Annals of Burns and Fire Disasters - vol. X - n. 1 - March 1997

DEEP BURNS OF THE KNEE: JOINT CAPSULE RECONSTRUCTION WITH DERMIS GRAFT

M. Masellis

Divisione di Chirurgia Plastica e Terapia delle Ustioni, Ospedale Civico, Palermo, ltaly

SUMMARY. Cases are presented of serious 111 degree deep burns in the knee area, with carbonization of skin tissues, the rotular apparatus, and muscle and articular tissues, with ample exposure of the femoral and tibial condyles. In the light of experience acquired both clinically and experimentally, the authors reconstructed the joint capsule with autologous dermis graft. This method, by permitting fairly good and rapid articular stability, allows early mobilization and therefore a favourable modulation of the periarticular scar tissue, with good recovery of joint movement.

One of the advantages of the plastic surgeon is the ability to identify imaginative alternative solutions to problems of reconstructive surgery that cannot be solved by normal surgical techniques. The use of dermis may be included among these solutions, even if its use has had alternating fortunes in the history of reconstructive plastic surgery.
When in 1987 G. Dogo proposed the use of Padgett's dermotome to remove the whole dermis, it was possible to overcome the numerous technical and biological problems which previously had conditioned the use of dermis. With the Padgett dermotome it is possible in a few minutes to remove a flap of 200 sq cm of dermis, thus permitting immediate repair of the donor area.

Histology of the dermis
The dennis is a dense fibrillary connective tissue, also called fibrous connective tissue, closely related to the epidermis which protects and feeds it. It provides a site for skin appendages such as hair follicles, sebaceous glands, and sweat glands. The dermis is conventionally divided into two parts: a) the papillary and periadnexal dermis, "adventitial dermis", and b) the "reticular dermis". Adventitial dermis is characterized by thin, haphazardly arranged collagen fibres, delicate branching elastic fibres, numerous elongated, plump and stellateshaped fibroblasts, abundant ground substance, and plentiful capillaries, linked to superficial arterial and venous plexuses. The papillary dermis and the epidermis together form a morphological and functional unit devoted to the very active metabolic life of the skin. The reticular dermis, the larger part of the dermis, extends from the base of the papillary dermis to the subcutaneous fat. It is composed of collagenous fibres arranged in bundles of various thickness and immersed in a scarce amorphous matrix. The bundles are mostly arranged parallel to the skin surface in an orthogonal wickerwork. A network of coarse wiry elastic fibres enmenshes the collagen bundles. In this part of the dermis there are few fibroblasts and blood vessels.
Occasionally, cells of subcutaneous fat can be found.
The fibroblasts are the builder cells of the dermis. They produce all the fibrillary components, as well as the amorphous matrix.
The collagen of the dermis consists of two different types. Type I forms thick fibres arranged in a dense orthogonal network in the reticular dermis and seemingly mostly parallel to the skin surface. Type II collagen is found principally in the adventitial dermis and consists of thin fibres, loosely arranged.
These fibres are prominent within and beneath the epidermal basement membrane, where they intermingle with type I collagen fibres.
Immature elastic fibres are aggregates of protein microfibrils grouped cylindrically along the surface of the fibroblasts. The fibroblast synthesizes a protein, elastin, and secretes it into the preformed tube of microfibrils.
Collagenous and elastic fibres are closely associated with each other. Collagen presumably provides the skin with tensile strength, whereas elastin returns the skin to its original dimension after stretching.
The interstitial substance produced by fibroblasts is composed of amorphous, semifluid mucoid material. The main components are t , he mucopolysaccharides (hyoluronic acid, chondroitin sulphate, dermatan sulphate) and cellular elements consisting of fibroblasts, histiocytes and mast cells, mainly in the perivascular area.

