- Email: [email protected]
Experimental evaluation of drills for extended frontal sinusotomy
Experimental evaluation of drills for extended frontal sinusotomy WERNER HOSEMANN, and Ulm, Germany
MD, PHD,
DANIELA HERZOG,
MD,
ACHIM G. BEULE,
OBJECTIVE: Endonasal extended frontal sinusotomy is needed in rare cases of therapy-resistant chronic frontal sinusitis. Several types of burs have been invented to ablate strong bone in the frontal sinus access but nevertheless surgical results seem to differ significantly. The benefits and shortcomings of different burs are subjected to a comparative evaluation. STUDY DESIGN: Five cadaver specimens were duplicated by means of dental molding and casting techniques to provide identical microanatomy for comparative studies on frontal sinusotomy. Different burs (conventional straight bur, right-angled bur according to Blokmanis, and curved frontal sinus bur) were applied to create a type IIb frontal sinusotomy according to Draf in microanatomical replicas. The geometry of the frontonasal neoostium was measured and its dimensions were contrasted to the collateral damage. Bone ablation was calculated by repeated weighting and the area of damaged mucosa was quantified using a 3D analyzing system. RESULTS: A frontal sinus neoostium measuring 9 ⴛ 10 mm on average was created by type IIb frontal sinusotomy according to Draf. The complementary use of an angled bur showed some specific improvements that applied best to spacious anatomic specimens. Those specimens subjected to an extensive use of the straight drill revealed significant collateral damage forming a contrast to minor enlargement of the neoostium. The curved frontal si-
From the Department of Otorhinolaryngology, Head and Neck Surgery, University of Greifswald, Greifswald (Drs Hosemann, Beule, and Kaftan); the Department of Otorhinolaryngology, University of Regensburg, Regensburg (Dr Herzog); and the Department for Lasertechnology in Medicine, University of Ulm, Ulm (Dr Herzog). There is no financial relationship of any of the authors with the manufacturers of any of the materials subjected to evaluation. There are no other (subtle) conflict of interests. Reprint requests: Werner Hosemann, MD, Head of the Department of Otorhinolaryngology–Head and Neck Surgery, University of Greifswald, Walther Rathenau Str. 43-45, D-17487 Greifswald, Germany; e-mail, [email protected]. 0194-5998/$30.00 Copyright © 2004 by the American Academy of Otolaryngology–Head and Neck Surgery Foundation, Inc. doi:10.1016/j.otohns.2004.02.016
MD,
and HOLGER KAFTAN,
MD,
Greifswald, Regensburg,
nus bur showed considerable technical insufficiencies. CONCLUSIONS: Judicious use of the straight drill is recommended for those rare cases of therapy-resistant frontal sinusitis treated by an extended type of frontal sinusotomy. New technical refinements of the curved frontal sinus burs should be subjected to repeated evaluation. (Otolaryngol Head Neck Surg 2004;131:187-91.)
E
ndoscopic endonasal surgery has gained wide acceptance for treatment of therapy-resistant chronic paranasal sinusitis. Irrespective to significant differences in the detailed operative strategy propagated by various rhinological schools, most surgeons strive for optimizing ventilation and drainage of the dependent paranasal sinuses using special instruments designed for microsurgery.1 The frontal sinus represents one of the few anatomical areas left in which the microsurgical concepts mentioned are subjected to an ongoing and controversial discussion. Common therapy-resistant frontal sinusitis can be treated in the vast majority of cases with surgery that is directed exclusively to correction of the primary anatomic key areas of the anterior ethmoid. However, rare cases of chronic frontal sinusitis require optimization of the anatomy of the frontonasal transition zone itself.2-4 Addressing the diversity of diseases and surgical requirements, some authors have developed a step-wise surgical concept of endonasal frontal sinus surgery: Draf4 has defined 3 different types of interventions ranging from mere operative exposure of the frontal sinus ostium to an extended endonasal “median drainage”. May and Schaitkin5 have adopted this classification and added some refinements. Any major surgery on the frontal sinus access must take into account the local microanatomy,6 especially of the superior nasal spine revealing strong bone of up to 1 cm3. The necessary ablation of comparatively compact bone may pose major problems for the application of delicate microsurgical instruments. In addressing this fact, surgeons have used different types of burs to ablate strong bone and to enlarge the operative access to the frontal sinus. However, personal experience has shown that even the largest frontal sinus neoostium may close by secondary scaring as a result of widespread areas of 187
188 HOSEMANN et al
Otolaryngology– Head and Neck Surgery September 2004
