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.