Histology of the articular capsule of the knee
The articular capsule of the knee consists of a dense fibrous connective tissue in which thick bundles of collagen fibres in undulating fashion weave in all directions. The bundles are enveloped by a scarse amorphous matrix in which there are some elastic fibres. This arrangement offers a high strength to traction and pressure.
Generally the orientation of the bundles is determined by the dynamic strain to which the articulation is subjected.
The articular side of a capsule is covered by synovial membrane. This membrane consists of collagen and elastic fibres and it is rich in fibrocytes, adipose cells, and histiocytes.
The surface of the synovial membrane can be enlarged by the presence of synovial villi, which are rich in vessels. The synovial membrane produces synovia.

The autologous dermis graft
Dermis graft is a free graft containing all the cutaneous strata remaining after removal of the epidermis, i.e. the deepest strata of the papillary dermis, the reticular dermis with a minimum quantity of subcutaneous fat, together with the epithelial components consisting of the epidermic appendages (hair follicles, sebaceous glands and sweat glands).
The advantages of autologous grafting of the dermis are: the facility and rapidity of removal thanks to the use of the Padgett dermotome, its resistance, and its limited post-operative reabsorption, which normally does not exceed 20% of the grafted implant.
The use of dermis autografts, instead of grafts of fascia lata or tendon which previously were used in reparative operations, especially those requiring considerable resistance to tensile forces, was introduced by Loewe in 1913 and Rhein in 1914.
Since then dermal autograft has been used in the correction of facial deformity, for knee, hip and elbow arthroplastics, and to strengthen extra-articular ligaments, e.g. of the temporomandibular joint.
The use of the dermis has proved to be very effective in the treatment of post-laparotomy hernias, when it is desired to reinforce the abdominal wall after reconstruction of the fascial plane.
Studies performed by Peer and Paddock' on fragments of dermis graft have shown that epidermal residue surviving on the surface of the graft gives rise to the formation of microscopically sized epidermoid cysts which do not affect the clinical outcome.
Thompsoril, has shown that the sebaceous glands and hair follicles disappear within a period of between two weeks and two months.
It is probably the hair follicles that cause the formation of the epidermoid cysts. These cysts, with the progressive increase of the internal tension determined by the epithelial elements, begin to atrophy and exhibit foreign body reaction accompanied by fibrosis.
The sweat glands survive and function much longer. Their secretions are entirely absorbed by the adjacent capillaries. No evidence has been found relating their survival to malignant degeneration.
The pilomotor muscles (arrectores pilorum) survive and the elastic fibres are preserved. They remain in great numbers arranged as in normal skin.

Technique for removal of the dermis
The dermis removal technique is easily accomplished by using a Padget drum dennotome.
If the blade of the dermotome is regulated to maximum thickness, it is possible to remove together epidermis and dermis as far as the adipose layer (Fig. 1).
Without detaching the flap adhering to the drum from its connection with the donor area, the blade is returned to the position of the anterior edge of the drum and regulated again to a thickness of 0.5 - 0.6 min (Fig. 2).

Fig. 1 - Dermotome blade regulated to maximum to remove epidermis and dermis. Fig. 2 - Dermotome blade regulated to a thickness of 0.5-0.6 mm to separate epidermis from dermis.

Further cutting separates the dermo-epidermic flap into two sheets: the epidermic sheet remains attached to the drum, while the other sheet is free and constitutes the real dermal graft, 0. 14 - 0.6 nim thick, uniform, and with a surface area of about 200 cm', i.e. equal to that of the dermotome drum (Fig. 3).
The sheet of epidermis detached from the drum provides an autograft to cover the donor area (Fig. 4).

Fig. 3 - The two sheets separated Fig. 4 - The sheet of dermis of 200 cm.

