Surgical staplers: toy or tool?

Surgical staplers may be used in a wide variety of skin, abdominal, thoracic and other veterinary surgical procedures. This article provides an overview of the applications of surgical stapling in small animal veterinary practice, and describes the various types of surgical staplers used in veterinary surgery and how to operate them.


Advantages
The proposed advantages of surgical staplers over manual suturing include: ■ Reduction of surgical time (operative and anaesthetic); ■ Reduced tissue trauma/manipulation; ■ Reduction or elimination of surgical contamination by intestinal contents; ■ Easy and secure closure of large vessels, vascular pedicles, and gastrointestinal, lung, liver and splenic tissue. However, use of a surgical stapler does not compensate for inadequate surgical technique. The basic principles of soft tissue surgery (Halstead's principles) and the principles of application of surgical staplers must be followed: ■ Do not staple tissue that is inflamed, oedematous or not viable; ■ Every staple must penetrate all the layers of the tissue; ■ Choose the correct staple size -in particular, the tissue must not be too thick or too thin for the closed staple to hold it securely; ■ Do not place excessive amounts of tissue in the stapler; ■ Inspect the tissue before firing to ensure it is correctly aligned within the stapler and that no other tissue is caught up in the stapler; ■ Carefully remove the stapler after firing so as not to disrupt the staple or staple line; ■ Inspect the staple or staple line for haemorrhage, leakage or loose staples (especially at both ends of a staple line).

Linear staplers
Linear staplers are also known as thoracoabdominal (TA) staplers (Fig 1). They consist of a long handle with a pistol-type grip, and a 'U-shaped' end into which the tissue to be stapled is inserted. Re-usable (stainless steel) or semi-disposable linear staplers are available in lengths ranging from 30 mm to 90 mm, and the surgeon chooses the length that will easily include all the tissue to be stapled. If there is doubt about what length to use, it does not matter if the staple line is too long (residual staples just fall away), but trying to put too much tissue into too small a stapler is not recommended. Vascular pedicles and stumps may be closed with a 30 mm cartridge.
Re-usable (stainless steel) linear staplers can be autoclaved. Semi-disposable linear staplers may be sterilised in ethylene oxide or hydrogen peroxide gas plasma and used a limited number of times (manufacturers often recommend re-use up to six times but the staplers may function well many more times than this).
A linear staple cartridge (Fig 2) consists of the staples and an opposing anvil against which the staples are fired. A retaining pin ensures the correct amount of tissue is placed, aligned correctly and kept within the jaws of the linear stapler during firing.
A linear stapler fires two or three (Fig 3) staggered rows of titanium staples. The staggered rows and inverted 'B' shape staple configuration (Fig 4) after firing are designed to secure the tissues and achieve haemostasis, while still allowing blood flow through the microcirculation so that the tissue beyond the staple line does not become necrotic.
Having chosen the length of linear stapler (30 mm to 90 mm) required for a particular situation, the surgeon matches this by choosing a disposable cartridge of the same length.
The surgeon must also match the thickness of the tissue to be stapled with the closed height (Fig 4) of the staple cartridge: ■ Standard (blue) staples close tissue to a height of 1.5 mm. These are often used in small and large intestinal tissue, for example. They may be used in thicker areas of liver and lung tissue, but the staple line should be carefully inspected and the surgeon should be prepared to deal with any residual haemorrhage or air leakage. These staples may also be used in the stomach if it is not too thick to be adequately compressed; ■ Thick (green) staples close tissue to 2 mm and are used in the stomach, for example; ■ Vascular/thin (white) staples close tissues to a height of 1 mm and have the increased security of three rows of staggered staples (only available for 30 mm cartridges). These staples can be used in the spleen, liver and lung, for example, and for vascular pedicles, such as the bronchus and hilar vessels during complete lung lobectomy.
To operate a linear stapler: ■ Compress the tissue by closing the approximating lever; ■ If placement is unsatisfactory the approximating lever can be opened and re-closed; ■ If the approximating lever cannot be closed easily then the tissue is too thick to be stapled (most semidisposable staplers have markers on the approximating lever which, when lined up, confirm full compression of tissue); ■ Release the safety lever; ■ Squeeze the handle firmly to fire the stapler; ■ The edge of the cartridge unit can be used as a guide for resection of the tissue beyond the stapler using a scalpel before the stapler is released and removed (Fig 5d and Fig 6b); ■ Inspect staple lines carefully, especially liver or splenic tissue for haemorrhage and lung tissue for air leakage (Fig 7); ■ Test stapled complete and partial lung lobectomies for leaks by filling the thoracic cavity with sterile saline, as is done for a manually sutured lung lobectomy. Linear staplers are extremely versatile. Linear and linear cutter (see below) staplers may be used interchangeably in many situations ( Fig 5). Sometimes, the very different shape of the linear versus linear cutter stapler dictates which is easiest to manoeuvre and position for a particular use. All other things being equal, linear cutter staplers/cartridges are usually slightly more expensive than linear staplers/cartridges. Applications of linear staplers include: ■ Closure of the intestinal ends in the final stage of a functional end-to-end anastomosis procedure ( Fig  8d); ■ Partial gastrectomy ( Fig 5); ■ Gastropexy; ■ Partial (Fig 9) or complete (Fig 7) lung lobectomy. En bloc stapling of the bronchus and hilar vessels with a vascular cartridge is regarded as safe, but occasionally the hilar vessels may need additional sutures; ■ Partial (Fig 6) or complete liver lobectomy; ■ Partial splenectomy (the hilar vessels of the spleen should not be incorporated in a stapled partial splenectomy); ■ Rectal tumour excision following a rectal eversion approach; ■ Typhlectomy; ■ Partial pancreatectomy; ■ Partial prostatectomy; ■ Excision of prostatic cysts; ■ Closure of the vascular pedicle, for example, during nephrectomy; ■ Resection of right atrial appendage tumours.