traumatized tissue. In addition to the individual predisposition to increased reparative inflammation and scarification, the detailed operative strategy and the instrumental technique seem to be criteria for success. These facts and speculations motivated us to start a comparative evaluation of burs based on exact measurements. Setting this goal, we developed an anatomic model that offered identical microanatomy to repeated surgical interventions. MATERIAL AND METHODS Five human sagittally split cadaver specimens revealing the one-sided paranasal sinus system were provided by the Department of Anatomy, University of Regensburg, Germany. Defined differences in the spacial dimension of microanatomy of the frontonasal transition zone served as selection criteria for the specimens. To ensure exact comparison of different manipulations applied subsequently to identical microanatomic specimens, the key area of the cadavers needed to be duplicated. The bony frontonasal transition zone containing inferior parts of the frontal sinus together with the medial supraorbital rim, the root of the nose, the anterior ethmoid, and the lamina papyracea was excised in a single piece using an oscillating saw. Applying dental molding and casting techniques (impression compound: vinyl polysiloxane; casting material: polymethylmethacrylate) on the five resected pieces of bone, 5 ⫻ 9 detailed duplicates of the anatomic frontonasal transition zone were gathered (Fig 1). Any irregularities of the duplicates were removed by hand. Following this, the duplicates were reintroduced into the anatomic specimen one after another. Each duplicate was fixed on the corresponding anatomic specimen with miniplates and screws. Applying this technique, 5 different series of identical anatomic specimens were available for the comparative study of extended frontal sinusotomy using drills. Initially, an anterior ethmoidectomy was performed in each specimen under the microscope (f ⫽ 250 mm) exposing the anterior skull base. Intraoperative view was improved by nasal specula. After this, an enlarged frontal sinusotomy type II according to Draf was performed applying different drills separately or by complementary use. Unfortunately, a sinusotomy type III according to Draf could not be performed because of shortcomings (paramedian cut) of the anatomic specimens. A straight bur was used in every case (n ⫽ 45) (Intra-handpiece, Fischer Co., Freiburg, Germany; bur head 5 mm ⭋). The modified dental drill according to
Fig 1. Parasagittally half split anatomic specimen of the skull with reattached methacrylate specimen (encircled). Insert: Series of duplicates of the frontonasal transition zone gained from 5 anatomic specimens (a– e).
Blokmanis (No. 52G E 229587, length of handpiece 100 mm, 90° angle distally; KaVo Co., Warthausen, Germany)7 was used complementarily in a second series (n ⫽ 5 ⫻ 2) (Fig 2). A third series of specimens (n ⫽ 5 ⫻ 2) was subjected to a “maximum drill-out” applying the straight drill exclusively but most extensively disregarding circumscribed destructions of the nasal pyramid and the external frontal sinus wall (but preserving the frontal skull base and also the posterior frontal sinus wall by all means). Another small series of experiments was conducted using special frontal sinus burs with a curved shaft and a flexible axle (RAD 55 TM, 55° angle, Xomed, Jacksonville, FL). For certain reasons listed below, this series was restricted to preliminary studies on bony cadavers. The inner surface of the methacrylate sinus duplicates were marked with two different colors preceding surgery on the frontal sinus (color 1: inner surface of sinus frontalis representing frontal sinus mucosa; color 2: surface of the ethmoidal cavity following anterior ethmoidectomy, prior to frontal sinusotomy–representing spared ethmoidal mucosa). Next to frontal sinusotomy, the methacrylate block was detached from the anatomic specimen. The relative mucosal damage could be analyzed by comparison of the surface area revealing loss of color (Fig 3). A series of 5 ⫻ 3 specimens operated on was subjected to an optical 3D-analyzing system based on the micromirror digital stripe projection process (phase shift rapid in vivo measurement of skin [PRIMOS], GFM Company, Berlin-Teltow, Germany). The methacrylate specimens were sagittally split allowing optical measurements to be focused on the new bottle-
Otolaryngology– Head and Neck Surgery Volume 131 Number 3
Fig 2. Curved bur, right-angled bur according to Blokmanis7 and conventional straight bur for extended endonasal frontal sinus surgery.
Fig 3. A) Methacrylate specimen detached from the skull, view from below. The left frontal sinus neoostium (type II according to Draf) is shown after bone work using exclusively the straight bur. 1: ‘Mucosa' of the anterior skull base. 2: wound area due to drilling. 3: intact ‘mucosa' of the posterior frontal sinus wall. B) Same series as in A. This specimen shows the neoostium created by complementary use of the straight bur and also the drill according to Blokmanis. The arrow indicates a bony spur which had been removed. C) Same series as in A and B. This specimen shows the neoostium created by a maximum ‘drill-out' procedure.
neck around the frontal sinus neoostium. The extent of “exposed bone” corresponding to the reduction of the colored areas was digitally analyzed (Fig 4). Ablation of bone was calculated by repeated weighting of the methacrylate blocks having in mind the specific weight of the dry material (1.18 g/ml).
