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Journal of the Anatomical Society of India

Accessory Maxillary Ostia: Topography and Clinical Application

Author(s): Kuma R, H; Choudhr Y, R; Kaka R. S.

Vol. 50, No. 1 (2001-01 - 2001-06)

Department of Anatomy , Lady Hardinge Medical College, New Delhi - INDIA

For Reprints, request from the author first.

Abstract Thirty half-heads from fifteen adult Indian cadavers were dissected to study the incidence, location and side of secondary maxillary ostia (AMO). AMO were present in 9 (30%) half-heads being located in the anterior nasal fontanelle (ANF) in 6 (66.7% ) , in the posterior nasal fontanelle (PNF) in 2 (22.2%) and at the hiatus semilunaris (HS) in 1 ( 1 1.1%). It was twice as frequently present on the right side as com p ared to the le f t. Five (55.6%) sides had single whereas 4 (44.4%) had twin AMO. T wo twin AMO were seen in the ANF & one each in PNF & HS. Seven of these were found unilaterally & except 2 were bilaterally present. All were present in the male cadavers except for a single AMO in the female half-head. The radiologists and endoscopic rhinologists must have detailed knowledge of inconsis tent location of these apertures and intricate topography of the middle meatus in any interventional endonasal endoscopic maxillary sinus surgery.

Key words : Accessory maxillary ostia/ostium (AMO), Antorior nasal fontanelle (ANF). Posterior nasal fontanelle (PNF), Hiatus semilunaris (HS).

Introduction :

Evolution is a gradual process by which man attained erect posture whereby the principal or main maxillary ostium (PMO) came to be located at a higher level consequentl y , drainage was no longer due to gravit y . Maxillary sinusitis is therefore the demerited gift of erect posture. "No-thanks " to this nondependent drainage. This factor along with the impendence to mucociliary action of the lining mucosa is the leading cause of this condition which results in obstruction of the ostium which opens at the hiatus semilunaris (HS). The obstruction may however be due to anatomic variation or anomaly in the vicinity of the PMO, a fact first recognised well over a century ago by Zuckerkandle (1870).

There has been resurgence of interest among otorhinologists in the morphological features of the lateral wall of nasal cavity with the advent of endonasal endoscopic sinus surger y , therefore the writings of anatomists have been reviewed for better understanding of complexities of this region. Functional endoscopic techniques being minimally traumatic have become increasingly popular in diagnostic and therapeutic aspects of nasal and sinus problems. It is thus imperative to study the topography of these apertures. Interestingly Hischamann in 1901 performed endoscopy using a cystoscope which was a forerunner of the modern day nasal endoscope. The area termed as "ostiomeatal complex" of the middle meatus has not only the PMO opening in the HS but also of-times, other "holes " or accessory maxillary ostia.ostium (AMO) in latin is termed as ostium maxillare ascessorium. AMO is invariably solitary but occasionally multiple, either congenital or secondary to disease process. A possible mechanism of formation of accessory ostia is obstruction of the main ostium by maxillary sinusitis or due to anatomic and pathologic factors in the middle meatus resulting in the rupture of membranous areas known as fontanelle ( Levine et al 1993). The word fontanelle was introduced by Zuckerkandal (187 0 ) to describe certain regions in the middle meatus located below the uncinate process and above the inferior turbinate, covered by nasal mucous membrane medially and mucosa of maxillary sinus laterally with connective tissue sandwiched between the two. These are thus deficient of bony component and are weak areas of the middle meatus vulnerable to perforation. These according to their location in relation to uncinate process are anterior nasal fontanelle (ANF) and posterior nasal fontanelle (PNF) (Fig.1). The ANF lies between the inferior edge of uncinate process and attached margin of the inferior turbinate while the PNF lies posterosuperior to the former ( Levine et al, 1993).

Materials and Methods :

Thirty half-heads of Indian origin from fifteen cadavers, ten males and five females cut in midsagittal plane which had been used for student dissection in the Department of Anatomy, Lady Hardinge Medical college were studied. The middle turbinate was cut or reflected along its attached margin to note the numbe r, side, and topography of AMO to the surrounding structures. The diameter of the AMO were measured using a divider and scale along their long axis in those that were oval.

