Long-term outcomes of a bioactive matrix enriched with an autologous platelet concentrate for the treatment of complex anal fistulae

doi:10.21203/rs.3.rs-4944964/v1

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Long-term outcomes of a bioactive matrix enriched with an autologous platelet concentrate for the treatment of complex anal fistulae

https://doi.org/10.21203/rs.3.rs-4944964/v1

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Background

Treating complex anal fistulae (CAF) remains a clinical challenge. Regenerative Fistula Treatment (RFT) with a bioactive matrix enriched with autologous platelet concentrate (Obsidian RFT™) has shown potential in healing of CAF while preserving continence, but its long-term efficacy is still debated. This study aimed to report the outcomes of RFT in patients with CAF.

Methods

A retrospective analysis of a prospective database of patients with CAF treated with RFT between February 2021 and November 2023 at a single centre was conducted. Patients were included if they completed at least a 6-month follow-up. The primary outcome was fistula healing at last available follow-up. Secondary outcomes included unscheduled reoperation and anorectal function.

Results

Thirty-one patients were treated with Obsidian RFT, 17 of whom completed the 6-month-follow-up. Nine of the patients were women. The median age was 47 (24–63) years, and eight had inflammatory bowel disease. High trans-sphincteric fistulae were observed in 52.9% of patients. At a median follow-up of 21.8 (8–36) months, a 53% success rate was achieved. Approximately half of patients required at least one additional procedure due to CAF persistence or recurrence. There were no reports of morbidity and mortality, and no worsening of continence was observed.

Conclusions

This pilot study demonstrated that nearly half of the patients treated with RFT for CAF achieved long-term healing, with no adverse effects on continence and an excellent safety profile. Larger studies are needed to draw definitive conclusions.

complex anal fistulae

regenerative fistula treatment

complications

continence

Complex anal fistulae (CAF), both idiopathic and in the settings of inflammatory bowel diseases (IBD), still represent an unsolved challenge regarding the most appropriate surgical treatment options to approach them [1, 2].

This choice should consider many variables: the anatomy of the fistula, the underlying cause, and the proportion of the sphincter muscle component involved in the pathology [1, 3]. However, surgical treatment of CAF is still associated with high recurrence rates and carries high risk of complications, especially in women and in anterior fistulae [2, 4–6].

The surgical approach to CAF is most often done by steps, consisting of placement of a loose seton and subsequent definitive surgical treatment. This approach allows the surgeon to set up an initial control/elimination of the acute sepsis and defers the removal of any chronic granulation tissue until later [4]. Among the most used surgical treatments, fistulotomy achieves the highest cure rates, but it brings about a higher risk of worsening incontinence or the onset of de novo incontinence (in up to 10% of cases) [7]. Advancement flaps represent a viable option for CAF, but success rates rangeing from 40–80% [7–11]. Even with these procedures, continence disturbances remain a potential complication, with an estimated occurrence rate of around 20% [7].

To prevent postoperative continence disturbances and complications, several minimally invasive techniques have been proposed, including ligation of the intersphincteric fistula tract (LIFT), fibrin glue injection, video-assisted anal fistula treatment (VAAFT), fistula laser closure (FiLaC) and placement of acellular dermal matrix (ADM). These treatments aim to combine a good cure rate with preservation of sphincter function, with success rates ranging between 12.5% and 88% [5, 8, 9, 12–18]. However, few studies have reported the long-term outcomes of such procedures.

Biocompatible materials offers a new treatment option for CAF. Among them, Regenerative Fistula Treatment (RFT) with the Obsidian RFT® matrix has been proposed, consisting of a bioactive, 100% autologous matrix that incorporates both platelets and concentrated growth factors. These components activate and protect thrombocytes from potential damage, thereby promoting soft tissue, connective and vascular tissue regeneration. Therefore, it is indicated for the treatment of extra-sphincteric, inter-sphincteric, trans-sphincteric, and supra-sphincteric fistulae. [19–23]. The Obsidian RFT® is activated locally upon application in the fistula track, facilitated by the natural proteolytic absorption of the matrix. This activation process typically spans over a period of 4 to 7 days, during which continuous stimulations promote the healing process. This treatment is compatible with various surgical approaches and can be combined with other local interventions, and it is characterized by simplicity and ease of use, in addition to respecting the anatomy and physiology of the anal canal. [19–23]. However, there is a need for long-term outcome data and assessment of the safety of such procedure.