HOSEMANN et al
189
Fig 4. Three sagittally split methylmethacrylate specimen are shown in a digital 3D version (1: straight bur; 2: maximum drill-out; 3: complementary use). The specimens revealing the frontal neoostium are seen obliquely from below (asterisk: ⬘spina nasalis superior’). The picture on the upper right serves for orientation of the detailed digital images only (a ⫽ anterior; p ⫽ posterior; s. front. ⫽ frontal sinus; ext. nose ⫽ external nose).
RESULTS Exclusive application of the straight bur resulted in a frontal sinus neoostium type II of 9.4 (6-10.5) mm length and 10.9 (8-15) mm width (N ⫽ 5). The neoostium showed an individual shape resembling mostly a triangle, circle, or a drop (Fig 3). The specific wound area was 317 (135-590) mm2 (Figs 5 and 6). Analysis of the specimen operated on by view from top and below revealed, in most instances, persisting bony overhangs or edges inside the frontal sinus. The range of action of the bur was restricted especially in the anterior working direction. At the same time, optical control by the microscope was restricted. The complementary use of the drill according to Blokmanis allowed ablation of additional 104 (2-193) mm3 of bone around the superior neoostium mainly anteriorly at the expense of the superior nasal spine. Moreover, bony overhangs and edges located laterally or medially could be removed, both under maximum preservation of the inferior mucosa. The sinusotomy resulted in a wound area of 330 (150-594) mm2. To ensure realization of the same neoostium by exclusive use of conventional straight burs, extensive planar bone ablation would have been needed inferior to the anatomical target area. The length of the frontal sinus neoostium gained 1.3 mm on average, and the width increased by 0.9 mm (N ⫽ 5). On the other hand, introduction of the angled drill constantly caused restrictions of optical control of the operative field. The range of action of the instrument was impaired in cases of narrow-spaced anatomy and generally in the superior and lateral direction.
190 HOSEMANN et al
Fig 5. Average diameter of the frontonasal neo-ostium created with the straight bur, the complementary use of the straight and angled bur (“compl. use”) and the maximum ‘drill-out' procedure (“drill out”).
The maximum drill-out resulted in ablation of an additional 184 (51-340) mm3 bone on average. Most specimens showed destruction of the superior nasal skeleton around the lateral nasofrontal suture. The corresponding wound area increased to 352 (186-578) mm2. However, the neoostium showed some augmentation (length: ⫹ 1.1 mm, width: ⫹ 0.9 mm), too. The ratio of the specific benefits (larger neoostium) and side effects (increased wound area) was best in specimens showing narrow spaced local anatomy. The small series of experiments using the special curved frontal sinus bur had to be stopped prematurely: The flexible axle broke in any case soon after starting major bone work on the superior nasal spine. The producer has been informed and technical improvements are in preparation. Ablating bone around the frontal sinus neoostium with the Blokamnis drill revealed some general inconveniences with respect to handling inside the nose and to the range of view of any telescope. The latter was primarily caused by focal thickening of the bur located at the 90° angle. We made an acrylic duplicate of the bur and simulated different other angulations of the tip of the instrument: a 60°-angled tip showed the most significant benefits with respect of the range of action and also to the simultaneous optical control. DISCUSSION Contemporary endonasal sinus surgery has given rise to distinct extended procedures focussing on the frontal sinus.4,8-10 Any surgical technique must deal with the strong bone of the nasal process of the frontal bone (spina nasalis interna).6 To address this fact, several types of burs have been introduced recently to
Otolaryngology– Head and Neck Surgery September 2004
Fig 6. Wound area created around the frontonasal neoostium by use of different burs (for legends, refer to Fig 5).