Linear cutter staplers
Linear cutter staplers are also known as gastrointestinal anastomosis or intestinal linear anastomosis staplers (Fig 10). They consist of two, straight interlocking 'arms', one of which accepts the staple cartridge containing the staples and a bisecting blade. Sterilisation and reuse are the same as for reusable and semi-disposable linear staplers (see above).
A linear cutter stapler fires four rows of staggered, inverted B-shaped, titanium staples and the blade divides between rows two and three. The incision made by the blade stops 8 mm before the end of the staple line (Fig 11).
Linear cutter staplers are available in lengths ranging from 50 mm to 100 mm. The surgeon chooses the length that will easily include all the tissue to be stapled. If the tissue to be stapled is very long then multiple cartridges may be used, but all the staple lines must overlap each other (Fig 5). It is also recommended that a stapled partial gastrectomy performed for resection of a necrotic stomach during gastric dilalation-volvulus surgery is oversewn with a manual, continuous, inverting suture pattern; this is in order to provide additional security in case there is unseen gastric mucosal necrosis that could compromise the staple line, despite the gastric serosa appearing viable.
As for linear staplers, the surgeon must match the thickness of the tissue to be stapled with the closed height of the linear cutter staple cartridge: ■ Standard (blue) staples close tissue to a height of 1.5 mm; ■ Thick (green) staples close tissue to 2 mm; To operate a linear cutter stapler: ■ Place each arm on either side of the tissue to be divided; ■ Lock the two arms together (an audible click confirms that the lock lever is fully closed); ■ The lock lever can be released to allow repositioning; ■ If excessive force is required to lock the two arms around the tissue then the tissue is too thick to be stapled; ■ There is no retaining pin so the surgeon must ensure the tissue in the stapler does not extend beyond the length of the staple cartridge; ■ Slide the push bar handle fully forward and then fully back (Fig 5a); ■ Uncouple and remove the stapler.
Linear cutter staplers may be used for: ■ Partial gastrectomy ( Fig 5); ■ Functional end-to-end anastomosis of intestine ( Fig  8); ■ Partial lung lobectomy (Fig 12); ■ Partial liver lobectomy; ■ Resection of oesophageal or rectal diverticulae; ■ Prostatic cyst resection; ■ Typhlectomy; ■ Side-to-side anastomosis of small intestine to stomach (eg, Bilroth II surgery). Functional end-to-end anastomosis of intestine ( Fig  8) is quick to perform with stapling equipment and is most useful for critically ill patients, for example, those with septic peritonitis. Complication rates for animals receiving a stapled functional end-to-end anastomosis compare favourably with manually sutured anastomoses. Strictures following stapled functional end-to-end anastomoses are not encountered because the stoma created is larger than the original intestinal lumen, and luminal disparity is irrelevant.

