Retrospective Study on Complications of Abdominal Subcutaneous Bone Flap Preservation among Patients Undergoing Cranioplasty following Decompressive Craniectomy and Literature Review

Abstract

Background

Following decompressive craniectomy (DC), the excised bone flap can be stored either in vivo (subcutaneously in the abdominal wall or thigh) or extracorporeally (cryopreserved). While bone flap preservation techniques and postcranioplasty outcomes have been extensively studied, complications related to abdominal wall bone flap storage remain underreported. A retrospective study was conducted on 92 patients who underwent DC followed by cranioplasty with subcutaneous abdominal wall bone flap preservation.

Results

The most common abdominal wall complications included psychological concerns (24%), cosmetic concerns (21.7%), pain at the incision site (19.5%), and abdominal wall heaviness (19.5%). Wound infections occurred in 10% of patients, necessitating bone flap removal in two cases. Other complications included difficulty in squatting (20%), breathing difficulty (2%), and wound hematoma (3%).

Discussion

However, abdominal wall complications, including infection, pain, and cosmetic concerns, should be discussed preoperatively with patients and their families. Despite these challenges, abdominal preservation remains an alternative to cryopreservation in neurosurgical centers with limited infrastructure for bone banking.

Conclusion

Abdominal subcutaneous bone flap preservation following DC is associated with a range of complications, though most are manageable with conservative measures. Autologous bone flap storage in the abdominal wall remains a viable option, particularly in high-volume and resource-constrained settings, due to its cost-effectiveness, biocompatibility, and reduced risk of bone resorption compared with cryopreservation. Given its efficacy and cost advantages, it remains a relevant choice in select settings.

 

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Keywords

decompressive craniectomy - cranioplasty - bone flap preservation - abdominal wall complications - in vivo bone storage

Introduction

Decompressive craniectomy (DC) is a neurosurgical intervention made specifically to relieve intracranial pressure in patients who suffer from conditions such as severe traumatic brain injury (TBI), malignant middle cerebral artery infarction, and aneurysmal subarachnoid hemorrhage.[1] [2] DC allows expansion, and the pressure–volume curve shifts to the right after bone removal.[1] [3] [4] Bleeding, new or expanded contusion, extracerebral herniation, fever, wound infection, subdural hygroma, infarction, and hydrocephalus are all common neurosurgical complications during and after a DC,[1] [2] [3] whereas trephine syndrome and bone resorption are relatively late complications.[1] [5] [6] After DC, the excised bone flap can be banked for subsequent reimplantation in the form of cranioplasty; this procedure is usually performed for the protection of the brain, hydrodynamic equilibrium, and cosmesis.[4] [7] [8] Though post-DC complications are under intense research, associated abdominal wall complications are relatively less discussed. In this article, we intend to discuss the abdominal wall complications associated with DC in this study.

Following bone flap removal, it can be stored in vivo in the subcutaneous plane of the anterior abdominal wall or anterior thigh. Even though it needs an additional procedure, the self-proclaimed justification for in vivo bone flap preservation in the abdominal subcutaneous plane includes that the modality of autologous bone flap storage is cost-effective, with no requirements for additional machinery or personnel, which would be challenging in a high-volume center.[4] [9] There are few studies suggesting postcranioplasty bone resorption in patients who had their bone cryopreserved.[5] [9] [10]

Even though cryopreservation is being practiced more often lately, abdominal subcutaneous preservation is still a cost-effective and accessible method, but not without its complications, especially in high-volume or resource-poor settings. This study evaluates the complications of the abdominal wall after the subcutaneous preservation of the bone flaps compared with those that present concerning cryopreservation and other in vivo methods.

 

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Aim of the Study

This study aims to investigate the abdominal wall complications following DC with subcutaneous bone flap preservation and to review the associated literature.

 

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Review of Literature

For centuries, the notion of relieving intracranial pressure by surgical means was known, but advances in neurosurgery, critical care, and neuroimaging paved the way for the modern evolution of DC.[11] [12] Though DC can be lifesaving, the long-term outcomes have been the subject of much debate. Most surviving patients succumb to severe disabilities, raising ethical questions regarding the quality of survival.[13] Current research emphasizes better patient selection criteria and improvement in functional outcomes at the time of discharge.[14] Future developments in DC include the introduction of minimally invasive techniques, better biomaterials for skull reconstruction, and improved neuroprotective strategies that eliminate or reduce secondary brain injury after the procedure.

Preservation of the bone flap is important for maintaining the protective and esthetic functions of the skull once the patient's neurological condition becomes stable and intracranial pressure normalizes. Over the years, different techniques for bone flap preservation have been developed and studied, each with its advantages, disadvantages, and potential complications. Autologous bone flap preservation is still the major option for cranioplasty due to its perceived biocompatibility and low cost.[15] Then, in the middle of the 20th century, more controlled procedures emerged for the storage of the bone, including autologous storage and cryopreservation—whose techniques have been perfected over time, with continuing research on the validity of effectiveness in preventing infections, resorptions, and other complications.[4] [9]

Today, several approaches to bone flap preservation are employed, each with unique benefits and limitations. These techniques are broadly categorized into autologous preservation methods and extracorporeal preservation methods.