ablate this bone. It may be noteworthy to call to attention to the fact that Halle11 had, in 1906, presented a special bur system especially designed for frontal sinusotomy. However, irrespective of impressive dimensions of the frontal sinus neoostia created intraoperatively, the long-term surgical results are sometimes flawed with reactive scaring, leading to a relapse of insufficiency of frontal sinus drainage and ventilation.12,13 As a consequence, surgeons strive to optimize the operative strategy by minimizing tissue trauma. Blokmanis7 introduced a modified dental drill with a 90°-angled tip to work around the corner at the frontal sinus access. Although collateral tissue trauma may be reduced avoiding the linear operative access needed in use of straight burs, the angled instrument shows considerable bulk inside the nose interfering with the endonasal optical control. Several industrial companies have presented slim curved burs with a flexible power transmission (axle) as an alternative choice. The investigations presented herein are based on a first series of experiments evaluating the benefits and shortcomings of burs recommended for extended frontal sinusotomy. We attached great importance to comparative use of instruments in specimens revealing identical anatomy. According to our experiments the contemporary surgical instruments are far from being perfect. Technical insufficiencies mainly affect the curved frontal sinus burs at that time, and in the meantime, announced technical refinements should be subjected to a second evaluation. At the moment, judicious use of the straight drill may be recommended for those rare cases that are in need of major bone work at the frontonasal transition zone. Complementary use of the Blokmanis bur is recommended for cases in which
Otolaryngology– Head and Neck Surgery Volume 131 Number 3
there are generous dimensions of local anatomy because of minimized mucosal trauma, as shown in our data. The presented evaluation may lay the foundation for further technical innovations and serve for the process of continuous improving of the individual operative strategy. CONCLUSION The enlarged frontal sinusotomy type II/III according to Draf4 has become an established type of treatment for special cases of chronic frontal sinusitis. Local anatomy exhibiting areas of strong bone calls for the application of burs. The use of burs at the frontoethmoidal transition zone inevitably leaves behind significant areas of exposed bone that may be subjected to secondary healing problems. The surgeon should make special efforts to minimize tissue trauma. New stenting systems may offer additional benefits.14 Slim curved burs with a flexible axle offered as an adjunct to shaver systems are offered for mucosa-sparing bone work around the frontal sinus neoostium. However, they do not seem to ablate strong bone sufficiently. Technical improvements have been initiated that await separate evaluation. The straight bur serves as the workhorse for enlarged frontal sinusotomy. Its range of action is restricted especially in the anterior direction, however. Maximum enlargement of the neoostium applying the straight bur is possible at the expense of major mucosal tissue trauma and of circumscribed destructions of the external frontonasal skeleton. Maximizing the drill out in type II neoostia may improve the mediolateral dimensions of the neoostium. The increased damage seems to be justified in narrow-spaced anatomy only. Anticipating postoperative wound healing problems in these cases, however, the surgeon may be advised to select alternatively a type III access from the start. A significant mucosa-preserving enlargement of a frontal sinus neoostium type II according to Draf may be accomplished by complementary use of the drill of Blokmanis7 in cases in which generous dimensions of local anatomy are available. The special gain in access is achieved essentially at the expense of anterior parts of the bony neoostium.
HOSEMANN et al 191
The presented experimental technique of multiplying microanatomy of the frontonasal transition zone does not only serve for comparative evaluation of instruments, but may also be suitable for teaching frontal sinusotomy. Comparison of a view from top and below on the detached acrylic specimen at the end of a surgical exercise may provide valuable information. We express our thanks to Prof. Dr. Dr. K.-H. Wrobel, Head of the Department of Anatomy at the University of Regensburg, Regensburg, Germany, for making several anatomical specimens available for our experiments. REFERENCES 1. Hosemann W, Weber RK, Keerl RE, et al. Minimally invasive endonasal sinus surgery. Stuttgart and New York: Thieme; 2000. 2. Becker DG, Moore D, Lindsey WH, et al. Modified transnasal endoscopic Lothrop procedure: further considerations. Laryngoscope 1995;105:1161-6. 3. Close LG, Lee NK, Leach JL, et al. Endoscopic resection of the intranasal frontal sinus floor. Ann Otol Rhinol Laryngol 1994; 103:352-8. 4. Draf W. Endonasal micro-endoscopic frontal sinus surgery: the Fulda concept. Op Tech Otolaryngol Head Neck Surg 1991;2: 234-240. 5. May M, Schaitkin B. Frontal sinus surgery: endonasal drainage instead of an external osteoplastic approach. Op Tech Otolaryngol Head Neck Surg 1995;6:184-92. 6. Hosemann W, Groß R, Go¨ de U, et al. Clinical anatomy of the nasal process of the frontal bone (‘spina nasalis interna’). Otolaryngol Head Neck Surg 2001;125:60-5. 7. Blokmanis A. A new drill for frontal sinus surgery. Laryngoscope 2000;110:168-70. 8. Schaefer SD, Close LG. Endoscopic management of frontal sinus disease. Laryngoscope 1990;100:155-60. 9. Neel HB, McDonald TJ, Facer GW. Modified Lynch procedure for chronic frontal sinus disease: rationale, technique, and longterm results. Laryngoscope 1989;99:885-95. 10. Gross CW, Gross WE, Becker DG. Modified transnasal endoscopic Lothrop procedure: frontal drillout. Op Tech Otolaryngol Head Neck Surg 1995;6:193-200. 11. Halle M. Externe oder interne Operation der Nebenho¨ hleneiterungen [External vs. internal surgical access for paranasal sinusitis]. Berl Klin Wochenschr 1906;43:1369-72 , 1404-7. 12. Gross CW, Zachmann GC, Becker DG, et al. Follow-up of University of Virginia experience with the modified Lothrop procedure. Am J Rhinol 1997;11:49-54. 13. Weber R, Draf W, Keerl R, et al. Langzeitergebnisse nach endonasaler Stirnho¨ hlenchirurgie [Long-term results of endonasal frontal sinus surgery]. HNO 1996;44:503-9. 14. Hosemann W, Schindler E, Wiegrebe E, et al. Innovative frontal sinus stent acting as a local drug releasing system. Eur Arch Otorhinolaryngol 2003;260:131-4.
