A case of fever and thrombocytopenia in a 33-year-old Special Forces Soldier with recent deployment to the Philippines is discussed, as are differential diagnosis and initial medical management at an ...overseas, fixed US military medical treatment facility. The authors discuss lessons learned that are applicable for Special Operations Forces (SOF) medical providers and recommend a renewed and continued emphasis on tropical medicine and infectious disease training for SOF medical providers.
Category:
Basic Sciences/Biologics
Introduction/Purpose:
Ankle arthroplasties are increasingly performed to address ankle arthritis. Patients with long standing ankle arthritis often present with an ...associated achilles tendon contracture. An open or percutaneous lengthening of the Achilles is commonly performed at the same time as the ankle arthroplasty to improve range of motion. Current ankle arthroplasty implants include mobile bearing and fixed bearing systems. Lengthening the achilles tendon improves dorsiflexion, however the effect of the lengthening on the ankle and subtalar joint is not well documented in the literature. Using a novel system to simulate weight bearing in a cadaveric model, we evaluated achilles tendon lengthening and its effect on ankle and subtalar joint orientation and load distribution. This may have potential implications to polyethylene implant longevity in total ankle arthroplasties.
Methods:
Five fresh frozen lower limb cadaveric specimens without known skeletal condition were used. The femoral head was potted with PMMA and TekScan pressure sensors were inserted into the ankle and subtalar joint. The specimens were placed on a custom jig, which allowed for load cell modulated loading of the leg; 75 lb load (half body weight)(4) was applied at the femoral head while the foot was supported against a fixed plate keeping the ankle in neutral position. Mean pressure (MP), peak pressure (PP), contact area (CA), and center of force (COF) were measured in both joints under two conditions; baseline (BASE), and following Achilles tendon release (TENDON) to simulate lengthening. Each condition was tested three times per specimen; the results were averaged per specimen and used for final analysis. Displacement of COF was calculated relative to its location at baseline.
Results:
The Mean Pressure (MP), Peak Pressure (PP) and Contact Area (CA) did not show a statistical difference in the ankle and subtalar joints between baseline (BASE) and TENDON (Achilles tendon release) conditions. (Table 1). Further, the displacement of the COF from the BASE to TENDON was 0.5 mm. In our model, the contracture of the muscle was not fully simulated. Further hindfoot kinetic studies with active achilles contracture may demonstrate a difference in contact forces in the ankle and subtalar joint as compared to normal.
Conclusion:
Ankle arthroplasty is becoming an effective treatment option for ankle joint arthritis. Our novel study demonstrates that Achilles tendon lengthening did not change the mean pressure, peak pressure, contact area center of force in the ankle and subtalar joint. This model provides validation for further studies evaluating tendon release and contact pressure changes in a cadaver with an implanted fixed bearing versus mobile bearing total ankle prosthesis. Difference in polyethylene wear may effect the longevity of ankle replacements. This study will provide clinicians additional information when evaluating the benefit/risks associated with lengthening the Achilles tendon for ankle arthroplasty patients.
Category:
Ankle, Basic Sciences/Biologics, Hindfoot, Biomechanics
Introduction/Purpose:
Orthotics are commonly prescribed by orthopaedic surgeons to address the hindfoot and midfoot deformity ...resulting from posterior tibial tendon dysfunction. The public however will often purchase over the counter orthotics for generalized complaints of foot pain that is not associated with any significant deformity or foot pathology. The mechanical axis of the lower limb may be altered in patients who use orthotics despite a normal foot alignment. We hypothesize that patients with normal alignment who use orthotics may adversely change ankle and subtalar joint orientation and load distribution.
Methods:
Five fresh frozen lower limb cadaveric specimens without known skeletal condition were used. The femoral head was potted with PMMA and TekScan pressure sensors were inserted into the ankle and subtalar joint. The specimens were placed on a custom jig, which allowed for load cell modulated loading of the leg; 75 lb load (half body weight) was applied at the femoral head while the foot was supported against a fixed plate keeping the ankle in neutral position. Testing was achieved by placing an orthotic under the medial half of the plantar talonavicular joint level. Mean pressure (MP), peak pressure (PP), contact area (CA), and center of force (COF) were measured in both the ankle and subtalar joints under three conditions; barefoot (BASE), with a 1.5 cm (ORT1) and 3 cm (ORT2) height orthotic. Each condition was tested three times per specimen. Displacement of COF was calculated relative to its location at baseline.
Results:
The MP, PP and CA showed a constant decrease from BASE to ORT1 and ORT2. Despite this relation, the only comparison that was significantly different was that between peak pressure values of the baseline and ORT2 conditions of the subtalar joint. The average displacement of COF from BASE was 0.14 mm and 0.42 mm medially, and 0.26 mm and 0.46 mm posteriorly at the ankle joint with ORT1 and ORT2 respectively. The average displacement of COF from BASE was 0.03 mm laterally and 0.08 mm posteriorly with ORT1, and 0.2 mm medially and 0.46 mm posteriorly with ORT2 at the subtalar joint.
Conclusion:
Foot deformities have an impact on the articular forces in the lower limb. Our results agree with previous studies about the role of foot deformity on the distribution of body weight forces and its consequences across the ankle and subtalar joint. Our novel study also demonstrates that orthotics and orthotics of varying sizes can change the mean pressure, peak pressure, contact area center of force in the ankle and subtalar joint. This study proves the feasibility of its design for studying intra-articular pressure changes in a lower limb cadaveric model with simulated weight bearing.
