Reconstruction for Mandibular Implant Failure Reconstruction for Mandibular Implant Failure

Mandibular defects may result from tumor ablations, trauma, or radiation necrosis. Significant segmental mandibular loss or hemimandibular loss may sometimes be replaced with mandibular implants by ENT surgeons/oral surgeons/head and neck sur - geons. However, this may bring about mandibular implant failure in long-term follow-up. Mandibular implant failures usually manifest as: soft tissue atrophy, mandibular implant extrusion, infection, facial nerve involvement, facial asymmetry, derangement of occlusion and mastication, orocutaneous fistula, etc. Over 30 years, the authors have treated 102 patients with mandibular implant failure. Reconstruction may involve removal of the mandibular implant and immediate replacement of the mandibular defect with a piece of vascularized bone flap, not only to compensate for bone loss but also to replace neighboring soft tissue and possible skin defects. Frequently used flaps have been vascularized iliac bone (89/102) or vascularized fibula grafts (13/102). During follow-up, iliac bone flap reconstruction has yielded more favorable results due to its ample bone bulk and adequate soft tissue coverage. Fibula flaps with osteotomies have been associated with an increasing incidence of malunion/nonunion and subsequent easy deformation.


Introduction
Mandibular defects may result from tumor ablations, trauma, or radiation necrosis. Significant segmental mandibular loss or hemimandibular loss may be replaced with mandibular implants by head and neck surgeons or oral surgeons in order to terminate surgery quickly [1]. However, mandibular implant failure may ensue on long-term follow-up.
The cause of mandibular implant failure may be related to high functional demands on mastication, speech, yawning, and singing. The force and pressures imposed on the mandible by chewing, yawning, and mouth opening make mandibular implants liable to extrusion sooner or later.
Complications of mandibular implant include infection, loosening, deformation, soft tissue wasting, extrusion, capsular contracture, and sometimes the development of a skin defect owing to infection with subsequent scar contracture ( Table 1).

Patients and methods
During the past 35 years, 102 patients with mandibular implant failures had been referred for further treatments ( Table 2) [2].
The manifestations were

Facial deformities
Significant facial deformities usually brought the patients to seek plastic surgeons.
a. Soft tissue wasting (Figure 8) b. Deviation of mandible and chin (Figure 9)

Infection
Infection ensued with or without extrusion of mandibular implant (Figure 11 Orocutaneous fistula occurred when intraoral extrusion of the implant brought saliva passing by the implant, causing infection. This was soon supervened with an orocutaneous fistula, which never healed.

Removal of implant 36
Total 32 Partial 4

Strategy of treatment
I. Removal of mandibular implant when the implant became extruded or got infected [3].
With implant retained in situ in patients without implant extrusion.
With implant removed in patients with implant extrusion.
C. Anterior mandibular defect: vascularized iliac bone D. Lateral segment defect: fibula flap [5] III. Repositioning of skin flap Banked external skin flap could be moved intraorally after the subsidence of tissue swelling.

IV. Reshaping of bony contour
After bony union, some imperfect bony contour may be reshaped [4].

VI.
For nearly hemimandibular reconstructions, overzealous removal of the reconstruction plate for further reconstruction might jeopardize the overlying facial nerve which had already been surrounded by fibrosis and might have assumed a nonanatomical path. Thereafter, surgical manipulation in this area to create space might stretch the facial nerve overlying the implant and might lead to its inadvertent injury. For this reason, the plate was either partially removed or not removed at all as long as it had not been already become extruded or infected; instead, it was overlaid with a piece of vascularized bone flap.

I.
Removal of Mandibular implant when the implant become or got in fected.

II.
Immediate reconstruction of missing mandibular segment.

IV. Reshaping of bony contour
After bony union, some imperfect bony contour may be reshaped Table 3. Summary of operation technique.

Problems of reconstruction with implant failure and removal of the implant
1. Scarring and capsule formation around the implant.

2.
Difficulty in dissecting and approaching the glenoid fossa.

3.
Lack of a clear plane to expand the pocket to accommodate a vascularized bone mimicking the ascending ramus.

4.
Possibility of facial nerve injury or traction during dissection or expansion.

5.
Placement of incision should be carefully designed since there had been soft tissue atrophy and thinning of skin (Figure 13(a) and (b)).

3.
Fascia lata sling operation to hold the mandibular body to temporal muscle and fascia.

B.
Facial asymmetry after resection of mandibular ameloblastoma and mere reconstruction with mandibular reconstruction plate (Figure 15(a) and (b)).
C. Young man, aged 25 years, suffered from soft tissue wasting 1 year after sole mandibular implant insertion and his status after subcondylar mandibular reconstruction (Figure 16(a-d)).
D. Young man, aged 28 years, suffered from soft tissue wasting and chin deviation 6 months after resection of a left side mandibular ameloblastoma and subsequent reconstruction with   (Figure 17(a)). He received mandibular reconstruction with retention of implant by onlaying a vascularized iliac bone flap on the reconstruction plate with osteosynthesis at the medial end of the mandibular section margin (Figure 17(b) and (c)).
Picture 15 years after left hemimandibular reconstruction by an onlaying vascularized iliac bone flap on the reconstruction plate. No soft tissue atrophy or wasting was noticed. Occlusion was satisfactory with symmetric facial expression (Figure 17(d)).
E. This 24-year-old lady suffered from left side facial wasting after sub-hemimandibular reconstruction with reconstruction plate only (Figure 18(a)). She received mandibular reconstruction with an onlaying vascularized iliac bone flap with retaining the titanium reconstruction plate (Figure 18(b-d)).

