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When the Bone Flap Expands Like Bellows of Accordion: Feasibility Study Using Novel Technique of Expansile (Hinge) Craniotomy for Severe Traumatic Brain Injury
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.325310
Keywords: Decompressive craniectomy, expansile (hinge) craniotomy, Glasgow outcome scale, intracranial volume, severe traumatic brain injuryKey Message: The EC results in circumferential expansion. The EC is a safe and noninferior alternative to DC in the management of brain swelling. The ICV expansion obtained is comparable to that obtained with DC. The complications due to EC are less.
Traumatic brain injury (TBI) frequently results in severe brain edema and rise in intracranial pressure (ICP). Decompressive craniectomy (DC) has been an important salvage strategy in the neurosurgeon's armamentarium to combat against the detrimental effects of the severe brain swelling. The concept of DC has undergone rigorous scrutiny in terms of translation of logic to reality and its effects on patient outcomes.[1] As with all surgical procedures, it is not free of complications.[2] In addition, it necessitates a second surgical procedure called cranioplasty, which in turn has its own set of complications.[3] A recently published consensus guideline for DC continues to value utility of the technique in controlling intracranial hypertension, albeit with some ambiguity regarding timing and indications.[4] Hinge craniotomy (HC) or expansile craniotomy (EC) is a technique that allows for a degree of decompression while retaining the bone flap in situ, in a “floating” or “hinged” fashion. This provides expansion potential for ensuing cerebral oedema while obviating the need for cranioplasty in the future. The exact indications, technique, and outcomes of this procedure have yet to be determined, but it is likely that HC provides an alternative technique to DC in certain contexts.[5] To this goal, we performed a feasibility study on a novel technique of EC which would provide the swollen brain, space to expand, while the bone flap remains in situ. We propose to describe a noninferior technique that may be effectively utilized in situations requiring standard DC. That way, we hypothesize that one would have benefits of decompression while obviating the need and complications of bone flap removal and cranioplasty.
This prospective study was conducted in patients treated surgically for severe TBI from 2014 through 2017 at major neurotrauma center. The study was in accordance with the Institutional Human Ethics Committee Guidelines. The main aim of the study was to look at the feasibility of EC as an alternative to DC. Adult patients between 18 and 65 years of age with TBI and requiring large DC for evacuation of a traumatic intradural mass lesion like a contusion, intracerebral hemorrhage, and acute subdural hemorrhage or severe cerebral edema causing midline shift or effacement of basal cisterns were screened. The indication for surgical intervention was based on commonly accepted standard practices and the decision was made jointly by chief resident of neurosurgery and consultant neurosurgeon on call. ICP monitoring was not performed in the current study. The consent for surgery was taken from the next available kin. The next available kin were explained about all the variations of surgical procedures including craniotomy with replacement of bone flap if brain is not bulging, and DC or EC depending on the brain bulge at the end of surgery. The decision to randomize to either procedure was taken when the brain was bulging out of the inner table. At our institute, if the brain is bulging out of the inner table, a DC is performed. For this study, such case was randomized to either DC or EC. If the brain was below the inner table after evacuation of intracranial hematoma, the bone flap was replaced. If the brain was bulging out of the outer table, requiring rapid rescue scalp closure then the bone flap was not replaced leading to DC. The patients who underwent primary bone flap replacement or underwent DC due to severe brain bulge requiring quick rescue scalp closure were excluded. In 80 patients in whom the brain was bulging out of the inner table of the skull, the decision to perform DC or EC was based on consecutive intraoperative allocation as outlined in [Figure 1].
