Intramuscular pressure of human tibialis anterior muscle detects age-related changes in muscle performance.

Intramuscular pressure (IMP) reflects forces produced by a muscle. Age is one of the determinants of skeletal muscle performance. The present study aimed to test whether IMP mirrors known age-related muscular changes. We simultaneously measured the tibialis anterior (TA) IMP, compound muscle action potential (CMAP), and ankle torque in thirteen older adults (60-80 years old) in vivo by applying different stimulation intensities and frequencies. We found significant positive correlations between the stimulation intensity and IMP and CMAP. Increasing stimulation frequency caused ankle torque and IMP to increase. The electromechanical delay (EMD) (36 ms) was longer than the onset of IMP (IMPD) (29 ms). Compared to the previously published data collected from young adults (21-40 years old) in identical conditions, the TA CMAP and IMP of older adults at maximum intensity of stimulation were 23.8% and 39.6% lower, respectively. For different stimulation frequencies, CMAP, IMP, as well as ankle torque of older adults were 20.5%, 24.2%, and 13.2% lower, respectively. Surprisingly, the EMD did not exhibit any difference between young and older adults and the IMPD was consistent with the EMD. Data supporting the hypotheses suggest that IMP measurement is an indicator of muscle performance in older adults.

Method for characterization of dynamic ankle stiffness in patients with spasticity.

BACKGROUND: Dynamic ankle stiffness has been quantified as the slope of the ankle joint moment-angle curve over the gait interval of the second rocker, defined explicitly as the period of the gait cycle from the first relative maximum plantar flexion in early stance to maximum dorsiflexion in midstance. However, gastrocnemius spasticity may interfere with the second ankle rocker in patients with spasticity. This gait disruption results in stiffness calculations which are misleading. Current dynamic stiffness metrics need to be modified. RESEARCH QUESTION: The main goal of this study was to develop and test a new method to better evaluate dynamic ankle stiffness in individuals with pathologic gait who lack a second rocker interval. METHODS: Twenty unimpaired ambulators (10/20 female, 26.7 ± 5.0 years, BMI: 23.2 ± 2.2) and 9 individuals with cerebral palsy (5/9 female, 5.7 ± 1.7 years, BMI: 14.6 ± 2.1, GMFCS Levels: I - 2, II - 5, III - 2) participated in this study. Dynamic ankle stiffness was evaluated using the previous kinematic method, defined by the interval of maximum plantar flexion to maximum dorsiflexion angle in midstance, and the proposed kinetic method, defined by the interval from the maximum dorsiflexion moment to first peak plantar flexion moment. Stiffness was quantified as the linear slope between the sagittal plane ankle angle and moment. Method differences were explored using an equivalence test (α = 0.05). RESULTS AND SIGNIFICANCE: There was equivalence between the methods for unimpaired ambulators (p = 0.000) and a lack of equivalence for patients with spasticity (p = 0.958). The new method was successfully applied to all 9 pediatric ambulators with CP and demonstrated increased stiffness in patients with spasticity as compared to the previous method. The ability to objectively calculate ankle stiffness in pathologic gait is critical for determining change associated with clinical intervention.

Intramuscular Pressure of Human Tibialis Anterior Muscle Reflects in vivo Muscular Activity.

Intramuscular pressure (IMP) is the fluid hydrostatic pressure generated within a muscle and reflects the mechanical forces produced by a muscle. By providing accurate quantification of interstitial fluid pressure, the measurement of IMP may be useful to detect changes in skeletal muscle function not identified with established techniques. However, the relationship between IMP and muscle activity has never been studied in vivo in healthy human muscles. To determine if IMP is able to evaluate electromechanical performance of muscles in vivo, we tested the following hypotheses on the human tibialis anterior (TA) muscle: (i) IMP increases in proportion to muscle activity as measured by electrical [Compound Muscle Action Potential (CMAP)] and mechanical (ankle torque) responses to activation by nerve stimulation and (ii) the onset delay of IMP (IMPD) is shorter than the ankle torque electromechanical delay (EMD). Twelve healthy adults [six females; mean (SD) = 28.1 (5.0) years old] were recruited. Ankle torque, TA IMP, and CMAP responses were collected during maximal stimulation of the fibular nerve at different intensity levels of electrical stimulation, and at different frequencies of supramaximal stimulation, i.e., at 2, 5, 10, and 20 Hz. The IMP response at different stimulation intensities was correlated with the CMAP amplitude (r 2 = 0.94). The area of the IMP response at different stimulation intensities was also significantly correlated with the area of the CMAP (r 2 = 0.93). Increasing stimulation intensity resulted in an increase of the IMP response (P < 0.001). Increasing stimulation frequency caused torque (P < 0.001) as well as the IMP (P < 0.001) to increase. The ankle torque EMD [median (interquartile range) = 41.8 (14.4) ms] was later than the IMPD [33.0 (23.6) ms]. These findings support the hypotheses and suggest that IMP captures active mechanical properties of muscle in vivo and can be used to detect muscular changes due to drugs, diseases, or aging.

