Intramuscular Pressure Research Articles

Continuous Near-Infrared Spectroscopy Demonstrates Limitations in Monitoring the Development of Acute Compartment Syndrome in Patients with Leg Injuries.

We recorded measurements of muscle perfusion using near-infrared spectroscopy (NIRS) and intramuscular pressure (IMP) in a study designed to develop a decision rule for predicting acute compartment syndrome (ACS). The purpose of this study was to report our experience measuring NIRS data in the context of this broader investigation and to explore factors related to variations in data capture. One hundred and eighty-five patients with lower-leg injuries had data consisting of continuous NIRS measurement of the O2 saturation in the anterior compartment of the injured limb and the contralateral (control) limb, and continuous IMP recording in the anterior and deep posterior compartments of the injured leg as part of their participation in an institutional review board-approved multicenter trial. All monitoring was done for a prescribed period of time. For both types of data, the percentage of valid data capture was defined as the ratio of the minutes of observed data points within a physiological range to the total minutes of expected data points. Clinically useful NIRS data required simultaneous data from the injured and control limbs to calculate the ratio. Statistical tests were used to compare the 2 methods as well as factors associated with the percent of valid NIRS data capture. For the original cohort, clinically useful NIRS data were available a median of 9.1% of the expected time, while IMP data were captured a median of 87.6% of the expected time (p < 0.001). Excluding 46 patients who had erroneous NIRS data recorded, the median percentage was 31.6% for NIRS compared with 87.4% for IMP data (p < 0.00001). Fractures with an associated hematoma were less likely to have valid data points (odds ratio [OR], 0.53; p = 0.04). Gustilo types-I and II open fractures were more likely than Tscherne grades C0 and C1 closed fractures to have valid data points (OR, 1.97; p = 0.03). In this study, NIRS data were not collected reliably. In contrast, IMP measurements were collected during >85% of the expected monitoring period. These data raise questions about the utility of current NIRS data capture technology for monitoring oxygenation in patients at risk of ACS.

Compartment syndrome as a result of incorrect treatment

Compartment syndrome is a rare vascular disorder and an orthopedic emergency caused by high intramuscular pressure following bone fractures and some other etiologies. It mostly involves extremities, but can affect other parts of the body. The syndrome is diagnosed based on extensively varying signs and symptoms including feeling pain, pallor, pulselessness, and some other signs among patients. It causes irreversible complications that may even lead to death in some cases. If not treated promptly, muscle and nerve necrosis, myoglobinuria, and ultimately extremity gangrene and renal failure may occur. Timely diagnosis requires close attention to patient’s signs and symptoms and repeated measurements of pressure in the compartment. The reported case was an 11-year-old girl suffering from a closed double fracture in her forearm following blunt trauma. Inappropriate treatment done by a local therapist resulted in compartment syndrome. The aim of this study was to obtain an accurate knowledge on it and to do timely action when facing with this syndrome.

Release of Tibialis Posterior Muscle Osseofascial Sheath for Chronic Exertional Compartment Syndrome Leads to Improved Outcomes

Category: Sports Introduction/Purpose: Success rates for surgical management of chronic exertional compartment syndrome (CECS) in the lower extremity are influenced by the leg compartment involved. A failure rate of 40-50% has been associated with release of the deep posterior compartment, which has historically been associated with significantly worse outcomes than isolated anterolateral releases. The tibialis posterior muscle often resides in a separate osseofascial sheath, the so-called “fifth compartment.” At our institution, when a deep posterior release is performed, we routinely examine for this fifth compartment and release it if present. Within the context of this surgical approach, the aim of the current study was to compare long-term patient satisfaction and activity levels in those that underwent 2-versus 4-compartment fasciotomy for CECS. Methods: Our study reports on 48 limbs from 31 patients associated with a consecutive series that presented to a single institution for surgical management of lower extremity CECS from 2007-2016. The mean (standard deviation) follow-up was 65 (+/- 28) months. All patients underwent pre-operative intramuscular compartment pressure testing for CECS diagnosis. All surgeries were performed by a single surgeon. In all patients in which 4-compartment fasciotomy was indicated, the tibialis posterior muscle was examined for a separate osseofascial sheath. This sheath was released when present. The presence or absence of the sheath was always dictated in the operative note. Patient satisfaction outcomes were assessed with a Likert scale (excellent, good, fair, or poor). Current activity level was assessed via Marx and Tegner activity scores. Results: Of the 48 limbs, 29 limbs received 2-compartment anterolateral releases only and 19 limbs received 4-compartment fasciotomies. Of those that received 4-compartment fasciotomies, 13 (68%) were found to have a separate osseofascial sheath surrounding the tibialis posterior muscle. At a mean 5-year follow-up interval, 77% of the total cohort rated their outcome as good or excellent. Among the 4-comparment fasciotomy sub-cohort, 79% of patients rated their outcome as good or excellent. Among the entire cohort, there were no revision surgeries performed. The overall mean Tegner and Marx activity scores were 6 and 11 respectively. There was no significant difference in mean outcome scores between those that had 2-versus 4-compartment fasciotomies. Conclusion: Our study illustrates that 1) a separate osseofascial sheath exists around the tibialis posterior muscle in the majority of cases and 2) if this fifth compartment is consistently examined for and released, patients can achieve equivalent success rates and return to a similarly high activity level as those that undergo 2-compartment fasciotomy for CECS. Our study demonstrates superior results for 4-compartment release and includes the longest mean follow-up time for CECS patients in the literature.

