The fate of autogenous free-fat grafts after posterior lumbar surgery: part 2. Magnetic resonance imaging and histologic studies in repeated surgery cases

Epidural fat mesenchymal stem cells: Important microenvironmental regulators in health, disease, and regeneration: Do EF-MSCs play a role in dural homeostasis/maintenance?

Mesenchymal stem cells (MSCs) are present in fat tissues throughout the body, yet little is known regarding their biological role within epidural fat. We hypothesize that debridement of epidural fat and/or subsequent loss of MSCs within this tissue, disrupts homeostasis in the vertebral environment resulting in increased inflammation, fibrosis, and decreased neovascularization leading to poorer functional outcomes post-injury/operatively. Clinically, epidural fat is commonly considered a space-filling tissue with limited functionality and therefore typically discarded during surgery. However, the presence of MSCs within epidural fat suggests that itis more biologically active than historically believed and may contribute to the regulation of homeostasis and regeneration in the dural environment. While the current literature supports our hypothesis, it will require additional experimentation to determine if epidural fat is an endogenous driver of repair and regeneration and if so, this tissue should be minimally perturbed from its original location in the spinal canal. Also see the video abstract here https://youtu.be/MIol_IWK1os.

Multifunctional Supramolecular Hydrogel for Prevention of Epidural Adhesion after Laminectomy

Postoperative epidural adhesion remains a clinically challenging problem in spine surgery. Currently there are no effective and safe antifibrotic and antiadhesion biomaterials that have been specifically developed for this complication in clinical practice. Herein we designed and engineered an advanced antiadhesion hydrogel with multiple functionalities, including temperature-responsive gelation, self-healing, tissue adhesiveness, antioxidation, anti-inflammation, and antifibrosis. This multifunctional supramolecular hydrogel can be facilely constructed by integrating three functional modules, i.e., a thermosensitive triblock copolymer, poloxamer 407 (PX); a reactive oxygen species-eliminating and anti-inflammatory nanoparticle (TPCD NP); and an adhesion-enhancing compound, tannic acid (TA). The optimal formulation (PXNT) was hierarchically screened based on in vitro properties and in vivo activities. Therapeutically, local treatment with PXNT hydrogel effectively prevented epidural fibrosis and adhesion after laminectomy in both rats and rabbits. Of note, PXNT hydrogel showed more beneficial efficacy than different control thermosensitive hydrogels and a commercially available barrier product, Interceed. Mechanistically, PXNT hydrogel significantly attenuated local oxidative stress, inhibited inflammatory responses, and reduced fibrotic tissue formation. Moreover, treatment with PXNT hydrogel did not cause systemic adverse effects and neurological symptoms. Consequently, PXNT hydrogel is a highly promising biomaterial for preventing postlaminectomy epidural adhesion and adhesions after other surgeries.

Discectomy with Subsequent Free Fat Flap Insertion in Disc Perforation Therapy of Temporomandibular Joint. Assessment of Results 24 Months after Operation

Discectomy with replacement of disc is one possibility for treating disc perforation where conservative, mini-invasive therapy and arthroscopy has had no effect. Allogenic or autologous materials are used to replace the disc. The authors assess the use of a free fat flap (FFF) in 19 patients who in 2015-2016 underwent a unilateral discectomy with disc replacement. In the retrospective 24-month follow-up study a total of 16 patients (84%) were free of difficulties. 24 months after the operation mouth opening was on average 39.3 mm, pain (VAS - visual analog scale (0-10) was assessed on average at 0.3). Crepitus was present after 24 months in 37.5% of patients (6 patients). An assessment of changes in joint structures on cone beam computed tomography (CBCT) for these patients 24 months after the operation showed the progression of flattening of the joint head, in one case unevenness of the joint head. In 3 cases (16%) there was a recurrence of the state within 24 months - in all cases with clinical manifestations of pain and limited mobility, for these patients on the CBCT significant unevennesses of the joint head, subchondral cysts were noted. The authors find discectomy with use of FFF to be an effective method of treatment with a minimum of complications. However, one should take into account the relatively short time of monitoring after the operation (2 years) and limited number of patients in the cohort (19 patients).

