Soft tissue defect of the knee is something which is frequently observed in orthopaedic surgery and traumatology. The present article proposes a number of simple but reliable techniques for covering a loss of soft tissue in this region of the anatomy. In addition, these techniques are adapted to surgical management in hazardous conditions i.e. when the working environment is difficult or even precarious such as at some medical centres in developing countries or in some small French hospitals during on-call duty at the weekend and after 6 pm…
Please refer to the article on reconstructive surgery under difficult conditions (Maîtrise d’Orthopédie, N° 118 and 122) for the general principles of reconstruction using simple techniques applied in difficult working circumstances.
In this article we propose reconstructive surgery of the knee, in practical terms.

 

 

WHAT TO DO WHEN THERE IS A LOSS OF SOFT TISSUE

We offer various solutions for treatment, from the simplest to the most complicated.

From the simplest to the most complicated

 

Faced with a loss of soft tissue, there are a number of possibilities:

1) foregoing treatment (it is sometimes a good idea to say “no” when local and general conditions suggest that treatment will not be successful),
2) controlled wound healing,
3) a skin graft,
4) a flap.

We offer this classification while realizing that it remains subjective. For example, controlled wound healing which in appearance seems simple, is difficult to apply when it is not possible to follow up on dressings. In this case a reliable flap which does not require any real postoperative follow-up would be better indicated. It is therefore sometimes simpler to carry out at the outset what appears to be a more complicated procedure (in this example, a flap compared to controlled wound healing).

 

When to carry out controlled wound healing

 

Repair by controlled wound healing is a proper technique and should not be left as a solution of last resort. It has its own indications. It consists of letting the area with loss of soft tissue close up by itself. The term "controlled" supposes that types of dressing will be used that will guide healing.

It is indicated when:

- Dressings can be put on and changed regularly with proper follow-up.
- Other coverage techniques seem to be more risky or difficult to carry out given the environment. For example, the absence of an operating room would suggest that it is unwise to carry out a delicate surgical technique and that controlled wound healing is called for.
- The loss of soft tissue is not too great and when it is thought that this kind of repair will enable wound healing within a reasonable period of time.
- The subsurface is not conducive to a skin graft (granulations still soft or already infected, etc.).
- Loss of soft tissue does not expose an important structure.
- Loss of soft tissue is not located around an orifice or a joint. Controlled wound healing will cause considerable retraction of tissue. Retraction of tissue around an orifice will modify the normal anatomy of the structure. For example, controlled wound healing on a lower eye-lid can cause an ectropion.

 

When to carry out a skin graft

 

The skin graft technique is also a proper surgical technique which combines a series of small details essential to the success of the procedure. It has the advantage of covering immediately, or within a few days, an area with considerable loss of soft tissue. It has the disadvantage of requiring a dressing and relative immobility for the first few days since the initial dressing of the graft is capital.
In any event, a skin graft can be carried out immediately or secondarily. It should be remembered that a skin graft can be applied immediately on a muscle, periostium or subcutaneous fat after the removal of a tumour or after a debridement. You can also wait a few days and let the granulation grow and carry out the graft on a thicker substratum. This will limit somewhat the residual depression that can be observed after a skin graft on some areas which have had an immediate graft.

A skin graft can be thin or total

- A thin skin graft takes more easily on a substratum of average quality but will retract more. It is therefore better indicated for an area with significant loss of soft tissue, at a distance from a joint and when granulation is acceptable.
- On the other hand, a total skin graft requires good quality granulation but does not retract. It should be preferred for small soft tissue losses in periarticular zones.

A skin graft can be full or in mesh form

- A full skin graft consumes a lot of skin since to cover 10 sq. cm of loss of soft tissue you will need 10 sq. cm of skin. But it provides a more attractive result. It is therefore indicated when the loss of soft tissue is not too great and when the final appearance of the reconstruction is important.
- A mesh skin graft allows for coverage of larger areas but is not very attractive in appearance. It should therefore be reserved for very large amounts of soft tissue loss in areas which can be hidden by clothes, for example.

