What happens to the bone flap? Long-term outcome after reimplantation of cryoconserved bone flaps in a consecutive series of 92 patients

Bone Regeneration and Polyetheretherketone Implants in Maxillo-Facial Surgery and Neurosurgery: A Multidisciplinary Study

Polyetheretherketone (PEEK) in the last few years has emerged as an exceedingly promising material for craniofacial defects due to its biocompatibility and mechanical properties. However, its utilization remains controversial due to its inertness and low osteoinductivity. This study aimed to investigate the postoperative outcomes of patients undergoing maxillo-facial and neurosurgical procedures with PEEK implants. The focus is on evaluating bone regrowth on the surface and edges of the implant, periosteal reactions, and implant positioning. A retrospective analysis of 12 maxillo-facial surgery patients and 10 neurosurgery patients who received PEEK implants was conducted. CT scans performed at least one year post operation were examined for bone regrowth, periosteal reactions, and implant positioning. In maxillo-facial cases, the analysis included mandibular angle and fronto-orbital reconstruction, while neurosurgical cases involved cranioplasty. In maxillofacial surgery, 11 out of 12 patients showed radiological evidence of bone regrowth around PEEK implants, with favorable outcomes observed in craniofacial reconstruction. In neurosurgery, 9 out of 10 patients exhibited minimal or none bone regrowth, while one case demonstrated notable bone regeneration beneath the PEEK implant interface. The study highlights the importance of implant design and patient-specific factors in achieving successful outcomes, providing valuable insights for future implant-based procedures.

Decompressive craniectomy plus best medical treatment versus best medical treatment alone for spontaneous severe deep supratentorial intracerebral haemorrhage: a randomised controlled clinical trial

BACKGROUND

It is unknown whether decompressive craniectomy improves clinical outcome for people with spontaneous severe deep intracerebral haemorrhage. The SWITCH trial aimed to assess whether decompressive craniectomy plus best medical treatment in these patients improves outcome at 6 months compared to best medical treatment alone.

METHODS

In this multicentre, randomised, open-label, assessor-blinded trial conducted in 42 stroke centres in Austria, Belgium, Finland, France, Germany, the Netherlands, Spain, Sweden, and Switzerland, adults (18-75 years) with a severe intracerebral haemorrhage involving the basal ganglia or thalamus were randomly assigned to receive either decompressive craniectomy plus best medical treatment or best medical treatment alone. The primary outcome was a score of 5-6 on the modified Rankin Scale (mRS) at 180 days, analysed in the intention-to-treat population. This trial is registered with ClincalTrials.gov, NCT02258919, and is completed.

FINDINGS

SWITCH had to be stopped early due to lack of funding. Between Oct 6, 2014, and April 4, 2023, 201 individuals were randomly assigned and 197 gave delayed informed consent (96 decompressive craniectomy plus best medical treatment, 101 best medical treatment). 63 (32%) were women and 134 (68%) men, the median age was 61 years (IQR 51-68), and the median haematoma volume 57 mL (IQR 44-74). 42 (44%) of 95 participants assigned to decompressive craniectomy plus best medical treatment and 55 (58%) assigned to best medical treatment alone had an mRS of 5-6 at 180 days (adjusted risk ratio [aRR] 0·77, 95% CI 0·59 to 1·01, adjusted risk difference [aRD] -13%, 95% CI -26 to 0, p=0·057). In the per-protocol analysis, 36 (47%) of 77 participants in the decompressive craniectomy plus best medical treatment group and 44 (60%) of 73 in the best medical treatment alone group had an mRS of 5-6 (aRR 0·76, 95% CI 0·58 to 1·00, aRD -15%, 95% CI -28 to 0). Severe adverse events occurred in 42 (41%) of 103 participants receiving decompressive craniectomy plus best medical treatment and 41 (44%) of 94 receiving best medical treatment.

INTERPRETATION

SWITCH provides weak evidence that decompressive craniectomy plus best medical treatment might be superior to best medical treatment alone in people with severe deep intracerebral haemorrhage. The results do not apply to intracerebral haemorrhage in other locations, and survival is associated with severe disability in both groups.

FUNDING

Swiss National Science Foundation, Swiss Heart Foundation, Inselspital Stiftung, and Boehringer Ingelheim.

Early detection of aseptic bone necrosis post-cranioplasty: A retrospective CT analysis using Hounsfield units

This study examined the efficacy of computed tomography (CT)-based Hounsfield units (HU) as early predictors of aseptic bone necrosis, a serious post-cranioplasty complication after autologous cranioplasty. In total, 100 patients who underwent decompressive craniectomy and subsequent autologous cranioplasty were included. The radiodensity of the bone flap was evaluated in HU from CT scans at five follow-up timepoints. HU thresholds were established to predict the development of aseptic bone necrosis. HU demonstrated a declining trend throughout the follow-up period in all patients. Necrosis type I patients showed significant differences at all timepoints from 3 months post-procedure onwards, while necrosis type II patients displayed a significant decline in HU at every follow-up. Optimal thresholds with cut-off A (91.23% of initial HU) and cut-off B (78.73% of initial HU) were established to predict the occurrence of bone necrosis and the need for artificial bone replacement, respectively. Our findings demonstrated the utility of CT-based HU measurements as a simple, non-invasive tool for the early prediction of aseptic bone necrosis following autologous cranioplasty. By delineating specific HU thresholds, our study offers a valuable guide for orchestrating timely follow-ups and advising patients on the necessity of proactive interventions.

