Published 11/1/2014
Margaret M. Maley, BSN, MS

When “7” Is Not a Lucky Number

Using the 7th character extension in ICD-10-CM for orthopaedic injuries

The 7th character extension represents a major distinction between the International Classification of Diseases, Ninth Edition (ICD-9) and the International Classification of Diseases, Tenth Edition (ICD-10). A clear understanding of the 7th character is imperative due to its extensive use in orthopaedics.

The 7th character extension is found predominately in the following chapters:

  • Chapter 13, Musculoskeletal, describing “phase of treatment”
  • Chapter 19, Injury (Poisonings and Other Consequences of External Causes), describing the “phase of treatment” in addition to giving important details in the case of fractures, such as whether the fracture is open or closed
  • Chapter 20, External Causes, addressing the episode of care; however, codes from this chapter are not required for proper coding (See “Hit by an Alligator or Crushed by a Crocodile,” AAOS Now, June 2014.)
  • Chapter 15, Pregnancy and Childbirth, providing information about the fetus but not used by orthopaedic surgeons

This article will focus on the episode of care or phase of treatment as it relates to acute injuries (but not fractures) in Chapter 19.

Chapter organization
Orthopaedic surgeons should first realize that the organization of Chapter 19 is completely transformed in ICD-10. In ICD-9, the injury chapter was organized first by type of injury and then by body location. In ICD-10, the injury chapter is organized first by body area (represented by ICD-10’s 2nd character) and within each body location, by type of injury.
Table 1 shows the general body areas in ICD-10, Chapter 19. (Each of these represents a different 3rd character.)

For each anatomic location shown, the following types of injuries are listed:

  • Superficial injury
  • Open wound
  • Fracture
  • Dislocations and subluxations/sprains of joints or ligaments
  • Nerve injury (motor and sensory nerves by name)
  • Blood vessel injury (arteries and veins by name); laceration and other
  • Muscle or tendon injury (tendon, fascia, and muscle by name)
  • Crush
  • Amputation traumatic
  • Other and unspecified injuries

For every injury listed in Chapter 19, an alpha 7th character extension is required. The 7th character describes the “phase of treatment.” Options for the 7th characters for injuries (other than fractures) are as follows:

A—initial encounter

D—subsequent encounter


Initial encounter
A, as a 7th character extension for an injury (not a fracture), is described by the words “initial encounter” and is used for every episode of care in which the patient receives active treatment for the injury. It can be used many times by the same provider, as well as by all practitioners providing active treatment.

For example, using ICD-10-CM, coding for a traumatic rupture of the Achilles tendon of the right ankle (S86.011, Strain of right Achilles tendon) would be reported as follows:

  • Emergency department (ED) visit—ED physician would report the diagnosis code S86.011A, Strain of right Achilles tendon, initial encounter.
  • If the patient is sent to radiology, the diagnosis code used for the radiographs is also S86.011A, Strain of right Achilles tendon, initial encounter.
  • Ankle is splinted; patient is given crutches and told to follow up with the orthopaedic surgeon. Patient sees the orthopaedic surgeon 3 days later. They discuss treatment options and plan surgery. Orthopaedic surgeon reports the office visit using S86.011A, Strain of right Achilles tendon, initial encounter.
  • Patient undergoes surgery later that week; the diagnosis used for the surgical procedure is still S86.011A, Strain of right Achilles tendon, initial encounter.

All of these encounters are considered active treatment and have an “A” as the 7th character extension.

Subsequent encounters
D as a 7th character extension is defined by the short descriptor as a “subsequent encounter” and is used for encounters after the patient has received active treatment for the condition. It is used for every encounter in which the patient receives routine care for the condition during the healing or recovery phase. It would be used in the following situations:

  • suture removal
  • medication adjustment
  • physical therapy after the active treatment of the injury
  • follow-up visits after the active treatment of the injury

Continuing the previous example, after surgery on the Achilles tendon, when the patient returns to have the stitches removed, the splint changed, the pain medication adjusted, or a walking boot fitted, all visits would be reported using the same code to describe the right Achilles tendon strain, but with a “D” in the 7th position, S86.011D.

Although the words “initial” and “subsequent” encounter are used in the short descriptor for the 7th character, these extensions have nothing to do with new and established patient visits described in CPT (Current Procedural Terminology). An established patient visit could be reported when the diagnosis has an A in the 7th position describing active treatment even though ICD-10 calls this an “initial encounter.” In ICD-10, the 7th character describes the phase of treatment—active treatment versus routine healing.

S in the 7th position indicates sequela and is used to indicate that a residual problem continues after the active phase of an injury or illness has resolved. There is no timeline on when a sequela code can be used; some “late effects” occur early, like weakness after a stroke, while others occur months or years after an injury.

Reporting sequela conventionally requires the use of two codes. The result of the injury, or the reason the patient is currently being treated, is listed as the first diagnosis code (contracture), and the cause or initial/original injury (fracture) is sequenced as the second code with the “S” extension. However, the “S” extension is not used to report surgical complications; it is similar to the “late effects” codes in ICD-9.

For example, a hand surgeon conducts an initial evaluation for Volkmann’s contracture some months after the patient sustained a supracondylar fracture of the right humerus. Coding this visit would be as follows:

  • T79.6XXA—Traumatic ischemia of muscle, initial encounter
  • S42.421S—Displaced comminuted supracondylar fracture without intercondylar fracture of right humerus, sequela

Because the code for the Volkmann’s contracture (T79.6) is only 4 characters long, “X” placeholders must be used to keep the 7th character extension in the correct position. The “A” character is used because it is the initial evaluation of the contracture, constituting active treatment.

The ICD-10 code for the cause of the contracture (the supracondylar fracture) is listed second with the “S” extension in the 7th position and without any placeholders.

What to remember
It’s important to remember the following five things about the 7th character extension in ICD-10 as it relates to injuries (not fractures):

  • It is not optional. If the code requires a 7th character, it must be assigned to be a valid code.
  • There are only three options (A, D, or S) for the 7th character when the code represents an injury that is not a fracture.
  • It must always be in the 7th position. The “X” placeholder must be inserted if the diagnosis code assigned is less than six characters long.

The 7th character extensions have nothing to do with the CPT codes for new and established patient visits.

When coding sequelae, two codes are required, and the “original” diagnosis code representing the cause is sequenced second with the “S” extension.

The 7th character extension for traumatic and fragility fractures is more complicated and will be addressed in future articles. Based on this information, orthopaedic surgeons who see patients with injuries should begin now to consider which 7th character should be assigned when ICD-10 rolls out on Oct. 1, 2015.

Margaret M. Maley, BSN, MS, is a senior consultant with KarenZupko & Associates, Inc., focusing on CPT and ICD-10 coding education for orthopaedic practices. This article has been reviewed by members of the AAOS Coding, Coverage, and Reimbursement Committee.