 

When to make a flap

 

The flap technique requires a minimum amount of training.

To close up an area with a loss of soft tissue, you can carry out:

1) a local flap (surgical procedure with local skin such as a rotation flap),
2) a regional flap (pedicled flap in the same region such as a flap from the internal gemellus muscle),
3) a distance flap which can be pedicled, such as a fasciocutaneous flap from the contralateral leg, or which can be free, such as a musculocutaneous flap from the latissimus muscle of the back, transferred with microsurgery.

 

 

SPECIFICITIES OF COVERAGE OF THE KNEE

The knee is a mobile region

 

- Scars are subject to strain from movement. They are therefore often of poor quality. In addition, suturing for a loss of soft tissue is generally carried out on the operating table with the knee in extension. When the patient bends the knee, the suture will be put under pressure and may, in some cases, be an obstacle to mobility of the joint. So, avoid sutures with tension which is too great in a joint region, and prefer a solution which will provide some ease of movement for the tissue.

- If a skin graft is chosen, it must be total so that retraction is moderate. It should be remembered that a thin skin graft “takes” more easily but it tends to retract a lot. On the other hand, a total skin graft requires a better quality receiving site, but there is little retraction. A total skin graft is better adapted to a joint or periarticular region because it will retain its flexibility.

- The mobility of the knee will require coverage with resistant but flexible tissue. Cutaneous strips are recommended. Muscle strips are thicker but they enable gaps to be filled or can play a role as spacer if necessary.

 

The knee is an articulated region

 

- the underlying presence of elements such as tendons or joints requires reliable coverage. As a corollary, controlled wound healing should be reserved for precise areas with a stable substratum and good granulation.

- The presence of joint cartilage dictates coverage even in the presence of signs of infection. Generally, when a region is infected, the plastic surgeon does not like to close the zone with a flap; we don’t like to “set the cat among the pigeons” as it were. It is preferable to leave it open, to wash it out and first of all settle the problem of infection before envisaging coverage. In the case of the knee, it is difficult to leave cartilage exposed to the air; so it needs to be covered, but not too tightly to ensure drainage. Others may close and drain using Redon stylets. It’s a question of habit and of "school," however we believe that removal of infected material is the first thing to be envisaged.

 

The knee is a weight-bearing region

 

- In difficult cases (open fracture, infected prosthesis, long-standing sepsis, etc.), reconstruction should endeavour to meet a number of imperatives. In the case of the knee, maintaining the length of the limb is often mentioned first and foremost, and fitting a secondary orthopaedic device is often envisaged. Coverage will be needed, whatever the technique. Good coverage is an essential prerequisite to fitting a secondary prosthesis, for example.

- On the other hand, difficult cases sometimes lead to a shortening arthrodesis. the bone shortening produced can be beneficial. Drawing the bone extremities closer will at the same time enable joining of the skin edges. Closure can be obtained without the need for additional tissue.

 

 

COVERAGE OF THE KNEE IN PRACTICAL TERMS

 

We will present four standard situations which summarize standard practice:

1) loss of tissue exposing the suprapatella ligament,
2) exposure of the patella,
3) sepsis of a prosthesis with loss of external soft tissue,
4) open fracture of the tibial plateau will loss of soft tissue.

 

 

1) Significant loss of suprapatella tissue exposing the patella ligament

Discussion of techniques

 

- Controlled wound healing ? Controlled wound healing is not indicated here because an important structure is exposed. In addition, controlled wound healing will mean retraction of tissue which would be harmful for knee flexion.

- Skin graft ? A skin graft can be envisaged, but it should be total to retain full flexibility of this mobile zone. However, for a total skin graft requiring a reliable and stable substratum, the patella is not the best place. It should be remembered that a tendon which has retained its sheath can either be grafted immediately, or secondarily after the appearance of good quality granulation. Whereas, when the sheath has disappeared, coverage with a flap is preferable.

