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Master's Thesis in Science in Medicine
Comparison of serial excision method in patients who
have big benign skin lesion using cogwheel pattern and
elliptical pattern method
Ajou University Graduate School
Department of Medical Science
Kyeong Beom Choi
Comparison of serial excision method in patients who
have big benign skin lesion using cogwheel pattern and
elliptical pattern method
Dong Ha Park, Advisor
I submit this thesis as the
Master's thesis in science in medicine.
February, 2017
Ajou University Graduate School
Science in Medicine
The Master's thesis of Kyeong Beom Choi in Science in
Medicine is hereby approved.
Thesis Defense Committee
President 박 동 하
Member 박 명 철
Member 김 철 호
Ajou University Graduate School
I
- ABSTRACT-
Comparison of serial excision method in patients who have big benign
skin lesion using cogwheel pattern and elliptical pattern method
Serial excision is the most simple and aesthetically suitable method for large congenital melanocytic nevus. However, a dumbbell shape nevus commonly remains after serial excision. The cogwheel pattern setial excision that contains Z-plasty was introduced in 2014.
We mathematically calculated the cogwheel pattern serial excision, and compared with previous elliptical pattern excision.
10 patients who received one traditional serial excision and 11 patients who received cogwheel pattern serial excision before complete excision were selected. We evaluated age, area, scar length, area per scar ratio, normal tissue resection, dog ear deformity, and patient satisfaction.
The long axis per short axis length was 1:2 in both groups. Normal tissue resection and dog ear deformity were statistically lower in the cogwheel pattern group. Area per scar ratio was lower and satisfaction was higher in the cogwheel pattern group, but the differences were not statistically significant
Cogwheel pattern serial excision makes the congenital melanocytic nevus more suitable for total excision.
II
TABLE
OF
CONTENTS
ABSTRACT I
TABLE OF CONTENTS II
LIST OF FIGURES III
LIST OF TABLES IV
I. INTRODUCTION 1
II. MATERIALS AND METHODS 3
III.RESULTS 12
IV.DISCUSSION 17
V.CONCLUSION. 19
REFERENCES. 20 국문요약
III
LIST
OF
FIGURES
Fig 1.Photograph of remnant dumbell shape nevus after traditional excision method. 2
Fig 2.
Design for elliptical pattern excision under imagine that the central circle is small
mass. 5
.Fig 3.
Design for cogwheel pattern excision. It is based on traditional elliptical pattern.
.
6
Fig 4.
Black part is the area that excised in cogwheel pattern excision. 7
Fig 5.
Comparison between elliptical, fusiform and cogwheel pattern excision. 8
Fig 6.
Algorithm of patients flow 9
IV
LIST
OF
TABLES
Table 1
Comparison of Area among Three Serial Excision Methods 10
Table 2
Mathematic Calculation among the Area of Three Methods 11
Table
3
The Raw Patients Data of Two Serial Excision Method 13
Table4
１
I.
I
NTRODUCTIONSeveral techniques of removing large congenital melanocytic nevus have been proposed. Serial excision, tissue expander insertion, excision and coverage with skin graft are common ways to excise the mass. Among these methods, serial excision is simplest and the character of replaced skin is same as the adjacent tissue. It is recommended to remove the mass before school age due to psychosocial development, especially in the face.1
In serial excision, surgeons should consider the aesthetic results, such as scar length, and reduce local deformities that include dog-ear deformity. Normal tissue should be preserved as much as possible. When the round mass receives serial excision, the remnant mass has a dumbbell shape (Figure 1). Normal skin tissue in between the lateral edge of nevus should be resected for complete excision.
The cogwheel pattern of serial excision was introduced in 2014.2 Using Z-plasty, the lateral edge of nevus can be resected under a more acute angle and the remnant nevus is transformed into a shape better suited for complete excision. In the seminal paper, only a brief explanation of the design was provided.
In this study, we designed the cogwheel pattern and mathematically compared it with the traditional elliptical pattern. Additionally, we compared aesthetic outcomes in patients who received the two different excision patterns.
２
Fig. 1.Photograph of remnant dumbell shape nevus after traditional excision method.
３
II.
M
ATERIALS ANDM
ETHODSMathematical Calculation
Figure 2 shows classical elliptical pattern excision for a small mass. In serial excision, the elliptical shape excision is commonly used. Practically, when the vertical tension is not severe and more excision of vertical length is possible, the mass can be excised using a vertically elongated elliptical pattern (we call it as fusiform pattern). This creates a dog ear deformity.
