13 healthy participants during maximum voluntary 1st metatarsophalangeal joint flexion-abduction contractions (MVC). Participants were grouped ("able" or "unable") based on their ability to fully activate AbH (VAR ≥ 0.9). 7 s-NMES trains (20 Hz) were then delivered to AbH with current intensity increasing from 150% to 300% motor threshold (MT) in 25% increments. Perceived comfort was recorded (10 cm-visual analogue scale; VAS). Only 3 participants were able to activate AbH to its full capacity (able, mean (range) VAR: 0.93 (0.91-0.95), n = 3; unable: 0.69 (0.36-0.83), n = 10). However, the maximum absolute forces produced during the graded sub-maximum direct-muscle NMES protocol were comparable between groups implying that the peripheral contractility of AbH is intact irrespective of the inability of individuals to voluntary activate AbH to its full capacity. These findings demonstrate that direct-muscle NMES overcomes the prevailing inability for high voluntary AbH activation and therefore offers the potential to strengthen the healthy foot and restore function in the pathological foot.

Direct muscle electrical stimulation as a method for the in vivo assessment of force production in m. abductor hallucis.

In vivo assessment of the force-generating capacity of m. abductor hallucis (AbH) is problematic due to its combined abduction-flexion action and the inability of some individuals to voluntarily activate the muscle. This study investigated direct muscle electrical stimulation as a method to assess isometric force production in AbH about the 1st metatarsal phalangeal joint (1MPJ) at different muscle-tendon lengths, with the aim of identifying an optimal angle for force production. A 7 s stimulation train was delivered at 20 Hz pulse frequency and sub-maximal (150% motor threshold) intensity to the AbH of the left foot in 16 participants whilst seated, and with the Hallux suspended from a force transducer in 0°,5°,10°,15° and 20° 1MPJ dorsal flexion. Reflective markers positioned on the foot and force transducer were tracked with 5 optical cameras to continuously record the force profile and calculate the external 1MPJ joint flexion moment at each joint configuration. A parabolic relationship was found between AbH force production and 1MPJ configuration. The highest 1MPJ joint moments induced by electrical stimulation were found between 10° and 15° of Hallux dorsal flexion. However, the joint angle (p < 0.001; η2 = 0.86) changed significantly across all but one 1MPJ configurations tested during the stimulation-evoked contraction, resulting in a significant change in the corresponding external moment arm (p < 0.001; η2 = 0.83). Therefore, the changes in joint geometry during contraction should be accounted for to prevent an underestimation of the resulting joint moment. We conclude that direct muscle electrical stimulation combined with dynamometry offers a robust method for standardised assessment of AbH sub-maximal isometric force production.

Trampoline Park Injuries and Their Burden on Local Orthopaedic and Emergency Services.

OBJECTIVE: To investigate the incidence of trampoline park injuries (TPIs) at a local recreational facility and to quantify the burden on emergency and orthopaedic services at our institute. METHODS: All patients that presented to the Emergency Department (ED) from the trampoline park via ambulance from July 2014 to November 2015 were included in the study. Patients' medical records were reviewed for clinical details including date, location and type of injury, treatment received, length of stay and outpatient follow-up. A cost analysis was performed to estimate the financial impact of each injury. RESULTS: A total of 71 patients were included in the study, with a mean age of 20 (7-48). Soft tissue sprains (n=29, 41%) and fractures (n=25, 35%) were the most common injuries, with the majority occurring in the lower limb. Two patients sustained open tibial fractures necessitating transfer to level 1 trauma centres. Fourteen patients (20%) underwent surgery, predominantly requiring open reduction and internal fixation. Overall, 18 patients (25%) required admission to hospital with mean length of stay of 2 days. The cost for pre-hospital, emergency and in-patient care amounted to over £80,000. CONCLUSION: TPIs pose a significant financial cost for local orthopaedic and emergency services. Contrary to studies evaluating home trampoline injuries, the majority of fractures at trampoline parks occurred in the lower limbs. Improved injury prevention strategies are required to help reduce morbidity and lower the financial implications for local NHS trusts.

Wide-pulse, high-frequency, low-intensity neuromuscular electrical stimulation has potential for targeted strengthening of an intrinsic foot muscle: a feasibility study.