MD, PHD,
DANIELA HERZOG,
MD,
ACHIM G. BEULE,
OBJECTIVE: Endonasal extended frontal sinusotomy is needed in rare cases of therapy-resistant chronic frontal sinusitis. Several types of burs have been invented to ablate strong bone in the frontal sinus access but nevertheless surgical results seem to differ significantly. The benefits and shortcomings of different burs are subjected to a comparative evaluation. STUDY DESIGN: Five cadaver specimens were duplicated by means of dental molding and casting techniques to provide identical microanatomy for comparative studies on frontal sinusotomy. Different burs (conventional straight bur, right-angled bur according to Blokmanis, and curved frontal sinus bur) were applied to create a type IIb frontal sinusotomy according to Draf in microanatomical replicas. The geometry of the frontonasal neoostium was measured and its dimensions were contrasted to the collateral damage. Bone ablation was calculated by repeated weighting and the area of damaged mucosa was quantified using a 3D analyzing system. RESULTS: A frontal sinus neoostium measuring 9 ⴛ 10 mm on average was created by type IIb frontal sinusotomy according to Draf. The complementary use of an angled bur showed some specific improvements that applied best to spacious anatomic specimens. Those specimens subjected to an extensive use of the straight drill revealed significant collateral damage forming a contrast to minor enlargement of the neoostium. The curved frontal si-
From the Department of Otorhinolaryngology, Head and Neck Surgery, University of Greifswald, Greifswald (Drs Hosemann, Beule, and Kaftan); the Department of Otorhinolaryngology, University of Regensburg, Regensburg (Dr Herzog); and the Department for Lasertechnology in Medicine, University of Ulm, Ulm (Dr Herzog). There is no financial relationship of any of the authors with the manufacturers of any of the materials subjected to evaluation. There are no other (subtle) conflict of interests. Reprint requests: Werner Hosemann, MD, Head of the Department of Otorhinolaryngology–Head and Neck Surgery, University of Greifswald, Walther Rathenau Str. 43-45, D-17487 Greifswald, Germany; e-mail, [email protected]. 0194-5998/$30.00 Copyright © 2004 by the American Academy of Otolaryngology–Head and Neck Surgery Foundation, Inc. doi:10.1016/j.otohns.2004.02.016
MD,
and HOLGER KAFTAN,
MD,
Greifswald, Regensburg,
nus bur showed considerable technical insufficiencies. CONCLUSIONS: Judicious use of the straight drill is recommended for those rare cases of therapy-resistant frontal sinusitis treated by an extended type of frontal sinusotomy. New technical refinements of the curved frontal sinus burs should be subjected to repeated evaluation. (Otolaryngol Head Neck Surg 2004;131:187-91.)
E
ndoscopic endonasal surgery has gained wide acceptance for treatment of therapy-resistant chronic paranasal sinusitis. Irrespective to significant differences in the detailed operative strategy propagated by various rhinological schools, most surgeons strive for optimizing ventilation and drainage of the dependent paranasal sinuses using special instruments designed for microsurgery.1 The frontal sinus represents one of the few anatomical areas left in which the microsurgical concepts mentioned are subjected to an ongoing and controversial discussion. Common therapy-resistant frontal sinusitis can be treated in the vast majority of cases with surgery that is directed exclusively to correction of the primary anatomic key areas of the anterior ethmoid. However, rare cases of chronic frontal sinusitis require optimization of the anatomy of the frontonasal transition zone itself.2-4 Addressing the diversity of diseases and surgical requirements, some authors have developed a step-wise surgical concept of endonasal frontal sinus surgery: Draf4 has defined 3 different types of interventions ranging from mere operative exposure of the frontal sinus ostium to an extended endonasal “median drainage”. May and Schaitkin5 have adopted this classification and added some refinements. Any major surgery on the frontal sinus access must take into account the local microanatomy,6 especially of the superior nasal spine revealing strong bone of up to 1 cm3. The necessary ablation of comparatively compact bone may pose major problems for the application of delicate microsurgical instruments. In addressing this fact, surgeons have used different types of burs to ablate strong bone and to enlarge the operative access to the frontal sinus. However, personal experience has shown that even the largest frontal sinus neoostium may close by secondary scaring as a result of widespread areas of 187
188 HOSEMANN et al
Otolaryngology– Head and Neck Surgery September 2004
