HEAT-INDUCED SEGMENTAL NECROSIS AFTER REAMING OF ONE HUMERAL AND 2 TIBIAL FRACTURES WITH A NARROW MEDULLARY CANAL

In three cases referred to our clinic (a simple fracture of the humera l shaft, a simple, closed fracture, and a wedge fracture of the mid-th ird of the tibia), bone necrosis had resulted, from excessive heat pro duced by reaming extremely narrow medullary cavities (5-5.5 mm diamete r) with the 9 mm front-cutting reamer as part of a reamed nailing proc edure. In any one case, different degrees of damage can occur from the metaphysis to the diaphysis. Based on the clinical course and the his tological evaluation, we postulate that heat-induced damage can be div ided into four degrees of severity (0-3). Grade 0: no damage; no devas cularization, no heat-induced damage. Grade 1: The heat damaged zone i s cut away during subsequent reaming, the only damage is devasculariza tion. Grade 2: The damaged zones are not eliminated by subsequent ream ing. The bone is devascularized and heat damaged. Grade 3: The entire cross section of the bone including the periosteum is devitalized by e xposure to excessive heat. Depending on the severity of additional dam age to the soft tissues, grave consequences are to be expected and fur ther operations are unavoidable. The effects of heat-induced damage ar e particularly critical in the presence of infection (cases 2 and 3). The fundamental aspects and the extent of heat necrosis will be discus sed. After discussion with the AO Technical Commission on the cause of heat-induced necrosis, we would recommend the following preventive me asures: 1. preoperative measurement of the smallest diameter of the me dullary cavity in two planes. 2. reaming with the standard instrumenta tion (9 mm) only if the medullary cavity has a diameter of at least 8 mm at its narrowest point. 3. Extremely narrow cavities should first b e reamed manually or an alternative to nailing should be sought. 4. It is strongly recommended that only sharp reamers be used in such cases and blunt or damaged reamers replaced.