- Flap ? Exposure of the patella tendon does not require thick coverage with a muscle flap. A skin flap would be better adapted, combining reliability and flexibility. It can be harvested locally if the tissue environment allows. However, creating additional scars which may generate adherences around the joint should be avoided.

  

Our choice: Local skin flap

We suggest a local flap transfer, of the Limberg flap type: (Fig. 1 a, b, c, d, e)

 

Fig. 1a. Example of loss of soft tissue opposite the quadriceps tendon which it is decided to cover with a local flap.

Fig. 1b. Flap design: you transform the area of loss of tissue into a diamond shape. You draw on the side a skin flap which will come up and cover the loss of tissue.

Fig. 1c. Diagram of a Limberg flap: 1) You create a diamond shape - A, B, C D. You make two counter incisions: D – E which is equivalent and in the continuation of B – D, and E – F which is equivalent and parallel to D – C. Your skin flap will be C-D-E-F. 2) and 3) You remove the skin flap C-D-E-F like any other flap i.e. without trying to individualize any sort of pedicle. You harvest the skin with its subcutaneous fat. Then, in order to transfer it to the receiving zone, you need to lift up the surrounding skin as required. 4) You transpose the freed-up flap towards the area of tissue loss by joining F to D. 5) You obtain coverage of the tissue loss with the flap. The donor zone of the flap is closed up by simply bringing together the edges of skin that you have already removed.

Fig. 1d. The flap is transferred to the zone to be covered.

Fig. 1e. The skin edges are sutured.

 

2) Exposure of the patella

Exposure of the patella can have a number of causes. We will take as an example a skin necrosis secondary to osteosynthesis with exposure of device.

Discussion of techniques

 

- Controlled wound healing ? Controlled wound healing is not indicated in this case because an important structure is exposed (bone) as well as the osteosynthesis device. Reliable coverage is essential here.

- Skin graft ? A skin graft would not “take” on an osteosynthesis device. However, we could remove this device and wait to have good granulation before carrying out a skin graft. The result would not be perfect but, in certain difficult circumstances, it might suffice. The advantage would be coverage of the bone; the disadvantage would be to have clingy and fragile skin over the patella.

- Flap ? A flap seems to be indicated in this case because it will permit reliable and flexible coverage It must be thin, elastic and easy to do The disadvantage is the learning required in the flap technique and the presence around the patella of fairly muscular strips such as those from the gemellus muscles.

 

Our choice: A locoregional fasciocutaneous island flap (Fig. 2 a, b, c, d, e, f, g, h)

Faced with exposure of the patella, we would suggest a pedicled neurovascular flap using the great saphenous vein. It is a good flap, reliable, elegant and provides a thin, flexible skin paddle for this mobile region. Harvesting is easy if the technique is followed properly. The disadvantage is the need to carry out a second operation to separate the pedicle.

 

Fig. 2a. The paddle is drawn on the path of the internal saphenous nerve and the great saphenous vein, half way up the leg The patient is in a dorsal decubitus position with a cushion under the contralateral buttock. The incision, enabling exposure of the pedicle, projects 1 cm back from the posterior edge of the tibia and starts 3 cm under the articular joint space in medial aspect.

Fig. 2b. There is a vascular network around the internal saphenous nerve which can vascularize the skin paddle. Concomitant harvesting of the great saphenous vein will facilitate retrieval and promote drainage of the flap. After having made an incision in the skin facing the pedicle, you lift up two strips of skin on either side. You will visualize the superficial fascia without being able to really distinguish the nerve or the vein. Do not try to isolate them.

Fig. 2c. Mark off a band of cellular tissue which will represent your pedicle (2 to 3 cm wide). It is a proximal pedicle flap where the pedicle will consist of all the subcutaneous tissue on either side of the nerve and vein. The deep border is delimited by the muscle fascia.

