Distraction Osteogenesis for Ridge Augmentation: Prevention and Treatment of Complications. 30 case reports

“Distraction Osteogenesis for Ridge Augmentation: Prevention and Treatment of Complications. 30 case reports”

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Distraction Osteogenesis for Ridge Augmentation: Prevention and Treatment of Complications. Thirty Case Reports

Stuart J. Froum, DDS 1, Edwin S. Rosenberg, BDS, H Dip Dent, DMD 2, Nicolas Elian, DDS 3, Dennis Tarnow, DDS4, Sang Choon Cho, DDS 5

Distraction osteogenesis (DO) is the latest addition to the variety of alveolar ridge augmentation procedures used to increase the volume of bone prior to implant placement Thirty DO procedures were performed in 30 patients using 17 intraosseous and 13 extraosseous devices to augment deficient alveolar ridges. Fifty-five implants placed in the distracted bone were followed for a period of 34 to 60 months after loading. Five implants failed, for a 90.9% success rate. Vertical augmentation ranged from 3.5 to 13.0 mm {average, 7.8 mm). At least one com­plication was encountered, requiring additional hard or soft tissue surgery, in each of the 30 repotted cases. This paper reviews complications encountered in the DO-treated patients, suggesting solutions and measures to prevent these prob­lems. (Int J Periodontics Restorative Dent 200S;2S:337-345.)

1 Clinical Professor, Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York
2 Professor, Department of Periodontology, University of Pennsylvania Dental Center, Philadelphia, Pennsylvania.

3 Assistant Professor and Director, Department of Periodontology and Implant Dentistry New York University College of Dentistry, New York, New York
4 Professor and Chair, Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York.
5 Assistant Clinical Professor, Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York.
Various ridge augmentation procedures have been documented as pre­dictable means of establishing new vital bone for implant placement.1-4 A variety of procedures, including guided bone regeneration (GBR) (with and without the addition of particulate bone), autogenous block grafts from the ramus or symphysis, and allograft blocks, have been used to increase bone volume prior to implant placement.5-7 The latest addition to the various ridge augmentation tech­niques is distraction osteogenesis (DO). DO is defined as a surgical process that involves the gradual, con­trolled displacement of a surgical frac­ture that results in simultaneous enlargement of the volume of bone and soft tissue.
The use of DO for long bone defects (to increase the length of the femur) dates back to the work of Codivilla.8 Ilizarov, a Russian orthopedic surgeon, and coworkers described the biologic basis for healing with a sur­gical distraction device9, and a number of successful case reports were subsequently presented in the orthopedic lit­erature10. In 1973, Snyder et al11 used a surgical device for the osseous distraction of a dog mandible, and since then several authors have used the technique in other mandibular animal models. 12,13 Ilizarov suggested the use of DO to correct maxillofacial deformities,14 and DO was later used by Karp et al in oral surgery.15  Nishimura et al reported the use of DO for ridge augmentation16, while McCarthy et al17 reported on four cases of unilateral mandibular hypoplasia that were treated using a miniatur­ized Hoffman device Different DO devices for treating alveolar ridge deformities in animal and human stud­ies were subsequently described by other authors.18-32
For the last decade, DO has been used intraorally to create bone for implant placement In 1996, Block et aI22 and Chin and Toth23 reported on the use of DO for site development prior to implant placement. Implants have been placed in this new bone with short-term and tong-term success rates that are similar to those seen for implants placed in ridges augmented with GBR procedures.3,4 In fact, one study concluded that “the overriding question of whether or not alveolar distraction osteogenesis can provide better results than conventional augmentation techniques was judged affir­matively, through the risk of the surgi­cal procedure may possibly be somewhat greater than conventional grafting procedures “.33That study reported that the 5-year clinical success of implants placed in bone augmented by DO was 90 4%. Another study elab­orated on three areas of minor com­plications arising during seven mandibular distraction procedures.34 These included intraoperative complications (ie, fracture of the transport segment), complications during dis­traction (ie, incorrect direction of dis­traction), and postdistraction compli­cations (le, bone formation defects)
A published review of the DO pro­cedure described different types of intraosseous and extraosseous devices and a combination device.35 This review also discussed several potential complications with the various devices. The purpose of the present article is to document the success rate and problems relative to 30 DO procedures per­formed using intraosseous or extraosseous devices and to discuss the occurrence prevention and treat­ment of these potential complications.
Method and Materials

