Demineralized bone matrix as an alternative for mastoid obliteration and posterior canal wall reconstruction: results in an animal model

Effect of Bone Powder/Mesenchymal Stem Cell/BMP2/Fibrin Glue on Osteogenesis in a Mastoid Obliteration Model

BACKGROUND/AIM

This study aimed to prospectively compare the osteogenesis of bone powder (BP) substances with and without mesenchymal stem cells (MSCs) and evaluate the synergistic effect of topically applied recombinant human bone morphogenic protein-2 (BMP2) on MSC-loaded BP using fibrin glue in a mastoid obliteration model.

MATERIALS AND METHODS

To determine the expression of osteocyte-specific genes, total RNA was isolated from three MSC groups: Untreated MSCs, MSCs cultured with BP, and MSCs cultured with BP and BMP2. Real-time polymerase chain reaction was carried out with specific primers of osteogenesis-related genes runt-related transcription factor 2, osteocalcin, osteoprotegerin, osterix, alkaline phosphatase, transforming growth factor beta, and type I collagen. Live/dead staining was also performed. To observe the adhesion of MSCs to the BP, MSCs were treated with BP for 2 days and the surface was observed by scanning electron microscopy (SEM). Under general anesthesia, mastoid obliteration was performed in rats using three groups: treated with BP alone, BP/MSCs, and BP/MSC/BMP2. Before decapitation at 8 weeks post operation, in vivo micro computed tomography (micro CT) was performed. The bullae were dissected, fixed, and decalcified. followed by dehydration, paraffin embedding, and staining by hematoxylin and eosin and Masson's trichrome.

RESULTS

SEM showed the MSCs to be well-attached to the superficial area of the BP. The expression of osteocyte-specific genes was the highest in the MSCs cultured with BP and BMP2, followed by cultured with BP only, and untreated MSCs. The BP/MSC/BMP2 group showed the highest radiodensity of bullae in microCT analysis. The microCT findings revealed that the BP/MSC/BMP2 group showed the most enhanced osteogenesis of the scaffold compared to the other two groups. No significant difference was found in osteoconductive osteogenesis between the control and BP/MSC groups. However, the BP/MSC/BMP2 group showed significantly enhanced osteoconductive osteogenesis and osteoinductive change of the BP as shown by hematoxylin and eosin staining. Histomorphometry of osteogenesis revealed that the difference between the BP/MSC/BMP2 group and the other two groups was statistically significant.

CONCLUSION

A small amount of BMP2 is necessary during MSC loading to enhance the osteogenesis of BP and avoid complications associated with high doses of BMP2. These results may be applicable to mastoid obliteration in clinical practice.

[The application of mastoidoplasty in repeated scanning operations on the ear]

The objective of the present study was to evaluate the outcomes of mastoid obliteration with the use of the orthotopic bone tissue taken from the linea temporalis region. It was shown that this region is the optimal site at the temporal bone for the harvesting of the plastic bone material to be used in mastoidoplasty during secondary sanitizing surgical interventions on the patients with mastoid cavity problems after canal wall-down mastoidrctomy under conditions of the deficiency of the orthotopic bone tissue. The application of such tissue for the purpose of mastoid-obliteration surgery provides a number of advantages over other methods of mastoidoplasty, in the first place from the standpoint of tissue biocompatibility. Multispiral computed tomography (MSCT) of the temporal bones is a highly informative and non-invasive technique for the study and control of the patients' condition during the late postoperative period following a secondary sanitizing surgical intervention involving mastoidoplasty with the application of the orthotopic bone tissue.

Reconstruction of the mastoid using a titanium cage

OBJECTIVES

Evaluate reconstruction of the posterior canal wall, including the mastoid cavity after canal wall-down cholesteatoma removal.

METHODS

A titanium mesh metal cage was used to rebuild the posterior auditory canal wall and mastoid cell system in 12 patients undergoing cholesteatoma removal. The cage was then covered with pieces of cartilage to reconstruct the soft tissue surface.

RESULTS

All reconstructions epithelialized completely. There was no denudation of the titanium material or signs of extrusion. Recurrences of cholesteatoma occurred twice according to the condition of the underlying disease, not related to the material.

CONCLUSION

The titanium cage showed good biocompatibility in the middle ear space and the potential for rebuilding the mastoid cell system, making it a versatile tool for primary cases with large defects and in revision cases where soft tissue with cartilage-only reconstructions failed. Reconstruction of the posterior canal wall and mastoid by means of a titanium cage can be used in situations where adhesive tensions need a more stable construction and support of the posterior canal wall.

Donor-site morbidity following minimally invasive costal cartilage harvest technique

OBJECTIVES

Autologous costal cartilage is a promising alternative for mastoid obliteration. However, donor-site morbidities of the chest wall limit the use of this graft. To address this issue, we have developed a minimally-invasive technique of harvesting costal cartilage and report donor site morbidity associated with the procedure.