Posterior Vertebral Endplate Fractures: A Retrospective Study on a Rare Etiology of Back Pain in Youth and Young Adults.

BACKGROUND: Posterior lumbar vertebral endplate fracture occurs with avulsion of the ring apophysis from the posterior vertebral body. Although this has been described in adolescents and young adults, proper diagnosis is often delayed or missed entirely. Surgery may be curative. OBJECTIVE: To determine the common clinical features and treatment outcomes in youth and young adults with posterior lumbar vertebral endplate fractures. DESIGN: Retrospective case series. SETTING: Academic medical institution. PATIENTS: Patients 10 to 25 years old from 2000 through 2012 with posterior vertebral endplate fracture diagnosis. MAIN OUTCOME MEASUREMENTS: Demographic characteristics, diagnostic studies, interventions, and change in symptoms postoperatively. RESULTS: A total of 16 patients had posterior vertebral endplate fractures (8 male patients; mean age, 15.2 years)-8.3% of 192 patients with inclusion age range undergoing spinal surgery for causes unrelated to trauma, scoliosis, or malignancy. The most common signs and symptoms were low back and radiating leg pain, positive straight leg raise, hamstring contracture, and abnormal gait. Cause was sports related for 12 patients (75%). Mean (range) time to diagnosis was 13.0 (3.0-63.0) months. Diagnosis was most commonly made with lumbar magnetic resonance imaging (n = 6). Most fractures occurred at L5 (n = 8, 50%) and L4 (n = 5, 31.3%). Conservative measures were trialed before surgery. Nine patients had "complete relief" following surgery and seven "improved." CONCLUSIONS: Posterior vertebral endplate fracture should be considered in differential diagnosis of a youth or young adult with back pain, radiating leg pain, and limited knee extension, regardless of symptom onset. For patients in whom conservative management fails, consultation with an experienced physician whose practice specializes in spine medicine is recommended. LEVEL OF EVIDENCE: IV.

Evidence-based intraoperative microbreak activities for reducing musculoskeletal injuries in the operating room.

BACKGROUND: Neuromusculoskeletal pain and fatigue have been self-reported by over 70% surgeons who perform minimally invasive surgery (MIS). These problems can become impairments impacting surgical performance, patient outcomes, and career longevity. Human factors engineering has identified microbreaks coupled with activities as a viable strategy to counteract known physical, cognitive, and environmental stressors as well as mitigate neuromusculoskeletal (NMS) problems for workers in office and manufacturing domains. OBJECTIVE: Develop a novel set of intraoperative surgical microbreaks activities tailored for MIS surgeons to mitigate surgery-induced neuromusculoskeletal fatigue and pain. METHODS: Using NSM problems identified by practitioners and literature, a clinician determined causes and solutions and ranked them based on literature and clinical expertise. Solutions were incorporated into synchronized activities that addressed overarching goals and multiple tissues. RESULTS: The resulting activities, translating contemporary science in clinical physical medicine and rehabilitation practice and tissue biomechanics, specifically address the overarching goals of: 1) posture correction; 2) normalization of tissue tension and soft tissue mobility/gliding; and 3) relaxation/stress reduction. CONCLUSION: Surgeons can perform the activities in approximately one minute inside the sterile field. Movements encompassing multiple requirements and engaging multiple body segments are combined to provide an efficient and effective intervention to the target tissues.

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.

Foot and Ankle Kinematics and Dynamic Electromyography: Quantitative Analysis of Recovery From Peroneal Neuropathy in a Professional Football Player.

