This study presents the first multicentre cohort of patients with adequately reconstructed orbital fractures after trauma using UHMWPE implants. We aimed to evaluate the outcome of orbital reconstruction with Ultra High Molecular Weight Polyethylene (UHMWPE) implants by measuring the difference in orbital volume before and after the surgery in a clinical setting.

Orbital fractures represent a significant subset of craniofacial injuries [12, 13], and while small fractures can be managed conservatively, surgical intervention is often required to restore orbital anatomy and function [14]. Although the ideal material for reconstruction remains controversial, the following characteristics are widely accepted to provide the best results. The material should be biocompatible and non-carcinogenic. It should conform to the patient’s anatomy and retain its new shape. If alloplastic, the material should be inexpensive and readily available. It should not promote microbial growth or be allergenic, and it should be rigid enough to support the orbital contents.

Autogenous implants remain a viable option due to their biocompatibility, but donor site morbidity, harvesting time, and cosmetic concerns are some of the drawbacks that limit their potential [15, 16].

There are a variety of alloplastic materials available for orbital floor reconstruction, but to date, none seems to combine all of the above characteristics to make it an ideal material [17, 18]. PDS and Polyglactin 910/PDS (Ethisorb) patches, two widely used materials, have been shown to be associated with increased infection rates, as well as inferior globe position and progressive enophthalmos due to their flexible nature, thus recommending overcorrection of the globe during surgery [8, 19, 20]. Therefore, PDS is preferred for reconstruction of small defects [21] and 910/PDS for small to moderate defects (maximum 2 × 2 cm) [22]. Polypropylene mesh, a material commonly used in abdominal surgery that can be both resorbable and non-resorbable, is a viable alternative for medium-sized orbital floor fractures, but studies report persistent diplopia and enophthalmos in some cases [23, 24]. Titanium mesh, a stiffer and more stable material, has traditionally been used for larger defects [25, 26], but orbital adhesion with subsequent ocular motor dysfunction has been reported [27,28,29], and it interferes with radiographic examination and causes weathering sensations due to its metallic nature [30].

UHMWPE is a polymer that differs from the more familiar high-density polyethylene (HDPE) in terms of molecular weight and average chain length. In addition to its mass, the molecular structure of the polymer plays an important role in its physical and chemical properties. Its interconnected pore network allows rapid infiltration by the host tissue and promotes osteointegration, resulting in a reduced risk of implant migration and excellent long-term stability [7]. A meta-analysis of case series studies by Schellini et al. highlighted the advantages of porous polyethylene implants in the orbital region, demostrating a lower risk of implant exposure [31]. The extensive use of UHMWPE in weight-bearing anatomical regions such as hip and knee arthroplasty undoubtedly demonstrates its toughness and biocompatibility [32]. Therefore, it’s mechanical strength provides sufficient support for the orbital contents, yet its thermoplastic nature ensures optimal conformability to the patient’s anatomy [33, 34], resulting in precise orbital reconstruction. Our clinical results mirror those of our previous study in cadavers, with favourable results in terms of orbital volume restoration and functional improvement [10].

There are several potential complications that may arise due to the non-resorbable character of the implant, such as implant migration or long-term tissue response. From the three most popular alloplastic materials (porous polyethylene sheets PPE, Polypropylene mesh and Titanium implants), studies report superior outcomes with fewer complications using porous polyethylene sheets like marPOR-implant. Ghafar et al. studied 24 patients who received PPE sheets for reconstruction of orbital floor fractures, none of whom required reoperation or showed Signs of implant displacement [35]. Lupi et al. used UHMWPE in 32 patients with no implant migration, extrusion or enophthalmos [36]. Krishna et al. used PPE implant in 12 patients with fractures of the orbital floor and within the 1-year follow-up no implants were extruded and there were no signs of inflammatory reactions [37]. While our study demonstrated the effectiveness of UHMWPE implants to restore the volume in orbital fracture reconstruction and although no major complications were observed during the immediate post-operative period, a long-term follow-up is required to further ensure the implants overall efficacy.

The main limitation of this study is the use of only one specific orbital implant; therefore, no comparison between different implants can be made. Additionally, its radiolucency can be proven challenging to determine the exact position of the implant. While the immediate post-operative CT scans in this study allowed a sufficient differentiation due to the contrast with the surrounding bone and post-operative emphysema and oedema around the implant, future research could explore modifications to the implant material, such as the incorporation of radio-opaque additives to enhance its visibility and allow long-term monitoring.

Despite these considerations, the results of this study support the short-term safety of UHMWPE implants and concludes that marPOR-Implant is a reliable alternative material for orbital fracture reconstruction. UHMWPE offers several distinct advantages such as long-term stability, exceptional strength, and biocompatibility. In addition, it is easy to handle, contour, and process to the patient’s unique anatomy, resulting in accurate orbital volume restoration.