By V. Elber. Coastal Carolina University.
In addition 100 mg penegra sale, comorbidities such as diabetes best penegra 100 mg, chronic renal failure penegra 100mg on-line, and postoperative nasal endoscopy with debridement is impera- chronic steroid use may prolong healing of the sinonasal tive for enhancing sinonasal healing and preventing sinonasal cavity and skull base buy 100 mg penegra visa. Proper medical and surgical management of terials may prolong postoperative healing compared with the sinonasal cavity provides the best opportunity for rapid the use of a vascularized pedicled fap (Fig. I Perioperative Management The vast majority of patients after endoscopic pituitary and skull base surgery are admitted to the intensive care unit in the immediate postoperative period for observation. Telfa nasal packs are placed anteriorly in the nasal cavities to wick blood in the immediate postoperative period. The head of the bed is kept A elevated, usually no more than 30 degrees from the supine position. A face tent provides mist humidifcation to the sinonasal cavity and decreases patient discomfort. Delivery of oxygen through a nasal cannula has the potential of causing a tension pneumocephalus, a seri- ous and potentially devastating complication of endonasal, intracranial approaches (Fig. Nasal sprays and irriga- tion should be avoided during the frst postoperative week because they may cause bleeding or displace materials used for skull base reconstruction. All patients are given perioperative antibiotics for 24 to 48 hours after surgery. A series of 90 patients undergo- ing endoscopic skull base surgery who received a single dose of perioperative antibiotics yielded no cases of intra- cranial infections or meningitis. The potential ramifcations of infection in these pa- B tients include meningitis, intracranial abscesses, and vascu- Fig. Patients are also I Postoperative Management instructed to avoid hot showers to prevent vasodilation of intranasal vessels and subsequent bleeding. Patients are Postoperative sinonasal care begins with the otolaryngolo- usually discharged with a prescription for an antibiotic and gist, approximately 1 week after discharge from the hospital. This includes removing crusting, 31 Managing Postoperative Sinusitis 323 old blood, mucoid secretions, and breakdown products from over, although rare, depending on the extent of intracranial hemostatic agents and tissue. Scabs are never aggressively debrided from the branches of the sphenopalatine artery. However, if present, they should be ethmoidal arteries necessitates immediate evaluation of the treated with local wound care and topical antibiotic oint- eye to rule out a retrobulbar hematoma. Patients are also placed on a gentamicin nasal spray rare event of a sentinel bleed suggestive of bleeding from (80 mg in 1000 mL of saline) three times a day for 4 weeks the carotid artery, immediate intranasal packing and inser- to decrease mucosal edema and bacterial colony count, as tion of a Foley balloon should be initiated to tamponade the well as to improve nasal mucociliary function and nasal hy- bleed. An unstable patient should be nasal irrigation has been studied and appears to be below emergently taken to the operating room for carotid ligation. Crusting Follow-up visits consist of postoperative sinonasal debride- ments, lysis of synechia, and examination of the skull base. A Crusting almost always occurs after endoscopic pituitary cranial nerve exam is performed in addition to evaluate for surgery. Crusting may be more extensive in ex- frequent and lengthier postoperative follow-up visits to re- tended skull base procedures for larger pituitary adenomas, move crusting and ensure good mucosal healing. Postoperative debridement after en- doscopic skull base surgery is important to improve mucosal healing, encourage mucociliary function, decrease synechia I Management of Sinonasal Complications formation, prevent sinonasal obstruction, avoid acute or chronic rhinosinusitis, and improve patient comfort. The Bleeding Postoperative bleeding rarely requires intervention if me- ticulous hemostasis is maintained intraoperatively. In our series of pituitary and anterior skull base cases, there was a 2% incidence of postoperative epistaxis. Minor postoperative bleeding is expected and usually does not require any treat- ment other than mist humidifcation and frequent changing of the nasal drip pad. In rare cases, a moderate amount of bleeding may be controlled with placement of a hemostatic matrix or intranasal packing. Endoscopic visualization of the origin is recommended for expedient hemostatic control and to avoid jeopardizing the skull base reconstruction. In some circumstances, if the patient is cooperative, local anes- thesia and electrocautery can be applied under endoscopic guidance to control the