In recent years, the interest in the comprehension of the fasciae has significantly grown, together with the necessity of finding a consensus for a terminology of the fasciae in the research and clinical fields. Furthermore, it is becoming necessary to categorize the various types of fascia (superficial, deep, visceral, neural) since they possess different anatomical characteristics, and are implicated in different pathophysiological pathways. While in the past we have described the deep/muscular fascia, the aim of this work is to summarize and catalog the information relating to the human superficial fascia (thickness, cellular end extracellular matrix component, innervation, vascularization).

Muscle spindles have unique anatomical characteristics that can be directly affected by the surrounding tissues under physiological and pathological conditions. Understanding their spatial distribution and density in different muscles is imperative to unravel the complexity of motor function. In the present study, the distribution and number/density of muscle spindles in human and animal muscles were reviewed. We identified 56 articles focusing on muscle spindle distribution; 13 articles focused on human muscles and 43 focused on animal muscles. The results demonstrate that spindles are located at the nerve entry points and along distributed vessels and they relate to the intramuscular connective tissue. Muscles’ deep layers and middle segments are the main topographic distribution areas. Eleven articles on humans and thirty-three articles on animals (totaling forty-four articles) focusing on muscle spindle quantity and density were identified. Hand and head muscles, such as the pronator teres/medial pterygoid muscle/masseter/flexor digitorum, were most commonly studied in the human studies. For animals, whole-body musculature was studied. The present study summarized the spindle quantity in 77 human and 189 animal muscles. We identified well-studied muscles and any as-yet unfound data. The current data fail to clarify the relationship between quantity/density and muscle characteristics. The intricate distribution of the muscle spindles and their density and quantity throughout the body present some unique patterns or correlations, according to the current data. However, it remains unclear whether muscles with fine motor control have more muscle spindles since the study standards are inconsistent and data on numerous muscles are missing. This study provides a comprehensive and exhaustive approach for clinicians and researchers to determine muscle spindle status.

Peripheral nerve injury (PNI) is a complex clinical challenge resulting in functional disability. Neurological recovery does not always ensure functional recovery, as extracellular matrix (ECM) alterations affect muscle function. This study evaluates hyaluronan (HA) and collagen concentration in the gastrocnemius muscle and thoracolumbar fascia (TLF) in unilateral lower limb PNI rats to explore systemic ECM alterations following PNI and their impacts on functional recovery. Eighteen 8-week-old male Sprague-Dawley rats were divided into experimental (n = 12 left sciatic nerve injury) and control (n = 6) groups. After six weeks, motor function was evaluated. Muscle and TLF samples were analysed for HA and collagen distribution and concentrations. SFI and gait analysis confirmed a functional deficit in PNI rats 6 weeks after surgery. HA concentration in both sides of the muscles decreased by approximately one-third; both sides showed significantly higher collagen concentration than healthy rats (12.74 ± 4.83 µg/g), with the left (32.92 ± 11.34 µg/g) significantly higher than the right (20.15 ± 7.03 µg/g). PNI rats also showed significantly lower HA (left: 66.95 ± 20.08 µg/g; right: 112.66 ± 30.53 µg/g) and higher collagen (left: 115.89 ± 28.18 µg/g; right: 90.43 ± 20.83 µg/g) concentrations in both TLF samples compared to healthy rats (HA: 167.18 ± 31.13 µg/g; collagen: 47.51 ± 7.82 µg/g), with the left TLF more affected. Unilateral lower limb PNI induced HA reduction and collagen accumulation in both the lower limb muscles and the TLF, potentially exacerbating motor function impairment and increasing the risk of low back dysfunctions.