BACKGROUND: Strengthening the intrinsic foot muscles is a poorly understood and largely overlooked area. In this study, we explore the feasibility of strengthening m. abductor hallucis (AH) with a specific paradigm of neuromuscular electrical stimulation; one which is low-intensity in nature and designed to interleave physiologically-relevant low frequency stimulation with high-frequencies to enhance effective current delivery to spinal motoneurones, and enable a proportion of force produced by the target muscle to be generated from a central origin. We use standard neurophysiological measurements to evaluate the acute (~ 30 min) peripheral and central adaptations in healthy individuals. METHODS: The AH in the dominant foot of nine healthy participants was stimulated with 24 × 15 s trains of square wave (1 ms), constant current (150% of motor threshold), alternating (20 Hz-100 Hz) neuromuscular electrical stimulation interspersed with 45 s rest. Prior to the intervention, peripheral variables were evoked from the AH compound muscle action potential (Mwave) and corresponding twitch force in response to supramaximal (130%) medial plantar nerve stimulation. Central variables were evoked from the motor evoked potential (MEP) in response to suprathreshold (150%) transcranial magnetic stimulation of the motor cortex corresponding to the AH pathway. Follow-up testing occurred immediately, and 30 min after the intervention. In addition, the force-time-integrals (FTI) from the 1st and 24th WPHF trains were analysed as an index of muscle fatigue. All variables except FTI (T-test) were entered for statistical analysis using a single factor repeated measures ANOVA with alpha set at 0.05. RESULTS: FTI was significantly lower at the end of the electrical intervention compared to that evoked by the first train (p < 0.01). Only significant peripheral nervous system adaptations were observed, consistent with the onset of low-frequency fatigue in the muscle. In most of these variables, the effects persisted for 30 min after the intervention. CONCLUSIONS: An acute session of wide-pulse, high-frequency, low-intensity electrical stimulation delivered directly to abductor hallucis in healthy feet induces muscle fatigue via adaptations at the peripheral level of the neuromuscular system. Our findings would appear to represent the first step in muscle adaptation to training; therefore, there is potential for using WPHF for intrinsic foot muscle strengthening.

Cadaveric experiments to evaluate pressure wave generated by radial shockwave treatment of plantar fasciitis.

BACKGROUND: Shockwave treatment is increasingly used for plantar fasciitis and Achilles tendinopathy. To be effective it is believed that high pressure must be achieved in the tissues. We report on the first human cadaveric experiments to characterize pressure from radial shockwave therapy (rSWT) for plantar fasciitis. METHODS: The pressure from rSWT was measured in two cadaveric feet using a needle hydrophone. Maximal pressure and energy flux were calculated from the measurements. RESULTS: The pressure persisted longer than supposed, for up to 400µs. The peak negative pressure was up to two Mega Pascal. The predicted energy in the tissue strongly depended on the time interval used in calculations. CONCLUSIONS: The measured pressure may be sufficiently high to cause cavitation in the tissue, which is one of the proposed healing mechanisms associated with rSWT. The results suggest that the energy is imparted to the tissues for much longer than previously thought.

Syndesmosis Stabilisation: Screws Versus Flexible Fixation.

Orthopedic surgery is not short of situations where there is controversy regarding optimum management. Treating ankle syndesmosis injuries is an example where practice varies widely and there are many questions that remain unsatisfactorily answered. When addressing the type of syndesmosis stabilization that is required it is essential to ascertain the extent of instability. Only then can a logical approach to restoring the ankle mortise be achieved. Fixation of fibula shaft fractures and posterior malleolus fractures can restore sufficient stability to render syndesmosis stabilization unnecessary. The indications and techniques for stabilizing the distal tibiofibular joint are reviewed with clinical examples.

Finite element modelling of radial shock wave therapy for chronic plantar fasciitis.

Therapeutic use of high-amplitude pressure waves, or shock wave therapy (SWT), is emerging as a popular method for treating musculoskeletal disorders. However, the mechanism(s) through which this technique promotes healing are unclear. Finite element models of a shock wave source and the foot were constructed to gain a better understanding of the mechanical stimuli that SWT produces in the context of plantar fasciitis treatment. The model of the shock wave source was based on the geometry of an actual radial shock wave device, in which pressure waves are generated through the collision of two metallic objects: a projectile and an applicator. The foot model was based on the geometry reconstructed from magnetic resonance images of a volunteer and it comprised bones, cartilage, soft tissue, plantar fascia, and Achilles tendon. Dynamic simulations were conducted of a single and of two successive shock wave pulses administered to the foot. The collision between the projectile and the applicator resulted in a stress wave in the applicator. This wave was transmitted into the soft tissue in the form of compression-rarefaction pressure waves with an amplitude of the order of several MPa. The negative pressure at the plantar fascia reached values of over 1.5 MPa, which could be sufficient to generate cavitation in the tissue. The results also show that multiple shock wave pulses may have a cumulative effect in terms of strain energy accumulation in the foot.