Evaluating skeletal muscle electromechanical delay with intramuscular pressure

IntroductionIntramuscular pressure (IMP) is the fluid pressure generated within skeletal muscle and directly reflects individual muscle tension. The purpose of this study was to assess the development of force, IMP, and electromyography (EMG) in the tibialis anterior (TA) muscle during ramped isometric contractions and evaluate electromechanical delay (EMD). MethodsForce, EMG, and IMP were simultaneously measured during ramped isometric contractions in eight young, healthy human subjects. The EMD between the onset of force and EMG activity (Δt-EMG force) and the onset of IMP and EMG activity (Δt EMG-IMP) were calculated. ResultsA statistically significant difference (p < 0.05) was found between the mean force-EMG EMD (36 ± 31 ms) and the mean IMP-EMG EMD (3 ± 21 ms). ConclusionsIMP reflects changes in muscle tension due to the contractile muscle elements.

Modeling Skeletal Muscle Stress and Intramuscular Pressure: A Whole Muscle Active-Passive Approach.

Clinical treatments of skeletal muscle weakness are hindered by a lack of an approach to evaluate individual muscle force. Intramuscular pressure (IMP) has shown a correlation to muscle force in vivo, but patient to patient and muscle to muscle variability results in difficulty of utilizing IMP to estimate muscle force. The goal of this work was to develop a finite element model of whole skeletal muscle that can predict IMP under passive and active conditions to further investigate the mechanisms of IMP variability. A previously validated hypervisco-poroelastic constitutive approach was modified to incorporate muscle activation through an inhomogeneous geometry. Model parameters were optimized to fit model stress to experimental data, and the resulting model fluid pressurization data were utilized for validation. Model fitting was excellent (root-mean-square error or RMSE <1.5 kPa for passive and active conditions), and IMP predictive capability was strong for both passive (RMSE 3.5 mmHg) and active (RMSE 10 mmHg at in vivo lengths) conditions. Additionally, model fluid pressure was affected by length under isometric conditions, as increases in stretch yielded decreases in fluid pressurization following a contraction, resulting from counteracting Poisson effects. Model pressure also varied spatially, with the highest gradients located near aponeuroses. These findings may explain variability of in vivo IMP measurements in the clinic, and thus help reduce this variability in future studies. Further development of this model to include isotonic contractions and muscle weakness would greatly benefit this work.

Effects of anterior compartment fasciotomy on intramuscular compartment pressure in patients with chronic exertional compartment syndrome

BackgroundPatients with chronic exertional compartment syndrome (CECS) have pain during exercise that usually subsides at rest. Diagnosis is usually confirmed by measurement of intramuscular compartment pressure (IMCP) following exclusion of...

