bone grafts

الرجل البخاخ

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Autogenic bone transfer is quite commonly required in maxillofacial surgery.
Reconstruction of cleft related defects, of the facial skeleton after ablative cancer surgery and after trauma are the most frequent reasons for bone grafting.
Sources of bone
1. Anterior superior iliac crest (ASIC). Cortical plate, chips or fragmented cortical bone or cancellous bone may be harvested from the ASIC. Cancellous harvest is required for closure of alveolar clefts, cleft related oronasal and oroantral fistulae. Cortical bone may be
harvested in good quantity for a wide range of uses including atrophic ridge augmentation, sandwich ostetomies and impaction grafting into titanium mesh preformed trays in mandibular segmental reconstruction. The technique involves a 2-3 cm incision over the crest and dissection to the subperiosteal plane or subperichondrial plane in children. A ‘coffin lid’ elevation raised on the medial aspect permits access to the cancellous bone.
Trephine excision is also possible. Cortical bone may be harvested from the outer table. Pre-excisional implantation of osseointegrated implants is possible.
Closure in layers using a vacuum drain and infusion of bupivacaine for analgesia permits early postoperative
mobilisation.
2. Posterior superior iliac crest (PSIC).
A largerquantity of bone may be harvested from this site than ASIC.
Its disadvantage is that intraoperative turning of the patient is required. Operative approach is similar to that described for ASIC harvest.
3. DCIA flap.
Vascularised iliac crest bone may be harvested pedicled on the deep circumflex iliac arterial system. Muscle and skin are available and may be
raised in continuity. The form of the anterior crest is near ideal for reconstruction of the mandibular angle.
4. Tibia.
In children, cancellous bone may be harvested by trephine from the lateral aspect of the tibial plateau. Adequate quantities of bone for grafting a cleft alveolus are available. Early mobilization is possible and the morbidity of this approach is reportedly less than with an ASIC approach.
5. Calvarilrm.
Calvarial bone may be used toreconstruct orbital floor defects, palatal dehiscences and if full thickness skull is harvested, segmental mandibular defects may be repaired. Pedicled calvarial bone grafts may be raised on a superficial temporal arterial pedicle with temporalis muscle. Calvarial bone fragments may be harvested also.
6. Fibula.
A source of vascularized bone for freetissue-transfer as a myofasciocutaneous flap pedicled on branches of the anterior tibial artery. Preoperativeangiography to demonstrate patent vessels in the peroneal and posterior tibial distribution with good distal run-off must be available. The bone harvested can be osteotomized to allow curvature appropriate for mandibular reconstruction.
7. Radius.
The myofasciocutaneous free forearm flapis well described.
A unicortical segment of radius maybe harvested in continuity to provide vascularized bone.
For mandibular reconstruction it is not as good as fibulaor DCIA flaps. Radial fracture is a troublesomecomplication.
8. Scapula.
Free scapula flaps permit harvest ofappropriate shaped and textured bone for intraoral reconstruction. Skin, muscle and facia are also available in good quantities.
9. Rib.
Rib may be harvested in continuity with apectoralis major or latissimus dorsi flap. Its survivaldepends on the harvest of an adequate degree of muscle covering. Vascularized rib flaps may also be harvested.
10. Clavicle.
The clavicular head of sternomastoid maybe raised in continuity with a section of clavicle.
Mandibular reconstruction is possible.
11. Perioral.
Palatal and mental mandibular bone isavailable in small quantities for closure of small alveolar defects.
12. Prosthetic tissues and xenografis.
Hydroxyapatite,reptilian kiel bone and lyophilized bone are aalvl ailable but are less commonly used as the problems of infection and graft failure are high.
Uses
Alveolar bone grafts
Alveolar clefts may be grafted. Cancellous bone isrequired and all traces of cortical bone and cartilage must be removed. Impaction of grafted bone is performed by some and good adaptation to the cleft margins once dissected free of all soft tissue and scar tissue is necessary. Firm mucoperiosteal cover over the graft site must be achieved and various flap des-igns have been designed to ensure this. Most are modifications of the Burrion flap.The advantages of the grafted cleft alveolus are principally that of uniting of the cleft segments and provision of bone through which the permanent canine may erupt. Subsequent maxillary osteotomy is likelyt o be easier if previous bone grafting has been performed.
Fistulae
Oroantral fistulae rarely require bone grafting with theexception of cleft related fistulae. Many of these are post-palatal closure and closure of a residual
communication is associated with a high rate of failure.
Oronasal fistulae are almost all found in cleft patients.
Grafting is often better performed using a soft tissue flap.
Galea1 flaps are often proposed for this role. Bone is less commonly required but clavarial bone is a useful source if required.
Mandibular reconstruction
Many methods of segmental reconstruction aredescribed.
Free or vascularized rib, clavicle,vascularized iliac crest, free fibula, corticocancellous fragments in titanium mesh or Dacron trays are allproposed.
Palatal resonstruction
Post maxillectomy reconstruction is debated as theclassical rehabilitative treatment is obturation. The opponents of reconstruction suggest that tumour recurrence will be missed if the palatal shelf is reconstructed and the cavity is not readily visualized. Nevertheless bone grafts using calvarial or iliac bone
are described. Vascularized bone is considered to be better than non-vital bone grafting.
Othognathic surgery
Augmentation genioplasty, sandwich osteotomies andonlay grafts are all described. Cortical bone blocks areused and harvested from iliac crest or outer table of
skull.
Preprosthetic surgery
In preparation of the mouth for osseointegrated implantssinus mucosal lifts via a Caldwell Luc operation and submucosal grafting increases the effective depth of the
maxillary alveolus and so permits implant placementwhere it would previously not hav be een possible.
Adjuncts
Analgesia
After harvest of iliac crest bone, the pain and morbidity
can be considerable. Fan blocks using local anaesthetic
or
insertion of an epidural catheter into the wound for
continuous infusion of local anaesthetic are good
methods of painc ontrol.
Biomaterials
Titanium mesh trays
or Dacron for use of fragmented
cortical grafts are described. Impaction grafting into
preformed titanium mesh trays is becoming a popular
technique in some centres.
Medical problems
Prevention of fractures with radial bone harvest and
prevention of thromboembolic problems may be
important depending on the preoperative medical status
of the patient. Therefore TED stockings, anticoagulant
use, limb splints, postoperative physiotherapy are all of
use.
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