Custom-made Hydroxyapatite Research Articles

Predictors of postoperative epidural hematomas after custom-made porous hydroxyapatite cranioplasty: a single-center experience of 194 consecutive cases.

Cranioplasty is important for improving cosmesis and functional recovery after decompressive craniectomy. We assessed the incidence and predictors of post-cranioplasty epidural hematomas requiring surgical evacuation. A single-institution, retrospective study enrolled 194 consecutive patients who underwent a cranioplasty using custom-made hydroxyapatite between February 2008 and April 2022. Variables associated with postoperative epidural hematoma requiring surgical evacuation at the p < 0.1 level in unadjusted analysis were entered into multivariable analyses. Nine patients (4.6%) experienced postoperative epidural hematomas requiring evacuation, with time interval between craniectomy and cranioplasty <6 months (adjusted odds ratio (aOR), 20.75, p = 0.047), cranioplasty-to-bone shift > half of the bone thickness (aOR, 17.53, p = 0.008), >10 mm difference between pre-cranioplasty and post-cranioplasty midline brain shift contralateral to the cranioplasty (aOR, 17.26, p < 0.001), and non-resorbable duraplasty (aOR, 17.43, p = 0.011) identified as independent predictors. Seventeen patients (8.8%) experienced post-cranioplasty hydrocephalus requiring shunt placement. Twenty-six patients (13.4%) experienced postoperative infection. Sixteen patients (8.2%) had postoperative epileptic seizures. The identification of independent predictors of post-cranioplasty epidural hematomas requiring surgical evacuation will help identify at-risk patients, guide prophylactic care, and reduce morbidity of this common and important procedure.

The Antibiotic Immersion of Custom-Made Porous Hydroxyapatite Cranioplasty: A Multicentric Cohort Study.

Cranioplasty is a common neurosurgical procedure performed to reconstruct cranial defects. The most common cranioplasty materials used today can be divided into 2 types: autologous bone and bone substitutes, such as polyetheretherketone, titanium mesh, poly-methyl methacrylate, and Hydroxyapatite (HA). Infection represents one of the most feared complications, ranging from 2.3% to 20%. Early implant infections occur within 30 days from the operation and are mostly due to pathogens from the skin and the paranasal cavity. The authors aim to demonstrate the efficacy of our preoperative antibiotic immersion protocol of custom-made HA prosthesis, to prevent early implant infections. The authors compare this population to cranioplasties without preoperative antibiotic elution and those with anonstandardized antibiotic elution. The authors retrospectively analyzed data from patients referred to 6 different hospitals in northern Italy, in the period 2000 to 2020. Inclusion criteria were patients requiring reconstruction of thecal bone with HA prosthesis after post-traumatic decompressive surgery; age more than 18 years; detailed patient history and clinical data; and follow-up of minimum 6 months. A total of 77 cranioplasties were included in the study, along with 120 retrospective cases in comparison. Infections occurred in 2.6% of cranioplasties with antibiotic immersion compared to 7.8% of cranioplasties without. Even if nonsignificant, these results support our hypothesis that pretreatment of HA implants with antibiotic appears to prevent cranioplasty infections and could be a viable option to improve cranioplasty outcomes in the future.

Soft tissue variations influence HR-pQCT density measurements in a spatially dependent manner.

