Clinical evaluation of the polypropylene-polyester knit used as a cranioplasty material

Characterisation of Selected Materials in Medical Applications

Tissue engineering is an interdisciplinary field of science that has developed very intensively in recent years. The first part of this review describes materials with medical and dental applications from the following groups: metals, polymers, ceramics, and composites. Both positive and negative sides of their application are presented from the point of view of medical application and mechanical properties. A variety of techniques for the manufacture of biomedical components are presented in this review. The main focus of this work is on additive manufacturing and 3D printing, as these modern techniques have been evaluated to be the best methods for the manufacture of medical and dental devices. The second part presents devices for skull bone reconstruction. The materials from which they are made and the possibilities offered by 3D printing in this field are also described. The last part concerns dental transitional implants (scaffolds) for guided bone regeneration, focusing on polylactide–hydroxyapatite nanocomposite due to its unique properties. This section summarises the current knowledge of scaffolds, focusing on the material, mechanical and biological requirements, the effects of these devices on the human body, and their great potential for applications.

Contemporary Review on Craniectomy and Cranioplasty; Part 2: Material Selection and Plate Manufacture

ABSTRACT

Cranioplasty materials include metals (ie, titanium); ceramics (ie, hydroxyapatite); polymers (ie, poly-methyl-metha-acrylate [PMMA]); and plastics (ie, polyether ether ketone). This paper aims to review their advantages and drawbacks. No ideal material currently exist, however, titanium implants are universally agreed to have lower infection rates than those reported for hydroxyapatite and PMMA implants; thus justifying their current wide use. These implants can be manufactured conventionally from medical grade titanium alloy Ti64 (titanium-aluminum-vanadium) in the form of plates ranging in thickness from 0.5 to 0.7 mm thick, or following the computer-aided design/manufacture principle. Surface finish of these implants is best achieved by electroplating.

A systematic review of cranioplasty material toxicity in human subjects

PURPOSE

Local and systemic toxic reactions to implanted materials can result in morbidities. However, little is reported about cranioplasty implants. Therefore, we performed a systematic review on the toxicity of different materials used for cranioplasty implants.

MATERIALS AND METHODS

A systematic search was conducted by browsing the Pubmed, Embase, and Cochrane Library databases. All human studies that identified toxic (aseptic) reactions to any types of material used as cranioplasty implants or onplants, published up to January 1, 2019, were included in the review.

RESULTS

Nineteen studies were identified. Collectively, 36 patients endured some type of toxic reaction to an implanted material. Eleven studies presented several types of toxicity for PMMA cranioplasties in several tissue types. One article highlighted the risk of neurotoxicity for PMMA cranioplasty. Three articles presented toxic reactions to calcium phosphate and titanium implants. Three additional articles presented toxic reactions to PEEK, polypropylene-polyester, and polyethylene.

CONCLUSION

All materials currently used for cranioplasty showed occasional toxicity and morbidities. Therefore, none can be considered completely biologically inert. We found that aseptic inflammatory reactions have been underreported in the literature due to a high incidence of infections with questionable evidence.

An investigation of factors associated with the development of postoperative bone flap infection following decompressive craniectomy and subsequent cranioplasty

OBJECTIVE

After a decompressive craniectomy (DC), a cranioplasty (CP) is often performed in order to improve neurosurgical outcome and cerebral blood circulation. But even though the performance of a CP subsequent to a DC has become routine medical practice, patients can in fact develop many complications from the surgery that could prolong hospitalization and lead to unfavorable prognoses. This study investigates one of the most frequent complications, bone flap infection, in order to identify prognostic factors of its development.

PATIENTS AND METHODS

In this single-center study, we have retrospectively examined 329 CPs performed between 2002 and 2017. Multiple categorical and metric parameters (e.g., timing of CP, bone flap material, specific laboratory signs of infection and reason for DC) were analyzed applying unadjusted and multivariable testing.

RESULTS

Bone flap infection occurred in 24 patients (7.3%). A CP performed more than six months after a DC is associated with a significantly increased risk of infection (OR = 0.308 [0.118; 0.803], p = 0.016). However, with CPs performed after twelve months, the incidence decreases, but without provable statistical impact. In addition, bone flap infection is strongly related to the neurological outcome and the material used for the skull implant, with the use of synthetic bone flaps leading to a marked increase in the rate of infection (p < 0.001).

