Gentamicin loading of calcium phosphate implants: implications for cranioplasty

Exploring complications following cranioplasty after decompressive hemicraniectomy: A retrospective bicenter assessment of autologous, PMMA and CAD implants

Cranioplasty (CP) after decompressive hemicraniectomy (DHC) is a common neurosurgical procedure with a high complication rate. The best material for the repair of large cranial defects is unclear. The aim of this study was to evaluate different implant materials regarding surgery related complications after CP. Type of materials include the autologous bone flap (ABF), polymethylmethacrylate (PMMA), calcium phosphate reinforced with titanium mesh (CaP-Ti), polyetheretherketone (PEEK) and hydroxyapatite (HA). A retrospective, descriptive, observational bicenter study was performed, medical data of all patients who underwent CP after DHC between January 1st, 2016 and December 31st, 2022 were analyzed. Follow-up was until December 31st, 2023. 139 consecutive patients with a median age of 54 years who received either PMMA (56/139; 40.3%), PEEK (35/139; 25.2%), CaP-Ti (21/139; 15.1%), ABF (25/139; 18.0%) or HA (2/139; 1.4%) cranial implant after DHC were included in the study. Median time from DHC to CP was 117 days and median follow-up period was 43 months. Surgical site infection was the most frequent surgery-related complication (13.7%; 19/139). PEEK implants were mostly affected (28.6%; 10/35), followed by ABF (20%; 5/25), CaP-Ti implants (9.5%; 2/21) and PMMA implants (1.7%, 1/56). Explantation was necessary for 9 PEEK implants (25.7%; 9/35), 6 ABFs (24.0%; 6/25), 3 CaP-Ti implants (14.3%; 3/21) and 4 PMMA implants (7.1%; 4/56). Besides infection, a postoperative hematoma was the most common cause. Median surgical time was 106 min, neither longer surgical time nor use of anticoagulation were significantly related to higher infection rates (p = 0.547; p = 0.152 respectively). Ventriculoperitoneal shunt implantation prior to CP was noted in 33.8% (47/139) and not significantly associated with surgical related complications. Perioperative lumbar drainage, due to bulging brain, inserted in 38 patients (27.3%; 38/139) before surgery was protective when it comes to explantation of the implant (p = 0.035). Based on our results, CP is still related to a relatively high number of infections and further complications. Implant material seems to have a high effect on postoperative infections, since surgical time, anticoagulation therapy and hydrocephalus did not show a statistically significant effect on postoperative complications in this study. PEEK implants and ABFs seem to possess higher risk of postoperative infection. More biocompatible implants such as CaP-Ti might be beneficial. Further, prospective studies are necessary to answer this question.

Cranioplasty in Brain Tumor Surgery: A Single-Center Retrospective Study Investigating Cranioplasty Failure and Tumor Recurrence

OBJECTIVE

Cranioplasty with synthetic implant can be performed to restore function and form of the skull after resection of malignancy infiltrating the bone. The aim of this study was to examine the rate of implant failure and tumor recurrence in patients undergoing nonautologous cranioplasty and tumor resection.

METHODS

In this retrospective single-center study, 48 patients were identified who had undergone cranioplasty with synthetic implants after tumor resection between 2010 and 2020. The medical records were analyzed to investigate patient demographics, surgery data, cranioplasty failure rates, and rate of tumor recurrence.

RESULTS

Cranioplasty failed in 8 patients. The median time to implant failure was 220 days with most failures occurring within 1 year (5 of 8). There was no significant difference in rate or time to failure between the different cranioplasty materials (P = 0.39). Low body mass index (P < 0.05), previous craniectomy/cranioplasty (P < 0.05), previous radiation therapy to the brain/skull (P < 0.05), and skin closure with sutures (P < 0.05) were associated with an increased risk of implant failure. Tumors recurred in 15 patients.

CONCLUSIONS

Cranioplasty surgery with synthetic implants carries a relatively high risk of failure, regardless of type of cranioplasty material used. Skin closure with staples may be beneficial in these patients.

Histological Processing of CAD/CAM Titanium Scaffold after Long-Term Failure in Cranioplasty

Cranioplasty is a frequently performed procedure after craniectomy and includes several techniques with different materials. Due to high overall complication rates, alloplastic implants are removed in many cases. Lack of implant material osseointegration is often assumed as a reason for failure, but no study has proven this in cranioplasty. This study histologically evaluates the osteointegration of a computer-aided design and computer-aided manufacturing (CAD/CAM) titanium scaffold with an open mesh structure used for cranioplasty. A CAD/CAM titanium scaffold was removed due to late soft tissue complications 7.6 years after cranioplasty. The histological analyses involved the preparation of non-decalcified slices from the scaffold’s inner and outer sides as well as a light-microscopic evaluation, including the quantification of the bone that had formed over the years. Within the scaffold pores, vital connective tissue with both blood vessels and nerves was found. Exclusive bone formation only occurred at the edges of the implant, covering 0.21% of the skin-facing outer surface area. The inner scaffold surface, facing towards the brain, did not show any mineralization at all. Although conventional alloplastic materials for cranioplasty reduce surgery time and provide good esthetic results while mechanically protecting the underlying structures, a lack of adequate stimuli could explain the limited bone formation found. CAD/CAM porous titanium scaffolds alone insufficiently osseointegrate in such large bone defects of the skull. Future research should investigate alternative routes that enable long-term osteointegration in order to reduce complication rates after cranioplasty. Opportunities could be found in mechano-biologically optimized scaffolds, material modifications, surface coatings, or other routes to sustain bone formation.

Tethered brain: disentangling unintentional brain-mesh interfaces. Illustrative case

BACKGROUND

Surgical meshes have found widespread use in neurosurgical practice. While commonly recognized risks of synthetic mesh include infection, exposure of mesh implants, and foreign body reaction, the risk of mesh tethering to neural structures is often overlooked.

OBSERVATIONS

The authors presented the first case, to their knowledge, of the disentanglement of mesh interfaced to cortical tissue. The patient, a 68-year-old woman, presented with severe intractable seizure disorder and worsening left hand function and incoordination after meningioma resection and cranioplasty 9 years earlier. Magnetic resonance imaging (MRI) demonstrated interval progression of macrocystic encephalomalacia involving the right supplementary motor area, with fluid-attenuated inversion recovery signal extending posteriorly into the right primary motor cortex. Both computed tomography and MRI suggested potential tethering of the cortex to the overlying cranioplasty mesh. Because of the progressive nature of her condition, the decision was made to surgically remove the tethered mesh.

LESSONS

De-tethering brain parenchyma from surgical mesh requires careful microdissection and judicious use of electrocautery to minimize further tissue damage and preserve neurological function. This inadvertent complication evinces the importance of using dural substitutes when unable to primarily repair the dura to prevent scarring and tethering of neural tissues to synthetic cranioplasty materials.

Bone formation in custom-made cranioplasty: evidence of early and sustained bone development in bioceramic calcium phosphate implants. Patient series

BACKGROUND

Implant failure (IF) rates in cranioplasty remain high despite efforts to reduce the incidence. New biomaterials may be part of the solution for this problem. Formation of autologous bone in implants may reduce rates of infection and subsequent failure.

OBSERVATIONS

Four patients with calcium phosphate implants supported by titanium mesh and undergoing surgery for reasons unrelated to IF were included in this series. Samples from the implants were microscopically examined. Pathological studies proved the formation of autologous bone in the calcium phosphate implants.

LESSONS

Bone and blood vessel formation in the implants and diminished foreign body reaction to autologous bone may reduce the rates of IF.