The objective of this study is to assess the long-term healing rates of CAF treated with RFT and to identify any associated complications and effects on continence.

This pilot study, conducted at a single center, involved a retrospective analysis of patients with CAF treated at Vall d’Hebron University Hospital, Barcelona, Spain, whose data were extracted from a prospectively maintained database. The study was conducted and reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement [23].

Inclusion and exclusion criteria

All patients with CAF who underwent RFT surgery with an autologous bioactive matrix (Obsidian RFT®) between February 2021 and June 2024 were evaluated for inclusion.

Inclusion criteria included: diagnosis of CAF, age above 18 years at the time of surgery, having undergone at least one prior surgical procedure for perianal sepsis, and having completed a follow-up period of at least 6 months. Patients with simple anal fistulae and who did not complete at least 6-month follow-up were excluded.

Definitions

Patients underwent endoanal ultrasound and/or magnetic resonance imaging (MRI), and CAF were described according to Park’s classification. Fistulae were defined as “complex” if they were high or middle trans-sphincteric, suprasphincteric, extrasphincteric or rectovaginal.

Disease persistence was defined as persistence of discharge or symptoms of perianal sepsis after surgery. Clinical recurrence was defined as the presence, upon clinical examination, of any perianal suppuration at gentle compression. Continence disturbance was defined as the occurrence of flatus, liquid or solid accidents after RFT treatment, in patients who were continent before treatment, or as worsening of continence compared to baseline.

Endpoints and outcome measures

The primary endpoint was defined as clinical fistula healing, indicated by the absence of discharge at last available follow-up visit. The number of patients with clinically active CAF served as the outcome measure. Secondary endpoints encompassed adverse events associated with RFT, need for additional surgery, impact on continence, and identification of factors associated with recurrence.

Surgical technique and RFT treatment

Prior to definitive surgery, patients undergo an examination under anaesthesia (EUA) to assess the fistula’s anatomy. A loose seton is inserted on the CAF tract and remains in place for 4–6 weeks before RFT treatment. No bowel preparation nor enemas are administered before RFT treatment. The procedure is conducted under epidural anaesthesia. Patients are positioned in lithotomy position for posterior CAF and in prone position for anterior CAF. Aqueous chlorhexidine is used for perianal antisepsis.

The loose seton is removed, and a fistula brush is employed to clean and debride the fistula tract. The tract is flushed with saline solution (37ºC), and debridement is repeated as necessary. Following each debridement, the tract is flushed again. Then, the internal orifice of the CAF is closed by a Z-suture and RFT is applied.

The procedure comprises the following steps: 1. Closure of the internal CAF orifice with a Z-suture; 2. The suture is tightened partially, without completely closing it; 3. Saline irrigation is conducted through the external CAF orifice to ensure no leakage from the internal CAF orifice is detected; 4. The suture is then loosened, and the Obsidian RFT endoscopic catheter is inserted through the external CAF orifice, reaching the internal orifice. RFT is applied continuously while slowly retracting the catheter using the “Jet No Air” setting. 5. The Z-suture is tied. Any remaining RFT is injected around the closure of the internal CAF orifice. 6. The external CAF orifice is left open.

The procedure is shown in Fig. 1 and Supplementary Video 1.

Postoperative management and follow-up schedule

After undergoing RFT treatment, patients are provided with post-procedural instructions to ensure optimal recovery. These include avoiding strenuous activities for one week following surgery, taking sitz baths three times a day, each lasting 15 minutes in warm water, to promote comfort and healing, and using analgesics as needed for perianal discomfort for up to three days.

The first follow-up appointment is scheduled 15 days after surgery. A second follow-up appointment occurs 15 days later. Subsequent follow-up appointments are scheduled every three months during the first year post-surgery, provided that both previous appointments show satisfactory progress. After the first year, follow-up visits are scheduled at 18 and 24 months, with no further appointments thereafter.

