The fate of autogenous free-fat grafts after posterior lumbar surgery: part 1. A postoperative serial magnetic resonance imaging study

Role of epidural fat in the local milieu: what we know and what we don't

PURPOSE

Traditionally, the epidural fat (EF) is known as a physical buffer for the dural sac against the force and a lubricant facilitating the relative motion of the latter on the osseous spine. Along with the development of the studies on EF, controversies still exist on vital questions, such as the underlying mechanism of the spinal epidural lipomatosis. Meanwhile, the scattered and fragmented researches hinder the global insight into the seemingly dispensable tissue.

METHODS

Herein, we reviewed literature on the EF and its derivatives to elucidate the dynamic change and complex function of EF in the local milieu, especially at the pathophysiological conditions. We start with an introduction to EF and the current pathogenic landscape, emphasizing the interlink between the EF and adjacent structures. We generally categorize the major pathological changes of the EF into hypertrophy, atrophy, and inflammation.

RESULTS AND CONCLUSIONS

It is acknowledged that not only the EF (or its cellular components) may be influenced by various endogenic/exogenic and focal/systematic stimuli, but the adjacent structures can also in turn be affected by the EF, which may be a hidden pathogenic clue for specific spinal disease. Meanwhile, the unrevealed sections, which are also the directions the future research, are proposed according to the objective result and rational inference. Further effort should be taken to reveal the underlying mechanism and develop novel therapeutic pathways for the relevant diseases.

The impact of posterior epidural adipose tissue on postoperative outcomes after posterior decompression surgery for lumbar spinal stenosis: A prospectively randomized non-inferiority trial

STUDY DESIGN

The present study is a prospectively randomized study.

OBJECTIVE

The objective of the study was to evaluate the impact of posterior epidural adipose tissue (PAT) on postoperative outcome following lumbar decompression surgery for lumbar spinal stenosis (LSS) by whether PAT was removed or preserved during the surgical procedure.

SUMMARY OF BACKGROUND DATA

In posterior decompression surgery for LSS, PAT is routinely removed without knowledge of its role and significance. However, considering adipose tissue has regenerative properties of damaged neighboring tissues or itself, PAT, which is adipose tissue located at peridural space, might also have a potential to regenerate the neighboring damaged tissue, including dura and nerve root in the lumbar spine, but this has not been thoroughly studied.

METHODS

Of the 185 eligible patients screened for the current study, 181 patients were enrolled and randomly allocated into either group A (PAT removal, n = 90) or group B (PAT retention, n = 91). The primary outcome measure was pain intensity on the lower back and lower extremity. The secondary outcome measures were functional outcome based on the Oswestry disability index (ODI) and walking distance, complications during the surgical procedure, and surgical outcomes.

RESULTS

Postoperative pain intensity on the lower back and lower extremity was greater in group A than in group B. Functional status on ODI and walking distance was also worse in group B than in group A (64.9% in group A and 66.2% in group B). The number of patients with aggravated pain intensity and deteriorated functional status in postoperative follow-up times was significantly greater in group A than in group B. There were no significant differences in surgical outcome and complications between the groups.

CONCLUSION

Preserving epidural fat may be favorable in postoperative outcomes of posterior decompression surgery for LSS compared to removing epidural fat.

Viability and Volumetric Analysis of Free Autogenous Dermis Fat Graft as Interpositional Material in TMJ Ankylosis: A Long-Term MRI Study

Aims and Objectives

Dermis fat graft has shown good clinical results as an interpositional material in temporomandibular joint (TMJ) ankylosis and prevents heterogeneous calcification following gap arthroplasty. However, survival of the graft and volume retention is still debatable. The main purpose of our study was to assess the viability of the graft, tissues changes associated with the graft and volume retention using magnetic resonance imaging (MRI).

Materials and Methods

Fifteen patients with TMJ ankylosis underwent gap arthroplasty followed by placement of abdominal dermis fat graft and were randomly divided into two groups. Group 1 was subjected to MRI analysis of the graft at 3-6 months and Group 2 was analyzed at 1-2 years post-operatively. The graft was evaluated using T1- and T2-weighed images along with fat suppression (FS) sequences in all the three planes and the volume was also calculated.

