There is a high incidence of rotational malalignment following intramedullary-nailing for tibia shaft fractures with incidences up to 30% [1,2,3,4,5,6,7]. An intraoperative fluoroscopy protocol to increase accuracy of alignment control during intramedullary-nailing of these fractures is still lacking. This study is the first to present an accurate and clinically feasible standardized intraoperative fluoroscopy protocol coined ‘C-Arm Rotational View (CARV)’ in order to minimize the risk on rotational malalignment, and to avoid rotational outliers during intramedullary-nailing of tibia shaft fractures.
Our primary findings demonstrate that tibial alignment during intramedullary-nailing of tibia shaft fractures can be significantly improved using the CARV-protocol. Only 12% of the corrections were categorized as unacceptable rotational alignment (≥10°). Second, we found that clinical estimation of rotation followed by realignment of the tibia according to present clinical standards is inaccurate. A total of 67% of the rotational corrections after single-leg draping and 58% after dual-leg draping resulted in unacceptable rotational alignment (≥10°). Application of the CARV relative to current clinical practice decreased the rate of rotational alignment from 67 and 58% to 12%, respectively (p < 0.001).
This study should be interpreted considering strengths and weaknesses. The CARV-protocol was tested in cadaveric specimens in which only a transverse mid-shaft fractures was simulated instead of different fracture patterns. We felt that incorporating a mid-shaft fracture in the study setup allowed for adequate measuring of tibia (mal)alignment using reference wires on both fracture sites. We believe that the simplified nature of our test setup does not disqualify our findings. Moreover, CARV was successfully applied in the case series that included different fracture patterns. Although proven to be clinically feasible, prospective clinical studies are needed to clinically validate the CARV-protocol on a larger scale. Secondly, the CARV-method works under assumption that each individual has almost symmetric tibias leading to symmetric radiographic landmarks. A previous study by our group demonstrated a potential physiological difference of 4° between the right and left tibiae . We believe that the small difference between the right and left tibiae does not have compromised the performance of CARV-protocol in this experimental study.
In femoral shaft fractures, multiple simple intraoperative fluoroscopy protocols have been described to avoid rotational malalignment after intramedullary-nailing [20,21,22,23,24]. Similarly, the potential of rotational malalignment following intramedullary-nailing for tibia shaft fractures can be minimized by simple application of the CARV-protocol. Some methods for avoiding rotational malalignment have been described in literature. Recently, a case report reported on the perfect lateral view of the ankle in order to obtain adequate alignment during intramedullary-nailing for tibia shaft fractures . However, this technique was not tested or validated in a research setting confirming its accuracy and usability. Clementz et al.  introduced a fluoroscopy-technique in 1989 measuring the angle between femur and ankle by assessing the overlap of the anterior and posterior cortex of the medial malleolus. This technique did not find its way in standard clinical practice despite multiple attempts to endorse its feasibility [29, 30].
Correction according to present clinical standards using either single-leg or dual-leg seemed to be insufficient in this experimental study, and has proven insufficient in multiple clinical prospective cohort studies [1,2,3,4,5,6,7]. This inaccuracy may be caused by (1) difficulties in clinical estimation and (2) the absence of a standardized fluoroscopy protocol to obtain adequate alignment. Among observers, the cortical step sign (CSS) and diameter difference sign (DDS) was used for alignment control . Although Keppler et al.  proved the CSS and DSS to be reliable landmarks to detect and correct for malrotation, we feel that the clinical feasibility is limited due to differences in fracture patterns and possible axial translation of the tibia caused by the eccentric position of the intramedullary-nail in the tibia shaft.
The first advantage of the CARV-protocol was the use of the C-arm as simple and accurate indicator for rotational malalignment rather than inaccurate clinical judgment. The C-arm was able to detect a 5° rotational difference between both injured and uninjured limb by revealing sufficient small fluoroscopy alterations of the proximal tibiofibular overlap and mortise-view of the ankle (Fig. 2). A second asset of the CARV-protocol includes the simple standardization of rotational correction techniques. The need for such was strengthened by the existence of a wide range of insufficient correction techniques among observers which resulted in relatively high rates of unacceptable rotational outcomes. We found no relationship between level of experience and successful application of the CARV-technique, and finally, the CARV-protocol has proven to be accurate in a clinical setting with different fracture patterns underlying its potential practicability and reproducibility in clinical practice.