bleeding. If the bleeding is brisk, located deeper in the nasal cavity, and difcult to identify despite endoscopic visualization, controlling the hemor- rhage in the operating room is preferable. This is particularly important in the immediate postoperative period, given the risk of displacing the skull base reconstruction materials if a Fig. A randomized, blinded panied by purulent secretions may occur, resulting in acute clinical trial evaluating postoperative debridement in pa- rhinosinusitis. In general, acute rhinosinusitis is defned as tients undergoing endoscopic sinus surgery was published symptomatic infammation of the nose and paranasal si- in 2006. At 12 Medical management with antibiotics is well supported weeks postoperatively, the debridement group experienced in the literature to eradicate bacteria from the sinuses, has- a slightly longer duration of pain (2. Overaggressive debridement especially at the skull mean symptom scores in nonsevere acute rhinosinusitis. However, topical therapy, including nasal sprays and irriga- Patients are encouraged to maintain good nasal hygiene tion, must be used cautiously in the immediate postopera- with the use of nasal sprays, irrigation, moisturization of the tive period to avoid disturbing the skull base reconstruction, nose, and mist humidifcation. Initial experience suggests specifcally hastening the dissolution of dural and tissue that these remedies should be used a week after surgery, sealants. Adequate assessment of pain and appropriate approximately, after the initial postoperative visit with the treatment with analgesics must also be initiated. Evidence for deferring antibiotics in patients with acute bacterial rhinosinusitis with mild symptoms (temperature <100°F) exists in the literature. This strategy is based pri- Synechia marily on comparing antibiotics versus placebo for acute Postoperative synechia may occur in the sinonasal cavity af- rhinosinusitis, showing spontaneous improvement in 62 to ter endoscopic pituitary and skull base surgery, despite me- 69% of patients after 7 to 14 days, spontaneous cure in 19 ticulous surgical and postoperative care. Because men- sinus or transpterygoid approaches to the pterygopalatine ingitis is a possibility in the setting of acute bacterial rhi- or infratemporal fossa may result in synechia between the nosinusitis, it must be treated aggressively in patients after middle turbinate and lateral nasal wall. Mature bacterial rhinosinusitis, it may not be the appropriate choice synechia require a formal lysis of synechia, which involves in patients after endoscopic pituitary and skull base surgery. In our series the incidence of Endoscopic culture-directed treatment of acute bacte- postoperative rhinosinusitis (based on American Academy of rial rhinosinusitis has improved treatment strategies. More common was acute bacterial rhinosinusitis after endoscopic pituitary or crusting, accompanied with mucoid or purulent secretions skull base surgery. Studies in patients with acute bacterial 31 Managing Postoperative Sinusitis 325 rhinosinusitis after endoscopic sinus surgery have shown medically, with the other half requiring surgery (one report that most postoperative infections were present as de novo of a sphenoid sinus mucocele. Senior et al16 looked at a large infections by bacteria other than colonizing bacteria. The one patient whose condi- well as postoperative surgical debridements, needs to be tion did not resolve required surgery for bilateral sphenoid performed cautiously given the potential for intracranial mucoceles. This is certainly not the case after the results with a series of more than 300 patients who under- skull base is well healed but is a more signifcant consid- went purely endonasal endoscopic transsphenoidal surgery. Postoperative debridements must also proceed An incidence of between 6% and 15% is thus supported with signifcant caution given the risk of disturbing the mul- by the otolaryngologic literature. A small piece of crust in ries, however, in which the trend has been away from the the posterior nasal cavity could be tightly tethered to one of sublabial transseptal approach and toward the purely endo- the layers of the multilayered skull base reconstruction. Any scopic approach, the incidence has decreased to the 6 to 8% attempt to remove this crust could disturb the skull base re- range. Determining the exact incidence remains difcult due Meningitis is a rare but possible complication in the set- to the small number of cases as well as the varied surgi- ting of acute bacterial rhinosinusitis. Chronic Rhinosinusitis Chronic rhinosinusitis in patients after endoscopic pitu- itary and skull base surgery is usually limited to the sphe- I Role of Imaging in Diagnosis noid sinus, in which case it is known as sphenoiditis, and Computed Tomography the symptoms