Electromyographic Determination of Jump Landing Sequence and Pre-activation Times During One-foot Landing

Introduction: Monopodal jumping is a common gesture in daily life and sports. In the Landing Phase (LF), potential energy is absorbed from the tridimensional stability of the Lower Limb (LH). This stability depends on neuromuscular strategies that include factors such as Muscle Preactivation Times (MAT) and the Sequence of Participation (SP) of the muscle groups. The alteration of TPA has been pointed out as a factor of possible injury. The aim of this study was to determine the preactivation times and participation sequence of the gluteus medius, adductor magnus, rectus femoris, vastus medialis quadriceps, biceps femoris longus, semimembranosus and soleus muscles during the monopodal jump landing in university students. At the same time, we sought to determine the existence or not of significant differences between men and women. Materials and methods: Twenty-six young adults, 16 women and 10 men, participated. An inertial sensor and 7 surface electrodes were used to collect electromyographic data in the gluteus medius, rectus femoris and vastus medialis quadriceps, semimembranosus, biceps femoris long head, soleus and adductor magnus muscles. Results: The general activation sequence was Vastus medialis -Biceps femoris longus - Adductor magnus - Gluteus medius - Rectus femoris -Semimembranosus and soleus. The data obtained reflects the activation prior to ground contact of all the muscles studied. There were differences between genders. Women presented a previous activation in all muscles with the exception of the gluteus medius. The muscles with the greatest variability were the adductor magnus in men and the rectus femoris in women. Conclusion: The significant differences found between men and women show that there are trends that can be the beginning to better understand the risk factors for injury generation. The TPA data presented a great variability which could reflect the existence of different activation patterns and not a unique behavior of the MMII musculature.

A Muscle Biosignature Differentiating Between Limb-Girdle Muscular Dystrophy and Idiopathic Inflammatory Myopathy on Magnetic Resonance Imaging

Background: The overlapping clinical presentations of limb-girdle muscular dystrophy (LGMD) and idiopathic inflammatory myopathy (IIM) make clinical diagnosis challenging. This study provides a comprehensive evaluation of the distributions and characteristics of muscle fat substitution and edema and aims to differentiate those two diseases.Methods: This retrospective study reviewed magnetic resonance imaging (MRI) of seventeen patients with pathologically proved diagnosis, comprising 11 with LGMD and 6 with IIM. The fat-only and water-only images from a Dixon sequence were used to evaluate muscle fat substitution and edema, respectively. The degrees of muscle fat substitution and edema were graded and compared using the appropriate statistical methods.Results: In LGMD, more than 50% of patients had high-grade fat substitution in the majority of muscle groups in the thigh and calf. However, <50% of IIM patients had high-grade fat substitution in all muscle groups. Moreover, LGMD patients had significantly higher grade fat substitution than IIM patients in all large muscle groups (p < 0.05). However, there was no significant difference in edema in the majority of muscle groups, except the adductor magnus (p = 0.012) and soleus (p = 0.009) with higher grade edema in IIM. Additionally, all the adductor magnus muscles in LGMD (100%) showed high-grade fat substitution, but none of them showed high-grade edema.Conclusions: MRI could be a valuable tool to differentiate LGMD from IIM based on the discrepancy in muscle fat substitution, and the adductor magnus muscle could provide a biosignature to categorizing LGMD.

Lateral Retinaculum Lengthening and Medial Patellofemoral Ligament Reconstruction With Adductor Sling Technique

Background: There are multiple ways of reconstructing the medial patellofemoral ligament (MPFL), including dynamic techniques that fix the graft to the adductor magnus tendon. We present this technique associated to an increasingly common surgery used as adjuvant in some patients with patellar instability, lateral retinaculum lengthening. Indications: Recurrent patellar dislocation with medial laxity and lateral tightness/lateral tilt. Technique Description: This is double bundle MPFL reconstruction with anterior tibialis tendon allograft. Both autograft or allograft may be used, with a minimum length of 15 cm. The graft is fixed to the proximal third of the patella, passing as a sling under the adductor magnus tendon where it is fixed with sutures and returns to the patella. The patellar fixation includes a 10 to 15 mm deep and 4 to 4.5 mm diameter tunnel in the proximal third with suture stitches to the soft tissues in the entrance of the tunnel, plus an anterior periostic tunnel for the second bundle in the proximal third of the patella fixed with suture stitches. Meanwhile, the lateral retinaculum is incised longitudinally into a superficial and deep layer, in order to lengthen it the desired length. Results: The expected outcome of the procedure is to have a stable patellofemoral joint, with patients that gain the lost function and may return to sport without recurrence of patellar dislocation. Discussion/Conclusion: This is a simple, cheap, and reproducible technique that corrects both medial laxity and lateral tightness for patients with recurrent patellar dislocation.

