Patient-Specific Implants for Cranioplasty: Is There an Ideal Implant?

Introduction: While the ideal synthetic material for cranioplasty remains elusive, the use of prefabricated alloplastic implants has many proposed advantages. Custom implants that fit a patient’s specific defect can reduce operative time and improve contour. Polymethyl-methacrylate (PMMA) has a long history of use for large cranioplasty defects. However, advances in 3D printing have led to an increased popularity of polymer alloplastic materials such as polyether-ketone-ketone (PEKK) implants. No direct comparisons of PMMA and PEKK exist in the literature. We present a retrospective analysis of PMMA and PEKK patient-specific implants at a single institution.

Methods: A retrospective chart review was performed identifying patients undergoing patient-specific implant (PSI) cranioplasty at Northwestern Memorial Hospital between January 2013 and July 2017. Medical records were reviewed for patient characteristics, indications, surgical details, implant type, and post-operative complications. Patients were divided into groups based on cranioplasty type (PMMA vs PEKK). Comparisons between groups were made using the student’s t test and Fisher exact test. 

Results: 74 patients underwent PSI cranioplasty during the study period. Thirty-five (47.3%) had PMMA implants and 39 (52.7%) had PEEK implants. Patients were 51% male with an average age of 44. There were no differences between groups except for follow up length (17 months vs 7 months, p=0.002). Plastic surgery involvement was more common in patients with a history of infectious complications (46% v 26%). The overall failure rate for PSI cranioplasty was 14.3%. There was no difference in failure rate when comparing PMMA to PEKK (14.7% vs 13.9%, p>0.05). There was no significant difference in complications between PMMA and PEKK (41.0% vs 34.3%, P>0.05). Infection rates were equivalent between groups (17.1% vs 16.7%). Delayed wound healing was also equivalent (8.8% vs 13.9%, p>0.05). When reviewing the 10 failures, 7 occurred in patients with prior infection, 5 in patients with a history of radiation, and 3 with both. 

Conclusions: PMMA and PEKK have similar complication profiles for patient-specific implant cranioplasty. Complication rates remain high for both materials, with wound healing and infectious complications and radiation carrying high risk of implant failure.