Significant weight loss following treatments for obesity undermines bone metabolism and increases bone turnover and fracture incidence. High resolution peripheral quantitative computed tomography (HR-pQCT) is widely used in skeletal heath assessment research to provide noninvasive bone parameter measurement (e.g. volumetric bone mineral density (vBMD)) with minimal radiation exposure. However, variation in body composition among study groups or longitudinal variations within individuals undergoing significant weight change will generate artifacts and errors in HR-pQCT data. The purpose of this study is to determine the influence of these artifacts on the measurement of vBMD. We designed a custom-made hydroxyapatite (HA)-polymer phantom surrounded by layers of reusable gel pack and hydrogenated fat to mimic the distal tibia and the surrounding lean and fat tissue. Four different thicknesses of fat were used to mimic the soft tissue of increasingly overweight individuals. We then evaluated how a change in soft tissue thickness influenced image quality and vBMD quantification within total, trabecular, and cortical bone compartments. Based on these data, we applied a data correction to previously acquired clinical data in a cohort of gastric bypass patients. In the phantom measurements, total, trabecular, and cortical vBMD increased as soft tissue thickness decreased. The impact of soft tissue thickness on vBMD varied by anatomic quadrant. When applying the soft tissue data correction to a set of clinical data, we found that soft tissue reduction following bariatric surgery can lead to a clinically significant underestimation of bone loss in longitudinal data, and that the effect is most severe in the cortical compartment. HR-pQCT-based vBMD measurement accuracy is influenced by soft tissue thickness and is spatially inhomogeneous. Our results suggest that variations in soft tissue thickness must be considered in HR-pQCT studies, particularly in studies enrolling cohorts with differing body composition or in studies of longitudinal weight change.

Custom-Made Porous Hydroxyapatite Cranioplasty in Patients with Tumor Versus Traumatic Brain Injury: A Single-Center Case Series

Cranioplasty is a common neurosurgical procedure with the goal of restoring skull integrity. Custom-made porous hydroxyapatite prostheses have long been used for cranial reconstruction in patients with traumatic brain injury. We present a large consecutive series of 2 groups of patients undergoing cranioplasty with hydroxyapatite custom bone and compare the adverse events (AEs) between the 2 groups. We examined a series of consecutive patients who underwent cranioplasty using custom-made porous hydroxyapatite implants following tumor resection and traumatic brain injury at a single center between March 2003 and May 2018. The implants were designed and produced according to the surgeon's specifications and based on the patient's computed tomography scan data obtained through a standardized protocol. AEs were recorded. Information on 38 patients with tumor and 39 patients with traumatic brain injury was collected and analyzed. A significant difference in the timing of surgery was found between the 2 groups; single-stage surgery was performed in 84% of patients in the tumor versus 8% of those in the traumatic brain injury group (P < 0.0001). The rate of AEs was not significantly different between the 2 groups (P= 0.4309) and was not related to the timing of surgery. Custom-made hydroxyapatite cranioplasty is a solution for cranial reconstruction in patients with cranial tumors. The low incidence of AEs in a consecutive series of patients with either trauma or tumors demonstrates that these prostheses represent a safe solution independent of the characteristics of cases.

Custom-made hydroxyapatite for cranial repair in a specific pediatric age group (7-13years old): a multicenter post-marketing surveillance study.

CustomBone Service (CBS) is a patient-specific, biocompatible, and osteoconductive device made of porous hydroxyapatite, indicated for cranial reconstruction in adults and children. Adult literature data report a failure rate of about 8%. The aim of this Post-Marketing Surveillance study is to verify the hypothesis that CBS in children aged 7-13years old shows a failure rate not superior to adults. Inclusion criteria were age at implantation ranging 7-13years old, with at least 1year elapsed from the date of surgery. The degree of satisfaction of surgeons and patients was assessed. Data about 76 implants in 67 patients (M:F = 41:26) were obtained from 28 centers across 7 European countries. The mean age at surgery was 10.03 ± 1.72years, with age stratification almost equally distributed. Fifty-nine subjects received one CBS, 7 subjects two and one subject received three CBS. Main etiologies were trauma (60.5%), malformation (11.8%), bone tumor (10.5%), and cerebral tumor (7.9%). Main indications to CBS were decompression (47.4%), autologous bone resorption (18.4%), tumor resection (11.8%), malformation (9.2%), comminuted fracture (5.3%), and other materials rejection (5.3%). Main implantation sites were fronto-parieto-temporal (26.3%), parietal (23.7%), frontal (11.8%), fronto-temporal (10.5%), and parieto-temporal (7.9%). CBS was chosen as first line of treatment in 63.1% of the cases. Mean follow-up was about 36months. Eleven adverse events (14.5%) were reported in nine devices. Five CBS required explantation (three cases of infection, one fracture, and one mobilization). Failure rate was 6.58%, which is statistically not superior to the explantation rate recorded in adults (two-sided 95%, CI 2.2-14.7%). Satisfaction of surgeons and patients was of about 95%. CBS is a safe and effective solution for cranial repair in pediatric patients. In particular, over the age of 7, CBS shows a rate of failure as low as in adults.

