Learning Objectives: 1. To share the long term results of our bony obliteration tympanoplasty technique in primary and revision cholesteatoma cases (BOT), and in the reconstruction of unstable CWD cavities (CR-BOT). 2. To illustrate the advantages of an intact bony canal wall over CWD procedures. 3. To discuss the prerequisites for long term safety when using the BOT. 4. To advocate the use of the non-EP DW MRI sequence for the follow-up of cholesteatoma cases.

Introduction: Since the last 15 years we have used the Canal Wall Up Bony Obliteration Technique (CWU-BOT) in 87% of our cholesteatoma cases. The BOT preserves the bony CW and closes the tympano-attical barrier and posterior tympanotomy with sculpted cortical bone. After removal of all diseased soft tissue and bone, the antro-attico-mastoid space is completely obliterated with healthy bone pâté. The middle ear is reconstructed using a tympano-ossicular allograft, including the malleus handle, which acts as the anchor point for columellar reconstruction to the stapes with a remodelled allograft incus or malleus.

Methods: We report on the long term outcome of 2 series of consecutive cases operated on by a single surgeon (EO). The first series comprises 34 paediatric cholesteatoma cases, followed up for at least 5 years without drop-outs. Control for residual disease was done by non-EP DW MRI (100%) at 1 and 5 years post-op. Control for recurrent disease was done by yearly micro-otoscopic evaluation. We compare the outcome with a similar series, previously operated by the same surgeon, using identical dissection and reconstruction techniques, however without bony obliteration. As such, we evaluate the contribution of the BOT factor to long term safety (prevention of recurrence).

The second series comprised 50 unstable CWD cavities surgically restored by means of the BOT, and followed up for a mean of more than 8 years. Control for residual disease was done by a combination of staging (the early cases) and non-EP DW MRI (76%). Control for recurrent disease was done by yearly micro-otoscopic evaluation.

Results: We report on recurrence rate, residual rate and anatomical/hygienic outcome.

In the paediatric series the 5 year recurrence rate was 5.8% (2 cases). The residual rate was 2.9% (1 case). At 5 years post-op all patients reported 0% otorrhea. The ears were waterproof in 100%. The operation rate (re-operation risk) to achieve this final result was 1.47. This re-operation rate included the revisions for the 2 residual cholesteatoma cases and for the single recurrence case, as well as secundary closure of 3 reperforations and some secundary Meatoplasty cases. The comparison with the non-BOT series showed a vast improvement of the recurrence rate, from 19.4% to 2.9%, as well as an improvement of the residual rate (from 24.3% to 5.8%).

In the cavity BOT-reconstruction series the recurrence rate was 2% (1 case). The residual rate was 2% (1 case). The long term final post-op outcome showed a dry and self-cleaning ear in 94% of the cases.

In both series there was no bone conduction loss and no facial paresis or palsy.

Conclusion: The CWU-BOT combines the advantages and avoids the disadvantages of both the CWU and CWD technique, reconciling the long term safety aim with excellent anatomical/hygienic outcome. The long term recurrence rates have dropped significantly in our series, as well as the residual rates. The vast majority of the patients report a dry, selfcleaning and water-resistant ear in the long term. The use of non-EP DW MRI as a screening tool for residual disease has obviated the need for routine second stage surgery and provides long term safety.

For us this solves the old debate of CWU versus CWD techniques in cholesteatoma management. Since 1997 we have completely abandoned the use of CWD techniques for the management of cholesteatoma. The suppression of the paratympanic cell system by complete bony obliteration seems to favourably influence the behaviour of the biologically unstable middle ear and its mucosal lining. The careful reconstruction of a solid bony partition between the mastoid and attic space on the one hand and the ear canal and tympanic cavity on the other hand seems to limit the effect of the pathological biological behaviour of the canal skin.