Autologous Cranioplasty with Bone Flap Preserved in Conventional Freezers: An Adequate Option in Low Resource Settings

BACKGROUND

Autologous cranioplasty has been used for decades and is the gold standard treatment in patients who underwent decompressive craniectomy (DC). One of the most common methods to store the cranial bone flap is cryopreservation at very low temperatures (-70 to -80°). The only way to achieve these low temperatures is by using special freezers which are not always available in all medical facilities, especially in low-resource centers. This paper describes our experience with the storage of cranial bone flaps in freezers of conventional refrigerators.

METHODS

This retrospective study included patients treated with autologous cranioplasty, operated between 2015 and 2020. The cranial bone flap was stored at -18°C in the freezer of conventional refrigerators. Complications and outcomes were analyzed and compared with reports of patients in whom ultra-low temperature freezers were used for bone flap preservation.

RESULTS

Twenty-five patients were included. The average follow-up period was 33 months. Trauma was the most common cause of DC, followed by stroke. The mean age was 36.7. Aseptic bone flap resorption was observed in 4 cases (16%). No cases of infection were observed.

CONCLUSIONS

The use of freezers from conventional refrigerators may be an acceptable alternative for the preservation of the cranial bone flap in facilities where special freezers are not available. The rate of aseptic bone necrosis and infections observed in this paper was similar to the incidence of these complications reported in studies where ultra-low temperatures were used.

Clinical Outcomes After Cranioplasty With Titanium Mesh, Polyetheretherketone, or Composite Bone Cement: A Retrospective Study

Cranioplasty is a common neurosurgical procedure; however, the optimal material choice remains controversial. At the time of this writing, autologous bone, the preferred choice for primary cranioplasty, has a high incidence of complications such as infection and resorption, thus requiring frequent use of synthetic materials. Therefore, this study aimed to compare the clinical benefits of titanium mesh (Ti), polyetheretherketone (PEEK), and composite bone cement (CBC) in cranioplasty to provide a clear selection basis for clinicians and patients. This study retrospectively collected data from 207 patients who underwent cranioplasty with Ti (n=129), PEEK (n=54), and CBC (n=24) between January 2018 and December 2020 at Henan Provincial People's Hospital. Postoperative follow-up information after 6 months was used to compare the long-term effects of the 3 materials on the patients. There were no significant differences in the overall complication rate after cranioplasty among the 3 materials. However, subcutaneous effusion was more frequent with PEEK (24.07%) and CBC (20.83%) than with Ti (2.33%). Second, there were no significant differences in the increase in Glasgow Outcome Scale and Karnofsky Performance Status scores after cranioplasty among the 3 materials. Finally, we found that PEEK had the highest patient satisfaction and hospitalization cost, whereas the opposite was true for Ti. Although the surgical outcomes of the 3 implant materials were similar, an examination of clinical outcomes such as patient satisfaction showed significant differences, deepening people's perceptions of the 3 materials.

Analysis of craniectomy bone flaps stored in a neurosurgical cryopreservation freezer: microorganism culture results and reimplantation rates

BACKGROUND

Cryopreservation of bone flaps after decompressive craniectomies is a common practice. A frequent complication after bone flap reimplantation is postoperative infection, so culturing of frozen craniectomy bone flaps is a crucial practice that can prevent patient morbidity and mortality. Although many studies report on infection rates after cranioplasty, no study reports on the results of bone flaps stored in a cryopreservation freezer, reimplanted or otherwise. We sought to analyze the flaps in our medical center's bone bank freezer, including microorganism culture results and reimplantation rates of cryopreserved bone flaps.

METHODS

Patients who underwent craniectomy and had bone flaps cryopreserved between January 1, 2016, and July 1, 2022, were included in this retrospective study. Information about bone flap cultures and reimplantation or discard was obtained from a prospectively maintained cryopreservation database. Information including infection rates and mortality was acquired from a retrospective review of patient records. Culture results were obtained for all flaps immediately before cryopreservation and again at the time of reimplantation at the operator's discretion.

RESULTS

There were 148 bone flaps obtained from 145 patients (3 craniectomies were bilateral) stored in our center's freezer. Positive culture results were seen in 79 (53.4%) flaps. The most common microorganism genus was Propionibacterium with 47 positive flaps, 46 (97.9%) of which were P. acnes. Staphylococcus was the second most common with 23 positive flaps, of which 8 (34.8%) tested positive for S. epidermidis. Of the 148 flaps, 25 (16.9%) were reimplanted, 116 (78.4%) were discarded, and 7 (4.7%) are still being stored in the freezer. Postcranioplasty infections were seen in 3 (12%) patients who had flap reimplantation.

CONCLUSIONS

Considering the substantial number of positive cultures and limited reimplantation rate, we have reservations about the logistical efficiency of cryopreservation for flap storage. Future multicenter studies analyzing reimplantation predictors could help to reduce unnecessary freezing and culturing.