CONCLUSIONS

This study supports the hypothesis that the risk of infection is higher the longer the elapsed time between DC and CP, especially if more than six months. Based on our results, the best DC-CP time frame for keeping the infection rate low is performing the CP within the first six months after the DC. In the event that the CP cannot be performed within the first six months, a CP performed twelve months or more after the DC seems to have a favorable outcome as well.

Incidence and Risk Factors for Skull Implant Displacement After Cranial Surgery

OBJECTIVE

Various complications that can occur during and after cranial surgery have been investigated extensively. One of the less frequent complications has thus far received little attention, however: displacement of the skull implant after craniotomy or craniectomy. The purpose of this study is to identify prognostic factors for the development of skull implant displacement (SID).

METHODS

In this study, 9087 cranial surgeries performed between 2002 and 2017 were retrospectively examined for the occurrence of SID. Because a first analysis of the investigated data revealed that a notable number of SIDs occurred after a cranioplasty (CP) performed after a decompressive craniectomy (DC), we focused our investigation on these cases. A total of 669 DCs and 329 subsequently performed CPs were analyzed. Several factors were analyzed unadjusted as possible factors influencing the risk for the development of SID.

RESULTS

A total of 13 implant dislocations occurred after CP (3.95%). Fixation technique is the only factor that seems to have had a significant influence, specifically not using miniplates as the fixation technique, which was associated with a higher risk of SID (P = 0.043). However, if fixation techniques are distinguished in more detail, no significant advantage of the miniplates over titanium clamps can be proven (P = 0.123). None of the remaining observed factors showed a statistically provable impact in our data.

CONCLUSIONS

A notable number of SIDs only occur after CPs that follow a DC. An advantage in successful placement was observed when fixation of the skull implant during cranioplasty was performed using miniplates.

Factors Affecting Optimal Time of Cranioplasty: Brain Sunken Ratio

Objective

After a rigorous management of increased intracranial pressure by decompressive craniectomy (DC), cranioplasty (CP) is usually carried out for functional and cosmetic purposes. However, the optimal timing of CP remains controversial. Our study aims to analyze the relationship between the optimal timing of CP and the post-operative complications.

Methods

From January 2013 to December 2015, ninety patients who underwent CP in a single institution were analyzed. We set the independent variables as follows: 1) patient characteristics; 2) the time interval between the DC and CP; 3) operation time; 4) anesthesia time; and 5) pre-operative computed tomography (CT) findings such as a degree of sunken brain by ratio of A (the median length from scalp to midline) to B (the length from midline to inner table of skull at this level). The dependent variables of this study are the event of post-operative complications.

Results

The overall complication rate was 33.3%. There was no statistical significance in the time interval between the DC and CP in the groups with and without complications of CP (p=0.632). However, there was a significant statistical difference in the degree of sunken brain by ratio (A/B) between the two groups (p<0.001).

Conclusion

From this study, we conclude that it is better to determine the optimal timing of CP by the pre-operative CT finding than by the time interval between the DC and CP. Hereby, we suggest a potentially useful determinant of optimal timing of CP.

Autogenous Bone Reconstruction of Large Secondary Skull Defects

BACKGROUND

The authors sought to ascertain the upper limits of secondary skull defect size amenable to autogenous reconstructions and to examine outcomes of a surgical series. Published data for autogenous and alloplastic skull reconstructions were also examined to explore associations that might guide treatment.

METHODS

A retrospective review of autogenously reconstructed secondary skull defects was undertaken. A structured literature review was also performed to assess potential differences in reported outcomes between autogenous bone and synthetic alloplastic skull reconstructions. Weighted risks were calculated for statistical testing.

RESULTS

Ninety-six patients underwent autogenous skull reconstruction for an average defect size of 93 cm (range, 4 to 506 cm) at a mean age of 12.9 years. The mean operative time was 3.4 hours, 2 percent required allogeneic blood transfusions, and the average length of stay was less than 3 days. The mean length of follow-up was 28 months. There were no postoperative infections requiring surgery, but one patient underwent secondary grafting for partial bone resorption. An analysis of 34 studies revealed that complications, infections, and reoperations were more commonly reported with alloplastic than with autogenous reconstructions (relative risk, 1.57, 4.8, and 1.48, respectively).