Independent Factors Affecting Postoperative Complication Rates After Custom-Made Porous Hydroxyapatite Cranioplasty: A Single-Center Review of 109 Cases

Cranioplasties are an important neurosurgical procedure not only for improved cosmesis but also for improved functional recovery after craniectomy with a large cranial defect. The aim of this study was to identify predictive factors of postcranioplasty complications using custom-made porous hydroxyapatite cranioplasty. Retrospective review was performed of all patients who underwent a reconstructive cranioplasty using custom-made hydroxyapatite at our institution between February 2008 and September 2017. Postoperative complications considered included bacterial infection, seizures, hydrocephalus requiring ventricular shunt placement, and cranioplasty-to-bone shift. Variables associated at P < 0.1 level in unadjusted analysis were entered into backward stepwise logistic regression models. Of 109 patients included, 15 (13.8%) experienced postoperative infection, with craniectomy performed at an outside institution (adjusted odds ratio [OR] 10.37 [95% confidence interval [CI], 2.03-75.27], P= 0.012) and a previous infection at the surgical site (adjusted OR 6.15 [95%CI, 1.90-19.92], P= 0.003) identified as independent predictors. Six patients (5.5%) experienced postoperative seizures, with stroke (ischemic and hemorrhagic) as a reason for craniectomy (adjusted OR 11.68 [95% CI, 2.56-24.13], P < 0.001) and the presence of seizures in the month before cranioplasty (adjusted OR 9.39 [95% CI, 2.04-127.67], P= 0.002) identified as independent predictors. Four patients (3.7%) experienced postcranioplasty hydrocephalus necessitating shunt placement, and 5 patients (4.6%) experienced cranioplasty-to-bone shift ≥5 mm, but no significant predictive factors were identified for either complication. This study identified possible predictive factors for postcranioplasty complications to help identify at-risk patients, guide prophylactic care, and improve morbidity of this important surgical procedure.

Histological assessment of porous custom-made hydroxyapatite implants 6 months and 2.5 years after cranioplasty.

Background:In cranial reconstruction, the features of artificial bone differ. Custom-made porous hydroxyapatite (HAp) implants for cranioplasty have been used all over the world because of their good cosmetic, biocompatibility, and osteoconductive properties. Surgical techniques were analyzed, and histological assessment of new bone formation in the hydroxyapatite was performed.Methods:Over a 6-year time period, 41 patients underwent cranioplasty using a custom-made three-dimensional hybrid pore structured hydroxyapatite (3DHPoHAp) implant. The surgical techniques and histological evaluations of 3DHPoHAp in 2 cases, removed 6 months and 2.5 years after cranioplasty, are described.Results:Using 3DHPoHAp, cranioplasty was successfully performed for all patients. The implant fit the bone defect exactly, and surgical manoeuvres were simple and easy. All implants were firmly fixed using a titanium plate, and postoperative infection occurred in 1 patient (2.4%). New bone formation was seen in 2 cases 6 months and 2.5 years after cranioplasty. Osteoblasts were progressing to the stoma at various depths, and bone tissue had ripened. Furthermore, lamellar structure was observed in the case at 2.5 years.Conclusions:In this study, there was a low infection rate, and new bone formation was seen in vivo after cranioplasty. This study also demonstrated that the 3DHPoHAp implant is a good candidate for cranial bone implants because its good osteoconductivity and biocompatibility.

