Friday, August 10, 2018
Although distraction osteogenesis is commonly employed in regular orthopedic surgery, its use in cancer patients is currently limited. But research shows that these durable reconstructions can provide superior opportunities for better long-term limb function and growth compared to the artificial or cadaveric alternatives used in oncology.
In the past, surgeons have been reluctant to perform distraction osteogenesis in bone cancers due to a lack of knowledge about the technique, concerns about infection risk, potential tumor activation, and the uncertainty of the effect of systemic chemotherapy on regenerated bone tissue.
With regards to tumor cell activation, there are a few anecdotal cases cited in the literature, but no causal relationship has been established. (1)
At Memorial Sloan Kettering Cancer Center, the technique is performed regularly and successfully to restore live bone stock and eliminate limb-length discrepancies in many pediatric sarcoma patients.
Pediatric Sarcoma: Improved Survival and Improving Surgical Techniques
There are several types of pediatric sarcoma, including adamantinoma, chondrosarcoma, Ewing sarcoma, and osteosarcoma. In children and teenagers, osteosarcoma (56 percent) and Ewing sarcoma (34 percent) are the two most common types. (1) With osteosarcoma, for example, the disease usually develops in patients after the age of ten and is most common during the teenage growth spurt.
Modern chemotherapy advances mean that a cure can be achieved in up to 70 percent of patients with a localized sarcoma. (1) As a result, more patients, especially pediatric patients with many years of life ahead, need durable reconstructions that can last a lifetime.
The mainstay of surgical reconstruction for most of these patients has traditionally included prosthetic implants, vascularized fibulas, a massive bone allograft, or the combination of an allograft and an implant. However, the failure rates with those methods are very high, depending on the technique used, and they do not address the limb-length discrepancy that develops as pediatric patients grow. (1)Back to top
Distraction Osteogenesis: How It Works
To perform distraction osteogenesis after lesion resection, we cut the bone carefully, tricking the bone into thinking it needs to heal the fracture; we then use an internal or external fixator device to hold the two ends of the bone together. The patient or caregiver makes small adjustments to the device every day to encourage new bone growth, at the rate of about a millimeter per day, closing the gap over a period of about four to six months.
Adequate resection with negative margins is the most critical principle in oncologic surgery: The resection always dictates the reconstructive option, not vice versa. We can incorporate the distraction osteogenesis technique with several methods of reconstruction: single-level or multilevel bone transport, acute compression with gradual lengthening, gradual shortening with gradual lengthening, physeal distraction, lengthening over a nail, and lengthening and then nailing or plating. (2)
The choice between an external or internal fixator device depends on several factors, including the size of the area to be regenerated, whether additional stabilization is required to maintain proper alignment, and whether additional lengthening will be needed to address limb-length discrepancy. Today, there are more external fixator options available, including monolateral and multiplanar systems.Back to top
Benefits of Living Bone Reconstruction
In a study of functional outcomes in 22 patients over ten years, researchers in Japan found that epiphyseal preservation and reconstruction by bone distraction restored functionality to natural limbs and provided excellent long-term outcomes. The study examined outcomes for eight men and 14 women with a mean age of 25.3 years who had a range of sarcomas: seven osteosarcomas, two osteofibrous dysplasias, one Ewing sarcoma, five low-grade osteosarcomas, two adamantinomas, and five giant cell tumors. Eight people received chemotherapy during bone distraction, 17 underwent bone transport, and five received shortening followed by distraction. The mean distraction length was 8.1 centimeters, and patients underwent external fixation for a mean period of 301 days. At 202 months, the average Musculoskeletal Tumor Society score, which is used to measure functional outcome, was 91.5 percent. Fourteen patients returned to playing sports with no difficulty. (3)Back to top
Limitations and Considerations
In the most extensive small study to date on pin tract infection in immunocompromised patients, researchers reported infection rates of 4.9 percent around wires and 4.6 percent around pins in 14 of 28 patients who had undergone distraction osteogenesis or vascularized fibular grafting after tumor resection. (4) These rates were comparable to patients undergoing bone-lengthening procedures for nononcologic conditions.
Chemotherapy likely impedes the ability of osteoblasts to cope with increased functional demand, slowing callus formation in distraction osteogenesis. (1)However, two analyses comparing patients who underwent distraction osteogenesis with and without concomitant chemotherapy did not demonstrate any difference in bone healing between the groups. (5), (6)
Reconstruction with distraction osteogenesis requires a prolonged treatment time, diligent care, and in cases where an external fixator is used, an added psychological, hygiene, and daily activity burden for patients and caregivers. As we develop customized treatment plans for each patient, we take all of these considerations into account when counseling patients and caregivers on their best options and treatment alternatives.
Patients benefit from improved long-term capacities to heal potential future fractures, build bone in response to increased loads, reverse disuse osteopenia, and fight infection better than with traditional forms of reconstruction. (1)
At MSK, we have the largest pediatric sarcoma program in the world and care for approximately 200 young patients with sarcomas each year. Our multidisciplinary experts have extensive experience in diagnosing and treating pediatric patients with all types of sarcomas, including rare sarcomas, such as desmoplastic small round cell tumors, Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma. We are dedicated to helping our patients achieve the best possible long-term outcomes.
Recently, we published a review paper on the use of distraction osteogenesis, sharing several cases from our experience at Memorial Sloan Kettering Cancer Center.
Consider this case of an 11-year-old female patient diagnosed with high-grade osteosarcoma. She had previously undergone wide resection with a Campanna technique reconstruction — an approach that uses a cadaveric allograft and intramedullary free fibular transfer — with a good initial result.
Three and a half years postsurgery, the reconstruction failed. She presented with a fractured allograft and a 13-centimeter leg-length discrepancy. We explanted the failed construction, placed an external fixator, performed a double osteotomy, and embedded an intramedullary wire to ensure that fragments of new bone growth would transport along the desired axis. Over a period of about six months, parallel double-level bone transport filled the defect, and additional lengthening addressed the limb-length discrepancy. Two years after the removal of the failed Campanna reconstruction, the patient had symmetric extremities and was fully weight bearing. (7)