traumatized tissue. In addition to the individual predisposition to increased reparative inflammation and scarification, the detailed operative strategy and the instrumental technique seem to be criteria for success. These facts and speculations motivated us to start a comparative evaluation of burs based on exact measurements. Setting this goal, we developed an anatomic model that offered identical microanatomy to repeated surgical interventions. MATERIAL AND METHODS Five human sagittally split cadaver specimens revealing the one-sided paranasal sinus system were provided by the Department of Anatomy, University of Regensburg, Germany. Defined differences in the spacial dimension of microanatomy of the frontonasal transition zone served as selection criteria for the specimens. To ensure exact comparison of different manipulations applied subsequently to identical microanatomic specimens, the key area of the cadavers needed to be duplicated. The bony frontonasal transition zone containing inferior parts of the frontal sinus together with the medial supraorbital rim, the root of the nose, the anterior ethmoid, and the lamina papyracea was excised in a single piece using an oscillating saw. Applying dental molding and casting techniques (impression compound: vinyl polysiloxane; casting material: polymethylmethacrylate) on the five resected pieces of bone, 5 ⫻ 9 detailed duplicates of the anatomic frontonasal transition zone were gathered (Fig 1). Any irregularities of the duplicates were removed by hand. Following this, the duplicates were reintroduced into the anatomic specimen one after another. Each duplicate was fixed on the corresponding anatomic specimen with miniplates and screws. Applying this technique, 5 different series of identical anatomic specimens were available for the comparative study of extended frontal sinusotomy using drills. Initially, an anterior ethmoidectomy was performed in each specimen under the microscope (f ⫽ 250 mm) exposing the anterior skull base. Intraoperative view was improved by nasal specula. After this, an enlarged frontal sinusotomy type II according to Draf was performed applying different drills separately or by complementary use. Unfortunately, a sinusotomy type III according to Draf could not be performed because of shortcomings (paramedian cut) of the anatomic specimens. A straight bur was used in every case (n ⫽ 45) (Intra-handpiece, Fischer Co., Freiburg, Germany; bur head 5 mm ⭋). The modified dental drill according to
Fig 1. Parasagittally half split anatomic specimen of the skull with reattached methacrylate specimen (encircled). Insert: Series of duplicates of the frontonasal transition zone gained from 5 anatomic specimens (a– e).
Blokmanis (No. 52G E 229587, length of handpiece 100 mm, 90° angle distally; KaVo Co., Warthausen, Germany)7 was used complementarily in a second series (n ⫽ 5 ⫻ 2) (Fig 2). A third series of specimens (n ⫽ 5 ⫻ 2) was subjected to a “maximum drill-out” applying the straight drill exclusively but most extensively disregarding circumscribed destructions of the nasal pyramid and the external frontal sinus wall (but preserving the frontal skull base and also the posterior frontal sinus wall by all means). Another small series of experiments was conducted using special frontal sinus burs with a curved shaft and a flexible axle (RAD 55 TM, 55° angle, Xomed, Jacksonville, FL). For certain reasons listed below, this series was restricted to preliminary studies on bony cadavers. The inner surface of the methacrylate sinus duplicates were marked with two different colors preceding surgery on the frontal sinus (color 1: inner surface of sinus frontalis representing frontal sinus mucosa; color 2: surface of the ethmoidal cavity following anterior ethmoidectomy, prior to frontal sinusotomy–representing spared ethmoidal mucosa). Next to frontal sinusotomy, the methacrylate block was detached from the anatomic specimen. The relative mucosal damage could be analyzed by comparison of the surface area revealing loss of color (Fig 3). A series of 5 ⫻ 3 specimens operated on was subjected to an optical 3D-analyzing system based on the micromirror digital stripe projection process (phase shift rapid in vivo measurement of skin [PRIMOS], GFM Company, Berlin-Teltow, Germany). The methacrylate specimens were sagittally split allowing optical measurements to be focused on the new bottle-
Otolaryngology– Head and Neck Surgery Volume 131 Number 3
Fig 2. Curved bur, right-angled bur according to Blokmanis7 and conventional straight bur for extended endonasal frontal sinus surgery.
Fig 3. A) Methacrylate specimen detached from the skull, view from below. The left frontal sinus neoostium (type II according to Draf) is shown after bone work using exclusively the straight bur. 1: ‘Mucosa' of the anterior skull base. 2: wound area due to drilling. 3: intact ‘mucosa' of the posterior frontal sinus wall. B) Same series as in A. This specimen shows the neoostium created by complementary use of the straight bur and also the drill according to Blokmanis. The arrow indicates a bony spur which had been removed. C) Same series as in A and B. This specimen shows the neoostium created by a maximum ‘drill-out' procedure.
neck around the frontal sinus neoostium. The extent of “exposed bone” corresponding to the reduction of the colored areas was digitally analyzed (Fig 4). Ablation of bone was calculated by repeated weighting of the methacrylate blocks having in mind the specific weight of the dry material (1.18 g/ml).
