Optimal Timing of Cranioplasty and Predictors of Overall Complications After Cranioplasty: The Impact of Brain Collapse

Neurosurgery 93:84–94, 2023

The optimal timing of cranioplasty (CP) and predictors of overall postoperative complications are still controversial.

OBJECTIVE: To determine the optimal timing of CP.

METHODS: Patients were divided into collapsed group and noncollapsed group based on brain collapse or not, respectively. Brain collapse volume was calculated in a 3-dimensional way. The primary outcomes were overall complications and outcomes at the 12-month follow-up after CP.

RESULTS: Of the 102 patients in this retrospective observation cohort study, 56 were in the collapsed group, and 46 were in the noncollapsed group. Complications were noted in 30.4% (n = 31), 24 (42.9%) patients in the collapsed group and 7 (15.2%) patients in the noncollapsed group, with a significant difference (P = .003). Thirty-three (58.9%) patients had good outcomes (modified Rankin Scale 0-3) in the collapsed group, and 34 (73.9%) patients had good outcomes in the noncollapsed group without a statistically significant difference (P = .113). Brain collapse (P = .005) and Karnofsky Performance Status score at the time of CP (P = .025) were significantly associated with overall postoperative complications. The cut-off value for brain collapse volume was determined as 11.26 cm 3 in the receiver operating characteristic curve. The DC-CP interval was not related to brain collapse volume or postoperative complications.

CONCLUSION: Brain collapse and lower Karnofsky Performance Status score at the time of CP were independent predictors of overall complications after CP. The optimal timing of CP may be determined by tissue window based on brain collapse volume instead of time window based on the decompressive craniectomy-CP interval.


First Experience With Postoperative Transcranial Ultrasound Through Sonolucent Burr Hole Covers in Adult Hydrocephalus Patients

Neurosurgery 92:382–390, 2023

Managing patients with hydrocephalus and cerebrospinal fluid (CSF) disorders requires repeated head imaging. In adults, it is typically computed tomography (CT) or less commonly magnetic resonance imaging (MRI). However, CT poses cumulative radiation risks and MRI is costly. Ultrasound is a radiation-free, relatively inexpensive, and optionally point-of-care alternative, but is prohibited by very limited windows through an intact skull.

OBJECTIVE: To describe our initial experience with transcutaneous transcranial ultrasound through sonolucent burr hole covers in postoperative hydrocephalus and CSF disorder patients.

METHODS: Using cohort study design, infection and revision rates were compared between patients who underwent sonolucent burr hole cover placement during new ventriculoperitoneal shunt placement and endoscopic third ventriculostomy over the 1-year study time period and controls from the period 1 year before. Postoperatively, trans-burr hole ultrasound was performed in the clinic, at bedside inpatient, and in the radiology suite to assess ventricular anatomy.

RESULTS: Thirty-seven patients with sonolucent burr hole cover were compared with 57 historical control patients. There was no statistically significant difference in infection rates between the sonolucent burr hole cover group (1/37, 2.7%) and the control group (0/57, P = .394). Revision rates were 13.5% vs 15.8% (P = 1.000), but no revisions were related to the burr hole or cranial hardware.

CONCLUSION: Trans-burr hole ultrasound is feasible for gross evaluation of ventricular caliber postoperatively in patients with sonolucent burr hole covers. There was no increase in infection rate or revision rate. This imaging technique may serve as an alternative to CT and MRI in the management of select patients with hydrocephalus and CSF disorders.

Complications associated with early cranioplasty for patients with traumatic brain injury

J Neurosurg 137:776–781, 2022

Cranioplasty is a technically simple procedure, although one with potentially high rates of complications. The ideal timing of cranioplasty should minimize the risk of complications, but research investigating cranioplasty timing and risk of complications has generated diverse findings. Previous studies have included mixed populations of patients undergoing cranioplasty following decompression for traumatic, vascular, and other cerebral insults, making results challenging to interpret. The objective of the current study was to examine rates of complications associated with cranioplasty, specifically for patients with traumatic brain injury (TBI) receiving this procedure at the authors’ high-volume level 1 trauma center over a 25-year time period.

