Bioabsorbable plating in the treatment of pediatric clavicle fractures: A biomechanical and clinical analysis

Highlights

• Adolescent midshaft clavicle fractures are fixed with metal or bioabsorble plates.

• Bioabsorbable plates deform plastically, with inferior stiffness.

• Metal plates required removal (13%) but bioabsorbable plates did not.

• All bioabsorbable plated fractures healed, with risk of lost radiographic reduction.

• Bioabsorbable plating outcomes were excellent for midshaft clavicle fractures.

Abstract

Background

Classic implants for operative intervention of mid-shaft clavicle fractures in adolescents can become symptomatic, requiring removal. This study compares 1) biomechanical properties and 2) clinical outcomes in adolescents of mid-shaft clavicle fracture fixation with bioabsorbable versus metal implants.

Methods

Six synthetic clavicles with mid-shaft fractures underwent bioabsorbable plating. A testing frame applied 10 non-destructive torsion and 10 axial compression cycles, followed by cantilever bending to failure. Stiffness was calculated; maximum failure load and failure mode were recorded. Results were compared to previous data for locked metal constructs.

Retrospective review of surgically treated clavicle fractures over three years included functional and radiographic outcomes.

Findings

Bioabsorbable plates had lower torsional stiffness (P < 0.001) and maximum cantilever load (P < 0.0001) than locked metal plates. There was no significant difference in compression stiffness (P = 0.2) or cantilever bending stiffness (P = 0.4). Primary failure of metal plates was screw pull-out compared to plate bending in bioabsorbable constructs.

Seven patients with bioabsorbable implants were included. All patients with bioabsorbable constructs achieved radiographic union, but 71% lost reduction. Despite fracture angulation, all achieved normal shoulder function after one year determined by QuickDASH evaluation. None required a second surgery.

Interpretation

Bioabsorbable implants had lower torsional stiffness and cantilever failure load, but comparable compression stiffness to metal implants. Bioabsorbable implants failed via gradual bending versus the catastrophic failure seen in metal implants. The clinical review allows understanding of the sequelae of this lower failure load of bioabsorbable plates where their use allowed in fracture displacement, yet achievement of ultimate radiographic union and acceptable functional outcomes.

Introduction

The clavicle accounts for nearly half of all shoulder fractures in children, and most commonly involves the midshaft region (Postacchini et al., 2002). Treatment of midshaft fractures has traditionally been non-operative except in cases of open fracture or neurovascular compromise. This management strategy was based on findings from the initial adult literature demonstrating overall positive clinical outcomes after non-operative treatment despite persistent radiographic mal-alignment (Nordqvist et al., 1998). However, more recent studies on adult high-velocity trauma fractures suggest that non-operative management may result in poor outcomes including: radiographic shortening, patient dissatisfaction regarding the cosmetic appearance, decreased endurance with shoulder abduction, and upper extremity neurologic symptoms (Hill et al., 1997; McKee et al., 2006; Zlowodzki et al., 2005). Rate of metal plate removal after implantation has been reported to be as high as 30% to 100% in children (Mehlman et al., 2009; Zlowodzki et al., 2005). Studies for the adolescent population have yielded less consistent results, and the clinical treatment strategies remain controversial. Though non-operative fixation may not result in an appreciable difference in function of the injured compared to the non-injured side, plate fixation may decrease symptomatic nonunion rates and decrease time before return to activities (Schulz et al., 2013; Vander Have et al., 2010).

While operative fixation with metal implants has been shown to decrease the rates of non- and malunion at least in the adult population, these constructs are not without their complications. Patients may experience discomfort, paresthesias or overlying skin breakdown at the site of implant placement, especially with superior plating (Kubiak and Slongo, 2002). Dissatisfaction with the appearance of the scar can be an issue in all plate positions. Additionally, fracture through the plate, implant loosening, or deep infection can also occur (Bostman et al., 1997; Poigenfürst et al., 1992). Ultimately, whether required by symptoms or by patient preference, many implants require an additional surgery for removal after the fracture is healed. Complications do not end with implant removal, as patients can re-fracture through the previous fracture site, remnant screw tunnel, or even during the plate removal process (Kubiak and Slongo, 2002; Poigenfürst et al., 1992).

One approach to eliminate the need for implant removal after fracture fixation is the utilization of a bioabsorbable implant. Implants made with biologically absorbable materials have become more popular in orthopaedic surgery and have the advantage of reduced stress shielding (allowing gradual load transfer) and a lower incidence of removal than their metal counterparts (Ambrose and Clanton, 2004; Böstman, 1996). The field of pediatric oral maxillofacial surgery has started to adopt the utilization of bioabsorbable implants over titanium implants for facial reconstruction surgery, particularly for zygomatic arch fractures (Chandra and Zemplenyi, 2017). The reason behind this trend is that the osseous structures are superficial with minimal soft tissue coverage, there is growth potential that could warrant removal of a restrictive metal implant and any requirement of implant removal is suboptimal given the location of the surgical approach. The outcomes of absorbable implants appear to mirror the outcomes seen in children treated with metal implants (both within the failure rates and the aesthetic outcomes) (Mahmoud et al., 2016; Turvey et al., 2011).

The successful utilization of absorbable implants on the facial bones lends to the discussion regarding other potential locations for successful utilization of absorbable implants. The criteria within the realm of orthopaedic surgery includes bones that are superficial in nature, have a high rate of secondary surgery for implant removal, and that during early phases of post-operative course can be managed with activity restrictions. These three criteria maximize the consideration to not use metal implants that have otherwise been demonstrated to be historically successful, such as in the midshaft clavicle fracture. The purpose of this study was to examine the biomechanical properties of failure in a bioabsorbable implant in the fixation of a midshaft clavicle fracture in comparison with those properties of a similarly-tested metal implant from a previous reported study (Robertson et al., 2009) and to determine if the mode of failure for these implants in adolescent clavicle fractures could still retain clinical utility as determined by patient-derived and radiographic outcomes.