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A patient with a closed Colles fracture has the cast removed at week 4 and a new cast applied due to suboptimal alignment. The original fracture care code (25605) was billed at the initial visit. How is the second cast application reported?

Report 29075 (short arm cast) for the replacement cast within the global period

Report 25605 again

Bundle into the original fracture care; not separately reported

Report 99024 (no charge follow-up) only

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2026 Statistics

Key Facts: COSC Exam

150

Total Items

AAPC

5h 40m

Exam Time

AAPC

$299

AAPC Member Fee

AAPC

7th char

Required on Injury Codes

ICD-10-CM Chapter 19

The AAPC COSC consists of 150 MCQ items over 5h40m with 70% passing. Fee $299 AAPC member. Master fracture care principles (cast/splint included; restorative vs definitive once per fracture per encounter), joint replacement codes (27130 THA, 27447 TKA, 23472 TSA), arthroscopy compartment bundling rules, and ICD-10-CM 7th character convention.

Sample COSC Practice Questions

Try these sample questions to test your COSC exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which bone of the upper extremity articulates with both the scapula and the radius/ulna?

A.Clavicle

B.Humerus

C.Sternum

D.Scapula

Explanation: The humerus is the long bone of the upper arm. Proximally it articulates with the glenoid of the scapula at the glenohumeral joint, and distally it articulates with both the radius (capitellum) and the ulna (trochlea) at the elbow.

2Which structure within the knee joint provides primary resistance to anterior translation of the tibia on the femur?

A.Posterior cruciate ligament (PCL)

B.Medial collateral ligament (MCL)

C.Anterior cruciate ligament (ACL)

D.Lateral meniscus

Explanation: The ACL is the primary restraint preventing anterior translation of the tibia relative to the femur. ACL tears are commonly addressed via arthroscopic reconstruction (CPT 29888).

3A Colles' fracture refers to a fracture of which bone?

A.Distal ulna with palmar displacement

B.Distal radius with dorsal displacement

C.Scaphoid waist

D.Proximal humerus surgical neck

Explanation: A Colles' fracture is a transverse fracture of the distal radius with dorsal angulation/displacement of the distal fragment, classically from a fall on an outstretched hand. ICD-10-CM S52.5xxA is used for the initial encounter.

4Which carpal bone is most commonly fractured and known for a high rate of avascular necrosis when the proximal pole is involved?

A.Lunate

B.Triquetrum

C.Scaphoid

D.Pisiform

Explanation: The scaphoid is the most commonly fractured carpal bone. Its retrograde blood supply enters distally, so proximal pole fractures are at high risk for avascular necrosis and nonunion.

5Which structure of the shoulder is most commonly torn in a SLAP lesion?

A.Rotator cuff (supraspinatus)

B.Superior glenoid labrum from anterior to posterior

C.Acromioclavicular ligament

D.Coracoacromial ligament

Explanation: SLAP stands for Superior Labrum Anterior to Posterior. It is a tear of the superior glenoid labrum extending from anterior to posterior, often involving the biceps anchor. Arthroscopic SLAP repair is reported with CPT 29807.

6The medial and lateral menisci of the knee are composed primarily of what tissue type?

A.Hyaline cartilage

B.Fibrocartilage

C.Elastic cartilage

D.Dense regular connective tissue

Explanation: The menisci are C-shaped fibrocartilaginous discs that absorb load and improve joint congruity. Only the peripheral red zone has blood supply that supports surgical repair (29882-29883); the inner avascular zone typically requires meniscectomy (29880-29881).

7Adhesive capsulitis of the shoulder is described in ICD-10-CM by which code family?

A.M75.0-

B.M75.1-

C.M17.-

D.M23.-

Explanation: Adhesive capsulitis (frozen shoulder) is classified under M75.0- with laterality. M75.1- is reserved for rotator cuff syndrome/tear.

8The acetabulum is part of which bone?

A.Femur

B.Innominate (hip) bone

C.Sacrum

D.Tibia

Explanation: The acetabulum is the cup-shaped socket of the innominate (hip) bone formed by the fusion of the ilium, ischium, and pubis. It articulates with the femoral head to form the hip joint.

9Which rotator cuff muscle is most frequently torn?