Cranioplasty after Decompressive Craniectomy Caused an Intracerebral Hemorrhage: A Case Report

Decompressive craniectomy is a common practice for patients with intracranial hypertension. Secondary rigid structural reconstruction following craniectomy can release the effects of atmospheric pressure on the brain, and the brain can become dilated. Although some cases with complications induced by cranioplasty, such as intracranial hematoma, have been reported, no clinical cases with intracerebral hemorrhage after rigid reconstruction have been reported. This case report describes a 39-year-old man with a skull defect following clipping with simultaneous decompressive craniectomy for a subarachnoid hemorrhage. About 25 months later, cranioplasty using a custom-made hydroxyapatite (HAP) ceramic implant was performed. Immediately after the operation, intracerebral hemorrhage was detected on the opposite side by computed tomography (CT). However, there were no physical or neurological findings, the hematoma was completely absorbed within 3 weeks postoperatively, and the skull retained a good shape. This case suggests that rigid reconstruction of a skull defect can influence intracranial conditions, and early postoperative CT is important to detect complications.

Surgical pitfalls with custom-made porous hydroxyapatite cranial implants

Aim: Cranioplasty implants are used primarily in cases of surgical cranial decompression following pathological elevations of intracranial pressure. Available bone substitutes include porous hydroxyapatite (HA) and polymethylmethacrylate. Whichever material is used, however, prosthetic cranial implants are susceptible to intra- and postsurgical complications and even failure. The aim of this study was to investigate such occurrences in HA cranioplasty implants, seeking not only to determine the likely causes (whether correlated or not with the device itself) but also, where possible, to suggest countermeasures. Methods: We analyzed information regarding failures or complications reported in postmarketing surveillance and clinical studies of patients treated worldwide with custom-made HA cranial implants (Custom Bone Service Fin-Ceramica Faenza, Italy) in the period 1997-2013. Results: The two most common complications were implant fractures (84 cases, 2.9% of the total fitted) and infections (51 cases, 1.77%). Conclusion: Although cranioplasties are superficial and not difficult types of surgery, and use of custom-made implants are often considered the easy option from a surgical perspective, these procedures are nonetheless plagued by potential pitfalls. If performed well they yield more than satisfactory results from the points of view of both the patient and surgeon, but lack of appropriate care can open the door to numerous potential sources of failure, which can compromise-even irreparably-the ability to heal.

Assessment of the RIVET fixation system for cranioplasty using the pull-out technique

Cranioplasty using custom-made hydroxyapatite (HAP) ceramic implants is a common procedure to repair skull defects. However, commercially available titanium screws are only minimally stabilized due to characteristic brittleness. We developed the RIVET technique which involves fixing a bioabsorbable plate atop a HAP block using bioabsorbable screws extending beyond both layers, and evaluated fixation strength using the pull-out test and microtomography. Three experimental conditions were compared: a non-RIVET group, RIVET group, and dry skull control group. Pull-out strength significantly differed across groups (non-RIVET group, 1.33 ± 1.21 kgf; RIVET group, 4.46 ± 0.84 kgf; and control group, 6.99 ± 1.14 kgf, P < 0.01). Microtomography of the dry skull control group revealed thread grooves fitted to the screws. The non-RIVET and RIVET groups presented fewer thread grooves than the control group, and the screws did not fit perfectly to the HAP block. However, fixation in the RIVET group was more stable, as the rivet was firmly lodged into the implant. In conclusion, by melting and creating the rivet, pull-out strength can be increased and rigid stabilization of HAP can be obtained. This technique uses commercially available absorbable plate and screws, and thus can be used widely in clinical applications involving HAP blocks with different porosities and thicknesses.

The RIVET

Cranioplasty using custom-made hydroxyapatite (HAP) ceramic implants is a common procedure for the repair of skull defects. The advantages of using HAP are that it is nonmetallic, unlike titanium; biocompatible; and osteoconductive. Furthermore, it can be molded to any complex shape that may be needed. A disadvantage is that titanium screws and plates are in development for its fixation. We developed a technique for implant fixation using bioabsorbable screws and plates, and named this technique RIVET: resorbable immobilization for vacuolar en bloc technique.Before each operation, the implant was customized for the patient in question on the basis of models prepared using computed tomography data. The bioabsorbable plates were attached to the implant by drilling, tapping, and screwing, as shown in the video (http://links.lww.com/SCS/A43). The interior portion of the screw was then melted to flatten it against the internal surface of the implant, forming a rivet to join the plate and HAP implant.We used this technique for cranial reconstruction in 2 patients, with satisfying and functional results. We did not encounter any complications.In conclusion, the technique described here allows surgeons to fix implants and plates together more rigidly, giving a better result than possible with previous methods.

