Bilateral procedure

Orthopedic scenarios

Concrete situations in orthopedic practice that warrant modifier 50.

Source · Editorial brief grounded in AAOS coding guidance and cited references ↓

• Bilateral total knee arthroplasty (TKA, CPT 27447): Patient undergoes simultaneous bilateral TKA. Bill 27447-50, one line, one unit. Medicare pays 150% of the 27447 unilateral allowable. If a manipulation under anesthesia is also performed that day, apply the 150% bilateral adjustment to 27447-50 first, then reduce the additional procedure per multiple-surgery rules.
• Bilateral knee arthroscopy with partial medial meniscectomy (CPT 29881): Surgeon scopes both knees in the same session. Bill 29881-50, one line, one unit of service. Confirm bilateral indicator = 1 in the MPFSDB before submission to ensure the 150% payment adjustment applies.
• Bilateral carpal tunnel release (CPT 64721): Open release performed on both wrists during one operative session. Bill 64721-50, one line, one unit. Because 64721 has a bilateral indicator of 1, payment is 150% of the single-wrist allowed amount.
• Bilateral ORIF of distal radius fractures (CPT 25600 or 25605 depending on manipulation): Both wrists fractured and reduced in the same session. Bill the appropriate ORIF code with modifier 50, one unit, confirming the bilateral indicator prior to submission—do not list separate LT and RT lines on the professional claim.
• Bilateral hip arthroscopy for femoroacetabular impingement (CPT 29914 or 29915): If the surgeon performs labral repair or cam resection on both hips the same day, append modifier 50 to the primary arthroscopy code, one line, one unit. Document medical necessity for simultaneous bilateral intervention explicitly in the operative note, as payers scrutinize bilateral hip arthroscopy claims closely.
• Bilateral shoulder subacromial injection (CPT 20610): Both shoulder joints injected the same visit. Bill 20610-50, one line, one unit. The bilateral indicator for 20610 is 1, so the 150% adjustment applies.

Common mistakes

Where coders most often go wrong with modifier 50.

Source · Editorial brief grounded in CMS NCCI Policy Manual and cited references ↓

• Appending modifier 50 to a code whose descriptor already reads 'bilateral' or 'unilateral or bilateral' (e.g., 31231 nasal endoscopy)—the RVUs are pre-built for both sides, and adding -50 causes the claim to be priced at the lower of total charges or 100% of the single-code fee schedule.
• Entering 2 in the units field on a professional (CMS-1500) claim instead of 1 unit with modifier 50—Medicare requires one unit on one line for professional billing; two units in the units field triggers MUE denial because many bilateral surgery codes carry an MUE value of 1.
• Billing modifier 50 in an ASC setting—ASCs are explicitly excluded from modifier 50 reporting under Medicare NCCI policy; ASC staff must use two separate claim lines with LT and RT modifiers or a single line with 2 units per their payer's ASC-specific bilateral rules.
• Using modifier 50 on a code with bilateral indicator 0 (e.g., a chest X-ray or a procedure that is not a paired anatomical structure)—the 150% adjustment does not apply, and payment defaults to the lower of total actual charges or 100% of the single-code fee schedule amount.
• Stacking modifier 50 with LT or RT on the same line—modifier 50 already communicates bilateral performance; adding a laterality modifier creates conflicting information and may cause the claim to reject or be manually reviewed.
• Failing to apply the bilateral pricing adjustment before calculating multiple-procedure reductions when bilateral TKA or bilateral knee arthroscopy is performed with an additional procedure the same day—getting the order of adjustments wrong understates the allowed amount for the bilateral service.

CPT codes that use modifier 50

861 orthopedic CPT codes in our reference list this modifier as applicable. Sorted by total RVU.

Source · Derived from per-code modifier guidance in our CPT reference

• 27278 $13,754.82
  Percutaneous arthrodesis of the sacroiliac joint performed under image guidance, with placement of intra-articular implant(s) — such as bone allograft or a synthetic device — without transfixing the joint.
• 20983 $4,905.92
  Percutaneous cryoablation of one or more bone tumors, including destruction of adjacent soft tissue involved by tumor extension, with imaging guidance bundled into the code when performed.
• 20982 $3,482.38
  Percutaneous ablation of one or more bone tumors using radiofrequency energy, including treatment of adjacent soft tissue involved by tumor extension, with imaging guidance when performed.
• 20805 $2,899.20
  Complete replantation of a traumatically amputated forearm, reattaching bone, vessels, nerves, and soft tissue.
• 21125 $2,595.58
  Surgical augmentation of the mandibular body or angle using prosthetic implant material to enlarge or reshape the lower jaw.
• 20957 $2,456.30
  Microvascular bone graft harvested from the metatarsal, transferred to a recipient site with microsurgical vascular anastomosis to restore active blood supply.
• 20962 $2,428.25
  Microvascular bone graft harvested from a donor site other than the fibula, iliac crest, or metatarsal, transplanted with its intact arterial and venous supply to fill a major skeletal defect at the recipient site.
• 21261 $2,175.73
  Periorbital osteotomies for orbital hypertelorism using a combined intra- and extracranial approach, with bone grafts to reposition the orbits and fill bony defects.
• 20824 $1,841.06
  Surgical reattachment of a completely amputated thumb, spanning the carpometacarpal joint through the MP joint, including repair of bone, vasculature, nerves, and soft tissue.
• 20816 $1,835.71
  Replantation of a single digit (excluding the thumb) following complete amputation, covering the metacarpophalangeal joint through the insertion of the flexor sublimis tendon.
• 27458 $1,731.50
  Femoral osteotomy performed with insertion and management of an externally controlled intramedullary lengthening device for limb-length discrepancy correction.
• 27134 $1,695.43
  Revision of total hip arthroplasty involving replacement of both the femoral and acetabular components in a single operative session.

Showing top 12 of 861 by total RVU.

Where modifier 50 shows up

Body regions where this modifier most commonly appears in our orthopedic reference.

• Foot & ankle 216 codes
• Wrist 102 codes
• Knee 99 codes
• Shoulder 90 codes