NOVEL APPROACHES TO RESTORING DEFECTS IN BONE TUMORS Figure 1. Treatment of the patient is a multi-disciplinary effort. It balances the tri-factor of aggressiveness, age and effectiveness of local control (a). In this way it may be determined if the patient will benefit from the proposed treatment option. It should be understood however that above all, the patient’s survival is not to be compromised. In this study conducted by the author reviewing the survival of patients with osteosarcoma over thirty years it is found that the survival of patients with osteosarcoma in the National University of Singapore was superior to the national average and that this in turn was superior to the national US average (statistically significant). Hence we may conclude that the treatment modalities offered to our patients in Singapore have not compromised their survival over the last 30 years.
Figure 2. It is rarely if ever necessary to perform an amputation in this era of modern medicine for bone tumors unless the tumor has fungated through the skin. This patient who had a neglected bone tumor and had sought a second opinion from a neighboring country was offered an amputation above the knee (a).We agreed that an amputation was necessary but offered the option of replanting the amputated segment using microsurgical techniques (b). We were able to re-anastamose all his vessels and his nerves which were lost in the amputated segment (a so called amputation replantation procedure). The huge advantage of this procedure is that the ankle now functions as a knee and can take a below knee prosthesis which is many times superior to an above knee amputation prosthesis (c). The variants of this procedure and how it compares to an above knee amputation (d) illustrate how this procedure may be superior over an above knee amputation. The prospect of using bone donated from a deceased individual to reconstruct defects offers a potentially durable life-time solution. There are problems however. They fracture or do not incorporate in one in five patients and get infected in one in ten patients. Immunocompatibility is now presently not required for bone transplants. Contrary to popular belief, they do not “come alive” within the body but rather stay as intercalary replacements. Availability is an issue and often bone needs to be imported from foreign countries. NUS presently has a working relationship with the Perth Bone bank who have kindly consented to providing bone for tumor reconstructions for a modest handling fee (Figure 3).
![]() Figure 3. This 4 year-old child had a Ewing’s sarcoma of the tibia (a). It had was about 15 mm from the growth plate (b). In view of her age, she was offered an amputation by her referring physician. Nevertheless we were able to offer her a limb salvage procedure after resecting the tumor (c). The only thing that would fit the dimensions of this toddler was the humerus of an adult (d). By doing an intercalary replacement, the author was able to save the growth plate (e). Surgery was uneventful and the epiphyseal screws were removed to allow growth (f). Six months later (g) the growth in the epiphysis was appreciable (arrowed).
Figure 4. Reusing the tumor bearing bone is an excellent solution to the challenges faced by tumors around the pelvis – in particular the hip joint. This 9 year-old boy had a Ewing’s sarcoma of the acetabulum (a). Resecting tumor (b) would result in an unstable joint and some surgeons would fuse the hip resulting in problems for the child sitting and causing long term back problems. The author elected to preserve the joint by hyper-freezing it in liquid nitrogen (c) and replanting it. This gives a perfect match for size and anatomy. Unfortunately the process of freezing, while it still preserves the growth factors kills off the cells both normal and malignant. Hence rods and cement are used to re-enforce the structure. Two years later the patient walks with a limp but is able to perform functionally well. There has been no signs of recurrence. While perhaps the most visible of the options available, megaendoprostheses use have many attendant problems, chief amongst which are size discrepancies and poor longevity. Nevertheless, next to amputations, they allow the fastest return to chemotherapy. Their high cost is often a consideration as well. They are classically indicated in the 14 to 16 year-old osteosarcoma patient who has reached the end of their growth potential. They have been used in growing children where growing mechanisms are incorporated. This involves multiple surgeries about 3 to 4 times per year to lengthen the limb or an electromagnet to effect lengthening without further surgery. While inviting in theory, often the desired length is not achievable and most implants will fail for a number of reasons by the end of the lengthening procedure whether from failures in fixation, failures in lengthening mechanisms or infections due to multiple surgeries. Their use has essentially become confined to a few dedicated research centers around the world. They are three times as expensive as the non-lengthening megaendoprosthesis described earlier. They are not the preferred method of bone lengthening in NUS (Figure 5). ![]() Figure 5. The author has extensive experience in using endoprosthetics in the reconstruction of bone tumors. These work very well in teens and adults. This 42 year-old male had a sarcoma of the left distal femur (a). Following the biopsy the tumor was filled with cement and metallic rods to prevent any fracture while chemotherapy was initiated. After 2 months the entire segment was resected and a megaendoprosthesis was used to reconstruct the defect. Another case shows the segments of bone which the megaendoprosthesis attempts to replicate (d). While a convenient approach, in this study by the author financed by the National University of Singapore, it was found that physical satisfaction was only superior if the patients’ own joint can be preserved (e). Hence the main thrust in surgical approach at the University has been to preserve the joint where possible unless as in this case the joint cannot be preserved without endangering local control.
Minimally invasive options
Minimally invasive approaches to aggressive non-malignant and metastatic lesions include cryosurgical and radio-frequency ablation. NUS has invested in cryosurgical probes that allow the delivery of freezing techniques into a remote area through percutaneous technique. The big advantage of probe delivery techniques are that they are easier to control and have fewer side effects of skin burns and nitrogen gas embolisation compared to older techniques using liquid nitrogen pour techniques (Figure 6).
![]() Figure 6. Professor Nathan led an initiative presently into the third phase of implementing cryosurgical ablation of tumors. The first phase involved ablation using liquid nitrogen pouring techniques. The second phase involved open procedures using the cryoprobe system shown (a). Presently we are developing minimally invasive technology using CT fluoroscopy to target the tumors in situ percutaneously (b). Each probe has a known and reproducible zone of ablation (c) which freezes down to -200 degrees Celsius. The process is monitored using thermocouples. It allows the percutaneous freezing of tumors without requiring large incisions (d). Computer assisted technologies Under this category are a group of technologies including computer navigation and robotic technology. This is covered elsewhere on our site. The primary problem with these technologies is the cost of the machines which ultimately becomes borne by an already stressed healthcare industry. In this space 3D cutting jigs have become available. Here we make use of high resolution scanners to scan the area of interest. This is then used to print in three-dimensions not only the cutting jigs but the surgical plans as well. Our centre is a leader in this field regionally and has come to the conclusion that it is the best compromise of cost and efficacy for highly specialized resection situations (Figure 7 and 8). We present a mini-lecture about 3D printing in orthopedic applications here. Figure 8. This is the video of a highly specialized resection and reconstruction of a bone tumor using 3D printing technology. Further information about this is available here. Conclusion
Musculoskeletal oncology is a highly specialized branch of orthopedic surgery practiced by a very select few in Singapore. Some are well published in the field and have been involved in the evolution of the specialty since its inception some 30 years ago with Singapore being the host of the 6th International Symposium of Limb Salvage Surgeons in 1993. Many techniques of limb salvage have come and gone in that time but the more resilient and proven techniques have stood the test of time. The challenges at hand may now be met by individualized approaches which in the right hands can yield remarkable results. |