Keywords
Absorbable implants - Foreign body reaction - Maxillofacial injury
INTRODUCTION
Metallic plates and screws are commonly used for rigid internal fixation during maxillofacial
surgery [[1]]. However, metallic implants have problems, such as visibility on radiography, palpability,
bone erosion and growth restrictions, thermal sensitivity, and the need for removal
[[2]
[3]]. Various bioabsorbable materials have been developed to overcome these disadvantages
of metallic implants [[4]]. Ideally, bioabsorbable plates are sufficiently rigid and biocompatible, provide
sufficient stability to allow bone healing, and are eliminated completely after osteosynthesis
without a foreign body reaction [[5]
[6]]. They do not require any secondary operation for removal due to their characteristics.
Thus, bioabsorbable plates and screws are commonly used to reduce maxillofacial bones,
particularly in pediatric patients [[7]]. Polyglycolic acid (PGA) and polylactic acid (PLA) are the polymers used most widely
to manufacture bioabsorbable plates and screws [[5]
[8]]. Plate degradation properties and rates vary depending on the ratio of lactic acid
isomers or glycolic acid. If the bioabsorbable plates fail to degrade completely or
undergo polymeric breakdown beyond the maximum metabolic clearance rate, the remnant
material can become a nidus for an inflammatory foreign body reaction [[8]
[9]
[10]]. Copolymers such as polylactic-co-glycolic acid are often used commercially because
these complications are almost always associated with homopolymers [[8]
[10]
[11]]. Many studies have reported the efficacy and clinical utility of bioabsorbable
plates, but few reports are available on complications associated with the plates,
resulting from inadequate degradation of the plates [[12]
[13]]. Between March 2005 and October 2013, we encountered eight cases of a delayed foreign
body reaction after surgical fixation with bioabsorbable plates and screws. We report
these cases with a review of the literature.
METHODS
The medical records of 372 patients who underwent surgical treatment with metal plates
(n=138), bioabsorbable plates (n=176), or both (n=58) for a maxillofacial fracture
between March 2006 and October 2013 were reviewed retrospectively. The data included
fracture patterns, fixation methods/materials, and any complications. A total of 234
patients who were treated using bioabsorbable plates (186 men and 48 women; age, 15-84
years; mean age, 35.2 years) were included in our study. They were diagnosed with
a zygomaticomaxillary complex fracture (n=146), maxilla fracture (n=57), nasoethmoid
orbital fracture (n=20), or a LeFort fracture (n=11). Rigid fixation was achieved
with the Inion CPS (Inion, Tampere, Finland) plating system in 173 patients and Rapidsorb
(Synthes, West Chester, PA, USA) in 61 patients ([Table 1]). Metal plates were used with bioabsorbable plates in 58 of 234 patients. Patients
were selected to receive bioabsorbable fixation on the basis of the degree of bony
displacement, fracture pattern or location, and patient age. Patients with an isolated,
noncomminuted, minimally displaced fracture were good candidates for bioabsorbable
fixation. However, biodegradable plates were regarded as the most appropriate in young
patients irrespective of the fracture type. All fractures were approached in the standard
fashion, and most patients were stabilized with a two- or three-point fixation at
the frontozygomatic suture (2.0-mm plate and 7-mm screws), infraorbital rim (1.5-mm
plate and 6-mm screws), and anterior wall of the maxilla (1.5-mm mesh plate and 4-mm
screws).
Table 1
Patient demographics
|
Characteristic
|
Number (%)
|
|
ZMC, zygomaticomaxillary complex; NEO, nasoethmoid orbital.
|
|
Total
|
234
|
|
Male
|
186 (79.5)
|
|
Female
|
48 (20.5)
|
|
Age/Range (yr)
|
35.2/15-84
|
|
Diagnosis
|
|
|
ZMC fracture
|
146 (62.4)
|
|
Maxilla fracture
|
57 (24.4)
|
|
NEO fracture
|
20 (8.5)
|
|
LeFort fracture
|
11 (4.7)
|
|
Material
|
|
|
Inion CPS
|
173 (73.9)
|
|
Rapidsorb
|
61 (26.1)
|
|
Complications
|
|
|
Palpable, fixed mass
|
6 (2.5)
|
|
Focal swelling
|
2 (0.9)
|
|
Total
|
8 (3.4)
|
In the statistical evaluation, a logistic regression analysis was used (level of significance,
P<0.05). Odds ratios were calculated, and 95% confidence intervals were constructed
where appropriate.
