Biodegradable Fixation of the Orbital Rim After Lateral Orbitotomy

Biomechanical analysis of fixation methods for bone flap repositioning after lateral orbitotomy approach: A finite element analysis

OBJECTIVE

In ophthalmic surgery, different materials and fixation methods are employed for bone flap repositioning after lateral orbitotomy approach (LOA), yet there is no unified standard. This study aims to investigate the impact of different fixation strategies on orbital stability through Finite Element Analysis (FEA) simulations of the biomechanical environment for orbital rim fixation in LOA.

METHODS

A Finite Element Model (FEM) was established and validated to simulate the mechanical responses under various loads in conventional lateral orbitotomy approach (CLOA) and deep lateral orbital decompression (DLOD) using single titanium plate, double titanium plates, and double absorbable plates fixation methods. The simulations were then validated against clinical cases.

RESULTS

Under similar conditions, the maximum equivalent stress (MES) on titanium alloy fixations was greater than that on absorbable plate materials. Both under static and physiological conditions, all FEM groups ensured structural stability of the system, with material stresses remaining within safe ranges. Compared to CLOA, DLOD, which involves the removal of the lateral orbital wall, altered stress conduction, resulting in an increase of MES and maximum total deformation (MTD) by 1.96 and 2.62 times, respectively. Under a horizontal load of 50 N, the MES in FEM/DLOD exceeded the material's own strength, with an increase in MES and MTD by 3.18 and 6.64 times, respectively, compared to FEM/CLOA. Under a vertical force of 50 N, the MES sustained by each FEM was within safe limits. Bone flap rotation angles remained minimally varied across scenarios. During follow-up, the 12 patients validated in this study did not experience complications related to the internal fixation devices.

CONCLUSION

Under static or physiological conditions, various fixation methods can effectively maintain stability at the orbitotomy site, and absorbable materials, with their smoother stress transmission properties, are more suited for application in CLOA. Among titanium plate fixations, single titanium plates can better withstand vertical stress, while double titanium plates are more capable of handling horizontal stress. Given the change in the orbital mechanical behavior due to DLOD, enhanced fixation strength should be considered for bone flap repositioning.

Orbital Soft Tissue Displacement After Blow-Out Fracture Repair Using Poly (L-Lactide-Co-Glycolide) Polymer Plates Based on Image Fusion Technique

PURPOSE

To analyze the displacement of orbital soft tissue after blow-out fracture (BOF) repair with poly (L-lactide-co-glycolide) plates.

MATERIALS AND METHODS

In this retrospective study, all patients who had undergone repair operations for orbital BOF from 2017 to 2021 were evaluated. Poly (L-lactide-co-glycolide) plates were used as repair materials. Preoperative and postoperative computed tomography images were integrated into the same coordinate system applying image fusion technique and were compared to determine the maximum displacement of orbital tissue after surgical repair.

RESULTS

A total of 15 patients were included. Five were male, and 10 were female. Mean age was 33±16 years. Median waiting period was 18 (12-23) days. Six cases were medial wall fractures, 5 were floor fractures, and 4 were combined fractures. Maxillo-ethmoidal strut was involved in 4. Mean defect area was 176.52±108.48 mm 2 . Median interval between postoperative imaging examinations was 292 (223-600) days. Mean orbital tissue displacement was 2.6±1.8 mm. Using simple and multivariable linear regression analysis, the fracture defect area ( P =0.001) and maxillo-ethmoidal strut involvement ( P =0.013) were found to be significantly associated with orbital tissue displacement. Median orbital volume change was 0.804 (0.647-1.010) cm 3 . Average proptosis variation was 1.2±0.8 mm.

CONCLUSIONS

Poly (L-lactide-co-glycolide) plates were more suitable for orbital BOF with small defect size. Those with large defect or maxillo-ethmoidal strut involved might have greater tissue displacements due to decline of supporting strength of poly (L-lactide-co-glycolide) plates.

The Lateral Orbitotomy Approach for Intraorbital Lesions

The lateral orbitotomy approach (LOA) was first described by Kronlein in 1888 and has since been subject to many modifications and variations. When considering orbital approaches, the location of the pathology is often more important in decision making than the type of pathology. The LOA is best suited for access to intraconal and extraconal lesions lateral to the optic nerve. Pathologies treated via the LOA include primary orbital tumors, extraorbital tumors with local extension into the orbit, and distantly metastatic lesions to the orbit. These all often initially manifest with vision loss, oculomotor deficits, or proptosis. The expertise of a multidisciplinary team is needed to execute safe and effective treatment. Collaboration between many specialties may be required, including ophthalmology, neurosurgery, otolaryngology, plastic surgery, oncology, and anesthesiology. The modern technique involves either a lateral canthotomy or eyelid crease incision with removal of the lateral orbital wall. It affords many advantages over a pterional craniotomy, primarily a lower approach morbidity and superior cosmetic outcomes. Reconstruction is fairly simple and the rate of complications-vision loss and extraocular muscle palsy-are low and infrequently permanent. Deep orbital apex location and intracranial extension have traditionally been considered limitations of this approach. However, with increased surgeon comfort, modern technique, and the adoption of endoscopy, these limits have expanded to even include primarily intracranial pathologies. This review details the LOA, including the general technique, its indications and limitations, reconstruction considerations, complications, and recent data from case series. The focus is on microscopic access to intraorbital lesions.

Tissue repair in neonatal and paediatric surgery: Analysis of infection in surgical implantation of synthetic resorbable biomaterials

BACKGROUND

There has been increased interest in the use of biomaterials that resorb completely leaving only the patient's native tissue. Synthetic materials are advantageous for tissue repair because they are highly customisable. The infection rate of using resorbable natural materials in paediatric surgery has recently been outlined, but there has not yet been a review of the use of synthetic resorbable materials in paediatric surgery.

OBJECTIVES

This systematic review analyses the risk of infection after implantation of fully resorbable synthetic biomaterials in paediatric cases.

METHODS

The literature was searched from January 1970 to January 2018 (inclusive), specifically searching for paediatric cases (0-18 years old), use of synthetic resorbable materials and infection.

RESULTS

The infection rate in 3573 cases of synthetic resorbable material implantation was 1.1% (41 cases). A Chi-squared test for independence found infection rate to vary among materials. Of the many biomaterials identified in this review, the highest infection rates were seen in Suprathel's use in burns injuries (12.1%).

CONCLUSIONS

This review found a low infection rate in synthetic resorbable materials used in paediatric surgery, with particularly strong evidence for low infection risk in LactoSorb® use.