Ethics

This study adhered to the principles outlined in the Declaration of Helsinki and received approval from the local Ethical Committee. Prior to undergoing the procedure, all patients provided written informed consent.

Statistical analysis

Continuous variables are reported as medians with ranges, while categorical values are expressed as absolute numbers with corresponding percentages.

Thirty-one patients with CAF underwent surgery with RFT in the study period, of whom 17 completed the 6-month follow-up and were included in the analysis (Fig. 2). Among them, nine patients (53%) were women. The median age at the time of surgery was 47 (24–63) years.

Population Characteristics and Previous Procedures

Among the cohort, nine patients (52.9%) presented with a high trans-sphincteric fistula, while seven (41.2%) had a middle trans-sphincteric fistula, and one (5.8%) had a rectovaginal fistula. Anterior CAF were observed in 12 patients (70.5%), with the remaining 29.4% presenting posterior CAF (n = 5). Four patients (23.5%) were current smokers, and one (5.8%) was a former smoker. A summary of patient characteristics is provided in Table 1.

Additionally, eight patients (47%) had an underlying inflammatory bowel disease, with six diagnosed with Crohn’s disease and two with ulcerative colitis.

Prior to RFT treatment, patients had undergone various procedures, including abscess debridement (n = 9), acellular dermal matrix plug (PressFit™, Biocablan S.L.) placement (n = 7), advancement flap (n = 6), porcine dermal collagen implant (Permacol™, Medtronic Inc.) placement (n = 4), ligation of the intersphincteric fistula tract (LIFT, n = 3), stem cell treatment (n = 2), Martius flap (n = 1), endoluminal vacuum therapy (B. Braun Endo-SPONGE™) (n = 1) and sphincteroplasty (n = 1). Notably, all patients had had more than one surgical procedure.

The median interval between the “preparation” surgery (seton placement) and RFT was 18.8 months (range: 3–57). Except for one patient who underwent fistulotomy plus sphincteroplasty four months prior to RFT, none of the patients had a seton in place at the time of RFT treatment.

Table 1

Patient characteristics
Age, median (range years)	47 (24–63)
Sex, n (%)	9 F (53%) 8 M (47%)
Inflammatory bowel disease, n (%)	Crohn’s disease: 6 (35%) Ulcerative colitis: 2 (11.7%)
Smoking status n, (%)	Non-smoker: 12 (70%) Active smoker: 4 (23.5%) Ex – smoker: 1 (5.8%)
Fistula Park’s classification n, (%)	Trans-sphincteric, high: 9 (52.9%) Trans-sphincteric, middle: 7 (41.2%) Rectovaginal fistula: 1 (5.8%)
Fistula location n, (%)	Anterior: 12 (70.5%) Posterior: 5 (29.4%)
Previous procedures for RFT n, (%)	Abscess debridement: 9 (52.9%) Pressfit placement: 7 (41.1%) Advancement flap: 6 (35.3%) Permacol placement: 4 (23.5%) LIFT: 3 (17.6%) Stem cells placement: 2 (11.7%) Martius flap: 1 (5.8%) Endosponge: 1 (5.8%) Sphincteroplasty: 1 (5.8%)
Additional procedures after RFT n, (%)	Loose-seton placement: 4 (23.5%) Permacol placement: 2 (11.7%) Pressfit placement: 1 (5.8%) Abscess debridement: 1 (5.8%) LIFT: 1 (5.8%) Sphincteroplasty: 1 (5.8%) Repeated RFT: 1 (5.8%) Advancement flap: 1 (5.8%)
F: Female, LIFT: Ligation of the intersphincteric fistula tract, M: Male

Primary Outcome: Fistula Healing

The median follow-up period was 21.8 (8–36) months. The overall success rate of RFT treatment was 53% (9 patients). However, among the nine patients who achieved healing, three (17.6%) required at least one additional procedure following RFT.

