The current study provides the clinical rationale that the temporary BP and permanent BS can achieve similar clinical and radiographic outcomes in the treatment of distal tibia shaft fractures with IMN. Although the coronal loss of reduction of the BP group is a bit more than that of the BS group, this small difference of about 0.3 degree is not clinically important.
The initial reduction of less than 5 degrees was observed in 83 patients, and 82 patients retained it until the last follow-up. This indicates that a good initial reduction is the key to prevent malunion in the treatment of distal tibia shaft fracture with IMN, which has also been confirmed by other studies. A recent prospective study reported 56 patients with distal tibia shaft fractures fixed with IMNs . 43 patients had good initial alignment (< 5 degrees), 42 patients maintained it until the fracture healed, and only 1 case developed from initial good alignment to malunion due to immediate weightbearing against medical advice. A retrospective study by Vallier et al  reported 76 patients with distal tibia shaft fractures fixed with IMN. 54 patients had good initial alignment of less than 5 degrees, and all of them maintained it until the fracture healed. Similarly, Guerado et al  and Avilucea et al  also suggest that a good initial reduction is the key to prevent malunion. However, the initial mal-reduction rate of the current study is significantly lower than the reported rate of 23%-29%, which may be related to the fact that the blocking technique can help achieve a more predictable and accurate reduction [5, 7].
The BP and BS achieved similar overall alignment. Whilst there was a statistical difference in loss of reduction in the coronal plane between BP and BS groups (P = 0.012), we do not feel that this small difference, of about 0.3 degrees is relevant clinically. The permanent BS may not provide an important clinical improvement in structural stability, which had been confirmed by a recent biomechanical study. Chan et al  evaluated the mechanical stiffness of the reamed IMN with two distal 5-mm interlocking screws augmented with or without a medial BS in the treatment of distal tibia fractures. They concluded that there was no significant difference in mechanical stiffness with or without the BS, and the IMN fixation alone can provide sufficient stability to allow for immediate weight-bearing. Moreover, De Giacomo and Tornetta  retrospectively analyzed 132 distal tibia fractures fixed with an IMN and concluded that IMN with two distal interlocking afford adequate stability to hold the reduction during union. In their study, no significant loss of reduction (average change of 0.9 degrees in both the coronal and sagittal planes) was observed after surgery. However, in an early reported study, Krettek et al  reported that two BSs placed medial and lateral to an 8-mm IMN increased bending stiffness by 57% compared with three interlocking screws without BSs. But the small diameter unreamed IMN and 3.9 mm interlocking screws they used were rarely used today, which may generate heterogeneity.
Previous literature suggested using permanent BS as a supplement to IMN [9, 11, 23, 24]. However, it must be noticed that our and their studies differed in several aspects. First, their patient group included a large number of OTA 43 fractures and fracture nonunions. In the present study, we only selected acute, closed fractures of the distal tibia shaft (OTA 42), which were more stable and easier to heal than previously reported fractures. Second, our pre-placed BP can guide an accurate reaming and subsequent tight bone-nail construct [20, 25, 26]. Third, modern perspective technique allows sufficient visualization. The nail tip can be accurately inserted into the hardest area of the subchondral bone and the distal interlocking screws can be accurately locked to avoid the “wiper effect” (Fig. 1-g) .
In the BS group, it requires an additional intraoperative procedure to replace the temporary Steinmann pins with screws, but in the BP group, the temporary Steinmann pins can be pulled out directly. This explains why the operating time was significantly shorter in the BP group [15, 16, 28]. The Steinmann pin was used during reduction in both groups, and no intraoperative adverse event occured. After surgery, two patients underwent removal of the permanent BS due to soft tissue irritation, but this is not a significant difference (P = 0.139). Of note, one patient in the BP group underwent a 4-degree loss of reduction because the bone around the distal interlocking screws was destroyed during drilling. For such patients, the addition of a permanent BS may get better results.
The major limitation of our study was its nonrandomized design. This allowed selection bias to obscure results as surgeons likely treated more difficult fractures with permanent BSs. Therefore, prospective studies with large sample size are needed to confirm the efficiency of temporary BPs. Another limitation is that we only evaluated acute, closed fractures of the distal tibia shaft, which were more stable and easier to heal. Open fractures and OTA 43 fractures should be an area of future research.