METHODS A single-institution retrospective review was conducted of patients undergoing cranioplasty after decompression for trauma. Patients were identified and clinical and demographic variables obtained from 2 neurotrauma databases. Patients were categorized into 3 groups based on timing of cranioplasty: early (≤ 90 days after craniectomy), intermediate (91–180 days after craniectomy), and late (> 180 days after craniectomy). In addition, a subgroup analysis of complications in patients with TBI associated with ultra-early cranioplasty (< 42 days, or 6 weeks, after craniectomy) was performed.

RESULTS Of 435 patients identified, 141 patients underwent early cranioplasty, 187 patients received intermediate cranioplasty, and 107 patients underwent late cranioplasty. A total of 54 patients underwent ultra-early cranioplasty. Among the total cohort, the mean rate of postoperative hydrocephalus was 2.8%, the rate of seizure was 4.6%, the rate of postoperative hematoma was 3.4%, and the rate of infection was 6.0%. The total complication rate for the entire population was 16.8%. There was no significant difference in complications between any of the 3 groups. No significant differences in postoperative complications were found comparing the ultra-early cranioplasty group with all other patients combined.

CONCLUSIONS In this cohort of patients with TBI, early cranioplasty, including ultra-early procedures, was not associated with higher rates of complications. Early cranioplasty may confer benefits such as shorter or fewer hospitalizations, decreased financial burden, and overall improved recovery, and should be considered based on patient-specific factors.


Customized cost‑effective polymethylmethacrylate cranioplasty: a cosmetic comparison with other low‑cost methods of cranioplasty

Acta Neurochirurgica (2022) 164:655–667

Intraoperative hand-moulded cranioplasty and polymethylmethacrylate (PMMA) prostheses made from bone impressions are economical but the cosmetic results are less than satisfactory. Commercially available customized prostheses perform better but are prohibitively expensive. We evaluate the performance of a locally developed, low-cost customized PMMA cranioplasty prosthesis.

Objective To compare the cosmetic outcome of 3 types of PMMA cranioplasty as well as with objective measurements on postoperative CT scans

Methods This study includes 70 patients who underwent cranioplasty between March 2016 and June 2020. In this period, patients had their cranioplasty prostheses made by intra-operative hand moulding (HM), by using the removed bone as a template and making a bone impression (BI) or by 3D printing the prosthesis based on a CT scan. Cosmetic outcomes were assessed by the patient and the operating surgeon on an 8-point scale. The degree of measured anthropometric asymmetry was measured on a postoperative CT scan and correlated with the cosmetic outcome.

Results Our locally produced 3D-printed cranioplasty prostheses showed a statistically better performance in cosmetic scores when compared to the HM and BI (p value < 0.001). CT anthropometric measurements significantly correlated with cosmetic outcome (p value 0.01)

Conclusion Our 3D cranioplasty prostheses had better cosmetic outcomes than HM and BI prostheses, and our technique is able to produce them at 10% of the cost of the currently available commercial customized prostheses.

Complications of Cranioplasty in Relation to Material: Systematic Review, Network Meta-Analysis and Meta-Regression

Neurosurgery 89:383–394, 2021

Cranioplasty is a ubiquitous neurosurgical procedure consisting of reconstruction of a pre-existing calvarial defect. Many materials are available, including polymethylmethacrylate in hand-moulded (hPMMA) and prefabricated (pPMMA) form, hydroxyapatite (HA), polyetheretherketone (PEEK) and titanium (Ti). OBJECTIVE: To perform a networkmeta-analysis (NMA) to assess the relationship between materials and complications of cranioplasty.

METHODS: PubMed/MEDLINE, Google Scholar, EMBASE, Scopus, and The Cochrane Library were searched from January 1, 1990 to February 14, 2021. Studies detailing rates of any of infections, implant exposure, or revision surgery were included. A frequentist NMA was performed for each complication. Risk ratios (RRs) with 95% CIs were calculated for each material pair.