Since 1999 at New York University Dental Center Department of Periodontology and Implant Dentistry and in the private practices of the authors, 30 patients have been treated with 30 DO procedures using 17 intraosseous devices (IDs) (Lead Stryker, Leibinger) and 13 extraosseous devices (EDs) (Track Plus System, KLS Martin) to augment deficient alveolar ridges prior to implant placement (Figs 1a to 1f). Procedures followed stan­dard distraction techniques35,36, albeit with several modifications, when these deuces were used for distraction of the transport segments Distraction of the segments was performed at a rate of 0.4 to 1.2 mm per day A 0.4-mm or 0.6-mm distraction rate was used for the first 3 days, followed by a rate of 1.2 mm per day in all cases treated. The consolidation time (healing time with the device in situ, with no move­ment following active distraction) prior to device removal and implant place­ment was 9 to 12 weeks in all cases.
In three patients using the ID and in 13 patients using the ED, two mod­ifications designed by one of the authors were made to the standard distractor appliance. Metal wedges were placed and attached with absorbable sutures, lingual to the transport and base plates, to change the buccaI vector of the distractor (Fig 2). An additional modification included the use of a horizontal dis­tractor appliance devised by the same author that employed a palatal expan­sion device37(Fig 3). This device was worn as a guide and to prevent lingual relapse. It was activated every other day during the vertical distraction (which was activated 0.4 mm on alternate days) This appliance allowed for improved buccaI vectors while avoid­ing the application of lateral forces to the central distractor screw.
To determine the amount of ver­tical augmentation achieved with the ED, measurements were made from one screw hole in the transport plate to a corresponding screw hole in the base plate (Fig 1c). This distance was calculated at the time of distractor placement and again at the time of removal. The vertical aug­mentation was calculated by subtract­ing the distance at the time of distrac­tor removal from the measurement at time of distractor placement. In patients in whom the ID was used, measurements from the screw hole in the base plate to the screw hole in the transport plate were calculated at the time of distractor placement and subtracted from the same measurements obtained at the time of distractor removal.
Fig 1a Preoperative view of a ridge defect with a malposed implant in the mandibular incisor area
Fig 1b Axial computerized tomographic scans of the malposed and unrestorable implant
Fig 1c Extraosseous distractor with transport plate secured to the mobile segment, with screw hole 5 mm apart
Fig 1d Distractor at the time of removal
Fig 1e New bone formed following distraction. The screw holes are now 16mm apart, documenting 11mm of vertical augmentation
Fig 1f Final four-unit restoration following DO, removal of malposed implant, and placement of two implants in the lateral incisor areas
Fig 2 Extraosseous distractor with metal wedges attached to distraction microplates to change the guidance vector
Fig 3 Placement of a horizontal distractor appliance designed by one of the authors to move the segment buccally following vertical distraction. Distraction is performed at a rate of 0.25mm per day
Fifty-five implants were placed in the distracted ridges and followed for a period of 34 to 60 months after load­ing. Of these, seven had machined surfaces and 48 were rough-surfaced implants. The implants were manufactured by four different companies (Endopore Innova, ITI Straumann, Nobel Biocare, and Implant Innovations). Any and all complications were documented and recorded. Implant success was defined following the criteria described by Albrektsson et al. 37 Failure was defined as any implant the did not follow these criteria, usually showing mobility at the time of removal.
Results:
Five of the 55 implants that were placed failed, for a 90.9% success rate. Vertical augmentation in the 30 patients ranged from 3.5 to 13.0mm (average 7.8mm). Implant failures in the present study correlated closely with resorption of the transport segment of the distracted bone. Four of the five implant failures occurred in sites where the transport bone underwent moderate to severe resorption. The other implant failure occurred as a result of infection at the surgical site. Of the five failed implants, two had smooth surfaces and three had rough surfaces.
Complications encountered in the 30 DO procedures are listed in Table 1 in order of frequency of occurrence and were classified into eight categories. The need for additional surgery occurred in all 30 patients, and soft tissue grafts were required to reestablish an adequate vestibule or provide necessary keratinized tissue prior to implant placement. additional hard tissue augmentation using GBR or block grafts was required in 18 of the 30 patients. Failure to achieve the desired buccal augmentation occurred in 22 of 30 cases. This was caused by segment guidance problems related to the buccal vector of movement. In 8 of 30 cases, a less-than-ideal esthetic result was reported. Other complications occurred to a minor degree.
Discussion
Success rates of implants placed in distracted bone may be somewhat lower than those of implants placed in bone augmented via GBR. However, comparisons of implant survival rates between reports that used different ridge augmentation procedures should be made with caution because of the many variables involved. Buser et al reported a 5-year success rate of 98.3% of 66 implants placed in bone that had been previously augmented with autografts and nonresorbable barrier membranes. 4 A literature review in the same article documented survival rates that ranged from 92.6% to 100% with implants placed in ridges augmented with membrane barriers combined with allografts, xenografts, or autografts. Two separate studies of implant placed in ridges augmented with autogenous block grafts reported implant success rates of 98.3% 38 (following for 0 to 77 months) and 81.28% 39 (followed for 3 years).
Although short-term data of implants placed in distracted bone reported no failures, 40 a prospective study reported a 90.4% success rate after 5 years of follow-up.33 The results of the present investigation docu­mented a similar implant success rate (90.9%).
DO has proven to be a predictable method for vertical ridge augmenta­tion. 24-27, 30, 33, 35, 40 Two recent prospec­tive studies documented average ver­tical gains following DO of 6.5 mm (range, 3 to 15 mm)33 and 7 mm (range, 5 to 9 mm)40. A case report used DO to treat an atrophied alveolar ridge in the anterior mandible of a 30-year-old woman and reported that “a vertical augmentation of 7 mm had been achieved”7.  Our results were similar to those of other authors, in that we achieved an average of 7.8 mm of ver­tical augmentation, with a range of 3.5 to 13.0 mm. These measurements should be viewed in light of the poten­tial for the DO technique to achieve vertical augmentation. For example, some patents required only 4 to 5 mm of augmentation. Therefore, when this amount of augmentation was achieved, the movement was ended. However, the greater potential of DO to achieve vertical augmentation is sig­nificant compared to ridge augmenta­tion procedures using GBR, which seem to be limited to approximately 4 mm of vertical augmentation.41
Guidance problems

