Wide en bloc resection is critical for both primary malignant bone tumors and solitary bone metastases [30]. As the standard technique allows visualization of the osteotomy bone surface only through healthy and uncontaminated tissue, sometimes for large soft tissue masses, more soft tissue exposure is required [26]. In addition, the placement of osteotomy guide plates and prosthesis is often limited to the surgical window and surrounding soft tissue [31]. Therefore, we initially designed two combined approaches for tumor resection and pelvic reconstruction. Only one patient who underwent marginal excision developed local recurrence at 3 months after surgery. This complication did not occur in the other five patients, even including the patient who had died at the last follow-up. This is not surprising because previous studies have verified that there is a significant relationship between the incidence of local recurrence and the surgical margin [32], with 70%-100% of local recurrence cases resulting from marginal and intralesional resection [33]. In addition, there were no cases of nerve damage, skin necrosis or dislocation in the study. Some advantages of this combined approaches were observed. First, it could achieve the adequate exposure of soft tissue and facilitate the positioning of the guide plates and prostheses. Second, the contour of the tumor was visualized through different windows; as a result, the traction of the muscles and neurovascular bundles could be reduced. Third, this approach could reduce the risk of intraoperative tumor contamination, resulting in a lower rate of tumor recurrence. Last, it could efficiently preserve the blood supply by alleviating skin tension.
Rigorous preoperative planning is crucial in pelvic tumor surgery. Using a 3D-printed proportional pelvic model, surgeons can simulate hands-on surgical resection and reconstruction prior to the real operation [33]. Some cadaveric studies have already proven noninferior osteotomy accuracy using 3D-printed guide plates compared to navigation systems [31, 34]. Nevertheless, because of the complicated preparation for the navigation procedure, the operative duration may increase and result in more bleeding [25]. In addition, the cost is another great disadvantage of surgical navigation system [35]. Gerant et al. [36] reported that major blood loss occurred during osteotomy. Osteotomy guide plates can help surgeons perform multiplanar osteotomy, achieve precise resection margins, shorten the operative duration and reduce intraoperative blood loss. In our series, pathological margins were negative after bone tumor resection. According to previous studies, the mean operative duration and intraoperative blood loss ranged from 258–445 min and 2206–6210 ml, respectively [7, 11, 19, 21, 22, 32, 36]. In the current study, the mean operative duration and intraoperative blood loss were reduced to 333 min and 1416 ml, respectively. Thus, the use of 3D-printed osteotomy guide plates was considered a key point to accelerate the osteotomy procedure.
Consideration should be taken by surgeons that many various complications may occur following pelvic reconstruction. In a systematic review [8], the overall complication rate after pelvic reconstruction was 50%. As the most common, deep infection accounted for 14% of complications. Ji et al. [22] noted that neoadjuvant chemotherapy could have a negative influence on wound-related complications. In our series, no wound-related complications, such as necrosis, seroma or dehiscence, were identified. Moreover, there were no cases of infection, even in the two patients who accepted preoperative neoadjuvant chemotherapy. We contributed these results to the use of intraoperative osteotomy guide plates and the design of the two combined approaches, which reduced the operative duration, blood loss and impact on soft tissue. Six patients all described significant alleviation of pain after surgery. The mean VAS score at 4 weeks and the mean MSTS score at 12 weeks postoperatively were 2 and 15.6, respectively, which are similar to those in the other studies [7, 11, 19, 21–24, 32, 38].
As another complication after pelvic reconstruction surgery, aseptic loosening occurs in up to 12% of patients due to the poor matching degree of conventional prostheses [36]. In our series, no cases of aseptic loosening, screw breakage, heterotopic ossification or periprosthetic fracture occurred. 3D-printed prostheses can precisely match any shape of residual pelvic and avoid repeated adjustments. The design of a porous metal surface permits osseointegration at the bone-implant interface, which is vital for implant longevity [2, 11, 26, 39]. In addition, poly-axial screws can also minimize shear stress to provide mechanical stability. Aside from these factors, the short follow-up period may be another reason for these results. Caution is advised if unexpected bone loss occurs during the operation, as it may be difficult to adapt the 3D-printed prostheses to the bone defect.
This study has some limitations. First, our 3D models were generated merely based on CT data, which may neglect the spread of the tumor within the bone. Second, the small sample size with a short follow-up limited this study. More cases should be included for further study, and we will continue to follow these patients.