Results

Both Group 1 (7 patients and 11 joints) and Group 2 (8 patients and 13 joints) showed the presence of viable fat on T1 and T2 images, confirmed by FS images. Minor tissue changes were observed at the center of the graft in 5 patients of Group 1 and 3 patients of Group 2. Average volume of the graft was 4.154 cm³ at 3-6 months and 4.269 cm³ at 1-2 years, respectively, and when compared to the original volume of the graft (4.583 cm³ in Group 1 and 4.712 cm³ in Group 2), the difference was statistically insignificant (p > 0.005).

Conclusion

MRI shows long-term survival of autogenous dermis fat graft without significant volumetric reduction. This along with positive clinical results make dermis fat an excellent choice as an interpositional material for TMJ ankylosis.

Mechanical barriers and transforming growth factor beta inhibitor on epidural fibrosis in a rabbit laminectomy model

Background

TGF-β has been described as a mediator of fibrosis and scarring. Several studies achieved reduction in experimental scarring through the inhibition of TGF-β. Fibroblasts have been defined as the cell population originating fibrosis, blocking fibroblast invasion may impair epidural fibrosis appearance. For this purpose, biocompatible materials used as mechanical barriers and a TGF-β inhibitor peptide were evaluated in the reduction of epidural fibrosis.

Methods

A L6 laminectomy was performed in 40 New Zealand white rabbits. Divided into four groups, each rabbit was assigned to receive either collagen sponge scaffold (CS group), gelatin-based gel (GCP group), P144® (iTGFβ group), or left untreated (control group). Four weeks after surgery, cell density, collagen content, and new bone formation of the scar area were determined by histomorphometry. Two experienced pathologists scored dura mater adhesion, scar density, and inflammatory infiltrate in a blinded manner.

Results

In all groups, laminectomy site was filled with fibrous tissue and the dura mater presented adhesions. Only GCP group presented a significant reduction in collagen content and scar density.

Conclusion

GCP treatment reduces epidural fibrosis although did not prevent dura mater adhesion completely.

Electronic supplementary material

The online version of this article (10.1186/s13018-018-0781-6) contains supplementary material, which is available to authorized users.

Fate of Free Fat Dermis Graft in TMJ Interpositional Gap Arthroplasty: A Long Term MRI Study

INTRODUCTION

Free fat dermis graft is a good interpositional material for TMJ gap arthroplasty. Analysing the fate of the graft by magnetic resonance imaging (MRI) images helps in excellent visualization of both bony and soft tissue anatomy of the operated TMJ joint as well as in assessing the changes in dermis graft which was previously placed.

PURPOSE OF THIS STUDY

To investigate the radiological fate of the dermis-fat graft within the TMJ using MRI.

MATERIALS AND METHODS

Five joints of five patients who had dermis-fat grafts placed in their TMJ following gap arthroplasty were recruited for this study. Each patient had undergone TMJ gap arthroplasty with immediate dermis-fat graft placement. All the patients are then subjected to MRI.

RESULTS

Fat graft was identified in close proximity to the mandibular condyle in all cases, with only three joints demonstrating fat covering the entire articular surface of the mandibular condyle. In the remaining joints the interpositional material found in the MRI defined joint space with mainly grey appearance, suggesting tissue change to other than fat, i.e. scar or granulation tissue.

CONCLUSION

When free fat dermis graft is placed as interpositional material the graft occupied the entire TM joint and prevented it from recurrent ankylosis. The graft placed aids in normal functioning of the temperomandibular joint without any complications.