Surgical technique of EC A large frontotemporoparietal question mark scalp flap (trauma flap) was raised and large craniotomy of at least 15 × 12 cm was performed. The temporal base was completely nibbled off from the sphenoid ridge up to the root of zygoma. Durotomy was done and mass lesion, if any, was removed. The bulging brain was closed using pericranium, and an augmentative duraplasty was done. The bone flap was divided into three pieces, with oblique and beveled cuts to prevent the bone strips from settling down after the subsidence of edema. The individual bone pieces were loosely tied with no. 1 linen/silk threads passed through peripheral holes. The bones at the margins of the craniotomy were tied loosely to the skull with no. 1 linen/silk threads passing through the multiple peripheral holes both on the bone flap as well as on the fixed skull [Figure 2]a and [Figure 2]b. Ease of scalp closure was assessed. It was ensured that the edematous brain was not compressed and the scalp was closed without undue tension. If required, additional peripheral subgaleal dissection was done to mobilize scalp flap. Galea and skin were closed in standard fashion, and a subgaleal drain was placed.
Postoperative evaluation A computerized tomography (CT) scan of the head was performed electively 6–8 h after surgery or earlier if clinically indicated. The postoperative CT scan was evaluated for reduction of midline shift and opening of basal cisterns. Intracranial volume (ICV) assessment was done using the planning station iPlan Cranial 3.0.6 (Brainlab®, Munich, Germany). The pre- and postoperative CT scans were studied and ICV was calculated. It was done with a semiautomated segmentation with additional manual adjustments. In the EC group, ICV within the bone boundary was marked on individual slices up to the medulla. In the DC group, ICV was marked up to the “dural line” on CT scans. The muscle and skin were excluded [Figure 2]c, [Figure 2]d, [Figure 2]e, [Figure 2]f. Pre-op and post-op volumes were obtained and tabulated. Outcome assessment All patients were assessed clinically and radiologically at discharge, 3 months, 6 months, and 1 year postoperatively. Bone flap replacement was performed at around 3 months or later if persistent brain bulge was present for patients who underwent DC. A ventriculoperitoneal shunt was done for posttraumatic hydrocephalus if indicated. The primary outcome was the Glasgow Outcome Scale (GOS) score one year after the surgery. The GOS was evaluated independently by neurotrauma research fellows who were well trained in performing the outcome assessment and not involved in the acute TBI management. In cases where patients were unable to schedule in-person visits, telephonic inquiries were carried out to assess GOS. The secondary outcome was increase in ICV measured in the postoperative CT scan of head. Statistical analysis The data were entered and analyzed using SPSS v20.0 (IBM inc. Chicago) software. Chi-square test and independent two-tailed t-test were performed after testing for normality of data. For non-parametric data, Mann-Whitney test was performed. A repeated measure ANOVA with a Greenhouse–Geisser correction was done for determining the change in intracranial volume. After univariate analysis, binary logistic regression and multivariate analysis of covariance were performed to account for confounding factors. Statistical significance was determined at P value <0.05.
A total of 757 patients underwent surgery for TBI during the study period. The brain was lax at the end of surgery and bone flap could be replaced safely in 525 patients. The brain was bulging in 232 patients at the end of surgery. Out of 232, there was a brain bulge. In 152 out of 232 patients, the bulge was severe and out of the outer table of the skull. The bone flap replacement was not possible in these 152 cases leading to a DC. In 80 out of 232 patients, the brain was bulging out of the inner table but not out of the outer table. These 80 patients were randomized to undergo either DC or EC. A total of 67 out of 80 patients were available at 1 year follow-up and were included for analysis [Figure 1]. Out of 67 patients, 31 underwent EC and 36 underwent the standard DC. Both the cohorts were matched in terms of baseline determinants of prognosis in neurotrauma which included the age of the patient, Rotterdam CT scan score at admission, and Glasgow coma scale (GCS) at admission [Table 1]. Though the age of the patients who underwent EC was less than the DC cohort, the difference was not significant. The average operative times were comparable (around 2.7 hours) with either procedure.