The floor of the orbit which forms the roof of the maxillary sinus was broken and light was introduced through it, to visualize the AMO and the fontanelles. The site of each ostium was noted in reference to the areas of bony dehiscence i.e. their presence in the ANF or PNF or HS.

Observations :

AMO were present in 9 out of the 30 half heads studied. In 6 half-heads these were present on the right side while in 3 they were on the left side. AMO were round or oval in shape and varied in size from being 0.5mm to 3mm (Fig 2 & 3). Out of the 9 half-heads presenting this feature, 5 were single whereas 4 were twin or double.

In two of these half-heads (right side), twin AMO were seen, lying in the ANF (Fig.2) while the twin AMO lying in the PNF (Fig.3) and HS (Fig.4) were in one half-head each, belonging to right and le ft side respectivel y. Both twin AMO located in the ANF & HS were placed in horizontal plane one behind the othe r, whereas those in the PNF were vertically placed one above the other . Each of a pair were of unequal size. All AMO were found in the male, except a single ostium in the ANF of a female cadaver on the right side.

Seven AMO were unilaterally present on the right or the left side, while one cadaver had this feature on both sides i.e. present bilaterally in the ANF.

On transillumination from the orbital aspect of the maxilla the ostia were seen lit against the dark background when seen from the medial side i.e. lateral nasal wall (Fig. 5)


N=9 (30%)
Anterior Nasal
(n=6) (66.7%)
4 4 4 2 (Rt.)
Posterior Nasal
1 (n=2) (22.2%)
2 - 1 1 (Rt.)
Hiatus Semilunaris
(n=1) ( 11.1%)
- 1 - (1 Lt.)


1. May et al (1990) PNF 0
2. Kennedy and
Zinreich (1991)
Not specified 15 Endoscopic
3. Van Alyea (1936) Not specified 23 Cadavers
4. Lang & Wurzburg (1991) Not specified 28 Cadavers
5. Myerson (1932) Not specified 31 Cadavers
6. Schae ffer (1920) ANF or PNF 43 Cadavers
7. Stammberger & Kennedy (1995) ANF or PNF 4.5
General population
8. Present study ANF or PNF
30 Cadavers or HS

Discussion :

Clearance of mucous from the maxillary antrum solely depends upon the mucociliary action of its lining mucosa. Normally the synchronous ciliary beat is towards the PMO, located in the hiatus semilunaris. The AMO when present whether as a consequence of chronic maxillary sinusitis or as a congeni tal entit y, is more advan tageously placed than the natural aperture. Little drainage that occurs in such cases is due to gravi tational e ffect as these ostia do not have active mucociliary clearance ( Kennedy and Zinreich 1991).


The incidence of presence and location of AMO varies according to di fferent workers ( Table II). In studies conducted on cadavers and endoscopicall y , the incidence of AMO has been recorded to range from 0% to 43%. It is recorded as 10% by May et al (1990) 15% by Kennedy and Zinreich (1991), 23% by Van Alyea (1936), 43% by Schaeffer (1920). Stammberger and Kennedy (1995) noted the "natural" incidence of AMO to the order of 4-5% in the normal healthy population, this incidence increases to 25% in patients of chronic inflammatory conditions of nose and sinuses. In the present study the AMO were found in 30% of half heads which corroborates to the incidence reported by Myerson (1932). Though most authors have not specified the location of the AMO with reference to the fontanelle, Schaeffe r, (1920) and S t ammberger and Kennedy (1995) reported their presence either in the ANF or PNF as found in the present stud y. May et al (1990) however found their presence restricted to the PNF posteroinferior to natural ostia. We however found that besides the font anelles the AMO can also be sited in the HS, a finding similar to that of Rice and Scheaffer (1993) and Frank et al (1993 ) .

In our study of thirty half-heads we found AMO most frequently at the ANF (66.6%), rest were present in the PNF (22.2%) and HS (11.1%). Out of the 9 half-heads with this finding twin AMO were observed in 4 (44.4%). However Scheaffer (1920) reported the AMO to number between 1 to 3. This is not a common occurance and hence there is paucity or literature regarding the multiple openings.

The twins openings at the HS could be interpreted as triple PMO as opined by Schaeffer(1953) who recorded duplicate PMO and does not favour calling one of these accessory to the main. Rice and Schaeffer (1993) however dispute this and term all extra openings other than a single PMO as AMO irrespective of their location.

