ICD-10-CM injury coding: Turn to coding guidelines for proper code assignment

by Ann Zeisset, RHIT, CCS, CCS-P

ICD-10-CM provides greater specificity in coding injuries than ICD-9-CM. While many of the ICD-10-CM’s coding guidelines for injuries remain the same as ICD-9-CM, the new coding system does include new features, such as seventh character extensions.

Injury, poisoning, and certain other consequences of external causes
Chapter 19, “Injury, Poisoning, and Certain Other Consequences of External Causes (S00–T88),” in the ICD-10-CM Coding Manual encompasses two alpha characters, S and T. The S section provides codes for the various types of injuries related to single body regions. The T section covers injuries to unspecified body regions as well as poisonings and certain other consequences of external causes.

The coding manual provides the following guidance at the beginning of the chapter, “Use secondary code(s) from Chapter 20, External Causes of Morbidity, to indicate cause of injury.” Codes within the T section that include the external cause do not require an additional external cause code.

In ICD-10-CM, injuries are grouped by body part rather than by category, so all injuries of a specific site (such as head and neck) are grouped together rather than groupings of all fractures or all open wounds.

Categories grouped by injury in ICD-9-CM such as fractures (800–829), dislocations (830–839), andsprains and strains (840–848) are sorted in ICD-10-CM by site. For example, head injuries are found in code series S00–S09, neck injuries in code series S10–S19, and injuries to the thorax in code series S20–S29.

Injury extensions
Most categories in chapter 19 require seventh character extensions for each applicable code. Most categories (with the exception of fractures) have three options:

  • A, Initial encounter
  • D, Subsequent encounter
  • S, Sequela

Use the initial encounter extension for patients actively receiving treatment for the injury (e.g., surgical treatment, emergency department encounter, and evaluation and treatment by a new physician). Report the subsequent encounter extension for patients receiving routine care for the injury during the healing or recovery phase (e.g., cast change or removal, removal of external of internal fixation device, medication adjustment, other aftercare and follow-up visits following injury treatment).

Use extension S, sequela, for complications or conditions that arise as a direct result of an injury, such as scar formation after a burn. The scars are sequela of the burn. When reporting extension S, use both the injury code that precipitated the sequela and the code for the sequela itself. But add the S only to the injury code, not the sequela code.

The S extension identifies the injury responsible for the sequela. The specific type of sequela (e.g., scar) is sequenced first, followed by the injury code. Sequela is the new terminology in ICD-10-CM for late effects in ICD-9-CM, and using the sequela extension replaces the late effects categories (905–909) in  CD-9-CM.

Fracture coding
ICD-10-CM fracture codes provide greater specificity than ICD-9-CM. For example, ICD-10-CM fracture codes can indicate the fracture type (e.g., greenstick, transverse, oblique, spiral, comminuted, segmental), specific anatomical site, whether the fracture is displaced, laterality, routine versus delayed healing, nonunions, and malunions. Laterality and type of encounter (i.e., initial, subsequent, sequela) are significant components of the code expansion.

To provide additional specificity, the fracture extensions are expanded to include:

  • A, Initial encounter for closed fracture
  • B, Initial encounter for open fracture
  • D, Subsequent encounter for fracture with routine healing
  • G, Subsequent encounter for fracture with delayed healing
  • K, Subsequent encounter for fracture with nonunion
  • P, Subsequent encounter for fracture with malunion
  • S, Sequela

Some fracture categories provide seventh character extensions to designate the specific type of open fracture. These designations are based on the Gustilo-Anderson open fracture classification and apply to categories S52 (Fracture of forearm), S72 (Fracture of femur), and S82 (Fracture of lower leg).

The Gustilo open fracture classification for extremities classifies open fractures into three major categories (types) depending on the mechanism of the injury, soft tissue damage, and degree of skeletal involvement. The classes are I, II, and III, with the third class further subdivided into A, B, and C.

The Gustilo classification is used to identify the severity of the soft tissue damage. Fracture healing, infection, and amputation rates correlate with the degree of soft tissue injury by Gustilo and helps determine the prognosis.