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.

Update on biomaterials for prevention of epidural adhesion after lumbar laminectomy

Lumbar laminectomy often results in failed back surgery syndrome. Most scholars support the three-dimensional theory of adhesion: Fibrosis surrounding the epidural tissues is based on the injured sacrospinalis behind, fibrous rings and posterior longitudinal ligaments. Approaches including using the minimally invasive technique, drugs, biomaterial and nonbiomaterial barriers to prevent the postoperative epidural adhesion were intensively investigated. Nevertheless, the results are far from satisfactory. Our review is based on various implant biomaterials that are used in clinical applications or are under study. We show the advantages and disadvantages of each method. The summary will help us to figure out ideas towards new techniques. The translational potential of this article: This review summarises recent biomaterials-related clinical and basic research that focuses on prevention of epidural adhesion after lumbar laminectomy. We also propose a novel possible translational method where a soft scaffold acts as a physical barrier in the early stage, engineered adipose tissue acts as a biobarrier in the later stage in the application of biomaterials and adipose-derived mesenchymal stem cells are used for prevention of epidural adhesion.

The fate of autogenous free fat grafts in the human temporomandibular joint using magnetic resonance imaging

OBJECTIVE

Autologous fat grafts in the temporomandibular joint (TMJ) has achieved positive clinical effects in preventing adhesion after surgery. However it still remains indeterminate about the survival rate of grafted fat. The purpose of this study was to evaluate the long-term survival rate of free fat grafts in the TMJ using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

89 patients (117 joints) with free fat grafts placed into TMJs following modified TMJ disc anchor were included in our study. They were divided into the following groups according to the time lapse between TMJ surgery and the latest MRI investigation: 1-3 months, 4-6 months, 7-12 months, 13-24 months, and >24 months. The signal intensity changes and volume retention were evaluated by MRI.

RESULTS

The volume retention rate of grafted free fat showed that the size was hovering right around 50% although it reduced very slowly with a long-term follow-up. Nearly half joints showed lower signal intensity of the grafted fat on MRI within 6 months and it recovered to normal compared with that of the day after surgery 6 months later.

CONCLUSIONS

Free fat grafted into TMJ cavity could be alive for a long time with the survival rate about 48.44%. However the survival mechanism has still been unknown, which need us to explore and study in the future.

Implantation of amniotic membrane to reduce postlaminectomy epidural adhesions

Postlaminectomy epidural adhesion is implicated as a main cause of "failed back surgery syndrome" and associated with increased risk of complications during revision surgery. Various materials acting as mechanical barriers to reduce fibroblasts infiltration into epidural space have met with limited success. In present research, amniotic membrane (AM) was studied to investigate its effects on reducing epidural scar adhesion after laminectomy in a canine model. Laminectomy sites were created at L-1, L-3, L-5, and L-7 levels in 24 adult mongrel dogs. Freeze dried AM (FAM), cross-linked AM (CAM), and autologous free fat (AFF) were implanted, respectively, at a randomly assigned site in each dog with the remaining untreated site serving as internal control. The animals were sacrificed at 1, 6, and 12 weeks postoperatively. Then, gross pathologic observation including scar amount and adhesion tenacity, qualitative histology evaluation, and quantitative histology analysis were compared. Gross observation demonstrated that scar amount and adhesion tenacity of CAM group were significantly lower in comparison with those of FAM and non-treatment groups. A white, slightly vascularized CAM layer covered the dura mater without tenacious scar adhesion. The histology analysis also indicated reduced fibroblasts infiltration and consequent epidural fibrosis, which were similar to the results of AFF group. In conclusion, the CAM is effective in reducing epidural fibrosis and scar adhesion after laminectomy in canine model. It is a promising biomaterial for future clinical applications.

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.

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.

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 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.