Inservice Exam - 2005
Skin Grafts

Which of the following is the best donor site for delayed multiple harvesting of split-thickness skin grafts?

(A) Back
(B) Lateral forearm
(C) Medial arm
(D) Medial forearm
(E) Medial thigh

The correct response is Option A.

The selection of a donor site depends largely on donor site morbidity and skin thickness. The back provides a nearly ideal donor site for repeated harvesting of split-thickness skin grafts and has large areas of thick skin available for harvesting. The lateral forearm exhibits unacceptable donor site morbidity. The medial arm, medial forearm, and medial thigh have skin of insufficient thickness to allow multiple harvesting.

The number of times that a donor site can be harvested for split-thickness skin grafts is limited by the thickness of the dermis at the site. A split-thickness skin graft includes the epidermis and part of the dermis. The donor site of a split-thickness graft heals by migration from the remnant epithelia of the dermal appendages, such as hair roots and sweat and sebaceous glands. Therefore, the epidermis regenerates but the dermis does not. A repeat split-thickness graft may be harvested once the skin has reepithelialized, but a thinner dermis will remain at the donor site.

References:
1. Hardesty RA, Herber SC, Place MJ. Basic technique and principles in plastic surgery. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith’s Plastic Surgery. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 1997:13-26.
2. Rudolph R, Ballantyne DL Jr. Skin grafts. In: McCarthy JG, May JW, Littler JW, eds. Plastic Surgery. Vol 1. Philadelphia: WB Saunders; 1990:221-274.



Which of the following bone grafts exhibits the greatest inductive capacity?

(A) Allogenic
(B) Autologous cancellous
(C) Autologous cortical
(D) Free vascularized
(E) Xenogenic


The correct response is Option B.

Cancellous bone grafts have the greatest inductive capacity (ability to stimulate the formation of new bone) because they contain bone morphogenic proteins that stimulate bone growth. Cortical bone grafts and allogenic and xenogenic grafts have less inductive capacity. Free vascularized bone grafts have no inductive capacity because they do not rely on stimulating new bone formation.

References:
1. Lee WPA, Butler PEM. Transplant biology and applications to plastic surgery. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith’s Plastic Surgery. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 1997:27-35.
2. Bishop AT. Vascularized bone grafting. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green=s Operative Hand Surgery. Vol 2. 4th ed. New York: Churchill Livingstone, 1998:1221-1250.



Which of the following is an advantage of using the dermal regeneration template (Integra) instead of a thin split-thickness autograft for reconstruction of the hand?

(A) Elimination of donor site
(B) Improved cosmesis
(C) Increased wound contraction
(D) Reduced risk of hematoma
(E) Shorter healing time


The correct response is Option B.

The advantages of Integra include the availability of large quantities, the simplicity and reliability of the placement technique, and the pliability and cosmetic appearance of the resulting cover.
Integra does not eliminate the use of a donor site. However, the skin graft used at the second stage is typically thinner than that used in single-stage grafting, so Integra does avoid the use of a deep donor site, which decreases the risk of infection, scarring, and permanent pigment changes.


Wound contraction with Integra is typically less than that with single-stage split-thickness skin grafting. Compared with autologous skin, Integra purportedly has no decrease in the hematoma rate. In one study, the incidence of hematoma under Integra was 9 out of 39 cases. Because Integra requires a second surgery after 3 to 4 weeks for coverage with a thin split-thickness skin graft, it has a longer healing time until final wound coverage.


References:
1. Dantzer E, Braye FM. Reconstructive surgery using an artificial dermis (Integra): results with 39 grafts. Br J Plast Surg. 2001;54(8):659-664.
2. Palao R, Gomez P, Huguet P. Burned breast reconstructive surgery with Integra dermal regeneration template. Br J Plast Surg. 2003;56(3):252-259.




Which of the following grafts has minimal resorption and loss of volume?

(A) Bone
(B) Cartilage
(C) Macro-fat
(D) Micro-fat
(E) Muscle

The correct response is Option B.
Although all of these tissues may be used for grafts, autologous cartilage grafts offer minimal resorption and loss of volume and provide good results in many clinical settings. The metabolic rate of cartilage is 1/100 to 1/500 the rate of other human tissues. It has low glycolytic activity and consumption because of its small cell population and relative isolation by the cartilage matrix. This isolation helps protect cartilagenous tissue from resorption. Readily accessible sites for cartilage grafts are the septum, auricular cartilage, and ribs.

Bone grafts, which depend on the size of the bone, have variable resorption rates based on the clinical circumstance. Macro-fat grafts are usually unreliable. They have high resorption rates and are more effectively used as dermal fat grafts to minimize resorption and fibrosis. Given by lipoinjection, micro-fat grafts may exhibit greater longevity than macro-fat grafts. However, their resorption may be 25% to 50% of the injected volume. Muscle grafts are not routinely used. Rather, vascularized muscle flap grafts are preferred for transferring muscle tissue.

References:
1. Lee WPA, Butler PEM. Transplant biology and applications to plastic surgery. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith’s Plastic Surgery. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 1997:27-38.
2. Brent B. Repair and grafting of cartilage in perichondrium. In: McCarthy JG, May JW, Littler JW, eds. Plastic Surgery. Vol 1. Philadelphia: WB Saunders; 1990:559-582.




Which of the following bone grafts does NOT rely on creeping substitution as a mode of remodeling?

(A) Allogenic
(B) Autologous cancellous
(C) Autologous cortical
(D) Free vascularized
(E) Xenogenic

The correct response is Option D.


Free vascularized bone grafts do not rely on creeping substitution (replacement of necrotic bone with osteoblasts and new vascular ingrowth) for remodeling. They do not need to stimulate new bone formation because they are used when little or no bone has been lost.


All nonvascularized bone grafts undergo a degree of resorption and remodeling, including creeping substitution, and have some degree of inductive capacity (ability to stimulate new bone formation). Cancellous bone grafts contain bone morphogenic proteins that stimulate the formation of new bone. Cortical bone grafts and allogenic and xenogenic grafts have less of this inductive capacity.


References:
1. Lee WPA, Butler PEM. Transplant biology and applications to plastic surgery. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith=s Plastic Surgery. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 1997:27-35.
2. Bishop AT. Vascularized bone grafting. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green’s Operative Hand Surgery. Vol 2. 4th ed. New York: Churchill Livingstone, 1998:1221-1250.