As its’ name implies, the cogwheel pattern of incision was inspired from cogwheel. In envisioning the pattern, it is best to picture circle with a radius of 3, with a center in (0,-2) as in elliptical excision. The elliptical excision is overlapped on the circle (Figure 3). Envisioning a circle that passes (1,2), (-3,0), and (3,0), with a center in (0,-1), the lower part is designed symmetrical with the upper part (Figures 4 and 5).
Cogwheel serial excision was designed under the hypothesis that maximal vertical length can achieve excision that equals excision using the fusiform and cogwheel excision methods. The main effect of this excision pattern is a more acute angle of than the conventional pattern (Figure 4), assuming that the maximal vertical length is constant (` = ` = ). Figure 4 displays the fusiform and cogwheel pattern simultaneously. Z-plasty is added with the previous fusiform pattern excision. The black area in the figure is bigger than the dark gray area, meaning that the cogwheel pattern can excise more area than the fusiform pattern. Table 1 summarizes characteristics of the three excision patterns. Table 2 provides the area calculation formula.
Patients and Methods
We designed retrospective study and 42 melanocytic nevus patients were included who underwent serial excision of their nevus in our hospital from 2010 to 2013. 24 patients were received fusiform pattern serial excision and 18 patients were received cogwheel pattern serial excision. All patients received one serial excision before complete excision, with an intervening interval from 6 to 12 months. Patients with incomplete charting in aspects like scar length and preoperative, intraoperative, and postoperative photo documentation were excluded, as were patients who did not comply with silicone gel scar treatment for 6 months or who were lost to follow up. 101 fusiform and 11 cogwheel pattern excision patients were ultimately enrolled.
４
Figure 6 shows the study flow.
All operations were conducted by one operator and performed in the suprafascial plane. In serial excision, we designed all the incision lines within the nevus and did not undermine the remnant nevus tissue to prevent the remnant nevus tissue expanding from tension. Complete excisions involved undermining around the normal tissue about 1 cm for better cosmetic result and preventing surrounding tissue distortion.
Before designing the incision line, a pinch test was performed in every patient to evaluate the maximal vertical length to be excised. In fusiform excision, we designed the elliptical excision line first and expand a vertical incision line, when the tension and dog ear deformity were acceptable.
We evaluated preoperative length of long and short axis, long per short axis length ratio, area and postoperative scar lengths, area per scar ratio, middle scar elongation, normal tissue resection, dog ear deformity, and patient`s satisfaction. If the patient is too young, we scored the parent`s score.
The longest length in the mass was measured first and recorded as the long axis. Then, the other longest length, which lies perpendicular to the long axis, was measured and recorded as the short axis. After the serial excision, long and short axis length was measured again. Area was calculated assuming that the nevus was oval or round in shape. Long per short axis length ratio was calculated because an oval-shaped nevus was easier to excise within a short scar length compared with a round nevus.
Scar lengths were measured with a flexible ruler capable of measuring a curved plane when stitches were removed. Area per scar ratio was calculated to compare the efficacy of the excision. The normal tissue resection was limited when the normal tissue was resected within medial and lateral edge of nevus in total excision. The scar length was evaluated upon suture removal in the outpatient clinic. Dog ear deformity and satisfaction were evaluated in outpatient clinic by patients at least after 6 months from complete excision.
Person`s chi-squared test for statistical analysis and group comparisons. p-value < 0.05 was considered statistically significant.
５
Fig. 2.
Design for elliptical pattern excision under imagine that the central circle is
small mass.
６
Fig. 3.
Design for cogwheel pattern excision. It is based on traditional elliptical
７
８
Fig. 5.
Comparison between elliptical, fusiform and cogwheel pattern excision. The
area of is elliptical pattern, is fusiform pattern, is cogwheel pattern. The black is
cogwheel pattern`s additional area while brighter gray is fusiform pattern`s additional
area. The black is more larger than brighter gray part.
