Finite element graft stress for anteromedial portal, transtibial, and hybrid transtibial femoral drillings under anterior translation and medial rotation: an exploratory study.

Stress concentration on the Anterior Cruciate Ligament Reconstruction (ACLr) for femoral drillings is crucial to understanding failures. Therefore, we described the graft stress for transtibial (TT), the anteromedial portal (AM), and hybrid transtibial (HTT) techniques during the anterior tibial translation and medial knee rotation in a finite element model. A healthy participant with a non-medical record of Anterior Cruciate Ligament rupture with regular sports practice underwent finite element analysis. We modeled TT, HTT, AM drillings, and the ACLr as hyperelastic isotropic material. The maximum Von Mises principal stresses and distributions were obtained from anterior tibial translation and medial rotation. During the anterior tibia translation, the HTT, TT, and AM drilling were 31.5 MPa, 34.6 Mpa, and 35.0 MPa, respectively. During the medial knee rotation, the AM, TT, and HTT drilling were 17.3 MPa, 20.3 Mpa, and 21.6 MPa, respectively. The stress was concentrated at the lateral aspect of ACLr,near the femoral tunnel for all techniques independent of the knee movement. Meanwhile, the AM tunnel concentrates the stress at the medial aspect of the ACLr body under medial rotation. The HTT better constrains the anterior tibia translation than AM and TT drillings, while AM does for medial knee rotation.

Unique case study: Impact of single-session neuromuscular biofeedback on motor unit properties following 12 days of Achilles tendon surgical repair.

We explored the first evidence of a single-session neuromuscular biofeedback effect on motor unit properties, neuromuscular activation, and the Achilles tendon (AT) length 12 days after undergoing AT surgical repair. We hypothesized that immediate neuromuscular biofeedback enhances motor unit properties and activation without causing AT lengthening. After 12 days AT surgical repair, Medial Gastrocnemius (MG) motor unit decomposition was performed on a 58-year-old male before and after a neuromuscular biofeedback intervention (surface electromyography (sEMG) and ultrasonography), involving unressited plantar flexion. The analysis included motor unit population properties, sEMG amplitude, force paradigm, and AT length. There were increased MG motor unit recruitment, peak and average firing rate, coefficient of variation, and sEMG amplitude, and decreased recruitment and derecruitment threshold in the repaired AT limb. The non-injured limb increased the motor unit recruitment, and decreased the coefficient of variation, peak and average firing rate, inter-pulse interval, derecruitment threshold and sEMG amplitude. The AT length experienced -0.4 and 0.3 cm changes in the repaired AT and non-injured limb, respectively. This single-session neuromuscular biofeedback 12 days after AT surgery shows evidence of enhanced motor unit properties and activation without signs of AT lengthening when unresisted plantar flexion is performed in the repaired AT limb.

Role of Lateral Ankle Ligaments in Vertical Stability of the Fibula: A Cadaveric Model.

BACKGROUND: In unstable ankle fractures, the role of the deltoid and syndesmosis ligaments has been widely studied. However, it is uncertain what the importance of the lateral ankle ligament complex (LALC) is in the vertical stability of the fibula. Given its anatomical position, it should prevent the proximal translation of the fibula. This study aims to evaluate the role of the LALC in stabilizing the fibula in the vertical plane. METHODS: Eleven below-knee cadaveric specimens were used in this study. Proximal traction of the fibula was performed by applying 50 N in the intact state and after sequential transection of the syndesmotic ligaments, anterior talofibular ligament (ATFL), and the calcaneofibular ligament (CFL). At each stage, the proximal displacement of the fibula was measured. One-way repeated measures analysis of variance with post hoc Bonferroni correction was carried out to determine any significant differences between the groups. A P value <.05 was considered statistically significant. RESULTS: The vertical displacement of the fibula in the intact state, and after sequential transection of syndesmotic ligaments, ATFL, and CFL was 1.96 ± 1.19 mm, 3.96 ± 1.33 mm, 5.9 ± 1.73 mm, and 10.22 ± 2.76 mm, respectively. There was no significant difference in the proximal displacement of the fibula between the intact and the syndesmotic ligaments groups (P < .05). However, when the syndesmotic ligaments were transected in conjunction with ATFL ± CFL, a significant difference was observed compared to the intact state (P < .001). CONCLUSION: The complete disruption of syndesmotic ligaments did not significantly increase the proximal displacement of the fibula. However, when the ATFL ± CFL were additionally disrupted, there was a significant increase in the vertical translation of the fibula. CLINICAL RELEVANCE: To our knowledge, this is the first study describing that LALC plays a paramount role in the vertical stability of the fibula. Concomitant syndesmosis and LALC should be suspected in an axially unstable fibular fracture with a significant proximal displacement.

Multiclass Support Vector Machine improves the Pivot-shift grading from Gerdy's acceleration resultant prior to the acute Anterior Cruciate Ligament surgery.