The extensions available for these open fractures are:

  • B, Initial encounter for open fracture type I or II
  • C, Initial encounter for open fracture type IIIA, IIIB, or IIIC
  • E, Subsequent encounter for open fracture type I or II with routine healing
  • F, Subsequent encounter for open fracture type IIIA, IIIB, or IIIC with routine healing
  • H, Subsequent encounter for open fracture type I or II with delayed healing
  • J, Subsequent encounter for open fracture type IIIA, IIIB, or IIIC with delayed healing
  • M, Subsequent encounter for open fracture type I or II with nonunion
  • N, Subsequent encounter for open fracture type IIIA, IIIB, or IIIC with nonunion
  • Q, Subsequent encounter for open fracture type I or II with malunion
  • R, Subsequent encounter for open fracture type IIIA, IIIB, or IIIC with malunion

In ICD-10-CM, when a physician does not indicate whether a fracture is displaced or nondisplaced, coders should code it as displaced. Similarly, coders should report a fracture not designated as open or closed as closed.

Coding aftercare
Do not use the aftercare Z codes for injury aftercare. For aftercare of an injury, coders should assign the acute injury code with the appropriate seventh character "D" for subsequent encounter. This change is significant for post-acute settings that provide subsequent care for injuries.

Currently V codes report physical therapy and other aftercare of fractures and injuries, such as removing casts and dressings.

Consider the following example. A patient has a displaced, closed fracture of the greater trochanter of the right femur (S72.111). Assign the following codes for this case:

  • Patient seen in the emergency room, admitted, and surgery performed: S72.111A, Initial encounter for closed fracture
  • Admitted to long-term care for rehabilitation after hip replacement: S72.111D, Subsequent encounter for closed fracture with routine healing
  • Discharged from long-term care and home health to see for continued physical therapy: S72.111D, Subsequent encounter for closed fracture with routine healing
  • Radiology department visit for X-ray: S72.111D, Subsequent encounter for closed fracture with routine healing

Should the patient visit the physician office for follow-up visit, report code S72.111D (subsequent encounter for closed fracture with routine healing).

Poisoning, adverse effects, and drug underdosing
Codes in categories T36–T65 are combination codes that include substances related to adverse effects, poisonings, toxic effects, and underdosing, as well as the external cause. ICD-10-CM doesn’t require any additional external cause codes for poisonings, toxic effects, adverse effects, and underdosing.

Sequence first a code from categories T36–T65, followed by the code that specifies the nature of the adverse effect, poisoning, or toxic effect. However, this sequencing instruction does not apply to underdosing codes (i.e., with a fifth or sixth character “6” you would code T36.0x6).

Assign an adverse effect code (e.g., T36.0x5-) when the drug was correctly prescribed and properly administered. Use additional codes for all manifestations of adverse effects. Examples of manifestations are tachycardia, delirium, gastrointestinal hemorrhaging, vomiting, hypokalemia, hepatitis, kidney failure, or respiratory failure.

When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), assign the appropriate code from categories T36–T50. Poisoning codes have an associated intent: accidental, intentional self-harm, assault, and undetermined. Use additional code(s) for all manifestations of poisonings.

When no intent of poisoning is indicated, code to accidental. Only use “undetermined intent” when a physician specifically documents he or she cannot determine the intent of the poisoning.
ICD-10-CM includes a table of drugs and chemicals; however, the columns have been restructured to group all poisoning columns together, followed by adverse effect and underdosing. Refer to the tabular list rather than code from the table of drugs and chemicals.

Coding professionals may assign as many codes as necessary to describe all drugs and medicinal or biological substances involved. If the physician reports two or more, code each individually unless the combination code is listed in the table of drugs and chemicals.
Underdosing is a new concept in ICD-10-CM. It refers to taking less of a medication than prescribed by a

provider or manufacturer instruction. For underdosing, assign the code from categories T36–T50. Never assign underdosing codes as principal or first-listed codes.

Code the medical condition if a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in dose. Use codes for noncompliance (Z91.12-, and Z91.13-) or complication of care (Y63.61, and Y63.8–Y63.9) with an underdosing code to indicate intent, if known.

Coding burns and corrosions
ICD-10-CM distinguishes between burns and corrosions though the guidelines are the same for both. Burn codes apply to thermal burns (except sunburns) that come from a heat source (e.g., fire or hot appliance) and include electricity and radiation burns. Corrosions are chemical burns.

Current burns (T20–T25) are classified by depth, extent, and agent (X code). Depth classifications include first degree (erythema), second degree (blistering), and third degree (full-thickness involvement). Burns of the eye and internal organs (T26–T28) are classified by site.

For any documented infected burn site, use an additional code for any infection. When coding burns, assign separate codes for each burn site. Category T30, Burn and corrosion, body region unspecified, is extremely vague and should be used rarely.

Ann Zeisset is a professional practice manager at the American Health Information Management Association. E-mail your questions to Senior Managing Editor Michelle A. Leppert, CPC-A, at mleppert@hcpro.com

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