J Oral Maxlllofac Surg

56.935-942. 1998

Long-Term Evaluation of the Use of Coralline Hydroxyapatite

in Orthognathic Surgery David A. Cottrell, DMD, * and Larry M. Wolford, DDSf

Purpose: This prospective study was designed to evaluate the long-term clinical and radiographic results of porous block hydroxyapatite (PBHA) used as a synthetic bone graft in orthognathic surgery and craniofacial augmentation.

Patients and Materials: A total of 245 consecutive patients were treated initially. Inclusion criteria for this study included a minimum clinical and radiographic follow-up of 5 years. In addition, all patients with known implant failures were included regardless of whether they met the study criteria. There were 111 patients that met the criteria for inclusion in this study. All patients had undergone orthognathic surgery with rigid fixation and had had inlay or onlay PBHA implants placed. Ninety-six percent of the implants were placed through an intraoral approach. Long-term postoperative radiographs were visually compared with immediate postoperative radiographs for implant position, stability, resorption, and other significant radiographic changes. The clinical examination evaluated for signs and symptoms of infection, wound dehiscence, implant exposure, implant displacement, changes in the overlying mucosa, and development of oronasal or oroantral fistulae.

Results: Four hundred seventy-one implants were placed: 403 in the maxilla, 44 in the mandible, and 24 in the periorbital region. There were 289 implants placed in direct communication with the maxillary sinus. The average follow-up time was 7.2 years (range, 5.0 to 10.3 years). Twenty-three implants (4.9%) were removed during the evaluation period. Lateral maxillary wall grafting had 95.7% success, with nine implants being lost in three patients. One chin implant was removed because of dissatisfaction with the aesthetics. Seven (14%) midpalatal implants used for maxillary expansion were lost, primarily because of exposure of the implant to the oral or nasal cavity at the time of surgery. When PBHA was used for alveolar cleft grafting, there was a 100% failure rate.

Conclusion: The use of PBHA as a bone graft substitute in orthognathic surgery and for facial augmentation showed a high percentage of success and efficacy. However, adequate soft tissue coverage in the nasal floor and on the palate are paramount for success of midpalatal implants. PBHA should not be used for alveolar cleft grafting. Rigid Iixation for inlay implants in the maxilla is important to provide stress shielding of the material and minimize micromovement during the initial healing phase.

Orthognathic surgery frequently requires movements of the maxilla, mandible, and midface region that creates gaps between the proximal and distal bony segments. These bone gaps can be small or quite large, as seen in cases of maxillary hypoplasia, midface

*Assistant Professor of Oral and Maxillofacial Surgery, Director of

Resident Research, Boston University School of Graduate Dentistry,

Boston, MA. Former Fellow in Oral and Maxillofacial Surgery, Baylor

College of Dentistry and Baylor University Medical Center, Dallas, TX.

tClinica1 Professor of Oral and Maxilfofacial Surgery, Texas A & M

University System-Baylor College of Dentistry; Private Practice,

Baylor University Medical Center, Dallas, TX.

Address correspondence and reprint requests to Dr Wolford:

3409 Worth St, Suite 400, DalIas, TX 75246.

B 1998 American Association of Oral and Moxillofaciol Surgeons

0278.2391/98/5608-0006$3.00/O

hypoplasia, and counterclockwise rotations of the maxillomandibular complex. Various interpositional grafting materials have been advocated to maintain the repositioned segments. Autogenous bone grafts from the calvarium, iliac crest, or ribs; freeze-dried bone; and the solid block form of hydroxyapatite have all been used as interpositional materials.‘-* Each of these materials has inherent drawbacks to its use. Autologous bone not only requires a second surgical harvest site with its inherent morbidity, but it also may undergo resorption and remodeling during healing, which has been associated with significant relapse. Freeze-dried bone undergoes significantly greater re- sorption and remodeling than autologous bone, takes longer to heal, and also carries the problems of a homograft. Solid-block hydroxyapatite does not allow bony ingrowth, is very di&ult to shape, does not become intimately incorporated into the bony matrix,

935

936 LONG-TERM EVALUATION OF HA IN ORTHOGNATHIC SURGERY

and requires autologous bone grafting to provide bony continuity and stability.