RESULTS: A total of 3620 abstractswere screened and 31 full paperswere included. Surgical revision was reported in 18 studies and occurred in 316/2032 cases (14%; 95% CI 11-17). PEEK had the lowest risk of re-operation with a rate of 8/157 (5%; 95% CI 0-11) in 5 studies, superior to autografts (RR 0.20; 95% CI 0.07-0.57), hPMMA (RR 0.20; 95% CI 0.07-0.60), Ti (RR 0.39; 95% CI 0.17-0.92), and pPMMA (RR 0.14; 95% CI 0.04-0.51). Revision rate was 131/684 (19%; 95% CI 13-25; 10 studies) in autografts, 61/317 (18%; 95%CI 9-28; 7 studies) in hPMMA, 84/599 (13%; 95% CI 7-19; 11 studies) in Ti, 7/59 (9%; 95% CI 1-23; 3 studies) in pPMMA, and 25/216 (12%; 95%CI 4-24; 4 studies) in HA. Infection occurred in 463/4667 (8%; 95%CI 6-11) and implant exposure in 120/1651 (6%; 95% CI 4-9).

CONCLUSION: PEEK appears to have the lowest risk of cranioplasty revision, but further research is required to determine the optimal material.

Cranioplasty following ventriculoperitoneal shunting: lessons learned

Acta Neurochirurgica (2021) 163:441–446

Cranioplasty (CP) is considered as a straightforward and technically unchallenging operation; however, complication rates are high reaching up to 56%. Presence of a ventriculoperitoneal shunt (VPS) and timing of CP are reported risk factors for complications. Pressure gradients and scarring at the site of the cranial defect seem to be critical in this context. The authors present their experiences and lessons learned.

Methods A consecutive series of all patients who underwent CP at the authors’ institution between 2002 and 2017 were included in this retrospective analysis. Complications were defined as all events that required reoperation. Logistic regression analysis and chi-squared test were conducted to evaluate the complication rates according to suspected risk factors.

Results A total of 302 patients underwent cranioplasty between 2002 and 2017. The overall complication rate was 17.5%. Complications included epi-/subdural fluid collection (7.3%) including hemorrhage (4.6%) and hygroma (2.6%), bone graft resorption (5.3%), bone graft infection (2.0%), and hydrocephalus (5.7%). Overall, 57 patients (18.9%) had undergone shunt implantation prior to CP. The incidence of epi-/subdural fluid collection was 19.3% in patients with VPS and 4.5% in patients without VPS, OR 5.1 (95% CI 2.1–12.4). Incidence of hygroma was higher in patients who underwent early CP. Patients with temporary shunt ligation for CP did not suffer from complications.

Conclusion CP in patients with a VPS remains a high-risk procedure. Any effort to understand the pressure dynamics and to reduce factors that may trigger the formation of a large epidural space must be undertaken.

Tonsillectomy with modified reconstruction of the cisterna magna with and without craniectomy for the treatment of adult Chiari malformation type I with syringomyelia

Acta Neurochirurgica (2020) 162:1585–1595

In light of the controversies regarding the surgical treatment of adult Chiari malformation type I (CM-I) with syringomyelia, a retrospective study was conducted to evaluate the safety and efficacy of tonsillectomy followed by modified reconstruction of the cisterna magna with or without craniectomy.

Methods Between 2008 and 2017, 78 adult CM-I patients (36 males and 42 females, mean age 40.6 years old) with syringomyelia were treated with posterior fossa decompression (PFD) with tonsillectomy and modified reconstruction of the cisterna magna. Patients were divided into two study groups: group A (n = 40) underwent cranioplasty with replacement of the bone flap; group B (n=38) underwent suboccipital craniectomy. Neurological outcomes were evaluated by traditional physician assessment (improved, unchanged, and worsened) and the Chicago Chiari Outcome Scale (CCOS). Syringomyelia outcomes were assessed radiologically.

Results The procedure was successfully performed in all patients, and restoration of normal cerebrospinal fluid (CSF) flow was confirmed by intraoperative ultrasonography. The median postoperative follow-up was 20.3 months (range 18– 60 months). Clinical improvement was evident in 66 (84.6%) patients, with no significant differences between the two groups (85.0% vs. 84.2%, P = 0.897). According to the CCOS, 36 patients (90.0%) in group A were labeled as “good” outcome, compared with that of 34 (86.8%) in group B (P = 0.734). Improvement of syringomyelia was also comparable between the groups, which was observed in 35 (87.5%) vs. 33 (86.8%) patients (P = 0.887). The postoperative overall (7.5% vs. 23.7%, P = 0.048) and CSF-related (2.5% vs. 18.4%, P = 0.027) complication rates were significantly lower in group A than group B.