manifested are more frequently retro-orbital headache, visual changes, meningitis, and nasal obstruc- Imaging is an important diagnostic tool in the evaluation tion. Sphenoid ous, and a high index of suspicion must be maintained for abnormalities remain visible on computed tomography diagnosis. Therefore, endoscopic scopic and sublabial transseptal transsphenoidal pituitary fndings are more valuable in diagnosing sinusitis during surgery, Batra et al15 reported an incidence of 7. Infamed mucosa appears as a low signal on T1 and high signal on T2 due to its high water content, A variety of materials and techniques have been used in en- whereas fbrosis has a low signal content on T1 and T2. Materials include autografts, allografts, and homo- varying intervals after transsphenoidal surgery, abnormali- grafts. Techniques include single-layer, multilayer, onlay, inlay, ties continued long after 3 months. Early scans, performed 1 gasket-seal, and pedicled vascularized grafts, among others. Intermediate scans, performed 6 to 18 months after after endoscopic pituitary surgery emphasizes the rapid heal- surgery, were abnormal in 71% of patients and showed con- ing of the skull base.
In 1993 purchase penegra 100 mg online, with the introduction into clinical use of desflurane discount 50 mg penegra amex, an even more sophisticated vaporizer was introduced to handle the unique physical properties of this agent cheap 50mg penegra fast delivery. Physics The physical properties of potent inhaled volatile anesthetic agents that are pertinent to a discussion of vaporizers and vaporization are shown in Table 25-2 buy penegra 50 mg free shipping. Vapor Pressure Contemporary inhaled volatile anesthetics exist in the liquid state at temperatures below 20°C. When a volatile liquid is in a closed container, molecules escape from the liquid phase to the vapor phase until the number of molecules in the vapor phase is constant. As the temperature increases, more molecules enter the vapor phase, and the vapor pressure increases (Fig. Vapor pressure is independent of atmospheric pressure and is dependent only on the temperature and physical characteristics of the liquid. The boiling point of a liquid is defined as that temperature at which the vapor pressure equals atmospheric pressure. At 760 mmHg, the boiling points for desflurane, isoflurane, halothane, enflurane, and sevoflurane are approximately 22. Unlike other contemporary inhaled anesthetics, desflurane boils at temperatures that may be encountered in particularly warm clinical settings such as pediatric and burn operating rooms. This unique physical characteristic alone mandates a special vaporizer design to control the delivery of desflurane. If agent-specific vaporizers are accidentally filled with incorrect liquid anesthetic agents, the resulting mixtures of volatile agents may demonstrate properties that differ from those of the individual component agents and may alter the anticipated output of the vaporizer (see section on Variable Bypass Vaporizers: Misfilling). The amount of energy that is consumed by a given liquid as it is converted to a vapor is referred to as the latent heat of vaporization. It is more precisely defined as the number of calories required to change 1 g of liquid into vapor without a temperature change. The thermal energy for vaporization must be derived from the liquid itself or from an external source. The temperature of the liquid itself will decrease during vaporization in the absence of an external energy source. This energy loss can lead to significant decreases in temperature of the remaining liquid and can greatly decrease subsequent vaporization. The vapor pressure curve for desflurane is both steeper and shifted to higher vapor pressures when compared with the curves for other contemporary inhaled anesthetics. The concept of specific heat is important to the design, operation, and construction of vaporizers because it is applicable in two ways. First, the specific heat value for an inhaled anesthetic is important because it indicates how much heat must be supplied to the liquid to maintain a constant temperature when heat is being lost during vaporization. Second, manufacturers select vaporizer component materials that have a high specific heat to minimize temperature changes associated with vaporization. Thermal Conductivity Thermal conductivity is a measure of the rate at which heat flows through a substance. Vaporizers are constructed of metals that have relatively high thermal conductivity, thus maintaining a uniform internal temperature. Variable bypass refers to the method for regulating the anesthetic agent concentration output from the vaporizer. As fresh gas from the machine flowmeters enters the vaporizer inlet, the concentration control dial setting determines the ratio of incoming gas that flows through