Intracranial volume The preoperative ICVs were comparable in both the cohorts (P = 0.69), as also the postoperative volumes (P = 0.65). The extent of ICV expansion obtained by EC and DC were comparable. The ANOVA with a Greenhouse–Geisser correction determined that mean volume differed statistically, between pre-op and post-op {F (1,65) =95.546, P < 0.0001} of the entire cohort. The interaction effect of the pre–post group did not show any statistical significance between EC and DC group (P = 0.79). Therefore, it can be concluded that there is a statistically significant increase in ICV postsurgery irrespective of the mode of treatment [Table 1]. Functional outcomes at 1-year Only those patients whose 1-year follow-up record was available were included in the analysis. In EC group, 1-year GOS was available for 27 out of 31 patients (87.1%). There were six known deaths overall by the end of the first year (23.1% mortality rate) and all but one occurred within 3 months of trauma. In the DC cohort, follow-up rates were better, and 1-year GOS could be administered on 34 out of 36 patients (94.4%). Of those, there were 13 mortalities, which occurred in the early perioperative period itself. In EC group, 18 out of 27 (66.7%) had favorable outcome (good recovery or moderate disability), whereas in the DC group 16 out of 34 (47.1%) had favorable outcome. The difference in outcome between EC and DC group was not significantly different (P = 0.126) [Figure 3]. The results of the binary logistic regression analysis after adjusting the age of covariates and GCS, which appeared apparently different in univariate analysis, was done [Table 2]. The difference in the outcome was still not significantly different between the EC and DC group (P = 0.45).
Complications and cosmetic outcome We also looked into the incidence of wound complications and subgaleal collection, hydrocephalus requiring CSF diversion, troublesome sunken flap syndrome, and cosmetic failures in both the cohorts [Table 3]. Complication rates did not differ significantly between the groups. After DC, four patients required titanium mesh cranioplasty for bone flap infection (one abdominal bone flap infection and three after autologous cranioplasty). The cosmetic failure was defined as lack of smooth symmetrical contour at follow-up (after cranioplasty in the DC group). The three cosmetic failures that did occur in EC were due to nonbeveled bone strips, which led to overriding of bone strips on each other and resulting in the settling of individual bone strips when the cerebral edema subsided. We therefore attribute this to inattention to detail and poor execution of the surgical technique rather than the failure of the technique itself.
The role of surgical decompression for the management of raised ICP remains controversial in view of morbidity associated with the standard DC procedure and the subsequent cranioplasty.[2] The former involve wound complications and CSF leak due to the expanded brain, necessity of a storage site for the bone flap, resorption of bone flap, risk of inadvertent injury to “unprotected” brain, hydrocephalus necessitating CSF diversion prior to cranioplasty, unsightly appearance, psychosocial distress, and sunken flap syndrome.[2] In a busy emergency department of neurosurgery as ours, cranioplasty receives a lower priority. To this are added the cost of implants and the fixation system. Cosmetic outcomes are not always good as there is bone resorption and flattening of parietal convexity in the meantime.[6] Cranioplasty, although a simple surgery, is not free of complications. It may cause seizures, postoperative hematoma, CSF leak, implant malfunction, and infection.[3] Comparison of hinge-like craniotomies with EC in severe TBI In attempts to circumvent problems with DC and cranioplasty, three independent groups had described the technique of “HC” in 2007.[7–9] These techniques described have been comparable between the groups due to the fact that one side (farther from the lesion) of the bone flap was fixed with a 'Y' miniplate (hinge) and screws or anchored to temporalis muscle, while the other side was freely mobile to aid in the brain expansion. For instance, Goettler and Tucci described the “Tucci flap” based on a case series of three patients and reported an estimated expansion of 40 mL.[7] Subsequently, Ko and Segan reported on 13 patients who underwent a similar technique of HC for TBI and three patients for arterial stroke.[8] Later the same year, Schmidt and co-workers reported a similar case series of 25 TBI patients who underwent HC.[9] They estimated that the adequacy of decompression was based on a decrease in midline shift in postoperative CT scans. In 2009, Kenning and co-workers performed a comparative study of HC (n = 20) and DC (n = 30) in patients with malignant intracranial hypertension due to a variety of causes.[10] They performed a similar technique of hinge using a Y-miniplate. The volume expansion was comparable in both the cohorts. In addition to these groups, Adeleye and co-workers employed an osteoplastic craniotomy approach and demonstrated that bone flap anchored on the temporalis muscle without the fixation to the skull allowed for a reasonable expansion.