METHODS

Donor site morbidities were evaluated for 151 patients who underwent costal cartilage harvest, canal wall down mastoidectomy, and mastoid obliteration. Pain and cosmetic concern were evaluated via visual analogue scale (VAS). Scars were evaluated via the modified Vancouver Scar Scale (VSS) and the Patient and Observer Scar Assessment Scale (POSAS). Postoperative complications were assessed during the follow-up period.

RESULTS

The mean duration of noticeable pain was 5.3 days post operation. The mean VAS score for pain was 3.0 of 10 on the first day after the operation and gradually declined. At the 6 months post operation, the mean VAS cosmetic score at the costal cartilage harvest site was 0.6 of 10. The mean VSS score was 9.5 out of 10 total, and the mean POSAS score was 23.27 out of 110 total.

CONCLUSION

The minimally-invasive chopped costal cartilage harvest technique resulted in acceptable pain, cosmetic concern, and postoperative complications for most patients. There were no major postoperative complications. Costal cartilage is an acceptable donor for mastoid obliteration in canal wall down mastoidectomy, especially in the context of the extremely low donor site morbidity of the minimally-invasive technique presented in the study.

Obliteration of temporal dorsal bulla in guinea pigs using different types of calcium phosphate

OBJECTIVE

The purpose of this study was to evaluate the applicability of different calcium phosphate types after mastoid obliteration procedure using the guinea pig as an animal model.

MATERIALS AND METHODS

Twenty six male guinea pigs were used for the experimental study. Four guinea pigs were used as a normal control group, with the remaining used for the experimental group. After bulla mucosa was removed, non-obliterated ears were used as control and granular (Polybone-G) or powder (Polybone-P) types of Polybone (tricalicium phosphate and polyphosphate) were applied into the dorsal bulla. The radiological and histologic findings were obtained from each animal at 8 and 20 weeks after obliteration.

RESULTS

On radiological examination, thickening of the bulla wall observed in all experimental groups compared with normal group. Increased homogenous bony densities continuous with the bulla wall were observed in the Polybone-G group compared to the other experimental groups, and some isolated bony densities were observed in the Polybone-P group. Histopathologic findings showed increased new bone formations and less inflammatory reactions in the Polybone-G group compared to the Polybone-P group.

CONCLUSION

This study demonstrates that granular type calcium phosphate can be used as effective material than powder type in mastoid obliteration.

Mastoid obliteration using a hyaluronic acid gel to deliver a mesenchymal stem cells-loaded demineralized bone matrix: an experimental study

BACKGROUND AND OBJECTIVE

The aim of this study was to evaluate whether a combination of expanded human mesenchymal stem cells (hMSCs) with hyaluronic acid gel in human demineralized bone matrix (hDBM) can promote osteogenesis in a mastoid obliteration procedure, with using the guinea pig as an animal model.

MATERIALS AND METHODS

Fourteen male guinea pigs were used for the experiment. Bulla obliteration using 6-diamidino-2-phenylindole (DAPI)-labeled hMSCs (2x10(6)) loaded into hDBM with hyaluronic acid hydrogel was performed in the experimental group (n=7). The control group was obliterated using hDBM only (n=7). The histologic findings and microCT images were obtained from each bulla at 3 and 7 weeks postsurgery.

RESULTS

The increased soft tissue intensity caused by chondrogenic differentiation around the implanted hMSCs-loaded hDBM was identified, as compared to the hMSCs-free hDBM group. All the hMSCs-loaded hDBM at 7 weeks post-implantation displayed greater amounts of bone filling the bulla space, as compared to the hMSCs-free hDBM implanted group. In the hMSCs-free hDBM group, microCT shows incomplete new bone formation, as compared to the hyaluronic acid gel-hMSCs treated group.

CONCLUSION

The successful formation of bone using allogeneic hMSCs loaded onto hDBM and hyaluronic acid hydrogel to repair critically sized bulla defects in the guinea pig model was accompanied with the absence of any local response to the foreign cells. The use of hMSCs-loaded hDBM and hyaluronic acid hydrogel is appropriate for performing clinical mastoid obliteration.

Pediatric Cholesteatoma: Canal Wall Window Alternative to Canal Wall Down Mastoidectomy

OBJECTIVE

A previous pilot series described a hybrid mastoidectomy technique, canal wall window (CWW), which substituted for the canal wall down (CWD) procedure and involved slitting the posterior canal wall. The current, larger series compares the results of the CWW procedure with conventional surgical techniques.

STUDY DESIGN

Retrospective analysis of 78 pediatric ears.

SETTING

Academic tertiary referral center.

PATIENTS

The mean patient age was 13.5 years.