Reconstruction of epidural fat with engineered adipose tissue from adipose derived stem cells and PLGA in the rabbit dorsal laminectomy model

Epidural fibrosis resulted from epidural fat destruction following laminectomy operation is regarded as a main cause of failed back surgery syndrome, which represents one of the most common complications in spine surgery. Up to now, the effectiveness of currently available treatments to prevent such a syndrome is quite limited. In the present study, we aimed to restore epidural fat using adipose tissue engineered from adipose derived stem cells (ASCs) in a rabbit dorsal laminectomy model. ASCs isolated from subcutaneous fat were first expanded to passage 3, seeded on porous poly(lactic-co-glycolic acid, PLGA) scaffold and then adipogenically induced for 7 days in vitro to form cell-scaffold complex. Laminectomy sites were created at T13-L1 level in each animal. The laminectomy defect was implanted either with cell-scaffold complex or PLGA scaffold alone. Non-treated defect was also included as a control. The animals were subjected to MRI evaluation at 1, 12 and 24 weeks post-surgery, and sacrificed at 24 weeks for gross and histological observation. It was demonstrated by MRI evaluation that scar tissue of coarse and high density was formed within laminectomy site in PLGA alone and non-treated groups as early as 12 weeks. However, the defect implanted with engineered adipose had formed a continuous linear adipose tissue regenerated along the spinal cord at 24 weeks. Histologically, a distinct area of adipose tissue just overlaying the dura mater could be identified in cell-scaffold complex treated group at 24 weeks post-operation. Regeneration of epidural fat was further confirmed by positive Oil Red O staining. As to the defect treated with PLGA alone or left untreated, either fine or dense scar tissue adhering to the dura mater was observed. Moreover, we could track the implanted ASCs labeled by magnetic nanoparticles within epidural area for as long as four weeks by MRI detection. Thus, adipose tissue engineered from ASCs exhibited great potential in restoration of epidural fat to prevent formation of epidural fibrosis.

Cerebrospinal fluid leaks following cervical spine surgery

BACKGROUND

A cerebrospinal fluid leak during cervical spine surgery is a feared complication. However, little is known about the prevalence, management, and long-term course of these events.

METHODS

The medical records of 1994 patients who had elective cervical spine surgery during an eleven-year period (1994 through 2005) were reviewed. Patients with cervical cerebrospinal fluid leaks identified at the time of surgery were followed both clinically and radiographically for an average of 5.4 years postoperatively. The prevalence, etiology, management, and outcome of all of the cervical cerebrospinal fluid leaks were analyzed.

RESULTS

The overall prevalence of cerebrospinal fluid leaks was 1%. The prevalence of cerebrospinal fluid leaks was higher in patients with a diagnosis of ossification of the posterior longitudinal ligament (12.5%), patients having a revision anterior procedure (1.92%), men (1.56%), and patients undergoing an anterior cervical corpectomy and arthrodesis (1.77%).

CONCLUSIONS

Many cervical dural tears can be managed by observation alone or by placement of a lumbar cerebrospinal fluid shunt either during the index procedure or in the postoperative period. At an average follow-up of 5.4 years, there were no long-term sequelae of the cervical dural tears in our series.

The effects of free fat graft or cellulose membrane implants on laminectomy membrane formation in dogs

The purpose of this study was to determine the effect of cellulose membrane or free fat grafts (FFG) on laminectomy membrane (LM) formation. Eighteen dogs were randomly divided into three groups of six dogs. All dogs underwent a modified dorsal laminectomy on T(13)-L(1). The laminectomy defect was left uncovered in the control group but either a FFG or a cellulose membrane implant was provided in the other two groups. The dogs were evaluated through neurological examination, myelography, macroscopic roundness index of spinal cord and histological evaluations of epidural fibrosis and spinal cord. The results showed a significant difference between the control and the FFG group, with the FFG causing neurological deficits and spinal cord compression as assessed by the roundness index of the spinal cord. Both FFG and cellulose membrane were partially effective in preventing LM formation. The use of FFG was associated with a high rate of significant neurological complications and spinal cord lesions.

Evaluation of DuraGen in preventing peridural fibrosis in rabbits. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2005

OBJECT

Peridural fibrosis is the scar tissue formed over the dura mater after a laminectomy. It has been implicated as a cause of persistence of pain after spinal surgery and associated with increased risk of complications during revision surgery. The application of a mechanical barrier to cover the peridural space to block the migration of inflammatory cells from superficial layers to the epidural space can potentially prevent or decrease scar formation. The authors evaluated the use of DuraGen for this purpose.

