ReviewBiomaterials and implants for orbital floor repair☆
Introduction
Orbital floor fractures, alone or in conjunction with other facial skeletal damage, are the most commonly encountered midfacial fractures, second only to nasal ones. According to Ng et al. [1] and Chang and Manolidis [2], orbital floor fractures were first described by MacKenzie in 1844 in Paris. More than a century later, in 1957, Smith and Regan [3] described inferior rectus muscle entrapment with decreased ocular motility in the setting of an orbital fracture and coined the term “blow-out fracture”. Since the 1960s different surgical routes have been proposed for the effective management of orbital floor fractures [4], [5], [6], [7], [8], [9], [10], [11].
It should be taken into account that the management of orbital floor injuries is complicated not only by their technical difficulty per se, but also by the required extensive medical competencies, ranging from the maxillofacial to otolarygological to ophthalmic fields, and by the multitude of factors necessary to make a correct decision as to the proper timing of the repair.
In addition to timing- and surgery-related issues, another key factor in the treatment of orbital fractures is the choice of the material used for tissue(s) reconstruction. A wide number of studies describing orbital fracture repair with a considerable variety of autogenous, allogenic and alloplastic materials are available in the literature. However, direct comparison between different materials are rather rare and, therefore, it is not trivial to draw definite conclusions as to which material is best suited to repair these injuries. The present review addresses this issue: specifically, the advantages and limitations of currently adopted biomaterials and implants are critically examined and possible new research directions towards a truly ideal device are described and discussed.
The article can be divided into three parts, devoted to presenting an essential medical background, a comprehensive materials/implants review and some indications/remarks for material choice/prospective research, respectively. The first part, Section 2, gives the reader a concise overview of the features, treatment and complications of orbital floor fractures. In this context Table 1 provides a short glossary of the medical terms that are not explained directly in the text or that may be unclear or unknown to non-specialist readers. The second part, Sections 3–8, gives the different classes of biomaterials and implants used to treat orbital floor fractures are extensively reviewed. The third part, Sections 9–11, critically compares and discusses the performances of the different materials and implants in current use and forecasts about future challenges are presented.
Section snippets
Aetiology and features
Damage to the facial skeleton is usually the result of low, medium or high velocity trauma due, for instance, to a motor vehicle or traffic accident. A fracture in the orbital floor commonly causes herniation of the orbital fat and other orbital content into the maxillary sinus(es), which results in an increase in the orbital volume (Fig. 1). Orbital floor fractures can occur as isolated injuries or in combination with extensive facial bony disruption. The orbital floor is most vulnerable to
Materials for orbital floor reconstruction
Basically, the goal of an orbital floor implant is to repair the traumatic defect, lifting the eyeball into its correct position and thereby avoiding enophthalmos. An ideal implant biomaterial should be (i) biocompatible, (ii) available in sufficient quantities, (iii) strong enough to support the orbital content and the related compressive forces, (iv) easy to shape to fit the orbital defect and regional anatomy, (v) easily fixable in situ, (vi) not prone to migration, (vii) osteoinductive and
Biological materials
Over the years a wide range of biological materials has been tested in the field of orbital floor repair. They have been derived from human or animal tissues and could be used as transplants (autografts, allografts and xenografts) or treated to obtain suitable substances to be used as implant materials. In general, biological materials have problems, such as limited availability and morbidity at the harvest site for autologous tissues and the risk of viral infection and disease transmission
Hydroxyapatite and other calcium phosphates
Hydroxyapatite (HA), due to its chemical and crystallographic similarity to bone mineral, is an excellent material for bone defect repair [87]. Since the early 1990s HA and carbonated apatite cements have been commercially available as mouldable bone substitutes in the broad field of craniofacial reconstruction [88], [89], [90], [91]. Mathur et al. [92] reported an interesting overview of the use of HA cements in the context of craniofacial surgery, including orbital floor repair.
HA was also
Titanium
For many decades titanium has been successfully and extensively used in orthopaedics and dentistry to manufacture bone screws, joint endoprostheses and dental implants [108], [109], as well as in the field of craniofacial reconstruction and orbital floor repair [54], [110], [111], [112], [113], [114], [115], [116], [117], [118]. Titanium is highly biocompatible and, thanks to its physico-mechanical properties, is an ideal candidate for the reconstruction of bone defects requiring substitutes
Silicone
Silicone has been extensively proposed for almost 50 years as a suitable material for various surgical applications due to its attractive properties, including biological/chemical inertness, flexibility, ease of handling and low cost. In retinal detachment surgery, for instance, silicone elements for scleral buckling are the unique scleral implants approved for clinical use and commercially available worldwide [123].
In 1963 silicone was introduced by Lipshutz and Ardizone [124] in the management
Composites
HA-reinforced high density composite (HAPEX™) has been marketed and successfully used for several years as a bone replacement material in the context of orbital floor repair [177], [178] and middle ear prostheses [179]. Zhang et al. [180] recently suggested the use of a HA/PE composite material as a skull implant for the repair of cranial defects. The combination of stiff, osteoinductive but brittle HA with low modulus, tough and bioinert PE produces a biomedical composite exhibiting attractive
Overview of comparative studies – does an ideal biomaterial exist?
No generally recognised consensus exists on the best choice of biomaterials/implants for orbital floor reconstruction, but several options are at the surgeon’s disposal and available in the marketplace (Table 2). The choice of an optimal material for orbital skeleton repair is influenced by many factors, including the specific characteristics of the injury, cost, the patient’s clinical history and the experience/opinion of the surgeon.
It is worth underlining once more that a careful history and
Summary and indications for material choice
Orbital fractures due to trauma usually result in damage to the floor and the medial wall, the thinnest bone in the body. In some cases surgical treatment is not mandatory and drug therapy may be recommended, as previously discussed in Section 2.2. Clinical indications for fracture repair are the patient’s symptoms and generally include severe diplopia, entrapment of extraocular muscles, large fractures (>50% of the wall) and enophthalmos greater than 2 mm [2], [8], [12], [17]. If surgical
Concluding remarks and promises for the future
The data from the existing literature demonstrate that orbital floor reconstruction is often a complex issue and, at present, none of the biomaterials used in clinical practice can be really considered the ideal one. In the next few years the development of new biomaterials and implants exhibiting superior performance with respect to the existing commercial solutions would be highly desirable. These new products should be easily sterilizable and have ease of use by the surgeon. Specifically,
Acknowledgement
Dr Daniela Dolcino, Head of the Ophthalmology Ward at Ss. Antonio e Biagio Hospital, Alessandria, Italy, is gratefully acknowledged for stimulating and supporting the author in writing this article.
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This article is dedicated to Prof. Giuseppe Heer, a great ophthalmologist and Head Emeritus of the Ophthalmology Ward at Maria Vittoria Hospital, Turin, Italy, on occasion of his 60 years of clinical activity and 85th birthday.