９
１０
Table 1. Comparison of Area among Three Serial Excision Methods
Elliptical
Fusiform
Cogwheel
Width-length
3 : 1
6 :
√10
7 :
√10
１１
Table 2. Mathematic Calculation among the Area of Three Methods
Area Calculation
Elliptical
2 × ∫ √5
2− 𝑥
2− 4𝑑𝑥 =
3 −3− 24 + 50 sin
−1(
3
5
) ≅ 8.17506
Fusiform
2 × ∫ √(
23
2√10
)
2− 𝑥
2−
13
2√10
𝑑𝑥 =
3 −3−
39
√10
+
529
20
sin
−1(
6√10
23
) ≅ 13.3263
Cogwheel
2 × *∫ √52− 𝑥2− 4𝑑𝑥 3 −3 + ∫ (√10 − 𝑥2− 1) − (√25 − 𝑥2− 4) 𝑑𝑥 0 −2 + ∫ (√10 − 𝑥2− 1) − (𝑥 + 1)𝑑𝑥 + 1 0 = −17 + 25 sin−1(3 5) + 10 sin−1( 1 √10) + 10 sin −1( 3 √10) ≅ 14.7955１２
III.
R
ESULTSAll operations were conducted by the same surgeon using the same procedure. There were no wounds with major complication. Raw data is summarized in Table 3 and organized values are summarized in Table 4. One patient who received cogwheel pattern serial excision was photographed (Figures 7).
The average age was younger in the cogwheel group. The nevus was bigger in the cogwheel group but the long per short axis ratio was almost same, about 2:1. This result support the study`s validity for comparing the two excision pattern in different shape of nevus patients because oval shape mass can be excised within shorter scar than round mass. The area per scar length ratio result means that even the Z-plasty, which increase the scar length, was performed in cogwheel pattern patients, the final scar length would be shorter than fusiform group. Because in fusiform serial excision, the remnant edge of nevus should also be excised and additional scar length would be added. However, the scar length was not statistically significant. The normal tissue was more commonly excised in fusiform pattern and the difference is statistically significant (p < 0.05). After fusiform serial excision, the normal tissue was commonly excised in the middle portion of the nevus due to dumbbell shape. In contrast, cogwheel pattern serial excision leads the remnant mass to more suitable shape for complete excision. The dog ear deformity was seen more often in fusiform pattern excision and it was statistically significant (p < 0.05). Moreover, the scar length getting more longer when correction needed. Considering scar length and dog ear deformity together, the cogwheel pattern is more profit for serial excision.
13
Table 3. The Raw Patients Data of Two Serial Excision Method
Case Age (years) Long Axis (cm) Short Axis (cm) Long/short Axis Ratio Area (cm2) Scar (cm) Area/scar Ratio Normal Tissue Resection Dog Ear Deformity Satisfaction (number)
Fusiform type excision
1 11 4 2 2.0 6.3 5.0 5.02 O O 1 2 6 4 1.5 2.7 4.7 7.0 2.69 X O 3 3 37 2 1 2.0 1.6 2.5 2.51 X O 4 4 5 0.8 0.5 1.6 0.3 2.5 0.50 O O 4 5 13 10 4 2.5 31.4 12.0 10.47 O O 3 6 16 2.5 1.5 1.7 2.9 3.0 3.93 O O 4 7 15 3 2 1.5 4.7 6.0 3.14 X O 4 8 6 3.5 2 1.8 5.5 7.0 3.14 O X 3 9 10 6 3 2.0 14.1 8.5 6.65 X O 2 10 8 2 1 2.0 1.6 3.5 1.79 O X 4
14
Average 12.7 3..8 1.9 2.0 7.3 5.7 4.0 0.6 0.8 3.2
Cogwheel type excision
1 9 18.0 6.0 3.0 84.8 27.0 12.56 X O 4 2 1 2.0 1.0 2.0 1.6 3.5 1.79 X O 3 3 4 3.0 1.0 3.0 2.4 4.0 2.36 O X 3 4 4 9.0 5.5 1.6 38.9 12.0 12.95 X O 3 5 1 2.5 1.5 1.7 2.9 5.0 2.36 X X 4 6 7 2.0 1.3 1.5 2.0 3.0 2.72 X X 3 7 21 10.0 4.5 2.2 35.3 13.0 10.87 X O 4 8 4 1.5 1.0 1.5 1.2 3.0 1.57 X X 4 9 1 2.0 1.0 2.0 1.6 4.0 1.57 X X 5 10 2 4.0 3.0 1.3 9.4 7.0 5.38 O X 4 11 18 5.0 2.5 2.0 9.8 9.0 4.36 X X 4 Average 6.6 5.3 2.5 2.0 17.3 8.2 5.3 0.2 0.4 3.7
15
Table 4. The Average Measurement and Comparison Value
Fusiform
Cogwheel
p-value
Age (years)
12.7 ± 9.4
6.6 ± 6.9
-
Long axis(cm)
3.8 ± 0.8
5.3 ± 1.5
-
Short axis(cm)
1.9 ± 0.3
2.5 ± 0.6
-
Long/short axis ratio
2.0 ± 0.1
2.0 ± 0.1
0.993
Area(cm
2)
1)7.3 ± 2.9
17.3 ± 7.9
-
Scar(cm)
5.7 ± 1.0
8.2 ± 2.1
-
Area/scar ratio(cm)
4.0 ± 0.9
5.3 ± 1.4
0.446
Normal tissue resection (%)
60
20
0.049
Dog ear deformity (%)
80
40
0.044
Satisfaction(number)
3.2 ± 0.3
3.7 ± 0.2
0.173
16
Fig. 7.