Coralline porous block hydroxyapatite (PBHA) (Interpore International, Irvine, CA) has been used as a bone graft substitute in orthognathic surgery for more than 12 years by the senior author (L.W.). It is FDA approved for use in orthognathic surgery and for craniofacial augmentation as an onlay graft. Because of its special porous nature, it is osteoconductive and allows intimate bony ingrowth. The pore size of coralline PBHA is not only similar to the normal osteon size of bone (190 pm), but it also conforms to research that confirmed the necessity of a minimum pore size of 100 urn, and preferably 150 to 200 urn for optimal bone ingrowth.5,6 Holmes et al7 reported on a histo- logic evaluation of 17 human biopsy specimens of PBHA implants used in orthognathic surgery and showed an average composition of 48.5% hydroxyapa- tite matrix, 18% bone, and 33.5% soft tissue or vascular space in healed coralline PBHA implants harvested 4.7 to 16.4 months postsurgery. In these same biopsy specimens, the composition of the adja- cent normal maxillary and mandibular bone averaged 66.5% bone and 33.5% soft tissue and vascular space, respectively. The study also showed that bone growth through the PBHA graft was essentially complete by 4 months, with further progression of the healing pro- cess resulting in maturation of the ingrown bone. Nunes et al8 reported on the histometrics of PBHA implants harvested from nine patients. Biopsy speci- mens of implants were harvested postsurgery be- tween 14 and 30 months (mean, 19.1 months). On average, the samples were composed of 17% bone, 21% void (soft tissue/vascular space), and 53% im- plant. The implants had less void space than the adjacent bone (30% void space). The implants had bone contact over 60% of their surfaces. A near balance between the implant and surrounding bone had been established.

Wolford et a19 introduced the use of coralline PBHA in orthognathic surgery in 1987, describing its applica- bility for inlay and onlay grafts. Ninety-two consecu- tive patients received 355 PBHA implants, with 294 to the maxilla, 41 to the mandible, and 20 to the midface region. Two hundred two implants were directly exposed to the maxillary sinus. Short-term follow-up showed overall good results. The most common complication was exposure of the midpalatal implant used to stabilize maxillary expansion to the oral or nasal cavity with subsequent loss of the implant. Most of the implants lost were exposed to the oral and nasal cavities as a result of incisions or tears of the mucosa directly over the implants.

Rosen and AckermanloJ1 reported on 46 patients followed-up for 6 to 20 months postsurgery who received coralline PBHA in lieu of bone grafting

during orthognathic surgery and described a complica- tion rate of 4.3%. Moenning and Wolford’* reported on 49 patients with a minimum of 24 months’ fol- low-up in whom 215 coralline PBHA implants had been placed during orthognathic surgery. Nine pa- tients had complications; including four who lost an implant, four who had sinusitis treated with antibiot- ics and decongestants, and one who had partial displacement of an implant. Moenning and Wolfordi3 also reported on the use of PBHA onlay implants stabilized with a bone screw(s) to the anterior man- dible for chin augmentation and showed no bone resorption, absolute stability, and radiographic evi- dence of bone ingrowth into the implants.

The purpose of this prospective study was to determine the long-term clinical and radiographic outcome of the use of PBHA in orthognathic surgery.

Patients and Materials

This prospective study enrolled 245 consecutive patients for PBHA implants. The inclusion criteria were met by 111 patients (32 male and 79 female; average age, 26.8 years; range, 9 to 55 years), who had undergone orthognathic surgery in which rigid fixa- tion and PBHA inlay or onlay implants were used and had a minimum of 5 years follow-up. All patients were operated on by one surgeon (L.M.W.). Medical inclu- sion criteria for the study required the following: 1) the ability to undergo general anesthesia; 2) absence of infection in the areas to be grafted; and 3) absence of systemic diseases such as diabetes or connective tissue and autoimmune diseases. Clinical inclusion criteria required the following: 1) preoperative base- line evaluation with a history, clinical examination, and radiographic imaging, including panoramic radio- graphs and lateral cephalograms; 2) orthognathic surgery or facial augmentation requiring coralline PBHA implants; and 3) a minimum of 5 years of postoperative clinical and radiographic follow-up. In all cases, preoperative antibiotics were given, rigid internal fixation with screw and bone plate fixation was used, and PBHA blocks were carved and placed into bone continuity defects where needed. The antibiotics of choice was intravenous penicillin G or a cephalosporin, given immediately preoperatively and postoperatively, and oral antibiotics for 5 days after discharge from the hospital. Methylprednisolone so- dium succinate IV, 125 mg, was given immediately preoperatively in all cases and continued every 6 hours for six doses.

