Epidural fibrosis has been considered to be enough of a concern to spine surgeons that its prevention has been a subject of concern since the early 1900s when Lexer (Lexer E: Die Freien Transplantation en Pat 1, Neue Deutsche Chirurgie 26:264-545, Stuttgart: Ferdinand Enke,1919) first reported on the use of free fat grafts for this purpose. Many forms of fat including pedicled grafts and a host of biocompatible materials have continued to be tested. Mayfield, in 1980, documented his 16 years of clinical experience with fat grafts and noted that they could prevent “constricting cicatrix” as well as serve to control cerebro-spinal fluid leaks and in the repair of dural tears. He also noted that their greatest danger was the possibility of their acting as a space occupying lesion and causing neural compression (Mayfield FH: Autologous Fat Transplants for the Protection and Repair of the Spinal Dura, In Clinical Neurosurgery, Vol. 27, Baltimore: Williams and Wilkins, 1980)
Three examples of severe post-operative epidural and perineural scarring demonstrated on axial view computed tomographic scans (CT) are shown above. In the first two cases the patient required additional surgery because of continued post-surgical spinal nerve compression. In the first case the red dot shows a residual (post-surgical) bony osteophyte continuing to produce lateral spinal stenosis. In the second case the red dot is over a posteriorally displaced bone plug following a posterior lumbar interbody fusion with a autogenous bone plug. In example three the red dot is over a post-operative collection of spinal fluid (pseudomeningocoele) which resulted from an intra-operative dural tear. All three of these patients required additional “salvage” surgery.
The Burton Experience with routinely applied autogenous free fat grafts has extended over a 25 year period and has included approximately 5,000 cases. On the basis of this experience the following observations are made:
Indications for Use of Fat:
- Prevention of constricting epidural fibrosis
- Prevention of excessive epidural scar tissue.
- Preventing normal post-decompression dural dilatation.
- The prevention of cerebrospinal fluid leakage from dural tears and other defects.
- Filling dead space (i.e. arachnoidal cysts)
- Protective barrier (i.e. strut stabilization with milled
- Readily available material.
- Survives as normally vascularized fat.
- Allows for ease of dural separation in subsequent surgeries.
- Acts as additional protective barrier for dura.
- Is not neurotoxic to the subarachnoid space.
- Fat becomes vascularized and serves to nourish dura
- The price is right.
- Can act as a space occupying mass and produce compression of neural elements.
- Consistency of fat is not uniform, areas of fat necrosis can occur.
- If separate incision is necessary hematoma formation is possible.
- Separate incisional donor site can be painful.
- Fat can act as a lubricant in subsequent surgeries and can increase the risk of instrument slippage.
Autogenous free fat grafts can be harvested from the primary incisional site or through separate buttock incisions. Incisions should be made to avoid interrupting the cluneal nerve complex (see above). The quality of fat is important because thick and fibrous adipose tissue is more likely to produce a mass effect.
The center image is a axial CT scan performed 10 years after previous fat grafting. The yellow dot is over the fat tissue which has become vascularized. In the image to the right the yellow dots are over 3 fat graft sections placed at surgery. It is important to place lateral fat first to act to support the dorsal fat mass. This aids in avoiding dural sac compression. Orientation is the same as the CT scan.
This operative photograph shows a fat graft in-situ 6 years after a surgical procedure. Dorsal fat graft is identified by the yellow dot. The fat is normal and vascularized. The dural sac is shown at the site of the blue dot. The dural surface is essentially normal and was easily separated from the surrounding fat graft. Post-surgical dural dilatation has not occurred.
Post-surgical dural compression producing cauda equina compression has occurred in less than 0.01% of the Editor’s series.
The cases involved severe central spinal stenosis where the tension of the fat graft impaired already abnormal roots of the cauda equina. In all cases the patients immediate post-operative onset of sacral anesthesia and parasthesia associated with leg weakness allowed early diagnosis, surgical revision, and subsequent recovery.
MRI views of a 3 month post-operative patient who had titanium cages inserted at the l3-4 level and local autologous fat grafts. Slight post-operative dural sac dilatation is noted. The fat has become vascularized and a pseudo-membrane is shown with the green dots.
Alternative Substances In Preventing Epidural Fibrosis
Fat is not optimal, in all regards, as a substance to be used in preventing epidural fibrosis and serving as a barrier to excessive scar formation. Fats greatest asset is that it has withstood the test of time. Of the various natural and artificial substances also being used as an alternative to fat grafts none have yet been proven to be superior to autogenous fat when all aspects are considered.
Adcon-L is a partially resorbable barrier gel substance composed of porcine derived gelatin and a complex sugar of the polyglycan family in a phosphate buffered saline solution.
Manufactured by Gliatech (www.gliatech.com) this product was approved by the United States Food and Drug Administration in May 1998. The Adcon-L gel represents the beginning of important new technology in addressing the control of unwanted post-operative adhesions. Its major benefit is that it does not appear to act as a space-occupying lesion or an irritant. It’s major liability is that it does not act as a space occupying mass to exert a desired tension on surrounding spinal tissues and gain this advantage. The use of Adcon-L adds about $800-1,000 to the patient’s hospital bill. Despite shortcomings there continues to remain significant commercial interest in developing various substances intended to reduce post-operative adhesions. As of the year 2000 the Burton Report® has identified the following organizations involved in developing such products:
Organization – Product
Alliance Pharmaceutical – Flogel®
Anika Therapeutics – Incert®
Biomatrix – Hylagel®
Ethicaon – Interceed®
Genzyme – Seprafilm®
Gliatech – Adcon-L®
W.L. Gore – Gortex®
Life Medical Sciences – Repel®
LifeCore Biomedical – Lubriciat®
Omrix Pharmaceuticals – Quixil®
The images at either side show a synovial chondroma (red dot) in a 42 year old male. This lesion is producing significant spinal cord compression. Facet joints with effusion (yellow dots) document associated segmental dysfunction. Adcon-L was used surgically in this case specifically because of its lack of mass effect on local structures (i.e. spinal cord).
At the present time the careful use of autogenous fat grafts of proper volume and consistency represent the procedure of choice in the majority of spine surgery cases to avoid undesired epidural fibrosis. The only reason that free fat grafts are not used more widely appears to have to do with lack of understanding of “Pitfall Prevention”>
In certain circumstances, such as indicated above, where the addition of any significant mass is undesirable the use of a biocompatible substance such as Adcon-L can be a preferred addition to the surgical procedure. If Gliatech, or one of its industrial colleagues, were to also develop a companion product which maintained a biofriendly mass effect it might then become preferred to autogenous fat grafting. Autogenous fat grafts have allowed a number of important surgical innovations such as in the management of arachnoidal cysts producing bone erosion and nerve compression.