Anatomy and Physiology

20/10/2025

Here is a view if the leg you don't see often.
Remember, the lower extremity consists of the thigh (from the hip to the knee), and the leg (everything below the knee)

20/10/2025

The Subclavius Muscle – The Single Most Super Contracted

Muscle of Thoracic Outlet Syndrome

Muscle Origin: The subclavius originates from the junction of the first rib and its cartilage. Muscle Insertion: The subclavius inserts on the inferior surface of the middle of the clavicle. Muscle Action: The subclavius action is to depress the clavicle (collarbone). When the subclavius is in an abnormally contracted state, it draws the clavicle (and hence the shoulder) down and forward. It also lifts the first rib up into the thoracic outlet. The subclavius muscle is the only muscle that can compress the interscalene triangle, the costoclavicular, and the subpectoral space! I find incredibly inflamed subclavius spasms.

17/10/2025

Pelvis
X ray anatomy

17/10/2025

Dermatomes of the body:

A dermatome is an area of skin that is mainly supplied by afferent nerve fibres from the dorsal root of any given spinal nerve. There are 8 cervical nerves (C1 being an exception with no dermatome, it having only a motor root). All the cervical nerves emerge from above their numbeted vertebrae, hence C8 is the only cervical nerve root that emeges from below a cervicalvertebra, C7. There are 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these nerves relays sensation from a particular region of skin to the brain.
The demarcation of these dermatomes is not precise and overlaps can occur

Disclaimer:
The information and resources
provided on this page are for educational and informational purposes only.

16/10/2025

The arterial circle of Willis is formed from the two internal carotid arteries and the two vertebral arteries, merging into the basilar artery.
Mind you, the French call it the quadrilateral of Willis. After all, it does look that way

15/10/2025

Ever heard of Peroneus Quartus ❓

🦶 The peroneus quartus (PQ) muscle, also called fibularis quartus, is a supernumerary anatomical variant located in the lateral compartment of the leg, typically originating from the peroneus brevis and inserting on the calcaneus, cuboid or the lateral tubercle. Paul Hecker proposed that its presence in humans but absence in other primates represents an adaptive response to bipedal gait, contributing to lateral foot elevation and stabilization of the subtalar joint during pronation and supination (https://onlinelibrary.wiley.com/doi/10.1002/ar.1090260110).

🦶 Its presence, although often asymptomatic, has been implicated in mechanical crowding within the peroneal tunnel and in predisposing to peroneal tendon pathologies (https://onlinelibrary.wiley.com/doi/10.1002/ar.1090260110), https://pubmed.ncbi.nlm.nih.gov/2265813/, https://pubmed.ncbi.nlm.nih.gov/8976937/). MRI-based studies have improved detection of this muscle, yet its true prevalence and clinical significance remain controversial. The present study by Yuksel, Ergun, and Kose (2025, https://pubmed.ncbi.nlm.nih.gov/41008701/]) investigated the prevalence of the PQ on MRI in a large cohort and examined its associations with peroneal tendon (PT) pathologies.

🩻 A retrospective MRI review was conducted on 1160 ankle scans from 1073 patients (mean age = 42.7 ± 14.5 years; 643 females, 430 males) obtained between June 2021 and October 2023. Exclusion criteria included poor image quality, postsurgical or traumatic alterations, infections, and congenital deformities. The PQ was defined as an accessory muscle–tendon unit posterior or medial to the peroneus brevis and longus, typically inserting on the calcaneus.

📊 Results

👫 The PQ muscle was identified in 123 of 1160 ankles (10.6 %), more frequently in males (12.7 %) than females (9.2 %) (p = 0.018). No significant side predilection was found. Among 87 patients with bilateral imaging, PQ was bilateral in 5.7 %, unilateral in 13.8 %, and absent in 80.5 %.

▶️ PQ presence showed significant associations with:

▶️ PBT tendinitis: OR = 3.06 (95 % CI 1.73–5.41, p = 0.001)

▶️ PBT tear: OR = 3.64 (95 % CI 1.64–8.10, p = 0.003)

▶️ PLT tendinitis: OR = 2.43 (95 % CI 1.56–3.79, p = 0.001)

▶️ No significant relationship was found with tenosynovitis (p = 0.396) or PLT tear (p = 0.638).

Discussion💡

This large MRI-based study—one of the most extensive to date—demonstrated a PQ prevalence of 10.6 %. Male predominance has been inconsistently reported in prior works but was statistically significant here, supporting possible sex-linked anatomical differences (https://pubmed.ncbi.nlm.nih.gov/24740146/).

The PQ was significantly correlated with PBT tendinitis and tears, indicating localized mechanical stress or friction due to reduced retromalleolar space. These findings reinforce prior smaller imaging and surgical studies linking PQ with peroneal tendon pathology (https://pubmed.ncbi.nlm.nih.gov/14752761/, https://pubmed.ncbi.nlm.nih.gov/35606277/, https://pubmed.ncbi.nlm.nih.gov/15168186/). Conversely, the absence of an association with PLT tears or tenosynovitis suggests that PQ’s pathogenic influence is more pronounced on the peroneus brevis due to anatomical adjacency and shared sheath.

❎ Strengths, Limitations, and Future Directions

Key strengths include large sample size, standardized MRI evaluation, and expert consensus review. Limitations involve its retrospective design and absence of symptom correlation Future prospective studies should correlate PQ morphology with clinical presentation and biomechanical data to clarify causal mechanisms and therapeutic relevance.

15/10/2025

Facet mediated pain

14/10/2025

What is the limbic system?

In this video, I discuss the limbic system's role in emotion and I briefly describe some of the structures that are often included in the limbic system: the ...

13/10/2025

Autonomic nerves

13/10/2025

The Palmar Extrinsic Ligaments.

UT, ulnotriquetral ligament.
UC, Ulnocapitate ligament.
UL, Ulnolunate ligament.
SRL, Short radiolunate ligament.
LRL, Long radiolunate ligament.
RSC, Radioscaphocapitate ligament.