CONCLUSIONS

Autogenous reconstructions are feasible, with minimal associated morbidity, for patients with skull defect sizes as large as 500 cm. A structured literature review suggests that autogenous bone reconstructions are associated with lower reported infection, complication, and reoperation rates compared with synthetic alloplasts. Based on these findings, surgeons might consider using autogenous reconstructions even for larger skull defects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Cranioplasty with autogenous bone flaps cryopreserved in povidone iodine: a long-term follow-up study

OBJECTIVE The aim of this study was to investigate the long-term therapeutic efficacy of cranioplasty with autogenous bone flaps cryopreserved in povidone iodine and explore the risk factors for bone resorption. METHODS Clinical data and follow-up results of 188 patients (with 211 bone flaps) who underwent cranioplasty with autogenous bone flaps cryopreserved in povidone-iodine were retrospectively analyzed. Bone flap resorption was classified into 3 types according to CT features, including bone flap thinning (Type I), reduced bone density (Type II), and osteolysis within the flaps (Type III). The extent of bone flap resorption was graded as mild, moderate, or severe. RESULTS Short-term postoperative complications included subcutaneous or extradural seroma collection in 19 flaps (9.0%), epidural hematoma in 16 flaps (7.6%), and infection in 8 flaps (3.8%). Eight patients whose flaps became infected and had to be removed and 2 patients who died within 2 years were excluded from the follow-up analysis. For the remaining 178 patients and 201 flaps, the follow-up duration was 24-122 months (mean 63.1 months). In 93 (46.3%) of these 201 flaps, CT demonstrated bone resorption, which was classified as Type I in 55 flaps (59.1%), Type II in 11 (11.8%), and Type III in 27 (29.0%). The severity of bone resorption was graded as follows: no bone resorption in 108 (53.7%) of 201 flaps, mild resorption in 66 (32.8%), moderate resorption in 15 (7.5%), and severe resorption in 12 (6.0%). The incidence of moderate or severe resorption was higher in Type III than in Type I (p = 0.0008). The grading of bone flap resorption was associated with the locations of bone flaps (p = 0.0210) and fragmentation (flaps broken into 2 or 3 fragments) (p = 0.0009). The incidence of bone flap collapse due to bone resorption was higher in patients who underwent ventriculoperitoneal (VP) shunt implantation than in those who did not (p = 0.0091). CONCLUSIONS Because of the low incidence rates of infection and severe bone resorption, the authors conclude that cranioplasty with autogenous bone flaps cryopreserved in povidone-iodine solution is safe and effective. The changes characteristic of bone flap resorption became visible on CT scans about 2 months after cranioplasty and tended to stabilize at about 18 months postoperatively. The bone resorption of autogenous bone flap may be classified into 3 types. The rates of moderate and severe resorption were much higher in Type III than in Type I. The grade of bone flap resorption was associated with bone flap locations. Fragmented bone flaps or those implanted in patients treated with VP shunts may have a higher incidence of bone flap collapse due to bone resorption.

Complications Associated with Decompressive Craniectomy: A Systematic Review

Decompressive craniectomy (DC) has been used for many years in the management of patients with elevated intracranial pressure and cerebral edema. Ongoing clinical trials are investigating the clinical and cost effectiveness of DC in trauma and stroke. While DC has demonstrable efficacy in saving life, it is accompanied by a myriad of non-trivial complications that have been inadequately highlighted in prospective clinical trials. Missing from our current understanding is a comprehensive analysis of all potential complications associated with DC. Here, we review the available literature, we tabulate all reported complications, and we calculate their frequency for specific indications. Of over 1500 records initially identified, a final total of 142 eligible records were included in our comprehensive analysis. We identified numerous complications related to DC that have not been systematically reviewed. Complications were of three major types: (1) Hemorrhagic (2) Infectious/Inflammatory, and (3) Disturbances of the CSF compartment. Complications associated with cranioplasty fell under similar major types, with additional complications relating to the bone flap. Overall, one of every ten patients undergoing DC may suffer a complication necessitating additional medical and/or neurosurgical intervention. While DC has received increased attention as a potential therapeutic option in a variety of situations, like any surgical procedure, DC is not without risk. Neurologists and neurosurgeons must be aware of all the potential complications of DC in order to properly advise their patients.

Early cranioplasty vs. late cranioplasty for the treatment of cranial defect: A systematic review

BACKGROUND

Cranioplasty is considered as a routine procedure in everyday neurosurgical practice for the patient with cranial defect, however, there is no established consensus on optimal surgical timing.

OBJECTIVE

To compare the effect of early cranioplasty (1-3 months after DC) and late cranioplasty (3-6 months after DC) on the complications and recovery of neurological function in the management of patients who received decompressive craniotomy.