Conclusions Tonsillectomy with modified reconstruction of the cisterna magna without craniectomy seems to be a safe and effective surgical option to treat adult CM-I patients with syringomyelia, though future well-powered prospective randomized studies are warranted to validate these findings.

Biomechanics of a novel reversibly expandable dynamic craniotomy bone flap fixation plate

J Neurosurg 132:560–567, 2020

Biomechanical evaluation of a novel expandable cranial fixation plate was assessed in cadavers. The dynamic craniotomy procedure uses low-profile reversibly expandable plates that allow cranial decompression by providing for intracranial volume expansion without removal of the bone flap. The plates allow reversible outward movement of the bone flap upon an increase in intracranial pressure (ICP) and also retract the bone flap and prevent it from sinking inside the cranium once the ICP normalizes.

METHODS A comparative evaluation of the extent of ICP control with an increase in intracranial volume between various bone flap fixation techniques was undertaken along with testing of the expandable plate compliance. Static compression tests of the plates were performed to assess bone flap fixation and prevention of sinking. Quasi-static shear tension testing of the plates was undertaken to test the tolerance of the plates for expansion. Fatigue shear tension evaluation of the plates was undertaken to assess tolerance for repetitive expansion and contraction.

RESULTS The dynamic craniotomy provided superior control of ICP with an increase in intracranial volume compared to the hinged craniotomy and standard craniotomy techniques (p < 0.001). Static compression results revealed that the plates withstood bone flap sinkage with a mean peak load of 643.3 ± 26.1 N and a mean inward bone flap displacement of 1.92 ± 0.09 mm. Static shear tension results indicated that the plates could withstand a peak expansion of 71.6 mm. Dynamic shear tension testing of the plates with repetitive 15-mm outward expansion and retraction for a total of up to 500 cycles revealed no cracking and no failure points.

CONCLUSIONS The reversibly expandable plates provide for a low-profile bone flap fixation with rigid restriction of bone flap sinking and also enable cranial decompression with a high tolerance for repetitive expansion and contraction.

Evaluation of neurosurgical implant infection rates and associated pathogens: evidence from 1118 postoperative infections

Neurosurg Focus 47 (2):E6, 2019

Various implanted materials are used in neurosurgery; however, there remains a lack of pooled data on infection rates (IRs) and infective bacteria over past decades. The goal of this study was to investigate implant infections in neurosurgical procedures in a longitudinal retrospective study and to evaluate the IRs of neurosurgically implanted materials and the distribution of pathogenic microorganisms.

METHODS A systematic literature search was conducted using PubMed and Web of Science databases for the time period between 1968 and 2018. Neurosurgical implant infections were studied in 5 subgroups, including operations or diseases, implanted materials, bacteria, distribution by country, and time periods, which were obtained from the literature and statistically analyzed. In this meta-analysis, statistical heterogeneity across studies was tested by using p values and I2 values between studies of associated pathogens. Egger’s test was used for assessing symmetries of funnel plots with Stata 11.0 software. Methodological quality was assessed to judge the risk of bias according to the Cochrane Handbook.

RESULTS A total of 22,971 patients from 227 articles satisfied the study’s eligibility criteria. Of these, 1118 cases of infection were reported, and the overall IR was 4.87%. In this study, the neurosurgical procedures or disorders with the top 3 IRs included craniotomy (IR 6.58%), cranioplasty (IR 5.89%), and motor movement disorders (IR 5.43%). Among 13 implanted materials, the implants with the top 3 IRs included polypropylene-polyester, titanium, and polyetheretherketone (PEEK), which were 8.11%, 8.15%, and 7.31%, respectively. Furthermore, the main causative pathogen was Staphylococcus aureus and the countries with the top 3 IRs were Denmark (IR 11.90%), Korea (IR 10.98%), and Mexico (IR 9.26%). Except for the low IR from 1998 to 2007, the overall implant IR after neurosurgical procedures was on the rise.