MAIN OUTCOME MEASURE(S)

The data analyzed included ears later requiring conversion from CWW to CWD, dry/moist ear results, recidivation determined by two separate methods, and audiometric data statistically analyzed using independent-samples analysis (unpaired, two-tailed Student's t test).

RESULTS

First, of 42 CWW ear procedures, 6 (14%) later required conversion to CWD. Second, dry ear results were as follows: for CWW, 94%; for CWD, 92%; and for CWU (canal wall up), 90%. Third, recidivation determined at 1 year (standard rate) was, for CWW, 19.5%; for CWD, 0%; and for CWU, 7.7%; the at-risk calculation rate was, for CWW, 27%; for CWD, 0%; and for CWU, 8.3%. The 6-year recidivation rate for all three surgical techniques was 0%. 4). The mean preoperative-to-postoperative four-tone air-bone gap change was, for CWW, from 29.7 to 26.4 dB; for CWD, from 32.9 to 39.0 dB; and for CWU, from 21.0 to 25.2 dB (postoperative CWW to CWD, p < 0.005). A postoperative air-bone gap result of 0 to 20 dB was achieved as follows: with CWW, in 13 of 36 ears; with CWD, in 2 of 14 ears; and with CWU, in 9 of 22 ears.

CONCLUSION

Frequently, a CWW procedure can be substituted for a traditional CWD procedure. In the extended series, the CWW technique continued to provide hearing results similar to CWU rather than to CWD procedures in a young population who will bear the surgical outcome for many decades.

The Use of Novabone and Norian in Cranioplasty: A Comparative Study

Bone replacement products have enhanced the ease of reconstructing bone while improving morbidity related to bone harvest. Although these products are successfully used, studies of bone healing and biomechanical strength are lacking. We aimed to compare how Norian CRS (cranial replacement substance) and Novabone C/M heal in a cranial defect. Adult New Zealand rabbits underwent removal of a critical size cranial defect. The defect was filled with Novabone (n = 8), Novabone plus demineralized bone matrix (n = 8), or Norian (n = 8), or it was left empty (n = 8). Rabbits were euthanized at 8 weeks. Cranial specimens were harvested and soft radiographs, contact microradiographs, and biomechanical testing were done. Soft radiographs revealed opacification like adjacent bone with Novabone, which was augmented when Novabone was combined with demineralized bone matrix. Norian maintained an opaque appearance. The control group did not heal. Contact microradiographs demonstrated bone within the healing defect with Novabone, which was augmented by demineralized bone matrix. Norian was not replaced with bone but served as a scaffold for bone formation. Biomechanical indentation testing demonstrated that the stiffness of Norian was the highest. Novabone plus demineralized bone matrix had a higher stiffness than Novabone alone. All experimental groups had a statistically significant difference compared with Norian. None of the groups achieved the strength of unoperated native bone. Studying two popular products, we found evidence that Novabone was incorporated into cranial bone, regenerating the bone. Novabone healed at a faster rate, creating a stronger product, with demineralized bone matrix. The biomechanical strength of the healed defect was higher in the Norian group, because the bone cement remained solid and was not incorporated, unlike crania reconstructed with Novabone.

The use of demineralized bone matrix for mastoid cavity obliteration

OBJECTIVE

To evaluate the use of demineralized bone matrix as a graft material for mastoid cavity obliteration in the treatment and prevention of problematic mastoid cavities.

STUDY DESIGN

The study is a retrospective review of patients identified using a computerized otology database.

SETTING

Tertiary care referral center.

PATIENTS

Patients were included in this study if they underwent mastoid obliteration using demineralized bone matrix.

INTERVENTION

Mastoid obliteration was performed for revision of a problematic mastoid cavity (n = 8) or primarily after canal wall down mastoidectomy for recurrent cholesteatoma (n = 3).

MAIN OUTCOME MEASURES

Data were collected to evaluate the ability to achieve a dry ear canal. Postoperative healing time and hearing results were also assessed.

RESULTS

A dry ear canal was achieved in all patients with a follow-up of 6 to 20 months (average, 14.5 mo). Eight patients (73%) had a well-healed, dry ear canal by their first postoperative visit (9 wk). One patient required 12.5 weeks to heal. Two patients (18%) had more prolonged granulation at the ear canal incision, which resolved in 17 and 28 weeks, respectively. The average preoperative pure-tone average air-bone gap was 47 +/- 14.9 dB (mean +/- SD), compared with postoperative values of 27.6 +/- 12.8 dB (p = 0.0033; paired t test). This represents an average pure-tone average air-bone gap closure of 20 dB.

CONCLUSION

The use of demineralized bone matrix as a graft extender in mastoid obliteration allowed creation of a dry, smooth-contoured canal in all patients studied. A significant improvement in hearing was also obtained. Demineralized bone matrix is an acceptable graft alternative for mastoid obliteration.