Evolution of the dermis placed ectopically
The use of dermis to reconstruct the capsular envelope of the knee, metacarpophalangeal and phalangeal articulations '1042 and Achilles tendons was suggested by confirmation, after experimentation based on hypothesis, that dermis transferred in ectopic position reorganizes its structured components with particular advantages for its mechanical function.A more accurate histological morphological and functional study enabled us to extend our knowledge of the problem and give it a better biological interpretation and offered a possible interpretation of the cyto-morpho-architectonic evolution of dermis in ectopic position. Ten Cate and Freeman identified the role of the fibroblasts in the repair of slow remodelling cutaneous wounds such as those involving dermis.They described three separate areas in which fibroblasts behave in a clearly destructive and different manner in relation to the structured characteristics of the fibroblasts: the area of preexisting connective tissue, the area of newly formed connective tissue, and the transition area.The morphofunctional peculiarities of the fibroblasts are the motivation of the use of dermis in the repair of extensive wounds, although in fact in the remodelling of the dermis a part is played by all three components of the connective tissue cells fibres and ground substance. They work together in the remodelling of collagen during the repair stage, each having a precise role in the final orientation in the space of the connective fibres that are subjected to precise strains.Ther6 are good reasons for thinking that both the fibroblasts of the implanted dermis and those of ectopic areas first cause hydrolysis of the proteoglycans, by means of lysosomial enzymes acting on the polysaccharide bonds; this is followed by degradation of the collagen fibres. The purpose of the digestion,of the fibres and the ground substance is the elaboration of molecules that must adopt a precise spatial organization such that the definitive collagen fibres may, by interreacting electrostatically with the proteoglycans, orient themselves according to force lines depending on the outline shape. The production of fibrils and amorphous matrix is based on a correct balance between absorption on the one hand and synthesis on the other. This function is performed by the fibroblasts both of the implanted dermis and of the ectopic area, which take on the ultrastructural characteristics of active cells. The fibroblasts' phagocytic and synthetic activity deterinines the area of transition between the preexisting and the nascent connective tissue. The final arrangement of the aggregated fibres and on the macromolecules of the ground substance in gel state determines the alignment of the fibres. Thus, the final remodelling depends on the cell components involved in reabsorption of the fibres, production of fibres, and ground substance; the arrangement and orientation of the fibres which, certainly depend on the shape of the outline together with external strain, are detennined by forces acting both on the fibres and on the macromolecules of the ground substance.

The dermis was utilized to reconstruct the articular capsule of the knee, in the event of serious traumas with damage of the skin, muscles and joint capsule or if there was exposure of the femoral and tibial condyles.In the case of large trauma of the articular capsule, regardless of the surgical repair work undertaken, functional recovery is nearly always impaired because of the formation of a "pannus" above and around the condyles stimulated by prolonged immobilization, leading to the formation of bone adherences and capsular contraction which progressively reduce mobility, even causing ankylosis.Rapid reconstruction of the joint capsule permits an early and moderately good degree of stabilization of the joint, more rapid mobilization, and more favourable modulation of the particular scar tissue with a notable degree of articular movement. The trophic function of the dermis is probably guaranteed by the fact that on the articular face of the re-formed capsule the reconstruction of the synovial membrane is probably a result of slipping of the synovial membrane from the residual capsule.

Case I
Woman aged 53 years, who fell onto a brazier in the open containing burning coals, after loss of consciousnes, remaining for a long time in contact with a source of heat.
The woman suffered III degree deep burns and carbonization around 3/4 of the knee area and 1/3 of the anterior proximal surface of the leg. Skin, muscles, rotular apparatus and joint capsule were severely damaged (Fig. 5a).
After initial treatment with chemical escharectomy by means of antiseptic antibiotate salicylate vaseline"I and subsequent removal, even surgical, of the residual necrotic tissue of the rotular apparatus and of the articular capsule, the femural and tibial condyles were amply exposed, appearing to be eroded and damaged by heat action (Fig. 5b).

Fig. 5a - Knee and surrounding area on admission Fig. 5b - Exposure fissural and tibial condyles.

The reconstruction of the capsular apparatus was achieved by means of dermis.
The sheet of dermis was sutured, with the epideurnic surface towards the joint, to the residual capsular tissue or to the periosteum by means of Dexon or Vicryl 2/0 stitches. In this case we used a sandwich of dermis (about 400 em') (Figs. 5c, 5d).

Skin coverage was ensured by rotation of an ample fasciocutaneous flap from the posterior face of the leg.
Mobilization and physiokinestherapy began after 7 days. Control at 6 months (Figs. 5e, 5J) and after 4 years (Figs. 5g, 5h).