The median time to treatment failure was 6.6 (1–20) months. Of the individuals in whom treatment failed (8 patients, 47%), three (17.6%) never achieved healing (disease persistence), while five (29.4%) experienced clinical recurrence after initially achieving healing.

Secondary Outcomes

Following treatment, one patient required emergency drainage of a perianal abscess. However, no further complications were observed during the follow-up period, and there were no recorded deaths.

Eight patients needed at least one additional surgical procedure, including seton placement (n = 4), porcine dermal collagen implant (Permacol® Medtronic Inc.) placement (n = 2), acellular dermal matrix plug (PressFit®, Biocablan S.L.) placement (n = 1), abscess debridement (n = 1), LIFT (n = 1), sphincteroplasty (n = 1), repeated RFT (n = 1) and an advancement flap (n = 1). The median interval between RFT and repeated surgery was 9 (3–20) months, with no adverse events recorded during and after these procedures. No deterioration in continence was noted following RFT treatment at last available follow-up.

Baseline and fistula characteristics are compared in Tables 2 and 3.

Table 2

Baseline characteristics according to the outcome
Variable	Healing	No healing
Age, median (range), years	50 (33–61)	43,7 (24–63)
Sex, n (%)	6M (35.3%) − 3F (17.6%)	2M (11.8%) -6F (35.3%)
Inflammatory bowel disease, n (%)	3 (33%)	5 (62.5%)
Immunosuppression, n (%)	3 (33%)	4 (50%)
Active smoker, n (%)	1 (11%)	3 (37.5%)
Diabetes mellitus, n (%)	2 (22%)	1 (12.5%)
Arterial hypertension, n (%)	4 (44%)	2 (25%)
F: Female, M: Male

Table 3

Comparison of fistula characteristics according to the outcome
Fistula characteristics	Healing group	Non-healing group
Time between seton placement and surgery, median (range) months	14.7 (3–39)	21.2 (4–57)
High trans-sphincteric and rectovaginal fistula, n (%) Middle trans-sphincteric, n (%)	5 (55.6%) 4 (44.4%)	5 (62.5%) 3 (37.5%)
Anterior, n (%) Posterior, n (%)	7 (77.8%) 2 (22.2%)	5 (62.5%) 3 (37.5%)
First-line treatment, n (%) Recurrent fistula, n (%)	3 (33.3%) 6 (66.6%)	2 (25%) 6 (75%)

This study assessed the long-term outcomes following the treatment of CAF with RFT and found that the RFT technique has a healing rate of more than 50 per cent at long-term follow-up, with no reported complications of function in the mid- and long-term, even in patients undergoing repeated surgical treatment.

Previous studies have reported healing rates for perianal fistulae ranging from 12.5–88% [5, 8, 9, 12–18]. The wide variation in healing rates may be attributed to several factors, including differences in the definition of "healing," the types of fistulae included in the study, and variations in the duration of follow-up (ranging from 1 week to 18 months).

In this study, the overall success rate of RFT was 53% at a median follow-up of 21.8 months. Treatment failure, including 17.3% disease persistence and 29.4% clinical recurrence, occurred within a median time of 6.6 months post-treatment. Recurrence rates tended to increase with longer follow-up periods, emphasizing the importance of adequate follow-up duration to accurately assess recurrence rates. This is important because a too short follow-up period contributes to the phenomenon known in clinical medical research methodology as the "honeymoon period": pilot studies often report excellent results that need to be confirmed by studies with longer and more comprehensive follow-up protocols. [24].

Due to the small sample size, no definitive conclusions can be drawn regarding patient and fistula characteristics predictive of treatment failure. However, female sex, inflammatory bowel disease, and smoking habit seemed to impair healing whereas patient age and cardiovascular disease did not (see Table 2).

Middle trans-sphincteric fistulae exhibited a slightly higher chance of healing (44.4% in the healing group versus 37.5% in the non-healing group) compared to high supra-sphincteric fistulae (55.6% in the healing group versus 62.5% in the non-healing group). Additionally, shorter intervals between seton placement and surgery were associated with higher cure rates (14.7 months in the healed group versus 21.2 months in the non-healed group, see Table 3).