Background:
Foot orthoses are used to treat many disorders that affect the lower limb. These assistive devices have the potential to alter the forces, load distribution, and orientation within ...various joints in the foot and ankle. This study attempts to quantify the effects of orthoses on the intra-articular force distribution of the ankle and subtalar joint using a cadaveric testing jig to simulate weight bearing.
Methods:
Five lower-limb cadaveric specimens were placed on a custom jig, where a 334-N (75-lb) load was applied at the femoral head, and the foot was supported against a plate to simulate double-leg stance. Pressure-mapping sensors were inserted into the ankle and subtalar joint. Mean pressure, peak pressure, contact area, and center of force were measured in both the ankle and subtalar joints for barefoot and 2 medial foot orthosis conditions. The 2 orthosis conditions were performed using (1) a 1.5-cm-height wedge to simulate normal orthoses and (2) a 3-cm-height wedge to simulate oversized orthoses.
Results:
The contact area experienced in the subtalar joint significantly decreased during 3-cm orthotic posting of the medial arch, but neither orthosis had a significant effect on the spatial mean pressure or peak pressure experienced in either joint.
Conclusion:
The use of an oversized orthosis could lead to a decrease in the contact area and alterations in the distribution of pressure within the subtalar joint.
Clinical Relevance:
The use of inappropriate orthoses could negatively impact the force distribution in the lower limb.
•There is no consensus on the optimal treatment for Achilles tendon ruptures.•Achilles tendon lengthening after conservative treatment may alter ankle kinetics.•This study uses a cadaveric model that ...simulates static weight bearing to explore the effect of a lengthened Achilles tendon on ankle joint load distribution.•Achilles lengthening does not significantly change contact pressures of the ankle joint in this model.•Further studies are needed to address the effects of Achilles tendon lengthening on the ankle and elucidate the long-term clinical outcomes.
In recent years, primary Achilles tendon ruptures have increased due to the aging population's participation in physically demanding activities. These injuries commonly occur during recreational sports and frequently lead to a long-term reduction in activity despite treatment. Non-operative methods of treatment for Achilles tendon ruptures may result in the Achilles healing in a lengthened position compared to the pre-injury state. This study uses a cadaveric model that simulates static weight bearing to explore the effect of a lengthened Achilles tendon on ankle joint load distribution.
Five lower limb cadaveric specimens were placed on a custom jig, where a 334 N (75 lb) load was applied at the femoral head, and the foot was supported against a plate to simulate static double-leg stance. A pressure mapping sensor was inserted into the ankle joint. A percutaneous triple hemiresection tendo-Achilles lengthening procedure (Hoke procedure) was performed on each specimen to simulate tendon lengthening after conservative treatment. Contact pressure, peak pressure, and center-of-pressure were measured for native and tendon-lengthened conditions.
Tendon rupture did not significantly alter average contact pressure, peak contact pressures, or center-of-pressure in the ankle joint compared with native tendon.
Achilles lengthening does not significantly change contact pressures of the ankle joint in this model . This result suggests that the passive restraint on ankle joint translation imposed by the Achilles tendon is minimal without muscle activation.
Cancer is a global epidemic; over 1.5 million new cancer diagnoses and greater than 600,000 deaths due to cancer are estimated to occur in the United States within the year 2015 alone. Approximately ...two-thirds of patients with bone metastases will experience pain, pathological fractures, spinal cord or nerve root compression, paralysis, impaired mobility, bone marrow infiltration and hypercalcemia of malignancy. We induced bone metastases through inoculation of rat femurs with MDA-MB-231 human breast cancer cells in order to compare the effectiveness of various treatment modalities, disease progression and recovery through the use of imaging methods in current clinical practice. CTRA provides highly accurate monitoring of metastases progression and treatment through both Ibandronate and Paclitaxel therapies. Using computed tomography (QCT)-based analysis to calculate the load bearing capacity of bone infiltrated with metastatic breast carcinoma, fracture risk threshold was predicted using Computed Topography Rigidity Analysis (CTRA) with 100% sensitivity and 90% specificity. The results of this study further validate that there is an existing gap between clinical guidelines and physician’s recommendations. This inconsistency necessitates that the decision making process for the selection of surgical or non-surgical treatment must be narrowed by more advanced prognostic tools such as CTRA.
In this paper, we present a review of some electromagnetic interactions in bone matter. Special attention is paid to pulsed electromagnetic therapy, which is potentially a promising therapeutic ...method for bone healing. We review and compare existing setups and their applications.
Cancer is a global epidemic; over 1.5 million new cancer diagnoses and greater than 600,000 deaths due to cancer are estimated to occur in the United States within the year 2015 alone. Approximately ...two-thirds of patients with bone metastases will experience pain, pathological fractures, spinal cord or nerve root compression, paralysis, impaired mobility, bone marrow infiltration and hypercalcemia of malignancy. We induced bone metastases through inoculation of rat femurs with MDA-MB-231 human breast cancer cells in order to compare the effectiveness of various treatment modalities, disease progression and recovery through the use of imaging methods in current clinical practice. CTRA provides highly accurate monitoring of metastases progression and treatment through both Ibandronate and Paclitaxel therapies. Using computed tomography (QCT)-based analysis to calculate the load bearing capacity of bone infiltrated with metastatic breast carcinoma, fracture risk threshold was predicted using Computed Topography Rigidity Analysis (CTRA) with 100% sensitivity and 90% specificity. The results of this study further validate that there is an existing gap between clinical guidelines and physician’s recommendations. This inconsistency necessitates that the decision making process for the selection of surgical or non-surgical treatment must be narrowed by more advanced prognostic tools such as CTRA.
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