Anatomy of Bone 😊

Anatomy of Bone

• No man’s land in flexor tendon → Zone 2

• Infertility workup → WHO grade 2 is most common

• BE FAN VEIN

• Patellar clunk syndrome

HLA associations

HLAs	Diseases
DQ1	• Pemphigus Vulgaris
DQ7	• BP variant
DQ2 / DQ8	• Celiac disease • Seal with DQ ()
DR2	• Good Pasteur’s (GBS) • Narcolepsy (DQB1:06:02) • Multiple sclerosis (B16, DR2) • 2nd - Good doctor () - have MS () - always sleeps ()
DR3	• Chronic active hepatitis • Dermatitis herpetiformis • SLE • Sjogren’s • T 1 DM
DR4	• Rheumatoid arthritis • Pemphigus vulgaris (DQ1, DR4)
DR5	• Hashimoto’s thyroiditis (DR3, DR5)
B27	• Ankylosing spondylitis • Reactive arthritis • Psoriatic arthritis
B35	• De Quervain's thyroiditis
B47	• CAH
B51	• Behcet’s disease
B57	• Abacavir hypersensitivity (B*57:01)

Composition of Bone

• Bone (Osteon) is composed of:
1. Organic component/Osteoid.
• Primarily proteins (90-95%).
• Collagen: Type I (Principal protein).
• Osteocalcin.
• Osteonectin.
• Cells (5-10%)
2. Water:
• Increased in children (Bones -> Softer).
3. Inorganic component:
• Calcium hydroxyapatite
• (Principal mineral).

Cells:

• Osteoblast:
• Cell type:
• Mononuclear cells.
• Function:
• Lays down osteoid matrix (collagen).
• Rich in alkaline phosphatase
• (responsible for mineral deposition).

• Osteoclast:
• Cell type:
• Monocyte aggregates,
• multinucleated giant cells.
• Function:
• Phagocytic,
• bone resorption, and remodelling.
• Rich in
• TRAP (Tartrate Resistant Acid Phosphatase)
• carbonic anhydrase.
• Least in number.

• Osteocyte:
• Cell type:
• Mature/resting osteoblast.
• Features:
• Most abundant,
• longest life span.
• Found within calcified matrix.

Note

• Bone and Meniscus of knee joint: Collagen type I.

• Articular hyaline cartilage: Collagen type II.

Bone Markers

• Formation markers:
• Pro collagen,
• Osteocalcin,
• Osteonectin,
• Alkaline phosphatase (ALP).

• Breakdown markers:
• Hydroxy proline,
• Hydroxy lysine,
• N & C telopeptide,
• Tartrate Resistant Acid Phosphatase (TRAP).

Note

• Bone formation markers can increase in bone resorption
• paradoxical
• indicating a healing response trying to keep up

• TRAP increases in osteoporosis
• due to increased osteoclast activity

Parts of Bone

• Medullary cavity:
• Contains marrow.
• In children it is red marrow.
• In adults, it's yellow bone marrow (fat).

• Epiphysis:
• End regions of the bone.

• Metaphysis:
• Region between epiphysis and diaphysis.
• Contains spongy/cancellous bone (medulla).
• Hairpin end arteries+

• Diaphysis:
• Shaft of the bone.
• Composed of compact/cortical bone (cortex).

• Endosteal lining:
• Lines the medullary cavity.

• Periosteum:
• Outer membrane of bone.

• Sharpey's fibers:
• Anchors periosteum to bone.

• Nutrient arteries:
• Supply blood to bone.

Growth Plate (Epiphyseal Plate/Physeal Plate)

• Only seen in children.

• Responsible for Longitudinal/interstitial growth.

• Structure (Layers from epiphysis to metaphysis):





1. Germinal layer
1. (most important):
2. Contains resting chondrocytes.
2. Proliferative layers:
1. Chondrocytes divide.
3. Hypertrophic layer
1. (weakest):
2. Chondrocytes enlarge.
4. Layer of calcification.
5. Layer of ossification.

Physeal Injuries

• Germinal layer injury:
• Leads to affected growth.

• Hypertrophic layer:
• Most commonly involved in traumatic injury.