Vertical Ridge Augmentation of the Atrophic Posterior Mandible With Custom-Made, Computer-Aided Design/Computer-Aided Manufacturing Porous Hydroxyapatite Scaffolds

The present study describes a new protocol for the manufacturing of custom-made hydroxyapatite scaffolds using computer-aided design/computer-aided manufacturing (CAD/CAM), to augment posterior mandibular bone and minimize surgery when severe atrophy is present. Computed tomographic images of an atrophic posterior mandible were acquired and modified into a 3-dimensional (3D) reconstruction model. This model was transferred as a stereolithographic file to a CAD program, where virtual 3D reconstructions of the alveolar ridge were performed, drawing 2 anatomically shaped, custom-made scaffolds. Computer-aided-manufacturing software generated a set of tool-paths for manufacture on a computer-numerical-control milling machine into the exact shape of the 3D projects. Clinically sized, anatomically shaped scaffolds were generated from commercially available porous hydroxyapatite blocks. The custom-made scaffolds well matched the shape of the bone defects and could be easily implanted during surgery. This matching of the shape helped to reduce the time for the operation and contributed to the good healing of the defects. At the 6-month recall, a newly formed and well-integrated bone was observed, completely filling the mandibular posterior defects, and implants were placed, with good primary stability. At the 1-year follow-up examination, the implant-supported restorations showed a good functional and esthetic integration. Although this is an interim report, this study demonstrates that anatomically shaped custom-made scaffolds can be fabricated by combining computed tomographic scans and CAD/CAM techniques. Further studies are needed to confirm these results.

Autologous bone flap versus hydroxyapatite prosthesis in first intention in secondary cranioplasty after decompressive craniectomy: A French medico-economical study

Background and purposeDecompressive craniectomy is the most common justification for cranioplasty. A medico-economial study based on the effective cost of the hydroxyapatite prosthesis, the percentage of autologous bone graft's loss due to bacterial contamination and the healthcare reimbursment, will allow us to define the best strategy in term of Healthcare economy management for the cranioplasties. A comparison was made between the two groups of patients, autologous bone flap versus custom-made prosthesis in first intention, based on the clinical experience of our department of neurosurgery. ResultsNo differences was shown between the two groups of patients, in terms of lenght of in-hospital stay and population's characteristics or medical codification. The mean cost of a cranioplasty using the autologous bone graft in first intention was €4045, while the use of hydroxyapatite prosthesis led to a cost of €8000 per cranioplasty. ConclusionIn term of Healthcare expenses, autologous bone flap should be used in first intention for cranioplasties, unless the flap is contaminated or in specific indications, when the 3D custom-made hydroxyapatite prosthesis should be privilegied.

Maxillary sinus augmentation using computer‐aided design/computer‐aided manufacturing (CAD/CAM) technology

Maxillary sinus augmentation is a common method for increasing bone height for insertion of dental implants. In most cases, the graft is manually cut into a roughly appropriate shape by visual estimation during the operation; accordingly, the shape of the graft depends considerably on the experience of the surgeon. We have developed a computer-aided design/computer-aided manufacturing (CAD/CAM) technique to generate custom-made block grafts for sinus augmentation, and a customized cutting guide to precisely position the lateral wall and facilitate membrane elevation, using cone-beam computed tomography (CBCT). Custom-made blocks of hydroxyapatite (HA) were preoperatively cut to the required shape, based on a three-dimensional (3D) simulation, using CAD/CAM technology. The custom-made HA blocks were used for sinus augmentation. Five patients underwent bilateral sinus elevation with custom-made HA blocks. Six months later, implants were placed. Two years after placement, all implants were in function. No clinical or prosthetic complications were encountered. We present a CAD/CAM technique for the fabrication of custom-made block grafts for sinus augmentation.