The surgical technique for placement of the im- plants has been previously described.9 Before implant placement, the surgeon changed gloves, and the basic PBHA implants were first cut with a 701 tapered fissure bur under copious sterile irrigation to help

COTJXELL AND WOLFORD 937

prevent inadvertent fracture of the implant and to wash debris from the pores and then dimensional refinement was accomplished using a no. 15 scalpel blade. Most implants were placed through an intraoral approach (96%) and were wedged into a stable position without any other means of fixation. Chin and zygomatic onlay implants were stabilized to the underlying bone with a bone screw. Detailed records of the size and position of the implants were recorded, and panoramic and lateral cephalometric radiographs were obtained within 1 week postoperatively. AR patients with a minimum of 5-year follow-up were included in this study, as were all patients with known implant failures, although some of this latter group were not followed-up for the 5-year minimum. They were evaluated with panoramic and lateral cephalomet- ric radiographs, a thorough clinical examination, and a history of past and present infections, sinusitis, and any surgical or medical intervention for head, neck, or oral problems was taken. Long-term postoperative radiographs were visually compared with immediate postoperative radiographs for implant position, stabil- ity, resorption, and other significant radiographic changes. The clinical examination evaluated for signs and symptoms of infection, wound dehiscence with implant exposure, changes in the overlying mucosa, and the presence of an oronasal or oroantral fistula.

Results

The average follow-up time was 85.5 months (7.2 years); with a range of 5.0 to 10.3 years. A total of 471 implants were placed: 403 in the maxilla, 44 in the mandible, and 24 in the periorbital region (Table 1). There were 289 implants placed in direct communica-

Position No. No. No. %

Placed Lost Remaining success

Interdental Palatal Lateral sinus wall PterMax fissure Alveolar cleft Maxillary step Piriform rim SSRO Inverted L ramus Chin (inlay) Chin (onlay) Lateral orbit Nasofrontal Zygoma (inlay) Zygoma (onlay) Total

58 0 50 7

207 9

34 0 5 5

48 0 1 0

18 6 :,

10 0 10 1* 14 0

1 0 5 0 4 0

471 23

198

34 0

48

17 6

10 9

14

z 448

100 86

95.7 100

0 100 100

94.4 100 100

90 100 100 100 100 95.1

*Removed because patient did not like the aesthetic result.

tion with the maxillary sinus. Twenty-three implants (4.9%) were removed during the evaluation period, with 448 implants (95.1%) remaining in position. Of the 15 anatomic locations into which implants were placed, removal occurred in only five. Failure gener- ally occurred early, in the first few months post- surgery, although a few cases took longer to identify. The lateral maxillary wall implants had 95.7% success (198 of 207 implants), with nine implants being lost in three patients. Two patients were smokers, and both had a history of presurgical sinus problems. One of these patients had had two prior Le Fort I osteotomies with bone grafts that became infected, resulting in loss of the grafts and maxillary instability. On the left side, there was presurgical loss of the lateral maxillary wall, and the apices of some teeth were exposed. The third patient had chronic bruxism. The maxilla was downgrafted, but postsurgery the bone plates on the right side loosened, with one lateral wall implant fracturing and falling into the sinus, creating an infection that also affected one other implant in the lateral wall. These two implants were removed and the plates restabilized at 2 months postsurgery with no further complications.

