ICD-10-CM/PCS codes for musculoskeletal system include greater level of specificity

by Melanie A. Endicott, MBA/HCM, RHIA, CCS, CCS-P

In ICD-10-CM, diseases, disorders, and injuries from the musculoskeletal system are coded within chapter 13: Diseases of the Musculoskeletal System and Connective Tissue (M00–M99), and chapter 19: Injury, Poisoning, and Certain Other Consequences of External Causes (S00–T88). These chapters refer to both the muscles and bones (including diseases, fractures, and injuries) within this body system.

Documentation must include site and laterality specificity

The majority of codes in chapter 13 of the ICD-10-CM Manual have been expanded in some way, primarily due to the additional documentation that is required as most of the codes in chapter 13 include site and laterality designations. The site represents either the bone, muscle, or joint involved. There is an option for multiple sites when a diagnosis concerns more than one bone, muscle, or joint (e.g., code M08.89 [other juvenile arthritis, multiple sites]). When more than one bone, joint, or muscle is involved and there is not a multiple site option or code, coders must use multiple codes to indicate the sites involved. For example, report the following codes for osteomyelitis of cervical and lumbar vertebra:

  • M46.22(osteomyelitis of vertebra, cervical region)
  • M46.26 (osteomyelitis of vertebra, lumbar region)

All codes that have laterality requirements require you to identify whether the disease, injury, or diagnoses is located on the right or left region. For example, if a patient has a diagnosis of an abscess of bursa of the right shoulder, the appropriate code is M71.011 (abscess of bursa, right shoulder). In ICD-9-CM, coders would report this condition with code 727.89 (disorder of synovium/tendon/bursa), which lacks site and laterality specificity.

Take note of seventh character extensions

Some categories and subcategories in chapter 13 of ICD-10-CM require the use of the following seventh character extensions:

  • A: Initial encounter for 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 or fracture with malunion
  • S: Sequela

For all pathological and stress fractures, coders must assign one of these seventh characters. For example, category M80 identifies osteoporosis with current pathological fracture and also requires the appropriate seventh character extension. The medical record must provide the necessary specificity in the documentation to allow the coder to assign the correct seventh character extension, as this character is not optional.

If the physician documents “stress fracture of the tibia,” you would currently report ICD-9-CM code 733.93 (stress fracture of tibia/fibula). However for ICD-10-CM, the physician will also need to indicate the laterality (i.e., right or left) and whether this was the initial encounter, subsequent encounter (with routine healing, delayed healing, nonunion, or malunion), or a sequela. Therefore, the physician would need to document “initial encounter for stress fracture of the right tibia” for coders to report the appropriate ICD-10-CM code (M84.361A).

Be aware of increased specificity in fracture codes

Chapter 19 of ICD-10-CM contains codes for injuries, which are grouped by body part rather than by category. In other words, all injuries for a specific site (e.g., head and neck) are grouped together rather than groupings of all fractures or all open wounds.

Fracture codes in ICD-10-CM include much greater specificity, and indicate the following:

  • Type of fracture
  • Specific anatomical site
  • Whether the fracture is displaced
  • Laterality
  • Routine versus delayed healing, nonunions, and malunions

Laterality and identification of type of encounter (e.g., initial, subsequent, or sequela) are significant components of the code expansion in ICD-10-CM.

Chapter 19 codes also require coders to assign seventh character extensions to indicate:

  • 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

Assign extensions to indicate an initial encounter when the patient is receiving active treatment for the injury (e.g., surgical treatment or emergency department encounter).

Use extensions for subsequent encounter for those that occur after the patient has received active treatment of the injury and is receiving routine care for the injury during the healing or recovery phase (e.g., cast change or removal, medication adjustment, or other aftercare visits).

Assign extension S, sequela, for complications or conditions that arise as a direct result of an injury (e.g., scar formation after a burn). When using extension S, code both the injury that precipitated the sequela and the sequela itself. Sequence the specific type of sequela (e.g., scar) first, and follow this with the injury code (e.g., burn).

Consider the following example. A patient suffered a spiral fracture of the shaft of the right femur six months ago. The fracture has healed nicely, but the patient is still experiencing pain in the right thigh. For this scenario, report ICD-10-CM codes M79.651 (pain in right thigh) and S72.341S (displaced spiral fracture of shaft of right femur, sequel). Note: In ICD-10-CM, code fractures not indicated as displaced or nondisplaced as displaced.

Examine characters for ICD-10-PCS musculoskeletal codes

Every ICD-10-PCS code is seven characters long, and each character represents an aspect of the procedure. Coders will need to assign one of 34 values to each of the seven characters; ICD-10-PCS uses numbers 0 through 9 and all letters of the alphabet except I and O.