The photograph of cogwheel pattern serial excision.
(A) One year-old girl has large congenital melanocytic nevus on her right buttock.
(B) Intraoperative photograph of cogwheel pattern design.
17
IV.
D
ISCUSSIONSerial excision was first introduced in plastic surgery in 1915 by Morestin.3 In the paper, he emphasized that all the incisions must lie inside of nevus to avoid unnecessary scars. A 1,948 paper described that serial excision should excise the medial and lateral portions of the nevus first.4 It is now well accepted by plastic surgeons that the nevus cells can migrate along the suture line, not considering the aesthetic aspect, incision line should be lie inside of nevus and final excision should containing minimal normal tissue.
The small congenital melanocytic nevus is found one in every 100 newborn infants and large congenital melanocytic nevus is found one in every 20,000 newborn infants.5 Even not considering the aesthetic aspect, excision is recommended before adolescence due to the possibility of malignancy.6 Among the available treatment modalities, serial excision and repair is the most preferred treatment when it is done in three stages.6
In elliptical shape excision, it is recommended that the lateral angle be less than 30 degrees and the optimal length-to-width ratio is 3–4.57. Practically, in younger age patients, the elasticity of skin is higher than for adults. So, in younger patients more tissue when be excised if mild dog ear deformity is acceptable.
The dog-ear deformity is influenced by many factors including wound shape, surface contours, tissue dynamics, and operation method.8-10 In dog ear deformity aspect, the long axis of the excision line should be three times that of the long axis11,12 of the mass, and the angle of the edge should be less than 30 degrees.13,14 However, long scar length cannot be avoided for decreasing dog ear deformity.15 So, the surgeon should design the incision line to balance the two complications. Using Z-plasty, a more acute angle excision line was available without dog ear deformity in cogwheel pattern excision. As a result, normal tissue resection and dog ear deformity were decreased simultaneously. We worried about scar length being longer than the previous fusiform pattern excision. But, the final scar length per area was shorter than the previous fusiform pattern excision, although the difference was not statistically significant. In addition, cogwheel pattern`s scar, Z-shape, is less visible than elliptical pattern`s linear pattern.
The elasticity of the skin is maximum during infancy (<2 years) and declines gradually thereafter.16,17 Subcutaneous fat layer is especially important in serial excision for planning
18
excision line due to dog ear deformity and suprafascial sliding. It has an early peak thickness of 6 months.18 Therefore, the optimal timing of surgery is from 6 months to 2 years old. As an anesthesia in children has been refined in the past few decades, our department strongly recommends patients to receive the operation in that age range. This can explain the age difference between the two groups.
There are several limitations in our study. First, we did not control the location of the nevus. Even though we excluded the patients who did not receive scar management, there can be a selective bias. Second, the patient`s age was not controlled. The cogwheel pattern group was 6 years younger than the elliptical group. Since skin elasticity and subcutaneous fat tissue are influenced by age, selective bias was possible.
Many excision patterns has been introduced recently, such as elliptical shape,19-20 banner flap,21 and S-shape.22 Recently, some serial excision patterns introduced such as cake flap23
and Ω-shape24 incision. A similar technique to the one we described is cake flap for serial excision. This pattern is similar to the cogwheel pattern in scar shape. However, our pattern does not divide mass for segment. Considering that the cogwheel pattern comes from combining the elliptical pattern and Z-plasty, our pattern is definitely different from other excision patterns.
