Computer-Aided Resection for Bone Tumors Around the Knee
Computer-Aided Resection for Bone Tumors Around the Knee
In all cases the tumors were removed successfully, and postoperative pathological examination confirmed clear surgical margins. All 12 patients underwent reconstruction with allogeneic bone and an endoprosthesis modeled using CAD. There were no surgical complications. Postoperative radiographs showed that the range of tumor resection was completely in accordance with the preoperative design, and showed that the morphological reconstruction of the bone defect area was satisfactory with complete bilateral symmetry. The reconstructed structure was very stable with excellent weight-bearing capacity, which resulted in early recovery of physical activity and daily living. The mean follow-up time of the 12 patients was 26.5 months, and as of this report 10 are alive and well. At the last follow-up, the average ISOLS score was 25.8 (range, 18 to 27), and was excellent in 8 cases and good in 4 cases (Table 2).
Computer Aided 3D Modeling. A 31-year-old female was seen for left knee pain and discomfort for 6 months. Radiography suggested an osteosarcoma in the left distal femur, which perforated laterally and posteriorly and formed a mass adjacent to the cortex (Figure 1A, B). MRI and an open biopsy were performed, and the results were consistent with an osteosarcoma adjacent to the cortex in the left distal femur. The lesion was classified as Enneking stage IIB. A three-stage treatment including preoperative chemotherapy, surgery, and postoperative chemotherapy was designed. The surgical strategy was en bloc tumor resection and limb salvage.
(Enlarge Image)
Figure 1.
Data of radiography. A, B) Anteroposterior and lateral radiographs and C) magnetic resonance imaging studies were consistent with an osteosarcoma of the left distal femur.
First, bilateral lower-extremity CT and subsequent 3D reconstruction were carried out to establish an anatomical model containing the bilateral femurs, tibias, fibulas, and patellae Second, plain and enhanced MRI was performed to verify the range of tumor invasion, and the 3D morphology of the bone tumor was reconstructed (Figure 1C). Both models were combined and analysis and measurements were carried out after registration and alignment. The distance between the proximal end of the tumor located in the medullary cavity of the left distal femur and the femoral intercondylar notch was about 66.4 mm. Based on oncological principles for en bloc tumor resection, normal bone 5 cm in length in the junction zone was to be removed. Because the length of tumor invasion into the medullary cavity was 66.4 mm, a total of 116.4 mm of the distal femur were to be removed (Figure 2A). A CAD designed auxiliary template was created to guide precise tumor resection during surgery (Figure 2B).
(Enlarge Image)
Figure 2.
Measurement and resection of tumor region. A) The distance between the proximal end of the tumor located in the medullary cavity of the left distal femur and the femoral intercondylar notch was about 66.4 mm. The orange-red area represents the 3D morphology of the tumor region. The distance from the proximal end of the tumor (yellow dotted line) to the planed excision point (orange dotted line) was 50 mm. Thus, a total of 116.4 mm of the distal femur was to be removed. B) Auxiliary template to guide tumor resection.
The parameters of the femoral prosthesis were designed according to the morphology of the bone defect and the length of osteotomy. The extramedullary length was 116.4 mm, and the intrameduallary length was 140 mm (Figure 3A). The diameter of the femoral shaft at the site of the osteotomy was 29 mm, the diameter of the medullary cavity at the site of the osteotomy was 17 mm, and the narrowest diameter of the medullary cavity was 15 mm. Based on these parameters, the length of the prosthesis entering the medullary cavity of the residual femur was 146.5 mm. The diameter of the proximal end of the cone-shaped prosthesis was 13 mm, and the diameter of the distal end was 14.5 mm. The extramedullary part of the femoral stem prosthesis was cylinder-shaped. The length was 120.1 mm and the diameter was 20 mm, which was larger than the diameter of the medullary cavity and smaller than the diameter of the femoral shaft at the site of the osteotomy. The CAD designed femoral prosthesis was composed of four parts: femoral condyle (blue), connector (gray), extension rod (blue), fixation rod (yellow) (Figure 3B). A fastening screw was applied between the femoral condyle and the connector. The connector and the extension rod were connected via a taper hole, and an anti-rotation locking plate was also used.