Ten-Year Institutional Experience to Predict Risk of Calvarial Bone Flap Loss Using Long-Term Outcome Data

BACKGROUND

Calvarial bone flap (CBF) loss is a common complication following craniotomy and subsequent skull reconstruction can be challenging. Defining predictors of CBF failure not only improves patient outcomes but reduces the need for complex reconstruction often requiring plastic surgery consultation. As CBF failure can occur many years following craniotomy, this study aimed to determine risk factors of CBF loss using long-term follow-up.

MATERIALS AND METHODS

This retrospective study included patients who underwent craniotomy with CBF reinsertion between 2003 and 2013 at a tertiary academic institution. Patients were included if demographics, comorbidities, and long-term outcomes were available. Multivariable logistic regression modeled the odds of CBF failure, defined as permanent removal for bone flap-related issues. The median follow-up was 6.9 years (interquartile range: 1.8-10.8 y).

RESULTS

There were 222 patients who met inclusion criteria and underwent craniotomy with CBF reinsertion, primarily for tumor resection or intracranial pressure relief. CBF failure occurred in 76 (34.2%) patients. Up to 4 CBF reinsertions were performed in both failure and nonfailure groups. The risks of CBF loss increased with each additional CBF elevation by 17-fold (P<0.001), male sex by 3-fold (P=0.005), and tumor etiology by 3-fold (P=0.033) (C-index=0.942).

CONCLUSIONS

Each CBF reinsertion dramatically increases the risk of CBF loss. This finding may optimize patient selection and surgical planning. Early multidisciplinary discussions between plastic surgeons and neurosurgeons may avoid multiple CBF elevations and prevent the adverse sequela of high-risk calvarial reconstruction efforts.

Two-center validation of the Oulu resorption score for bone flap resorption after autologous cranioplasty

OBJECTIVE

Autologous bone has been the gold standard of cranioplasty materials for decades. Unique to autologous cranioplasty, bone flap resorption is a poorly understood and unclearly defined complication. Even further, it has been unclear, whether the resorption process eventually stabilizes over time. Thus, the sufficient follow-up period after autologous cranioplasty is unknown. The Oulu Resorption Score (ORS) is a straight-forward classification system for the radiological interpretation of bone flap resorption. The aims of the present study were to evaluate the reliability of the ORS using intra-class correlation coefficient (ICC) and to assess the temporal progression of the resorption process.

METHODS

We identified 108 consecutive autologous cranioplasty patients treated between 2005 and 2018 in two tertiary referral centers. All 365 head CT scans the patients had undergone were evaluated using the ORS in a blinded, independent two-center setting. Intra- and inter-observer reliabilities were calculated. The ORS was applied to study the temporal progression of the resorption process.

RESULTS

The intra-observer reliability of the ORS was excellent (ICC 0.94, 95%CI 0.93-0.95). Inter-observer reliability was good-to-excellent (ICCs 0.87 and 0.89, 95%CIs 0.84-0.89 and 0.87-0.91, respectively). In scatterplot smoothing analyses, the progression of bone flap resorption appeared to stabilize 12-24 months after cranioplasty.

CONCLUSIONS

ORS is the only validated radiological tool for the standardized analysis of bone flap resorption after autologous cranioplasty. Evaluated using the ORS, the resorption process seemed to stabilize during the first two postoperative years after cranioplasty, suggesting that the sufficient follow-up time after autologous cranioplasty is two years.

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

BACKGROUND

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 network meta-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 abstracts were screened and 31 full papers were 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.

Spontaneous Bone Flap Resorption Following Cranioplasty Using Autologous Bone

ABSTRACT

Cranioplasty is a common neurosurgical procedure. The main reasons for performing cranioplasty are, in addition to aesthetic correction and protection of the brain, the reestablishment of the adequate flow of cerebrospinal fluid and the prevention of complications inherent to the perpetuation of bone failure. In our institution the patient's autologous bone remains the best method for performing cranioplasty, despite the existence of other heterologous grafts and bone substitutes. Despite representing for us, the best material for cranioplasty, the use of autologous grafting is subject to complications. In this paper, the authors present the case of a patient who underwent cranioplasty with autologous bone that progressed with spontaneous resorption of the bone flap. The authors herein briefly discuss the case and review the literature on the subject, with an emphasis on the factors that can lead to such an outcome.

Aseptic bone-flap resorption after cranioplasty - incidence and risk factors

Objective

One of the common complications occurring after cranioplasty (CP) is aseptic bone-flap resorption (ABFR). Reoperation necessary because of the development of ABFR can lead to unfavorable complications during subsequent surgery using a synthetic skull implant, and also necessarily leads to higher costs. The aim of this study is to identify prognostic factors that may help to predict the development of ABFR.

Methods

In this study, 303 CP surgeries performed between 2002 and 2017 were examined retrospectively to identify factors predicting the occurrence of ABFR. A number of these factors (e.g., time lapse between decompressive craniectomy (DC) and CP, bone-flap size, specific laboratory signs, and the reason for the original DC) were analyzed as possibly influencing the risk of developing ABFR.

Results

ABFR of an autologous bone flap that subsequently required a CP with synthetic skull implants occurred in 10 of 303 patients (3.0%). CP timing and patients' Karnofsky Performance Scores (KPS) (p = 0.008; p = 0.012) were identified as significant factors with an impact on the development of ABRF. Age did not reveal a significant value, but statistical analysis shows a clear trend. The younger the age, the more likely it was that an ABFR would develop.

