The cavity of the ulcer consists of the ischial bursa but, as the condition progresses and extends, the ischial tuberosity increasingly pro-jects into the cavity and becomes the seat of chronic osteitis. An advance in the treatment of this type of ulcer has been reduction of the prominence of the ischial tuberosity jointly with the appropriate soft tissue surgery. Even where the bone is not pathologically involved it is still the main cause of the ulceration.
When planning the appropriate flap the patient should have the hip flexed to imitate the sitting posture to ensure that residual scars do not overlie the tuberosity. A useful flap is very broadly based medially along the greater part of the thigh and moved upwards.
A virtue in this situation is its generous dimensions which, on the one hand make it extremely safe, and on the other permit further rotation should the ulcer recur. An added advantage is that it provides simultaneous access to the ham-string muscles, and the atrophic remnant of the biceps muscle can be detached at its lower end and mobilised by dividing approximately half of the perforating vessels.
The muscle can then be rolled up and tucked into the dead space left by the ischiectomy.
An alternative possibility is the tensor fasciae latae flap. Used for this purpose the length of the flap required is rather greater than for the trochanteric ulcer, a flap of 30 cm or even more being needed. Where trochanteric and ischial ulcers coexist, the single flap may be able to cover both simultaneously.
Total obliteration of the pressure point by ischiectomy, used in conjunction with an appro-priate flap for skin cover, appeared to be a prom-ising advance when it was first introduced. The late results have shown up its deficiencies. The major defect as in all procedures in the para-plegic is the tendency to recurrent or fresh ulcera-tion.
The body weight has to be supported somewhere, and the effect of surgical procedures
is merely to transfer the pressure to a new area where a fresh sore is liable to develop. Following the use of ischiectomy, sores tend to develop on the posterior aspect of the thigh at trochanteric level and also towards the perineum and scro-tum.
Ulcers in these areas, particularly the perineoscrotal, are extremely intractable, and with flaps already used for ischial sores are very difficult to deal with surgically.
With the ischial ulcer it is better to compromise and, instead of carrying out a formal ischiecto-my, to restrict bony excision to the obvious area of projection.
In the lateral aspect of the thigh the fascia lata is markedly thickened to form the iliotibial tract, receiving into its upper part the insertions of glu-teus maximus behind and tensor fasciae latae further forward. As the tract passes distally it overlies vastus lateralis but there is no attach-ment between the two structures.
Although the fascia lata encircles the thigh the thickening which constitutes the iliotibial tract virtually ceases along a line dropped vertically from the anterior superior iliac spine. The tensor fasciae latae muscle is perfused in its lowest part from the ascending branches of the lateral femoral circumflex vessels which reach it about the level of the pubic tubercle. This supply appears to extend into the upper two-thirds of the iliotibial tract.
The tensor fasciae latae myocutaneous flap is
designed on the lateral aspect of the thigh with its base superior, and makes use of the iliotibial tract as its ‘muscular’ element. Its anterior bor-der runs vertically along a line brought just lateral to the anterior superior iliac spine in order to avoid the lateral cutaneous nerve of thigh. Its posterior border approximates to the line running down from the greater trochanter.
The length of the flap is determined by the geometry of the transfer but it can safely extend to the junc-tion between the upper two-thirds and the lower third of the thigh. The flap is technically easy to raise because the plane between the tract and vastus lateralis is so well defined and avascular. It can be raised proximally to the level of the pubic tubercle.
Its usual use is as a transposed flap, moved posteriorly to cover a defect of
trochanter and/or ischium. The secondary defect is split skin grafted as a rule.
Although discussion of pressure sores in the paraplegic patient is confined to the problems of reconstruction, it cannot be emphasised too strongly that the procedures to be described for the various types of decubitus ulceration are only a small facet in the overall care of the paraplegic, and they must be regarded as merely providing the ulcerated area with a fresh start in the best conditions.
The sites in the paraplegic which are particu-larly liable to develop pressure sores lie over the pressure-bearing bony prominences.
Compared with the sores which develop in the non-para-plegic, the ulcers tend to have an ‘iceberg’ qual-ity, with extensive undermining, and osteitis of
the underlying bone, or even pyoarthrosis in severe cases. Surgical treatment consists of the covering of the completely excised ulcer with a movable pad of healthy skin and subcutaneous tissue, and simultaneous reduction of any under-lying bony prominence which appears to be acting as a focal pressure point.
This latter proced-ure is generally essential, since such promi-nences left untouched reproduce the mechanical pressure which was responsible for the original ulcer.
During the acute phase of the spinal injury, the common sites are over the sacrum and femoral trochanter; after recovery, prolonged sitting in a wheelchair makes the ischial area the most frequent site.
Sacral ulcers tend to be large and flat with minimal undermining; ulcers of the trochanter and ischium usually have a small opening, leading into a large slough-lined cavity into the base of which the bony prominence projects.
The anaesthetic tissues of the paraplegic heal
poorly, and with the slightest provocation the wound will fail to heal following surgery.
Tension on suture lines must be avoided, haemostasis must be even more meticulous than usual, cavities and dead space must be positively eliminated -failure in any one aspect will result in failure as a whole. If skin loss is minimal, exci-sion and direct closure may suffice, but in most instances a flap is needed. The secondary defect created by transfer of the flap has often to be grafted and, as discussed on p. 88, the graft need not necessarily be applied at the time of the flap transfer.
The collection of a haematoma under the flap is particularly undesirable in the para-plegic patient, and leaving the secondary defect ungrafted in this way is a valuable way of ensur-ing that a large area is available through which any haematoma can drain instead of collecting under the flap to cause tension, infection and necrosis. The graft can be applied 7-10 days later.