The midline palatal grafts had 86% success (43 of 50 implants), whereas in the alveolar cleft region all five implants failed. Four of the latter implants were infected and removed within 3 months of placement; the other was removed at 20 months. Five of the seven palatal implants lost were exposed intraorally at the time of surgery. The other two palatal implants became symptomatic within 2 months of the surgery because of intranasal exposure, although the expo- sure was not immediately identified. These two im- plants were vertically overcontoured, extending signifi- cantly higher than the level of the nasal floor. They were removed at 12 and 13 months postsurgery. Chronic sinusitis persisted in two patients, but the implants appeared well integrated clinically and radio- graphically. These two patients had a presurgical history of chronic sinus problems. Seven implants were placed into a previously irradiated maxilla of one patient without complications.

In the mandible, the chin inlay implants had 100% success (10 of 10 implants), the chin onlay had 90% success (9 of 10 implants), and the SSRO had 94.4% success (17 of 18 implants). The only chin implant removed was not a biologic failure, being asymptom- atic and well healed at 1 year postsurgery, with radiographic evidence of bone ingrowth. However, the patient was unhappy with the aesthetic result, and another surgeon removed it approximately 1 year postsurgery. In the SSRO implant sites, slippage of the implant occurred in two patients, with one implant becoming infected and requiring removal within 2 months after surgery. The other implant, although

938 LONG-TERM EVALUATION OF HA IN ORTHOGNATHIC SURGERY

somewhat displaced, healed uneventfully, and no intervention was necessary.

Discussion

Interpositional bone grafting is indicated in orth- ognathic surgery in which continuity defects exist for the following reasons: 1) to provide bony continuity; 2) to improve healing; 3) to decrease surgical relapse; and 4) to provide surgical stability in traditionally unfavorable orthognathic movements. The use of PBIIA as an alloplastic implant material has the advan- tages of no donor site morbidity, no resorption, no known hypersensitization or immune response, ease of manipulation, no working time constraints, shorter overall surgical time and shorter recovery time, and unlimited volume. The use of coralline hydroxyapatite implants combined with rigid internal fixation in maxillary downgraft and advancement surgery has shown long-term stability. Wardrop and Wolford14 published the results on 14 maxillary advancement cases, 11 maxillary downgraft cases, and three midfa- cial advancement cases, all stabilized with bone plates and PBHA implants, with less than 0.5 mm relapse in any direction.

Biocompatibility of hydroxyapatite has been estab- lished, and this study shows the long-term retention of coralline hydroxyapatite used in orthognathic sur- gery. The results of this study, and previous histologic studies7s show good biologic acceptance of the implants in association with the maxillary sinus.

In this study, a high survival rate occurred for implants placed in the lateral maxillary walls (198 of 207, 95.7%) maxillary step osteotomies (48 of 48, lOO%), interdental osteotomies (58 of 58, lOO%), the pterygomaxillary fissure (34 of 34, lOO%), and the midline of the palate (43 of 50, 86%). These are important locations for maintaining stability in maxil- lary advancements, downgrafts, and expansions. Gen- erally, patients maintain good sinus health postsur- gery, and exposure of the implants to the maxillary sinus does not appear to interfere with healing (Pig l), but rather it promotes healing. Use of the palatal and interdental implants is important to improve stability when performing multipiece maxillary surgery that creates bone gaps in these areas. The interdental implants had 100% survival, whereas some early failures were encountered with the midpalatal im- plants (86% success). The palatal implant failures occurred in cases in which oral contamination devel- oped either through midline incisions in the palatal mucosa or midline tears of the palatal mucosa or nasal mucosa that exposed the implants to the oral or nasal flora and debris. The first five oral exposures of midpalatal PBIIA implants occurred during surgery because the midline palatal soft tissue incisions were

made directly over the implants or the palatal tears occurred in that location (Pig 2). Initially, it was thought that the soft tissue would heal over the implants, but this did not occur. With the subsequent use of unilateral and bilateral parasagittal palatal soft tissue incisions,15 and avoidance of midpalatal tears, this problem has not recurred. We now use unilateral or bilateral parasagittal releasing incisions for expan- sions of 2 mm or greater or when midline soft tissue tears are anticipated (Pigs 3-5). Elevating the palatal soft tissues off the underlying midpalatal bone should prevent soft tissue tears. Because implants are used with midline expansions of 3 mm or more, this soft tissue management technique should provide cover- age of the implant and prevent oronasal fistula forma- tion.