(Enlarge Image)
Figure 3.
Design of the femoral prosthesis. A) Prosthesis parameters. B) CAD model of the femoral prosthesis. C) Template to trim the allogeneic bone to match the surfaces in the distal end of the femoral prosthesis. D) The trimmed allogeneic bone was set in the outer surface of the individualized metal prosthesis to form an individualized femoral prosthesis. E) Stepped contact in the junction zone. F) Allogeneic bone covering the junction at the distal end of the remaining femur and fixed with a band. G) Final 3D model of distal femur reconstruction.
An allogeneic distal femur 15 mm in length was purchased from Auri Biotechnical Company (Taiyun, Shanxi Providence, China). The allogeneic bone was prepared by cobalt 60 irradiation, and was freeze-dried and stored at room temperature until use. The allogeneic femur was cut to an appropriate length using the CAD designed template for trimming the allogeneic femur. Next, the template was used to trim the allogeneic bone such that it matched the surfaces in the distal end of the individualized femoral prosthesis (Figure 3C). The trimmed allogeneic bone was then set in the extramedullary portion of the individualized femoral prosthesis, and bone cement was used for fixation (Figure 3D).
Stepped contact was designed between the allogeneic bone and the residual proximal femur to increase the contact area, reduce stress shielding, and enhance the interface healing (Figure 3E). Moreover, this site was covered with the allogeneic bone, which was fixed by a double wire band (Figure 3F). Conventional prosthetic replacement was carried out in the proximal end of the tibia. A reconstruction model of the distal femur and proximal tibia is shown in Figure 3G.
Surgical Procedure. The distal femur was exposed, and the auxiliary tumor resection template was installed to guide the osteotomy (Figure 4A) and precise tumor resection (Figure 4B). An allogeneic trimming template was installed on the allogeneic bone (Figure 4C), and the allogeneic bone was trimmed to a 3D shape matching the bone defect area (Figure 4D). An allogeneic tendon was passed through both sides of the distal part of the allogeneic bone for collateral ligament reconstruction. The trimmed allogeneic bone was combined with the prosthesis, and bone cement was applied to fix the related parts to form an individualized prosthesis for bone defect repair (Figure 4E).
(Enlarge Image)
Figure 4.
Intraoperative photos. A) Auxiliary template for tumor resection was installed. B) Resected specimen. C) Allogenic bone with template for trimming. D) Trimmed allogeneic bone. E) The trimmed allogeneic bone with prosthesis installed. F) Distal femur implant in place. G) Template for drilling holes in the allogenic bone. H) Allogeneic bone was used to cover the junction zone and fixed with a double wire band.
Conventional osteotomy was performed 10 mm inferior to the articular surface of the right proximal tibia as determined by 3D modeling. The individualized femoral prosthesis was inserted into the medullary cavity of the femur. Conventional prosthetic replacement was carried out on the tibial plateau to reconstruct the bone and joint structure (Figure 4F). A guiding template for hole-drilling was installed (Figure 4G) to guide drilling on the surface of the allogeneic bone. Allogeneic bone fragments were applied to cover the junction between the patient's own bone and the allogeneic bone. A double wire was placed for fixation (Figure 4H). Autologous bone fragments were placed in the holes on the surface of the allogeneic bone to enhance bone regeneration. After placement of a drain and wound closure, the knee joint was fixed with a brace. Postoperative X-ray showed that the reconstruction of the bone and joint was extremely accurate, and the prosthesis shape was well-matched (Figure 5).
(Enlarge Image)
Figure 5.
Postoperative radiographs showed good placement of the femoral and tibial prostheses.
The total operative time was 5 hours, and the intraoperative blood loss was 600 ml. The amount of postoperative drainage was 600 ml on postoperative day one, and decreased to 50 ml on postoperative day four and the drainage tube was removed. Ankle extension and flexion exercises were begun on postoperative day 1, hip flexion and knee flexion exercises were begun on postoperative day 3, and straight leg raises were begun on postoperative day 5. The patient was encouraged to walk with crutches 10 days after surgery. She was able to walk independently by 3 months after surgery and at the 2-year follow-up she was alive and well without evidence of recurrence.