RESULTS
A total of 234 patients achieved satisfactory bone healing with favorable restoration
in form and function and no signs of inflammation, such as a heating sensation or
tenderness, during the early postoperative period. Complications occurred in eight
(3.4%) of the 234 patients, including palpable, fixed masses in six patients and focal
swelling in two patients ([Table 1]). Six patients were diagnosed with a zygomaticomaxillary complex fracture, and two
were diagnosed with a nasoethmoid orbital fracture. Six of them were fixed with Inion
CPS plates, and two were fixed with Rapidsorb plates. The period from surgical fixation
to the onset of symptoms was 9-23 months. We were determined to perform the operations
when the masses formed. Two patients with focal swelling were under observation without
surgery for a mean duration of 13 months after fixation. Six patients with a mass
underwent secondary surgery for the exploration and removal of the mass at a mean
duration of 17.7 months after fixation. The masses developed in the bioabsorbable
fixation sites, including the frontozygomatic suture (n=3), the infraorbital rim (n=2),
or both (n=1) ([Table 2]). A surgical skin incision was made along the previous scar. The masses contained
fibrous tissue with a yellow, grainy, and cloudy fluid and remnants of incomplete
degraded bioabsorbable plates and screws. A connective tissue capsule was seen around
the foreign material and was composed of thin collagen fibers with numerous fibroblasts
and fibrocytes. Multinucleate giant cells, lymphocytes, and histiocytes were evident.
The masses were diagnosed as a foreign body reaction. The tissue culture results were
negative in all patients, and the masses did not recur during a 1-year follow-up after
recovery. There was no difference in gender and material type causing the foreign
body reaction between the patients with and those without a foreign body reaction
([Table 3]).
Table 2
Characteristics of the patients with complications
|
Patient no.
|
Sex/Age (yr)
|
Diagnosis
|
Fixation plates (size, mm)
|
Onset of symptom after surgery (mo)
|
Symptom
|
Location
|
Treatment
|
Histologic examination
|
|
ZMC Fx, zygomaticomaxillary complex fracture; NEO Fx, nasoethmoid orbital fracture.
|
|
1
|
M/36
|
ZMC Fx
|
Rapidsorb (2.0)
|
23
|
Palpable, fixed mass
|
Frontozygomatic suture
|
Operation
|
Foreign body granuloma
|
|
2
|
M/28
|
ZMC Fx
|
Inion CPS (2.0)
|
17
|
Palpable, fixed mass
|
Frontozygomatic suture
|
Operation
|
Foreign body reaction with fibrosis
|
|
3
|
M/28
|
ZMC Fx
|
Inion CPS (2.0)
|
15
|
Palpable, fixed mass
|
Frontozygomatic suture
|
Operation
|
Foreign body reaction with fibrosis
|
|
4
|
M/56
|
ZMC Fx
|
Inion CPS (2.0)
Inion CPS (1.5)
|
21
|
Palpable, fixed mass
|
Frontozygomatic suture Infraorbital rim
|
Operation
|
Foreign body reaction with fibrosis
|
|
5
|
M/40
|
NEO Fx
|
Inion CPS (1.5)
|
10
|
Palpable, fixed mass
|
Infraorbital rim
|
Operation
|
Foreign body reaction with fibrosis
|
|
6
|
M/49
|
NEO Fx
|
Inion CPS (1.5)
|
18
|
Palpable, fixed mass
|
Infraorbital rim
|
Operation
|
Foreign body reaction with fibrosis
|
|
7
|
M/21
|
ZMC Fx
|
Inion CPS (2.0)
|
17
|
Focal swelling
|
Frontozygomatic suture
|
Observation
|
No
|
|
8
|
F/58
|
ZMC Fx
|
Rapidsorb (2.0)
|
9
|
Focal swelling
|
Frontozygomatic suture
|
Observation
|
No
|
Table 3
Odds ratio of patients with and those without a foreign body reaction
|
Characteristic
|
Patients with a foreign body reaction (n = 8)
|
Patients without a foreign body reaction (n = 226)
|
Odds ratio
|
P-value
|
|
a)P<0.05, significant difference; P>0.05, no significant difference.
|
|
Gender
|
|
|
|
0.57a)
|
|
Male
|
7
|
179
|
1.84
|
|
Female
|
1
|
47
|
0.54
|
|
Material
|
|
|
|
0.94a)
|
|
Inion CPS
|
6
|
167
|
1.06
|
|
Rapidsorb
|
2
|
59
|
0.94
|
Case 1 (patient no. 1)
A 36-year-old man visited our clinic to treat a mass on the left frontozygomatic suture.