The two intranasal exposures were the result of

FIGURE 1. A, Axial CT scan taken 1 year postoperatively shows PBHA grafts in the anterior and posterior lateral walls of the maxilla with direct exposure to the sinus cavity. The grafts are well healed, and there is no evidence of sinus pathology. 6, Coronal CT scan shows the PBHA grafts in the lateral maxillary walls with good sinus health.

COTTRELL AND WOLFORD

FIGURE 4. Undermining the midpalatal soft tissue flap is completed.

FIGURE 2. The most common complication seen in the initial set of patients was exposure of the palatal implant to the oral cavity at surgery

secondary to placement of the incision or tissue tear occurring directly over the implant.

implants that were vertically overcontoured and ex- tended well above the nasal floor with unrepaired tears in the nasal mucoperiostium occurring at the time of surgery. These two palatal implants failed. Such failure can be prevented by 1) keeping the height of the implant at or below the nasal crest of the maxilla; 2) ensuring primary closure of the nasal mucosa should any tears occur; and 3) appropriately closing nasal mucosa incisions made for access to perform inferior turbinectomies. Since becoming aware of these complications and following the soft tissue protocol previously described, this complica- tion has been virtually eliminated. If this type of exposure occurs, it is recommended to keep the area

clean (chlorhexidine rinses), use antibiotics if neces- sary, and maintain the implants as long as possible to allow primary healing and stability of the other surgi- cal sites. These exposed implants are relatively easy to remove after 2 to 4 months because osseous ingrowth does not occur.

Oronasal fistula formation has rarely occurred, but if it does develop, we recommend waiting at least 6 to 9 months before attempting closure so as to maximize the health and quality of the tissue in the area. If a fistula interferes with eating or speech, a palatal obturator can be constructed and used to cover the area until surgery is performed.

No complications occurred with the interdental implants (n = 56) except for one that was slightly prominent and required minor recontouring at 6 weeks postsurgery; it healed uneventfully. If orthodon- tics requires movement of tooth roots into the im- planted area, PBHA implants should not be used

FIGURE 3. Parasagittal incisions are used to eliminate exposure and loss of midpalatal im lants. The incisions are made medial to the anterior palatine vesse s. P

FIGURE 5. The maxilla has been expanded and the midpalatal implant placed. The flap covers the graft, and the lateral soft tissue defects are left to granulate

940 LONG-TERM EVALUATION OF HA IN ORTHOGNATHIC SURGERY

because the implant will not resorb, and root resorp- tion will likely occur. Bone grafting should be used in such cases. Another option is to place the PBHA implant in the superior aspect of the interdental osteotomy above the root apices. If the bone gap between the segments is too great, fibrous tissue will lill in the alveolar defect instead of bone, and this could create periodontal and stability problems if orthodontic mechanics are used to shift the root(s) of the tooth into the area.

Placing PBHA implants into the mandibular ramus sagittal split osteotomy site does not appear to provide increased stability but can be used to improve bony fill in large gaps. Stability of the implant is important because slippage occurred in two cases, and one became infected and had to be removed. We have not placed an implant in sagittal split areas in over 10 years because we see no aesthetic nor functional benefit with the current surgical techniques we are using.9@ The chin onlay (n = 10) and inlay (n = 10) implants, and the nasofrontal (n = l), lateral orbit (n = 14), and zygoma onlay (n = 4) and inlay (n = 5) implants are very predictable when appropriately wedged in posi- tion or stabilized with screw fixation. None of these implants were lost for biologic reasons, and only one chin implant was removed by another surgeon be- cause the patient was unhappy with the esthetic result. This chin onlay graft was well healed and asymptomatic at the time of removal, at 1 year postsurgery.

All five of the alveolar cleft implants failed, and use in this area is not recommended. Most likely this was attributable to a lack of rigidity of the implant and oronasal communication/contamination because of inability to achieve a watertight soft tissue closure, resulting in contamination with oral/nasal flora and debris.