INTRODUCTION: Rotatory laxity acceleration still lacks objective classification due to interval grading superposition, resulting in a biased pivot shift grading prior to the Anterior Cruciate Ligament (ACL) reconstruction. However, data analysis might help improve data grading in the operative room. Therefore, we described the improvement of the pivot-shift categorization in Gerdy's acceleration under anesthesia prior to ACL surgery using a support vector machine (SVM) classification, surgeon, and literature reference. METHODS: Seventy-five patients (aged 30.3 ± 10.2 years, and IKDC 52.0 ± 16.5 points) with acute ACL rupture under anesthesia prior to ACL surgery were analyzed. Patients were graded with pivot-shift sign glide (+), clunk (++), and (+++) gross by senior orthopedic surgeons. At the same time, the tri-axial tibial plateau acceleration was measured. Categorical data were statistically described, and the accelerometry and categorical data were associated (α = 5%). A multiclass SVM kernel with the best accuracy trained by orthopedic surgeons and assisted from literature for missing data was compared with experienced surgeons and literature interval grading. The cubic SVM classifier achieved the best grading. RESULTS: The intra-group proportions were different for each grading in the three compared strategies (p < 0.001). The inter-group proportions were different for all comparisons (p < 0.001). There were significant (p < 0.001) associations (Tau: 0.69, -0.28, and -0.50) between the surgeon and SVM, the surgeon and interval grading, and the interval and SVM, respectively. CONCLUSION: The multiclass SVM classifier improves the acceleration categorization of the (+), (++), and (+++) pivot shift sign prior to the ACL surgery in agreement with surgeon criteria.

Preseason multiple biomechanics testing and dimension reduction for injury risk surveillance in elite female soccer athletes: short-communication.

BACKGROUND: Injury risk is regularly assessed during the preseason in susceptible populations like female soccer players. However, multiple outcomes (high-dimensional dataset) derived from multiple testing may make pattern recognition difficult. Thus, dimension reduction and clustering may be useful for improving injury surveillance when results of multiple assessment tools are available. AIM: To determine the influence of dimension reduction for pattern recognition followed by clustering on multiple biomechanical injury markers in elite female soccer players during preseason. METHDOLOGY: We introduced the use of dimension reduction through linear principal component analysis (PCA), non-linear kernel principal component analysis (k-PCA), t-distributed stochastic neighbor embedding (t-sne), and uniform manifold approximation and projection (umap) for injury markers via grid search. Muscle strength, muscle function, jump technique and power, balance, muscle stiffness, exercise tolerance, and running performance were assessed in an elite female soccer team (n = 21) prior to the competitive season. RESULTS: As a result, umap facilitated the injury pattern recognition compared to PCA, k-PCA, and t-sne. One of the three patterns was related to a team subgroup with acceptable muscle conditions. In contrast, the other two patterns showed higher injury risk profiles. For our dataset, umap improved injury surveillance through multiple testing characteristics. CONCLUSION: Dimension reduction and clustering techniques present as useful strategies to analyze subgroups of female soccer players who have different risk profiles for injury.

Is the Rotatory Knee Stability Immediately Decreased Following a Competitive Soccer Match?

Fatigue induced by soccer playing increases physical efforts, which might alter the transverse knee stability, a known factor that promotes knee injuries, particularly anterior cruciate ligament injury. Thereby, primarily, we aimed to determine whether rotatory knee stability decreases immediately following a competitive soccer match in amateur players. Furthermore, we assessed the role of the preferred and non-preferred limbs to kick a ball in rotatory knee stability and the correlation between performance parameters and rotatory knee stability. We hypothesized that the knee stability decreases immediately after a competitive soccer match in amateur players. Eight healthy amateur soccer players (aged 27.2 ± 4.7 years and with body mass index of 23.8 ± 1.2 kg m-2) were included immediately before and after a competitive soccer match. The rotatory knee stability was assessed in the preferred and non-preferred limbs through the acceleration and jerk of the pivot shift maneuver and by the internal knee rotation of a pivoting landing task. Two-way repeated-measures ANOVA for factors time (before and after the soccer match) and limb (preferred and non-preferred) and multiple comparisons were performed using α = 5%. There was a statistical significance for the main factor time in the acceleration (5.04 vs. 6.90 ms-2, Δ = 1.86 ms-2, p = 0.020, η2 = 0.331) and jerk (18.46 vs. 32.10 ms-2, Δ = 13.64 ms-2, p = 0.004, η2 = 0.456) of the pivot shift maneuver. Rotatory stability decreases following a competitive soccer match in amateur soccer players under fatigue. Both the acceleration and jerk during the pivot shift maneuver is increased without significant internal knee rotation changes during the pivoting landing task.

