3D printed personalized titanium plates improve clinical outcome in microwave ablation of bone tumors around the knee

Abstract

Microwave ablation has been widely accepted in treating bone tumor. However, its procedure is time-consuming and usually results in postoperative fractures. To solve this problem, we designed and fabricated titanium plates customized to the patients' bone structures. The personalized titanium plates were then used for fixation after the removal of tumorous tissue. Specifically, 3D models of tumor-bearing bone segments were constructed by using computed tomography (CT) and magnetic resonance imaging (MRI). The 3D models were used to design the personalized titanium plates. The plate model was transferred into a numerical control machine for manufacturing the personalized titanium plates by 3D printing. The plates were then surgically implanted for reconstruction assistance following microwave-induced hyperthermia to remove the bone tumor. Implementation parameters and knee functions were then evaluated. No postoperative fractures, implant failures or loosening problems occurred; mean Musculoskeletal Tumor Society score was 27.17 from the latest follow-up. Mean maximum flexion of affected knees was 114.08°. The results of knee gait analysis were comparable with normal population data. Our work suggests that personalized titanium plates can significantly improve the clinical outcomes in the surgical removal of bone tumor. This study represents the first-time effort in using personalized titanium plates for such surgery.

Figure 1

The current global procedure for the designed clinical study. (A) CT scan is first performed on the tumorous bone. (B) The MRI scan image is then performed on the tumorous bone. (C) In accordance with the merged CT-MR image, a 3D model of the tumorous bone is constructed using Mimics software, with tumor being highlighted in red. (D) The 3D model shown in C is then used to design a personalized titanium plate (pink) using UG software. (E) 3D printing is used to print the bone model shown in (C). (F) A numerical control machine is used to fabricate the personalized titanium plate shown in (D). (G) The fabricated titanium plate is combined with the 3D printed tumorous bone to match the model shown in (D) in order to test if the plate matches the tumorous bone as modeled. (H) The fabricated personalized plate is then used to fix the bone structure after the surgery removal of osteosarcoma and the bone repair using the mixture of allograft bone and cement. (I) The recovery of the patient is followed by X-ray examination and gait analysis.

Figure 2

The modeling of the tumorous bone and personalized titanium plate as well as the matching between the tumorous bone and the titanium plate. (A) The 3D model of the tumorous bone was constructed with Mimics software according to the merged CT-MR data. (B) The 3D model of the tumorous bone is matched with a personalized titanium plate model (pink) using UG software. (C) The resultant 3D model is filled with screws in order to show the required number as well as the location and lengths of the screws that will be used during the operation. (D) The 3D printed tumorous bone model is matched with a fabricated personalized titanium plate.

Figure 3

Preoperative imagological data. (A,B) Malignant tumor in the left distal femur was observed in anteroposterior (A) and lateral (B) X-ray radiographs. (C,D) Malignant tumor was confirmed from T1-weighted (C) and T2-weighted (D) magnetic resonance images. (E) Positron emission tomography-computed tomography was carried out to confirm the absence of metastasis.

Figure 4

Surgical procedure. (A) Bone tumor was separated from the surrounding normal tissues with an adequate margin. (B) Microwave ablation of the tumor tissue was performed in situ. (C) The ablated tumor tissue was removed. (D) The resultant bone defect was filled with the mixture of allograft bone and cement, followed by the fixation with the personalized titanium plate. (E) The lateral collateral ligaments were sutured to the lateral epicondyle.

Figure 5

Postoperative radiographs and functional evaluation of knee joint. (A,B) Postoperative anteroposterior (A) and lateral (B) radiographs showed that the personalized titanium plate was well-matched to the bone surface. (C,D) Limb function was evaluated with a novel knee gait analysis system (C), which is schematically shown in (D). The gait analysis system is equipped with an integrated two-head stereo-infrared camera, infrared light-reflecting markers, a workstation computer with custom software and a treadmill. When the patients were walking on the treadmill, the trajectories of markers attached to the thigh and shank were captured by the stereo-infrared camera, and the tibiofemoral gait analysis was performed in real time.