METHODS

In this paper, the authors report a systematic review and meta-analysis of operative time, complications and neurological function outcomes on different timing of cranioplasty. Randomized or non-randomized controlled trials of early cranioplasty and late cranioplasty surgery were considered for inclusion.

RESULTS

Nine published reports of eligible studies involving 1209 participants meet the inclusion criteria. Compared with late cranioplasty, early cranioplasty had no significant difference in overall complications [RR=1.14, 95%CI (0.83, 1.55), p>0.05], infection rates [RR=0.87, 95%CI (0.47, 1.61), p>0.05], intracranial hematoma [RR=1.09, 95%CI (0.53, 2.25), p>0.05]; subdural fluid collection [RR=0.47, 95%CI (0.15, 1.41), p>0.05]. However, early CP significantly reduced the duration of cranioplasty [mean difference=-13.46, 95%CI (-21.26, 5.67), p<0.05]. The postoperative hydrocephalus rates were significant higher in the early cranioplasty group [RR=2.67, 95%CI (1.24, 5.73), p<0.05].

CONCLUSION

Early CP can only reduce the duration of operation, but cannot reduce the complications of patients and even increase the risk of hydrocephalus. More evidence from advanced multi-center studies is needed to provide illumination for the timing selection of CP surgery.

Two-stage desorption-controlled release of fluorescent dye and vitamin from solution-blown and electrospun nanofiber mats containing porogens

In the present work, a systematic study of the release kinetics of two embedded model drugs (one completely water soluble and one partially water soluble) from hydrophilic and hydrophobic nanofiber mats was conducted. Fluorescent dye Rhodamine B was used as a model hydrophilic drug in controlled release experiments after it was encapsulated in solution-blown soy-protein-containing hydrophilic nanofibers as well as in electrospun hydrophobic poly(ethylene terephthalate) (PET)-containing nanofibers. Vitamin B2 (riboflavin), a partially water-soluble model drug, was also encapsulated in hydrophobic PET-containing nanofiber mats, and its release kinetics was studied. The nanofiber mats were submerged in water, and the amount of drug released was tracked by fluorescence intensity. It was found that the release process saturates well below 100% release of the embedded compound. This is attributed to the fact that desorption is the limiting process in the release from biopolymer-containing nanofibers similar to the previously reported release from petroleum-derived polymer nanofibers. Release from monolithic as well as core-shell nanofibers was studied in the present work. Moreover, to facilitate the release and ultimately to approach 100% release, we also incorporated porogens, for example, poly(ethylene glycol), PEG. It was also found that the release rate can be controlled by the porogen choice in nanofibers. The effect of nanocracks created by leaching porogens on drug release was studied experimentally and evaluated theoretically, and the physical parameters characterizing the release process were established. The objective of the present work is a detailed experimental and theoretical investigation of controlled drug release from nanofibers facilitated by the presence of porogens. The novelty of this work is in forming nanofibers containing biodegradable and biocompatible soy proteins to facilitate controlled drug release as well as in measuring detailed quantitative characteristics of the desorption processes responsible for release of the model substance (fluorescent dye) and the vitamin (riboflavin) in the presence of porogens.

Cranioplasty prosthesis manufacturing based on reverse engineering technology

Background

Most patients with large focal skull bone loss after craniectomy are referred for cranioplasty. Reverse engineering is a technology which creates a computer-aided design (CAD) model of a real structure. Rapid prototyping is a technology which produces physical objects from virtual CAD models. The aim of this study was to assess the clinical usefulness of these technologies in cranioplasty prosthesis manufacturing.

Material/Methods

CT was performed on 19 patients with focal skull bone loss after craniectomy, using a dedicated protocol. A material model of skull deficit was produced using computer numerical control (CNC) milling, and individually pre-operatively adjusted polypropylene-polyester prosthesis was prepared. In a control group of 20 patients a prosthesis was manually adjusted to each patient by a neurosurgeon during surgery, without using CT-based reverse engineering/rapid prototyping. In each case, the prosthesis was implanted into the patient. The mean operating times in both groups were compared.

Results

In the group of patients with reverse engineering/rapid prototyping-based cranioplasty, the mean operating time was shorter (120.3 min) compared to that in the control group (136.5 min). The neurosurgeons found the new technology particularly useful in more complicated bone deficits with different curvatures in various planes.

