COSC cheat sheet

Anatomic planes: sagittal divides left and right; coronal divides anterior and posterior; axial or transverse divides superior and inferior.

Valgus describes the distal segment deviating away from the midline; varus describes the distal segment deviating toward the midline.

Proximal means closer to the trunk; distal means farther from the trunk; medial and lateral describe position relative to the midline.

A complete operative report contains preoperative and postoperative diagnoses, procedure or procedures, surgeon and assistants, anesthesia, indication, findings, technique, implants, estimated blood loss, specimens, and complications.

The word open in open reduction describes surgical exposure; a closed fracture can still require open reduction when an incision is used.

Code from the documented procedure actually performed, not from the report title or the originally scheduled procedure.

Laterality, right or left, and the specific anatomic site must be documented for paired structures; missing laterality prevents accurate CPT and ICD-10-CM assignment.

Implant documentation includes manufacturer, model, size, lot or serial number, and location; these details support arthroplasty and revision coding.

Medical necessity documentation links the procedure to a diagnosed condition, failed conservative care, functional deficit, or injury mechanism.

Closed fracture treatment codes include the initial closed reduction and cast or splint application by the same physician, plus routine follow-up during the global period.

Do not report a separate cast application code with a fracture-care code when the cast is part of the same closed treatment.

Open fracture treatment codes include the surgical approach, open reduction, and internal fixation documented; do not add separate hardware insertion codes.

Percutaneous fixation is selected when pins or screws are placed through small incisions without direct fracture visualization.

External fixation application is reported with 20690 for a uniplane system and 20692 for a multiplane system; removal under anesthesia may be reported separately with 20694.

Dislocation reduction codes are site-specific; closed reduction is coded separately from open reduction, which requires documented surgical exposure.

When multiple fractures are treated at the same site, code the most complex procedure and check NCCI edits before reporting additional fracture codes.

Traumatic tendon or muscle laceration repair is coded by site and complexity; it is not automatically included in a fracture code.

Code each distinct fracture site when separate incisions and procedures are documented, subject to NCCI bundling rules.

Surgical arthroscopy includes diagnostic arthroscopy of the same joint; do not report a separate diagnostic arthroscopy code.

Knee arthroscopy: 29870 is diagnostic or debridement; 29880 is medial and lateral meniscectomy; 29881 is single-compartment meniscectomy.

Meniscal repair, 29882 or 29883, is distinct from meniscectomy; documentation must state repair versus excision.

Arthroscopic ACL reconstruction, 29888, includes graft harvest, notchplasty, and fixation; concomitant meniscectomy may be separately coded when distinct.

Shoulder arthroscopy codes are procedure-specific; acromioplasty, 29826, has NCCI bundling relationships with many shoulder procedures.

Arthroscopic capsular release and lysis of adhesions are separately coded only when documented as distinct procedures, not routine portal work.

Arthroscopy documentation should list portals, compartments examined, findings, procedures, implants, tourniquet time, and any open conversion.

When an arthroscopic procedure converts to open, report the open procedure; do not separately report the arthroscopy unless a distinct arthroscopic procedure was completed.

Total knee arthroplasty is 27447; unicompartmental knee arthroplasty is 27446; patellofemoral arthroplasty is 27438.

Total hip arthroplasty is 27130; revision hip and knee codes generally include removal of the existing prosthesis and insertion of new components.

Arthroplasty codes include routine arthrotomy, capsulectomy, synovectomy, osteophyte removal, and implant insertion; these are not separately coded.

Spinal fusion is coded by approach, region, and number of motion segments fused; instrumentation add-on codes are reported per additional segment.

Autograft harvest for spine fusion: 20936 local, 20937 tricortical iliac crest; allograft: 20930 morselized, 20931 structural.

Vertebroplasty and kyphoplasty are reported by vertebral level and approach; documentation must identify the level and whether balloon kyphoplasty was performed.

A spinal fusion level is a motion segment between two adjacent vertebrae; count each interspace, not each vertebral body.

Major joint arthroplasty has a 90-day global period; unrelated E/M services during that period require modifier 24.

Injury codes in Chapter 19 require a seventh character: A initial encounter, D subsequent encounter, S sequela.

Fracture coding requires site, laterality, type, displaced or nondisplaced status, open or closed status, and healing status when applicable.

External cause codes from Chapter 20 are secondary diagnoses; they are never the principal diagnosis for an injury.

Osteoarthritis codes are site-specific and laterality-specific; use bilateral codes only when bilateral disease is documented.

Pathologic fracture coding requires the underlying disease and the fracture site; do not code a traumatic fracture when the documentation says pathologic.

Periprosthetic fracture is coded with M97.- by site; document the joint, implant, and displacement.

History of disease Z codes are used for resolved conditions and are not substitutes for active condition codes.

Complication codes such as T84-, M97-, and T81- require documentation of the complication type and the affected device or joint.

Do not code symptoms such as pain when the pain is integral to a confirmed diagnosis; code the diagnosis instead.

Modifier 25: significant, separately identifiable E/M service on the same day as a procedure by the same physician.

Modifier 24: unrelated E/M service during a postoperative global period; documentation must establish the service is unrelated to the surgery.

Modifier 57: E/M service that resulted in the initial decision to perform surgery.

Modifier 50: bilateral procedure; modifier 51: multiple procedures; modifier 59: distinct procedural service.

X{E,S,P,U} are more specific substitutes for modifier 59: XE separate encounter, XS separate structure, XP separate practitioner, XU unusual non-overlapping service.

Modifier 58: staged or related procedure during the postoperative period; modifier 78: return to the operating room for a related complication; modifier 79: unrelated procedure during the postoperative period.

Add-on codes are never reported with modifier 51 and must be linked to the primary procedure.

The global surgical package includes routine preoperative, intraoperative, and postoperative care; implants and distinct services may be separately reported when rules allow.

NCCI procedure-to-procedure edits: the column one code is payable; the column two code is denied unless a valid modifier and documentation support a distinct service.

Medically Unlikely Edits set maximum units per patient per date of service for a code; exceeding the MUE requires exceptional documentation.

Modifier 59 or X{E,S,P,U} should be used only when the services are distinct and the documentation supports separate sites, encounters, or structures.

Medical necessity requires the service to be reasonable and necessary for the diagnosis or treatment; payer LCD and NCD policies may define covered indications.

Documentation must support the level of service, procedure, diagnosis, laterality, and medical necessity; incomplete notes are a common audit risk.

Incident-to billing requires the supervising physician to be present and the service to be part of the physician's plan of care in the office setting.

High-risk audit areas include arthroplasty, spine fusion, arthroscopy, and trauma; document implants, levels, compartments, and laterality.

Payer rules vary by Medicare, Medicaid, workers' compensation, and commercial plans; verify coverage and modifier policies before submission.