[11] A similar temporalis-based HC was also described by Zaater and coworkers.[12] Recently, a technique similar to EC was described by Guttman and co-workers.[13] In this study which spanned over years, 57 patients underwent “floating anchored craniotomy,” where the bone flap was anchored with loosely tied polyglactin threads. There improvement in ICP was 15.4 ± 7.4 mmHg. There are a few dissimilarities in the above-mentioned procedures. In the case of craniotomy hinged on one side using Y-plate or temporalis muscle, we believe that the expansion occurs only on the nonhinged side and may not be sufficient enough for a circumferential brain expansion. Besides, the brain may get unduly compressed on the hinged side, and therefore the applicability of this technique may be limited to only borderline cases. Though the concept is not new, the EC described in present study allows a circumferential expansion of the edematous brain. Interestingly, this technique allows bone fragments to expand like “bellows of an accordion.” The circumferential expansion of bone is desirable rather that expansion in only one direction as described in classical HC [Figure 4]. Splitting the bone flap into three to four fragments creates an additional 1–1.5 cm gap in between the fragments, which is not possible in anchored (hinged) craniotomy. This could also prove beneficial in conditions of severe brain bulge; however, it warrants detailed investigation in prospective studies. As the edema subsides gradually, these bone pieces settle back over the brain contour [Figure 5]. The key advantage of EC is fixation of the bone pieces loosely using silk threads rather than using rigid miniplates and/or screws, which allow bone flaps to settle as oedema subsides.
Though EC is done with an intention to avoid a second surgery, there is possibility of persistent midline shift following EC. In such cases, the patient requires secondary DC after EC. In our present short series, we did not encounter a case where secondary DC was required. However, in review of literature, only 3.2% required subsequent formal DC.[5] Limitations One of the major limitations was that the randomization was insufficient. However, both the groups were matched for standard predictors of outcome of TBI. An innovation, development, exploration, assessment, and long-term study (IDEAL) methodology is required to validate an alternative or new surgical procedure.[14] According to this methodology, the EC can be considered between stage IIb and III “Exploration” and “Assessment,” i.e., the technique is stable, and is comparable to existing practice (DC). Another limitation was lack of ICP monitoring. As the ICP is not routinely practiced, we did not do ICP monitoring for this study. Instead, we demonstrated that the volume expansion with both techniques was comparable. A standard DC reduces ICP by allowing volume expansion. As the volume expansion was comparable, it indirectly indicates that ICP reduced after both procedures. Although the correlation of volume expansion, postoperative midline shift reversal, and clinical outcomes can provide a reasonable and convincing measure of efficacy and safety of this technique, the addition of ICP monitoring could have provided added knowledge in this regard. The routine ICP monitoring is logistically difficult in many centers in developing country.[15] The current work is a feasibility study and not a rigorous randomized controlled trial. Moreover, results of the current study cannot be considered for routine implementation of EC instead of the standard DC. Nevertheless, our study calls for many centers worldwide to implement the EC and compare their results with DC, and arrive at a meaningful consensus. Such multicentric studies could provide the basis for prospective randomized controlled trials comparing EC versus DC for severe TBI.
Our technique of EC in which bone fragments expand circumferentially appears to be a safe and noninferior alternative to DC in the management of brain swelling due to TBI. The ICV expansion obtained was comparable to that obtained with DC. The long-term clinical outcomes with less complications, and (potentially) reduced health care costs especially in resource-constrained settings can make EC a viable and useful alternative to DC. However, a randomized controlled trial or multicenter study is essential before EC can be adopted as an alternative to DC. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest DIB, DPS, BID, and PJH are collaborators of the National Institute for Health Research (NIHR) Global Health Research Group on Neurotrauma. “This research was commissioned by the National Institute for Health Research (NIHR) Global Health Research Group on Neurotrauma using UK aid from the UK Government. The views expressed in this publication are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.”
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]
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