2027 ICD-10-CM Diagnosis Code S02.101BFracture of base of skull, right side, initial encounter for open fracture
ICD-10-CM Codes›S00–T88›S00-S09›S02
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 399
- 7th Character B — Initial Encounter for Open Fracture
- Not Chronic
S02.101B is a billable ICD-10-CM diagnosis code for fracture of base of skull, right side, initial encounter for open fracture. The 7th character B means initial encounter for open fracture. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 82 through 87, 963 through 965. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 383 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fracture of head and neck, initial encounter.
For Medicare Advantage risk adjustment, S02.101B maps to CMS-HCC Category 399 (Major Head Injury without Loss of Consciousness) under the V28 model, adding a risk factor of about 0.199 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
S02.101B maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Coding GuidelinesGuidance
The principles of multiple coding of injuries should be followed in coding fractures. Fractures of specified sites are coded individually by site, to the level of detail furnished by medical record content.
A fracture not indicated as open or closed should be coded to closed. A fracture not indicated whether displaced or not displaced should be coded to displaced.
Initial vs. Subsequent Encounter for Fractures
Traumatic fractures are coded using the appropriate 7th character for initial encounter (A, B, C) while the patient is receiving active treatment for the fracture. The appropriate 7th character for initial encounter should also be assigned for a patient who delayed seeking treatment for the fracture or nonunion.
Fractures are coded using the appropriate 7th character for subsequent care for encounters after the patient has completed active treatment of the fracture and is receiving routine care for the fracture during the healing or recovery phase.
Care for complications of surgical treatment for fracture repairs during the healing or recovery phase should be coded with the appropriate complication codes.
Care of complications of fractures, such as malunion and nonunion, should be reported with the appropriate 7th character for subsequent care with nonunion (K, M, N) or subsequent care with malunion (P, Q, R).
The open fracture designations in the assignment of the 7th character for fractures of the forearm, femur and lower leg, including ankle are based on the Gustilo open fracture classification. When the Gustilo classification type is not specified for an open fracture, the 7th character for open fracture type I or II should be assigned (B, E, H, M, Q).
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to S02.101B: its own notes plus those printed at S02.1, S02, block S00-S09, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- injuries of ear
- injuries of eye
- injuries of face [any part]
- injuries of gum
- injuries of jaw
- injuries of oral cavity
- injuries of palate
- injuries of periocular area
- injuries of scalp
- injuries of temporomandibular joint area
- injuries of tongue
- injuries of tooth
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- burns and corrosions (T20-T32)
- effects of foreign body in ear (T16)
- effects of foreign body in larynx (T17.3)
- effects of foreign body in mouth NOS (T18.0)
- effects of foreign body in nose (T17.0-T17.1)
- effects of foreign body in pharynx (T17.2)
- effects of foreign body on external eye (T15.-)
- frostbite (T33-T34)
- insect bite or sting, venomous (T63.4)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
- any associated intracranial injury (S06.-)
- for any associated infection
Notes
General instructions on how these codes are used.
- A fracture not indicated as open or closed should be coded to closed
- 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
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category S02
- Ainitial encounter for closed fracture
- Binitial encounter for open fracture this code
- Dsubsequent encounter for fracture with routine healing
- Gsubsequent encounter for fracture with delayed healing
- Ksubsequent encounter for fracture with nonunion
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name S02.101B, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming S02.101B: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 2
These codes carry an Excludes2 note naming S02.101B: its condition is not part of those codes, and both may be reported when the patient has both.
Code First 1
These codes say to code first a condition named in the note, and S02.101B is one of the conditions named.
Use Additional Code 1
These codes say to use an additional code from the note, and S02.101B is one of the codes named.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Fractures
A fracture is a break in a bone. Fractures are usually caused by injuries. Since they can sometimes be serious, it's important to get medical care right away if you think you have a fracture.
The full article covers:
- What is a fracture?
- What are the different types of fractures?
- What causes fractures?
- What are the symptoms of a fracture?
- How are fractures diagnosed?
- What are the treatments for fractures?
- Can fractures be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S02.101B to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code History & ChangesHistory
Replacement S02.101B replaces the following previously assigned code(s):
- S02.10XB - Unsp fracture of base of skull, init for opn fx
Questions About S02.101BOverview
Is S02.101B (Fracture of base of skull, right side) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report fracture of base of skull, right side, initial encounter for open fracture on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character B in S02.101B mean?
The final character B means initial encounter for open fracture, in this case for the fracture of base of skull, right side. It comes from the 7th character list in the CMS Tabular List for this category.
What MS-DRG does S02.101B group to?
When fracture of base of skull, right side, initial encounter for open fracture is the principal diagnosis on an inpatient stay, it groups to MS-DRG 85, 964, 83, 84, 965, 82, 86, 87, 963, with relative weights from 0.9219 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.
Is S02.101B a CC or MCC?
CMS lists S02.101B as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 383 closely related codes in its exclusion list.
What is the ICD-9 equivalent of S02.101B?
Under the General Equivalence Mappings, fracture of base of skull, right side, initial encounter for open fracture converts to ICD-9-CM 801.50 (open skull base fracture). The mapping is approximate, so confirm the match fits the documentation.
What HCC is S02.101B?
S02.101B (fracture of base of skull, right side, initial encounter for open fracture) maps to CMS-HCC Category 399 (Major Head Injury without Loss of Consciousness), commonly written as HCC 399, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 167 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does S02.101B risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, S02.101B adds a risk adjustment factor of about 0.199 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.052 to 0.349 depending on the payment segment). A more severe related category (HCC 397 and HCC 398) supersedes it when both are reported. See the full factor table on the HCC 399 category page.
