1. Cartilage is a valuable source of tissue for grafting. It is readily available, bulky, easily shaped and survives well.
2. The metabolism of a cartilage is unique in that it is virtually anaerobic. The fact that it uses sulphur for its metabolism from the surrounding fluid is in a way a throwback to distant times on our earth where organisms first appeared in the sea without oxygen in a primordial soup which contained methane and some sulphurous compounds.
3. 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’.
4. A chondrocyte constitutes the basic cell in the cartilage and this cell generates both the ground substance (chondroitin sulfate) and the fibrous network within this substance. This fibrous network can be tough, (fibro cartilage in the intervertebral disc) elastic as in the ear, at the junctions of the ribs and the sternum, in the larynx or in the ala of the nose or in the bronchii. The hyaline cartilage with a specialized fibrous network also covers all articulatory surfaces of the bones which form joints. Equally important are their function in the epiphysis where successive layers of bones are deposited as the bones grow with great symmetry.
5. In some specific areas for example in the rib cage or the nasal septum a somewhat specialized chondrocyte lays a ground substance which locks the cartilage into a shape. Any injury to this locking function unfurls the cartilage leading to warping. Accidental traumatic injury to a septum may therefore cause a deviation both visible to the eye or within the nasal cavity to cause obstruction. When a cartilage is used as a graft, so that it does not warp, care must be taken not to injure the epichondral layer. In an ingenious method a crooked septum can be harvested as a whole placed inside a special hammer then broken and this broken straight material can be fixed in a biological glue and is replaced between the central septal mucosal layer. Here warping is not possible because this new substance is an amalgamate.
6. A popular operation in recent times has been to surgically score cartilage on one side to offset an already present deformity caused by injury or deviation to the opposite side. The procedure called septoplasty though based on sound science has not been proved to be successful in any long term series for the simple reason that the nature and effect of the original injury and deviation cannot be mimicked on the opposite side by what is best a random scoring. The visible anterior part of the septum is not amenable to any scoring and may be best camouflaged by a thin bone or cartilage graft.
7. The tendency of a cartilage to warp can be used as an advantage by the surgeon when reconstructing an ear. Selective scoring under vision in vitro may effectively produce a curvature which is suitable for reconstruction. This reorientation will take about 30 minutes to manifest and that much time must be spent before the cartilage is placed at the desired site. However the sculpting of a cartilage from the costo chondral junction can be done at leisure by extubating the patient and sending him to the recovery room only for the patient to be brought back for implanting the sculpted framework.
8. Autogenous cartilage grafts are hardy in the sense that their metabolic requirement is low and chondrocytes will survive by virtue of the tissue fluid in their immediate environment and do not need any blood supply. Cartilage also does not undergo in metaplastic or structural changes per se. Even when a cartilage warps due to the unequal tension of a damaged perichondrial cover it’s substance remains unchanged.
9. The commonest sites for harvesting a cartilage are the costochondral area, the nasal septum and the auricular cartilage. Of the latter a fair amount can be harvested without producing any great visual deformity.
10. The auricular cartilage can be used in nasal reconstruction (to augment a saddle nose) as an overgraft over a deficient lower nasal alar cartilage (as in a cleft lip nose), as a tarsal plate in the eyelid and even in the areola to mimic Montgomery’s tubercles and to extract and keep erect an inverted nipple.
11. The nasal septal cartilage is even more abundant and be used with one of its mucosal covers for reconstructing the eyelid, the cartilage serving as a tarsal plate and the mucosa merging with the conjunctiva. It is also a local source for the augmentation of the saddle nose, for camouflaging deviation in the visible part of the nasal septum and as mentioned earlier by crushing it in a hammer and then after using the glue, to replace it back to improve the results of a septoplasty. While harvesting a septal cartilage the ‘L’ strut (anterior and columnar) must be preserved to avoid a collapse of the nasal right angle.
12. The costo chondral junction in by far the largest source of cartilage graft. Though while harvesting such a graft it must be borne in mind that the cartilage gets ossified with age and less and less will be available as age advances. The reconstruction of ear for microtia when done at an appropriate age (7-9 years) is by far the best time to harvest this graft. The ossification in this area can be converted to an advantage by harvesting an osseo-cartilaginous graft in reconstructing and replacing small missing portions of the mandible, though with the advent of microvascular surgery mandibles are now invariably reconstructed with a free live graft. In the nose particularly in the adults this mixed graft serves a good purpose and are in fact a rib cartilage graft.
13. Notwithstanding the fact that a cartilage graft because of its almost non-existent blood supply is not an immunologically aggressive tissue the experience with homograft as well as irradiated homografts has not been encouraging.
14. The formation of post traumatic cauliflower ears resulted in the realization that an avulsed perichondrium produced cartileginous tissue over the denuded area and has led to the use of perichondrium in denuded cartilaginous joint surfaces, for example in the temporo mandibular joint to resurface both the socket as well as the head of the mandible or in the inter phalyngeal and meta carpophalyngeal joints. While the former, that is reconstructing the temporomandibular joint with perichondium has been reported frequently no long term results appear to have been published. The same appears true of reconstruction in the small joints of the hand.
15. While the idea for a chondrocutaneous graft appears attractive for complex defects for example in the loss of an ala of the nose, these grafts are not very popular because of for their complete or partial failure and certainly in India very few successful results have been demonstrated. The ostensible reason for which has been given as unsuitable humid climate.