Practical Plastic Surgery

322 Practical Plastic Surgery

Suggested Reading

1.Arnez ZM. Immediate reconstruction of the lower extremity—an update. Clin Plast Surg 1991; 18(3):449.

2.Arnold PG, Irons GB. Lower-extremity muscle flaps. Orthop Clin North Am 1984; 15(3):441.

3.Attinger C. Soft-tissue coverage for lower-extremity trauma. Orthop Clin North Am 1995; 26(2):295.

4.Byrd HS, Cierny IIIrd G, Tebbetts JB. The management of open tibial fractures with associated soft-tissue loss: External pin fixation with early flap coverage. Plast Reconstr Surg 1981; 68(1):73.

5.Heller L, Levin LS. Lower extremity microsurgical reconstruction. Plast Reconstr Surg 2001; 108(4):1029.

6.Johansen K, Daines M, Howley T et al. Objective criteria accurately predict amputation following lower extremity trauma. J Trauma 1990; 30:568.

7.Park S, Han SH, Lee TJ. Algorithm for recipient vessel selection in free tissue transfer to the lower extremity. Plast Reconstr Surg 1999; 103(7):1937-48.

8.Zenn MR, Levin LS. Microvascular reconstruction of the lower extremity. Semin Surg Oncol 2000; 19(3):272.

Table 53.1. Age of eruption of the deciduous teeth

Pattern of Eruption

The deciduous teeth begin to erupt at six months of age. Maxillary and mandibular teeth tend to erupt at the same times (Table 53.1). The primary dentition eventually exfoliates and is replaced by the permanent detention in a predictable sequence (Table 53.2).

Pathologic Descriptions

Occlusion describes the relationship, or fit, between the upper and lower teeth when in contact. The occlusal plane is the curvilinear plane along which the teeth erupt and meet each other.

Overbite refers to the amount of vertical overlap between the maxillary and mandibular incisal edges when in occlusion. Anterior open bite describes a situation where these incisal edges do not overlap, resulting in a negative overbite.

Overjet refers to the forward projection of the upper incisors beyond the lower incisors when the teeth are in occlusion.

Crossbite exists when there is an abnormal buccolingual relationship among 53 the upper and lower molars. In normal or neutral occlusion, the buccal cusps of

the maxillary teeth overlap those of the mandibular teeth. Buccal crossbite occurs when the entire maxillary tooth is buccal to the mandibular tooth. Lingual crossbite occurs when the buccal cusps of the mandibular teeth overlap the maxillary teeth.

Table 53.2. Age of eruption of the permanent teeth

Common Tooth Injuries

Subluxation refers to intrusion and extrusion. Most intruded deciduous teeth require no treatment as they will erupt spontaneously. However, if the intruded tooth fails to resorb or erupt in an appropriate timeframe, it must be extracted to allow for eruption of the permanent tooth bud. Intruded permanent teeth are electively repositioned by the orthodontist.

Extruded primary teeth are usually not replanted; the patient should instead be referred to an orthodontist for fabrication of a space maintainer. An attempt may be made to replant an extruded permanent tooth within 1-2 hours of injury. Prior to any attempt, the socket should be irrigated. After one hour, any clot or granulation in the socket should be aggressively debrided. After two hours, replantation will generally fail.

Tooth fractures that involve the crown are typically treated by the endodontist. Fractures involving the root usually require removal of the tooth.

Pearls and Pitfalls

The importance of accurate identification of teeth cannot be overstated. Learn the standard nomenclature. If you have any doubt about which tooth number to use, refer to the proper name, such as “right mandibular second molar.” You do not want to write the wrong number in a progress note or extract the wrong tooth in the line of a fracture.

It is important to treat extruded primary teeth with a space maintainer, which is fabricated by an orthodontist or pediatric dentist. Loss of primary teeth may lead to shifting of the remaining teeth. The resultant loss of arch space can ultimately cause

53 crowding and malocclusion of the permanent dentition.