CONCLUSIONS In this study, the main pathogen in neurosurgery was S. aureus, which can provide a certain reference for the clinic. In addition, the IRs of polypropylene-polyester, titanium, and PEEK were higher than other materials, which means that more attention should be paid to them. In short, the total IR was high in neurosurgical implants and should be taken seriously.

Subcutaneous bone flap storage after emergency craniectomy: cost-effectiveness and rate of resorption

J Neurosurg 129:1604–1610, 2018

Decompressive craniectomy is used for uncontrolled intracranial pressure in traumatic brain injury and malignant hemispheric stroke. Subcutaneous preservation of the autologous bone flap in the abdomen is a simple, portable technique but has largely been abandoned due to perceived concerns of resorption. The authors sought to characterize their experience with subcutaneous preservation of the bone flap and cranioplasty.

METHODS The authors performed a retrospective single-institution review of subcutaneous preservation of the autologous bone flap after decompressive craniectomy from 2005 to 2015. The primary outcome was clinically significant bone resorption, defined as requiring a complete mesh implant at the time of cranioplasty, or delayed revision. The outcome also combined cases with any minor bone resorption to determine predictors of this outcome. Logistic regression modeling was used to determine the risk factors for predicting resorption. A cost comparison analysis was also used via the 2-sided t-test to compare the cost of cranioplasty using an autologous bone flap with standard custom implant costs.

RESULTS A total of 193 patients with craniectomy were identified, 108 of whom received a cranioplasty. The mean time to cranioplasty was 104.31 days. Severe resorption occurred in 10 cases (9.26%): 4 were clinically significant (2 early and 2 late) and 6 demonstrated type II (severe) necrosis on CT, but did not require revision. Early resorption of any kind (mild or severe) occurred in 28 (25.93%) of 108 cases. Of the 108 patients, 26 (24.07%) required supplemental cranioplasty material. Late resorption of any kind (mild or severe) occurred in 6 (5.88%) of 102 cases. Of these, a clinically noticeable but nonoperative deformity was noted in 4 (3.92%) and minor (type I) necrosis on CT in 37 (37%) of 100. Bivariate analysis identified fragmentation of bone (OR 3.90, 95% CI 1.03–14.8), shunt-dependent hydrocephalus (OR 7.97, 95% CI 1.57–40.46), and presence of post-cranioplasty drain (OR 9.39, 95% CI 1.14–1000) to be significant risk factors for bone resorption. A binary logistic regression optimized using Fisher’s scoring determined the optimal multivariable combination of factors. Fragmentation of bone (OR 5.84, 95% CI 1.38–28.78), diabetes (OR 7.61, 95% CI 1.37–44.56), and shunt-dependent hydrocephalus (OR 9.35, 95% CI 1.64–56.21) were found to be most predictive of resorption, with a C value of 0.78. Infections occurred in the subcutaneous pocket in 5 (2.60%) of the 193 cases and after cranioplasty in 10 (9.26%) of the 108 who underwent cranioplasty. The average cost of cranioplasty with autologous bone was $2156.28 ± $1144.60 (n = 15), and of a custom implant was $35,118.60 ± $2067.51 (3 different sizes; p < 0.0001).

CONCLUSIONS Craniectomy with autologous bone cranioplasty using subcutaneous pocket storage is safe and compares favorably to cryopreservation in terms of resorption and favorably to a custom synthetic implant in terms of cost. While randomized data are required to definitively prove the superiority of one method, subcutaneous preservation has enough practical advantages with low risk to warrant routine use for most patients.


Autologous Cranioplasty is Associated with Increased Reoperation Rate: A Systematic Review and Meta-Analysis

Consensus regarding selection of synthetic versus autologous flap reimplantation for cranioplasty after decompressive craniectomy has not been reached and the multiple factors considered for each patient make comparative analysis challenging. This study examines the association between choice of material and related complications.