Results
In all cases the tumors were removed successfully, and postoperative pathological examination confirmed clear surgical margins. All 12 patients underwent reconstruction with allogeneic bone and an endoprosthesis modeled using CAD. There were no surgical complications. Postoperative radiographs showed that the range of tumor resection was completely in accordance with the preoperative design, and showed that the morphological reconstruction of the bone defect area was satisfactory with complete bilateral symmetry. The reconstructed structure was very stable with excellent weight-bearing capacity, which resulted in early recovery of physical activity and daily living. The mean follow-up time of the 12 patients was 26.5 months, and as of this report 10 are alive and well. At the last follow-up, the average ISOLS score was 25.8 (range, 18 to 27), and was excellent in 8 cases and good in 4 cases (Table 2).
Representative Case
Computer Aided 3D Modeling. A 31-year-old female was seen for left knee pain and discomfort for 6 months. Radiography suggested an osteosarcoma in the left distal femur, which perforated laterally and posteriorly and formed a mass adjacent to the cortex (Figure 1A, B). MRI and an open biopsy were performed, and the results were consistent with an osteosarcoma adjacent to the cortex in the left distal femur. The lesion was classified as Enneking stage IIB. A three-stage treatment including preoperative chemotherapy, surgery, and postoperative chemotherapy was designed. The surgical strategy was en bloc tumor resection and limb salvage.
(Enlarge Image)
Figure 1.
Data of radiography. A, B) Anteroposterior and lateral radiographs and C) magnetic resonance imaging studies were consistent with an osteosarcoma of the left distal femur.
First, bilateral lower-extremity CT and subsequent 3D reconstruction were carried out to establish an anatomical model containing the bilateral femurs, tibias, fibulas, and patellae Second, plain and enhanced MRI was performed to verify the range of tumor invasion, and the 3D morphology of the bone tumor was reconstructed (Figure 1C). Both models were combined and analysis and measurements were carried out after registration and alignment. The distance between the proximal end of the tumor located in the medullary cavity of the left distal femur and the femoral intercondylar notch was about 66.4 mm. Based on oncological principles for en bloc tumor resection, normal bone 5 cm in length in the junction zone was to be removed. Because the length of tumor invasion into the medullary cavity was 66.4 mm, a total of 116.4 mm of the distal femur were to be removed (Figure 2A). A CAD designed auxiliary template was created to guide precise tumor resection during surgery (Figure 2B).
(Enlarge Image)
Figure 2.
Measurement and resection of tumor region. A) The distance between the proximal end of the tumor located in the medullary cavity of the left distal femur and the femoral intercondylar notch was about 66.4 mm. The orange-red area represents the 3D morphology of the tumor region. The distance from the proximal end of the tumor (yellow dotted line) to the planed excision point (orange dotted line) was 50 mm. Thus, a total of 116.4 mm of the distal femur was to be removed. B) Auxiliary template to guide tumor resection.
The parameters of the femoral prosthesis were designed according to the morphology of the bone defect and the length of osteotomy. The extramedullary length was 116.4 mm, and the intrameduallary length was 140 mm (Figure 3A). The diameter of the femoral shaft at the site of the osteotomy was 29 mm, the diameter of the medullary cavity at the site of the osteotomy was 17 mm, and the narrowest diameter of the medullary cavity was 15 mm. Based on these parameters, the length of the prosthesis entering the medullary cavity of the residual femur was 146.5 mm. The diameter of the proximal end of the cone-shaped prosthesis was 13 mm, and the diameter of the distal end was 14.5 mm. The extramedullary part of the femoral stem prosthesis was cylinder-shaped. The length was 120.1 mm and the diameter was 20 mm, which was larger than the diameter of the medullary cavity and smaller than the diameter of the femoral shaft at the site of the osteotomy. The CAD designed femoral prosthesis was composed of four parts: femoral condyle (blue), connector (gray), extension rod (blue), fixation rod (yellow) (Figure 3B). A fastening screw was applied between the femoral condyle and the connector. The connector and the extension rod were connected via a taper hole, and an anti-rotation locking plate was also used.
