Pressure in plaster backslabs after surgery for ankle fractures.

Concern over the safety of applying a cast when postoperative swelling might be expected, prompted a study of the pressure inside backslabs. Using a modified Sengstaken tube, pressure measurements were taken from blackslabs applied for temporary support after open reduction and internal fixation of 15 ankle fractures. The mean pressure rise was 4.6 cmH2O (3.4 mmHg), the maximum increase in any cast was 18 cmH2O (13.2 mmHg), and the maximum pressure reached was 27.5 cmH2O (20.2 mmHg). There were no clinical signs or symptoms of excessive compression by the cast and in all cases the pressure had reached its maximum and begun to fall within 3 h of the operation. The ankle swelling associated with injury and surgery seems not to produce an unacceptable pressure rise within backslabs applied postoperatively.