A.Subscapularis

B.Infraspinatus

C.Teres minor

D.Supraspinatus

Explanation: The supraspinatus is the most commonly torn rotator cuff tendon, particularly in the critical zone near its insertion on the greater tuberosity due to its course beneath the acromion.

10Which cervical vertebra is known as the axis and contains the dens (odontoid process)?

A.C1

B.C2

C.C3

D.C7

Explanation: C2 is the axis. Its superior projection, the dens (odontoid process), articulates with C1 (the atlas) to permit rotation of the head.

About the COSC Exam

AAPC specialty credential for orthopaedic surgery coders. Validates expertise in fracture care coding (closed/open with/without manipulation; ORIF; restorative vs definitive — only one per encounter), joint replacement (THA, TKA, TSA with revisions), arthroscopy by joint (knee, shoulder, hip, wrist, ankle) with NCCI compartment-specific bundling, ICD-10-CM injury codes (S-codes with required 7th character A/D/G/K/P/S), and ortho-specific modifiers.

Questions

150 scored questions

Time Limit

5 hours 40 minutes

Passing Score

70%

Exam Fee

$299 AAPC member (AAPC)

COSC Exam Content Outline

15%

MSK Anatomy and Orthopaedic Pathology

Long bones, joints, ligaments/tendons, common ortho conditions

20%

CPT Fracture Care

Closed/open with/without manipulation; ORIF; cast/splint included

20%

CPT Joint Replacement and Reconstructive

THA 27130, TKA 27447, TSA 23472, revisions, hemiarthroplasty

15%

CPT Arthroscopy

Knee 29870-29889, shoulder 29805-29828, hip 29862-29863, wrist/ankle

15%

ICD-10-CM Musculoskeletal and Injury

M-codes (osteoarthritis, RC syndrome, meniscal); S-codes with 7th character A/D/G/K/P/S

15%

Modifiers, Casting/Splinting, Compliance

50, 51, 58, 78, 79, LT/RT, F1-FA digit, T1-TA digit, 80 assistant; 29000-29799 cast/splint

How to Pass the COSC Exam

What You Need to Know

Passing score: 70%
Exam length: 150 questions
Time limit: 5 hours 40 minutes
Exam fee: $299 AAPC member

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

COSC Study Tips from Top Performers

1Master 7th character convention: A initial encounter (active tx), D subsequent routine healing, G delayed, K nonunion, P malunion, S sequela. Required on S-codes

2Know fracture care bundle: includes initial cast/splint + first E/M; replacement cast during global IS separately billable; cannot bill 2 fracture care methods same fracture

3Memorize joint replacement codes: 27130 THA, 27132 conversion to THA, 27125 hemi; 27447 TKA, 27446 unicompartmental, 27486/27487 revision (1 vs both); 23472 TSA, 23473 revision

4Understand knee scope bundling: same compartment debridement bundles with meniscectomy; different compartments use modifier 59. HCPCS G0289 for separate-compartment chondroplasty (Medicare)

Frequently Asked Questions

What does the 7th character mean in ICD-10-CM injury codes?

Chapter 19 injury codes (S00-T88) require a 7th character to indicate encounter type: A = initial encounter (active treatment of injury), D = subsequent encounter (routine healing), G = subsequent with delayed healing, K = subsequent with nonunion, P = subsequent with malunion, S = sequela (late effect from prior injury). For open fracture S-codes, additional Gustilo-Anderson classification characters specify type.

How is fracture care coded?

Each fracture gets ONE definitive code per encounter. Choose: closed without manipulation, closed with manipulation, open treatment with internal fixation (ORIF), or percutaneous skeletal fixation. The fracture care code INCLUDES the initial cast/splint application + first global E/M. Replacement cast during the global period IS separately billable (29000-29799). Cannot bill restorative + definitive treatment of same fracture same encounter.

What's the rule for knee arthroscopy bundling?

Knee arthroscopy compartments: medial, lateral, patellofemoral. Within the SAME compartment, debridement (29877) is bundled when you bill meniscectomy of that compartment (29880/29881). Across DIFFERENT compartments, separately reportable with modifier 59 (e.g., medial meniscectomy + lateral chondroplasty). HCPCS G0289 is used for chondroplasty in a SEPARATE compartment from a meniscectomy (Medicare-specific).