CLASSIFYING ISCHIAL TUBEROSITY AVULSION FRACTURES BY OSSIFICATION STAGE AND TENDON ATTACHMENT

Background: Currently, there is no classification system for ischial tuberosity avulsion fractures. Hypothesis/Purpose: To provide a new classification system for ischial tuberosity fractures based on the ossification pattern of the apophysis. Methods: We performed a retrospective records review of patients diagnosed with ischial tuberosity avulsion fractures at our institution from 2008 to 2018. Skeletal maturity (Modified Oxford score [MOS], Risser score), fracture type, size, and displacement were recorded based on initial injury radiographs. We reviewed a large series of pelvic CT and MRI scans from patients aged 10-19 years old to assess the ossification pattern and tendinous attachments of the ischial tuberosity. Pelvic CT review demonstrated a reproducible 5-stage pattern of ossification spanning the age of 13-19 years for males and 12-17 years for females (Figure 1). Review of available CTs and MRIs indicated that the semimembranosus attaches at the most lateral ossification center, followed by the conjoint tendon and adductor magnus as one moves medially (Figures 1). We created a classification system based on location of the ischial tuberosity avulsion fracture: Type 1 (lateral – semimembranosus and conjoint tendons) or Type 2 (complete – semimembranosus, conjoint, and adductor magnus tendons). An A or B descriptor was then added to distinguish minimally displaced (<1 cm) and displaced (≥1 cm) fractures, respectively (Figure 2). Results: We identified 45 ischial tuberosity fractures. Mean age was 14.4 years (range, 10.3–18). Males accounted for 82% of the cohort. Type 1 fractures accounted for 47% of cases and 53% were classified as Type 2. Type 1 fractures were associated with younger age chronological age (p=0.001), lower MOS (p=0.002), lower Risser score (p=0.002), less displacement (p=0.001), and smaller size (p<0.001), when compared with Type 2 fractures (Table 1). Of the 45 patients, 18 had >6 month follow-up with 56% going on to non-union. Non-union was associated with greater displacement (p=0.016) and size (p=0.027). When comparing union rates by fracture location, 33% of Type 1 fractures progressed to non-union, while 78% percent of Type 2 suffered a non-union; however, this difference did not reach statistical significance (p=0.153) (Table 2). Conclusion: In younger patients (ages 13-15 years), the lateral ossification centers of the ischial tuberosity, at which the hamstrings attach, are at risk for isolated avulsion injury. However, in older patients (16-18 years), coalescence of the hamstring and adductor magnus ossification centers predispose patients to a combined avulsion injury consisting of a larger fragment and with greater displacement. [Figure: see text][Figure: see text][Table: see text][Table: see text]

Thigh and Leg Muscle MRI Findings in GNE Myopathy

Background: Muscle MRI protocols have been developed to assess muscle involvement in a wide variety of muscular dystrophies. Different muscular dystrophies can involve muscle groups in characteristic patterns. These patterns can be identified in muscle MRI in the form of fatty infiltration. Objective: This study was conducted to add the existing knowledge of muscle MRI in GNE myopathy and evaluate the correlation of muscular involvement with different gene mutations. Methods: The MRI scans of the 18 GNE patients were analyzed retrospectively. Cluster analysis was done for grouping the muscles and patients. Results: The four muscles with the highest fat infiltration were adductor magnus, tibialis anterior, semitendinosus, and semimembranosus. Furthermore, three clusters of muscle involvement were found, including cluster 1, typical muscle involvement indicating muscles with the highest infiltration: extensor digitorum longus, gracilis, biceps femoris, soleus, gastrocnemius medial, adductor longus, tibialis anterior, adductor magnus, semimembranosus, semitendinosus; cluster 2, less typical muscle involvement indicating muscles with intermediate fat infiltration, peroneus longus, gastrocnemius lateral, and minimal fat infiltration in most of the patients, i.e., tibialis posterior; and cluster 3, atypical muscle involvement with low-fat infiltration: rectus femoris, sartorius, vastus intermedius, vastus medialis, and vastus lateralis. Conclusions: This study found three clusters of muscle involvement and three groups of patients among GNE patients. Hamstring muscles and the anterior compartment of the lower leg were the muscles with the highest fat infiltration. Moreover, a weak genotype-muscle MRI association was found in which tibialis posterior was more involved in patients with the most frequent mutation, i.e., C.2228T > C (p.M743T) mutation; however, this finding may be related to longer disease duration.