One of the complications observed in the present study was the limited buccal augmentation achieved by DO because of an inadequate buccal vec­tor. One study33 reported an average of < 2 mm of horizontal augmentation following DO in 30 patients. That study reported a range of 10 mm of buccal positioning to 4 mm of lingual posi­tioning in horizontal augmentation procedures. In the same study, 11 seg­ments moved palatally and 5 seg­ments healed in a neutral position. Thus, additional surgery (bone grafting or soft tissue augmentation) was nec­essary in the 30 patients reported. We have presented a possible solution for this vector problem in a horizontal distractor that can aid in the attainment of the desired buccal augmentation. Care must be taken when using two differ­ent vectors not to move the segment too rapidly, which may result in nonunion. More documentation is nec­essary to determine the ideal rate and timing of the use of two vector distractions.
In the final eight patents treated in the present study, the buccal aug­mentation was significantly improved over the previous 22 cases. Each of these cases used metal buccal wedges to change the distraction vector and a horizontal distractor in conjunction with the vertical augmentation to achieve satisfactory buccal movement of the transport segment Moreover; the con­cept of “overdistraction” was employed in an attempt to solve the problem recently identified with two adjacent implants in the esthetic zone. These papers documented a deficiency of the interimplant papil­lae caused by the limitation of soft tis­sue height (average 3.4 mm) coronal to the intercrestal bone between Iwo adjacent implants. Overdistraction of the tissue in this area may compensate for the soft tissue limitation and improve the esthetic result.
Soft tissue complications (diminished vestibule)

A diminished vestibule is often encountered as a result of the initial incision in the alveolar mucosa and the advancement of the flap to obtain complete flap coverage over the dis­traction apparatus. This problem occurred in all 13 patients with the ED and in five patients with the ID. In the patients who used the ID, the initial vertical gap of approximately 4 mm caused by the interposition of the base and transport plates requires advance­ment of the flap to gain primary clo­sure. In patents with the ED, a dimin­ished vestibule is even more common, since there is a greater bulk of mater­ial to cover with the flap. This problem can be treated with a connective tissue graft placed at The time of or shortly after removal of the distract on appa­ratus (Fig 4).
Soft tissue complications (flap dehiscence)

Flap dehiscence at the distractor plates occurred in four patients with ED. These dehiscence defects appeared at 2, 4, 4, and 8 weeks following active distraction (Fig 5). The patients were instructed to clean the exposed plates with a cotton swab saturated with 0.12% chlorhexidine three times per day and use warm saline rinses three or four times a day until the distraction devices were removed. There were no cases of infection or instances where the distraction device had to be removed earlier than planned. In one patient, a bony dehiscence was noted during distraction with the ID (Fig 6). The etiology of this was related to the fact that irregular and sharp bony edges are often created when the ver­tical cuts are made during the osteotomy. Because during the stan­dard DO procedure, tissue is reflected up to but not over the alveolar crest, these sharp edges often remain unde­tected until they become visible through the crestal tissue. Treatment of this complication involves immediate osteoplasty of the exposed bony seg­ment. Prevention is accomplished by performing this osteoplasty during surgery to place the distractor, follow­ing the vertical osteotomy cuts. The steeper the angle of the vertical defect, the greater the likelihood that this problem will occur.
Fig 4 A connective tissue graft of palatal mucosa is placed on the buccal aspect of the augmented ridge to reestablish the vestibule following removal of the distractor.
Fig 5 Soft tissue dehiscence occurred with an ED at 4 weeks after initiation of distraction