Análisis biomecánico de la continuación prepatelar del cuádriceps / Biomechanical assessment of the prepatellar quadriceps continuation

OBJETIVO Determinar la resistencia máxima a la tracción (RMT) de la continuación prepatelar del cuádriceps (CPC).MATERIALES Y MÉTODOS Se realizó un estudio en cadáveres humanos. Fueron incluidos diez especímenes, en los cuales se utilizaron los tercios proximal y medial de la cortical anterior de la patela para evaluar las propiedades mecánicas de la CPC. En cada espécimen, se estudió un área de sección transversal de 0,2 cm2 (A1) y 1 cm2 (A2). Se aplicó una carga gradual para determinar la RMT.RESULTADOS La mediana de la RMT en el A1 fue de 232,56 N (rango: 141,23 N a 295,33 N) y en el A2 fue de 335,30 N (rango: 216,45 N a 371,40 N). El incremento en la TMR fue significativo entre las 2 áreas (p = 0,006).CONCLUSIÓN El ignificado clínico de este estudio es que la CPC es un tejido fuerte que puede servir de anclaje seguro para reconstrucciones alrededor de la patela. Un área relativamente pequeña tolera al menos 140 N y, a medida que crece el área, también aumenta la RMT.

OBJETIVE To determine the ultimate tensile strength (UTS) of the prepatellar quadriceps continuation (PQC). MATERIALS AND METHODS A human cadaveric study was performed. Ten fresh-frozen specimens were used. The proximal and medial thirds of the anterior cortex of the patella were used to assess the mechanical properties of the PQC. In each specimen, transverse section areas measuring 0.2 cm2 (A1) and 1 cm2 (A2) were studied. A gradual load was applied to determine the UTS. RESULTS The median UTS of A1 was of 232.56 N (range: 141.23 N to 295.33 N), and that of A2 was of 335.30 N (range: 216.45 N to 371.40 N). The increment in UTS was significant between the 2 areas (p » 0.006). CONCLUSION The clinical significance of the present study lies in the fact that it shows that the PQC is a strong tissue that can be a safe anchor for reconstruction around the patella. A relatively small area supports at least 140 N, and, as the area grows, the UTS increases as well.

Effects of Elbow Crutch Locomotion on Gluteus Medius Activation During Stair Ascending.

Crutches can help with the locomotion of people with walking disorders or functional limitations. However, little is known about hip muscle activation during stair ascending using different crutch locomotion patterns in people without disorders and limitations. Thus, we determined the acute effects of elbow crutch locomotion on gluteus medius (GM) activity during stair ascending. This comparative analytic cross-sectional study enrolled ten healthy men (22.0 ± 0.47 years). Participants climbed up the stairs with elbow crutches using one or two crutches, with ipsilateral or contralateral use, and after loading or unloading a limb. EMG signals were recorded from anterior, middle, and posterior portions of the GM and compared between the crutch conditions. The Kruskal-Wallis test and Dunn's multiple comparison test were performed (α = 5%). The activation of the GM increased with the ipsilateral use of crutches, with two crutches and three points, and when all the load depended only on one limb. GM activation decreased with contralateral use and in the unload limb. In conclusion, ascending stairs with elbow crutches alters the GM activation. The more critical factors were choosing the crutches' lateral use, the number of crutches, and if the limb is loaded or unloaded while ascending the stairs. Our findings can be helpful to increase or decrease the GM activation for those who use or will use crutches.

Steadiness training improves the quadriceps strength and self-reported outcomes in persistent quadriceps weakness following nine months of anterior cruciate ligament reconstruction and failed conventional physiotherapy.

Background Persistent quadriceps weakness may occur after anterior cruciate ligament reconstruction, limiting the strength gain. However, steadiness strengthening might change the inability to gain strength. Hence, we determined whether strength training with force steadiness and visual biofeedback can improve knee quadriceps torque, self-reported pain and knee stability in patients with persistent quadriceps weakness after knee anterior cruciate ligament reconstruction. Methods Twenty-five patients (aged 43.7 ± 12.2 years) with persistent quadriceps weakness following knee anterior cruciate ligament reconstruction and 34-weeks of physiotherapy performed unilateral strength training for both lower limbs. Four-weeks of conventional physiotherapy at week-30 were given, confirming the inability to gain torque. Then, steadiness training (isometric knee extension with visual biofeedback) was given for 7-weeks. Knee quadriceps peak torque, strength improvement, determination of responders to the intervention, coherence of strength gain between limbs, and self-reported outcomes (pain and knee stability) were obtained. Descriptive statistics and data inference using mixed-ANOVA, McNemar test, and χ2 test were described. Findings Quadriceps torque in the reconstructed knee improved (98.2 ± 47.2-155.2 ± 78.9 Nm; p = 0.031) for most patients (84%). Nevertheless, the torque was lower than the healthy side maintaining asymmetry (155.2 ± 78.9 vs. 209.5 ± 101.8 Nm; p = 0.026). There was high (20%) and medium coherence (80%) between limbs. Knee stability and pain improved in 72% of the patients (p < 0.001). Interpretations Steadiness training after anterior cruciate ligament reconstruction followed 9 months of surgery and failed conventional physiotherapy, improves the persistent weakness and self-reported outcomes, but gain strength was dissimilar between limbs.