Wang et al., in their systematic review and meta-analysis on the use of platelet-rich plasma (PRP) for anal fistula treatment, reported an overall healing rate of 72.11% (95% CI 0.64–0.79). The cure rate of PRP alone was 62.39% (95% CI 0.55–0.69), while the combined cure rate of PRP with other treatments was 83.12% (95% CI 0.77–0.88). The complete cure rate across 8 studies was 66.37% (95% CI 0.52–0.79), with a recurrence rate of 14.84% (95% CI 0.08–0.24) in 12 studies [25]. In the current study, combined treatment modalities included abscess debridement (52.9%), acellular dermal matrix plug (PressFi®, Biocablan S.L.) placement (41.1%), and advanced flap (35.3%) administered as pre-PRF injection treatment. While none of these represent definitive treatment techniques for anal fistulae, their inclusion may lead to an overestimation of RFT success due to the synergistic effects of combined approaches.

Study Limitations and Strengths

This retrospective analysis lacks a control group, posing limitations to the study. Additionally, the small sample size makes it challenging to draw definitive conclusions. Another limitation is that all patients in the study group underwent surgical treatment before receiving Obsidian RFT® injections, potentially influencing the outcome.

One major drawback of RFT is its cost, as it is a more expensive option compared to conventional techniques like fistulotomy, fistulectomy, advancement flap or LIFT, which do not require special materials or devices. However, RFT was not associated with short- or long-term morbidity. Moreover, the improvement in patient well-being, independent of CAF healing, suggests potential long-term value in reducing secondary costs.

This study has the advantage of being conducted in a group of patients followed by a surgical team specialised in the treatment of perianal pathology with expertise in minimally invasive CAF treatment. This allowed managing patients with rigorous and standardised pathways in the perioperative phase, and enabled the surgical team to establish an homogeneous and replicable long-term post-operative follow-up.

This study demonstrated that clinical healing can be achieved in over half of patients with CAF using RFT following previous surgical treatment, with no reported adverse events and no impact on continence.

It is essential to conduct follow-up assessments for at least six months post-surgery, and future studies should aim for a 12-month follow-up to provide a more comprehensive understanding of treatment outcomes.

While the findings of this study are reassuring and encouraging, they must be interpreted within the context of high failure rate of any CAF and the significant risk of continence disturbances. Therefore, larger studies with adequate follow-up periods are necessary before definitive conclusions can be drawn. Nonetheless, the information provided here will be invaluable at the time of discussing CAF surgery with patients, allowing the establishment of realistic expectations and providing reassurance regarding the minor long-term impact on function.

Author Contribution

Dr. Maya and Dr. Spada made the research and wrote the manuscriptDr. Cirera translate the manuscript to englishDr. Maya and Dr. Cirera prepared figures and tablesDra. Maya recorded the surgical procedure and create de supplementary videoDr. Pellino, Dr. Espín and Dr. Martí reviewed the manuscript

Conflict of interest: The authors declare no conflict of interests in relation with this manuscript.

Source of funding: No funding was received for the current manuscript.

Ethical statement: This study complied with the declaration of Helsinki. All patients provided written informed consent before undergoing the surgical procedures. The study was approved by the Ethical Committee of the Vall d’Hebron University Hospital.

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No competing interests reported.

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Supplementary Material Supplementary Video 1. Surgical procedure

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You are reading this latest preprint version

Long-term outcomes of a bioactive matrix enriched with an autologous platelet concentrate for the treatment of complex anal fistulae

Status:

Version 1

Abstract

Background

Methods

Results

Conclusions

Figures

Introduction

Methods

Inclusion and exclusion criteria

Definitions

Endpoints and outcome measures

Surgical technique and RFT treatment

Postoperative management and follow-up schedule

Ethics

Statistical analysis

Results

Population Characteristics and Previous Procedures

Primary Outcome: Fistula Healing

Secondary Outcomes

Discussion

Study Limitations and Strengths

Conclusions

Declarations

Author Contribution

References

Additional Declarations

Supplementary Files

Status:

Version 1