Suggested Reading

1.Bischoff RJ, Simon WJ. The occluding system of the teeth. A review of the occluding system of the mouth—from nomenclature to malocclusions. Dent Assist 1975; 44(1):17.

2.Goodman P. A universal system for identifying permanent and primary teeth. J Dent Child 1967; 34(5):312.

3.Lunt RC, Law DB. A review of the chronology of eruption of deciduous teeth. J Am Dent Assoc 1974; 89(4):872.

4.Natiella JR, Armitage JE, Greene GW. The replantation and transplantation of teeth. A review: Oral Surg Oral Med Oral Pathol 1970; 29(3):397.

5.Wilson KS, Hohmann A. Dental anatomy and occlusion. Otolaryngol Clin North Am 1976; 9(2):425.

•The width of the nasal dorsum is half the intercanthal width.

•Facial midline, nasal tip, maxillary and mandibular midlines, and chin point are in line.

•Upper face height (glabella to subnasale) should be equal to lower face height (subnasale to menton).

Inspect for symmetry and size of the forehead, orbits, eyes, ears and nose. Useful measurements include:

•Interpupillary width: normal is 65 mm

•Intercanthal width: normal is 32 mm for whites and 35 mm for African Americans

•Upper lip length: normal is 22 mm for males and 20 mm for females. Measured from subnasale to upper lip stomion.

•Upper tooth to lip relationship: 2.5 mm of incisal edge lips the lips relaxed

•Lower lip length: normal is 42 mm for males, 38 mm for females. Measured from lower lip stomion to menton.

At the end of the physical exam, take high quality digital photographs. These pho-

tos will be crucial to videocephalometric predictions, correlation with model surgery, and will be referred to intraoperatively. The following photos are recommended:

•Frontal photograph relaxed

•Frontal photograph smiling

•Lateral profile—right and left

•45˚ oblique

•Intraoral—central, right, left

The fabrication of dental casts aids in diagnosis as well as treatment. For ex-

ample, in orthognathic surgery it is essential to fabricate surgical splints. The casts must be properly mounted using the facebow, bite record and articulator.

54 The orthognathic workup and cephalometric analysis are important since they determine many of the surgical movements. A key point to an accurate workup is the careful positioning of the mandible in centric relation rather than in centric occlusion during the bite registration. Centric relation denotes position of mandible where the condyles are in the most superior, posterior position in the mandibular fossa. Centric occlusion is the position with maximal intercuspation of the teeth. During surgery, the mandible is positioned in centric relation as this depicts the skeletal defect and allows for a reproducible anatomic position.

Radiographic Analysis

After the clinical exam is completed, radiographic analysis helps to further define the nature of the patient’s maxillofacial deformity. The Panorex, lateral cephalogram and AP cephalogram are used. The Panorex is inspected for pathology of the sinus, joints, mandible, maxilla and dentition. Examine the Panorex closely for condylar morphology and position. The Ramus Condyle Unit is measured to determine if there are any asymmetries in condylar growth. This may be indicative of conditions such as idiopathic condylar resorption or condylar hyperplasia. The lateral and AP cephalograms are the two principle radiographs of othognathic surgery and cephalometric analysis. Classical cephalometric analysis required tracing the cephalometric film by hand. This allowed for identification of the hard and soft tissue landmarks used in the cephalometric analysis. Digital radiographs and computer cephalometric analysis are replacing traditional radiographs and hand tracings. Using a computerized tracing

program, the surgeon selects several landmarks on the digitized lateral cephalogram. The computer then produces the cephalometric measurements and the digital tracing.

The relationship between the cranial base, nasomaxillary complex, mandible and maxillomandibular dentition is determined by the resulting angular and linear measurements. Notably, the surgeon may measure the distance from sella to posterior nasal spine (PNS). This value determines the position of the posterior maxilla in relation to the cranial base. The normal value is between 45-50 mm.