the bypass chamber to that entering the vaporizing chamber (sump). The gas channeled through the vaporizing chamber flows over a wick system saturated with the liquid anesthetic and subsequently also becomes saturated with vapor. Thus, flow- over refers to the method of vaporization and is in contrast to a bubble-through system that is used in now-obsolete measured flow vaporizers (e. Each is equipped with an automated temperature- compensating device that helps maintain a constant vapor concentration output for a given concentration dial setting, and over a wide range of operating temperatures. These vaporizers are agent specific because each is designed to accommodate a single anesthetic agent, and are out-of-circuit, that is, physically located outside of the breathing circuit. Variable bypass vaporizers are used to deliver halothane, enflurane, isoflurane, and sevoflurane, but not desflurane. Basic Operating Principles A diagram of a generic, variable bypass vaporizer is shown in Figure 25-30. In principle, it creates a saturated vapor concentration of the liquid agent in the vaporizing chamber and dilutes this to clinically usable concentrations by mixing it with fresh gas from the vaporizer bypass. This corresponds to a vapor concentration of 160 mmHg/760 mmHg × 100 = 21%, which is too high for clinical use. Therefore, the vaporizer must dilute this 21% concentration to a clinically desirable value indicated on the vaporizer dial. Vaporizer components include the concentration control dial, the bypass chamber, the vaporizing chamber, the filler port, and the filler cap. Using the filler port, the operator fills the vaporizing chamber with liquid anesthetic. The maximum safe fill level is predetermined by the position of the filler port, which is designed to minimize the likelihood of overfilling. If a vaporizer is overfilled or tilted, liquid anesthetic can spill into the bypass via the inlet and outlet chambers. If this were to happen, both the vaporizing chamber flow and the bypass flow could potentially be carrying saturated anesthetic vapor, and an overdose would result. The concentration control dial is a variable restrictor, which controls gas flow through the bypass and through the outlet of the vaporizing chamber. Most of the flow passes straight through the bypass chamber to the vaporizer outlet. Depending on the temperature and vapor pressure of the particular inhaled anesthetic, the fresh gas entering the vaporizing chamber entrains a specific flow of the anesthetic agent saturated vapor. The mixture that exits the vaporizer outlet comprises flow through the bypass chamber, flow through the vaporizing chamber, and flow of entrained anesthetic vapor. The final concentration of inhaled anesthetic (in volumes percent) is the ratio of the flow of the entrained anesthetic vapor to the total gas flow. It can be 1670 approximated from the following formula :85 Figure 25-30 Generic variable bypass vaporizer. If the vaporizer dial is set to deliver 1% sevoflurane, the bypass flow will be 2,000 mL/min because 21 mL of sevoflurane vapor will be diluted in a total volume of 2,100 mL (21 + 79 + 2,000); 21/2,100 = 1% by volume. To achieve this the vaporizer concentration dial has created a flow ratio of 2,000:100 or 20:1 between the bypass flow and the flow exiting the vaporizing chamber. When the dial is set to deliver 2% sevoflurane, the vaporizer concentration dial creates a ratio of 950:100, or 9. In the case of an isoflurane vaporizer set to deliver 1% isoflurane, the concentration of isoflurane vapor in the vaporizing chamber will be 238/760 = 31% at 20°C (Table 25-2). Each 100 mL of gas leaving the vaporizing chamber will contain 31 mL of isoflurane vapor, the other 69 mL being the gas that entered the vaporizing chamber. The bypass flow must be 3,000 mL because now 31 mL of isoflurane vapor is diluted in a total volume of 3,100 (31 + 69 + 3,000). The vaporizer concentration dial has created a flow ratio 1671 of 30:1 between the bypass flow and the flow exiting the vaporizing chamber. Variable bypass vaporizers incorporate a mechanism to compensate for variations in ambient temperature. To compensate for this, the bimetallic strip of the temperature-compensating valve leans to the right, decreasing the resistance to gas flow through the bypass chamber. This allows more flow to pass through the bypass chamber and less flow to pass through the vaporizing chamber. This increases the resistance to flow through the bypass chamber, causing relatively more flow to pass through the vaporizing chamber and less flow to pass through the bypass chamber. The net effect in both situations is maintenance of relatively constant vapor output concentration despite large swings in ambient temperature. Designing such a vaporizer is difficult because as ambient conditions change, the physical properties of gases and of the vaporizers themselves can change. Even though some of the most sophisticated vaporizing systems now available use computer-controlled components and multiple sensors, they have yet to become significantly more accurate than conventional mechanical flow- splitting (variable bypass) vaporizers. Fresh Gas Flow Rate With a fixed dial setting, vaporizer output can vary with the rate of gas flowing through the vaporizer. The output of all variable bypass vaporizers is less than the dial setting at low flow rates (<250 mL/min). This results from the relatively high density of volatile inhaled anesthetic vapors.