It is recommended that the surgeon change gloves before handling the PBHA material, because oral flora and debris previously picked up on the gloves could contaminate the implant. Several important character- istics of coralline hydroxyapatite should be noted. PBHA is brittle in its initial form and must be handled and shaped carefully so that it does not inadvertently fracture, although the material becomes very strong and shows higher compressive strength than bone when integrated. It is important to use irrigation when trimming the material with a bur or scalpel because this improves its strength, minimizes aberrant frac- ture, and helps keep debris out of the pores. Screws placed through the material, as in the PBHA chin or cheek implant, should be inserted with a lag screw technique to prevent splitting of the material, and the screws should not be overtightened.

Rigid fixation of the repositioned maxilla is para-

mount to provide stress shielding for the PBHA implants during healing. The implants in the maxilla are trimmed and wedged in position and are not directly fixed. A soft diet is encouraged for 8 to 12 weeks postoperatively to minimize micromovement and help prevent displacement or fracture of the implants. A previous histologic study by Holmes, Wardrop, and Wolford’ showed that bone growth through the implants is complete at 4 months, al- though the bone is of an immature quality. There is no significant increase of bone volume within the im- plant after that time. After 4 months, the bone undergoes a maturation phase that may last for 9 to 12 months.

Complications not seen in this study population, but which have rarely occurred, are fracture of im- plants postoperatively and displacement of fragments into the sinus or lateral to the lateral maxillary wall. Displacement of the PBHA implant or fragments can occur as a result of inadequate rigid fixation and stress shielding, improper contouring or placement of the implant into the osteotomy site, parafunctional habits (i.e., clenching, bruxism), or poor patient compli- ance. Infection can occur at any site, but it most often appears to be correlated with exposure to the oral or nasal flora and debris, improper fixation, mobility of the implant, fracture of the graft and fragment displace- ment, or the presence of a presurgical infection in the area. Parafunctional habits can contribute to mobility of the maxilla, which will interfere with healing, significantly decrease bone ingrowth, and possibly could cause fracture or displacement of the implant. Control of these parafunctional habits postsurgery will enhance the outcome.

Long-term follow-up (average, 7.2 years; range, 5 to 10.3 years) on a large patient population (n = 111) in which PBHA was used as a bone graft substitute (n = 471 implants) in orthognathic surgery and for facial augmentation has shown the efficacy of this material for these applications. Identification of the problem areas leading to implant failure, and the technical modifications developed to prevent recur- rence of these problems, should further improve the success rate of PBHA implants.

References 1. Araujo A, Schendel SA, Wolford LM, et al: Total maxillary

advancement with and without bone grafting. J Oral Surg 38:849, 1978

2. Bloomquist DS, Turvey TA: Bonegrafting in dentofacial deformi- ties, in Bell WH (ed): Modern Practice in Orthognathic and Reconstructive Surgery. Philadelphia, PA, Saunders, 1992, p 831

3. Epker BN, Friedlaender NC, Wolford LM, et al: The use of freeze-dried bone in middle-third face advancements. J Oral Surg 42~278, 1976

4. Kent JN, Zide MF, Kay JF, et al: Hydroxylapatite blocks and

JOSEPH F. PIECUCH 941

5.

6.

7.

8.

9.

10.

particles as bone graft substitutes in orthognathic and recon- structive surgery. J Oral Maxillofac Surg 44:597, 1986 Holmes RE: Bone regeneration within a coralline hydroxyapa- tite implant. Plastic Reconstr Surg 63:626, 1979 Holmes RE, Hagler HK, Coletta CA: Thick section histometry of porous hydroxyapatite implants using backscattered electron imaging. J Blamed Mater Res 21:731, 1987 Holmes RE, Wardrop RW, Wolford LM: Hydroxylapatite as a bone graft substitute in orthognathic surgery: Histologic and histometrlc findings. J Oral Maxillofac Surg 46:661,1988 Nunes CR, Simske SJ, Sachdeva R, et al: Long-term ingrowth and apposition of porous hydroxylapatite implants. J Biomed Mater Res 36:560, 1997 Wolford LM, Wardrop RW, Hartog JM: Coralline porous hydrox- ylapatite as a bone graft substitute in orthognathic surgery. J Oral Maxillofac Surg 45:1034, 1987 Rosen HM: Porous, block hydroxyapatite as an interpositional bone graft substitute in orthognathic surgery. Plast Reconstr Surg 83:985, 1989