Salter & Harris Classification of Physeal Injuries

• Mnemonic: SALTeR

• S - Type I (Split fracture):



• Features:
• Fracture splits growth plate
• without injuring the germinal layer
• through Hypertrophic layer > Calcific layer
• Normal growth on reducing the fracture.
• Prognosis: Good (Best).

• A - Type II (Above from the joint)



• Most common
• No injury to the germinal layer.
• Normal growth on reducing the fracture.
• Associated with a metaphyseal fragment
• Thurston Holland fragment
• Mnemonic: Thund fracture
• Prognosis: Good.

• L - Type III (Lower to the joint):



• Fracture line splits the growth plate and goes towards the epiphysis.
• Germinal layer will be injured.
• No growth on reducing the fracture.
• Tillaux # → Tibia
• Prognosis: Bad.

• T - Type IV (Through everything):



• Fracture line through all layers (epiphysis, growth plate, metaphysis).
• Germinal layer injured.
• Growth is impacted even on reducing the fracture.
• Prognosis: Bad.

• R - Type V (Rammer/Crushed/Rare/Looks fine but isn't):



• Impaction injury crushes the growth plate.
• Fracture is often missed on X-ray (no obvious fracture line).
• Late presentation with limb length discrepancy.
• Prognosis: Worst.

Fractures

Diagnosis

• Clinical (abnormal mobility) or Radiological (X-ray).

Causes of Fractures

• 1. Significant Trauma

• 2. Insignificant Trauma
• Leads to Stress Fracture
• Occurs in normal bone with abnormal loading
• Point tenderness is positive
• Leads to Pathological Fracture
• Occurs in abnormal/weak bone
• Pain precedes fracture due to pre-existing lesion

Causes of Pathological Fracture

• Localized Causes
• Infection
• Ischemia
• Lesions
• Cysts
• Radiation

• Generalized Causes
• Osteoporosis (most common)
• Common sites:
• Spine >
• Hip >
• Colles'
• Metastasis
• Common sites:
• Proximal femur
• Spine
• Osteogenesis imperfecta
• Osteopetrosis
• Scurvy,
• Rickets/Osteomalacia
• Paget’s disease

Note on Pathological fractures

• Vertebral compression fractures:
• Wedge fractures
• (most common bone involved in pathological fracture).

• Subtrochanteric proximal femur fracture:
• Banana fracture.

• Mirel's criteria:
• For prophylactic fixation of pathological fractures.
• Score > 8 indicates prophylactic internal fixation.
• Mnemonic: Myru → when > 8 for internal fixation

Stress Fractures

• Pain occurs after activity
• sudden increase in intensity/frequency

• LL > UL

• X-ray positive: 2 to 3 weeks later.

• IOC (Investigation of Choice):
• MRI
• detects occult fractures by showing soft tissue edema

• Multiple stress fractures:
• Require bone scan.

Sites:

1. Tibia.

1. Metatarsal:
1. March fracture
1. most common at
1. 2nd > 3rd metatarsal
2. neck > shaft
• Mnemonic: March → Left Right → kazhuth thirich

Types of fracture

Fracture Healing

Primary Healing (Direct/Intramembranous healing)

• Callus formation:
• Absent (or minimal).

• Movement at fracture site:
• Absolute stability.

• Devices:
• Compression plates,
• lag screws.

Secondary Healing (Indirect/Endochondral healing)

• Callus Present (prominent).

• Movement at fracture site:
• Micromovements (Relative stability).

• Devices:
• POP/casts/braces,
• external fixation,
• bridge plating,
• intramedullary nailing.

Stages of Secondary Healing

1. Hematoma formation (2-3 days).

2. Granulation tissue formation (2-3 weeks):
1. Inflammation + fibroblasts.

3. Callus formation (2-3 months):



1. Fibroblasts differentiate into osteoblasts.
2. Osteoblasts → lays Osteoid matrix → ↑ calcium deposition
3. Aka soft callus, Primary Callus
4. Indicate healing
5. Seen on Xray

4. Consolidation (2-3 years).



1. Callus become harder forms woven bone
2. Hard callus or secondary callus

5. Bone remodelling (3 years):
1. Woven bone is replaced by lamellar bone.

3 - 6 - 9 Rule

• Bone

• Bowel obstruction
• >3 cm dilatation: small bowel obstruction.
• >6 cm dilatation: colonic obstruction.
• >9 cm dilatation: caecal obstruction.