HOSEMANN et al
189
Fig 4. Three sagittally split methylmethacrylate specimen are shown in a digital 3D version (1: straight bur; 2: maximum drill-out; 3: complementary use). The specimens revealing the frontal neoostium are seen obliquely from below (asterisk: ⬘spina nasalis superior’). The picture on the upper right serves for orientation of the detailed digital images only (a ⫽ anterior; p ⫽ posterior; s. front. ⫽ frontal sinus; ext. nose ⫽ external nose).
RESULTS Exclusive application of the straight bur resulted in a frontal sinus neoostium type II of 9.4 (6-10.5) mm length and 10.9 (8-15) mm width (N ⫽ 5). The neoostium showed an individual shape resembling mostly a triangle, circle, or a drop (Fig 3). The specific wound area was 317 (135-590) mm2 (Figs 5 and 6). Analysis of the specimen operated on by view from top and below revealed, in most instances, persisting bony overhangs or edges inside the frontal sinus. The range of action of the bur was restricted especially in the anterior working direction. At the same time, optical control by the microscope was restricted. The complementary use of the drill according to Blokmanis allowed ablation of additional 104 (2-193) mm3 of bone around the superior neoostium mainly anteriorly at the expense of the superior nasal spine. Moreover, bony overhangs and edges located laterally or medially could be removed, both under maximum preservation of the inferior mucosa. The sinusotomy resulted in a wound area of 330 (150-594) mm2. To ensure realization of the same neoostium by exclusive use of conventional straight burs, extensive planar bone ablation would have been needed inferior to the anatomical target area. The length of the frontal sinus neoostium gained 1.3 mm on average, and the width increased by 0.9 mm (N ⫽ 5). On the other hand, introduction of the angled drill constantly caused restrictions of optical control of the operative field. The range of action of the instrument was impaired in cases of narrow-spaced anatomy and generally in the superior and lateral direction.
190 HOSEMANN et al
Fig 5. Average diameter of the frontonasal neo-ostium created with the straight bur, the complementary use of the straight and angled bur (“compl. use”) and the maximum ‘drill-out' procedure (“drill out”).
The maximum drill-out resulted in ablation of an additional 184 (51-340) mm3 bone on average. Most specimens showed destruction of the superior nasal skeleton around the lateral nasofrontal suture. The corresponding wound area increased to 352 (186-578) mm2. However, the neoostium showed some augmentation (length: ⫹ 1.1 mm, width: ⫹ 0.9 mm), too. The ratio of the specific benefits (larger neoostium) and side effects (increased wound area) was best in specimens showing narrow spaced local anatomy. The small series of experiments using the special curved frontal sinus bur had to be stopped prematurely: The flexible axle broke in any case soon after starting major bone work on the superior nasal spine. The producer has been informed and technical improvements are in preparation. Ablating bone around the frontal sinus neoostium with the Blokamnis drill revealed some general inconveniences with respect to handling inside the nose and to the range of view of any telescope. The latter was primarily caused by focal thickening of the bur located at the 90° angle. We made an acrylic duplicate of the bur and simulated different other angulations of the tip of the instrument: a 60°-angled tip showed the most significant benefits with respect of the range of action and also to the simultaneous optical control. DISCUSSION Contemporary endonasal sinus surgery has given rise to distinct extended procedures focussing on the frontal sinus.4,8-10 Any surgical technique must deal with the strong bone of the nasal process of the frontal bone (spina nasalis interna).6 To address this fact, several types of burs have been introduced recently to
Otolaryngology– Head and Neck Surgery September 2004
Fig 6. Wound area created around the frontonasal neoostium by use of different burs (for legends, refer to Fig 5).
