2. Closed mechanical injuries

1. Definition

• Closed mechanical injury → damage to tissues or organs by a mechanical force with intact skin and mucosa
• No direct route for bacteria → lower infection risk than open injuries
• Severe deep damage possible under normal-looking skin

2. Types

1. Contusion (contusio)
2. Haematoma
3. Sprain (distorsio)
4. Dislocation (luxatio)
5. Subcutaneous rupture → muscle, tendon, internal organ
6. Concussion (commotio)
7. Compression (compressio), crush syndrome
8. Closed fracture

3. Contusion (bruise)

Pathology

• Blunt force → damage to subcutaneous fat, small vessels and muscle without skin breach
• Bleeding into tissue:
  • Petechiae → pinpoint
  • Ecchymosis → diffuse bleeding in the tissue planes
  • Haematoma → collection of blood in a cavity
• Aseptic inflammation and oedema

Clinical picture

• Pain, swelling, tenderness
• Bruise colour changes with haemoglobin breakdown:
  1. Red-blue → first days
  2. Purple
  3. Green → biliverdin
  4. Yellow → bilirubin, after 1–2 weeks
• Partial loss of function

Treatment

• First 24–48 h → rest, ice, compression, elevation (RICE)
• After 48 h → warmth, mobilisation
• Analgesia

4. Haematoma

• Collection of blood in a tissue cavity
• Fluctuation on palpation; pulsation → suspect false aneurysm
• Outcomes:
  • Resorption
  • Organisation → fibrosis, calcification (myositis ossificans in muscle)
  • Encapsulation → seroma or cyst
  • Infection → abscess
• Morel-Lavallée lesion → closed degloving; skin and fat shorn off the fascia over the thigh or pelvis
• Treatment → RICE; large or tense collection → aspiration or evacuation

5. Sprain (distortion)

• Stretch or partial tear of a joint capsule or ligament without loss of joint congruity
• Joint returns to normal position after the force stops
• Most common → ankle, knee, wrist
• Grades:
  1. Grade I → stretch, joint stable
  2. Grade II → partial tear, mild laxity
  3. Grade III → complete tear, unstable joint
• Signs → pain, swelling, bruising, painful movement
• Treatment → RICE, elastic bandage, immobilisation 1–3 weeks; grade III → orthopaedic review

6. Dislocation (luxation)

• Persistent loss of contact between articular surfaces, with capsule and ligament tear
• Subluxation → partial loss of contact
• Most common → shoulder (anterior)
• Signs:
  • Pain
  • Deformity, abnormal limb position
  • Springy (elastic) fixation of the joint
  • Empty joint socket on palpation
  • Loss of function
• X-ray before and after reduction → exclude fracture
• Check distal pulses and nerves → axillary nerve in shoulder dislocation
• Treatment → early closed reduction under analgesia or anaesthesia, then immobilisation

7. Subcutaneous ruptures

Muscle and tendon

• Sudden contraction against resistance or direct blow
• Palpable gap, haematoma, loss of function
• Achilles tendon → Simmonds' (Thompson's) test positive: no plantar flexion when the calf is squeezed
• Treatment → immobilisation or surgical repair

Internal organs

• Spleen, liver, kidney, bowel, bladder
• Intra-abdominal bleeding → shock, Kehr's sign (left shoulder pain in splenic rupture)
• Hollow organ rupture → peritonitis
• Treatment → resuscitation, imaging, laparotomy or non-operative management

8. Concussion (commotio)

• Functional disturbance of an organ without visible structural damage
• Commotio cerebri → brief loss of consciousness, retrograde amnesia, headache, nausea
• Commotio cordis → blunt chest blow causing ventricular fibrillation
• Treatment → observation, rest

9. Compression and crush syndrome

• Crush syndrome (Bywaters' syndrome, traumatic toxicosis) → prolonged compression of large muscle masses, > 4–6 h
• Pathogenesis after release of compression:
  1. Muscle ischaemia and necrosis (rhabdomyolysis)
  2. Plasma loss into the limb → hypovolaemia, shock
  3. Release of potassium, myoglobin, acids → hyperkalaemia, acidosis
  4. Myoglobin in renal tubules → acute kidney injury
• Periods:
  1. Compression period
  2. Early period → first 1–3 days, shock
  3. Intermediate period → 3–12 days, acute kidney injury
  4. Late period → local healing, recovery
• Signs → swollen, tense, cold limb; dark (cola-coloured) urine; oliguria
• Treatment:
  • Intravenous fluids before release where possible
  • Target urine output > 200–300 mL/h
  • Correct hyperkalaemia
  • Fasciotomy for compartment syndrome
  • Haemodialysis for renal failure
  • Amputation for a non-viable limb