The assessment of neuromuscular recovery after peripheral nerve surgery has typically been a subjective physical examination. The purpose of this report was to assess the value of gait analysis in documenting recovery quantitatively. A professional football player underwent gait analysis before and after surgery for a peroneal intraneural ganglion cyst causing a left-sided foot drop. Surface electromyography (SEMG) recording from surface electrodes and motion parameter acquisition from a computerized motion capture system consisting of 10 infrared cameras were performed simultaneously. A comparison between SEMG recordings before and after surgery showed a progression from disorganized activation in the left tibialis anterior and peroneus longus muscles to temporally appropriate activation for the phase of the gait cycle. Kinematic analysis of ankle motion planes showed resolution from a complete foot drop preoperatively to phase-appropriate dorsiflexion postoperatively. Gait analysis with dynamic SEMG and motion capture complements physical examination when assessing postoperative recovery in athletes.

Frequency analysis of lower extremity electromyography signals for the quantitative diagnosis of dystonia.

The purpose of this study was to develop an objective, quantitative tool for the diagnosis of lower extremity dystonia. Frequency domain analysis was performed on surface and fine-wire electromyography (EMG) signals collected from the lower extremity musculature of ten patients with suspected dystonia while performing walking trials at self-selected speeds. The median power frequency (MdPF) and percentage of total power contained in the low frequency range (%AUCTotal) were determined for each muscle studied. Muscles exhibiting clinical signs of dystonia were found to have a shift of the MdPF to lower frequencies and a simultaneous increase in the %AUCTotal. A threshold frequency of 70Hz identified dystonic muscles with 73% sensitivity and 63% specificity. These results indicate that frequency analysis can accurately distinguish dystonic from non-dystonic muscles.

The John Insall award: no benefit of minimally invasive TKA on gait and strength outcomes: a randomized controlled trial.

BACKGROUND: While some clinical reports suggest minimally invasive surgical (MIS) techniques improve recovery and reduce pain in the first months after TKA, it is unclear whether it improves gait and thigh muscle strength. QUESTIONS/PURPOSES: We hypothesized TKA performed through a mini-subvastus approach would improve subjective and objective and subjective function compared to a standard medial parapatellar approach 2 months after surgery. METHODS: We randomized 40 patients into two groups using either the mini-subvastus approach or standard medial parapatellar approach. Patients were evaluated preoperatively and 2 months after surgery. We assessed subjective functional outcome and quality of life (QOL) using routine questionnaires (SF-12, Knee Society Score [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], UCLA activity, patient milestone diary of activities). We determined isometric strength of the thigh muscles and assessed gait with a three-dimensional (3-D) analysis during level walking and stair climbing. RESULTS: We observed improvements from preoperatively to 2 months postoperatively in functional scores, QOL, and knee kinematic and kinetic gait parameters during level and stair walking. Isometric quadriceps strength increased in both groups, although remaining lower when compared to sound limbs. We found no differences between the groups in KSS, SF-12, KOOS, UCLA activity, patient milestone diary of activities, isometric quadriceps strength, or 3-D gait parameters, except a marginally higher speed of stair ascent in the MIS group. CONCLUSIONS: Our observations suggest an MIS approach does not confer a substantial advantage in early function after TKA. LEVEL OF EVIDENCE: Level I, therapeutic study. See Instructions to Authors for a complete description of levels of evidence.

Forefoot plantar pressure reduction of off-the-shelf rocker bottom provisional footwear.

BACKGROUND: Increased plantar pressures have been shown to be a risk factor in ulceration of the neuropathic foot. Prescriptive footwear is a common medical treatment, yet evidence regarding the efficacy of these prescriptions is underdeveloped. The purpose of this study is to determine the off-loading properties of four provisional shoes; a rocker sole compared to a flat sole shoe with and without the addition of a 1.25 cm plastizote insert. METHODS: Fifteen subjects with peripheral neuropathy and a normal longitudinal arch were recruited to compare four types of provisional (post-operative) footwear. Plantar surface foot pressures were measured while wearing a rocker sole shoe or a flat stiff sole shoe. Both shoes were worn with and without a 1.25 cm plastizote insert. Peak plantar pressures were recorded for the hallux, metatarsal heads (1-5), midfoot, and heel. FINDINGS: The rocker sole shoe with plastizote had the best off-loading properties. While wearing this footwear, mean peak plantar pressure was 2.8 kg/cm(2) (range: 1.7 to 4.5 kg/cm(2), 50% mean reduction from flat sole shoe without plastizote) and 1.9 kg/cm(2) (range: 0.7 to 3.6 kg/cm(2), 35% mean reduction) at the five metatarsal heads and hallux, respectively. INTERPRETATION: For patients with a normal longitudinal arch and forefeet, either at risk of developing an ulcer or are healing a forefoot ulcer, a provisional shoe with a rocker sole and plastizote insole provides plantar pressure reduction of the forefoot. However, when results were analyzed for the subjects individually the amount of off-loading varied.