Fig. 2d. Distally you locate the saphenous vein which needs to be fastened. The skin paddle is lifted taking everything right up to the fascia of the underlying muscles. Dissection continues from distal to proximal, passing just above the muscle fascia. Stop dissecting proximally when the length of the pedicle is sufficient to reach the patella.

Fig. 2e. When the pedicle has been fully dissected, check the proper vascularisation of the skin paddle. You can then place the flap on the area of soft tissue loss and keep it in place with a suture. This will enable you to determine the tolerance of the flap in its future position and to check that vascularisation of the skin paddle is satisfactory. At the same time you can also suture the two strips of skin which have enabled exposure of the pedicle.

Fig. 2f . Harvesting a skin island will leave a circular loss of tissue which will need to grafted with a thin skin graft. You can either do the graft immediately making a bolster (see Maîtrise d’Orthopédie, N°s 118 and 122), or leave the granulation to grow and do a skin graft later on.

Fig. 2g. The skin paddle is sutured on the area of loss of soft tissue. The pedicle is left on the outside and a paraffin gauze dressing is applied to it. It takes three weeks, on average, to become autonomous. Some authors propose passing the pedicle under the skin creating a subcutaneous tunnel. We prefer to avoid this option given the risk of too much compression of the pedicle. After three weeks, we proceed with the separation of the pedicle by sectioning it level with the paddle and at its base.

Fig. 2h. One or two sutures are applied to the skin paddle to adapt the final result. The exit orifice of the pedicle is left to controlled wound healing.

 

3) Sepsis on knee prosthesis with external exposure

Infection on a knee prosthesis is a real problem and a decision as to treatment will depend on the experience of the surgeon involved. When the device is exposed, there is the additional problem of its coverage. Whatever “school” we belong to, we all agree that faced with an exposed prosthesis, there is a requirement for quality coverage.

 

Discussion of techniques
 

- Controlled wound healing ? Controlled wound healing is not indicated in this case because the osteosynthesis device is exposed. It needs to be covered.

- Skin graft ? Without a reliable substratum, a skin graft is not possible. In addition, there is the problem of the infection.

- Flap ? Exposure of an osteosynthesis device requires reliable coverage. The joint region suggests a flexible flap. But the infectious context requires a flap which will fight the infection. A pure muscle flap enables good coverage and will fight infection. In addition, if the surgeon needs to remove the prosthesis, the volume of the muscle flap will serve as a spacer.
 

Our choice: Pure muscle flap from the lateral gemellus muscle

With external exposure of a knee prosthesis, we suggest a muscle flap from the lateral gemellus muscle. This is a reliable flap which will cover the loss of soft tissue and pump out the infection. The vascular wealth of the muscle facilitates the fight against infection. The flexibility of the muscle means the surface can be adapted to the loss or even to fill a dead space. Skin is not harvested.

a) Anatomical background

 

The gemellus muscle is vascularized by the genicular artery which is a branch of the popliteal artery. Each gemellus (internal and external) has its artery. The muscle can be entirely pedicled on its nutrient artery, but in practice, it is not necessary to “push” the dissection of the pedicle to its origin on the popliteal artery. You “lift” the muscle as required and dissect the pedicle as required (Fig. 3 a, b, c, d).

 

fig 3 a,b,c,d

b) Position on table

This should enable exposure of the external aspect of the leg. A cushion is placed under the ipsilateral buttock to place the thigh in slight internal rotation. The tourniquet at the top of the thigh will spontaneously position the knee in slight flexion which makes the operation position easier.

