Cartilage grafts

CARTILAGE GRAFTS

1. Cartilage grafts Cartilage is a kind of connective tissue which is mainly composed of chondrocytes and their extracellular matrices (ECM) of type II collagen fibers, proteoglycans, and elastic fibers .

2. According to its composition , cartilage can be classified into three types: hyaline cartilage; fibrocartilage; and elastic cartilage.

3. Hyaline cartilage is the most common type of cartilage and can be found in costal, articular, tracheal, and nasal cartilage.

4. Fibrocartilage is composed of bundles of thick collagen fibers, along with intervening unicellular islands of cartilage arranged in small chains.

5. Because of this unique structure, fibrocartilage can provide high tensile strength and supporting function and is thus present in areas that are most subject to frequent stress,

6. such as meniscus, intervertebral discs, symphyseal joints, and the joint portion of bone and tendons/ligaments.

7. Elastic cartilage is characterized by its extremely high elasticity because of the presence of abundant amounts of elastic fibers. It is histologically similar to hyaline cartilage but contains many elastic fibers Which form an elastic fiber network along with collagen fibers .

8. This unique feature provides great flexibility so that elastic cartilage can withstand repeated bending. It is mainly found in the outer ear structure, the larynx and epiglottis .

9. Cartilage is a unique tissue with low metabolic rate due to the sparsity of its cell population and its avascular structure. The glycolytic activity and oxygen consumption of cartilage approaches anaerobic condition and the tissue is nourished by tissue fluid diffusion. Metabolism of cartilage

10. This unique non dependence on blood supply ensures that cartilage grafts will survive by imbibing surrounding fluids and are therefore far more reliable in terms of what is called as a ‘ take.

11. cartilage is considered as “ immunologically privileged,” and allogeneic cartilage may serve as a potential graft , autologous cartilage grafting remains the most applicable cartilage graft.

12. According to surgical procedures, cartilage can be transferred either as a free graft. or as a microvascular composite graft.

13. Auricular cartilage graft As an elastic cartilage, auricular cartilage is an ideal graft for transplantation and perhaps is the most versatile of all cartilage grafts because it can be easily fashioned and contoured into different shapes for various uses.

14. Auricular cartilage can be harvested easily under local anesthesia and a significant portion of the concha can be removed without causing donor site deformity .

15. Auricular cartilage graft is often used as a framework for ear reconstruction or auricular deformity correction.

16. In addition, conchal cartilage can be used as a single-layered graft for nasal, tarsal, and nipple reconstruction. .

17. The other important application of auricular cartilage is to transfer as a composite chondrocutaneous graft for nasal reconstruction.

18. Nasal cartilage graft Although limited in its available amount, nasal cartilage has been employed as a composite chondromucosal graft for eyelid reconstruction .

19. Septal cartilage is an important source of nasal cartilage graft . The septal cartilage can be accessed via a hemitransfixion incision with dissection around the caudal margin of the quadrangular cartilage. After both sides of mucoperichondrium are raised, the septal cartilage can be harvested.

20. The other region available for harvesting nasal chondromucosal graft is the upper lateral nasal cartilage, as reported by Tessier in 1979.

21. In addition to eyelid repair, septal cartilage graft has been used for dorsal augmentation, tracheal repair, and extended septal graft for controlling the projection and shape of nose tip.

22. Alar batten grafts are thin, oval shaped cartilage grafts that are placed along the nasal sidewall in the area of the supra-alar crease or area of lateral wall weakness.

23. A spreader graft is a cartilage graft that is insert between the septum and upper lateral cartilage , thereby widening the area of narrowing and opening up the internal nasal valve. The cartilage is usually carved from septal cartilage that is removed during a concurrent septoplasty .

24. Rib cartilage graft Costal cartilage may serve as the best donor site for cartilage graft in terms of available tissue amount and mechanical strength ..

25. The autologous rib cartilage can be virtually contoured into any desired shape and it can retain form and bulk after implantation if basic surgical principles are followed .

26. The costal cartilage graft is often used as a cartilage framework. for total ear reconstruction.

27. Cartilage engineering

28. The tissue-engineering process involves three major components : (1) seed cells: the component for matrix production, deposition, and tissue formation; (2) scaffold: the substance that provides a 3D place for cells to reside, proliferate, and produce matrix ; (3) tissue formation environment :.

29. After being seeded on the scaffold, cells start to grow and produce and deposit ECMs on the scaffold. In a proper environment, with gradual degradation of the scaffold , cell proliferation , matrix production , and proper tissue remodeling, an engineered tissue gradually forms and becomes mature.