F.
A 66-year-old lady suffered from soft tissue wasting, deformation with impending extrusion of the implant 1 year after reconstructing a segmental symphyseal defect with a  titanium mandibular reconstruction plate (Figure 18(a-c)). Removal of anterior segment mandibular implant and reconstruction with an iliac bone flap resulted in satisfactory bone union and facial contour (Figure 18(d)).   G. This 27-year-old young man received a hemimandibular implant reconstruction after resection of an ameloblastoma. However, it was complicated with infection and extrusion and ended up with implant removal, leaving a significant facial deformity (Figure 19(a)). The lateral segment mandibular defect was reconstructed with a fibula flap imcorporating with a titanium mandicular condyle (Figure 19(b) and (c)) [5].

Ancillary procedures:
Ancillary procedures are always required to achieve satisfactory functional and aesthetic results are shown in (Table 4) and (Table 5).  A. Hemimandibular reconstruction with implant (Figure 20(a-d)).
B. Soft tissue wasting above the left mandibular implant area (Figure 21(a-c)).
C. Secondary resurfacing of the lower sulcus with a banked iliac bone skin flap with revolving door technique to facilitate denture fitting and restoration of chin profile (Figure 23(a-f)).
Keeping the mandibular implant and overlaying it with a vascularized iliac bone flap can achieve not only a good functional result ( Table 4) If extrusion of the implant has occurred, infection will supervene, and inevitably the implant should be removed totally. Reconstruction may involve removal of the mandibular implant and immdiate replacement of the mandibular defect with a piece of vascularized bone flap, not only to compensate for bone loss, but also to replace neighboring soft tissue and possible skin defect. With the night strategy, good functional outcome and satisfactory aesthetic result can always be achieved, but also a satisfactory aesthetic outcome ( Table 5). Soft tissue wasting and atrophy ceased with long-term follow-up (Figure 22(a) and (b)).
For reconstruction of anterior segment mandibular defect, vascularized iliac bone grafting associated with external banking of the skin and soft tissue, followed by turning the skin flap and soft tissue intraorally with revolving door technique, can resurface the anterior vestibule and augment the chin profile, a procedure that also facilitate fitting lower denture fitting (Figure 23(a-f)).

Discussions
Mandibular defects may result in significant facial disfigurement. When the defect is associated with inner mucosal defect and/or external skin defect, the situation become even more complicated [11]. Conventional bone grafting can only succeed in less than 5 cm segmental defect or partial thickness defect.
Mandibular implants made of different materials (titanium, vitellium, etc.) and having different brands have been used by many head and neck surgeons to reconstruct segmental mandibular defects or hemimandibular defects. However, they are fraught with miscellaneous miserable complications [12].
In this article, we have presented many kinds of failures resulting from mandibular reconstructions with implants.
Reconstructions problems associated with implant failure include: • scarring and capsule formation around the implant, • difficulty in dissecting and approaching the glenoid fossa, • lack of a clear plane to expand the pocket in order to accommodate a vascularized bone graft camouflaging the ascending ramus, resulting in • possibility of facial nerve injury or traction during dissection or expansion.
• Careful planning of the incision should be elaborated because of soft tissue atrophy and thinning of skin on top of the mandibular implant.
The choice of bone flap for reconstructions is iliac bone flap for anterior mandibular, segmental and hemimandibular reconstructions while, for lateral mandibular defect, fibular flap in preferred.

Conclusions
The fate of various reconstructive modes for major mandibular defects has been presented. Selecting the ideal modes of reconstruction for significant mandibular defects is of paramount importance if an uncomplicated outcome and excellent functional result without facial disfigurement are to be achieved.
Secondary mandibular reconstruction after implant failure may cause facial nerve injury due to scarring which result in difficulty in approaching the glenoid fossa.
When mandibular reconstruction with implant fails, extrusion and infection may ensue and necessitate removal of the implant. In this situation, soft tissue wasting, fibrosis, and contracture will supervene. The overlying facial nerve will be endangered during further reconstruction consequent upon creating additional space to accommodate a vascularized bone flap.
A fascia lata sling operation is always required in hemimandibular reconstruction in patients with the implant failures, in order to hold the reconstructed mandible to an anatomical and functional place.
The use of mandibular implants as the sole reconstruction tool for significant mandibular defects should be limited. Since patients suffering from mandibular ameloblastomas are mostly young, it is advised that vascularized bone be the ideal choice in major mandibular reconstructions.