11. Rosen HM, Ackerman JL: Porous block hydroxyapatite in

orthognathic surgery. Angle Orthof 61:185,1991 12. Moenning JE, Wolford LM: Coralline porous hydroxyapatite as a

bone graft substitute in orthognathic surgery: 24-Month fol- low-up results. Int J Adult Orthod Orthog Surg 4:105, 1989

13. Moenning JE, Wolford LM: Chin augmentation with various alloplastic materials: A comparative study. Int J Adult Orthod Orthognath Surg 4: 175,1989

14. Wardrop RW, Wolford LM: Maxillary stability following down- graft and/or advancement procedures with stabilization using rigid fixation and porous block hydroxyapatite implants. J Oral

Maxillofac Surg 47:336, 1989 15. Reiche-Fischel 0, Wolford LM: Parasagittal incisions and soft

tissue healing after surgical maxillary expansion. J Oral Maxillo- fat Surg 54:92, 1996 (suppl3)

16. Wolford LM, Davis WMcL: The mandibular inferior border split: A modification in the sagittal split osteotomy. J Oral Maxillofac Surg 48:92, 1990

j Oral Maxiilofac Surg 56:941-942, 1998

Discussion

Long-Term Evaluation of the Use of Coralline Hydroxyapatite in Orthognathic Surgery

Joseph F. Piecuch, DMD, MD Clinical Professor, University of Connecticut, Farmington, Connecticut

Before commenting on this article by Drs Cottrell and Wolford, I must disclose to the reader that about 15 years ago I had substantial support for laboratory and clinical research project@ from the Interpore Company, testing the porous hydroxyapatite now known as Interpore-200. Although my decade of research with this material has long since been concluded, I maintain a strong conviction that it does indeed have a future role as a bone graft substitute. However, the specific applications have perhaps not yet been determined. Therefore, I congratulate Drs Cottrell and Wolford for having the scientific interest and tenacity to continue looking critically at their own patients so many years later. With the plethora of published “results” in the literature and in presentations at national conferences describing success rates at intervals sometimes so short that they are less than the natural healing period, it is certainly refreshing to see a report that reviews a truly long-term experience of up to 10 years.

The strong points of this article include a review of the known literature on the specific application of Interpore- 200 to orthognathic surgery, documentation of long-term biocompatability of the material in this type of use, descrip- tion of a reasonable method of carving and shaping the hydroxyapatite at surgery, and an honest commentary regarding success and failure for different clinical situations. However, there are some concerns with this report that should be kept in mind if the reader were to consider using this material for these purposes.

Whether this is a prospective study, or a retrospective review as admitted by the authors in a previous article on the same material3 is, in my opinion, open to question. Semantics aside, the article is purely a description of observations made on a long-term basis without any real information as to success rates for the material, because only 111 of the original 245 patients were presented in this report. The authors honestly include all patients who had known complications, regardless of when in the follow-up period the complication occurred. Yet, the absence of information on the other 134 patients who had this material inserted, whether clinical observation was shorter-term or not and whether adequate radiographs were available or not, compromises the data. The reader simply does not learn whether these patients are currently under observation, but not reported, or simply lost to follow-up. If lost to follow-up, why? Were there other complications of which the authors may not be aware?

Although comparisons with bone grafts are made in the discussion section of this article, and in other referenced articles by the same group, no direct comparisons are available. This is not a controlled study; there is no control material. There are also no other controlled comparisons of bone and hydroxyapatite for orthognathic surgery in the literature. All comparisons with bone are really asumptions, comparing one report with another, one group’s work with another, etc. Hence, no conclusion can be drawn by the authors or by the reader suggesting that porous hydroxyapa-

tite is actually better than, the same as, or worse than autologous bone. That conclusion awaits future study. All we know from this article is that the material was stable and biocompatible in most of the applications, and for most of the patients reported.

Indications for the use of porous hydroxyapatite in osteotomy surgery are not given in this article. The authors’ statement in the Materials and Methods section that the