c) Incision

This is made facing the external gemellus muscle that is localized under the skin on the external surface of the leg. This localization can be done in the patient’s room before the operation. After having incised the skin and subcutaneous cellular tissue, you localize the muscle which is just under the skin. Sometimes the soleus muscle can be mistaken for the gemellus muscle. You need only to lift up the intermuscular septum with the finger to rapidly identify the soleus in depth and the gemellus more superficial. Dissection with the fingers facilitates this phase of the operation. (Fig. 4)

fig 4

d) Dissection of muscle

Dissection of the muscle is quite easy. Its anterior surface is freed up with the finger. Its posterior surface is lifted from the subcutaneous level with the finger or scissors. Some cutaneous perforans need to be coagulated. Only the area of union between the two gemellus muscles, along the median line, will require the assistance of the cautery knife or dissection with scissors and good arrest of bleeding. The distal extremity of the gemellus is also very adherent and will require sectioning with scissors or with the cautery knife. The aim at this stage is to entirely free up the muscle on all of its surfaces in order to pediculate it on its upper insertion. The vascular pedicle can be seen at this stage but its dissection is not essential (Fig. 5).

fig 5

e) Rotation of muscle

Once the muscle is free, you lift it up to see if the dissection is adequate. The drawing shows the vascular pedicle of the muscle well individualized but, in reality, it is not very visible. You will need to pivot the muscle on to the zone to be covered and upwards freeing of the muscle will occur progressively and as required. (Fig. 6)

fig 6

In practice, two remarks:

- You can, in theory, after having localized the pedicle, continue dissection of the muscle up to its insertion. But it’s not really useful to reach the knee. Don’t waste time unnecessarily.

- The muscle passes perfectly well over the biceps femoris tendon. We avoid passing the muscle under the tendon because, when the knee is in extension, there is a risk that the tendon will compress the underlying muscle.

f) Example of pedicled internal gemellus muscle flap for coverage of internal aspect of knee. The protocol for the procedure is almost identical (Fig. 7).

fig 7

 

4) Open fracture of tibial plateau with loss of soft tissue

It is perhaps appropriate to remember here that the prelude to any repair, in this context, is a good quality skin debridement. In most cases we are in a context of direct trauma and, consequently, tissue will be heavily crushed. You should not hesitate to do a proper debridement of contused and dubious tissue to avoid secondary necrosis which might infect your underlying osteosynthesis.

Discussion of techniques

 

- Controlled wound healing ? Controlled wound healing is not indicated if a large osteosynthesis device is exposed. However, synthesis with a screw could be covered by controlled wound healing if the remaining bone still has its periosteum. Minimum exposure could be envisaged if operating conditions are a contraindication for any sophisticated method of coverage. For instance, a not very displaced fracture, with medium exposure, osteosynthesized with a screw with the head buried; in this case and in a medical centre, wisdom would suggest doing controlled wound healing followed by a skin graft. It should, however, be remembered that we are in difficult circumstances and that although what is simple is not always wise, sometimes simplicity is the best.

- Skin graft ? If granulation is of good quality, if no device is exposed and if the context is truly risky, a skin graft could be envisaged.

- Flap ? An open fracture combined with exposure of osteosynthesis device requires coverage with a flap.
An open fracture in the upper third of the leg or tibial plateau tibial is, in most cases, secondary to a direct shock. In an emergency situation, determining tissue contusion is often difficult. Some authors, rightly, advise against doing a skin flap on an open fracture in an emergency. This is because the skin paddle harvested may be the seat of a contusion which initially went unnoticed and it may suffer secondarily at the vascular level. A muscle flap therefore seems more reliable, except that it too can be the seat of a contusion that escaped notice at the beginning. However, it is more resistant in this context and in an emergency. In any event, we can see the importance of initial debridement. In difficult circumstances or at a medical centre we are rarely confronted with a true orthopaedic emergency and in most cases we should offer deferred soft tissue coverage. Secondarily, both coverage variants (skin flap or muscle flap) are satisfactory. You should do the flap that you know the best, whether skin, or pure muscle combined with a skin graft.

 

Our choice: Fasciocutaneous flap from the internal surface of the leg.

