Reverse wedge effect following intramedullary nailing of a basicervical trochanteric fracture variant combined with a mechanically compromised greater trochanter

BACKGROUND: To introduce an unreported intraoperative complication in intramedullary nailing (IN) of an anatomically reduced trochanteric fracture variant characterized by a basicervical fracture line and coronally disrupted greater trochanter (GT). METHODS: A total of 414 trochanteric fractures (TF) treated with intramedullary nails from 2013 to 2017 were included in this study. After analysis of intraoperative fluoroscopy data, 33 cases, including 21 females and 12 males, with a mean age of 72.5 years (33 to 96 years) were identified for internal rotation of the cephalocervical fragment and inferior opening at the basicervical fracture line caused by nailing a satisfactorily reduced TF. The morphological features of this group of patients were analyzed on computed tomography (CT) scan. On radiograph, the magnitude of the displacement and final femoral neck-shaft angle (NSA) were measured. RESULTS: CT analysis demonstrated that the basicervical fracture line and the posterolateral fragment (PLF) detached from the GT were the two dominant features of this cohort. They were classified according to the number of main fragments: a 3-fragmentary subgroup containing three consistent fragments (cephalocervical fragment, PLF and distal femoral shaft) and a 4-fragmentary subgroup embracing one additional fragment (lesser trochanter). The four subtypes were as follows: the 3-fragmentary S indicating a small PLF (6 cases), the 3-fragmentary M presenting a moderate PLF (3 cases), the 3-fragmentary L standing for the PLF involving whole lesser trochanter (LT) (4 cases) and the 4-fragmentary GL incorporating separated PLF and LT fragments (20 cases). Geological analysis demonstrated that the majority of the basicervical fracture lines (81.8%) just crossed the center of the piriformis fossa, while the others marginally involved the medial wall of the GT. Postoperatively, the mean width of the inferior opening at the basicervical region was 9.2 ± 4.6 mm. The mean NSA was 135.2 ± 7.8 degrees. The comparison between the 3- and 4-fragmentary subgroups revealed no significant differences in magnitude of displacement and NSA. CONCLUSION: This unreported intraoperative complication predominantly occurred in the intramedullary nailed basicervical trochanteric fracture variant combined with a PLF from the GT. The magnitude of the secondary displacement was substantial and resulted in a relative valgus reduction. This secondary displacement was caused by an impingement of the reamer with the superolateral cortex of the cephalocervical fragment and should be addressed during the operation. LEVEL OF EVIDENCE: Therapy IV.