Non-union

Factors Affecting Fracture Healing (can lead to non-union)

• Patient factors:
• Age, nutrition, tobacco, alcohol.

• Treatment factors:
• Improper immobilization
• (most common cause),
• inadequate reduction.

• Fracture type:
• Open
• contaminated
• interposed
• soft tissue between bone ends

• Tissue factors: Ischemia.

3 - 6 - 9 Rule

• Bone

• Bowel obstruction
• >3 cm dilatation: small bowel obstruction.
• >6 cm dilatation: colonic obstruction.
• >9 cm dilatation: caecal obstruction.

Types of Non-union

Hypertrophic:

• Fracture:
• Smooth & sclerosed ends,
• visible fracture line.

• Due to Improper Immobilization:

• X-ray: Exuberant callus formation.

• Bone biology:
• Good bone
• biological capacity for healing exists

• Treatment:
• Immobilization.

Atrophic:

• Fracture:
• Smooth & sclerosed ends,
• visible fracture line.

• X-ray:
• Absent callus formation.

• Bone biology:
• Abnormal bone

• Treatment:
• Autologous bone grafting.

Bone Graft

• Most common site: Iliac crest.

• MOA
• Creeping substitution
• acts as a canvas for bone to grow

Ideal Bone Graft Characteristics

• Osteogenesis:
• Graft makes bone directly via osteoblasts.

• Osteoconduction:
• Acts as a scaffold for bone growth.

• Osteoinduction:
• Stimulates host bone formation.
• Growth factors induce mesenchymal cells → bone-forming cells.

Substitutes of Bone Graft

Malunion

• Healing in an anatomically abnormal position.

• TOC
• Osteotomy
• cut, realign, & fix bone

Note

• Fractures that undergo malunion rarely/never undergo non-union & vice versa.

Bones with Increased Risk of Malunion vs. Non-union

Management of Fractures

• Intra-articular fracture
• involves articular surface
• Open reduction + internal fixation with plates & screws.

• Extra-articular fracture:
• Conservative management:
• POP/cast, slab, traction.
• Surgical management (Definitive):
• Upper limb: Plating with screws.
• Lower limb: Intramedullary rods/nails with interlocking screws.

• Patella/Olecranon
• Fragment pulled by attached tendons
• TOC:
• Tension band wiring device with
• K-wires &
• stainless steel wires
• (converts distractive force into compressive force).

Fractures of Necessity (Require Surgical Management)

1. Intra-condylar fracture.

2. Lateral condylar humerus fracture.

3. Neck of femur fracture.

4. Monteggia/Galeazzi fracture.

• Mnemonic: Galezzi () de monte () neckil (neck of femur) laterally (lat condylar) akath (intra condylar) surgery cheyth → condom itt

Open Fractures

• Fracture + break in skin and underlying soft tissue.

• 2 Factors
• Most common pathogen:
• Staphylococcus aureus (affects healing).
• Fracture hematoma escapes outside.

• Most common bones involved:
• Tibia
• phalanges.

Gustilo Anderson Classification

• Type I: Wound < 1 cm long.

• Type II: Wound 1-10 cm.

• Type IIIa: Open fracture + contaminated environment (sewage, farms, firearm injury).
• Wound size usually > 10 cm.
• Mnemonic: Azhukk → A

• Type IIIb: Open fracture with periosteal stripping.
• Mnemonic: Stripping Bare → B
 

• Type IIIc: Open fracture + vascular injury (distal pulses not palpable).
• ONLY NEEDS OPEN REPAIR
• Mnemonic: Circulation → C

Management

A. Wound Management

1. Broad spectrum antibiotics.

2. Debridement.

3. Wound wash with:
1. Sterile normal saline,
2. Povidone iodine,
3. H2O2.

4. Wound closure delay if:
1. > 6 hr old injury,
2. new neurovascular injury,
3. edges cannot be approximated.

B. Fracture Management

• Steps
1. External fixation (EF) is the initially
2. followed by wound management & closure,
3. then definitive surgery.

1. Schanz pin with external rod:

• Can be uniplanar (one rod) or multiplanar (multiple rods).

2. Ilizarov ring fixator:

• Multiplanar.

• Uses rings and pins.