19
V.
C
ONCLUSIONGenerally, Cogwheel pattern serial excision makes the congenital melanocytic nevus more suitable for total excision when long and short axis ratio is 2:1. Using a mathematical
calculation and retrospective study, it makes more acute angle resection in both lateral edges of the nevus, more area excised, and cause low dog ear deformity using Z-plasty. The normal tissue resection and dog ear deformity were statistically lower in traditional elliptical shape excision pattern.
20
R
EFERENCES1.Lee 1. Koot HM, de Waard-van der Spek F, Peer CD, Mulder PG, et al. Psychosocial sequelae in 29 children with giant congenital melanocytic naevi. Clin Exp Dermatol 2000;25:589-93. 2. Kang HG, Park MC, Park DH. A new modality for treating congenital melanocytic nevus:
"cogwheel pattern" serial excision method. Arch Plast Surg 2014;41:418-20.
3. Morestin H. La reduction graduelle des difformites tegumentaries. Bull Mem Soc Chir Paris 1915;41:1233.
4. Wilson JS. Serial excision as applied to a naevus of the cheek. Br J Plast Surg 1948;1:117. 5. Michel JL, Chalencon F, Gentil-Perret A, Fond L, et al. Congenital pigmented nevus:
prognosis and therapeutic possibilities. Arch Pediatr 1999;6:211-7.
6. Kruk-Jeromin J, Lewandowicz E, Rykala J. Surgical treatment of pigmented melanocytic nevi depending upon their size and location. Acta Chir Plast 1999;41:20-4.
7. Hudson-Peacock MJ, Lawrence CM. Comparison of wound closure by means of dog ear repair and elliptical excision. J Am Acad Dermatol 1995;32:627-30.
8. Weisberg NK, Nehal KS, Zide BM. Dog-ears: a review. Dermatol Surg 2000;26:363-70. 9. Zitelli JA. TIPS for a better ellipse. J Am Acad Dermatol 1990;22:101-3.
10. Zitelli JA. Tips for wound closure. Pearls for minimizing dog-ears and applications of periosteal sutures. Dermatol Clin 1989;7:123-8.
11. Borges AF. Dog-ear repair. Plast Reconstr Surg 1982;69:707-13.
12. Leshin B. Proper planning and execution of surgical excisions. In: Wheeland RG, editor. Cutaneous surgery. Philadelphia: W.B. Saunders; 1994. p. 171-7.
13. Bennett RG. Complex closures. In: Bennett RG, editor. Fundamentals of cutaneous
surgery. St. Louis: Mosby; 1988. p. 473-91.
14. Dunlavey E, Leshin B. The simple excision. Dermatol Clin 1998;16:49-64.
15. Grabb WC. Basic techniques in plastic surgery. In: Grabb WC, Smith JW, editors. Plastic
surgery (3rd ed). Boston: Little, Brown and Company; 1979. p. 3-8.
16. Feins NR, Rubin R, Borger JA. Ambulatory serial excision of giant nevi. J Pediatr Surg 1982;17:851-3.
21
17. Sugihara T, Ohura T, Homma K, Igawa HH. The extensibility in human skin: variation according to age and site. Br J Plast Surg 1991;44:418-22.
18. Paul AA, Cole TJ, Ahmed EA, Whitehead RG. The need for revised standards for skinfold thickness in infancy. Arch Dis Child 1998;78:354-8.
19. Stegman SJ, Tromovitch TA, Glogau RG. Ellipse. In: Stegman SJ, Tromovitch TA, Glogau RG, editors. Basics of dermatologic surgery. Chicago: Year Book Medical Publishers; 1982. p. 60-72.
20. Vistnes LM. Basic principles of cutaneous surgery. In: Epstein E, Epstein E, Jr., editors. Skin surgery (6th ed). Philadelphia: Saunders; 1987. p. 44-55.
21. Masson JK, Mendelson BC. The banner flap. Am J Surg 1977;134:419-23. 22. Liu H, Yu N, Shi J, Hu X, et al. A new modified S-plasty for skin defect closure. Aesthetic Plast Surg 2015;39:100-5.