Muscle spindles (MSs) are essential for proprioception and motor control. The precise distribution and localization of MSs have been the focus of major research efforts to provide a foundation for understanding their roles in various diseases and motor dysfunctions. However, there are currently disagreements on the distribution patterns of MSs, and these discrepancies hinder the advancement of novel physical therapy techniques based on MS functionality. In this study, we present an innovative fascia-based distribution pattern for MSs. Using the rat quadriceps femoris muscle as the target, serial sections of the muscle were meticulously prepared following tissue sampling, fixation, and embedding. Furthermore, four additional rat gastrocnemius and eight human muscles were processed and cut into non-successive sections by the above method. The MSs were identified and characterized using Sirius Red staining, and their locations, quantities, associated structures, and basic parameters were documented via microscopy. Our findings demonstrate that the MSs are primarily located within the fascial layers and predominantly within the perimysium; the MS capsule is structurally continuous with the perimysium and forms multiple connections in different orientations. This study demonstrates that MSs are influenced by not only changes in muscle length but also alterations in the fascia tension or state, which may have more significant impacts. Furthermore, both nerves and vessels were observed near or within the capsule of the MS but were not always presented. In some sections, no microscopically distinguishable vessels or nerve fibers were observed around the MSs. This study proposes a novel fascia-based distribution model for MSs by highlighting that MSs are embedded within the fascial matrix and that the fascia may serve as a key structural marker for locating MSs. Additionally, the structural continuity of the fascia with the MS capsule suggests its role as a potential mediator in MS functions. The present study challenges the traditional concepts of MS distribution by introducing a more refined and efficient approach for studying MSs through the fascial perspective, thereby representing a significant advancement.

Background: Tibial plateau fractures (TPFs) are complex injuries often leading to long-term complications such as knee instability, limited range of motion, and osteoarthritis. Accurate diagnostic evaluations combining subjective and objective assessments are essential for identifying functional limitations, guiding rehabilitation, and improving recovery outcomes. This study examines the role of diagnostic predictors in differentiating recovery trajectories in two groups of patients treated for closed TPFs by open reduction and internal fixation (ORIF), comparing patients with less severe fractures and patients with more severe fractures (BCFs). Methods: A consecutive series of patients with a diagnosis of TPFs treated by ORIF at our institution between 2009 and 2016 were analyzed in this retrospective study. All injured patients were divided according to the Schatzker classification into two groups: mono-condylar (MCF) and bi-condylar (BCF) fracture patient groups. Diagnostic evaluations included patient-reported outcome measures (PROMs) such as KOOS, IKDC, and AKSS, alongside objective assessments of functional recovery using dynamometers, force platform tests (single-leg stance and squat jump variations), and measurements of active range of motion (AROM). Results: A total of 28 patients were included: 17 in the MCF patient group (Schatzker: 12 II; 5 III; 0 IV) and 11 in the BCF patient group (Schatzker: 6 V; 5 VI). Patients with less severe MCFs exhibited significantly better recovery outcomes, including higher KOOS (86.0 vs. 64.6, p = 0.04), IKDC (80.3 vs. 64.6, p = 0.04), and AKSS (95.3 vs. 70.5, p = 0.02) scores. They also demonstrated greater knee flexion (122.8° vs. 105.5°, p = 0.04) and faster neuromuscular recovery, as evidenced by higher rates of force development (RFD) during dynamic performance tests. Conversely, patients with more severe BCFs showed lower RFD values, indicating slower recovery and greater rehabilitation challenges. Conclusions: Integrating diagnostic tools like PROMs, AROM, and neuromuscular performance tests provides valuable insights into recovery after ORIF for TPFs. Fracture severity significantly impacts functional recovery patients with MCFs showing better outcomes and faster neuromuscular recovery, while subjects with BCFs require a longer rehabilitation treatment focusing on neuromuscular re-education and soft tissue recovery.

Peripheral nerve injury (PNI) is a complex clinical challenge affecting quality of life. Neurological recovery does not always ensure functional recovery as extracellular matrix (ECM) alterations affecting muscle function. This study evaluates hyaluronan (HA) and collagen concentration in gastrocnemius muscle and thoracolumbar fascia (TLF) in unilateral lower limb PNI rats to ex-plore systemic ECM alterations following PNI and their impacts on functional recovery. Eighteen 8-week-old male Sprague-Dawley rats were divided into experimental (n=12 with left sciatic nerve transection injury repaired by nerve conduit) and control (n=6) groups. After six weeks, motor function was evaluated. Muscle and TLF samples were analyzed for HA and collagen concentrations using Purple-Jelley HA Assay and Total-Collagen Assay kit. HA and collagen distribution was assessed using Alcian Blue and immunohistochemistry, and Picrosirius Red staining. In PNI rats, SFI and gait analysis were -87±9.12 and 1.32±0.29. Both sides of muscles showed significantly lower HA concentration than that in healthy rats (left p