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31. Causes of nerve injury Focal contusion(Gun shot wounds) Traction injury Injection injury Compression Crush injuries Avulsion Laceration Electrical burns Others( infections, metobolic ) idiopathic

32. CLASSIFICATION OF NERVE INJURY Classified by Seddon , sunderland and lately by Mackinnon. Into six degress

33. Degrees of nerve injury Ist degree ( Neurapraxia ) Segmental demylination Axons intact Recovery in 12 to16 weeks 2 nd degree injury ( axonotmesis ) Axonal injury/ distal wallerian degeneration Regeneration at the rate of1 inch per month Complete slow recovery

34. Degrees of nerve injury 3 rd degree injury Axonal injury & fibrosis of endoneurium Incomplete recovery 4 th degree injury Axonal injury Damage to endo and perineurium with dense scarring Needs surgical intervention

35. Degrees of nerve injury 5 th degree injury( neurotmesis ) Complete nerve division 6 th degree injury Variable combination of previous five degrees

36. Primary neurorrhaphy is the gold standard by which all other nerve repair techniques are judged . Excessive tension will inhibit nerve regeneration; however a small amount of tension to achieve primary coaptation is acceptable

37. Nerve autograft is the gold standard for reconstructing a nerve gap. In the event of a nerve gap, options for repair include: • mobilization and primary coaptation • nerve repair with nerve graft or conduit • nerve transfers .

38. Indications of nerve grafting Tension at site of repair. Need of postural positioning Alignment of sensory & motor components Maximize number of axons Reversal of graft Exclusion of expendable nerve

39. Factors most affecting nerve recovery include: • age of the patient • location of injury (proximal versus distal peripheral nerve) • type of injury: crush versus avulsion versus transection • timing or repair • technique or repair (tension, alignment, scarring).

40. Advantages Disadvantages Nerve autograft Gold standard for reconstruction Schwann cells in extra cellular matrix Second operative site Results in donor sensory loss Potential for neuroma formation/pain Sensory nerve autografts do not support motor regeneration as well as motor or mixed sensorimotor nerves Limited available length Allograft Can potentially allow functional recovery equivalent to autograft No donor site morbidity Patients Requires patient systemic immunosuppression (~18 months) Patients vulnerable to opportunistic infections

41. NERVE GRAFT TAKE

42. Under ideal circumstances, the nerve graft will behave as the distal nerve stump would. Therefore , the graft must also undergo wallerian degeneration to provide a conduit for axon regeneration.

43. Schwann cell survival in the graft is critical to this process. For the Schwann cells to survive, the graft must be appropriately revascularized . This process occurs both from the proximal and distal nerve stumps and from the surrounding tissue bed. In animal models, graft revascularization reaches supranormal levels in 4 to 5 days .

44. Initial revascularization occurs through the proximal and distal stumps and then the surrounding tissue . Ingrowth from local tissue creates extensive adhesions, which limit graft excursion . The first few days after grafting, cellular viability is dependent solely on diffusion from the tissue bed

45. As graft size increases, central cellular necrosis occurs , because the volume of nerve tissue increases beyond the limits of perfusion or revascularization. This limitation contributes to poor outcome with trunk grafting. Trunk grafts are now used uncommonly, unless harvested as vascularized nerve grafts .

46. Nerve Grafting Techniques In group fascicular grafting, every attempt is made to accurately deliver regenerating axons through the graft material to a matching fascicular group in the distal stump . The distal nerve tissue may be marked and sent for histochemical staining, depending on clinical needs and laboratory capabilities .

47. After graft harvest and careful hemostasis, grafts are sutured to individual fascicular groups with the minimally needed number of sutures . Emphasis again is placed on appropriate fascicular matching without tension

48. Individual fascicular grafting is uncommon. A distal digital nerve defect is a specific, useful indication for individual fascicular grafting . Other indications may arise when clinically critical single fascicles ( eg , the thenar motor branch) can be identified.

49. Graft Material Autogenous nerve graft is the most commonly used material for bridging nerve gaps. Ideally , the donor nerve provides a suitable environment for regeneration and results in acceptable donor morbidity .

50. The sural nerve Through a longitudinal incision or sequential small transverse incisions, up to 40 cm of nerve can be harvested from each leg.

51. In the forearm, cutaneous nerve branches are available as graft material. The medial antebrachial cutaneous nerve (MACN) may be harvested and provides up to 10 cm of graft .

52. . The lateral antebrachial cutaneous nerve provides significantly more graft material than the MACN does -- up to 20 cm . However, the resultant sensory loss along the lateral aspect of the forearm can extend onto the thenar area, making it undesirable for median nerve defects in general and thumb digital nerve injuries in particular.

53. The posterior interosseous nerve may be harvested at the wrist level and yields approximately 3.5 cm of graft material. The graft may be particularly useful in digital nerve defects , and there is no donor morbidity from sensory loss.

54. The use of vascularized nerve grafts provides several potential advantages . The initial period of ischemia (2 to 3 days) after nonvascularized grafting is avoided , the necessity for revascularization via the recipient bed (which may be severely scarred and poorly vascularized) is eliminated, and larger sizes of nerve tissue (in cross section) may be used as graft without the problems of central necrosis.

55. There is experimental evidence that vascularized nerve grafting can produce superior outcomes , though conclusive evidence is still lacking.

56. The most compelling present indication is grafting in a severely scarred tissue bed . Situations where transfer of large nerve trunks is desirable and feasible ( eg , brachial plexus reconstruction using the ulnar nerve) may benefit from this technique, as well.

57. Nerve Vascular Supply Superficial radial Radial artery Ulnar Superior ulnar collateral artery Sural Superficial sural artery Anterior tibial Anterior tibial artery Superficial peroneal Superficial peroneal artery Saphenous Saphenous artery Vascularized Nerve Grafts: Donor Nerves and Associated Vessels

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