Gastrocnemius shortening and heel pain.

Pain and reduced function caused by disorders of either the plantar fascia or the Achilles tendon are common. Although heel pain is not a major public health problem it affects millions of people each year. For most patients, time and first-line treatments allow symptoms to resolve. A proportion of patients have resistant symptoms. Managing these recalcitrant cases is a challenge. Gastrocnemius contracture produces increased strain in both the Achilles tendon and the plantar fascia. This biomechanical feature must be properly assessed otherwise treatment is compromised.

Biomechanical analysis of endobutton versus screw fixation after Lisfranc ligament complex sectioning.

BACKGROUND: Our goal was to compare diastasis after endobutton and screw fixation after Lisfranc ligament complex sectioning. METHODS: Twenty-four (12 pairs) fresh-frozen cadaveric feet were assigned to endobutton or screw fixation and loaded to 343N. Displacement (first-second metatarsal bases) was measured in intact feet and after ligament sectioning (Lisfranc, medial-intermediate cuneiform ligaments), fixation, and 10,000 cycles. RESULTS: The mean change in diastasis for endobutton and screw fixation under initial loading was 1.0mm (95% CI, 0.2-1.9mm) and 0.0mm (95% CI, -0.4 to 0.4mm), respectively (p=0.017). After cyclic loading, diastasis decreased (mean, -0.7mm, 95% CI, -1.2 to -0.1mm) in the endobutton group but was unchanged in the screw group (p=0.035). CONCLUSIONS: Diastasis after endobutton fixation was significantly greater than after screw fixation under initial loading but did not increase further after cyclic loading.

Results of proximal medial gastrocnemius release for Achilles tendinopathy.

BACKGROUND: Most patients with Achilles tendinopathy (AT) are treated successfully with physiotherapy involving eccentric calf training. In some patients, gastrocnemius contracture persists and there are reports of improvement following gastrocnemius release. We present the first series of patients to have proximal medial gastrocnemius release (PMGR) for AT. METHOD: 16 PMGRs (12 patients) were performed at our institution over a 2-year period. Nine patients (10 PMGRs) were available for follow-up. The mean age of patients was 45 years (range, 25-63 years), with 5 female and 4 male subjects. The average follow-up period was 2.5 years (range, 1.7-3.3 years). The sample was divided into noninsertional and insertional tendinopathy, with 5 PMGRs per group. Outcome measures were visual analog scale (VAS) scores, Victorian Institute of Sport Assessment-Achilles (VISA-A) scores, American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, and overall satisfaction. Complications and further procedures were also recorded. RESULTS: At an average of 2.5 years of follow-up, 6 out of 9 patients were highly satisfied. The noninsertional tendinopathy group enjoyed better results than the insertional group: mean VISA-A scores improved by 59% (noninsertional) versus 22% (insertional); mean AOFAS scores improved by 29% (noninsertional) versus 15% (insertional). The improvement in the noninsertional group was statistically significant (P < .05) for all 3 outcome measures. CONCLUSION: PMGR was an outpatient procedure that was well tolerated without wound healing concerns due to the proximally based incision. Patients with noninsertional tendinopathy who have failed conservative treatment can expect notable improvement, with VISA-A scores possibly normalizing after the procedure. We recommend PMGR for patients suffering recalcitrant noninsertional AT in whom gastrocnemius contracture persists despite an eccentric stretching program. LEVEL OF EVIDENCE: Level IV, case series.

Flexor digitorum longus tendon harvest length utilising a limited operative exposure: A cadaveric study.

BACKGROUND: Flexor digitorum longus (FDL) is a commonly used donor tendon for transfer to substitute for a dysfunctional tibialis posterior in the management of adult acquired flatfoot deformity. The tendon transfer is attached to the navicular bone via a drill hole. Interference-fit screws are an alternative means of securing a transferred tendon allowing for a shorter length of graft and less extensive dissection. The aim of this cadaveric study was to investigate the length of FDL tendon harvest required for transfer and to determine if this length of tendon can be obtained without formal dissection to the Knot of Henry. METHODS AND RESULTS: The FDL tendon was exposed in 8 cadaveric specimens via a medial hindfoot incision. The tendon was divided proximal to the Knot of Henry. The lengths of the skin incisions and the length of the FDL tendon harvest were measured. No specialist tendon harvesting instruments were used. The average length of the skin incision was 9.0cm (95% confidence intervals 8.0-10.0cm). The average length of the harvested FDL tendon was 6.7cm (95% confidence intervals 6.4-7.0cm). CONCLUSION: This study demonstrates that the FDL tendon can be safely and adequately harvested via a limited exposure. The average length of FDL tendon harvest via this approach compares favourably with other descriptions of approaches. This shorter graft length is more than adequate, allowing at least 2cm for fixation by interference screw to a tunnel in the navicular bone.