Conclusion

The risk of ABFR lessens the longer the period of time elapsed between DC and CP. Age does not reveal a significant value, but statistical analysis shows that there is a clear trend.

ACE-inhibitors: a preventive measure for bone flap resorption after autologous cranioplasty?

OBJECTIVE

Decompressive craniectomy (DC) is an established treatment for refractory intracranial hypertension. It is usually followed by autologous cranioplasty (AC), the reinsertion of a patient's explanted bone flap. A frequent long-term complication of AC is bone flap resorption (BFR), which results in disfigurement as well as loss of the protective covering of the brain. This study investigates risk factors for BFR after AC, including medical conditions and antihypertensive drug therapies, with a focus on angiotensin-converting enzyme inhibitors (ACEIs), which have been associated with a beneficial effect on bone healing and bone preservation in orthopedic, osteoporosis, and endocrinology research.

METHODS

In this single-center, retrospective study 183 consecutive cases were evaluated for bone flap resorption after AC. Information on patient demographics, medical conditions, antihypertensive therapy, and BFR-defined as an indication for revision surgery established by a neurosurgeon based on clinical or radiographic assessments-was collected. A Kaplan-Meier analysis of time from AC to diagnosis of BFR was performed, and factors associated with BFR were investigated using the log-rank test and Cox regression.

RESULTS

A total of 158 patients were considered eligible for inclusion in the data analysis. The median follow-up time for this group was 2.2 years (95% CI 1.9-2.5 years). BFR occurred in 47 patients (29.7%), with a median time to event of 3.7 years (95% CI 3.3-4.1 years). An ACEI prescription was recorded in 57 cases (36.1%). Univariate Kaplan-Meier analysis and the log-rank test revealed that ACEI therapy (2-year event free probability [EFP] 83.8% ± 6.1% standard error vs 63.9% ± 5.6%, p = 0.02) and ventriculoperitoneal (VP) shunt treatment (2-year EFP 86.9% ± 7.1% vs 66% ± 5.0%, p = 0.024) were associated with a lower probability of BFR. Multiple Cox regression analysis showed ACEI therapy (HR 0.29, p = 0.012), VP shunt treatment (HR 0.278, p = 0.009), and male sex (HR 0.500, p = 0.040) to be associated with a lower risk for BFR, whereas bone fragmentation (HR 1.92, p = 0.031) was associated with a higher risk for BFR.

CONCLUSIONS

Hypertensive patients treated with ACEIs demonstrate a lower rate of BFR than patients treated with other hypertensive medications and nonhypertensive patients. Our results are in line with previous reports on the positive influence of ACEIs on bone healing and preservation. Further analysis of the association between ACEI treatment and BFR development is needed and will be evaluated in a multicenter prospective trial.

Predictors of primary autograft cranioplasty survival and resorption after craniectomy

OBJECTIVE

Craniectomy is a common neurosurgical procedure that reduces intracranial pressure, but survival necessitates cranioplasty at a later stage, after recovery from the primary insult. Complications such as infection and resorption of the autologous bone flap are common. The risk factors for complications and subsequent bone flap removal are unclear. The aim of this multicenter, retrospective study was to evaluate the factors affecting the outcome of primary autologous cranioplasty, with special emphasis on bone flap resorption.

METHODS

The authors identified all patients who underwent primary autologous cranioplasty at 3 tertiary-level university hospitals between 2002 and 2015. Patients underwent follow-up until bone flap removal, death, or December 31, 2015.

RESULTS

The cohort comprised 207 patients with a mean follow-up period of 3.7 years (SD 2.7 years). The overall complication rate was 39.6% (82/207), the bone flap removal rate was 19.3% (40/207), and 11 patients (5.3%) died during the follow-up period. Smoking (OR 3.23, 95% CI 1.50-6.95; p = 0.003) and age younger than 45 years (OR 2.29, 95% CI 1.07-4.89; p = 0.032) were found to independently predict subsequent autograft removal, while age younger than 30 years was found to independently predict clinically relevant bone flap resorption (OR 4.59, 95% CI 1.15-18.34; p = 0.03). The interval between craniectomy and cranioplasty was not found to predict either bone flap removal or resorption.

CONCLUSIONS

In this large, multicenter cohort of patients with autologous cranioplasty, smoking and younger age predicted complications leading to bone flap removal. Very young age predicted bone flap resorption. The authors recommend that physicians extensively inform their patients of the pronounced risks of smoking before cranioplasty.

Classification of bone flap resorption after cranioplasty: a proposal for a computed tomography-based scoring system

Background

Bone flap resorption (BFR) is the most prevalent complication resulting in autologous cranioplasty failure, but no consensus on the definition of BFR or between the radiological signs and relevance of BFR has been established. We set out to develop an easy-to-use scoring system intended to standardize the interpretation of radiological BFR findings.

Methods

All 45 autologous cranioplasty patients operated on at Oulu University Hospital from 2004 to 2014 were identified, and the bone flap status of all the available patients was evaluated using the new scoring system. Derived from previous literature, a three-variable score for the detection of BFR changes is proposed. The variables “Extent” (estimated remaining bone volume), “Severity” (possible perforations and their measured diameter), and “Focus” (the number of BFR foci within the flap) are scored from 0 to 3 individually. Using the sum of these scores, a score of 0–9 is assigned to describe the degree of BFR. Additionally, independent neurosurgeons assessed the presence and relevance of BFR from the same data set. These assessments were compared to the BFR scores in order to find a score limit for relevant BFR.