Clinical Application

On gross study, V an Alyea (1936) found that the PMO was not approachable due to variable configuration of uncinate process or bulla ethmoidalis or size of the ostia in 20% of specimens. The surgeons may then fail to cannulate it. Clinically the AMO may be utilized in such cases by the endoscopic sinus surgeon to irrigate the maxillary sinus ( Levine et al 1993). Apart from the ostia the fontanelles may be used to create alternative passage which re-establishes ventilation and drainage during therapy of maxillary sinusitis.

Recognition of the maxillary ostia is tedious while performing endoscopic procedures which accounts for a high rate of orbital complications for a novice performing surgery in this region. It is therefore imperative to know the landmarks in this regions which may be obliterated by disease.

On endoscopy the mucociliary flow of secretions is frequently found moving through the AMO into the maxillary sinus and then leaving through the PMO. This may be one possible mechanism by which pathogens make their re-entry into maxillary sinus.

Radiologist should be aware of this entity as it can appear as communication between the maxillary sinus and nasal cavity on sinus imaging examinations. In case these are " stacked" one above the other as one seen in the PNF in our case two openings may be visualized in the coronal C T .

References :

  1. Frank, G; W aren, M.K; Schae f fe r , S.D. (1993): Otolaryngologic clinics of Nort h America. Vol 26. pp 509-515.
  2. Hirschmann (1901): Ober endoskople der nase and deren nebenhohlen; eine neue untersuchungsmethod. Archives Laryngology Rhinology Vol 14: p 105.
  3. Kenned y , D. W ; Zinteich, J. : Otolaryngolog y , Head and Neck, V ol III. W .B. Saunders Com p an y , pp. 1861-1871. (1991)
  4. Land, J. W urzberg : Paranasal sinuses; anatomical considerations, S pringer V erlag. pp 3-17. (1991)
  5. Levine, H.L; Mark, M; Rontal, M; Rontal, E; : Complex Anatomy of latral nasal wall simplified for endoscopic surgeon. Endoscopic sinus surger y , thieme Medical Publishers, New York pp. 1-28. (1993).
  6. Ma y , M; Scbol, S.M; Korzee, J. (1990) : Location of maxillary Os and its importance to endscopic sinus surgeon. Laryngoscope. Vol. 10 0 , pp. 1037-1042.
  7. Myerson (1932) : The natural orifice of maxillary sinus, Anatomical studies. Archives of Otolaryngology, Vol. 5 pp. 80-91.
  8. Rice, H.D; Schea f fe r, S.D: Endoscopic Paransal sinus surger y , 2nd ed, Ravan Press: pp. 3-46. (1993)
  9. Schea f fer J. P . Paranasal sinuses, nasolacrimal p assageways and olfactory organ in Man. Philadelphia. Blakiston. (1920)
  10. Schea f fer J.P: Morris Human Anatom y , 1 1th Ed. Mc Graw Hill Book Comp an y , Ne w Y ork, pp. 1430-1446. (1953).
  11. V an Alyea, O.E. (1936) : The Ostium Maxillare anatomic study of it s surgical accessibilit y, Archives of Otolaryngology, Vol. 24, pp. 553-559.
  12. Zuckerkandle: (Quoted by Stammberger et al (1990) Functional endoscopic sinus surger y . B.C. Decker , Philadelphia, pp. 9-67, 170-182. (1870)

Fig 1: Location of AMO at hiatus semilunaris (HS.) anterior nasal fontanelle (ANF) and posterior nasal fontanelle (PNF . )

Fig 1

Fig 2 . Twin AMO in the ANF located one behind the other . The smaller anterior ostium is directed upwards and backwards.

Fig 2

Fig 3. Twin AMO in the PNF one above the other. The PMO is covered by the uncinate process.

Fig 3

Fig 4. Twin AMO in the HS along with an upwardly directed large PMO in the anterior half of HS. The upper part of uncinate process has been removed to display the PMO.

Fig 4

Fig 5. Same half-head (Fig. 4) T ransilluminated to visualise the twin AMO.

Fig 5
J. Anat. Soc. India 50(1) 3-5
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