23. Tang L, MacKenzie Ross AD, Nduka C. The Cake Flap: a new technique for serial excision of benign cutaneous lesions. J Plast Reconstr Aesthet Surg 2011;64:1194-6. 24. Iida N, Watanabe A. Usefulness of omega-shaped incision in skin tumor excision. Plast Reconstr Surg Glob Open 2014;2:e102.
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큰 양성 피부 병변을 갖고 있는 환자에게 톱니바퀴형 연속적 절
제술과 방추형 연속적 절제술 방법의 비교
아주대학교 대학원 의학과 최경범 (지도교수 :박동하) 큰 양성 종양이 피부에 있을 때 순차적 절제술, 조직 확장술, 절제 후 피부이식술 등 여러 방법을 시도해볼 수 있으나 그 중 순차적 절제술은 큰 양성 종양이 있을 때 시도해볼 수 있는 가장 간단하며 미용적으로 선호되는 방법이다. 하지만 절제술 후 아령 모양의 종괴가 자주 남으며 이것은 다음 절제술을 시행할 때 종양이 아닌 보통 피부를 제거해야 하고, 개 귀 변형을 초래하여 이 변형을 교정하는데 추가적 인 수술이나 불필요한 긴 흉터가 남게 된다. 2013년도에 고안된 톱니바퀴형 절제술 은 이와 같은 부작용을 줄이기 위해 고안되었으며 그 도안과 효과에 대하여 연구를 진행하였다. 먼저 수학적인 도안과 그 효과에 대하여 검토하였다. 이론적으로 원추형의 절제 술은 가로와 세로의 비율이 각각 3:1의 비율로 이루어지게 된다. 하지만 실제적으 로 피부의 장력이 심하지 않은 경우 약 2:1의 비율로도 절제술이 이루어 진다. 이 때 피부의 장력이 같다고 가정한 뒤 절제할 수 있는 면적을 비교한 결과 톱니바퀴 형 절제술에서 한번에 더 많은 조직을 절제할 수 있었으며 이는 연장술과 함께 양 쪽 끝에서 일반적인 절제술보다 더 높은 각도의 절제술을 시행할 수 있기 때문이었 다. 2010년부터 2013년도 사이에 본원에서 순차적 절제술을 한차례 시행 받고 전 절 제술을 시행받은 사람들을 대상으로 연구를 진행하였다. 기존의 절제술 또는 톱니 톱니바퀴형 절제술을 받은 42명의 환자를 선별하였으며 의무기록과 사진을 통해 결과를 수집하였으며 만족도와 같은 주관적인 평가는 외래 방문이나 그것이 어려운 경우 전화를 이용하여 집계하였다. 모반의 장축, 단축, 개귀 변형, 흉터의 늘어남과23 길이, 만족도 등을 조사하였다. 양성 종양의 장축과 단축의 비율은 1:2 정도로 두 그룹에서 거의 차이가 없었으며 이것은 두 그룹의 비교를 가능하게 하는 전제 조건이 성립하였음을 의미한다. 다른 결과를 비교한 결과 중간에 피부를 절제한 경우와 개귀 변형 두가지 결과에서 통계 적으로 유의한 차이를 보였으며 흉터 길이당 절제한 면적 및 만족도에서 톱니바퀴 연속적 절제술이 더 좋은 결과를 보였으나 통계적으로 유의한 차이를 보이지는 않 았다. Z-성형술은 길이를 연장시키는 술기로 아직까지 연속적 절제술과 함께 쓰인 적 이 없으며 톱니바퀴형 절제술은 이를 이를 이용하여 더 많은 면적을 절제하고 다음 절제술에 유리한 모양을 남기면서 절제를 할 수 있다. 아령 모양의 종괴가 남는 경 우 당연히 중간의 정상 피부를 절제해야 하며 이에 따른 흉터의 장력이 심하게 가 해져 흉터가 늘어나게 된다. 연속적 절제술은 2번 이하로 시행할 경우 피부이식술 이나 다른 술기에 비해 미용적인 결과가 뛰어나며 주변 조직으로 재건하여 이질감 을 들지 않게 하는 술기이다. 짧고 변형이 적은 흉터를 남기면서 종양을 절제하는 것이 이의 핵심이며 위의 관점에서 보았을 때 톱니바퀴형 연속적 절제술은 기존의 절제술에 비해 뛰어난 방법이라고 볼 수 있다.