Tolérance clinique et degré d’ossification des cranioplasties en hydroxyapatite de larges défects osseux

ObjectiveCranioplasty is an everyday concern in neurosurgery, especially in decompressive craniectomy cases. Our surgical team uses custom-made hydroxyapatite implants for large and/or complex defects. Patients and methodEight patients had a custom-made prosthesis. Each of them has been reviewed by an independent observer. Each patient described his feeling of satisfaction, using a questionnaire, graduated from “A” (really satisfied) to “D” (unsatisfied). Each of them also underwent a CT-scan (helicoidal acquisition, 0.6mm thick for multiplanar reconstruction) to evaluate qualitatively the ossification graduated from “0” (no ossification) to “5” (continuous ossification). Maximal under-prosthetic bone thickness, intra-prosthetic calcic density were also reported. ResultsSupervision delay was 43.7 months [6–99 months], average defect surface was 85.5cm2 [27.6–137.6cm2], the craniectomy etiologies were intracranial hypertension (seven patients) and calvarial invasion (one patient). Implant tolerance was reparted in “A” score (50%) and “B” score (50%). Concerning ossification, six patients (75%) had a score of “2” or less and two patients had a score of “3” or “4”. DiscussionHydroxyapatite custom-made implants for cranioplasty appear to be ideal for good aesthetic and tolerance results, but their ossification is hardly analyzed due to the prosthesis density higher than the bone's density. This is why we recommend them for children and in cases of complex defects such as pterion location.

Histologically demonstrated skull bone integration in a hydroxyapatite prosthesis in a human

Dear Editor,Surgical treatment for skull bone defects consists ofcranioplasty using different materials including polyme-thylmethacrylate, titanium, resin prostheses, polyesther andceramics [1–4]. The increasing tendency to employ decom-pressive craniectomy for the treatment of cerebral traumahas led to the need for high-quality materials that canpossibly be both resistant and biocompatible. An additionaladvantage could be osteoinductivity, with promotion ofosteoblastic migration across the prosthesis. This propertycan be found in porous custom-made hydroxyapatite (HA)prostheses, which have been shown to induce osteogenesisin experimental animal models [4]. We had the opportunityto demonstrate that osteogenesis induced by bioceramicprotheses occurs also in humans.A 69-year-old woman had been operated on for leftatypical parasagittal meningioma in 2006 at the Departmentof Neurosurgery of the Istituto Neurologico “Carlo Besta”in Milan. The need to remove the bone flap developedduring surgery as the bone was infiltrated by the lesion.One year after her first surgery, the patient underwentcranioplasty with a previously manufactured custom-madehydroxyapatite ceramic new flap. The prosthetic bone flapwas obtained by three-dimensional stereolithography basedon a computerized tomography 3D model of the patient’sskull and bone defect. The material consists of poroushydroxyapatite (including both macropores and micro-pores). Because of recurrence of the meningioma, sheunderwent Cyberknife therapy and, subsequently, furthersurgery 2 years after the first operation. The size of thelesion and the tight adherence of the ceramic material to theskull forced us to remove the prosthesis together with aportion of the surrounding skull, thus resulting intoenlargement of the craniotomy. The removed flap was thensent for histological examination, which revealed thepresence of fresh bone tissue along the superior margin ofthe prosthesis and of bone formation along the interface(Fig. 1).The thickness (in frontal sections) of both the syntheticand the newly developed bone was 4.38 mm; the thicknessof the autologous bone layer was 0.13 mm.The search for perfect or nearly perfect bone integrationin bone prostheses implanted as cranioplasty has led to thedevelopment of new materials that could help the fusionwith the bone edges. In our patient porous hydroxyapatiteshowed these characteristics. The mainstay is obviously thebone integration at the interface with the used material, butin our case new bone formation occurred also along thesuperior surface of the prosthesis. Although several reportsof radiologically demonstrated successful bone-prosthesisfusion exist [5], this is the first report in the literature ofeffective bone-HA integration in humans as demonstratedin the postoperative histological examination.

