Heat-induced segmental necrosis after reaming of one humeral and two tibial fractures with a narrow medullary canal.

In three cases referred to our clinic (a simple fracture of the humeral shaft, a simple, closed fracture, and a wedge fracture of the mid-third of the tibia), bone necrosis had resulted from excessive heat produced by reaming extremely narrow medullary cavities (5-5.5 mm diameter) with the 9 mm front-cutting reamer as part of a reamed nailing procedure. In any one case, different degrees of damage can occur from the metaphysis to the diaphysis. Based on the clinical course and the histological evaluation, we postulate that heat-induced damage can be divided into four degrees of severity (0-3): Grade 0: no damage; no devascularization, no heat-induced damage. Grade 1: The heat damaged zone is cut away during subsequent reaming, the only damage is devascularization. Grade 2: The damaged zones are not eliminated by subsequent reaming. The bone is devascularized and heat damaged. Grade 3: The entire cross section of the bone including the periosteum is devitalized by exposure to excessive heat. Depending on the severity of additional damage to the soft tissues, grave consequences are to be expected and further operations are unavoidable. The effects of heat-induced damage are particularly critical in the presence of infection (cases 2 and 3). The fundamental aspects and the extent of heat necrosis will be discussed. After discussion with the AO Technical Commission on the cause of heat-induced necrosis, we would recommend the following preventive measures: 1. preoperative measurement of the smallest diameter of the medullary cavity in two planes. 2. reaming with the standard instrumentation (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 be 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.