METHODS: A systematic literature review and meta-analysis were performed using PubMed for articles reporting delayed cranioplasty after decompressive craniectomy using a cohort design comparing autologous bone and synthetic implants. Extracted data included implant material and incidence of infection, reoperations related to implant, wound complications, and resorption. –

RESULTS: One randomized controlled trial and 11 cohort studies were included for a total of 1586 implants (950 bone, 636 synthetic). Autologous implants had significantly more reoperations than did synthetic implants (n [1586 implants; odds ratio [OR], 1.91; 95% confidence interval [CI], 1.40e2.61). Reoperations were most often because of resorption (54%, n [ 159/295) followed by infection (41%, n [ 121/295). The pooled incidence of resorption in autologous implants was 20% (n [ 159/791). Among the other outcomes, there was no significant difference for infections (n [ 1586; OR, 1.24; CI, 0.82e1.88) or wound complications (n [ 678; OR, 0.56; CI, 0.22e1.45). For the trauma subpopulation, there was no significant difference in infection rate with either material (n [ 197; OR, 1.89; CI; 0.59e6.09).

CONCLUSIONS: Autologous implants had significantly more reoperations primarily because of the intrinsic risk of resorption (level of evidence 3b).

Effects of Cranioplasty on Cerebral Blood Flow Following Decompressive Craniectomy

Neurosurgery 81:204–216, 2017

Cranioplasty after decompressive craniectomy (DC) is routinely performed for reconstructive purposes and has been recently linked to improved cerebral blood flow (CBF) and neurological function.

OBJECTIVE: To systematically review all available literature to evaluate the effect of cranioplasty on CBF and neurocognitive recovery.

METHODS: A PubMed, Google Scholar, and MEDLINE search adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines included studies reporting patients who underwent DC and subsequent cranioplasty in whom cerebral hemodynamics were measured before and after cranioplasty.

RESULTS: The search yielded 21 articles with a total of 205 patients (range 3–76 years) who underwent DC and subsequent cranioplasty. Two studies enrolled 29 control subjects for a total of 234 subjects. Studies used different imaging modalities, including CT perfusion (n = 10), Xenon-CT (n = 3), single-photon emission CT (n = 2), transcranial Doppler (n = 6), MR perfusion (n = 1), and positron emission tomography (n = 2). Precranioplasty CBF evaluation ranged from 2 days to 6 months; postcranioplasty CBF evaluation ranged from 7 days to 6 months. All studies demonstrated an increase in CBF ipsilateral to the side of the cranioplasty. Nine of 21 studies also reported an increase in CBF on the contralateral side.Neurological function improved in an overwhelming majority of patients after cranioplasty.

CONCLUSION: This systematic review suggests that cranioplasty improves CBF following DC with a concurrent improvement in neurological function. The causative impact of CBF on neurological function, however, requires further study.

Syndrome of the Trephined: A Systematic Review


Neurosurgery 79:525–534, 2016

Syndrome of the trephined (SoT) is a rare, important complication of a craniectomy characterized by neurological dysfunction that improves with cranioplasty. Its varied symptoms include motor, cognitive, and language deficits. Its exact characterization appears suboptimal, with differing approaches of evaluation. Accordingly, this topic is in great need of further investigation.

OBJECTIVE: To accurately describe SoT and explore methods of an objective diagnosis/ evaluation.

METHODS: Electronic searches of PubMed, MEDLINE, Web of Knowledge, and PsycINFO databases used the key words “syndrome of the trephined” and “sinking skin flap.” Non–English-language and duplicate articles were eliminated. Title and abstract reviews were selected for relevance. Full-text reviews were selected for articles providing individual characteristics of SoT patients.

RESULTS: This review identified that SoT most often occurs in male patients (60%) at 5.1 6 10.8 months after craniectomy for neurotrauma (38%). The average reported craniectomy is 88.3 6 34.4 cm2 and usually exists with a “sunken skin flap” (93%). Symptoms most commonly include motor, cognitive, and language deficits (57%, 41%, 28%, respectively), with improvement after cranioplasty within 3.8 6 3.9 days. Functional independence with activities of daily living is achieved by 54.9% of patients after 2.9 6 3.4 months of rehabilitation. However, evaluation of SoT is inconsistent, with only 53% of reports documenting objective studies.