ablate this bone. It may be noteworthy to call to attention to the fact that Halle11 had, in 1906, presented a special bur system especially designed for frontal sinusotomy. However, irrespective of impressive dimensions of the frontal sinus neoostia created intraoperatively, the long-term surgical results are sometimes flawed with reactive scaring, leading to a relapse of insufficiency of frontal sinus drainage and ventilation.12,13 As a consequence, surgeons strive to optimize the operative strategy by minimizing tissue trauma. Blokmanis7 introduced a modified dental drill with a 90°-angled tip to work around the corner at the frontal sinus access. Although collateral tissue trauma may be reduced avoiding the linear operative access needed in use of straight burs, the angled instrument shows considerable bulk inside the nose interfering with the endonasal optical control. Several industrial companies have presented slim curved burs with a flexible power transmission (axle) as an alternative choice. The investigations presented herein are based on a first series of experiments evaluating the benefits and shortcomings of burs recommended for extended frontal sinusotomy. We attached great importance to comparative use of instruments in specimens revealing identical anatomy. According to our experiments the contemporary surgical instruments are far from being perfect. Technical insufficiencies mainly affect the curved frontal sinus burs at that time, and in the meantime, announced technical refinements should be subjected to a second evaluation. At the moment, judicious use of the straight drill may be recommended for those rare cases that are in need of major bone work at the frontonasal transition zone. Complementary use of the Blokmanis bur is recommended for cases in which
Otolaryngology– Head and Neck Surgery Volume 131 Number 3
there are generous dimensions of local anatomy because of minimized mucosal trauma, as shown in our data. The presented evaluation may lay the foundation for further technical innovations and serve for the process of continuous improving of the individual operative strategy. CONCLUSION The enlarged frontal sinusotomy type II/III according to Draf4 has become an established type of treatment for special cases of chronic frontal sinusitis. Local anatomy exhibiting areas of strong bone calls for the application of burs. The use of burs at the frontoethmoidal transition zone inevitably leaves behind significant areas of exposed bone that may be subjected to secondary healing problems. The surgeon should make special efforts to minimize tissue trauma. New stenting systems may offer additional benefits.14 Slim curved burs with a flexible axle offered as an adjunct to shaver systems are offered for mucosa-sparing bone work around the frontal sinus neoostium. However, they do not seem to ablate strong bone sufficiently. Technical improvements have been initiated that await separate evaluation. The straight bur serves as the workhorse for enlarged frontal sinusotomy. Its range of action is restricted especially in the anterior direction, however. Maximum enlargement of the neoostium applying the straight bur is possible at the expense of major mucosal tissue trauma and of circumscribed destructions of the external frontonasal skeleton. Maximizing the drill out in type II neoostia may improve the mediolateral dimensions of the neoostium. The increased damage seems to be justified in narrow-spaced anatomy only. Anticipating postoperative wound healing problems in these cases, however, the surgeon may be advised to select alternatively a type III access from the start. A significant mucosa-preserving enlargement of a frontal sinus neoostium type II according to Draf may be accomplished by complementary use of the drill of Blokmanis7 in cases in which generous dimensions of local anatomy are available. The special gain in access is achieved essentially at the expense of anterior parts of the bony neoostium.
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The presented experimental technique of multiplying microanatomy of the frontonasal transition zone does not only serve for comparative evaluation of instruments, but may also be suitable for teaching frontal sinusotomy. Comparison of a view from top and below on the detached acrylic specimen at the end of a surgical exercise may provide valuable information. We express our thanks to Prof. Dr. Dr. K.-H. Wrobel, Head of the Department of Anatomy at the University of Regensburg, Regensburg, Germany, for making several anatomical specimens available for our experiments. REFERENCES 1. Hosemann W, Weber RK, Keerl RE, et al. Minimally invasive endonasal sinus surgery. Stuttgart and New York: Thieme; 2000. 2. Becker DG, Moore D, Lindsey WH, et al. Modified transnasal endoscopic Lothrop procedure: further considerations. Laryngoscope 1995;105:1161-6. 3. Close LG, Lee NK, Leach JL, et al. Endoscopic resection of the intranasal frontal sinus floor. Ann Otol Rhinol Laryngol 1994; 103:352-8. 4. Draf W. Endonasal micro-endoscopic frontal sinus surgery: the Fulda concept. Op Tech Otolaryngol Head Neck Surg 1991;2: 234-240. 5. May M, Schaitkin B. Frontal sinus surgery: endonasal drainage instead of an external osteoplastic approach. Op Tech Otolaryngol Head Neck Surg 1995;6:184-92. 6. Hosemann W, Groß R, Go¨ de U, et al. Clinical anatomy of the nasal process of the frontal bone (‘spina nasalis interna’). Otolaryngol Head Neck Surg 2001;125:60-5. 7. Blokmanis A. A new drill for frontal sinus surgery. Laryngoscope 2000;110:168-70. 8. Schaefer SD, Close LG. Endoscopic management of frontal sinus disease. Laryngoscope 1990;100:155-60. 9. Neel HB, McDonald TJ, Facer GW. Modified Lynch procedure for chronic frontal sinus disease: rationale, technique, and longterm results. Laryngoscope 1989;99:885-95. 10. Gross CW, Gross WE, Becker DG. Modified transnasal endoscopic Lothrop procedure: frontal drillout. Op Tech Otolaryngol Head Neck Surg 1995;6:193-200. 11. Halle M. Externe oder interne Operation der Nebenho¨ hleneiterungen [External vs. internal surgical access for paranasal sinusitis]. Berl Klin Wochenschr 1906;43:1369-72 , 1404-7. 12. Gross CW, Zachmann GC, Becker DG, et al. Follow-up of University of Virginia experience with the modified Lothrop procedure. Am J Rhinol 1997;11:49-54. 13. Weber R, Draf W, Keerl R, et al. Langzeitergebnisse nach endonasaler Stirnho¨ hlenchirurgie [Long-term results of endonasal frontal sinus surgery]. HNO 1996;44:503-9. 14. Hosemann W, Schindler E, Wiegrebe E, et al. Innovative frontal sinus stent acting as a local drug releasing system. Eur Arch Otorhinolaryngol 2003;260:131-4.