• Can perform
• compression,
• distraction or
• angulation at wound site
• Lengthen bone if required
• Distraction osteogenesis (AKA callotaxis)
• at 1 mm/day

• Indications/uses:
• Open fracture,
• non-union,
• infected non-union,
• deformity correction/malunion.
• fracture with bone loss,
• limb lengthening,

3. Rail fixators/limb reconstruction system:

• Adjustable rods,

• combination of
• compression and
• external fixation.

4. Spanning external fixator:

• Spans across the joint to increase stability.

• Use:
• Periarticular fracture of knee b/w
• distal femur
• proximal tibia fractures

Complications of Management

• Ring sequestrum (most common):
• Occurs at pin tract sites.
• Causes:
• Heat necrosis due to drilling,
• direct infection.

Stability of EF:

• ↑↑ by ↑↑ number of
• pins,
• rods,
• planes
• (biplanar > uniplanar).

Amputation

Trauma Scores (to assess limb salvage vs. amputation)

1. Mangled Extremity Severity Score (MESS):
• Messi = 7, Visa Kitti → But ponel kaalu vettanam
• Score ≤ 6 = salvageable
• Score ≥ 7 = Amputation (Not salvagable)
• Mnemonic: VISA.
• V: Velocity of injury or soft tissue coverage.
• I: Ischemia time (most important).
• S: Shock.
• A: Age of patient.
• Messed up leg → 6 thavayil kuravu tyre kalil kude keri irangiyal rakshapedutham else amputate

2. Limb Salvage Score.

3. Ganga Score.

4. Transcutaneous oxygen pressure
• most reliable and sensitive test for wound healing.
• < 20 mmHg ⇒ Amputate

Types

• Amputation:
• Cutting limb through the bone.

• Disarticulation:
• Cutting limb through a joint.

Terminology of Amputation (Lower Limb)

• Hip disarticulation.

• Midthigh/above-knee
• transfemoral amputation.

• Knee disarticulation.

• Below-knee
• transtibial amputation
• most common

• Foot amputations:
• Syme
• Chopart
• intertarsal joint
• Chop between tarsals
• Lisfranc
• tarsometatarsal joint
• Lisa Met (Lis → Tarsometatarsal) ChoTTa (Chop → Tarsal)
• Transmetatarsal.

Prosthesis

Advanced Trauma Life Support (ATLS)

Order of Intervention

• Mnemonic: ABCDE.
1. A - Airway: Chin lift/jaw thrust with restriction of cervical spine motion.
2. B - Breathing.
3. C - Circulation: Stop the bleeding.
4. D - Disability: Neurological status.
5. E - Exposure: Undress and environment (temperature control).

Note

• Fractures causing the most amount of blood loss:
• Pelvis > Femur.

Pelvic Fracture Management

• Can cause 1.5-2 L of blood loss leading to hemorrhage & death.
1. Pelvis binder/hands/bedsheets:
1. Preferred Immediate management
2. Tamponade the blood loss.
2. IV fluids: RL > NS.
3. External fixation of pelvis (in compression).

Avascular Necrosis (AVN)/Osteonecrosis

Classification

Traumatic:

• due to interruption of blood supply from trauma



• Fracture of Neck of femur
• AVN of head of femur
• Fracture of Waist of scaphoid
• AVN of proximal pole of scaphoid
• Fracture of Neck of talus
• AVN of body of talus

Non-traumatic:

• d/t ↑ intraosseous pressure → ↓ blood flow
• Idiopathic (most common).
• Steroid use.
• Sickle cell disease.
• Gaucher's disease.
• Alcohol abuse.
• Perthes' disease.
• Caisson disease.

FICAT STAGING

Bones with tendency for AVN

• Head of femur.

• Proximal pole of scaphoid.

• Body of talus.

• Proximal pole of lunate.

• Distal femoral condyle.

• Head of humerus.

• Capitulum.

X-ray

1. Reduced joint space

2. subcortical cysts,

3. patchy sclerosis, and

4. subcortical lucency (Crescent sign)

• Changes appear very late > 6 weeks

• X-ray
• Dead bone
• white/sclerosed
• jagged edges.

• IOC
• MRI
• early diagnosis

• TOC
• Total hip replacement
• for AVN of head of femur

Deformities