DISCUSSION: SoT is a variable phenomenon associated with a prolonged time to cranioplasty. Due to current weaknesses in objectivity, we hypothesize that SoT is often underdiagnosed and recommend a multifaceted approach for consistent evaluation.

CONCLUSION: SoT is a serious complication that lacks exact characterization and deserves future investigation. Improved understanding and recognition have important implications for early intervention and patient outcomes.

Cranioplasty after decompressive craniectomy: is there a rationale for an initial artificial bone-substitute implant?

Cranioplasty after decompressive craniectomy

J Neurosurg 124:710–715, 2016

The complication rate for cranioplasty after decompressive craniectomy is higher than that after other neurosurgical procedures; aseptic bone resorption is the major long-term problem. Patients frequently need additional operations to remove necrotic bone and replace it with an artificial bone substitute. Initial implantation of a bone substitute may be an option for selected patients who are at risk for bone resorption, but this cohort has not yet been clearly defined. The authors’ goals were to identify risk factors for aseptic bone flap necrosis and define which patients may benefit more from an initial bone-substitute implant than from autograft after craniectomy.

Methods The authors retrospectively analyzed 631 cranioplasty procedures (503 with autograft, 128 with bone substitute) by using a stepwise multivariable logistic regression model and discrimination analysis.

Results There was a significantly higher risk for reoperation after placement of autograft than after placement of bone substitute; aseptic bone necrosis (n = 108) was the major problem (OR 2.48 [95% CI 1.11–5.51]). Fragmentation of the flap into 2 or more fragments, younger age (OR 0.97 [95% CI 0.95–0.98]; p < 0.001), and shunt-dependent hydrocephalus (OR 1.73 [95% CI 1.02–2.92]; p = 0.04) were independent risk factors for bone necrosis. According to discrimination analysis, patients younger than 30 years old and older patients with a fragmented flap had the highest risk of developing bone necrosis.

Conclusions Development of bone flap necrosis is the main concern in long-term follow-up after cranioplasty with autograft. Patients younger than 30 years old and older patients with a fragmented flap may be candidates for an initial artificial bone substitute rather than autograft.

The Recent Revolution in the Design and Manufacture of Cranial Implants

The Recent Revolution in the Design and Manufacture of Cranial Implants

Neurosurgery 77:814–824, 2015

Large format (ie, .>25 cm2) cranioplasty is a challenging procedure not only from a cosmesis standpoint, but also in terms of ensuring that the patient’s brain will be well-protected from direct trauma.

Until recently, when a patient’s own cranial flap was unavailable, these goals were unattainable. Recent advances in implant computer-aided design and 3-dimensional (3-D) printing are leveraging other advances in regenerative medicine. It is now possible to 3-D-print patient-specific implants from a variety of polymer, ceramic, or metal components.

A skull template may be used to design the external shape of an implant that will become well integrated in the skull, while also providing beneficial distribution of mechanical force in the event of trauma.

Furthermore, an internal pore geometry can be utilized to facilitate the seeding of banked allograft cells. Implants may be cultured in a bioreactor along with recombinant growth factors to produce implants coated with bone progenitor cells and extracellular matrix that appear to the body as a graft, albeit a tissue-engineered graft.

The growth factors would be left behind in the bioreactor and the graft would resorb as new host bone invades the space and is remodeled into strong bone. As we describe in this review, such advancements will lead to optimal replacement of cranial defects that are both patient-specific and regenerative.

Polyetheretherketone Implants for the Repair of Large Cranial Defects

Polyetheretherketone Implants for the Repair of Large Cranial Defects

Neurosurgery 75:523–529, 2014

Calvarial reconstruction of large cranial defects following decompressive surgery is challenging. Autologous bone cannot always be used due to infection, fragmentation, bone resorption, and other causes. Polyetheretherketone (PEEK) is a synthetic material that has many advantages in cranial-repair surgery, including strength, stiffness, durability, and inertness.

OBJECTIVE: To describe our experience with custom-made PEEK implants for the repair of large cranial defects in 3 institutions: San Francisco General Hospital, Hadassah- Hebrew University Hospital, and the National Neuroscience Institute, Singapore.