Barefoot plantar pressure measurement in Chronic Exertional Compartment Syndrome

BackgroundPatients with Chronic Exertional Compartment Syndrome (CECS) have exercise-limiting pain that subsides at rest. Diagnosis is confirmed by intramuscular compartment pressure (IMCP) measurement. Accompanying CECS, subjective changes to gait (foot slap) are frequently reported by patients. This has not previously been investigated. The aim of this study was to investigate differences in barefoot plantar pressure (BFPP) between CECS cases and asymptomatic controls prior to the onset of painful symptoms. Methods40 male military volunteers, 20 with symptoms of CECS and 20 asymptomatic controls were studied. Alternative diagnoses were excluded with rigorous inclusion criteria, magnetic resonance imaging and dynamic IMCP measurement. BFPP was measured during walking and marching. Data were analysed for: Stance Time (ST); foot progression angle (FPA); centre of force; plantarflexion rate after heel strike (IFFC-time); the distribution of pressure under the heel; and, the ratio between inner and outer metatarsal loading. Correlation coefficients of each variable with speed and leg length were calculated followed by ANCOVA or t-test. Receiver operating characteristic (ROC) curves were constructed for IFFC-time. ResultsCaseshad shorter ST and IFFC-times than controls. FPA was inversely related to walking speed (WS) in controls only. The area under the ROC curve for IFFC-time ranged from 0.746 (95%CI: 0.636–0.87) to 0.773 (95%CI: 0.671–0.875) representing ‘fair predictive validity’. ConclusionPatients with CECS have an increased speed of ankle plantarflexion after heel strike that precedes the onset of painful symptoms likely resulting from a mechanical disadvantage of Tibialis Anterior. These findings provide further insight into the pathophysiology of CECS and support further investigation of this non-invasive diagnostic. The predictive value of IFFC-time in the diagnosis of CECS is comparable to post-exercise IMCP but falls short of dynamic IMCP measured during painful symptoms.

Duty Cycle Impairs Functional Sympatholysis During Moderate Intensity Hand‐grip Exercise

Functional sympatholysis is a well‐known mechanism that blunts the sympathetic vasoconstrictor signal in working muscle, enabling blood flow to be maintained during exercise in the moderate intensity domain. Recent work has demonstrated that exercise intensity and contraction frequency effects functional sympatholysis via changes in metabolic rate. However, less is known about the effects duty cycle (DC) on functional sympatholysis, which alters the time that intramuscular pressure is developed throughout a contraction cycle independent of changes in frequency and intensity. Given that a higher duty cycle (i.e., 50% DC) attenuates muscle blood flow to the working limb, potentially leading to a greater metabolite buildup, we hypothesized that a 20% DC would show greater percent change in forearm vascular conductance (%Δ FVC) and forearm blood flow (%Δ FBF) when compared to 50% duty cycle.METHODSEight healthy male subjects (age: 25 ± 1 yrs; height: 176.8 ± 1.5 cm; weight: 84 ± 5 kg) agreed to participate in the current investigation. Subjects began with a four‐minute resting protocol, two‐minutes of supine blood pressure and blood flow and two‐minutes utilizing lower‐body negative pressure (LBNP; ‐30 mmHg) to increase sympathetic outflow. Subjects then underwent two exercise conditions in a randomized order consisting of 20% and 50% DC (20%:50% or 50%:20%) with ~10 min between trials to allow blood pressure and blood flow to return to baseline. All hand‐grip exercise was performed at 20 contractions per minute at a workload of 20% of subject's maximal voluntary contraction.RESULTSAbsolute FVC during the 20% duty cycle condition was significantly higher than the 50% duty cycle (20%: 398 ± 34; 50%: 327 ± 37 ml min−1 mmHg−1; P &lt; 0.01). FBF was also significantly higher in the 20% duty cycle condition (20%: 392 ± 21; 50%: 330 ± 29 ml min−1; P &lt; 0.01). During steady state hand‐grip exercise coupled with LBNP, %Δ FVC, an indicator of sympathetically‐mediated vasoconstriction, showed a larger percent reduction during 20% duty cycle (20%: −12.6 ± 1.5%; 50%: 1.4 ± 3.9%; P &lt; 0.01).CONCLUSIONThe results of the current investigation suggest that the 20% DC had a greater sympathetically‐mediated vasoconstrictor response compared to the 50% duty cycle.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Current Diagnosis and Management of Chronic Exertional Compartment Syndrome

