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Definition

The most common complications associated with the incision for bone graft harvest include incisional infection, seroma, and drainage with peri‐incisional edema [3, ]. Incisional dehiscence may result in osteomyelitis, particularly when the sternum and proximal tibia are used as donor sites [13].

Risk factors

Harvest site location

Pathogenesis

Case selection in the bone graft harvest site is important in minimizing complications. Several donor sites for cancellous bone grafts in the horse have been described, principally the tuber coxae, sternum, rib, proximal medial aspect of the tibia, and proximal humerus, each with its advantages and disadvantages, which are summarized in Table 10.1 [3, 12, 14–17]. Similar amounts of cancellous bone may be obtained from the sternum, tuber coxae, tibia and humerus, while the rib yields smaller quantities in comparison [2, 17].

Case‐specific factors dictate intraoperative access to the donor site, amount of graft material required, as well as other case‐specific factors including pre‐existing soft tissue trauma or decubital ulcers [12, 16, 17].

Utilization of the sternum as a graft donor site is associated with minor complications, including peri‐incisional edema, serum exudate, and wound dehiscence due to the ventral location and tension [16].

Incisional dehiscence, which may result in osteomyelitis, is reported, particularly when the sternum and proximal tibia are used as donor sites due to tension and location [13].

Prevention

Location of the donor site is selected based upon the location of the surgical site and therefore anesthetic recumbency selected, which dictates intraoperative access to the site and amount of graft material required. While multiple donor sites may supply an adequate quantity of bone graft material, each donor site carries its own risks and benefits in terms of early postoperative sequellae. Donor site selection is made after taking into account the known risks associated with each site as well as case specific factors such as location of the lesion, soft tissue trauma or presence of decubital ulcers. Whenever possible, avoiding sites at greatest risk of complication is recommended (Table 10.1 ).

Adherence to aseptic technique is advised to reduce morbidity associated with the bone graft donor site incision. The sternum and tibia have also been reported to be more prone to dehiscence due to tension in these areas during anesthetic recovery, and so avoidance of these sites as donor sites for bone graft harvest may reduce incisional site complications.

Diagnosis

Incisional infection, seroma, or edema is diagnosed by clinical examination with evidence of drainage or swelling at the incision site.

Monitoring

Monitor the graft donor incision site for increased drainage, swelling or dehiscence that may indicate seroma formation or infection. Complete integration of the bone graft into host tissue may take years [9]. Autogenous cancellous bone grafting enhances and stimulates bone healing, and utilization of bone grafts in long bone fracture repair should decrease fracture repair failure as a result of implant fatigue.

Treatment

Incisional infection or seroma at the donor site may be treated successfully with facilitated drainage of the incision site and antimicrobial therapy.

Expected outcome

Incisional complications, such as incisional infection, seroma, and drainage with peri‐incisional edema or superficial incisional infection, are usually self‐limited and carry a good prognosis [3, 12, 13]. Osteomyelitis is a more serious condition but usually responds well to local debridement and antimicrobial therapy.

Table 10.1 Summary of bone graft donor sites

Donor Site	Advantages	Disadvantages
Tuber coxae [2, 23, 17]	Provide ample grafting materialGood visualization for surgical approachLow rate of postoperative incisional complicationsRemains the most commonly used donor site	Time‐consumingRequires patient in lateral recumbencyDecubital ulcers or soft tissue trauma over the tuber coxae may preclude its use
Sternum [16, 21, 37, 38, 39]	Use in cases where patient in dorsal recumbencyReduces risk of pathological fracture associated with harvesting from the tibia and humerusAbsence of skin tension and dependency of this location facilitates drainage if incisional infection or dehiscence occurCancellous bone obtained is equivalent in amount and microscopic appearance to that obtained from other sites such as the tuber coxae, proximal tibia, and ribNo instability or fractures of the sternum have been reported, even when more than one sternebra is accessed in order to obtain the desired amount of cancellous bone	Risk of puncturing thoracic or pericardial cavities exists
Tibia [12, 19]	May be accessed with patient in dorsal or lateral recumbencyUseful in cases where smaller amounts of graft material (<50 ml) are required, such as in arthrodeses, bone cysts or acute fractures	Risk of pathologic fracture on anesthetic recovery has been recognized
Humerus [3]	Greater soft tissue coverage and muscular support may reduce potential for incisional complications and help to dissipate torsional forces exerted on the bone during recovery from general anesthesia	Catastrophic fracture during recovery from anesthesiaMild to moderate incisional swelling and edema
Rib [25]	Bone obtained from transcortical rib biopsies was reported to be superior in quality to unicortical biopsies in terms of histomorphometry	Pneumothorax or hemothorax
Fourth coccygeal vertebra [15]	Provides large quantity of cancellous boneAccessible with the patient in dorsal or lateral recumbency	Use of this site requires tail amputation
Periosteum [15]	Transplantation of periosteum as a source of osteoprogenitor cells may enhance bone healing as donor tissue with good osteogenic propertiesEquine tibial periosteum was examined in vitro for its osteogenic and osteoprogenitor characteristicsUse of autogenous tibial periosteum in human cartilage repair techniques reportedly did not result in morbidity associated with donor site	Periosteum as an alternative donor source in bone grafting warrants further investigation in vivo in the equine patient.