Biased instantaneous regional muscle activation maps: Embedded fuzzy topology and image feature analysis.

The instantaneous spatial representation of electrical propagation produced by muscle contraction may introduce bias in surface electromyographical (sEMG) activation maps. Here, we described the effect of instantaneous spatial representation (sEMG segmentation) on embedded fuzzy topological polyhedrons and image features extracted from sEMG activation maps. We analyzed 73,008 topographic sEMG activation maps from seven healthy participants (age 21.4 ± 1.5 years and body mass 74.5 ± 8.5 kg) who performed submaximal isometric plantar flexions with 64 surface electrodes placed over the medial gastrocnemius muscle. Window lengths of 50, 100, 150, 250, 500, and 1,000 ms and overlap of 0, 25, 50, 75, and 90% to change sEMG map generation were tested in a factorial design (grid search). The Shannon entropy and volume of global embedded tri-dimensional geometries (polyhedron projections), and the Shannon entropy, location of the center (LoC), and image moments of maps were analyzed. The polyhedron volume increased when the overlap was <25% and >75%. Entropy decreased when the overlap was <25% and >75% and when the window length was <100 ms and >500 ms. The LoC in the x-axis, entropy, and the histogram moments of maps showed effects for overlap (p < 0.001), while the LoC in the y-axis and entropy showed effects for both overlap and window length (p < 0.001). In conclusion, the instantaneous sEMG maps are first affected by outer parameters of the overlap, followed by the length of the window. Thus, choosing the window length and overlap parameters can introduce bias in sEMG activation maps, resulting in distorted regional muscle activation.

Efectos del autoinjerto hueso-tendón patelar-hueso sobre la posición articular y la fuerza en pacientes con reconstrucción del ligamento cruzado anterior / Effects of bone-patellar tendon-bone autograft on joint position and strength in patients with anterior cruciate ligament reconstruction

RESUMEN: El objetivo del estudio fue comparar el déficit propioceptivo a través del Joint position sense (JPS) y Force steadiness en pacientes con reconstrucción del ligamento cruzado anterior (LCA) injerto hueso-tendón patelar-hueso (HTH) 6 a 12 meses postcirugía. Participaron 15 pacientes (13 hombres y 2 mujeres, 25,5 ± 1,3 años) con reconstrucción de LCA con autoinjerto HTH y 20 personas sin lesión del LCA (19 hombres y 1 mujer, 24,1 ± 0,8 años). Para evaluar la sensación de posición de la articulación de la rodilla se midió la Joint position sense (JPS) en tres rangos: 0°-30°, 31°-60° y 61°-90° y la sensación de fuerza del cuádriceps fue evaluada con la prueba Force steadiness (FS) al 15 % de la contracción voluntaria máxima (CVM), ambas pruebas realizadas 6 a 12 meses post cirugía. Los resultados mostraron que no hubo diferencias estadísticamente significativas en la sensación de la posición articular (JPS 0°-30°) (p=0.564) y 31°-60° (p=0.681), mientras que en el rango 61°-90° (p=0.003) existieron diferencias estadísticamente significativas. En las mediciones de sensación de fuerza del cuádriceps (FS al 15 % CVM) entre los pacientes operados de LCA técnica HTH y el grupo control no hubo diferencias estadísticas (p= 0.987) La sensación de la fuerza del cuádriceps medida con la prueba FS al 15 % CVM no presentaría déficit entre los 6 a 12 meses en pacientes post operados de LCA al ser comparados con sujetos sin lesión ni cirugía de este ligamento. Se concluye que la sensación de la posición articular medida con la prueba JPS en en tres rangos articulares de pacientes con reconstrucción de LCA injerto HTH 6 a 12 meses post cirugía sólo mostró alteraciones en el rango de 61°- 90° al ser comparado con el grupo control, lo cual indica que la sensación de la posición articular presenta un déficit en este rango específico.

SUMMARY: The aim of the study was to compare the proprioceptive deficit through the Joint position sense (JPS) and Force steadiness in patients with anterior cruciate ligament (ACL) bone-patellar tendon-bone graft (PTH) reconstruction 6 to 12 months post-surgery. Fifteen patients (13 men and 2 women, 25.5 ± 1.3 years) with ACL reconstruction with HTH autograft and 20 persons without ACL injury (19 men and 1 woman, 24.1 ± 0.8 years) participated. To assess knee joint position sensation, Joint position sense (JPS) was measured in three ranges: 0°-30°, 31°- 60° and 61°-90° and quadriceps strength sensation was assessed with the Force steadiness (FS) test at 15 % of maximal voluntary contraction (MVC), both tests performed 6 to 12 months post surgery. The results showed that there were no statistically significant differences in joint position sensation (JPS 0°-30°) (p=0.564) and 31°-60° (p=0.681), while in the range 61°-90° (p=0.003) there were statistically significant differences. In the quadriceps strength sensation measurements (FS at 15 % CVM) between the patients operated on ACL HTH technique and the control group there were no statistical differences (p= 0.987). The quadriceps strength sensation measured with the FS test at 15 % CVM would not present a deficit between 6 to 12 months in post- operated ACL patients when compared to subjects without injury or surgery of this ligament. It is concluded that the joint position sensation measured with the JPS test in three joint ranges of patients with ACL reconstruction HTH graft 6 to 12 months post surgery only showed alterations in the range of 61°- 90° when compared to the control group, indicating that the joint position sensation presents a deficit in this specific range.

