Analysis of characteristics and causes of postoperative invalid fixation failures of femoral intertrochanteric fractures / 中华创伤杂志

ABSTRACT

Objective:To investigate the characteristics of postoperative internal fixation failures of femoral intertrochanteric fractures and analyze the related reasons using the leverage-balance-reconstruction theory.Methods:A retrospective case series study was performed for 40 patients suffering from implant failure after internal fixation of femoral intertrochanteric fractures admitted to Peking University People's Hospital from January 1999 to December 2019. There were 20 males and 20 females, aged from 43 to 92 years [(74.1±11.5)years]. The patients were assigned to extramedullary fixation (extramedullary fixation group, 17 patients) and intramedullary fixation (intramedullary fixation group, 23 patients). Complications associated with internal fixation were recorded, including internal fixation cutout, coxa vara deformity of hip joint, internal fixation withdrawal, femoral heck shortening and internal fixation breakage. Based on the lever-balance-reconstruction theory, the failure reasons of internal fixation were analyzed in combination with the change of arm length and outward shift of fulcrum measured before operation, after internal fixation and after fixation failure.Results:Among 40 patients, internal fixation cutout occurred in 18 patients, coxa vara deformity of hip joint in 37, internal fixation withdrawal in 29, femoral neck shortening in 37 and internal fixation breakage in 3. In extramedullary fixation group, the lengths of primary power arm and resistance arm were (8.0±1.0)mm and (59.4±10.9)mm, the lengths of power arm and resistance arm after fixation were (72.7±21.7)mm and (8.9±7.4)mm, the lengths of power arm and resistance arm after fixation failure were (50.3±14.9)mm and (33.6±17.6)mm. In intramedullary fixation group, the lengths of primary power arm and resistance arm were (6.7±0.6)mm and (49.8±9.9)mm, the lengths of power arm and resistance arm after fixation were (51.5±7.0)mm and (19.8±5.9)mm, the lengths of power arm and resistance arm after fixation failure were (41.6±9.6)mm and (32.4±7.7)mm. In each group, the lengths of power arm and resistance arm after internal fixation showed significant differences from that of normal ones and from that after fixation failure ( P<0.05). The length of power arm in extramedullary fixation group was larger than that in intramedullary fixation group ( P<0.05). The shortening of power arm in extramedullary fixation group was larger than that in intramedullary fixation group after fixation failure ( P<0.05). Conclusions:The extramedullary and intramedullary fixation of femoral intertrochanteric fractures result in the displacement of reconstruction fulcrum. The shortening of power arm is observed after fixation failure. The leverage-balance-reconstruction theory is helpful to analyze the cause of complications. The power arm after extramedullary fixation is longer than that after intramedullary fixation and is therefore more prone to fixation failure. The primary cause of postoperative internal fixation complications is to achieve a new balance of leverage.