Post-operative fracture risk assessment following tumor curettage in the distal femur: a hybrid in vitro and in silico biomechanical approach

The effect of defect size and location on the fracture risk of proximal tibia, following tumor curettage and cementation: An in-silico investigation

Even though, proximal tibia is a common site of giant cell tumor and bone fractures, following tumor removal, nonetheless very little attention has been paid to affecting factors on the fracture risk. Here, nonlinear voxel-based finite element models based on computed tomography images were developed to predict bone fracture load with defects with different sizes, which were located in the medial, lateral, anterior, and posterior region of the proximal tibia. Critical defect size was identified using One-sample t-test to assess if the mean difference between the bone strength for a defect size was significantly different from the intact bone strength. Then, the defects larger than critical size were reconstructed with cement and the mechanics of the bone-cement interface (BCI) was investigated to find the regions prone to separation at BCI. A significant increase in fracture risk was observed for the defects larger than 20 mm, which were located in the medial, lateral and anterior regions, and defects larger than 25 mm for those located in the posterior region of the proximal tibia. Furthermore, it was found that the highest and lowest fracture risks were associated with defects located in the medial and posterior regions, respectively, highlighting the importance of selecting the initial location of a cortical window for tumor removal by the surgeon. The results of the BCI analysis showed that the location and size of the cement had a direct impact on the extent of damage and its distribution. Identification of critical regions susceptible to separation at BCI, can provide critical comments to surgeons in selecting the optimal cement augmentation technique, which may ultimately prevent unnecessary surgical intervention, such as using screws and pins.

Postoperative Fracture Risk in Giant Cell Tumor: A Case Report and Review of Literature

Giant cell tumor (GCT) of the proximal femur poses various challenges in its management and recurrence. We present a rare case of GCT of proximal femur in which recurrence and coxa vara deformity were encountered after index surgery. Management of the recurrence was done with intramedullary fixation with extended curettage and bone grafting. Different aspects of management such as the role of defect size, adjuvants, bone cement/bone graft, implants, and bisphosphonates have been highlighted in this article.

Risk factors of fracture following curettage for bone giant cell tumors of the extremities

BACKGROUND

Following curettage of giant cell tumor of bone (GCTB), it is common to fill the cavity with polymethylmethacrylate (PMMA) bone cement, bone allograft, or artificial bone to maintain bone strength; however, there is a 2-14% risk of postoperative fractures. We conducted this retrospective study to clarify the risk factors for fractures after curettage for GCTB of the extremities.

METHODS

This study included 284 patients with GCTBs of the extremities who underwent curettage at our institutions between 1980 and 2018 after excluding patients whose cavities were not filled with anything or who had additional plate fixation. The tumor cavity was filled with PMMA bone cement alone (n = 124), PMMA bone cement and bone allograft (n = 81), bone allograft alone (n = 63), or hydroxyapatite graft alone (n = 16).

RESULTS

Fractures after curettage occurred in 10 (3.5%) patients, and the median time from the curettage to fracture was 3.5 months (interquartile range [IQR], 1.8-8.3 months). The median postoperative follow-up period was 86.5 months (IQR, 50.3-118.8 months). On univariate analysis, patients who had GCTB of the proximal or distal femur (1-year fracture-free survival, 92.5%; 95% confidence interval [CI]: 85.8-96.2) presented a higher risk for postoperative fracture than those who had GCTB at another site (100%; p = 0.0005). Patients with a pathological fracture at presentation (1-year fracture-free survival, 88.2%; 95% CI: 63.2-97.0) presented a higher risk for postoperative fracture than those without a pathological fracture at presentation (97.8%; 95% CI: 95.1-99.0; p = 0.048). Patients who received bone grafting (1-year fracture-free survival, 99.4%; 95% CI: 95.7-99.9) had a lower risk of postoperative fracture than those who did not receive bone grafting (94.4%; 95% CI: 88.7-97.3; p = 0.003).

CONCLUSIONS

For GCTBs of the femur, especially those with pathological fracture at presentation, bone grafting after curettage is recommended to reduce the risk of postoperative fracture. Additional plate fixation should be considered when curettage and cement filling without bone grafting are performed in patients with GCTB of the femur. This should be specially performed for those patients with a pathological fracture at presentation.

Biomechanical and fracture characteristics of different filling and fixation methods applied to various proximal tibial metaphyseal defect sizes in an ovine model

BACKGROUND

Ideal treatment method based on the size of the defect in local aggressive bone tumors is yet to be described. We evaluated the mechanical behavior of different fixation methods for various defect sizes located in the proximal tibia.

METHODS

Ninety-one sheep tibiae were distributed in five groups. Each study group was further divided into three subgroups, forming 25%, 50%, and 75% metaphyseal defects. The five groups were divided as follows: 1) control group where tibiae remained intact (n = 7); 2) isolated defect created, without filling (n = 21); 3) filling with cement (n = 21); 4) application of two subchondral cortical screws in addition to cement (n = 21); and 5) application of plate-screw fixation in addition to cement (n = 21). A loading test simulating the axial load applied by the distal femur to the tibia plateau was performed. The maximum failure load was compared between groups according to the defect size and fixation method.

FINDINGS

In 25% defects, group 5 had significantly higher failure load than other groups. However, in 50% and 75% defects, additional fixation did not increase the failure load. Also, additional screw fixation did not increase failure load in all defect sizes. There was a significant positive correlation between fracture morphology and defect size, fixation method, and failure load.

INTERPRETATION

Additional plate-screw fixation would increase the stability in defects ≤25%. In defects ≥50%, additional fixation does not increase stability. Screw fixation in addition to cementing does not increase stability in all defect sizes.