Anatomic and Biomechanical Properties of Flat Medial Patellofemoral Ligament Reconstruction Using an Adductor Magnus Tendon Graft: A Human Cadaveric Study

Background: In contrast to the majority of existing techniques for reconstruction of the medial patellofemoral ligament (MPFL), the technique described in this article uses the adductor magnus muscle tendon to gain a flat, broad graft, leaving its distal femoral insertion intact, and does not require drilling within or near the femoral physis. It also allows for soft tissue patellar fixation and could facilitate anatomic MPFL reconstruction in skeletally immature patients. Purpose: To evaluate the anatomic and structural properties of the native MPFL and the adductor tendon (AT), followed by biomechanical evaluation of the proposed reconstruction. Study Design: Descriptive laboratory study. Methods: The morphological and topographical features of the AT and MPFL were evaluated in 12 fresh-frozen cadaveric knees. The distance between the distal insertion of the AT on the adductor tubercle and the adductor hiatus, as well as the desired length of the graft, was measured to evaluate this graft’s application potential. Load-to-failure tests were performed to determine the biomechanical properties of the proposed reconstruction construct. The construct was placed in a uniaxial testing machine and cyclically loaded 500 times between 5 and 50 N, followed by load to failure, to measure the maximum elongation, stiffness, and maximum load. Results: The mean ± SD length of the AT was 12.6 ± 1.5 cm, and the mean distance between the insertion on the adductor tubercle and adductor hiatus was 10.8 ± 1.3 cm, exceeding the mean desired length of the graft (7.5 ± 0.5 cm) by 3.3 ± 0.7 cm. The distal insertion of the AT was slightly proximal and posterior to the insertion of the MPFL. The maximum elongation after cyclical loading was 1.9 ± 0.4 mm. Ultimately, the mean stiffness and load to failure were 26.2 ± 7.6 N/mm and 169.7 ± 19.2 N, respectively. The AT graft failed at patellar fixation in 2 of the initially tested specimens and at the femoral insertion in the remaining 10. Conclusion: The described reconstruction using the AT has potential for MPFL reconstruction. The AT graft presents a graft of significant volume, beneficial anatomic topography, and adequate tensile properties in comparison with the native MPFL following the data from previously published studies. Clinical Relevance: Given its advantageous anatomic relationship as an application that avoids femoral drilling and osseous patellar fixation, the AT may be considered a graft for MPFL reconstruction in skeletally immature patients.

Effect of iliopsoas muscle tightness on electromyographic activity of hip extensor synergists during gait

Background: Hip flexor muscles' tightness has been considered as one of the main risk factors for neuromuscular impairment of lower extremities not only lead to change the movement patterns but also probably result in changing the neuromuscular features of other muscles. The purpose of this research is study was to evaluate the iliopsoas tightness’ effect on electromyographic activity of hip extensor synergists during gait. Methods: In this case-control study fifteen 11-14 years old adolescents with iliopsoas tightness as experimental group, and 15 healthy adolescents which matched based on age, height, weight, body mass index, dominant leg and sport experience participated voluntarily as control group. Surface electromyographic activity of the gluteus maximus, adductor magnus and biceps femoris, were measured between groups during stance phase of gait. Results: Individuals with restricted hip flexor muscle length demonstrated more gluteus maximus activation during terminal stance (p=.001), more biceps femoris activation during mid stance (p=.002) and late stance (p=.001) and more adductor magnus activation during mid stance (p=.04) and late stance (p=.001). Conclusion: Adolescent soccer athletes with hip flexor muscle tightness exhibit more biceps femoris and adductor magnus and gluteus maximus activation during stance phase of gait. Thus, individuals with hip flexor muscle tightness appear to utilize different neuromuscular strategies to control lower extremity motion.