He had fallen 29 months earlier, under alcohol intoxication. The patient had a left
zygomaticomaxillary complex fracture, which was fixed with a Rapidsorb 2.0-mm 4-hole
plate on the frontozygomatic suture, a 1.5-mm 8-hole plate on the infraorbital rim,
and a bioabsorbable mesh plate on the anterior wall of the maxilla. He suffered from
a palpable, fixed mass measuring 1 cm×2 cm for 6 months ([Fig. 1A]). A computed tomography (CT) scan 23 months after surgery showed soft tissue thickening
on the left frontozygomatic suture ([Fig. 1B]). The patient had secondary surgery for the exploration and removal of the mass.
The resected mass contained chronic inflammatory tissue with a grainy, cloudy liquid,
and no gross evidence of a plate or screws inside the mass ([Fig. 1C, D]). However, the histological findings of the mass revealed the fine fragments of
a foreign body with inflammatory cell infiltration, which was diagnosed as a foreign
body granuloma ([Fig. 1E]).
Fig. 1 Case 1 (patient no. 1)
(A) Preoperative clinical view 29 months after Rapidsorb plate fixation. (B) Computed
tomography scan shows soft tissue thickening on the left frontozygomatic suture (red
circle). (C) Fibrous encapsulated mass. (D) Resected mass containing inflammatory
tissue with a yellow, cloudy liquid. (E) Fine foreign body fragments, multinucleated
giant cells, lymphocytes, and histiocytes are seen (H&E, ×100).
Case 2 (patient no. 2)
A 28-year-old man was struck on the right side of the face while snowboarding. The
patient had a right zygomaticomaxillary complex fracture, which was fixed with the
Inion CPS 2.0-mm 4-hole bioabsorbable plate on the frontozygomatic suture, a 1.5-mm
C-shaped 7-hole plate on the infraorbital rim, and a bioabsorbable mesh plate on the
anterior wall of the maxilla. The patient visited our outpatient clinic 17 months
later complaining of a palpable mass, measuring 3 cm×2 cm, on the left frontozygomatic
suture ([Fig. 2A]). The mass was a painless, visible, fixed mass. A CT scan showed a high-density
content mass on the right frontozygomatic suture ([Fig. 2B]). The patient underwent secondary surgery for the exploration and removal of the
mass. The bioabsorbable plate and screws had been replaced by a fibrous capsule, which
contained a yellow, cloudy fluid and the remnants of the incompletely degraded bioabsorbable
plate and screws ([Fig. 2C]). The histological findings of the mass showed a foreign body reaction with fibrosis
([Fig. 2D]).
Fig. 2 Case 2 (patient no. 2)
(A) Preoperative clinical view 17 months after Inion CPS plate fixation. (B) Computed
tomography scan showing high-density content with soft tissue thickening on the right
frontozygomatic suture (red circle). (C) Resected mass containing a yellow, cloudy
fluid and the remnants of an incompletely degraded bioabsorbable plate and screws.
(D) Foreign body material with multinucleated giant cells, fibroblasts, lymphocytes,
and histiocytes (H&E, ×100).
Case 3 (patient no. 4)
A 56-year-old man visited our clinic to receive treatment for a mass on the right
frontozygomatic suture and infraorbital rim ([Fig. 3A]). He had fallen while driving a concrete mixer truck 25 months earlier. The patient
had a right zygomaticomaxillary complex fracture, which was fixed with the Inion CPS
2.0-mm 4-hole plate on the frontozygomatic suture and the 1.5-mm 6-hole plate on the
infraorbital rim. He suffered from two palpable, fixed masses, measuring 2.5 cm×1
cm each, for 4 months. A CT scan showed soft tissue thickening on the right frontozygomatic
suture and infraorbital rim ([Fig. 3B, C]). The patient underwent secondary surgery for the exploration and removal of the
mass. The mass contained fibrous tissue with a yellow, cloudy fluid and the remnants
of the incompletely degraded bioabsorbable plate and screws ([Fig. 3D, E]). The histological findings of the mass demonstrated a foreign body reaction with
fibrosis ([Fig. 3F]).
Fig. 3 Case 3 (patient no. 4)
(A) Preoperative clinical view 25 months after Inion CPS plate fixation. (B) Computed
tomography scan shows soft tissue thickening on the right frontozygomatic suture (red
circle). (C) Soft tissue thickening on the right infraorbital rim (red circle). (D)
Resected mass containing a yellow, cloudy fluid and remnants of an incompletely degraded
bioabsorbable plate and screws on the right frontozygomatic suture. (E) Resected mass
on the right infraorbital rim. (F) Foreign body material with multinucleated giant
cells, fibroblasts, lymphocytes, and histiocytes (H&E, ×200).