The goal of this paper is to review the current evidence on diagnosis and management of chronic exertional compartment syndrome (CECS) of the lower leg. We sought to answer the question of whether recent research and innovations have demonstrated diagnostic alternatives or adjuncts to intramuscular compartment pressure testing and whether there are effective treatment options other than surgical fasciotomy. Research has shown promising outcomes with non-operative management including targeted alterations to running biomechanics. There is also research demonstrating efficacy in the use of botulinum injection as well as ultrasound-guided fascial fenestration and fasciotomy. Innovations in the diagnosis of CECS include the use of continuous compartment pressure monitoring during exercise as well as some early research on the use of musculoskeletal ultrasound and particular MRI protocols of the lower leg. Non-surgical management includes intervention to improve running biomechanics, botulinum toxin injection, and ultrasound-guided fasciotomy. Future research is needed on alternative diagnostic modalities including musculoskeletal ultrasound and exercise MRI protocols and on alternative management strategies including botulinum toxin injection and ultrasound-guided fascial fenestration or fasciotomy.

Effect of Cold-Water Immersion on Elbow Flexors Muscle Thickness After Resistance Training.

Matos, F, Neves, EB, Rosa, C, Reis, VM, Saavedra, F, Silva, S, Tavares, F, and Vilaça-Alves, J. Effect of cold-water immersion on elbow flexors muscle thickness after resistance training. J Strength Cond Res 32(3): 756-763, 2018-Cold-water immersion (CWI) is commonly applied to speed up the recovery process after exercise. Muscle damage may induce a performance reduction and consequence of the intramuscular pressure induced by the muscular swelling. The aim of the study was to verify the CWI effects on muscle thickness (MT) behavior of the elbow flexors after a strength training (ST) protocol. Eleven men were submitted to an ST, performed in 2 different weeks. In one of the weeks, subjects experienced a passive recovery. In the other, subjects were submitted to a CWI (20 minutes at 5-10° C). Ultrasound (US) images were taken before, after, as well as 24, 48, and 72 hours after exercise, to evaluate the MT. Muscle thickness in both exercise arm (EA) and control arm (CA) was significantly higher 48 and 72 hours after exercise when subjects were submitted to a passive recovery compared with the CWI (p = 0.029, p = 0.028, p = 0.009, and p = 0.001, 48 hours, 72 hours, EA, and CA, respectively). When each arm was analyzed with or without using CWI individually, significantly higher MT was observed in the EA with CWI: before exercise in relation to 72 hours after exercise (p = 0.042) and after exercise in relation to the other measurements (p = 0.003, p = 0.003, p = 0.038, and p < 0.0001, before exercise and 24, 48, 72 hours after exercise, respectively). The evaluation of MT by US provides evidence that CWI after ST (and 24 hours after exercise) may reduce muscle swelling in the postexercise days when compared with a passive recovery. Seems to be a paradox between the uses of CWI for an acute reduction of muscle swelling.

Intramuscular Pressure of Tibialis Anterior Reflects Ankle Torque but Does Not Follow Joint Angle-Torque Relationship

Intramuscular pressure (IMP) is the hydrostatic fluid pressure that is directly related to muscle force production. Electromechanical delay (EMD) provides a link between mechanical and electrophysiological quantities and IMP has potential to detect local electromechanical changes. The goal of this study was to assess the relationship of IMP with the mechanical and electrical characteristics of the tibialis anterior muscle (TA) activity at different ankle positions. We hypothesized that (1) the TA IMP and the surface EMG (sEMG) and fine-wire EMG (fwEMG) correlate to ankle joint torque, (2) the isometric force of TA increases at increased muscle lengths, which were imposed by a change in ankle angle and IMP follows the length-tension relationship characteristics, and (3) the electromechanical delay (EMD) is greater than the EMD of IMP during isometric contractions. Fourteen healthy adults [7 female; mean (SD) age = 26.9 (4.2) years old with 25.9 (5.5) kg/m2 body mass index] performed (i) three isometric dorsiflexion (DF) maximum voluntary contraction (MVC) and (ii) three isometric DF ramp contractions from 0 to 80% MVC at rate of 15% MVC/second at DF, Neutral, and plantarflexion (PF) positions. Ankle torque, IMP, TA fwEMG, and TA sEMG were measured simultaneously. The IMP, fwEMG, and sEMG were significantly correlated to the ankle torque during ramp contractions at each ankle position tested. This suggests that IMP captures in vivo mechanical properties of active muscles. The ankle torque changed significantly at different ankle positions however, the IMP did not reflect the change. This is explained with the opposing effects of higher compartmental pressure at DF in contrast to the increased force at PF position. Additionally, the onset of IMP activity is found to be significantly earlier than the onset of force which indicates that IMP can be designed to detect muscular changes in the course of neuromuscular diseases impairing electromechanical transmission.