Results

BFR was considered relevant by the neurosurgeons in 11 (26.8%) cases. The agreement on the relevance of BFR demonstrated substantial strength (κ 0.64, 95%CI 0.36 to 0.91). The minimum resorption score in cases of relevant BFR was 5. Thus, BFR with a resorption score ≥ 5 was defined relevant (grades II and III). With this definition, grade II or III BFR was found in 15 (36.6%) of our patients. No risk factors were found to predict relevant BFR.

Conclusions

The score was proven to be easy to use and we recommend that only cases with grades II and III BFR undergo neurosurgical consultation. However, general applicability can only be claimed after validation in independent cohorts.

Bone resorption in autologous cryopreserved cranioplasty: quantitative evaluation, semiquantitative score and clinical significance

BACKGROUND

Changes after reimplantation of the autologous bone have been largely described. However, the rate and the extent of resorption in cranial grafts have not been clearly defined. Aim of our study is to evaluate the bone flap resorption (BFR) after cryopreservation.

METHODS

We retrospectively reviewed 27 patients, aged 18 years or older, subjected to cranioplasty (CP) adopting autologous cryopreserved flap. The BFR was derived from the percentage of decrease in flap volume (BFR%), comparing the first post-operative computed tomography (CT) and the last one available (performed at least 1 year after surgery). We also proposed a semiquantitative scoring system, based on CT, to define a clinically workable BFR classification.

RESULTS

After a mean ± SE follow-up of 32.5 ± 2.4 months, the bone flap volume decreased significantly (p < 0.0001). The mean BFR% was 31.7 ± 3.8% and correlated with CT-score (p < 0.001). Three BFR classes were described: mild (14.8% of cases) consisting in minimal bone remodelling, CT-score ≤ 6, mean BFR% = 3.5 ± 0.7%; moderate (51.9% of cases) corresponding to satisfactory cerebral protection, CT-score < 13, mean BFR% = 25.6 ± 2.2%; severe (33.3% of cases) consisting in loss of cerebral protection, CT-score ≥ 13, mean BFR% = 54.2 ± 3.9%. Females had higher BFR% than males (p = 0.022). BFR classes and new reconstructive surgery were not related (p = 0.58).

CONCLUSIONS

BFR was moderate or severe in 85.2% of re-implanted cryopreserved flaps. The proposed CT-score is an easy and reproducible tool to define resorption extent.

Quantitative and qualitative analysis of bone flap resorption in patients undergoing cranioplasty after decompressive craniectomy

OBJECTIVE: Autologous bone cranioplasty after decompressive craniectomy entails a notable burden of difficult postoperative complications, such as infection and bone flap resorption (BFR), leading to mechanical failure. The prevalence and significance of asymptomatic BFR is currently unclear. The aim of this study was to radiologically monitor the long-term bone flap survival and bone quality change in patients undergoing autologous cranioplasty. METHODS: The authors identified all 45 patients who underwent autologous cranioplasty at Oulu University Hospital, Finland, between January 2004 and December 2014. Using perioperative and follow-up CT scans, the volumes and radiodensities of the intact bone flap prior to surgery and at follow-up were calculated. Relative changes in bone flap volume and radiodensity were then determined to assess cranioplasty survival. Sufficient CT scans were obtainable from 41 (91.1%) of the 45 patients. RESULTS: The 41 patients were followed up for a median duration of 3.79 years (25th and 75th percentiles = 1.55 and 6.66). Thirty-seven (90.2%) of the 41 patients had some degree of BFR and 13 (31.7%) had a remaining bone flap volume of less than 80%. Patients younger than 30 years of age had a mean decrease of 15.8% in bone flap volume compared with the rest of the cohort. Bone flap volume was not found to decrease linearly with the passing of time, however. The effects of lifestyle factors and comorbidities on BFR were nonsignificant. CONCLUSIONS: In this study BFR was a very common phenomenon, occurring at least to some degree in 90% of the patients. Decreases in bone volume were especially prominent in patients younger than 30 years of age. Because the progression of resorption during follow-up was nonlinear, routine follow-up CT scans appear unnecessary in monitoring the progression of BFR; instead, clinical follow-up with mechanical stability assessment is advised. Partial resorption is most likely a normal physiological phenomenon during the bone revitalization process.

Defining "early" cranioplasty to achieve lower complication rates of bone flap failure: resorption and infection

BACKGROUND

Although cranioplasty (CP) is a frequently performed and simple procedure, complications are common, particularly bone flap resorption and infection. The timing of surgery is as an important contributory factor, but the optimal timing has not been clearly determined.

OBJECTIVE

We retrospectively investigated bone flap resorption and surgical site infection after CP to determine the optimal timing of surgery for reduction of complications.

METHODS

The study enrolled 126 patients who underwent decompressive craniectomy (DC) and subsequent CP. Patients with bone flap resorption or surgical site infection were analyzed as the "complication" group. Receiver operating characteristic curve analysis was performed and the Youden index was used to dichotomize "early CP" and "late CP" groups. Univariate and multivariate survival analyses were performed.