Circular staplers
Circular staplers are more technically demanding to use and have much more limited application in small animal veterinary surgery than other staplers. They consist of a long handle with a central rod at the end, on to which inserts a circular staple cartridge with a circular blade. A dome-shaped anvil screws onto the central rod after it has passed through the staple cartridge. They can only be used if the bowel lumen is big enough to accept the available sizes of circular stapler; access to the colon or rectum within the pelvic canal may be difficult in cats and male dogs with small and/or narrow pelvic canals.
Circular staplers fire two staggered, circumferential rows of titanium B-shaped staples full thickness through each inverted gastrointestinal wall and cut two circular segments of redundant gastrointestinal tract tissue ('doughnuts') from each end to produce a two-layer, inverting anastomosis (Fig 13). Readers are referred to the articles listed in the 'Further reading' section below for detailed descriptions of circular staplers and how to operate them. Circular staplers may be used for end-to-end anastomoses in the gastrointestinal tract -usually distal colonic or proximal rectal anastomoses -using a combined transrectal and laparotomy approach. They are most useful for excision of colorectal masses that cannot be manually anastomosed via a single laparotomy, rectal pull-through or dorsal approach because there is insufficient room due to the mass being too large and/or located too far within the pelvic canal.
Anastomoses using circular staplers are reported to save time without increasing the risk of postoperative dehiscence. Strictures are a frequent complication following the use of circular staplers due to the inverting nature of the anastomosis.

Ligate and divide stapler
The ligate and divide stapler (LDS) has a handle in the shape of a pistol (Fig 14). It places two U-shaped staples around a vessel and divides the tissue between them (Fig 15). Re-usable (stainless steel) or semi-disposable LDS staplers accept disposable cartridges containing titanium staples.
To operate an LDS: ■ Place the vessel or vessels to be ligated within the C-shaped jaws of the stapler; ■ Fire the stapler by squeezing the handle; ■ Keep the LDS steady when firing because movement during application can tear the vessel; ■ Vessels up to 7 mm wide that can be compressed to less than 0.75 mm can be safely secured; ■ The tissue should be thick enough for the staple not to slip on the pedicle, but excessive tissue should not be forced into the jaws of the stapler -as an approximate guide, the vessel/tissue pedicle should measure between one-third to two-thirds of the staple width; ■ Vessels that require double ligation (eg, major arteries and veins such as the splenic artery and vein) must have an additional single staple or ligature applied before the stapler is used; ■ There is a safety mechanism that prevents firing of the stapler when the cartridge is empty. LDS staplers save the surgeon considerable time during procedures that require multiple vessel ligations (eg, splenectomy [Fig 16], resection of omental adhesions), and their use is associated with minimal complications.