Preservation of Autologous Bone Flap

Subcutaneous Pocket Preservation (Anterior Thigh or Abdominal)

In subcutaneous pocket preservation, the resected bone flap is placed in a subcutaneous pocket, mainly in the abdominal wall. It has several benefits, including a reduced chance of infection as the bone is kept in the patient's own body, and the external contamination risk is reduced. Another benefit is biocompatibility; in most studies, the bone stock retained its biological and structural characteristics after this storage, significantly reducing the possibility of bone resorption upon reimplantation as there is minimal destruction of viable osteoblasts. A study by Movassaghi et al showed that the histology of retrieved bone at the time of cranioplasty showed portions of necrotic bone interspersed with areas of new bone formation. Several studies demonstrate good outcomes with abdominal preservation.[16] A very illustrative study by Schuss et al found less infection and bone flap resorption with this method than with extracorporeal storage methods.[17] However, the abdominal preservation has some potential disadvantages, such as requiring additional surgery to create the subcutaneous pocket, which increases the chance of infection or other complications at the site. Some patients may experience pain or discomfort at the storage site during recovery.

 

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Subgaleal Preservation

In this largely obsolete technique, the bone flap is usually positioned under the galea aponeurotica adjacent to the craniectomy incision over the opposite side of the skull. Subgaleal storage is often argued as less invasive than abdominal storage.[18] Although no second incision is needed, it is risky compared with abdominal storage because the bone flap is closer to the original surgical site and thus poses more chances of infection and other wound complications. If the patient ends up having wound complications, the clinical outcome will be worse, and it made this technique largely obsolete.

 

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Extracorporeal Bone Flap Preservation

Cryopreservation

Storage of bone flaps at −80°C in a deep-freeze environment is called cryopreservation and maintains the structural integrity of the bone flap till reimplantation.[5] [15] The procedure is widely practiced in many neurosurgical centers due to its availability and efficiency. Key advantages include that the bone flaps can be stored for a long time. This is of great value for patients who need a long recovery or rehabilitation period before the cranioplasty since subcutaneously placed bone can have progressive resorption.[19] And the bone flaps preserved by cryopreservation are available and useful for reimplantation without further additional surgical sites, as in the case of autologous methods. It eliminates the need for additional surgery at the time of DC and also cranioplasty. Though rare, when the abdominal wound is opened first to check the condition of the bone flap, cranioplasty may need to be postponed in case the bone flap happens to be unhealthy and results in deferring the cranioplasty. Storage of an extracorporeal flap can save such unwarranted events.

Despite these benefits, cryopreservation also carries the risk of a higher chance of bone flap resorption after reimplantation. There is evidence that postcranioplasty bone resorption is higher compared with autologous storage methods.[5] [19] This results in bone fragility and poor cosmetic results after cranioplasty. In addition, improper handling during storage and reimplantation can lead to contamination and infection. In high-volume, low-resource settings, facilities and infrastructure for cryopreservation and bone banks may not be available, and logistical errors can happen.

Finally, alternatives to autologous bone flaps include polymethyl methacrylate, titanium mesh, custom-made titanium molds, or porous polyethylene implants. They have many advantages, such as minimizing the risk of infection and resorption, and they can be custom-shaped with methods such as three-dimensional printing and other advanced techniques for optimal results in cosmetics and protection. They do not, however, offer biological integration as has been known with autologous bone flaps.

 

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Complications and Outcomes

The most common complications associated with bone flap preservation techniques include infection, resorption, and poor cosmetic results. However, they can occur after any preservation technique, each carrying specific risk factors. Each has varied incidence in various studies. A study by Corliss et al showed no significant difference in the infection rate between in vivo-preserved and cryopreserved bone flaps.[4] Bone flap resorption is a significant problem with cryopreserved bone flaps, especially when storage duration exceeds several months. This is due to the absence of nutritive supply to the bone graft such as the in vivo preservation and progressive loss of osteoblastic activity. Young age, longer duration, and fractures are other factors that can increase bone flap resorption.[4] [5] [19] Cosmetic and functional outcomes have been relatively better for autologous storage methods, especially abdominal preservation because they preserve much of the biological characteristics of the bone tissue postcranioplasty.

 

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Objectives

While complications associated with DC, such as hydrocephalus, wound infections, and bone flap resorption, have been extensively studied, there remains a relative paucity of literature addressing abdominal wall complications arising from in vivo preservation of bone flaps in the subcutaneous plane. In our study, we aim to evaluate and analyze abdominal wall complications following the preservation of bone flaps in the abdominal subcutaneous tissue after DC. This study seeks to shed light on this underexplored area, contributing to a better understanding of the associated risks and outcomes. Our main focus for this research was to assess complications following DC and bone flap preservation in the abdominal wall.