(Enlarge Image)
Figure 3.
Design of the femoral prosthesis. A) Prosthesis parameters. B) CAD model of the femoral prosthesis. C) Template to trim the allogeneic bone to match the surfaces in the distal end of the femoral prosthesis. D) The trimmed allogeneic bone was set in the outer surface of the individualized metal prosthesis to form an individualized femoral prosthesis. E) Stepped contact in the junction zone. F) Allogeneic bone covering the junction at the distal end of the remaining femur and fixed with a band. G) Final 3D model of distal femur reconstruction.
An allogeneic distal femur 15 mm in length was purchased from Auri Biotechnical Company (Taiyun, Shanxi Providence, China). The allogeneic bone was prepared by cobalt 60 irradiation, and was freeze-dried and stored at room temperature until use. The allogeneic femur was cut to an appropriate length using the CAD designed template for trimming the allogeneic femur. Next, the template was used to trim the allogeneic bone such that it matched the surfaces in the distal end of the individualized femoral prosthesis (Figure 3C). The trimmed allogeneic bone was then set in the extramedullary portion of the individualized femoral prosthesis, and bone cement was used for fixation (Figure 3D).
Stepped contact was designed between the allogeneic bone and the residual proximal femur to increase the contact area, reduce stress shielding, and enhance the interface healing (Figure 3E). Moreover, this site was covered with the allogeneic bone, which was fixed by a double wire band (Figure 3F). Conventional prosthetic replacement was carried out in the proximal end of the tibia. A reconstruction model of the distal femur and proximal tibia is shown in Figure 3G.
Surgical Procedure. The distal femur was exposed, and the auxiliary tumor resection template was installed to guide the osteotomy (Figure 4A) and precise tumor resection (Figure 4B). An allogeneic trimming template was installed on the allogeneic bone (Figure 4C), and the allogeneic bone was trimmed to a 3D shape matching the bone defect area (Figure 4D). An allogeneic tendon was passed through both sides of the distal part of the allogeneic bone for collateral ligament reconstruction. The trimmed allogeneic bone was combined with the prosthesis, and bone cement was applied to fix the related parts to form an individualized prosthesis for bone defect repair (Figure 4E).
(Enlarge Image)
Figure 4.
Intraoperative photos. A) Auxiliary template for tumor resection was installed. B) Resected specimen. C) Allogenic bone with template for trimming. D) Trimmed allogeneic bone. E) The trimmed allogeneic bone with prosthesis installed. F) Distal femur implant in place. G) Template for drilling holes in the allogenic bone. H) Allogeneic bone was used to cover the junction zone and fixed with a double wire band.
Conventional osteotomy was performed 10 mm inferior to the articular surface of the right proximal tibia as determined by 3D modeling. The individualized femoral prosthesis was inserted into the medullary cavity of the femur. Conventional prosthetic replacement was carried out on the tibial plateau to reconstruct the bone and joint structure (Figure 4F). A guiding template for hole-drilling was installed (Figure 4G) to guide drilling on the surface of the allogeneic bone. Allogeneic bone fragments were applied to cover the junction between the patient's own bone and the allogeneic bone. A double wire was placed for fixation (Figure 4H). Autologous bone fragments were placed in the holes on the surface of the allogeneic bone to enhance bone regeneration. After placement of a drain and wound closure, the knee joint was fixed with a brace. Postoperative X-ray showed that the reconstruction of the bone and joint was extremely accurate, and the prosthesis shape was well-matched (Figure 5).
(Enlarge Image)
Figure 5.
Postoperative radiographs showed good placement of the femoral and tibial prostheses.
The total operative time was 5 hours, and the intraoperative blood loss was 600 ml. The amount of postoperative drainage was 600 ml on postoperative day one, and decreased to 50 ml on postoperative day four and the drainage tube was removed. Ankle extension and flexion exercises were begun on postoperative day 1, hip flexion and knee flexion exercises were begun on postoperative day 3, and straight leg raises were begun on postoperative day 5. The patient was encouraged to walk with crutches 10 days after surgery. She was able to walk independently by 3 months after surgery and at the 2-year follow-up she was alive and well without evidence of recurrence.
Source...