Identifying prognostic factors for conservative treatment outcomes in servicemen with chronic exertional compartment syndrome treated at a rehabilitation center

BackgroundChronic exertional compartment syndrome (CECS) is a condition of pain induced by exercise, and it is characterized by muscle swelling and impaired muscle function in the lower leg. Given the diversity in the diagnosis and treatment of CECS, it is desirable to determine variables pertaining to prognosis and recovery. The purpose of this study is to identify prognostic factors for conservative treatment outcomes in servicemen with CECS who were treated at a Military Rehabilitation Center.MethodsPatients from all military services were referred from the special unit for lower leg pain at the Central Military Hospital, Utrecht, the Netherlands. Descriptive analysis was used to report the characteristics of the participants and their baseline measurements. Group differences were analyzed using a Student’s t-test or Mann-Whitney U test, according to the normality of the data distribution. Differences between the pre- and post-intervention outcomes were evaluated using the Wilcoxon signed rank test. To evaluate the magnitude of prognostic factors, a univariate logistic regression analysis was performed. The prognostic factors included age, body mass index, body fat percentage, self-efficacy beliefs, foot malalignment, intramuscular pressure, other comorbidities, protein and creatine use, smoking, alcohol use, complaint duration, physical demands, and duration of military service.ResultsAfter the rehabilitation period, we observed 25 patients with a successful outcome, which was defined as a reduction in pain (≥ 2 points) during the capacity test measured using a verbal rating scale and 20 patients with an unsuccessful outcome. Factors demonstrating a limited increased odds ratio for an unsuccessful outcome included smoking, alcohol use, intramuscular pressure, a complaint duration of more than 6 months, and physical demands of service. However, these factors did not reach significance.ConclusionThis study did not identify any prognostic factors that predict the outcome of a rehabilitation program for CECS. A larger sample using an identical design might provide further evidence regarding prognostic factors, which would facilitate development of a model that predicts the outcomes of a rehabilitation program for CECS.

Muscle Microvascular Blood Flow, Oxygenation, pH, and Perfusion Pressure Decrease in Simulated Acute Compartment Syndrome.

The current gold standard for diagnosing acute compartment syndrome (ACS) is an assessment of clinical signs, invasive measurement of intramuscular pressure (IMP), and measurement of local perfusion pressure. However, IMP measurements have several shortcomings, including pain, risk of infection, risk of technique error, plugging of the catheter tip, lack of consensus on the diagnostic pressure threshold, and lack of specificity and sensitivity. The objective of this study was to evaluate muscle hemodynamics, oxygenation, and pH as diagnostic parameters in a human model of ACS. We hypothesized that as IMP increases, muscle microvascular blood flow, oxygenation, and pH decrease in the anterior compartment of a leg at heart level and that they decrease significantly more when the leg is elevated further. An external pneumatic leg pressure chamber, combined with a venous stasis thigh cuff, was used to increase IMP and simulate ACS. Eight healthy subjects (5 males and 3 females; mean age, 26 years) had photoplethysmography and near-infrared spectroscopy-pH sensors placed over the middle aspect of the tibialis anterior muscle of the right (experimental) and left (control) legs. Leg chamber pressure conditions (40, 50, and 60 mm Hg) were applied in a randomized order after baseline measurements were taken. Data were collected continuously for each 11-minute pressure condition, with an 11-minute recovery period after each condition, and the average of the last 6 minutes was used for data analyses. The same protocol was repeated with each subject's legs elevated 12 cm above heart level. Data were analyzed using repeated-measures analysis of variance (ANOVA). As IMP increased, muscle microvascular blood flow (p = 0.01), oxygenation (p < 0.001), and pH (p < 0.001) all decreased significantly in the experimental leg compared with the control leg. At all IMP levels, leg elevation significantly decreased muscle oxygenation (p = 0.013) and perfusion pressure (p = 0.03) compared with the control leg at heart level. These results indicate that muscle microvascular blood flow, oxygenation, pH, and perfusion pressure decrease significantly as IMP increases in a human model of ACS. This study identifies hemodynamic and metabolic parameters as potential noninvasive diagnostic tools for ACS.