Proximal medial gastrocnemius release in the treatment of recalcitrant plantar fasciitis.

BACKGROUND: Isolated gastrocnemius contracture has been implicated as the cause of a number of foot and ankle conditions. Plantar fasciitis (PF) is one such condition that can be secondary to altered foot biomechanics as a result of gastrocnemius contracture. In this paper, we report our results with an isolated release of the proximal medial head of gastrocnemius for recalcitrant PF. METHODS: We prospectively followed a consecutive series of 21 heels in 17 patients following a Proximal Medial Gastrocnemius Release (PMGR). PF was diagnosed clinically and confirmed radiologically in all cases. To be included, at least 1~year of conservative treatment must have been tried and an isolated gastrocnemius contracture confirmed clinically using Silfverskiold's test preoperatively. Outcome measures included a 5-point Likert scale as well as subjective and objective calf weakness assessments. Final followup was on average 24 (range, 8 to 36) months after the surgery. RESULTS: Seventeen of the 21 heels (81%) reported total or significant pain relief following the surgery and none reported worsening of their symptoms. The majority did not have subjective or objective evidence of calf weakness. There were no `major' complications and only one case that suffered a `minor' complication. CONCLUSION: We believe a PMGR is a simple way of treating a patient with PF who has failed to respond to conservative management. In our series, the results were favorable, the recovery fast and the morbidity low.

Revision surgery of the lesser toes.

Surgery of the lesser toes is a difficult balancing act, and revision procedures are challenging. It is vastly preferable that the correct procedure be chosen for the correct patient and performed properly from the outset. The flow charts below (Figs. 23­25) are not a rigid protocol, but rather the authors' personal algorithm, based on their own experience, which may help other surgeons facing a stiff, deformed or flail toe to make a reasoned decision.

Idiopathic toe walking and contractures of the triceps surae.

Toe walking is a common feature in immature gait and is considered normal up to 3 years of age. As walking ability improves, initial contact is made with the heel. Toe-walkers will stand out as different once heel-strike is achieved by most of their peers. This difference gives rise to parental concern. Therefore toe-walkers are often referred at 3 years of age. This article examines the evidence for the management of children who have idiopathic toe walking and reviews the literature on surgery for the lengthening of a calf contracture.

Detecting patient allergy: beware the LIE.

INTRODUCTION: Allergy detection is important in surgical patients. Historically, the focus has been on drug allergies. There is increasing focus on non-drug allergy, specifically latex, iodine and elastoplast. PATIENTS AND METHODS: The practice and knowledge of 24 pre-registration house officers was evaluated, with regard to patient allergy. For the second phase of the study, the cohort of 367 consecutive patients presenting to the orthopaedic pre-assessment clinic was prospectively assessed. RESULTS: This prospective study demonstrates that standard history-taking misses a large number (38%) of such allergies. CONCLUSIONS: With regard to allergy detection, we are living a LIE (by ignoring latex, iodine, elastoplast allergy). We suggest junior doctors should employ the mnemonic LIED (latex, iodine, elastoplast and drugs) when taking a medical history.

Biomechanical comparison of two fixation methods for first metatarsophalangeal joint arthrodesis.

PURPOSE: The aim of this study was to compare the mechanical stability of two methods of fixation for arthrodesis of the hallux metatarsophalangeal joint: 1. a technique using an intramedullary screw and 2. a standard technique using crossed interfragmentary compression screws. METHODOLOGY: The metatarsophalangeal joint was mechanically evaluated in cantilever bending using a servohydraulic testing machine. Differences in stiffness and strength parameters between the two techniques were checked for significance (P<0.05) using a paired t-test. RESULTS: Fixation provided by the intramedullary screw was stiffer and stronger than that from crossed compression screws. CONCLUSIONS: The stronger and stiffer intramedullary screw technique offers mechanical advantages over the crossed interfragmentary screw technique.