Intramedullary nails have become the mainstream treatment for intertrochanteric fractures due to their advantages of being minimally invasive and biomechanics features. However, with the widespread use of intramedullary nails, the distal locking procedure as a routine operation gradually raised controversy. Complications emerged associated with distal locking, including fascia lata irritation, secondary femoral fractures [5, 9, 10], thigh pain, and erosion of the femoral cortex, femoral cortical hypertrophy and superficial femoral artery [8]. Due to this emerging problem, in some studies the utility of using distal interlocking screws in their biomechanical studies was investigated, demonstrating that distal locking was unnecessary in stable and in some unstable intertrochanteric fractures [6, 21-26]. In many studies, the outcomes of distal locking and unlocking in the intramedullary nailing for the treatment of intertrochanteric fractures was compared, however, clear inconsistency in treatment effects were described in these studies. Thus, the optimal method to deal with distal locking during nailing of intertrochanteric fractures remains controversial [12-20]. Therefore, the purpose of this meta-analysis and systematic review was to summarize existing evidence to determine the safety and efficacy of distal locking and unlocking in the nailing of intertrochanteric fractures. To our knowledge, no similar meta-analysis has been performed.
Summary of evidence
This study considered 9 articles that included a total of 1978 patients with a similar baseline. The results showed that the distal unlocking group had a shorter operation time, less intraoperative bleeding, transfusion rate, and thigh pain in the treatment of femoral intertrochanteric fracture when compared with the distal locking group. No significant differences in safety-related outcomes, including mortality, infection rate, cutting out, loss of reduction, backing out of lag screws, cephalic screw breakage, nail breakage, and peri-implant fractures was found. In addition, efficacy-related outcomes, including nonunion, delayed healing rates, and the Harris functional score were not significantly different. According to the GRADE tool, most of these outcomes were graded as low-moderate.
Consistent with the foregoing expected results, the operative time, blood loss, rate for blood transfusion, and radiation exposure in ULN were significantly reduced when compared with LIN. The operating time was shorter and radiation exposure was les because of less surgical procedures. The reason for the low amount of blood loss was mainly due to smaller trauma and a shorter operation time. The short operation time and the small amount of intraoperative blood loss minimize the anaesthetic effect on respiration and blood circulation, and represent an advantage for the recovery of elderly patients after surgery. Reduced transfusion implies a reduced risk of disease transmission, transfusion reactions, and immunomodulation, and it reduces the costs of the transfusions [27]. Less radiation exposure can reduce harm and increase the protection for both patients and surgeons. A statistically significant difference of heterogeneity existed due to different hospitals that calculated the operating time and blood loss, different internal fixation, and the inconsistency of surgeon proficiency.
The overall results regarding thigh pain were significant, suggesting that the use of distal screw might be harmful. This is consistent literature reports [12, 15, 16, 18]. However, when subgroup analysis was performed, differences were not significant, suggesting that the reliability of these findings was not strong.
Two approaches exist to lock distal nails: static locking and dynamic locking. Most included studies did not distinguish between the two approaches. In the study by Ciaffa et al., their prospect comparative analysis was expanded, including static locking vs dynamic locking vs no locking. No significant differences were observed across the three groups regarding major radiological performancce of fracture union, malunion, as well as regarding HHS, SF-12 and Barthel index results after 1-year follow-up[13].
The occurrence of cut-out and nonunion after cephalomedullary nailing of stable pertrochanteric fractures appeared to be correlated to the presence of cortical impingement[28]. Therefore, a fake unlocked femoral nail with cortical impingement should be avoided in stable intertrochanteric femur fractures.
Disagreements with other studies
Rates of peri-implant fractures were similar in both LIN and ULN groups and therefore not statistically significant. However, the data were heterogeneous (P=0.010; I²=67%), mainly due to the Skala-Rosenbaum et al. study [18]. After removal of this article, although the conclusion remains unchanged, the heterogeneity significantly decreased (P=0.82; I²=0%). In the present study, after analysing a group of 849 pertrochanteric fractures managed with short nails, we found that patients without distal locking had an 85.7% higher risk of peri-implant fractures. This finding is different from the results of all clinical and biomechanical studies considered in our work. Methodologically speaking, the reason of this difference may be due to the absence of random and blind methods in the study by Skala-Rosenbaum et al., and in addition, the baseline and weight-bearing time between the two groups were not introduced. Clinically speaking, the difference might theoretically be related to the fracture type or the inappropriate selection of patients for unlocked nailing, whose fracture should be a stable fracture for this choice of using unlocked nailing, because the dorsomedial fragment or the existence of recessive fracture is often difficult to detect by ordinary X-ray evaluation [18, 29]. In addition, peri-implant fractures are associated with instability. The stability is not only related to internal fixation, but also to surgical reduction. Poor surgical reduction can also lead to instability [30]. The study by Skala-Rosenbaum et al. did not mention the effect of post-operative reduction. Furthermore, their study did not give a detailed description of the tip apex distance and the position of the head nail, which are closely related to the stability.
Strengths and limitations
This meta-analysis has some limitations. 1. The nine articles included 1978 cases of intertrochanteric fractures of the femur. Five of them were observational studies. Some defects were present in the research design, and the performance of the statistical tests may be insufficient. 2. The nine articles involved did not describe each measurement and outcome in detail, and the validity of the statistical tests may be insufficient. We tried to contact the authors of the included studies for more information, however, we did not receive any response regarding the possibility to check the data of their study. Therefore, subgroup analysis of some aspects, including fracture types, intramedullary nails, and complications to rule out possible confounding factors was not performed, thereby affecting the effectiveness of our study. 3. The inconsistency about nails length, number or type of cephalic screws and angle between cephalic screws are unclear aspects that make our results questionable.
Further research should be performed considering larger, multicenter, randomized controlled studies that take into account the need for large clinical trials with a valid, type-specific fracture and uniform method for the measurement and definition of the outcome. We recommend that CT should be performed to identify the type of fracture as stable before deciding to use distal locking nails. Patients with wide diameters of the medullary cavity, comminution of the lateral wall of the greater trochanter, and large posteromedial fragment extending distally below the lesser trochanter should not be considered for unlocked intramedullary nailing. Current studies mainly focus on short nails, but relatively few on long nails. Therefore, this study of long intramedullary nailing for intertrochanteric treatment should be properly enriched with other studies performed as recommended above.