RESULTS

The complication group included 42 patients. The Youden index was used to identify a cutoff value for the DC-CP interval of > 44 days, and this was used to define early (< 45 days) and late (≥ 45 days) CP. Late CP was a significant risk factor in univariate and multivariate Cox regression analyses.

CONCLUSION

This study showed that early CP before 45 days after DC is associated with a lower rate of bone flap resorption and surgical site infection than late CP.

Bone Flap Conservation in the Scalp After Decompressive Craniectomy

BACKGROUND

Decompressive craniectomy may be used as a primary or secondary treatment for intracranial hypertension and is clearly associated with reduced mortality. The removed bone flap is usually preserved in the abdominal subcutaneous tissue or in the bone bank. The aim of this study was to describe an option for preserving the bone flap after decompressive craniectomy using bone flap preservation in the skull subcutaneous tissue in subgaleal space over the pericranium contralateral to the craniectomy site.

METHODS

This was a multicenter retrospective study including patients with severe traumatic brain injury from 2014 to 2016. There were 23 patients who had their bone fragments preserved below the scalp in the subcutaneous tissue for analysis. The following results were analyzed: surgical site infection, bone flap resorption during the period of preservation, and patient discomfort.

RESULTS

Five patients died of systemic infectious complications, and the remaining patients underwent cranioplasty a mean 118 days after craniectomy. There were no surgical wound infections, macroscopically evident bone absorption, or site discomfort in any of the patients during a period of 18 months.

CONCLUSIONS

This variant of the bone flap preservation technique has been shown to be satisfactory as an option for routine use.

Additively manufactured versus conventionally pressed cranioplasty implants: An accuracy comparison

This article compared the accuracy of producing patient-specific cranioplasty implants using four different approaches. Benchmark geometry was designed to represent a cranium and a defect added simulating a craniectomy. An ‘ideal’ contour reconstruction was calculated and compared against reconstructions resulting from the four approaches –‘conventional’, ‘semi-digital’, ‘digital – non-automated’ and ‘digital – semi-automated’. The ‘conventional’ approach relied on hand carving a reconstruction, turning this into a press tool, and pressing titanium sheet. This approach is common in the UK National Health Service. The ‘semi-digital’ approach removed the hand-carving element. Both of the ‘digital’ approaches utilised additive manufacturing to produce the end-use implant. The geometries were designed using a non-specialised computer-aided design software and a semi-automated cranioplasty implant-specific computer-aided design software. It was found that all plates were clinically acceptable and that the digitally designed and additive manufacturing plates were as accurate as the conventional implants. There were no significant differences between the additive manufacturing plates designed using non-specialised computer-aided design software and those designed using the semi-automated tool. The semi-automated software and additive manufacturing production process were capable of producing cranioplasty implants of similar accuracy to multi-purpose software and additive manufacturing, and both were more accurate than handmade implants. The difference was not of clinical significance, demonstrating that the accuracy of additive manufacturing cranioplasty implants meets current best practice.

A randomised controlled trial comparing autologous cranioplasty with custom-made titanium cranioplasty: long-term follow-up

OBJECTIVE

To compare the long-term outcomes of patients who had been randomly allocated to receive primary titanium cranioplasty or autologous bone graft following decompressive craniectomy.

METHODS

Sixty-four patients had been previously enrolled and randomised to receive either their own bone graft or a primary titanium cranioplasty. Functional and cosmetic outcomes had previously been assessed at 1-year following the cranioplasty procedure. Hospital records and the Picture Archiving communication system were reviewed to determine how many patients had cranioplasty failure or associated complications such as seizures beyond 1 year-with a minimum of 24-month follow-up.

RESULTS

Amongst the 31 patients in the titanium group (one patient had died), no patients had a partial or complete cranioplasty failure at 12 months follow-up and there had been no failures beyond 12 months. Amongst the 31 patients who had an autologous cranioplasty (one patient had died), 7 patients had complete resorption of the autologous bone such that it was adjudged a complete failure at 12-month follow-up. Five of these patients had had titanium augmentation and two patients declined further surgery. Both of these patients requested cranial augmentation for functional and cosmetic reasons subsequent to the 12-month follow-up. Another patient who had previously been noted to have moderate resorption at 12 months presented 1 year later with progressive bone flap resorption and also required subsequent augmentation for functional and cosmetic reasons. When follow-up was extended to a minimum of 24 months, use of titanium instead of autologous bone for primary cranioplasty resulted in a significant reduction in the number of patients who required rescue cranioplasty (0 vs 25%, 95% confidence interval [CI] 9.1-42.1%; p = 0.001). In addition, there were significantly less total hospital healthcare costs in those patients randomised to the titanium arm of the trial (difference = A$9999, 95%CI 2231-17,768; p = 0.015).

CONCLUSIONS

Bone resorption continued to occur beyond 12 months after autologous cranioplasty; use of primary titanium cranioplasty after decompressive craniectomy reduced the number of reoperations needed and the associated long-term total hospital costs.

Aseptic Bone Flap Resorption after Cranioplasty with Autologous Bone: Incidence, Risk Factors, and Clinical Implications

OBJECTIVES

Aseptic bone flap resorption (ABFR) is a known complication of cranioplasty (CP) with an autologous bone flap. The incidence of ABFR has been reported to be as high as 34.2% in the literature; however, it is underestimated in clinical fields. We retrospectively reviewed 13 years of clinical cases of patients who underwent CP after decompressive craniectomy (DC) to investigate the incidence and risk factors of ABFR.