METHODS

Seventeen New Zealand White rabbits underwent bilateral L-4 and L-7 laminectomies. Each space was randomly assigned to either receive DuraGen, fat graft, or no (sham) treatment. At a mean 18 +/- 4 weeks after surgery, the animals underwent magnetic resonance (MR) imaging with and without Gd enhancement, and the area of the scar tissue overlying the middle of the laminectomy was measured. The rabbits were killed and the spinal cords with an intact dural covering were harvested. The midsection of each treated level was evaluated histologically and the scar area was measured. In rabbits in which a fat graft was placed, MR imaging of the epidural space demonstrated a significant (p < 0.05) increase in the mean area (0.9713 mm2) of scar tissue compared with those in which DuraGen was used (0.687 mm2) or those receiving sham treatment (0.6661 mm2). The same correlation was observed when the histological sections were measured at the middle of the laminectomy site where the mean areas of both DuraGen (1008 mm2) and control (2249 mm2) groups were significantly lower than that in the fat graft group (6007 mm2) (p < 0.01 and 0.05, respectively). No significant differences between the DuraGen and control groups were observed.

CONCLUSIONS

The authors demonstrated that peridural scarring formed in all groups. The mean area of scar deposition was significantly higher in the fat graft group than in the DuraGen or control group both on MR imaging and histological analysis. DuraGen was more effective than a fat graft in preventing epidural fibrosis but not significantly different from that occurring in control animals.

Magnetic resonance imaging of autologous fat grafting

A 30-year-old female patient with isolated facial lipodystrophy underwent two sessions of fat injection. MR signals of injected fat at different injection ages were compared to native fat. Native T1 signal was smaller for transplant fat, probably due to a slightly lower fat content and/or fibrosis or due to higher perfusion. T2 signal of transplants was significantly higher than that of native fat. T1 post-contrast was also higher, and contrast uptake of transplanted fat increased slightly with transplant age, which could be explained by an increasing perfusion. This study demonstrates the differences and MR signal time changes of native and transplanted fat.

Prevention of recurrent radicular pain after lumbar disc surgery: a prospective study

BACKGROUND

Postoperative epidural fibrosis is a major causative factor of low-back pain even if microsurgical techniques are adopted to reduce this phenomenon. To prevent the recurrent radicular pain caused by this problem, we utilized adipose tissue drawn from the same patient; at the end of surgical procedure, the fat was placed around the spinal root or the dural sac. This procedure was evaluated by a prospective, randomised study.

METHOD

From 180 patients operated on for lumbar discectomy between January 2000 to December 2001, 74 were enclosed in the study. In 37 patients, the spinal root was covered by autologous fat (group A), in the other 37 (control group, B), this procedure was not adopted. One year after surgery, all the patients were evaluated with clinical and radiological (Magnetic Resonance Imaging) follow-up. Only two patients were lost to follow-up.

FINDINGS

71% of the patients in group A had 100% of clinical and radiological post-operative outcome score; this result was obtained only in 35% of the patients in group B. A clinical score evaluating pain syndrome (from grade 0 to 5) and a radiological score evaluating postoperative fibrosis (from grade 0 to 4) was adopted. Therefore, group A had best outcome as compared to control group.

CONCLUSIONS

The authors found a positive effect in the reconstruction of epidural fat with autograft of adipose tissue to prevent postoperative scarring and failed-back syndrome related to postoperative fibrosis.

Collagen matrix (DuraGen) in dural repair: analysis of a new modified technique

STUDY DESIGN

Retrospective review of 110 patients undergoing spinal dural repair and regeneration using an onlay, suture-free, 3-dimensional-collagen matrix graft (DuraGen) over an 8-year period (1995-2003).

OBJECTIVES

Technique appraisal of collagen matrix to repair spinal dura following incidental durotomy, spinal tumor surgery, and trauma.