Accuracy of volumetric bone mineral density measurement in high-resolution peripheral quantitative computed tomography

Accurate bone mineral density (BMD) quantification is critical in clinical assessment of fracture risk and in the research of age-, disease-, and treatment-related musculoskeletal changes. The development of high-resolution peripheral quantitative computed tomography (HR-pQCT) imaging has made possible in vivo assessment of compartmental volumetric BMD (vBMD) and bone micro-architecture in the distal radius and tibia. HR-pQCT imaging relies on a polychromatic X-ray source and therefore is subject to beam hardening as well as scatter artifacts. In light of these limitations, we hypothesize that the accuracy of HR-pQCT vBMD measurement in the trabecular compartment (vBMD trab) is not independent of bone density and geometry, but rather influenced by variations in trabecular bone volume fraction and cortical thickness. The goal of this study, therefore, was to evaluate the accuracy of HR-pQCT vBMD trab measurement in the radius and tibia, and to determine the dependence of this measurement on geometric and densitometric parameters. Our approach was to use a series of idealized hydroxyapatite (HA) phantoms with varying densities and geometries to quantify the accuracy of HR-pQCT analysis. Two sets of custom-made HA phantoms designed to mimic the distal tibia and distal radius were manufactured. Geometric and densitometric specifications were based on a dataset of healthy volunteers and osteopenic patients. Multiple beam hardening correction (BHC) algorithms were implemented and evaluated in their ability to reduce measurement error. Substantial errors in measured vBMD trab were found. Overestimation of vBMD trab increased proportional to cortical shell thickness and decreased proportional to insert density. The most pronounced vBMD trab overestimation therefore occurred in the phantoms with the lowest insert densities and highest shell thickness, where error was as high as 20 mg HA/cm 3 (33%) in the radius phantom and 25 mg HA/cm 3 (41%) in the tibia phantom. Error in vBMD trab propagates to the calculation of micro-architectural measures; 41% error in vBMD trab will produce 41% error in volume fraction (BV/TV) and trabecular thickness (Tb.Th), and 5% error in trabecular separation (Tb.Sp). BHC algorithms supplied by the manufacturer failed to eliminate these errors. Our results confirm that geometric and densitometric variations influence the accuracy of HR-pQCT vBMD trab measurements, and must be considered when interpreting data across populations or time-points.

Image-guided cranial osteoma resection and bioceramic porous hydroxyapatite custom-made reconstruction in a one-step surgical procedure. Technical notes and illustrative case

Removal of a large cranial tumour and reconstruction of the consequent bone defect in the same surgical setting is an ordinary procedure. A custom-made hydroxyapatite ceramic reconstruction of a cranial bone defect is a modern option that currently needs a preoperative stage of studying the bone defect and designing the implant. Consequently, if a reconstructive hydroxyapatite-based procedure after a cranial tumour resection is the aim, a two-stage surgery is necessary. The authors investigated the possibility of performing this procedure in a one-step surgery by the use of a neuronavigation system. Preoperatively, an epoxy-resin model is built by stereolithography on three-dimensional (3D) cranial computed tomographic (CT) scan data of the patient affected by the cranial tumour. Afterwards, the implant is designed on the base of the planned bone flap that the surgeon simulates on the model for the tumour resection. The CT scan of the patient is fused in the neuronavigational system with a 3D cranial CT scan performed on the model without the planned bone flap. Intra-operatively, the surgeon is guided by the neuronavigational system to remove the cranial tumour through the craniotomy preoperatively planned on the model and, for this reason, perfectly matching the prosthesis for shape and size. In an illustrative case, a 26-year-old woman presented to the authors' attention for a large growing fronto-temporal osteoma. Because of the site of the tumour and the consequent challenging reconstruction of the bone defect, it was decided to attempt the cranioplasty with a custom-made hydroxyapatite ceramic implant. The removal of the osteoma and reconstruction with a hydroxyapatite ceramic implant was done in a one-step surgery. Seriate postoperative cranial CT scans showed a satisfying 3D result. Surgical removal of a cranial bone tumour and optimal reconstruction with a custom-made hydroxyapatite ceramic implant is an appealing procedure that can be carried out in a one-step surgery by means of an intraoperative image-guidance system.

Short term result of revision total hip replace-ment with custom-made hydroxyapatite spacers

Short term result of revision total hip replace-ment with custom-made hydroxyapatite spacers