Intraoperative pivot-shift accelerometry combined with anesthesia improves the measure of rotatory knee instability in anterior cruciate ligament injury.

PURPOSE: The knee stiffness acquired following an Anterior Cruciate Ligament (ACL) injury might affect clinical knee tests, i.e., the pivot-shift maneuver. In contrast, the motor effects of spinal anesthesia could favor the identification of rotatory knee deficiencies prior to ACL reconstruction. Hence, we hypothesized that the intra-operative pivot-shift maneuver under spinal anesthesia generates more acceleration in the lateral tibial plateau of patients with an injured ACL than without. METHODS: Seventy patients with unilateral and acute ACL rupture (62 men and 8 women, IKDC of 55.1 ± 13.8 pts) were assessed using the pivot-shift maneuver before and after receiving spinal anesthesia. A triaxial accelerometer was attached to the skin between Gerdys' tubercle and the anterior tuberosity to measure the subluxation and reduction phases. Mixed ANOVA and multiple comparisons were performed considering the anesthesia and leg as factors (alpha = 5%). RESULTS: We found a higher acceleration in the injured leg measured under anesthesia compared to without anesthesia (5.12 ± 1.56 m.s- 2 vs. 2.73 ± 1.19 m.s- 2, p < 0.001), and compared to the non-injured leg (5.12 ± 1.56 m.s- 2 vs. 3.45 ± 1.35 m.s- 2, p < 0.001). There was a presence of significant interaction between leg and anesthesia conditions (p < 0.001). CONCLUSIONS: The pivot-shift maneuver performed under anesthesia identifies better rotatory instability than without anesthesia because testing the pivot-shift without anesthesia underestimates the rotatory subluxation of the knee by an increased knee stiffness. Thus, testing under anesthesia provides a unique opportunity to determine the rotational instability prior to ACL reconstruction.

Intrasession Real-time Ultrasonography Feedback Improves the Quality of Transverse Abdominis Contraction.

OBJECTIVE: The purpose of this study was to compare changes in thickness of the transverse abdominis during performance of the hollowing exercise guided by feedback using ultrasonography images together with verbal guidance and using verbal guidance alone. We also determined the minimal detectable change and agreement between normalized pressures and muscle thickness. METHODS: Twenty participants without lumbar pain performed the hollowing exercises with or without ultrasonography feedback: 7 men and 13 women, mean (SD) age = 25 (5) years, height = 166 (10) cm, body mass = 64 (6) kg, body mass index = 22.2 (5.8) kg/m2. The thickness of the transverse abdominis was quantified during the exercise using musculoskeletal ultrasonography. Basal and 3 repetitions guided by an evaluator were performed. Pressure was determined using a lumbar cushion. Data were compared with a mixed-model analysis of variance and Bonferroni post hoc test (P < .05). Minimal detectable changes were identified and Bland-Altman analysis performed considering normalized thickness and pressure. RESULTS: Ultrasonography feedback resulted in larger thickness changes (P < .05). The lowest minimal detectable changes were achieved using ultrasonography feedback. Nonagreement was found between normalized thickness and pressure. CONCLUSION: Contraction of the transverse abdominis is improved using real-time ultrasonography together with verbal feedback. Low changes in muscle contraction estimated by thickness showed nonagreement with a pressure cushion.

Concentración de bupivacaína y preservación de fuerza de cuádriceps en bloqueo femoral para artroplastía total de rodilla / Bupivacaine concentration and quadriceps strength preservation in femoral nerve block for total