With an open fracture of the tibial plateau, we suggest a fasciocutaneous flap from the internal surface of the leg, with a proximal pedicle. It is a flap which is easy to harvest, reliable and which provides a large skin paddle. The disadvantage is the skin “lug” which appears at its base after rotation of the flap and which may require an additional procedure. However, a minimal skin lug can be resorbed spontaneously. In practice, the duration of a mission will not allow for the time to separation so the procedure is carried out in most cases in one go. The skin graft on the donor zone is carried out immediately. It should be noted that this region can also take a muscle flap from the internal gemellus muscle.

a) Anatomical background

The skin paddle does not have a truly individualized vascular pedicle; the flap could be called a free flap. In fact it is a reliable flap (Fig. 8) where:
1) the arterial supply is mainly ensured by the perforans branches of the internal gemellus muscle (musculocutaneous arteries) + the ambient vascularity of the great saphenous vein.
2) the venous return is above all ensured by the saphenous vein.

fig 8

b) Flap contours (Fig. 9 a, b)

Taking these anatomical considerations into account the skin paddle is harvested opposite the internal gemellus muscle to have a maximum of perforans and “carry” the great saphenous vein with the paddle for better vein drainage.
The boundaries of the fasciocutaneous flap from the inside surface of the leg will therefore be: (Fig. 10)
1) to the front, 1cm behind the tibia
2) to the back, the groove between the two heads of the gemellus muscles
3) proximally, 3 to 4 cm under the popliteal crease
4) distally, 1/3 medium – 1/3 distal of the leg

Fig 9 a	fig 9 b

fig 10

c) Position on table (Fig. 11)

The patient is in dorsal decubitus with a cushion under the contralateral buttock. Installation must enable access to the internal and posterior surface of the leg. A tourniquet is placed at the base of the limb. The flap is drawn before pumping out the limb to localize more easily the subcutaneous veins which will be included in the skin paddle. The great saphenous vein will be included in the outline. The posterior incision should, in principle, protect the small saphenous vein which will not be included in the flap.

fig 11

d) Dissection of flap (Fig. 12)

The incision should be made according to the outline and up to the muscle fascia without going beyond it. Distally, the great saphenous vein is fastened and sectioned. It should be taken with the flap. The skin paddle should be manipulated in one piece, delicately in a damp pad, avoiding separation of epidermis from dermis. Simple traction with Gillies’ hooks may suffice. Freeing up the flap of muscle fascia is easy but may require some arrest of bleeding of the musculocutaneous arteries using bipolar cautery.  

fig 12 a,b

e) Rotation of flap (Fig. 13)

The flap is freed up from distal to proximal as required while trying to obtain coverage of the receiving site without tension. No vascular pedicle is individualised. At the end of dissection, correct vascularisation of the flap is checked by making the dermis of the distal skin edge bleed. The flap is sutured with a few simple stitches into its final position. The vitality of the paddle in its new position should be checked once again.

fig 13

 

f) Skin graft (Fig. 14)

The skin paddle is sutured with simple non-absorbable monofilament stitches. An lug of skin may appear at the base of the flap. It will be resorbed in a few months. The donor site is grafted immediately. A mesh graft is preferable since its surface is, generally, quite large. Then, a bolster is placed to keep the graft in place. Care needs to be taken that the dressing does not compress the pedicle of the flap and a window, to be able to monitor the skin paddle, is advised.

fig 14 a,b

 

Conclusion

 

A surgical technique carried out in difficult circumstances should meet the following five requirements: It should be
- able to be carried out whatever the conditions,
- reliable whoever the operator is,
- familiar to the surgeon,
- easy to teach,
- and where the true goal is healing the patient.
To cover the loss of soft tissue of the knee, we propose two techniques that it is essential to be familiar with (and which meet the five requirements above): the fasciocutaneous flap of the inside surface of the leg and the gemelllus muscle flap (internal and external).

 

 

References

One book Flaps in Limb Reconstruction. A.C. Masquelet / A. Gilbert.  1995. Edition Martin Dunitz.

Two web sites www.chirurgieplastiquehumanitaire.net :  site du DIU de Chirurgie Réparatrice en Situation Précaire www.Interplast-France.net :  Site of an NGO in restorative surgery for developing countries.