METHODS

Ninety-one patients who underwent DC and CP in Guro Hospital, Korea University Medical Center, were enrolled. ABFR was defined using serial brain computed tomography. To identify possible risk factors for ABFR, univariate and multivariate Cox regression and receiver operating characteristic curve analyses were performed.

RESULTS

Of the 91 patients enrolled, ABFR was diagnosed in 32 patients (35.1%). Bone flap size, existence of a shunting system, and the DC-CP interval were significant in the univariate analysis. Bone flap size was statistically significant in the multivariate analysis (P = 0.0189). The cutoff points of the DC-CP interval and bone flap size were 44 days and 110 cm², respectively.

CONCLUSIONS

The incidence of ABFR was remarkably high. Bone flap size, the existence of a shunting system, and the DC-CP interval were shown to be potential risk factors of ABFR after CP.

Bone Flap Resorption Following Cranioplasty with Autologous Bone: Quantitative Measurement of Bone Flap Resorption and Predictive Factors

Objective

To quantitatively measure the degree of bone flap resorption (BFR) following autologous bone cranioplasty and to investigate factors associated with BFR.

Methods

We retrospectively reviewed 29 patients who underwent decompressive craniectomy and subsequent autologous bone cranioplasty between April 2005 and October 2014. BFR was defined as: 1) decrement ratio ([the ratio of initial BF size/craniectomy size]-[the ratio of last BF/craniectomy size]) >0.1; and 2) bone flap thinning or geometrical irregularity of bone flap shape on computed tomographic scan or skull plain X-ray. The minimal interval between craniectomy and cranioplasty was one month and the minimal follow-up period was one year. Clinical factors were compared between the BFR and no-BFR groups.

Results

The time interval between craniectomy and cranioplasty was 175.7±258.2 days and the mean period of follow up was 1364±886.8 days. Among the 29 patients (mean age 48.1 years, male: female ratio 20: 9), BFR occurred in 8 patients (27.6%). In one patient, removal of the bone flap was carried out due to severe BFR. The overall rate of BFR was 0.10±0.11 over 3.7 years. Following univariate analysis, younger age (30.5±23.2 vs. 54.9±13.4) and longer follow-up period (2204.5±897.3 vs. 1044.1±655.1) were significantly associated with BFR (p=0.008 and 0.003, respectively).

Conclusion

The degree of BFR following autologous bone cranioplasty was 2.7%/year and was associated with younger age and longer follow-up period.

Complications of skull reconstruction after decompressive craniectomy

INTRODUCTION

Decompressive craniectomy can be a life-saving procedure. Later reconstruction of the skull using the stored bone flap ("cranioplasty") is often associated with complications. These complications require new procedures and often result in the reconstruction of the skull using an expensive patient-specific cranial implant.

PATIENTS & METHODS

All adult patients who underwent cranioplasty after decompressive craniectomy in the last 10 years in our center were included (74 patients). Bone flap size, duration of the procedure, age, and other clinical parameters were included in our analysis.

RESULTS

29.7% of our patients who received in the first place an autologous cranioplasty developed a complication which necessitated removal of the bone flap and the implantation of a custom-made implant. Descriptive statistics demonstrate a significantly higher amount of complications in younger patients (20-40 years, p = 0.027). We also saw a trend toward lower complications when bone flaps were stored according to a biobank protocol (p = 0.075).

CONCLUSIONS

Cranioplasty using the stored bone flap after decompressive craniectomy is associated with a high percentage of complications. Selecting patients at risk could possibly indicate cases where an immediate custom-made implant technique would be required.

Evolution of design considerations in complex craniofacial reconstruction using patient-specific implants

Previously published evidence has established major clinical benefits from using computer-aided design, computer-aided manufacturing, and additive manufacturing to produce patient-specific devices. These include cutting guides, drilling guides, positioning guides, and implants. However, custom devices produced using these methods are still not in routine use, particularly by the UK National Health Service. Oft-cited reasons for this slow uptake include the following: a higher up-front cost than conventionally fabricated devices, material-choice uncertainty, and a lack of long-term follow-up due to their relatively recent introduction. This article identifies a further gap in current knowledge – that of design rules, or key specification considerations for complex computer-aided design/computer-aided manufacturing/additive manufacturing devices. This research begins to address the gap by combining a detailed review of the literature with first-hand experience of interdisciplinary collaboration on five craniofacial patient case studies. In each patient case, bony lesions in the orbito-temporal region were segmented, excised, and reconstructed in the virtual environment. Three cases translated these digital plans into theatre via polymer surgical guides. Four cases utilised additive manufacturing to fabricate titanium implants. One implant was machined from polyether ether ketone. From the literature, articles with relevant abstracts were analysed to extract design considerations. In all, 19 frequently recurring design considerations were extracted from previous publications. Nine new design considerations were extracted from the case studies – on the basis of subjective clinical evaluation. These were synthesised to produce a design considerations framework to assist clinicians with prescribing and design engineers with modelling. Promising avenues for further research are proposed.