This vast compendium Glomerulocystic kidney disease of developmental misadventures prompted Edith Potter to Glomerular cysts associated with hereditary syndromes comment that “The more complicated an organ in its devel- Other contexts with glomerular cysts opment buy penegra 100 mg with amex, the more subject it is to maldevelopment order penegra 100mg on-line, and in Tubulointerstitial diseases with or without cysts this respect the kidney outranks most other organs discount penegra 50mg fast delivery. Phycomatoses and renal disease von Hippel-Lindau disease Tuberous sclerosis complex Table 2 generic 50 mg penegra mastercard. This section presents a modest sampling of the and Number many possible defects and combination of defects. These diseases are discussed together because there are coexistent anomalies in nearly every case. In most cases, the kidneys show normal nephron Rotation anomalies are recognized by the abnormal location development and function. Incomplete rotation results in an anterior ectopias, problems related to urinary tract obstruction and location. This family of diseases may be spo- Over-rotation results in a posterior or a lateral pelvis and radic or syndromic, and may occur in combination with renal ureter. These kidneys illustrate incomplete rotation in which the ureters are anterior rather than in the normal medial location. Although this is a characteristic of ureters in renal fusion, in this case both kidneys remain separate. Notice that the ureters are thickened and the pelves appear dilated, consistent with the obstructive complication of this anomaly (From Zhou M, Magi-Galluzzi C, editors. Their location may be pelvic, abdominal, above the most commonly affects the lower pole, resulting in what is normal renal fossa and subdiaphragmatic, thoracic, or in the referred to as a horseshoe kidney. Midline fusion prevents medial rotation of the ureters; thus, anterior nonrotation is present. Ascent to the usual ﬂank location is prevented by the inferior mesen- teric artery, which loops over the fused kidneys. This means horseshoe kidneys are not only fused and nonrotated, they are also ectopic. Its blood supply arises from It represents both kidneys fused at their lower poles, resulting in the iliac vessels. In addition to this anomaly, the contralateral kidney was distinctive shape responsible for its name. There is hypertensive injury (arterial nephrosclerosis), accounting for the coarsely granular surface 2. The right pelvis is biﬁd, and the left pelvis is triﬁd with a narrow connecting portion Fig. There was urethral atre- sia resulting in megacystis and massively dilated proximal hydroureters. Although the right kidney is much smaller than the left kidney, notice that both renal moieties of the horseshoe kidney contain numerous small peripheral cysts Fig. These are extensively fused kidneys resulting in a globular appearance only minimally horseshoe-shaped. This anomaly was not isolated; it was associated with an Arnold-Chiari malformation 22 2 Developmental Anomalies and Cystic Kidney Diseases 2. Renal hypoplasia was deﬁned by Heptinstall many years ago in the ﬁrst edition of Heptinstall’s Pathology of the Kidney as follows: “in the absence of acquired disease, reduction of one kidney by more than 50 % in size, or in total renal mass by more than 1/3 is regarded as true hypoplasia. A truly hypoplastic kidney possesses ﬁve or fewer, in contrast to the normal complement of ten or more. Because renal hypoplasias should have histologically normal-appearing nephrons, they are most readily recog- nized on gross exanimation by reduction in renal size and weight. Although a reduction in the number of renal lobes was emphasized by Heptinstall, a reduction in cortical thick- ness due to reduced nephron generation also may result in a Fig. This composite specimen viewed pos- small kidney and may be noted microscopically in optimally teriorly is from a newborn with nonsyndromic multiple congenital oriented sections. The kidneys are fused and were ectopic, located in the right opmental “defect” if one includes reduced nephron numbers, lower pelvis. Proof of because nephron number shows marked individual variation fusion is