14.2 Basic Human Anatomy, Common Injuries and Diseases & Diagnostic Tests
Key Takeaways
- The vertebral column has 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral and 4 fused coccygeal vertebrae, and disc herniations at C5-6, L4-5 and L5-S1 dominate New York bodily injury files.
- A sprain injures a ligament (bone to bone) while a strain injures a muscle or tendon; both are graded I through III.
- Third-degree (full thickness) burns are painless because the nerve endings are destroyed, and burn extent is estimated with the Rule of Nines.
- X-ray and CT image bone and acute bleeding, MRI images soft tissue such as discs, menisci and the rotator cuff, and EMG with nerve conduction studies assesses muscle and nerve function.
- Repetitive motion conditions such as carpal tunnel syndrome are handled in New York as occupational disease claims running from the date of disablement rather than first exposure.
Basic Human Anatomy, Common Injuries and Diseases & Diagnostic Tests
Exam Focus: The second half of the medical reports domain asks what the body part is, what the injury or disease is, and what each diagnostic test actually measures. The most frequently missed items are the distinction between a strain and a sprain, the degrees of burn, the fracture types, and which test images soft tissue (MRI) versus bone (X-ray, CT) versus nerve and muscle function (EMG and nerve conduction studies).
Skeletal Structure
The adult skeleton has 206 bones, divided into the axial skeleton (skull, vertebral column, ribs and sternum) and the appendicular skeleton (limbs, shoulder girdle and pelvic girdle).
The Vertebral Column — the single most claim-relevant structure
| Region | Vertebrae | Abbreviation | Common claim finding |
|---|---|---|---|
| Cervical | 7 | C1–C7 | Whiplash, C5-6 herniation, radiculopathy into the arm |
| Thoracic | 12 | T1–T12 | Compression fractures |
| Lumbar | 5 | L1–L5 | L4-5 and L5-S1 herniations, low back disability |
| Sacral | 5 fused | S1–S5 | S1 radiculopathy (sciatica) |
| Coccygeal | 4 fused | Coccyx | Tailbone injury from falls |
Between the vertebrae sit intervertebral discs, each with a tough outer annulus fibrosus and a gel-like nucleus pulposus. A bulge is a symmetric extension of the disc; a herniation (HNP) is a focal extrusion of nucleus through the annulus that may compress a nerve root and produce radiculopathy.
Other structures that recur in files
- Upper extremity: clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, phalanges.
- Lower extremity: femur, patella, tibia, fibula, tarsals, metatarsals, phalanges.
- Knee soft tissue: anterior and posterior cruciate ligaments (ACL/PCL), medial and lateral collateral ligaments (MCL/LCL), and the medial and lateral menisci.
- Shoulder soft tissue: the rotator cuff — supraspinatus, infraspinatus, teres minor and subscapularis — plus the labrum.
Body Systems in Brief
| System | Key components | Typical claim |
|---|---|---|
| Nervous | Brain, spinal cord (central); peripheral nerves | TBI, radiculopathy, reflex sympathetic dystrophy |
| Respiratory | Trachea, bronchi, lungs, diaphragm, pleura | Smoke inhalation, occupational lung disease, pneumothorax |
| Cardiovascular | Heart, arteries, veins, capillaries | Exertion-related cardiac events, hypertension |
| Abdominal organs | Liver, spleen, kidneys, pancreas, stomach, intestines | Blunt trauma, lacerated spleen, hernia |
| Musculoskeletal | Bones, joints, muscles, tendons, ligaments | The bulk of bodily injury claims |
| Integumentary | Skin, hair, nails | Burns, lacerations, scarring |
Common Injuries
Strain vs. Sprain — memorise this pair
- A strain is an injury to a muscle or tendon (tendon attaches muscle to bone). Think **“sT”rain = Tendon/muscle.
- A sprain is an injury to a ligament (ligament attaches bone to bone). Think **“spr”ain = ligament.
Both are graded I (mild, fibres stretched), II (partial tear) and III (complete rupture).
Dislocations and Subluxations
A dislocation is complete displacement of a bone from its joint; a subluxation is partial displacement. Reduction may be closed (manipulated back without surgery) or open (surgically).
Fractures
| Fracture type | Description |
|---|---|
| Closed (simple) | Bone broken, skin intact |
| Open (compound) | Bone breaks through the skin — infection risk, higher value |
| Greenstick | Incomplete break, common in children |
| Comminuted | Bone shattered into three or more fragments |
| Transverse / Oblique / Spiral | Break perpendicular / angled / twisting (spiral suggests a torsional mechanism) |
| Compression | Vertebral body collapses — typical of axial loading falls |
| Impacted | Ends driven into one another |
| Pathologic | Break through bone weakened by disease, e.g. osteoporosis or tumour |
| Avulsion | A fragment pulled off by tendon or ligament traction |
ORIF (open reduction internal fixation) denotes surgical realignment with plates, screws or rods — a significant reserve event.