Figs.   5e, 5f - Recovery of articular function after 6 months. Figs.   5g, 5h - After 4 years.

Case 2
Man aged 79 years, with deep burn of medial surface of the left knee, mediodistal femoral surface, and medioproximal tibial surface.
After chemical and surgical escharectomy the articular capsule was found to be destroyed with exposure of the knee articulation (Fig. 6a).

Fig. 6a - Aspect of knee area after escharectomy. The open articulation.

The surrounding areas were covered by skin grafts, while the capsular apparatus was reconstructed by means of dermis.
A large fasciocutaneous flaps ensured skin covering (Figs. 6b, 6c).

Fig. 6b - Reconstruction of capsular apparatus by means of dermis. Fig. 6c - Skin covering by fasciocutareous flap.

After 7 days the patient began physiokinesitherapy and after 10-12 days the articular excursion appeared to have fully recovered (Fig. 6d).

Fig. 6d - Articular excursion satisfactory after 10- 12 days.

Case 3
Woman aged 75 years with large deep burn of medial surface of proximal third of tibial region, medial surface of knee, and medial surface of the femoral region.
The patient was admitted to our department from another hospital 45 days after the burn and after a period time of immobilization (Fig. 7a).
After escharectomy the medial articular capsule appeared totally destroyed with extensive exposure of the femoral and tibial condyles (Fig. 7b).

Fig. 7a - Burned area before complete escharectomy. Fig. 7b - Large exposure of femoral and tibial condyles.

A large sheet of dermis was utilized to reconstruct the capsular apparatus which was reinforced by two strips of dermis (Figs. 7c, 7d).

Fig. 7c - The large sheet of dermis used to recostruct capsular apparatus Fig. 7d - Two strips of dermis were placed to reinforce the reconstructed capsule.

A large fasciocutaneous flaps assured skin covering The remaining burned areas were covered by skin grafts.
Kinesitherapy began later (after 2 weeks) (Fig. 7e) owing to the protracted previous immobilization; the recovery was slower and difficult also because of the patient's advanced age (Figs. 7f , 7g).

Fig. 7e - Articular excursion after 2

Case 4
Child aged 12 with associated injury of contact burn and of the crawling wound in medial surface of the knee.
After escharectomy there was a large loss of articular capsule with exposure of the femoral and tibial condyles (Fig. 8a).

Fig. 8a - Large loss of articular capsule with exposure of condyles.

The reconstruction of the articular apparatus was achieved with a sheet of dermis reinforced by two strips of the same tissue (Figs. 8b, 8c)

Fig. 8b - Recostruction of articular apparatus with a sheet of dermis Fig. 8c - Scrips of dermis used as reinforcement

Skin coverage was obtained by means of local skin flaps and a skin graft (Fig. 8d).

Fig. 8d - Before placing skin graft.

There was total recovery of the articulation (Figs. 8e, 8f, 8g, 8h).

Fig. 8e - After I year. Fig. 8f - Total recovery of articulation Fig. 8g - Total recovery of articulation. Fig. 8h - Total recovery of articulation.

Conclusion

We believe that in the case of deep burns of large joints in which there is destruction of the caDsular envelope the use of autograft dermis to reconstruct the articular capsule may provide a good solution. The results obtained in experimental investigations and clinical practice for post-traumatic lesions enable us to present a method that may serve at least as an alternative surgical technique to those already in use, which always lead to impairment of functional recovery.

RESUME. L'auteur présente des cas de brûlure grave de III degré dans le zone du genou, avec carbonisation des tissus de la peau, de l'appareil rotulien, et des tissus musculaires et articulaires, avec une ample exposition des condyles fémoraux et tibiaux. Sur la base de l'expérience acquise cliniquement et expérimentalement, l'auteur a reconstruit la capsule articulaire utilisant une greffe autologue de derme. Cette méthode, en permettant une stabilité articulaire acceptable et rapide, facilite une mobilisation précoce et en conséquence une modulation favorable du tissu cicatriciel périarticulaire.

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