INTRODUCTION: The commonly used concentrations of local anesthetics (LA) for femoral nerve block (FNB) cause a significant decrease in the quadriceps strength (QS), limiting physiotherapy and determining a risk factor for patient's falls. The use of more dilute solutions could determine the preservation of motor function without impairing analgesia. METHODS: Five patients scheduled for total knee arthroplasty (TKA) received a preoperative FNB with 20 mL of bupivacaine in decreasing concentrations (0.0875%, 0.075%, 0.0625%, 0.050%, 0.0375%). Sensory block to cold in the anterior knee region, QS, surface electromyography (SEMG) of vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) plus were recorded before and 30 minutes after the blockage. Posteriorly, the clinical data of 20 patients who underwent TKA and received a continuous femoral nerve block (CFNB) with bupivacaine in the most dilute concentration that granted sensory blockade and significantly preserved the QS in the previous analysis were retrospectively analyzed. Postoperative pain at 24 and 48 hours, morphine consumption at 24 hours, the ability to successfully perform physiotherapy on the first postoperative day (POD) and reports of falls were rescued from the patients' files. Finally, seventy-five patients that underwent TKA during 2018 who received a CFNB with a similar dilution, but using levobupivacaine, were also retrospectively analyzed. Postoperative pain, need for advanced rescue analgesia, ability to perform physiotherapy, CFNB related complications and reports of patients falls during the first 72 hours post-surgery were obtained. RESULTS: Biomechanical study: of the 5 concentrations analyzed, either 0.050% or 0.0375% bupivacaine were adequate producing sensory block and preserving 94% and 100% of the basal QS, respectively. With both concentrations, the SEMG showed a similar range of activation with respect to baseline values. Bupivacaine case series: Twenty patients undergoing TKA received a 5-8 mL/hr infusion of 0.037% bupivacaine. The average consumption of morphine at 24 hours was 3.9 (3.6) mg. The median [IQR] of dynamic postoperative pain at 24 and 48 hours was 3 [1-4] and 3 [2-5]. All patients had adequate active joint ranges at 24 hours and physiotherapy was not limited by significant motor block. No falls were reported during the stay. Levobupivacaine case series: seventy-five patients undergoing TKA received a 5-8 mL/hr infusion of 0.037% levobupivacaine. The median [IQR] of at rest (R) and dynamic (D) postoperative pain at 24, 48 and 72 hours were R24: 0 [0-3]; D24: 3 [1-5]; R48: 0 [0-2]; D48: 3 [1.5-5]; R72: 0 [0-1]; D72: 3 [1-4]. 21% of patients required adding a PCA mode to the CFNB and a 7% a morphine PCA. On POD 1, 4% of patients were not able to adequately perform rehabilitation. On POD 2 and 3, all patients had adequate active joint ranges and physiotherapy was not limited by significant motor block. There were also no falls during hospitalization. CONCLUSIONS: The use of diluted solutions of bupivacaine and levobupivacaine for CFNB may represent a good alternative for TKA postoperative analgesia while avoiding significant quadriceps paresis. Additional studies are necessary to determine the ideal concentration and administration regimen to then compare with other quadriceps sparing analgesic alternatives.

INTRODUCCIÓN: Las concentraciones habituales de anestésicos locales (AL) utilizadas para el bloqueo del nervio femoral (BNF) provocan una disminución significativa de la fuerza del cuádriceps (FC), limitando la fisioterapia y constituyendo un factor de riesgo de caídas de pacientes. El uso de soluciones más diluidas podría determinar preservación de la función motora sin perjudicar la analgesia. MÉTODOS: Cinco pacientes programados para artroplastía total de rodilla (ATR) recibieron un BNF preoperatorio con 20 mL de bupivacaína en concentraciones decrecientes (0,0875%, 0,075%, 0,0625%, 0,050%, 0,0375%). Se registró la FC, electromiografía de superficie (EMGS) de vasto lateral (VL), vasto medial (VM) y recto femoral (RF) y el bloqueo sensitivo al frío antes y 30 minutos después del bloqueo. Posteriormente, se analizó retrospectivamente 20 casos sometidos a ATR que recibieron un bloqueo continuo del nervio femoral (BCNF) con bupivacaína en la concentración más diluida que otorgó bloqueo sensitivo y preservó significativamente la fuerza basal del cuádriceps durante el análisis anterior. El dolor postoperatorio a las 24 y 48 horas, el consumo de morfina las primeras 24 horas, la capacidad de realizar con éxito la fisioterapia el primer día postoperatorio (DPO) y reporte de caídas fueron rescatados de los expedientes. Por último, también se analizó retrospectivamente un grupo de 75 pacientes sometidos a ATR durante el 2018 y que recibieron un BCNF con una dilución similar, pero de levobupivacaína. Se obtuvieron datos de dolor, requerimientos de rescate analgésico, capacidad de realizar rehabilitación, complicaciones del BCNF y reporte de caídas durante las primeras 72 horas postoperatorias. RESULTADOS: Estudio biomecánico: de las 5 concentraciones analizadas, tanto bupivacaína 0,05% como 0,0375% produjeron adecuado bloqueo sensorial preservando el 94% y el 100% de la FC, respectivamente. Con ambas concentraciones la EMGS mostró similar rango de activación respecto a valores basales. Serie de casos con bupivacaína: veinte pacientes sometidos a ATR recibieron una infusión de bupivacaína 0,037% a 5-8 mL/h. El consumo promedio de morfina a las 24 horas fue 3,9 (3,6) mg. La mediana [RIC] del dolor dinámico postoperatorio a las 24 y 48 horas fue 3 [1-4] y 3 [2-5]. Todos los pacientes tuvieron rangos articulares activos adecuados a las 24 horas y la fisioterapia no fue limitada por bloqueo motor significativo. No se registraron caídas durante la hospitalización. Serie de casos levobupivacaína: setenta y cinco pacientes sometidos a ATR recibieron una infusión de levobupivacaína 0,037% a 5-8 mL/h. La mediana [RIC] de dolor postoperatorio en reposo (R) y dinámico (D) a las 24, 48 y 72 horas fue R24: 0 [0-3]; D24: 3 [1-5]; R48: 0 [0-2]; D48: 3 [1.5-5]; R72: 0 [0-1]; D72: 3 [1-4]. Un 21% requirió agregar modo PCA al BCNF y 7% una PCA de morfina. En DPO 1, un 4% de pacientes no pudo realizar adecuadamente la rehabilitación. En DPO 2 y 3 todos los pacientes tuvieron rangos articulares activos adecuados y fisioterapia no fue limitada por bloqueo motor significativo. Tampoco se registraron caídas durante la hospitalización. CONCLUSIONES: El uso de soluciones diluidas de bupivacaína y levobupivacaína en BCNF podría representar una buena opción para analgesia postoperatoria en ATR evitando la paresia significativa del cuádriceps. Estudios adicionales son necesarios para determinar la concentración y régimen de administración ideal para luego comparar con otras alternativas analgésicas preservantes del cuádriceps.