Soft Tissue and Brain Injuries
- Contusion (bruise), laceration (cut), abrasion (scrape), hematoma (collection of blood).
- Concussion: a mild traumatic brain injury; post-concussion syndrome may persist for months.
- Subdural and epidural hematoma: bleeding beneath or above the dura mater — neurosurgical emergencies.
- Diffuse axonal injury: shearing of nerve fibres from rotational force, often with normal CT and abnormal MRI.
Burn Classifications
| Degree | Depth | Appearance |
|---|---|---|
| First degree (superficial) | Epidermis only | Red, painful, no blistering |
| Second degree (partial thickness) | Epidermis + dermis | Blistering, severe pain |
| Third degree (full thickness) | Through the dermis | White or charred, painless (nerve endings destroyed), grafting required |
| Fourth degree | Into muscle, tendon or bone | Catastrophic |
Extent is estimated by the Rule of Nines, which assigns percentages of total body surface area to each region.
Cumulative Trauma and Repetitive Motion
Not every compensable injury is a single event. Carpal tunnel syndrome, lateral epicondylitis (tennis elbow), rotator cuff tendinopathy and trigger finger arise from repetition. In New York these are handled as occupational disease claims, where the date of disablement — not the date of first exposure — starts the notice and filing clocks under Workers' Compensation Law §§ 18, 28 and 45.
Common Diseases That Appear as Causation Defences
| Condition | What it is | Why the adjuster cares |
|---|---|---|
| Arthritis / osteoarthritis | Degenerative joint disease | Pre-existing degeneration undermines traumatic causation |
| Osteomyelitis | Bone infection | A complication that extends an open fracture claim |
| Diabetes mellitus | Impaired glucose metabolism | Slows healing, complicates wound and amputation claims |
| Hypertension | Chronically elevated blood pressure | Underlying condition in cardiac claims |
| Atherosclerosis / coronary thrombosis | Arterial plaque / clot in a coronary artery | Central to exertion-related heart claims |
| Stroke (CVA) | Interrupted blood supply to the brain | Causation disputes after trauma or exertion |
| Tachycardia | Abnormally fast heart rate | Symptom, not a diagnosis |
| Glaucoma | Raised intraocular pressure damaging the optic nerve | Pre-existing vision loss |
| Lung disease (COPD, asbestosis, silicosis) | Chronic pulmonary impairment | Occupational exposure claims |
| Mental wellness conditions | Depression, anxiety, PTSD | Emotional distress and psychiatric components |
Medical Tests: What Each One Actually Shows
| Test | Modality | Best at showing |
|---|---|---|
| Laboratory studies | Blood, urine chemistry | Infection, toxicology, organ function |
| Radiography (X-ray) | Ionising radiation | Bone — fractures, dislocations, alignment. Poor for soft tissue |
| Computerized tomography (CT/CAT) | Cross-sectional X-ray | Acute bleeding, complex fractures; fast, the ED workhorse |
| Magnetic resonance imaging (MRI) | Magnetic field, no radiation | Soft tissue — discs, ligaments, menisci, rotator cuff, spinal cord |
| Myelography | Contrast injected into the spinal canal, then imaged | Nerve root compression when MRI is contraindicated |
| Electromyography (EMG) | Electrical activity of muscle | Denervation, radiculopathy |
| Nerve conduction studies (NCS/NCV) | Speed of signal along a nerve | Carpal tunnel, peripheral neuropathy |
| Arthroscopy | Fibre-optic scope inside a joint | Direct visualisation — both diagnostic and operative |
| Electrocardiogram (EKG/ECG) | Electrical activity of the heart | Arrhythmia, infarction |
| Electroencephalography (EEG) | Electrical activity of the brain | Seizure activity, encephalopathy |
Exam Discrimination: if the fact pattern involves a torn meniscus or rotator cuff, the answer is MRI, not X-ray. If it involves an acute head bleed in the emergency department, the answer is CT. If it involves numbness and tingling in the hand, the answer is EMG with nerve conduction studies.
An emergency department record documents a fall with an injury to the ligament of the lateral ankle and a separate injury to the calf muscle. How should these be described?
A claimant reports persistent numbness and tingling in the thumb, index and middle fingers after months of repetitive assembly work. Which combination of studies is designed to confirm the suspected diagnosis, and how does New York treat the claim?