provided by the left ureter, which is on the right side and crosses over to the left side of the bladder. The cal threshold for assignment of what should be regarded as anus was imperforate “normal” nephron numbers versus hypoplasia has not been 2. A reduction in nephron numbers often is related to prematurity, poor maternal health, and low birth weight, and is physiologically important because it has been strongly correlated with risk of hypertension as an adult. The types of renal hypoplasia are: • Simple hypoplasia • Oligomeganephronic hypoplasia • Cortical hypoplasia • Segmental hypoplasia/Ask-Upmark kidney 2. However, if the renal mass is insufﬁcient to maintain proper homeostasis, with physical maturation nephron scle- rosis may ensue. The cortex is thin on the right side, and there is no column of Bertin between the two pyramids. Their combined weight and size, especially the kidney on the left, are less than half of normal. There was no histologic abnormality 24 2 Developmental Anomalies and Cystic Kidney Diseases 2. The daunting enlarged compared with nephrons in a patient of a similar name of this disorder describes its essential features. Patients present with nephrotic range proteinuria and kidneys are small with reduced numbers of renal lobes that develop renal failure at a young age. The enlarged nephrons may not be easily appreciated in a single photograph but require comparison with an image at similar magniﬁcation from a patient of comparable age. It also has more numerous glomerular capillary loops than normal, a feature that may be appreciated in this image. This is another example of oligome- ganephronia from a biopsy performed for proteinuria and renal insufﬁciency. This glomerulus is markedly enlarged and also appears to con- tain more numerous capillary loops than a normal glomerulus. Cortical hypoplasia refers to a reduction in nephron However, if a threshold for a diagnosis of cortical hypoplasia generations. Determination of nephron generations is best is set at a 50 % reduction in nephron generation—that is, accomplished with a nephrectomy specimen so that properly four to ﬁve generations in a properly oriented section—then oriented sections aligned along medullary rays are avail- the reliability of this assessment is reasonable. Cortical hypoplasia may be difﬁcult to rec- ognize histologically unless a well-oriented section shows the full corti- cal thickness along a medullary ray. In this image from a normal kidney, there are two medullary rays with three rows of nephrons aligned per- pendicular to the medullary ray tubules Fig. Notice that there are no medullary rays and that there is no evidence of nephron atrophy or metanephric dysgenesis Fig 2. Although the normal kidney should have 10–14 generations of nephrons, identifying more than 9 to 10 genera- tions in a well-oriented section is difﬁcult. Others, like the author, agree with reﬂux-related injury, but believe most cases are developmental in origin as a result of in utero reﬂux that damages the developing renal lobe. Segmental hypoplasia is deﬁned as a small kidney with a deep cortical groove(s) and dilatation of adjacent calyx. The cortex contains few tubules, with no or only rare glomeruli, little or no inﬂammation, and no evidence of metanephric dysgen- esis or nephron atrophy. The medulla is absent or ﬂattened with no loops of Henle and may contain a distinctive cellular Fig 2. This kidney is from a 17-year-old patient interstitial mesenchymal tissue not present in the normal renal with cortical hypoplasia. Extrarenal vascular anomalies occur in 40 % of cases of three nephron generations are present, and there is no atrophy or supporting a developmental abnormality. This example of segmental hypoplasia shows the circumferential deep cortical groove characteristic of segmen- tal hypoplasia. Only two to three nephron generations are present, and there is no atrophy or metanephric dysgenesis Fig. It is only 7 cm in length and contains a single circumferential deep cortical groove and dilated collecting system. In addition to the segmental hypoplastic focus, there was cortical hypoplasia with a reduc- tion in nephron generation to two to three generations in sections of oth- erwise normal cortex away from the groove, as shown in Fig. This developmental abnormality strengthens the postulate that segmental hypoplasia may have a developmental basis, at least in some cases Fig. There are multiple hyp- glomeruli are present to indicate an atrophic lesion oplastic foci, and the renal pelvis is signiﬁcantly dilated 28 2 Developmental Anomalies and Cystic Kidney Diseases Fig.