 

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Materials and Methods

This study was conducted in the Department of Neurosurgery, Government Medical College. We studied 92 patients who underwent DC, followed by cranioplasty with the preservation of a bone flap in the abdomen after receiving clearance from the Institutional Review Board and Institutional Ethics Committee. We conducted a record-based retrospective study for 2 years in the Department of Neurosurgery, Government Medical College, Thrissur, from 2022 through 2024.

 

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Data Collection Method and Tools

Data were collected from department records and operative registers in the Department of Neurosurgery, Government Medical College, and with phone interviews if details were insufficient in records. We collected variables such as age, sex, indication for DC, postoperative Glasgow coma scale, side of the surgery, difficulty while squatting, breathing difficulty, heaviness, local pain, psychological problems, wound infection in the abdomen, hematoma, and cosmetic concerns in our study. This is a record-based study; hence, permission was taken from the head of the department and hospital authorities to use details available in the medical records. If the details were not fully available in the available clinical records, details were sought through a phone call, and in such cases, verbal consent was obtained.

Data Analysis

The collected data were inputted on the proforma and later consolidated into the master chart. The results were analyzed using SPSS 22.0. The charted quantitative data and qualitative data were analyzed by descriptive statistics.

 

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Results

During the study period, 92 patients underwent cranioplasty in our department. The mean age of the study population was 44.5 years, with 76% of them being males. TBI was the most common primary pathology for DC (85%), followed by infarct and intraparenchymal hematoma. The mean interval of the cranioplasty period was 3 months ([Table 1]).

Table 1 Patient characteristics and primary pathology

Demographic details
Mean age (range)	44.5 (18–72)
Sex: male, n (%)	70 (76)
Primary pathology, n (%)
Trauma	78 (85)
Infarct	8 (9)
Intraparenchymal hematoma	4 (4)
Timing of cranioplasty, n (%)
Mean	5.5 mo
< 6 wk	1 (1)
6 wk–3 mo	18 (20)
3–6 mo	53 (58)
> 6 mo	20 (21)

Complications Associated with Abdominal Flap

The data were selected using record reviews and phone interviews with patients awaiting cranioplasty surgery following DC. Eighteen patients had wound site pain in the immediate postoperative period; 9 patients had wound infections in the abdominal flap site out of which 2 bone flaps were removed and were planned for cranioplasty with exogenous implant at a later date; 19 patients had abdominal wall heaviness at the wound site; 20 patients had cosmetic concerns regarding flap site incision; and 19 patients had some psychological issues. Other complications are depicted in [Table 2].

Table 2 Complications associated with abdominal flap, n (%)

Pain	18 (19.5%)
Difficulty in squatting	19 (20%)
Breathing difficulty	2 (2%)
Abdominal wall heaviness	18 (19.5%)
Wound infection	9 (10%)
Psychological concerns	22 (24%)
Cosmetic concerns	20 (21.7%)
Wound hematoma	3 (3%)

 

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Discussion

The removed bone flap after DC is stored in the subcutaneous plane in the anterior abdomen or the thigh, or extracorporeally in the bone biobank. Even though there is a tendency to shift to cryopreservation in recent literature, autologous preservation still has advantages such as biocompatibility, low cost, a perfect match in terms of fit and curvature, and immunological tolerance.[20] [21] [22] [23] [24] Even though many studies are comparing different storage techniques on the outcome of cranioplasty in terms of infections, bone flap resorption, etc., there is a relative paucity of literature studying abdominal wall complications following bone flap preservation. In our study, we tried to address this lacuna. In our study group, there were no significant complications except for wound infection in the abdominal site in nine patients. Of which seven patients were treated conservatively. In two patients, the infected bone flap had to be removed, and the wound was closed with a drain. The other complications such as pain are treated successfully with conservative measures. Psychological and cosmetic concerns were managed with counseling and reassurance.

 

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Conclusion

As there were no significant complications following abdominal flap preservation and comparable safety with cryopreservation, it remains a valid choice in high-volume and resource-constrained settings due to its low cost and comparable efficacy. Additional logistical errors and the cost of biobanks for bone preservation can also be avoided.

Even so, the need for an additional procedure and surgical site should be discussed with patients and relatives, and options for biobanking should be offered if available. We need further studies to evaluate the complications and outcomes of in vivo preservation in a larger population. The bone flap resorption and new bone formation are to be studied in subcutaneously preserved bone flaps.

 

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Conflict of Interest

None declared.

Ethical Approval

The study was approved by the Institutional Review Board and Institutional Ethics Committee (IEC No.: IEC/GMCTSR/2024/087).

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Publication History

Article published online:
09 April 2025