Evaluation of atraumatic hip instability measured by triaxial accelerometry during walking.

Hip joint instability has been targeted as an important issue that affects normal hip function. The diagnosis of hip instability could be very challenging and currently, there is no definitive diagnostic test. Hip instability results in an excessive amount of translation of femoroacetabular articulation, leading to changes on the dynamic loading of the hip. These changes in femoroacetabular translation could be evaluated by human movement analysis methods. The purpose of this study was to describe the triaxial and overall magnitude of acceleration in patients diagnosed with hip instability during gait cycle and compare those results with a control group. Our hypothesis was that acceleration values obtained from the instability group would be higher than asymptomatic controls. Ten patients with previously diagnosed hip instability were included and 10 healthy and asymptomatic subjects were enrolled as control group. Triaxial accelerometers attached bilaterally to the skin over the greater trochanter were used to record acceleration during walking on a treadmill. The overall magnitude of acceleration and the axial, anteroposterior and mediolateral accelerations (x/y/z) were obtained during gait. Mean overall magnitude of acceleration was higher in the hip instability group compared with the control group, 1.51 g (SD: 0.23) versus 1.07 g (SD: 0.16) (P = 0.022). The axial, anteroposterior and mediolateral accelerations significantly differed between the two groups. The axial and mediolateral accelerations showed to be higher for the hip instability group while the anteroposterior axis acceleration was lower.

Comparison of total hip arthroplasty surgical approaches by Statistical Parametric Mapping.

BACKGROUND: The most common surgical approaches in use for total hip arthroplasty are the lateral and posterior. When comparing these approaches in terms of gait biomechanics, studies usually rely on pre-defined discrete variables related to the events of gait cycle. However, this analysis may miss differences in other parts of the movement pattern that are not explored. We applied Statistical Parametric Mapping to compare hip kinematics between patients who underwent arthroplasty using either a lateral or posterior approach, contrasting these results with discrete variable analysis. METHODS: Twenty-two participants (11 lateral, 11 posterior; age between 50 and 80 years) underwent gait analysis before, 3 weeks and 12 weeks after hip arthroplasty. One-dimensional (e.g. time-varying) trajectories and zero-dimensional (e.g. peak extension) discrete variables were used to assess differences between groups in each plane of hip movement (sagittal, frontal, and transverse). FINDINGS: One-dimensional and zero-dimensional analyses found no significant differences between groups. Statistical Parametric Mapping revealed that both groups presented significant changes over time in hip adduction at 11-43% of the gait cycle. Zero-dimensional analysis seems to overstate sagittal plane changes over time since no such changes were found by Statistical Parametric Mapping. INTERPRETATION: Our results agreed with previous studies suggesting that surgical approach do not affect hip kinematics at the early post-operative stage after arthroplasty. However, Statistical Parametric Mapping revealed changes in frontal plane kinematics over time that were underestimated by the zero-dimensional variables. These findings suggest hip adduction impairment up to 12 weeks after arthroplasty.

Ankle perturbation generates bilateral alteration of knee muscle onset times after unilateral anterior cruciate ligament reconstruction.