Preferably generic penegra 50mg with amex, the margins Assessment of the bone available for implantation is of the prosthesis should extend in areas of limited mobility essential during preoperative planning buy penegra 50mg overnight delivery. A substantial advantage of navigation is precise pre- be placed deep enough to allow for sufcient thickness of the operative planning discount penegra 50mg online, which is optimized by taking into prosthetic material buy 50 mg penegra amex. A transparent template is helpful to consideration anatomic and prosthetic aspects. Using this assess the dimensional relationship between the surface of the technology, a plastic template of the ideal position of the prosthesis and the intended implantation point. Te attach- implants is made using radiopaque markers, and the patient ment system should be designed according to the individual is scanned with the template. Te available bone can then be requirements, whether frm and rigid, fexible, or a combina- assessed, and implant placement can be planned such that tion of both, depending on the size and location of the defect damage to critical anatomic structures is avoided, improving and the areas to be covered. For example, in cases tage that they can be extended in undercuts for additional in which the external ear, the mastoid process, and its air-cell stability. Furthermore, implants in the concentration is avoided and forces are distributed uniformly orbital rim are difcult to position, as they need to point to ensure long-term survival of the implants. Although this internally into the orbit and sufcient bone needs to be avail- does not pose many problems in auricular, orbital, or simple able. Individually designed implants necessary for camoufage by the prosthesis later on. In these cases, angulation and direction of the implants are secondary, because the custom-designed retention system can Prosthodontic Methods in Endosseous compensate for these issues. It is of greater importance to Craniofacial Implants place many implants in the remaining skeleton to distribute Te prosthetic requirements of treatment with extraoral or the load and achieve maximum rigidity. In combined defects complex combination devices difer greatly from those for where the maxilla is missing, the primary goal is restoration 15 intraoral prostheses. Te position of plastic ear models with radiopaque markers is visible in all views. Tis process is accompanied Te placement of endosseous implants for the rehabilitation by histologic changes such as osteolysis and infltration of of craniofacial defects is limited by three factors: the avail- fbrous tissue. Although osseointegration is possible in radi- ability of bone, the extension of the prosthesis, and the ated bone, a higher rate of osseointegration failure is expected. Tere is still insufcient clinical and biologic infor- mation to suggest an established time table for the implanta- tion of endosseous implants in irradiated bone, because the bone healing capacity can vary depending on the period of 17 irradiation, the site, and the addition of chemotherapy. D Figure 23-2, cont’d D, Areas suitable for implantation of implants in combined intra-/extraoral defects. A fange is designed for these Healing abutment implants to avoid dislocation into interior compartments. Using these implants, many of the former limitations of prostheses designed to cover defects after tumor ablation in the face have been eliminated. Extraoral prostheses can now be directly anchored to the underlying bone with functional and aesthetic improvements and long-lasting results (Figure 23-3, A). If no template is used, the position of the implants To position the implants, it is helpful to sculpture a wax replica should be marked prior to surgery with a pen or needle, as the of the prosthesis, which can also be used to fabricate a template optimal implantation sites are diffcult to determine in the operat- 24 ing room when the patient is dressed for surgery, due to a lack of for surgery. In auricular prostheses, the external meatus can be incorporated into the template and used as a reference point visible landmarks. It is important to use To place the craniofacial implants, the implant sites are exposed sharp drilling instruments and suffcient irrigation to avoid thermal by refection of a full thickness skin fap with the incision line trauma to the bone and to optimize bone healing. A cover screw is placed into the implant to For the insertion of craniofacial implants, a guide drill is frst used prevent ingrowth of soft tissue during the healing period. The implants drill is then used to give the fnal exact diameter and direction of can be exposed after a healing interval of 3 to 4 months. For implantation into the temporal bone, the widened ated bone, a longer healing period is recommended. In other craniofacial loca- are not exposed until 6 to 12 months after the installation, espe- tions, pretapping is not required because of the lower bone cially in the midface and orbital regions because of lower survival density. Finally, the