DISCUSSION
Bioabsorbable plates ideally provide rigid fixation during the initial bone healing
phase and are degraded by the body after osteosynthesis. In addition, these plates
must be biocompatible with the recipient environment to prevent a significant inflammatory
foreign body reaction [[5]
[6]]. Multiple factors, such as the chemical composition, size, and shape of bioabsorbable
plates, affect the occurrence of foreign body reactions [[8]]. The results of several studies reveal that the foreign body reaction of a bioabsorbable
plate results from an inadequate degradation of the chemical components of the plate.
PGA and PLA are popular among several chemical compositions for bioabsorbable plates,
and PLA exists in two different isomeric configurations of poly-L-lactic acid (PLLA)
and poly-DL-lactic acid (PDLLA) [[5]
[8]]. PGA and PLA biodegradation occurs in a two-stage process. The first stage relies
on the hydrolysis of the polymer's chemical bonds, thereby creating a shorter-chain
molecule. The presence of these small polymer fragments can evoke a foreign body reaction.
Then, they are phagocytized by macrophages and carried to the liver for metabolism.
In the second metabolic phase, the breakdown products are metabolized to CO2 and H2O [[5]
[6]
[8]
[10]
[14]]. Secondary surgery for removal can be avoided through this process. Degradation
properties and rates differ according to the main chemical components because they
depend on the crystallinity and hydrophobicity of the polymers. PGA is a hard crystalline
polymer and is less hydrophobic, so it undergoes rapid breakdown within 1 year. In
contrast, PLA is a semicrystalline polymer and is highly hydrophobic, so it is degraded
much more slowly within 5-6 years. Therefore, PGA is typically used in conjunction
with PLA to create better strength and degradation profiles than those of either of
the homopolymers alone [[8]
[10]
[11]]. The Rapidsorb plate is manufactured from 85:15 poly (L-lactide-co-glycolide, PLGA).
This copolymer is formed by combining PLLA and PGA. These plates maintain approximately
85% of their initial strength after 8 weeks and are completely absorbed after 1 year
[[15]]. The Inion CPS plate is a copolymer of PLLA, PLDLA, and trimethylene carbonate.
These plates are absorbed slowly, retaining 70% of their initial strength at 9 weeks,
and they are completely degraded in 2-4 years [[16]].
In this study, six patients had palpable, visible masses and two patients had focal
swelling around the bioabsorbable plates and screws. No risk factors of a foreign
body reaction, namely gender and material type, could be found ([Table 3]). Most of the complications occurred in the frontozygomatic suture, which was fixed
with a large-volume, 2.0-mm-thick bioabsorbable plate and 7-mm screws. As the implant
materials have high volume and thickness, dead space may form and lead to fluid collection
and a foreign body reaction [[17]]. In addition, this complication is caused by inadequate degradation, as degradation
properties and rates are influenced by implant volume, geometrical shape, and chemical
composition [[18]]. In contrast, there was no complication in the anterior wall of the maxilla. We
think that this can be attributed to the small-volume implant, 1.5-mm mesh plate,
and 4-mm screws used for fixation; further, the small polymer fragments derived from
the first degradation process were partially absorbed into the maxillary sinus without
a foreign body reaction.
The resected masses of six patients were diagnosed as foreign body reactions with
fibrosis (n=5) and a foreign body granuloma (n=1). The patient with a foreign body
granuloma was fixed with a 2.0-mm Rapidsorb plate. No gross evidence of a plate or
screws was detected inside the granuloma, but fine foreign body fragments with inflammatory
cell infiltration were seen histologically. This finding occurred because the Rapidsorb
plate was almost absorbed 29 months after surgery. Two patients who were under observation
without surgery continue to be monitored. Their symptoms improved to some degree,
but mild focal swelling remains 6 years after surgery.
Plate degradation properties and rates change depending on the characteristics of
the bioabsorbable plates, such as chemical composition and implant volume. Inadequate
degradation can cause a delayed foreign body reaction with inflammation, thus requiring
a second exploratory operation. In addition, a palpable mass or focal swelling resulting
from a foreign body reaction can remain for years. Therefore, it is prudent to consider
delayed complications when using bioabsorbable plates, and surgeons should conduct
longer and closer follow-ups.