Compromised Esthetic Results

One of the major indications of the DO procedure is to reconstruct hard and soft tissue in the anterior areas of the maxilla and mandible to enable fabrication of an esthetic implant-supported fixed restoration. Unfortunately, this is often difficult to accomplish. In fact, Jensen et al33, in discussing the esthetics of restorations placed following DO, reported that none of his 30 distracted cases showed superlative esthetic results with implant-supported restorations. In the present study, following the additional hard or soft tissue surgery that was necessary in all 30 DO cases to improve augmentation and esthetics, only 8 of 30 patients treated felt that the esthetic results were unacceptable. Since all DO-treated cases required additional surgery, the clinician using this modality should be familiar with auxiliary methods of ridge augmenta­tion, including soft and hard tissue grafts and GBR, to achieve the excel­lent esthetic results that have until now been rare with DO procedures alone.
Temporization difficulties

Temporization during DO requires acceptable esthetics, easy access (for the operator) to the distraction screw, and prevention of occlusal forces on the transport segment. Whenever pos­sible the patient is asked to function without a provisional appliance for 10 to 14 days post surgery. In some cases this is not possible. The provisional appliance of choice uses orthodontic brackets and an archwire to which the pontics are attached coronal to the segment being distracted. During the consolidation period, an acrylic resin-bonded splint may be fabricated. Intraosseous DO devices require that a hole be made in the splint to allow positioning of the splint over the dis­traction screws (Fig 7).

Fig 6 Clinical view of bony spicule caused by the sharp bony edge following vertical osteotomy
Fig 7 Removable provisional appliance with provision made for access for the distractor rod of the ID
Distractor instability

Instability of the distraction device was a problem in 2 of the 30 cases per­formed. Both of these occurred with the intraosseous systems. This did not, however, compromise the success of the four implants placed in the dis­tracted bone. In all other cases, the transport and base plates were well fixated with 10-to 12-mm-long screws. In patients who received EDs, the base plate with the added vertical straight chain “tailpiece” increased stability of the distractor screw, thus preventing this problem
Infection

Infection occurred in 2 of the 30 dis­traction procedures. Both of these complications occurred in patients with IDs. In these two cases of infection, partial resorption of the transport segment took place. Chlorhexidine 0.12% rinses and systemic antibiotic coverage resulted in resolution of the infection in both cases. Prevention of infection was accomplished by premedicating all patients with 2 g amoxicillin (or 600 mg clindamycin for those with penicillin allergy) 1 hour prior to surgery and continuing with 500 mg of amoxicillin three times daily or 300 mg of clin­damycin four times daily for 10 to 14 days postsurgery. All patients were pre­scribed a 0.12% chlorhexidine gluconate mouth wash to use twice a day on the day prior to surgery, immedi­ately before the procedure, and con­tinuing twice a day beginning 24 hours following surgery for 1 month post-surgery.
Resorption of transport segment

Resorption of the transport segment can be minimized by keeping the crestal and lingual soft tissues intact dur­ing both the osteotomy procedure and the distraction period. These tissues stabilize the transport segment and provide vascular supply to the healing tissue. In the present study complete resorption of the distracted bone occurred in one patient. Partial resorp­tion occurred in eight patients. All but one of these patients used the ID. In the ID patient, complete resorption occurred following successful vertical distraction when an attempt was made to move the transport segment buccally with orthodontic elastics attached to the central distractor screw. The dis­tractor moved buccally, but the seg­ment resorbed. This was the result of the application of buccal forces to the distractor screw, which was not inte­grated with the transport plate (Fig 8). In all subsequent cases, no additional force was applied to the distractor other than that indicated for a vertical activation of 1.2 mm per day. Researchers have noted that the mag­nitude of distraction is more important than the frequency of distraction in producing an improved regenerative result in the other 21 patients, the transport segment remained vital, did not resorb, and was moved vertically with success.
Fig 8 Resorption of a transport segment caused by horizontal forces that were placed on the distractor rod in an attempt to move the segment buccally

Conclusions

Distraction osteogenesis is a pre­dictable method of treating alveolar ridge deformities prior to implant placement. In this study, significant ver­tical augmentation was achieved. However, the clinician must be aware of the limitations and potential com­plications of this procedure. The solu­tions suggested in this paper to pre­vent these problems may make this modality more acceptable to a larger percentage of surgeons performing ridge augmentation procedures. Moreover, the clinician should be famil­iar with other methods of augmenta­tion (guided bone regeneration, block grafts, soft tissue grafts), which are usu­ally necessary in conjunction with dis­traction osteogenesis augmentation to achieve the desired functional and esthetic results.
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