The Riedel Procedure-An Analysis of 22 Cases

The Riedel procedure is a radical ablative operation devised in 1898 when, in the pre-antibiotic era, acute and chronic frontal sinusitis carried a high morbidity and mortality. Curiously it persists as part of the armamentarium of the sinus surgeon over a century later. Despite all the advances made in modern therapeutics, imaging and instrument technology, a small subset of patients persists with chronic refractory frontal osteomyelitis that has defi ed conventional management. It is the purpose of this paper to report our experience with 22 cases undergoing the Riedel procedure to establish a profi le for those patients with chronic frontal sinusitis who insidiously develop chronic osteomyelitis and ultimately require radical ablative surgery.


Introduction
The Riedel procedure is a radical ablative operation devised in 1898 when, in the pre-antibiotic era, acute and chronic frontal sinusitis carried a high morbidity and mortality.
Curiously it persists as part of the armamentarium of the sinus surgeon over a century later. Despite all the advances made in modern therapeutics, imaging and instrument technology, a small subset of patients persists with chronic refractory frontal osteomyelitis that has defi ed conventional management. It is the purpose of this paper to report our experience with 22 cases undergoing the Riedel procedure to establish a profi le for those patients with chronic frontal sinusitis who insidiously develop chronic osteomyelitis and ultimately require radical ablative surgery.

Materials and Methods
A comprehensive chart review of all patients presenting to the senior authors (W.L. and A.R.) requiring the Riedel procedure was performed. Basic demographic information was recorded.
The entire pre-operative, operative and post-operative course of all patients was reviewed including previous procedures and complications. A comprehensive literature review of frontal osteomyelitis and its management was performed as well.

Discussion
Among the paranasal sinuses, the frontal sinus presents the greatest challenge. It is the sinus most prone to multiple surgical procedures, both endoscopic and external, for a variety of reasons including: 1) maintaining nasofrontal outfl ow patency is limited by the tendency to osteoneogenesis; 2) mucociliary fl ow is from the nasal cavity into the frontal sinus inviting reinfection; 3) anatomically, diploe of the anterior and posterior table invites the development of osteomyelitis, and the diploic veins passing through them may   lead to subperiosteal and intracranial infections; 4) it has the greatest incidence of mucoceles and mucopyoceles, which may indolently produce chronic infection of the surrounding bone; and 5) it has a longer and irregular outfl ow tract narrowed by extramural ethmoid cells.
Consequently, despite the increased safety and outcome results of endoscopic frontal sinus surgery enhanced by navigational guidance and improved instrumentation, failures occur. They result principally from outfl ow tract stenosis, but also from extrasinal extension, mucocele formation and refractory infections resulting in osteomyelitis.
Intractable frontal sinusitis following medical management and endoscopic sinusotomies may require an open approach often with sinus obliteration. Frontal sinus obliteration has been performed in several forms; the purpose being the elimination of the air containing space and its secretory mucosa and isolating it from the remaining paranasal sinus complex. The earliest approach was the Riedel procedure in which an osteomyelitic anterior table was removed and the forehead skin permitted to collapse against the posterior wall of the sinus. The osteoplastic fl ap created a hinged osteoperiosteal vascularized fl ap of the anterior table, which permitted entry into the sinus and exenteration of its contents in a non-deforming fashion. Obliteration of the cavity was achieved by the implantation of autogenous fat. Alternatively, auto-obliteration by osteoneogenesis was permitted; however, this method has proven to be unreliable. At the time of the procedure, small areas of nonviable bone can be removed without signifi cant deformity of the forehead, but it carries the risk of residual foci of indolent osteomyelitis remaining, which become active over the passage of time. Finally, cranialization can produce sinus obliteration by removing the posterior table of the frontal sinus permitting herniation of the brain and dura to prolapse against the anterior table. This is most commonly performed through a frontal craniotomy for trauma or after tumor removal. The Riedel procedure was the most radical and deforming and so was rapidly replaced by the other more conservative operations. However, it has persisted for management of chronic refractory osteomyelitis of the frontal bone, which paradoxically may arise from conservative medical and surgical treatment. Antibiotics frequently mask latent infection and both endonasal and external procedures may fail to eliminate foci of osteomyelitic bone or persistent pyoceles.