Conclusions

Reverse engineering and rapid prototyping may reduce the time needed for cranioplasty neurosurgery and improve the prosthesis fitting. Such technologies may utilize data obtained by commonly used spiral CT scanners. The manufacturing of individually adjusted prostheses should be commonly used in patients planned for cranioplasty with synthetic material.

Reconstruction of cranial defects with individually formed cranial prostheses made of polypropylene polyester knitwear: an analysis of 48 consecutive patients

This article presents a new method of cranioplasty in which polypropylene polyester knitwear was used as the filling material. The basis for prosthesis shaping was a three-dimensional model of the defect made according to the patient's CT scans. Previously, such material has never been a subject of computer-aided design and computer-aided manufacturing (CAD/CAM) individual forming. The process of the prosthesis design included CT bone scans and mold preparation for each patient. Such prostheses were implanted in 48 patients with cranial defects. The total number of prostheses applied was 51. The follow-up time was at least 6 months up to 36 months. The group of treated patients is described here, and sample pictures are shown to illustrate the results. The smallest defect had a size of 15 cm(2); the biggest, 178 cm(2). The coverage and the aesthetic results were very good in all cases. Two patients had postoperative complications. The cranioplastic solution described here is a valuable addition to the existing reconstructive methods, because of the low cost of the implant, the ease of its adjustment to the shape of the defect, and the short time of preparation.

Effect of Early Surgery, Material, and Method of Flap Preservation on Cranioplasty Infections: A Systematic Review

BACKGROUND:

Infection is a significant cause of morbidity with cranioplasty procedures. However, few studies have investigated the effect of specific surgical practices on cranioplasty infection.

OBJECTIVE:

To analyze the literature on the effect of early surgery (within 3 months of craniectomy), implant material, and method of flap preservation on cranioplasty infections, and to perform a subanalysis of the effect of early surgery on overall complications associated with cranioplasty.

METHODS:

A systematic search of the PubMed, Cochrane, SCOPUS, and CINAHL databases was conducted. Comparative studies that reported on timing of surgery, implant material (autograft vs allograft), or method of flap preservation (subcutaneous vs extracorporeal), and infection or complication rates were selected for detailed analysis. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each analysis.

RESULTS:

Eighteen articles (2254 data points) met criteria for inclusion. There was no difference in infection rates (OR, 1.35; 95% CI, 0.53-3.41; P = .53) or overall complication rates (OR, 0.57; 95% CI, 0.29-1.11; P = .10) between early or later surgery. Fourteen studies (n = 1582) compared infection rates between autograft and allograft materials; there was no difference in infection rates between the two (OR, 0.81; 95% CI, 0.40-1.66; P = .57). There was no significant difference in infection rates between subcutaneous or extracorporeal preservation (OR, 0.35; 95% CI, 0.09-1.35; P = .13).

CONCLUSION:

Analysis of the best current evidence suggests that early surgery, implant material, and method of flap preservation have no effect on the rate of cranioplasty infections.

Management of postneurosurgical bone flap loss caused by infection

LEARNING OBJECTIVES

After studying this article, the participant should: 1. Be able to define indications and timing for secondary cranioplasty. 2. Understand the surgical options for reconstructing the cranium and overlying soft-tissue defect including their advantages and disadvantages. 3. Be able to apply this knowledge to the clinical setting of an infectious bone flap loss.

BACKGROUND

Infection after craniotomy occurs in approximately 1.1 to 8.1 percent of cases and often necessitates bone flap removal. For a secondary cranioplasty, there is an increased risk of recurrent infection, which influences the reconstructive plan. The soft tissue/scalp is frequently compromised by infection, sequelae of prior surgery, and/or adjuvant radiation therapy.

METHODS

A literature review was conducted to compile and summarize the indications for secondary cranioplasty after infectious bone flap loss, the timing of the procedure, and the surgical options for bone and soft-tissue reconstruction. In coordination with soft-tissue coverage, cranioplasty options include alloplastic reconstruction, allogeneic or autogenous bone grafts, and free tissue transfer.

RESULTS

The literature review identified the following factors that must be considered in the treatment plan for secondary cranioplasty after postneurosurgical bone flap loss: indications, timing of reconstruction, soft-tissue status and the need for soft-tissue reconstruction, and method of cranioplasty.

CONCLUSIONS

Treatment recommendations for cranioplasty in the clinical setting of infectious postneurosurgical bone flap loss are presented. These guidelines consider the risk factors for a recurrent infection, the condition of the soft-tissue coverage, and the concavity of the preoperative cranial deformity.