Patient-specific polymethylmethacrylate prostheses for secondary reconstruction of large calvarial defects: A retrospective feasibility study of a new intraoperative moulding device for cranioplasty

PURPOSE

The aim of this study was to review a new template-based technique for intraoperative patient-specific cranioplasty manufacturing (PSCM) with polymethylmethacrylate (PMMA) to cover large calvarial defects.

MATERIAL AND METHODS

A polypropylene foil thermoformed on a three-dimensional reprint of the calvarial defect was used as an intraoperative moulding device for PMMA between August 2012 and December 2015. Surgical and radiological data were retrospectively reviewed, and a patient questionnaire was used to assess functional and cosmetic outcome (numeric rating scale, Odom's criteria).

RESULTS

Seventeen patients (mean age 42.2 ± 14.5 years) received PSCM. Operating time averaged 130 ± 34 min, and the approximate blood loss was 293 ± 185 ml. Volumetric analysis revealed a lower implant volume compared to index bone (mean 66.5 vs. 72 cm³, p = 0.513), the mean difference in thickness being the lowest in the posterior parietal and pterional (0.4-0.7 mm) and the highest in the anterior-superior frontal area (1.8 mm). Cosmetic satisfaction averaged 9 ± 1.5, with 70.6% of patients judging the overall result as excellent or good and 29.4% as satisfactory. Mean follow-up was 19.5 ± 13.3 months, with an overall complication rate of 17.6%, including 11.8% surgical site infections (SSIs) and one implant removal.

CONCLUSIONS

Intraoperative PSCM using PMMA moulded on a thermoformed polypropylene foil leads to satisfactory outcomes. It is a safe technique with complication rates comparable but not superior to those of other alloplastic techniques, but the device has considerable production costs.

Bone healing in rabbit calvarial critical-sized defects filled with stem cells and growth factors combined with granular or solid scaffolds

PURPOSE

In pediatric neurosurgery, decompressive craniectomy and correction of congenital cranial anomalies can result in major cranial defects. Corrective cranioplasty for the repair of these critical-sized defects is not only a cosmetic issue. The limited availability of suitable autogenous bone and the morbidity of donor site harvesting have driven the search for new approaches with biodegradable and bioactive materials. This study aimed to assess the healing of rabbit calvarial critical-sized defects filled with osteogenic material, either with bioactive glass scaffolds or tricalcium phosphate granules in various combinations with adipose stem cells or bone marrow stem cells, BMP-2, BMP-7, or VEGF to enhance osteogenesis.

METHODS

Eighty-two bicortical full thickness critical-sized calvarial defects were operated. Five defects were left empty as negative control defects. The remaining 77 defects were filled with solid bioactive glass scaffolds or tricalcium phosphate granules seeded with adipose or bone marrow derived stem cells in combination with BMP-2, BMP-7, or VEGF. The defects were allowed to heal for 6 weeks before histologic and micro-CT analyses.

RESULTS

Micro-CT examination at the 6-week post-operative time point revealed that defects filled with stem cell-seeded tricalcium phosphate granules resulted in new bone formation of 6.0 %, whereas defects with bioactive glass scaffolds with stem cells showed new bone formation of 0.5 to 1.7 %, depending on the growth factor used.

CONCLUSIONS

This study suggests that tricalcium phosphate granules combined with stem cells have osteogenic potential superior to solid bioactive glass scaffolds with stem cells and growth factors.

A randomized controlled trial comparing autologous cranioplasty with custom-made titanium cranioplasty

OBJECTIVE Autologous bone is usually used to reconstruct skull defects following decompressive surgery. However, it is associated with a high failure rate due to infection and resorption. The aim of this study was to see whether it would be cost-effective to use titanium as a primary reconstructive material. METHODS Sixty-four patients were enrolled and randomized to receive either their own bone or a primary titanium cranioplasty. All surgical procedures were performed by the senior surgeon. Primary and secondary outcome measures were assessed at 1 year after cranioplasty. RESULTS There were no primary infections in either arm of the trial. There was one secondary infection of a titanium cranioplasty that had replaced a resorbed autologous cranioplasty. In the titanium group, no patient was considered to have partial or complete cranioplasty failure at 12 months of follow-up (p = 0.002) and none needed revision (p = 0.053). There were 2 deaths unrelated to the cranioplasty, one in each arm of the trial. Among the 31 patients who had an autologous cranioplasty, 7 patients (22%) had complete resorption of the autologous bone such that it was deemed a complete failure. Partial or complete autologous bone resorption appeared to be more common among young patients than older patients (32 vs 45 years old, p = 0.013). The total cumulative cost between the 2 groups was not significantly different (mean difference A$3281, 95% CI $-9869 to $3308; p = 0.327). CONCLUSIONS Primary titanium cranioplasty should be seriously considered for young patients who require reconstruction of the skull vault following decompressive craniectomy. Clinical trial registration no.: ACTRN12612000353897 ( anzctr.org.au ).

Bone flap resorption following cranioplasty in a cost-constrained scenario

Bone flap resorption is an infrequently reported yet significant late complication of autologous bone cranioplasty. It requires serial imaging both to pick up and to monitor progression. Custom-made implants avoid this complication, but are expensive. In a resource-limited situation, when bone flaps placed in the abdomen undergo demineralisation and sutures are used to fix the flap as opposed to plates, where artificial cranial flap substitutes are prohibitively expensive and frequent postoperative imaging may not be feasible, prevention and management of this complication will continue to remain a problem.