Endoprothetische Rekonstruktion nach interkalarer Resektion

Plate configuration for biological reconstructions of femoral intercalary defect - a finite element evaluation

BACKGROUND AND OBJECTIVE

Biological reconstruction was commonly used for femoral intercalary defect. The initial stability by plate fixation was believed to have an effect on bone union and implant failure. Our study was proposed to explore relationship of plate configuration and initial stability for femoral intercalary reconstruction using allo-/autograft.

METHODS

Femoral intercalary defect models were established with four different plate configurations: (1) Single lateral bridging plate, SLP (2) Lateral bridging plate + Orthogonal adjuvant plate, LP+OAP (3) Lateral bridging plate + Medial adjuvant plate, LP+MAP (4) Lateral bridging plate + Medial bridging plate, LP+MP. A diaphysis defect of 12 cm was simulated, and the removed native femoral bone was used as a structural allograft with the osteotomy gap of 2 mm. Models were analyzed by finite element simulations under an axial compression of 2000N and an axial moment of 10 Nm, respectively.

RESULTS

Axial load: (1) The peak von Mises stress of SLP, LP+OAP, LP+MAP, LP+MP were 993.50 MPa, 335.63 MPa, 240.03 MPa, 281.73 MPa, respectively and LP+MAP was the lowest (p < 0.01); (2) The mean displacement of SLP, LP+OAP, LP+MAP, LP+MP was 0.765, 0.130, 0.121, 0.235 mm, respectively. LP+MAP showed the best stability while SLP had a crash in the medial proximal gap; (3) The LP+MAP configuration had the most uniform stress distribution and the lowest maximum von Mises stress of 79.7 MPa within plates. Axial torsional load: (1) The peak von Mises stress of SLP, LP+OAP, LP+MAP, LP+MP were 431.66Mpa, 120.73 MPa, 72.31 MPa, 109.86 MPa, respectively; (2) The rotation angle of SLP, LP+OAP, LP+MAP, LP+MP was 4.30°, 1.35°, 1.20°, 1.57°, respectively. All of LP+OAP, LP+MAP and LP+MP showed an optimal torsional stability.

CONCLUSIONS

For femoral intercalary reconstruction using allo-/autograft fixed by plates, LP+MAP and LP+MP configurations showed superior stability in terms of axial compression and torsion load by FE simulation. A better stability was believed to be associated with higher union rate and lower hardware failure rate.

[Research progress of cementless intercalary prosthesis stem]

OBJECTIVE

To review the research progress of cementless intercalary prosthesis stem.

METHODS

The literature about the cementless intercalary prosthesis in treatment of bone defects of extremities was reviewed, and the designing and application of prosthesis stem were analyzed.

RESULTS

Cementless intercalary prosthesis has the advantages of good biocompatibility. However, there are also some disadvantages, including the multiple factors affecting the fixation of the prosthesis stem and individual differences in the stability of the prosthesis. The methods to improve the fixation stability of prosthesis stem mainly include the optimization of prosthesis stem shape, addition of auxiliary fixation, and improvement of coating materials on the stem surface as well as porous structure of the stem surface. Among these methods, augment with auxiliary fixation has the most satisfactory effect on improving the stability of prosthesis. However, the deficiency of the method is the increasing risk of the larger incision exposure and surgical trauma.

CONCLUSION

Improving the design and fixation method of the cementless intercalary prosthesis stem can further improve the stability of the prosthesis. Under the premise of avoiding increasing surgical trauma as much as possible, addition of the auxiliary fixation can be a feasible choice to improve the fixation stability of prosthesis.

Assessment of the Viability and Union Feature of Diaphysis Reconstruction Using Pasteurized Tumor Bone and Intramedullary Free Fibular After Tumor Resection

BACKGROUND

Reconstruction using pasteurized tumor bone (PTM) and intramedullary-placed vascularized free fibular (VFG) has the combined advantages of mechanical strength and biological activity. The aims of this study were to investigate scintigraphic viability and radiographic union patterns of composite grafts after surgery, union rates, functional outcomes, and complication rates.

METHODS

Seventeen patients underwent intercalary composite reconstruction using PTM and VFG (12 male, 2 female, mean age: 10.9 y). Retrospective evaluation of radiography and bone scintigraphy was performed. The most common diagnosis was osteosarcoma (12/14, 85.7%). All radiography and bone scintigraphy was reviewed for bone healing and tracer uptake semiquantitatively using the ratio of the reconstructed portion to the contralateral side. Complications and oncological and functional outcomes were recorded.

RESULTS

At a mean follow-up of 33.1 months, primary union was achieved in all 28 host-graft junctions in all 14 patients. The respective mean times to proximal and distal junction bone union were 6.9 and 6.5 months. Metaphyseal junctions healed faster than diaphysis junctions (5.2 vs. 8.0 mo, P=0.02). Free fibular was integrated with surrounding bone after a mean of 10.1 months. The mean tracer uptake ratio was 1.1 after a mean of 4.8 months postoperatively. Half patients (50%) had higher uptake on bone scan than contralateral side. There was no significant correlation between uptake value and bone healing time. Five complications occurred in 4 patients (28.6%), and 1 patient (7.1%) contracted an infection. No fractures or breakages were observed. The mean Musculoskeletal Tumor Society 93 score was 87.6%.

CONCLUSIONS

Reconstruction using PTM combined with VFG is associated with good short-term biological activity as indicated by bone scintigraphy, a high union rate, and an acceptable complication rate. The technique is a useful reconstruction option for large segmental bone defects after tumor resection in lower extremities.

LEVEL OF EVIDENCE

Level IV-therapeutic study.