Cephalometric Analysis

The cephalometric analysis is a valuable tool that will assist the clinician with the diagnosis of a facial deformity. The diagnosis and treatment plan are determined during the clinical and cephalometric analysis. There are a variety of cephalometric analyses in clinical practice; the Singer and Harvard methods are most commonly used. Normal values for cephalometric measurements in adults are listed in Table 54.1.

Important cephalometric measurements include the following:

1.Porion: midpoint of upper contour of the external auditory canal

2.Sella: midpoint of the sella turcica

3.Orbitale: most inferior point along the bony orbit

4.Pterygomaxillary fissure: most superior posterior point of the pterygomaxillary fissure

5.Nasion: most anterior point of the frontonasal suture

6.Basion: Most inferior anterior point of the foramen magnum

7.Anterior nasal spine (ANS): most anterior point of the anterior nasal spine

8.Posterior nasal spine (PNS): most posterior point of the anterior nasal spine

9.A point: most posterior point along the bony premaxilla between ANS and 54 maxillary incisor

Table 54.1. Cephalometric measurements for adults (in mm)

10.B point: most posterior point along the bony contour of the mandible between mandibular incisor and pogonion

11.Pogonion: most anterior point along the contour of the bony chin

12.Menton: most inferior point along the mandibular symphysis

13.Gnathion: point along bony chin between menton and pogonion

14.Gonion: angle of the mandible at the intersection of the tangents drawn from the posterior ramus border and the lower ramus

15.Articulare: point of intersection between the cranial base and posterior ramus

16.Condylion: most superior posterior point of the bony condyle Important cephalometric planes and angles include the following:

1.Sella-Nasion-A point: SNA

2.Sella-Nasion-B point: SNB

3.A point-Nasion-B point: ANB

4.Frankfort horizontal (FH) plane: Pogonion—Orbitale

5.Palatal plane: ANS-PNS

6.Occlusal plane: plane from mesial cusp of maxillary molar through point bisecting overbite

7.Mandibular plane: tangent along lower border of mandible

8.Gonial angle: Articulare-Gonion-Menton

SNA and SNB provide an assessment of the maxillary and mandibular relationship to the cranial base. However, in order to utilize SN as the normal inclination of the anterior cranial base, the surgeon must first normalize the actual SN position to the normal SN-FH of 6 degrees. In most patients, the sella turcica is normally positioned and thus the sella to Frankfort angle is normal. However, in patients with craniofacial deformities, congenital syndromes, or sequences, it is imperative to identify the relationship of sella-to-FH. Altering the normal position of sella will, by

54default, alter the SNA and SNB. In order to assess the true SNA/SNB one must determine the SN-FH correction.

1.First measure the SN-Frankfurt angle (normal is 6˚)

2.If the SN-F angle is abnormally acute due to a shallow SN plane, the measured SNA and SNB will be too obtuse. Therefore, we must subtract the

difference ([SN-FHactual-SN-FHnormal]) to generate the “corrected” SNA and SNB.

3.If the SN-F angle is abnormally obtuse due to a steep SN plane, the measured SNA and SNB will be too acute. Therefore, one must add the difference ([SN-FHactual-SN-FHnormal]) to generate the “corrected” SNA and SNB.

PA Cephalogram

The PA cephalogram illustrates transverse and vertical skeletal relationships and evaluates facial symmetry. The first step in analyzing the PA film is to analyze the transverse dimension using a J point analysis. A horizontal measurement is made from the lateral aspects of the maxilla at the level of the pyriform rims. Similarly, a horizontal measurement is made from antegonial notch form right to left. The difference between these two values is used to identify an excessively narrow maxilla or enlarged mandible. The normal J point value is between 20 and 23 mm. Next, the PA cephalogram is drawn on tracing paper. Horizontal lines are drawn at the infraorbital rim, pyriform rim, occlusal plane and gonial angle. These marks are compared to a vertical midline mark in order to determine symmetry and cant of the orbits, zygomas, maxilla and mandible.

54

Figure 54.1. Common cephalometric points and their relationships.