Frontal osteomyelitis
The pathogenesis of frontal osteomyelitis from chronic frontal sinusitis has been elucidated by several investigators.
Acute or chronic pyogenic infections of the frontal sinus may extend to the surrounding bone by septic retrograde thrombophlebitis of the valveless diploic veins leading to the involvement of the medullary and cortical portions of the cranium and producing a subperiosteal or intracranial abscess.
Historically, Sir Percival Pott in 1760 was the fi rst to recognize osteomyelitis of the frontal bone as a distinct entity and the term "Pott's puffy tumor" became an eponym for the external pericranial or subgaleal abscess presenting as a tender swelling of the forehead [1]. He initially reported it occurring following trauma and, later in 1775, secondary to frontal sinusitis. The etiology in the great majority of the cases is from frontal sinusitis but it has been reported following penetrating and blunt forehead trauma, cocaine use, frontal reconstruction, insect bites and dental sepsis.
The majority of the cases of Pott's puffy tumor are in the pediatric population with a strong male preponderance in all age groups [1]. The patients generally present with headache and fever along with forehead swelling. As the majority of cases are sinogenic in origin, a history and signs and symptoms of acute or chronic sinusitis are present. Pott's puffy tumor associated with acute and chronic frontal osteomyelitis is often accompanied by intracranial complications, with reported rates as high as 60-100% [3][4][5].
In 2011, Ketenci et al., found 62 cases of Pott's puffy tumor reported in the English literature in the past 40 years, only 11 of which were adults [6]. They added 6 cases (4 adults), 3 with a frontal lobe abscess, which requited craniotomy and craniectomy, 1 of which died. One patient had cerebritis and 2 had an orbital abscess. In 2012, in a systematic review of Pott's puffy tumor by Nisa et al. extending over a 60 year period (1950-2010), which included the European literature, 141 cases were found, again principally in adolescents and young males [7]. In this group almost three-quarters had intracranial complications. This is especially true in pediatric patients.
Blumfi eld and Misra reported 5 adolescents presenting with Pott's puffy tumor; 4 had epidural abscesses and 2 had dural sinus thrombosis [8]. In the 7 cases of Bambakidis and Cohen (2001), ages ranged from 11-18 years, there were 5 epidural abscesses, 4 subdural abscesses and 1 brain abscess [9]. Younis et al., attributed the greater prevalence of intracranial and orbital complications in this age group to the increased number of diploic veins in children [10]. Akimaya et al., on review of the English literature for the period 1990-2011 specifi cally for Pott's puffy tumor in adults found 27 cases to which they added 5 cases [11]. The mean age for the group was 45.6 years. Intracranial complications were present in 29%.
Orbital complications also occur frequently with Pott's puffy tumor and may be the presenting sign. The pathogenesis is also believed to be retrograde septic thrombophlebitis from valveless veins. In the 5 pediatric cases of Pott's puffy tumor reported by Blumfi eld and Misra, all patients with orbital involvement had intracranial involvement [8]. The systematic review of 141 reported cases of Pott's puffy tumor by Nisa et al., revealed that 42 (29%) cases had orbital complications [7].

Operative procedure
The procedure can be performed through an eyebrow (gullwing), mid brow, or coronal incision, which is determined by the hairline in males, previous incisions, the extent of the disease process or the presence of a fi stula (Figures 3,4) . • Any dural dehiscences or lacerations are repaired by primary suturing or fascial grafting.
• Cultures are taken from the operative site and the wound is copiously irrigated.
• The supraorbital ridges are exposed and reduced suffi ciently to permit collapse of the forehead soft tissues into the defect and to contact the posterior table and any exposed dura to produce complete obliteration.
The supraorbital and supratrochlear nerves are preserved if at all possible. Implicit in this is some degree of deformity, the severity of which depends of the prominence of the supraorbital ridges.
• A Penrose drain is inserted and the wound is closed in layers.
• With a signifi cant degree of deformity of the forehead, a cranioplasty can be performed, generally with an alloplastic material (acrylic) or autogenous bone grafts, after an adequate disease free interval both clinically and on radionuclide evaluation.

Treatment
Acute frontal osteomyelitis requires drainage of the subperiosteal collection along with endoscopic or external drainage (trephine) of the frontal sinus. This is always performed in conjunction with prolonged IV antibiotic therapy. Imaging of the brain and orbits is essential because of the high incidence of intracranial and orbital complications associated with Pott's puffy tumor which may also require neurosurgical and ophthalmologic intervention.
In the great majority of cases of acute and early chronic

Conclusion
1. Chronic frontal osteomyelitis is an indolent process that develops over many years in immunocompetent patients.

2.
The natural history is generally of multiple progressively more invasive surgical procedures and numerous courses of antibiotic therapy.