SUMMARY OF BACKGROUND DATA

Traditional methods of spinal dural repair following incidental durotomy involve tedious attempts at primary watertight suture with a 5% to 10% failure rate. Dural injury occurs after trauma, or dural excision may be required after tumor resection. Collagen matrix is a newer development in collagen sponge.

METHODS

The clinical and demographic data included diagnosis, type and site of surgery, infection risk, size of defect, use of lumbar drains, closed suction subfascial drains, and adverse events. The primary endpoints of graft failure were cerebrospinal fluid leak and pseudomeningocele formation. Neurosurgical wound infection rates were determined.

RESULTS

Collagen matrix was used (n = 110) in the following conditions: degenerative (69), pseudomeningocele formation repair (4), tumors (14), trauma (13), and congenital (5). There were 15 cervical (10 anterior), 21 thoracic (3 anterior), and 71 lumbar (all posterior) surgeries. Fibrin glue was used in 7.3%, subfascial drains in 82%, and lumbar drainage in 2.7%. Overall, cerebrospinal fluid leaks occurred in 2.7%. The 2 pseudomeningocele formations (3.2%) resolved at 3 months. There were 2 wound infections. In the subgroup with incidental durotomy (n = 69), failure of cerebrospinal fluid containment occurred in 4.3% [1 cerebrospinal fluid leak (1.4%), 2 pseudomeningocele formations (2.9%)].

CONCLUSIONS

Collagen matrix was successful in cerebrospinal fluid containment in > 95% of patients requiring dural repair following anterior and posterior spinal surgery. Subfascial drains were safe. Routine lumbar drains are not required but are recommended for repair of established pseudomeningocele formations.

The effect of perioperative corticosteroids on the outcome of microscopic lumbar disc surgery

Eighty adult patients with lumbar disc herniation verified by magnetic resonance imaging (MRI) and clinical findings corresponding to the radiological level underwent microscopic disc removal to evaluate the outcome of perioperatively given corticosteroids in a prospective randomized double-blind study. In the treatment group the patient received 250 mg Solu-Medrol intravenously and 160 mg Depo-Medrol intramuscularly. Before closure of the wound, a free fat transplant soaked in 80 mg Depo-Medrol was placed on the dural sac. In the control group the same procedure was performed, but sodium chloride was given instead of Depo-Medrol. All patients underwent a clinical examination before surgery and at 2, 6, 12, 26, 52 and 104 weeks postoperatively, rating their pain with the visual analog scale (VAS) and function with the Disability Rating Index (DRI). The postoperative hospital stay was significantly shorter (P=0.01) in the treatment group (1.7 days) compared to the control group (2.3 days). Time taken to return to full-time work was also significantly shorter in the treatment group (P=0.003). VAS-W (Worst Pain during last week) was significantly lower in the treatment group (P=0.02). Postoperative spondylitis occurred in one patient in the control group and no adverse corticosteroids effect was seen. Our study shows that perioperatively given corticosteroids improve the outcome of microscopic disc surgery in terms of length of hospital stay and time taken to return to full-time work. The results also indicate that corticosteroid treatment reduces pain and improves functional outcome.

The effect of epidural free fat graft on the outcome of lumbar disc surgery

Numerous materials have been used to prevent epidural scar tissue after lumbar disc surgery. Free fat grafts are common both experimentally and clinically, but there is some doubt about their protection against fibrosis, and some complications have been reported. In this prospective study, the usefulness of free fat grafts during lumbar disc surgery was evaluated. Ninety-nine patients who had undergone operation due to lumbar disc herniation were divided in two groups: those with implantation of free fat grafts (group A) and those without (group B). Outcome was evaluated at a mean of 2.6 years postoperatively according to the following criteria: visual analog scale for back and leg pain, Hannover Questionnaire on activities of daily living, reflex findings, sensory and motor deficits, consumption of analgesics, walking distance, straight leg raising test, and clinical examination. The outcome variables showed no significant differences between the two groups ( P>0.05). This study suggests that the use of free fat grafts during lumbar disc surgery was clinically ineffective.