Rigor MortisBy: Imtiaz ur Rehman4th Year MBBSKhyber Medical College Peshawar

Definition

• Rigor Mortis is normal muscle contraction that occurs after death and is fixed due to lack of ATP

Mechanism of Rigor Mortis

Characteristics • Occurs in both involuntary and voluntary muscles• Appears first in short muscles and then in larger muscles• It has nothing to do with nerve supply as it can occur in paralyzed limbs as well• Muscle become brittle and tearable• Heart will be in permanent contracted state and will contain very little blood• Skin will have granular appearance due to contraction of Erector Pilae muscles. This

condition is called Cutis Ansernia or goose skin• Discharge of semen due to involvement of seminal vesicles• Iris will contract abnormally• Post mortem delivery

Progression of Rigor Mortis

Eyelid 3-4 hrs

Face4-5 hrs

Neck & Trunk5-7 hrs

Upper Limb

7-9 hrs

Lower Limb

9-11 hrs

Small Muscles

of fingers & toes

11-12 hrs

Static phase13-24 hrs

Passing off

phase25-48 hrs

Proximodistal Progression

(Nysten’s Law)

Testing of Rigor Mortis• Attempting to open eyelid• Depressing the jaw• Flexing neck and other joints

Factors effecting Rigor Mortis

• Temperature• Age• Body structure • Nutritional status• Muscular activity• Mode of death

Medicolegal importance

• Diagnosis of death• Determining postmortem interval• Determining manner of death• Position of body at the time of death

• Postmortem• Involves both voluntary as well as

involuntary muscles• Muscles of whole body are affected• Has a specific pattern of development

• Occurs in all deaths

• Moderate force is required to break the rigidity

• Has no relation to establishment of manner of death

• Antemortem• Involves only voluntary muscles• Only a group of muscles is effected• Develops instantaneously, being

associated with last action before death

• Occurs in sudden death and emotional stress

• Very hard to break• Helps to establish manner of death

• Rigor Mortis • Cadaveric Spasm

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