Evaluate muscle tension using intramuscular pressure device in rabbit tibialis anterior model for improved tendon transfer surgery

Quantitative evaluation of passive tension in a muscle is important in tendon transfer surgeries, however, currently appropriate intraoperative measurement techniques are lacking. Objective: Intramuscular pressure (IMP) is explored as an application to access force. Approach: The tibialis anterior (TA) in New Zealand white rabbits (n = 9) was used to test the hypothesis of a strong correlation between the IMP, muscle force, and length. This study also helped to develop intraoperative techniques for future human studies evaluating various insertion techniques (parallel versus perpendicular). Main results: The Pearson correlation between IMP and force for all trials was 0.74 ± 0.30. Separating out the parallel insertion from the perpendicular insertion revealed a significantly higher correlation for parallel, 0.91 ± 0.13 versus 0.56 ± 0.32. Significance: These data indicate IMP sensors can be used to assess force in a single muscle and the parallel insertion method should be used.New findings• What is the central question of this study?Successful outcomes of tendon and muscle transfers depend on proper muscle tension. A near linear relationship has been seen between muscle force and intramuscular pressure. This study aims to develop an intraoperative technique for assessing passive muscle tension using intramuscular pressure.• What is the main finding and its importance?The findings from this study reveal a high correlation between pressure and passive tension in a single muscle. The techniques developed in this study will allow the translation to a human model. The work will help to improve surgical outcomes and aim to retain muscle strength in the patient following procedures such as tendon and muscle transfers.

Muscle changes in patients with diabetes and chronic exertional compartment syndrome before and after treatment with fasciotomy.

Muscle changes in patients with diabetes and lower leg pain due to chronic exertional compartment syndrome (CECS) were investigated before and after fasciotomy. The tibialis anterior muscle was analyzed with histochemical and morphological techniques in 7 patients with diabetes and CECS before fasciotomy and in 5 of them 1 year after fasciotomy. Nondiabetic patients with CECS and healthy participants served as references. Before treatment, walking distance until occurrence of pain was limited (<0.2 km). Intramuscular pressure was significantly higher than in reference participants. Muscle analysis showed changes pathognomonic for neuropathy and myopathy and a restricted capillary network, with significantly more severe changes in the muscles of patients with diabetes than in the muscles of nondiabetic patients. Treatment with fasciotomy improved clinical signs, increased walking ability, and reduced muscle abnormalities, but muscle capillarization remained low. Patients with diabetes and CECS have distinct pathological changes in affected muscles. Pressure-relieving fasciotomy triggers a regenerative response in the muscle tissue but not in the capillary bed. Muscle Nerve 57: 229-239, 2018.

Acute compartment syndrome

Acute compartment syndrome is a well-known complication of tibial fractures, yet it remains difficult to diagnose and the only effective treatment is surgical fasciotomy. Delayed fasciotomy is the most important factor contributing to poor outcomes, and as a result, treatment is biased towards performing early fasciotomy. Current diagnosis of ACS is based on clinical findings and intramuscular pressure (IMP) measurement, and is targeted at identifying safe thresholds for when fasciotomy can be avoided. Since clinical findings are variable and difficult to quantify, measurement of IMP – ideally continuously – is the cornerstone of surgical decision – making. Numerous investigators are searching for less invasive and more direct measurements of tissue ischemia, including measurement of oxygenation, biomarkers, and even neurologic monitoring. This article provides a brief but thorough review of the current state of the art in compartment syndrome diagnosis and treatment.

Predicting Acute Compartment Syndrome (PACS): The Role of Continuous Monitoring.

The diagnosis of acute compartment syndrome (ACS) is a common clinical challenge among patients who sustain high-energy orthopaedic trauma, largely because no validated criteria exist to reliably define the presence of the condition. In the absence of validated diagnostic standards, concern for the potential clinical and medicolegal impact of a missed compartment syndrome may result in the potential overuse of fasciotomy in "at-risk" patients. The goal of the Predicting Acute Compartment Syndrome Study was to develop a decision rule for predicting the likelihood of ACS that would reduce unnecessary fasciotomies while guarding against potentially missed ACS. Of particular interest was the utility of early and continuous monitoring of intramuscular pressure and muscle oxygenation using near-infrared spectroscopy in the timely diagnosis of ACS. In this observational study, 191 participants aged 18-60 with high-energy tibia fractures were prospectively enrolled and monitored for up to 72 hours after admission, then followed for 6 months. Treating physicians were blinded to continuous pressure and oxygenation data. An expert panel of 9 orthopaedic surgeons retrospectively assessed the likelihood that each patient developed ACS based on data collected on initial presentation, clinical course, and known functional outcome at 6 months. This retrospectively assigned likelihood is modeled as a function of clinical data typically available within 72 hours of admission together with continuous pressure and oxygenation data. This study will improve our understanding of the natural history of compartment syndrome and examine the utility of early and continuous monitoring of the physiologic status of the injured extremity in the timely diagnosis of ACS.