No strength or gait benefit of two-incision THA: a brief followup at 1 year.

BACKGROUND: Using comprehensive gait analysis and strength testing, we previously investigated the early (2-month) functional outcome after THA using two-incision and mini-posterior surgical approaches and found an advantage for the mini-posterior approach. Benefits included improved muscle strength, a less antalgic gait, and better hip function as reflected by changes in hip moments during level walking and stair climbing. We questioned how these differences in function would fare with longer followup. QUESTIONS/PURPOSES: We determined whether the observed early functional advantages for the mini-posterior technique over the two-incision technique were still present 1 year postoperatively. PATIENTS AND METHODS: We prospectively enrolled 22 patients with primary degenerative arthritis of the hip; of these, 21 completed gait and strength testing at 2 months, and 19 completed comprehensive gait and strength testing at 1 year (11 two-incision hips, eight mini-posterior hips). The 19 patients included 11 men and eight women with a mean age of 65 years (range, 40-85 years) and a mean (BMI) of 29 (range, 21-39). RESULTS: At 1 year postoperatively, the patients who had the mini-posterior THA had greater improvement in hip flexion strength and internal rotation strength, greater increase in hip flexor internal moment, and greater increase in single-leg stance time on level ground over the patients who had the two-incision THA. CONCLUSIONS: Compared with the two-incision approach, patients undergoing mini-posterior THA had persistently better function, including hip flexor and internal rotator muscle strength, hip flexor internal moment, and single-leg stance during level walking. LEVEL OF EVIDENCE: Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The 2008 Frank Stinchfield award: variation in postoperative pelvic tilt may confound the accuracy of hip navigation systems.

Most computer navigation systems used in total hip arthroplasty integrate preoperative pelvic tilt to calculate the anterior pelvic plane assuming tilt is constant; however, the consistency of pelvic tilt after THA has never been proven. Therefore, using a modern comprehensive gait analysis before and after arthroplasty we sought to compare (1) dynamic pelvic tilt changes and (2) pelvic flexion/extension range-of-motion changes. Twenty-one patients who underwent unilateral THA were prospectively studied. Quantitative pelvic tilt changes (in the sagittal plane) and pelvic range of flexion/extension motion relative to a laboratory coordinate system were compared using a computerized video motion system. Mean gait pelvic tilt was 13.9 masculine +/- 4.8 masculine (range, 1.73 masculine-23.1 masculine) preoperatively, 12.5 masculine +/- 4.5 masculine (range, 1.4 masculine-18.7 masculine) 2 months postoperatively, and 10.5 degrees +/- 5.5 masculine (range, -2.36 masculine-19.2 masculine) 12 months postoperatively. A significant proportion (31%) of patients had more than a 5 degrees difference between preoperative and 12-month postoperative measurements and the variability was spread over 20 degrees . Significant dynamic changes in pelvic tilt occurred after THA. While navigation clearly improves the anatomical position of the component during THA, the functional position of the component will not always be improved because of the significant change between preoperative and postoperative pelvic tilt.

Measuring outcomes in adult brachial plexus reconstruction.

The focus of this article is on evaluating the various outcome measures of surgical interventions for adult brachial plexus injuries. From a surgeon's perspective, the goals of surgery have largely focused on the return of motor function and restoration of protective sensation. From a patient's perspective, alleviation of pain, cosmesis, return to work, and emotional state are also important. The ideal outcome measure should be valid, reliable, responsive, unbiased, appropriate, and easy. The author outlines pitfalls and benefits of current outcome measures and offers thoughts on possible future measures.