Spinal fusion is a surgical procedure used to correct problems with the small bones in the spine (vertebrae). It is essentially a “welding process”. The main goal of this surgery is to fuse together two or more vertebrae into a single, solid bone to restore the stability of the spine.
All spinal fusions use some type of bone material, called a bone graft to help promote the fusion process. These bone grafts doesn’t heal or fuse the spine immediately, instead it stimulates the new bone production and helps the vertebrae heal together into a single solid bone.
Bone graft considerations:
There are a number of deciding factors to be considered for the selection of bone grafts. However the main factors to be taken into account include:
- Type of spinal fusion (ALIF, PLIF and others)
- The number of levels of the spine involved.
- Location of the fusion
- Patient risk factors (example: obese, smoker and poor bone quality)
- Surgeon experience and preference.
Types of bone grafts:
There are two types of bone grafts: real bone and bone graft substitutes. The type of bone graft is an important element to assign the correct codes and the definition is provided below for more clarity:
Real bone graft:
It refers to bone graft that comes from your own body (known as autograft) or harvested from a cadaver donor (known as allograft).
Autograft: An Autograft is a transplanted bone taken from the patient’s body and the process of obtaining the graft is called harvesting. It is considered the best choices of bone grafts because it contains the patient’s bone cells, proteins, and calcified matrix, all of which help to stimulate healing of the fusion. Bone may be harvested from one of the patient’s iliac crests (pelvic bones) or another source, such as a rib or the spine requiring an additional incision during the operation.
Allograft: An allograft is a bone graft that comes from a donor. It usually comes from bone banks that harvest the bone from cadavers. The types of allograft bone used for spine surgery include fresh frozen and lyophilized (freeze dried). The bone is cleaned and disinfected to reduce the possibility of disease transmission from donor to recipient. It is less effective when compared to that of an autograft as it does not contain living bone cells.
Bone graft substitutes:
These are man-made or a manipulated version of a natural product having similar properties to human bone including a porous structure and/or proteins to stimulate healing. They are generally categorized as below:
- Demineralized bone matrix (DBM)
- Synthetic bone graft extenders
- Bone morphogenetic proteins (BMP)
Demineralized bone matrix: It is an allograft bone that has undergone the process of removing mineral components, while leaving much of the proteinaceous components native to bone. These proteins are further processed and available in various forms such as chips, gel, putty or powder. This type of product is called demineralized bone matrix, and it can be readily used in place as a bone graft or as an extender to the patient’s own bone.
DBM Products: Stimublast, Allomatrix, DBX, Grafton
Synthetic bone graft extenders: These include substances such as ceramics, calcium phosphate and other synthetic materials that have similar properties and structure to that of a cadaver bone (allograft).They allow for new bone growth on their surface and later resorbed by the body, with the patient’s own bone remaining in place.
Bone morphogenetic proteins (BMP): BMP is a naturally occurring human protein used to stimulate new bone growth. These proteins are found in trace amounts in human bone and are produced in larger amounts by means of genetic engineering.
Key components for the selection of bone graft codes:
- Type of bone graft: Allograft and Autograft
- Incision site for the autograft
- Nature of the graft: Morselized or structural
The above key components are framed into questions for better understanding:
1. Does the bone graft come from patient’s own body?
When choosing bone graft codes, it is essential to know if the graft is obtained from the patient’s own body. The graft obtained from the patient’s own body is defined as autograft and the applicable autograft codes are 20936, 20937 and 20938.
+20936 Autograft for spine surgery only (includes harvesting the graft); local (eg, ribs, spinous process, or laminar fragments) obtained from same incision (List separately in addition to code for primary procedure)
+20937 Autograft for spine surgery only (includes harvesting the graft); morselized (through separate skin or fascial incision) (List separately in addition to code for primary procedure)
+20938 Autograft for spine surgery only (includes harvesting the graft); structural, bicortical or tricortical (through separate skin or fascial incision) (List separately in addition to code for primary procedure)
2. Where is the incision?
When choosing autograft codes, you need to determine whether the bone for the graft is harvested from the same site into which the graft will be placed, or from a separate site.
If the surgeon harvests and places the bone through the same incision, then report CPT 20936.
If the surgeon harvests the bone from a different incision, then report CPT 20937 or 20938 based on the nature of the graft as morselized or structural.
3. Is the graft morselized or structural?
You must know the difference between morselized and structural graft to select the appropriate bone graft codes. A structural graft is a larger piece of bone graft to fill into bony defects. A morselized graft refers to small pieces of bone graft.
For a morselized autograft, you need to report CPT 20937.
For a structural autograft, you need to report CPT 20938.
From all the above questions, you can derive the codes for autograft bone grafts used in spine surgery.
The similar pattern of questions can be followed for the allograft bone grafts EXCEPT the incision site as the allografts are obtained from the bone banks or the donors.
1. Does the bone graft come from a bone bank or donor other than the patient?
The graft obtained from a bone bank or donor is defined as allograft and the applicable allograft codes are 20930 and 20931.
+20930 Allograft, morselized, or placement of osteopromotive material, for spine surgery only (List separately in addition to code for primary procedure)
+20931 Allograft, structural, for spine surgery only (List separately in addition to code for primary procedure)
2. Is the graft is morselized or structural?
For a morselized allograft, you need to report CPT 20930.
For a structural allograft, you need to report CPT 20931.
- All spinal bone graft codes are add-on codes. Therefore you should not report modifier 51 multiple proceduresto bone graft codes 20930-20938.
- Per CPT instructions, do not append modifier 62 two surgeons to bone graft codes 20930-20938.
- Only one bone graft code per operative session is allowed per CPT guidelines.
Happy learning! Happy coding!