Three-year postoperative outcomes between MIS and conventional TLIF in1-segment lumbar disc herniation

Aim: The aim of this study is to assess the long-term clinical and radiological outcomes between minimally invasive (MIS) and conventional transforaminal lumbar interbody fusion (TLIF) in treating one-segment lumbar disc herniation (LDH).Material and methods: One-hundred and six patients treated by MIS-TLIF (50 cases) or conventional TLIF (56 cases) were included. Perioperative results were evaluated. Clinical outcomes were compared preoperatively and postoperatively. Radiologic parameters were based on a comparison of preoperative and three-year postoperative lumbar lordosis, segmental lordosis, sacral slope, the cross-sectional area of the paraspinal muscle and fusion rates.Results: MIS TILF had significantly less blood, shorter operation time, mean return to work time and lower intramuscular pressure compared with the conventional group during the operation. VAS scores for lower back pain and ODI in MIS-TLIF were significantly decreased. The mean cross-sectional area of the paraspinal muscle was significantly decreased after surgery in the conventional TLIF group and no significant intragroup differences were established in the MIS-TLIF group. No significant differences were found in fusion rate, lumbar lordosis, segmental lordosis and sacral slope.Conclusions: Both MIS and conventional TLIF were beneficial for patients with LDH. However, MIS-TLIF manifests a great improvement in perioperative outcomes, low back pain, disability and preventing paraspinal muscle atrophy during the follow-up period observation.

Dorsiflexor Muscle Oxygenation During Low, Moderate and Submaximal Sustained Isometric Contraction.

Sustained isometric contractions of skeletal muscles produce intramuscular pressures that lead to blood flow restriction. Thus, we have the paradox of rising O2 demand due to muscle activity and at the same time reduced blood flow. The aim was to assess muscle oxygenation during sustained isometric low (30%), moderate (60%) and submaximal [90% of maximal voluntary contraction (MVC)] contraction of the dorsiflexor muscle. Experiments were conducted on the dominant (right) leg of 8 male students (age 19 ± 2 years, weight 75 ± 6 kg). Tissue oxygen saturation (StO2) was recorded from the tibialis anterior using near-infrared spectroscopy. StO2 was higher at 30% compared to both 60% and 90% MVC at all time points after the start of the exercise and higher at 60% than 90%. This indicates that the supply of O2 did not keep up with its consumption. During arterial occlusion the minimal StO2 reached 52%, which is significantly higher than StO2 during 60% and 90% MVC. After each contraction there was a large and immediate hyperemic response, whose resaturation rate continuously increased from 30% to 60% to 90% MVC. The StO2 resaturation rate was positively correlated with the MVC, indicating a vasodilation depending on the intensity of the exercise.

A validated model of passive skeletal muscle to predict force and intramuscular pressure

The passive properties of skeletal muscle are often overlooked in muscle studies, yet they play a key role in tissue function in vivo. Studies analyzing and modeling muscle passive properties, while not uncommon, have never investigated the role of fluid content within the tissue. Additionally, intramuscular pressure (IMP) has been shown to correlate with muscle force in vivo and could be used to predict muscle force in the clinic. In this study, a novel model of skeletal muscle was developed and validated to predict both muscle stress and IMP under passive conditions for the New Zealand White Rabbit tibialis anterior. This model is the first to include fluid content within the tissue and uses whole muscle geometry. A nonlinear optimization scheme was highly effective at fitting model stress output to experimental stress data (normalized mean square error or NMSE fit value of 0.993) and validation showed very good agreement to experimental data (NMSE fit values of 0.955 and 0.860 for IMP and stress, respectively). While future work to include muscle activation would broaden the physiological application of this model, the passive implementation could be used to guide surgeries where passive muscle is stretched.