Vascular clip applicators
Vascular clip applicators place a metallic V-shaped clip around a vessel. They have a long handle with a scis- sor-type grip (Fig 17). There are many clip applicators available that have different features including: ■ Number of clips they hold; ■ Size of clips available; ■ Whether the device holds multiple clips which automatically replace at the tip on firing, or whether single clips are manually loaded into the device after every use; ■ Whether the clips have a locking mechanism for increased security; ■ Whether the devices are single use or may be reloaded with additional cartridges; ■ Whether they can be re-sterilised and by what method; ■ What the staple is made of (titanium, stainless steel or absorbable material). Variations in these features will affect whether a particular vascular clip applicator is suitable for a particular surgical use and/or is cost-effective for an individual veterinary practice. The most useful and economic choice for veterinary surgery is usually a device that holds multiple clips (eg, 10 to 20), allowing rapid and easy application during surgery, and can be re-sterilised until all the remaining clips have been used.
To operate a vascular clip applicator: ■ The vessel must be adequately dissected and exposed so that the clip can be applied accurately and enough tissue (2 mm to 3 mm) can be left beyond the clip to prevent slippage; ■ Squeeze the handles firmly to secure the staple in place; ■ Release the jaws carefully so as not to disturb the staple during removal; ■ The vessel width should not exceed one-half to three-quarters of the vascular clip width. Vascular clips can be used in place of suture liga-tures in most surgical situations. They are particularly useful when: ■ Surgical access is limited; ■ Suture ligatures are difficult to apply; ■ Surgery requires the application of many vessel ligatures, eg, tumour excision; ■ Oncological surgery requires postoperative imaging of the clips to help with postoperative radiation treatment planning. Stainless steel clips can be used as radio-opaque surgical markers but titanium clips are even more useful as markers because they do not interfere with postoperative computed tomography (CT) or magnetic resonance imaging (MRI) studies.
Vascular clips have few drawbacks but great care must be taken using them because they are more easily dislodged than traditional ligatures.

Skin staplers
There are many different designs of skin staplers, but those typically used in veterinary practice have a palm grip, fixed head and stainless steel staples (Fig 18) because these are easy to use and cost effective. The ideal properties of palm grip, fixed head skin staplers include: ■ Audible click to confirm staple formation is complete; ■ Staple counter; ■ Easy staple alignment (low profile head, open, clear nose piece with distinct arrows, pre-cock mechanism); ■ Secure staple placement (firm attachment to skin, no rotation); ■ Good staple depth control; ■ Easy staple removal.
The above ideal skin stapler properties have been compared for various skin stapler brands in an experi-  mental dog cadaver study (Smeak and Crocker 1997).
Most skin staplers are manufactured to be single use, but in practice they may be re-sterilised using ethylene oxide or hydrogen peroxide gas plasma without any significant decrease in function, until all the preloaded staples in the unit have been utilised. Skin staples are usually between 5 mm and 7 mm wide, depending on the manufacturer and whether a regular or wide staple width has been selected. Skin staples form a rectangle shape when fired into the closed position. Table 1 lists the advantages and disadvantages of skin staplers.
To operate a skin stapler: ■ As for skin sutures, all the wound tension should be borne by the underlying tissues and not the skin staples. This is best achieved with an intradermal suture pattern, which places the skin edges in close apposition producing an ideal wound for skin stapling. This is a critical step, and skin wounds closed with staples but without appropriate suturing of the underlying tissues are less secure and will be at increased risk of wound breakdown and/or infection; ■ If the skin edges are not perfectly aligned they may be held together with thumb forceps to facilitate accurate placement of the skin staple (Fig 19); ■ The skin stapler should be placed directly perpendicular to the skin incision to optimise apposition of the skin edges (Fig 19); ■ As with skin sutures, a gap should be left between the wound and the skin staple to allow for postoperative swelling; ■ Skin staples should be placed approximately 0.5 cm to 1 cm apart (Fig 20); ■ Skin staples need to be removed using a staple remover (Fig 21). In addition to skin wound closure, skin staplers have been used to attach skin grafts, close gastrotomy and enterotomy wounds, and perform intestinal anastomoses. They may also be used in a wide variety of situations to secure drains, dressings and tubes to animals.

Conclusion
Surgical staplers save time during surgery without increasing the risks, which is most beneficial for criti- cally ill animals. There are some surgeries where the use of staplers is now the preferred method, such as for partial and complete liver and lung lobectomies. Complication rates following the use of stapling devices are low providing they are applied correctly by a surgeon trained in their use, using good surgical judgement. The two main manufacturers of stapling products worldwide are Autosuture (Covidien) and Ethicon (Johnson & Johnson); the individual distributors of these products in the UK should be contacted for current recommendations on all available products, details of specific product dimensions, their indications and limitations.