METHODS: A preoperative high-resolution computed tomography scan was obtained for each patient for design of the PEEK implant. Cranioplasty was performed via standard technique with the use of self-tapping titanium screws and miniplates.

RESULTS: Between 2006 and 2012, 66 cranioplasties with PEEK implants were performed in 65 patients (46 men, 19 women, mean age 35 6 14 years) for repair of large cranial defects. There were 5 infections of implants and 1 wound breakdown requiring removal of the implant (infection and surgical removal rates of 7.6% and 9.1%, respectively). Two patients required drainage of postoperative hematoma (overall surgical complication rate, 12.7%). Nonsurgical complications in 5 patients included seizures, nonoperative collection, and cerebrospinal fluid rhinorrhea that resolved spontaneously. Overall median patient or family satisfaction with the cranioplasty and aesthetic result was good, 4 on a scale of 5. Temporal wasting was the main aesthetic concern.

CONCLUSION: Custom-designed PEEK implants are a good option for patients with large cranial defects. The rate of complications is comparable to other implants or autologous bone. Given the large size of these defects, the aesthetic results are good.

Cranial vault remodeling for sagittal craniosynostosis in older children

Neurosurg Focus 31 (2):E3, 2011,DOI: 10.3171/2011.5.FOCUS1196

Sagittal craniosynostosis is the most common form of craniosynostosis and is commonly treated within the first year of life. Optimal treatment of patients older than 1 year of age is not well characterized. The authors reviewed cases of sagittal craniosynostosis involving patients who were treated surgically at their institution when they were older than 1 year in order to determine the rate of intracranial hypertension (ICH), potential to develop nonhealing cranial defects, and the need for various surgical procedures to treat the more mature phenotype.

Methods. A retrospective chart review was conducted of all cases in the Children’s Hospital of Pittsburgh Neurosurgery Database involving patients who underwent cranial vault remodeling for scaphocephaly after 1 year of age between October 2000 and December 2010.

Results. Ten patients were identified who met the inclusion criteria. Five patients underwent anterior two-thirds cranial vault remodeling procedures, 3 patients underwent posterior vault remodeling, and 2 patients underwent 2-staged total vault remodeling. All patients had improved head shapes, and mean cephalic indices improved from 65.4 to 69.1 (p = 0.05). Six patients exhibited signs of ICH. No patients with more than 3 months of follow-up exhibited palpable calvarial defects.

Conclusions. Patients with sagittal synostosis treated after 1 year of age demonstrate increased rates of ICH, warranting diligent evaluations and surveillance to detect it; rarely develop clinically significant cranial defects if appropriate bone grafting is performed at the time of surgery; and achieve acceptable improvements in head shape.

“In-window” craniotomy and “bridgelike” duraplasty: an alternative to decompressive hemicraniectomy

J Neurosurg 113:982–989, 2010. DOI: 10.3171/2009.11.JNS09674

The object of this study was to propose an alternative procedure to the classic decompressive hemicraniectomy using an “in-window” craniotomy and a “bridgelike” duraplasty.

Methods. The authors performed a large, almost rectangular craniotomy involving the frontal, temporal, and parietal bones and part of the occipital squama in 5 patients. The dura mater is opened and its area is enlarged using a rectangular dural patch of the surgeon’s choice in the form of a bridge between the anterior and posterior dural edges. With a vertical cut, the bone flap is divided into 2 similarly sized pieces that function as “window lids.” The outer frontal and occipital sides of the bone are tied to the skull border at 2 points to function as a hinge joint. The angle of the bone cut must be beveled outward (inclination ~ 45° of the bone drill or saw) to allow the bone flap to rest on the adjacent skull and prevent its slippage toward the intracranial cavity.

Results. The above procedures were performed with effective control of intracranial hypertension due to cerebral venous sinus thrombosis, brain trauma, intracerebral hematoma, or malignant cerebral ischemia.

Conclusions. Decompressive surgery, which uses an in-window craniotomy that gradually opens according to the intracranial pressure, is an alternative solution for deploying autologous material. The procedure has the advantage of obviating the need for a second surgical procedure to close the bone defect, and thus preventing the metabolic cerebral impairment associated with the absence of an overlying skull.