Character 1

There are 16 sections within ICD-10-PCS, the largest being the Medical and Surgical section, depicted with a 0 (zero) in the first character position. Note the following characters and what each identifies in an ICD-10-PCS code in the Medical and Surgical section:

  • Character 1: Section
  • Character 2: Body system
  • Character 3: Root operation
  • Character 4: Body part
  • Character 5: Approach
  • Character 6: Device
  • Character 7: Qualifier

Character 2

In ICD-10-PCS, the second character identifies the body system, which is the general physiological system or anatomic region involved. There are a total of 31 body systems in ICD-10-PCS. There are eleven body systems related to the musculoskeletal system:

Body system Character value
Muscles K
Tendons L
Bursae and ligaments M
Head and facial bones N
Upper bones P
Lower bones Q
Upper joints R
Lower joints S
Anatomical regions, general W
Anatomical regions, upper extremeties X
Anatomical regions, lower extremeties Y


Character 3

The third character of an ICD-10-PCS code identifies the root operation. There are 31 root operations in the Medical and Surgical section (e.g., bypass, drainage, excision, resection, and replacement), each with a distinct definition.

The root operations excision and resection are often confused. In ICD-10-PCS, excision is defined as cutting out or off, without replacement a portion of a body part, whereas resection is defined as cutting out or off, without replacement, all of a body part. These definitions look very similar, but are very different as they involve a portion versus all of a body part.

Coders must thoroughly understand each of these root operations and be able to correctly apply them to procedure coding. Physicians should not be expected to document the terms used in ICD-10-PCS code descriptions, nor should coders query the physician when the correlation between the documentation and the defined ICD-10-PCS terms is clear. For example, when a physician documents “partial resection,” coders can independently correlate this to the root operation of “excision” without querying for clarification.

Note that ICD-10-PCS guideline B3.1b states that components of a procedure specified in the root operation definition and explanation are not coded separately. Procedural steps necessary to reach the operative site and close the operative site are also not coded separately.

Therefore, a resection of a joint as part of a joint replacement procedure is included in the root operation definition of replacement and is not coded separately.

Character 4

The fourth character identifies the body part or specific anatomical site where the physician performed a procedure. There are up to 34 possible body part values for each body system.

Not every body part has its own distinct body part value. For example, there is one body system for the tendons, and since each body system has a maximum of 34 body parts, only 34 tendons can have their own distinct body part value.

ICD-10-PCS coding guideline B4.2 provides guidance on the selection of the body part value for procedures performed on a body part with no distinct value. The guideline states that when a specific branch of a body part does not have its own body part value, code the body part to the closest proximal branch that has a specific value. For example, there are 30 muscles that have a distinct body part value in the muscle body system. For a procedure performed on the extensor digitorum brevis muscle, code the foot muscle body part (right or left). Code a procedure performed on the flexor pollicis longus muscle to the lower arm and wrist muscle (right or left).

Character 5

There are seven different approach values in the Medical and Surgical section that indicate the technique the physician used to reach the site of the procedure. Approaches may be through the skin or mucous membranes, through an orifice, or external. Some examples of approaches for musculoskeletal procedures are:

  • Open (e.g., open reduction internal fixation of fracture)
  • Percutaneous (e.g., needle biopsy of muscle)
  • Percutaneous endoscopic (e.g., knee arthroscopy)
  • External (e.g., closed reduction of fracture)

Character 6

The sixth character specifies devices that remain after the physician completes the procedure. Materials that are incidental to a procedure (e.g., clips, sutures) are not considered devices and would use the device character Z to indicate “no device.” Device values fall into four categories:

  • Grafts and prostheses
  • Implants
  • Simple or mechanical appliances
  • Electronic appliances

Some of the devices used in musculoskeletal system procedures are internal and external fixation devices, bone growth stimulators, and drainage devices.

Character 7

The qualifier is specified in the seventh character. The qualifier contains unique values for individual procedures and varies depending on the previous values selected. Examples of qualifiers are type of transplant, second site for a bypass, or diagnostic excision (biopsy).

Start preparing for ICD-10-CM/PCS now

It is not too early for coders to begin preparing for ICD-10-CM/PCS. Reviewing the guidelines, studying the root operations, and practicing coding cases in ICD-10-CM and ICD-10-PCS are just a few of the ways that coders can familiarize themselves with the new code sets and be ready for the transition on October 1, 2013.

Editor’s note: Melanie Endicott, MBA/HCM, RHIA, CCS, CCS-P, is a professional practice manager at the American Health Information Management Association in Chicago. E-mail questions to Endicott at Melanie.endicott@ahima.org.

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