THE CHALLENGES ASSOCIATED WITH TREATING DISTAL FEMORAL FRACTURES WITH LOCKING PLATES IN THE ELDERLY: DIFFERING PATTERNS OF FAILURE WITH DIFFERENT LOCKING PLATES

Abstract

Despite advances in Locking Plate (LP) design, distal femoral fractures remain challenging injuries to treat especially in the elderly where approximately 15–30% develop nonunions secondary to failure of fixation.

Aim: To establish the mechanisms of nonunion in our patient population using two different LP systems.

Methods: Between December 2002-May 2008, we prospectively collected data on all 67 patients with distal femoral fractures who were treated using a suitable distal femoral LP (LISS, 35 cases, or Periloc, 32 cases). 72% of the patients were female; ages ranged from 25–94 years (ave. 67 years). Many of our patients had a number of significant co-morbidities.

Results: The presence of significant co-morbities e.g. Rheumatoid arthritis, long term systemic steroid use, cerebrovascular accidents resulting in ambulatory problems, previous major joint arthroplasty including ipsilateral knee replacements, paralysis, and severe dementia, did not appear to influence fracture union significantly. However, old age was strongly correlated with nonunion with all failed cases (7 patients - 10% of the study group) presenting with failure of fixation. 2 of the LP system failures resulted in malunion and the 5 other cases required revision surgery. Of note, all 7 patients were elderly, 6 being over 80 years of age. The mechanism of fixation failure was specific to each of the LP systems. All 4 of the failures treated with LISS, resulted from poor proximal stability as a consequence of unicortical screw fixation. Two patients required to have the proximal fixation revised through the insertion of bicortical screws which subsequently resulted in successful union. The other two patients were treated in long leg casts as the varus deformities were considered acceptable given each patient’s needs. All 3 of the failures who had been treated with a Periloc LP, resulted from fracturing of the plate at the metaphyseo-diaphyseal junction at the level of the main extra-articular component of the fracture. The plates all fractured through the unfilled screw holes, and all 3 patients required revision of fixation to bring about union.

Discussion: The LISS failures can all be attributed to poor proximal fixation that is associated with the use of unicortical screws in osteoporotic bone and confirms the need for bicortical screw fixation. However, modern LP systems manufactured from stainless steel offer increased implant stability that may in turn stress any fracture bridging segments of the LP.

Conclusion: Although we are aware of the importance of bicortical screws in osteoporotic patients, it is also seems likely that excessive plate rigidity should be avoided, by using long plates with well spaced out screws.