implant is inserted gently, preferably with a rates of osseointegrated implants in these areas. For extraoral locations, split skin grafts with a 7- to tion of the subcutaneous tissue. Ideally, the skin 10 mm around 8-mm thickness can be harvested behind the ear, where the skin the abutment should be free of hair follicles and immobile; in is thin, the texture is ideal, and the scar is not visible. Alterna- addition, thinned and fat-free skin is required to prevent granula- tively, a split skin graft can be taken from the thigh or the inside 26 of the upper arm, which is usually more convenient for the tion tissue formation that leads to a higher implant failure rate. For intranasal or intraoral locations, mucosal skin grafts gold interface is at least 2 mm and a maximum of 5 mm above (e. Subdermal margins and fange exposure can potentially lead to infammation and loss of the implant. The thickness the implants are uncovered, if the surrounding tissue is too thick of the mucosal fap should be 0. In the donor area, and mobile resulting in chronic irritation, then surgical revision wound healing by free granulation of the tissue is usually rapid needs to be considered. Impressions of craniofacial defects are taken with the patient in Gauze is placed on the alginate surface for retention, and the an upright, sitting position. In combined intra-/extraoral or nasal impression is supported with fast-setting plaster and turned. A master cast is produced with brass replicas in the Copings are mounted on each abutment cylinder to ensure the correct position and used for fabrication of the retention correct transfer into the master impression. C, With skin-penetrating abutments, it is important that the abutment/gold interface is at least 2 mm and a maximum of 5 mm above the tissue surface. Avoidance and Management of Intraoperative the surgical follow-up should initially be scheduled in an Complications alternating manner, so that the patient is seen every 3 months. Later, both appointments can be combined in a semiannual Long-term success of a facial, orbital, or auricular prosthesis review. Te Te survival rates of extraoral implants depend on the site viability of all components of the prosthesis should be assessed of implantation, ranging from 73. Radiographs do not need to highest failure rates are observed in the frontal bone, zygoma, be performed routinely, because a right-angle projection, mandible, and nasal maxilla. Te lowest implant failure rates which allows assessment of the implant-bone interface, is not are observed in the oral maxilla. Clinical evaluation of implants placed into irradiated bone appears to be even the stability of the implant and the status of the surrounding higher and also depends on the retention system of the pros- tissues is crucial. Te time of the In addition, there appears to be a direct correlation between second-stage surgery, when the skin-penetrating abutments the level of hygiene and infammatory soft tissue reactions of are attached to the implant, needs to be adjusted accordingly the skin at extraoral implantation sites. In the mastoid, where and a radical neck dissection, the patient may be impaired in the success rate of osseointegrated implants is high, the his or her movements, or the patient many not be able to see second-stage procedure is performed after 3 to 4 months. Orbital implants are most difcult for the Alternatively, a one-stage procedure can be used. In all other patient to clean, and the failure rate is the highest among all craniofacial locations and in irradiated bone, a healing period facial locations. Te foor of the nose is the easiest to clean of 6 months is advised, as clinical experience has shown that and has the lowest rate of soft tissue reactions leading to loss osseointegration appears to be slower, likely due to difer- of the implant. Patient follow-up should there- tion and prosthetic restoration can be shortened in patients fore be adjusted to the individual needs. If soft tissue reac- with a poor tumor prognosis, for maximal improvement of tions are found and the patient is unable to clean the implant 31 quality of life. Infammation can be caused by Postoperative Considerations surrounding tissues that are too thick and mobile. It is there- fore favorable for the skin of mucosa to be thin and frmly A craniofacial prosthesis requires a lifetime commitment and attached to the underlying bone. For the survival of endosseous can be thinned out in the area where the implant is inserted craniofacial implants, it is especially important that the at the time of implantation. To avoid this problem, it is important to check the ties may have problems cleaning the implant sites. In addi- removed; it is not sufcient to excise the skin surrounding tion, implants in the temporal bone and the orbit are difcult the implant.