BACKGROUND: The aim of this study was to compare muscle activation onset times of knee muscles between the involved and uninvolved knee of patients with unilateral anterior cruciate ligament reconstruction (ACLR), and the uninjured knees of healthy subjects after a controlled perturbation at the ankle level. METHODS: Fifty male amateur soccer players, 25 with unilateral ACLR using semitendinosus-gracilis graft (age = 28.36 ± 7.87 years; time after surgery = 9 ± 3 months) and 25 uninjured control subjects (age = 24.16 ± 2.67 years) participated in the study. Two destabilizing platforms (one for each limb) generated a controlled perturbation at the ankle of each participant (30°of inversion, 10°plantarflexion simultaneously) in a weight bearing condition. The muscle activation onset times of semitendinosus (ST) and vastus medialis (VM) was detected through an electromyographic (EMG) analysis to assess the neuromuscular function of knee muscles. RESULTS: Subjects with ACLR had significant delays in EMG onset in the involved (VM = 99.9 ± 30 ms; ST = 101.7 ± 28 ms) and uninvolved knee (VM = 100.4 ± 26 ms; ST = 104.7 ± 28 ms) when compared with the healthy subjects (VM = 69.1 ± 9 ms; ST = 74.6 ± 9 ms). However, no difference was found between involved and uninvolved knee of the ACLR group. DISCUSSION: The results show a bilateral alteration of knee muscles in EMG onset after a unilateral ACLR, responses that can be elicited with an ankle perturbation. This suggests an alteration in the central processing of proprioceptive information and/or central nervous system re-organization that may affect neuromuscular control of knee muscles in the involved and uninvolved lower limbs.

Differences between motor point and innervation zone locations in the biceps brachii. An exploratory consideration for the treatment of spasticity with botulinum toxin.

BACKGROUND: Botulinum toxin (BTX) acts on the neuromuscular junction which can be located by the innervation zone (IZ). Clinically, the motor point (MP) is homologous to the IZ and it is used as the injection site of BTX. Differences in the effectiveness of the application of BTX between MP and IZ locations have been determined. OBJECTIVE: Compare the location of the MP obtained using electrical stimulation and the location of the IZ using a linear surface electrodes array on the biceps brachii muscle. METHODS: The biceps brachii muscle of twenty men was assessed. The MP was located using the torque measurement generated by electrical stimulation. The IZ was detected using a linear surface electrodes array. RESULTS: A difference between the MP and the IZ positions (75.8 vs. 86.5mm, delta 10.7 mm; p=0.003, post-hoc power 0.89) was observed. DISCUSSION: The magnitude of the difference between the MP and the IZ may be clinically relevant. The IZ location using surface electromyography as a guide to optimize BTX injection is proposed.

Postural control and low back pain in elite athletes comparison of static balance in elite athletes with and without low back pain.

Although current research findings suggest that postural control or static balance is impaired in subjects with low back pain, few studies have specifically addressed the effect of low back pain on static balance in elite athletes. Forty-four athletes belonging to Chilean national teams took part in this study; 20 had low back pain and the remaining 24 were healthy controls. Displacement of the centre of pressure was analyzed by computerized platform posturography, using a standardized protocol; subjects were required to stand upright on both feet, with eyes first open then closed. The results showed that, athletes with low back pain used significantly more energy (p< 0.0182) and had a greater displacement of the centre of pressure (p< 0.005) with open eyes to control posture than healthy athletes. It may be concluded that static balance is impaired in elite athletes with low back pain and that analysis of two-footed stance provides a sensitive assessment of static balance in athletes.

Changes in surface EMG assessed by discrete wavelet transform during maximal isometric voluntary contractions following supramaximal cycling.

To better understand characteristics of neuromuscular fatigue in supramaximal cycling exercise, this study examined changes in surface electromyography (sEMG) frequency during maximal voluntary isometric contractions (MVC) following a 30-s Wingate anaerobic test (WAnT) using discrete wavelet transform (DWT). The changes in sEMG were also compared between DWT and mean frequency (MNF) obtained by fast Fourier transform (FFT). 17 healthy men performed a WAnT with a 7.5 % of body mass load. Knee extensor MVC torque was measured before and 1, 3, 6, 9, 12 and 15 min following WAnT, and sEMG was recorded from vastus lateralis muscle during the torque measures. sEMG was analysed for (RMS), MNF by FFT and frequency domains of DWT (divided into six domains). MVC torque decreased 21-23 % at 3-15 min, RMS increased 26-34 % at 1-15 min, and MNF decreased 8-10 % from baseline (76.3 ± 3.2 Hz) at 1-3 min post-cycling (P < 0.05). The DWT frequency domains showed that the changes lasted longer than MNF such that the intensity increased at 12 and 15 min for domain 2 (125-250 Hz), all time points for domain 3 (62.5-125 Hz), and 1-6 min for domains 4 (31.2-62.5 Hz) and 5 (15.6-31.2 Hz). The magnitude of increase in the intensity at 1 min post-exercise (45-60 %) was largest for domains 3 and 5 (P < 0.05). A significant correlation was evident only between the magnitude of changes in the domain 5 and MNF (r = -0.56). It is concluded that DWT provides information on neuromuscular fatigue that is not detected by MNF derived from FFT.