The pediatric patient with a malignant bone tumor of the extremity is a challenging clinical scenario. Advances in adjuvant therapy have made limb-salvage procedures a realistic option without compromising survival or local recurrence. Surgical options to be discussed with the family include amputation, rotationplasty and prosthetic reconstruction. The advent of the expandable prosthesis has gained significant interest due to the appeal of limb salvage with a good cosmetic result and potential for equal limb length at skeletal maturity. Devices now exist which allow for non-invasive lengthening on an outpatient basis. Review of the literature demonstrates that this procedure has generally good patient reported outcomes but has a high complication rate, with aseptic loosening being the most common mode of failure. Further improvement in implant design and biomaterials may decrease these complications and work in these areas is underway. Currently, patients choosing this option should be counseled regarding the likelihood of future surgeries to manage the expected complications.
An exciting new development in this field has been the creation of a“bioexpandable”endoprosthesis to address the issue of the increasing leverage between endoprosthetic/bone segments with subsequent lengthening., Baumgart and colleagues have reported on the MUTARS BioXpand device (Implantcast, Buxtehude) which employs the technique of callous distraction to lengthen the host bone segment. This device accomplishes this by use of the fully implantable motorized nail, the“Fitbone,”rather than external fixation devices as classically described by Ilizarov. There are, as of yet, no long term studies that we are aware of evaluating the outcomes and complications of this particular procedure.
I entered the Navy out of college in January 1965. My boot training was in North Chicago, and my "A" school was also based there. I completed Hospital Corpsman school in August 1965. My first assignment was Kittery, Maine Naval Shipyard, at the Naval hospital. I made E-4 (or Petty Officer 3rd Class) at that time. In May 1966, I got my invitation to join the Fleet Marines down in Camp LeJeune, NC, for some training with the "Mean Green Machine". I was assigned to Field Medical School and then, upon completion, the 2nd Marine Division, India Company. I then attended and completed "Jungle Warfare School" in Panama. I changed Battalions and thought I was going to the Med (Mediterranean for NATO training), instead I went back to Panama for more Jungle Warfare Training with H&S Company, Battalion Aid Station etc. In November of 1967, I got orders to report to California and the 3rd Marine Division for assignment, Southeast Asia (Vietnam). After two weeks of classes and shots etc. in Okinawa, I was airlifted to DaNang, Republic of South Vietnam. I don't recall how long I spent there before I was given an opportunity to "volunteer" for duty with the 3rd Recon Battalion moving up to Phu Bai. I volunteered because I believed I was as prepared as anyone in my group just entering the country for duty. When I arrived Phu Bai, I was assigned to Alpha Company and with that company and the advanced party, we moved up to our permanent base camp in Quang Tri. Quang Tri is in what was called the "Iron Triangle". Within this geographical area is 3rd Recon's area of responsibility: Khe Sahn, Camp Lo, Con Tien, Dong Ha, Camp Carrol, the DMZ, and some places I don't remember. Some outstanding geological formations are: The Rock Pile, The Razor Back, Dong Ho Mountain, Ashau Valley, etc. While on one of my first Patrols out of Phu Bai, my team saw a massive troop movement through our area of responsibility just a few hours before a holiday called "TET68"! That's right, my recon team of seven, heavily armed and dangerous, reported a violation of the TET holiday truce. We requested a legitimate fire mission on the offending masses and we were refused. That moment in time changed my whole perspective on how I was going to participate in this war. Sometime later in my tour of duty, my team of five reconners were ambushed along a frontier and we took out three North Vietnamese soldiers, one more limped away. We were evenly matched and thus, three of their number escaped with their lives, two were down in the field of fire. That was when I made my second resolution to survive and rotate Stateside in my turn. The rest of my tour of duty was relatively uneventful. I was to work exclusively the Battalion Aid Station as the "senior" corpsman until I was demoted by someone more senior to me with no bush experience. That was fine, as I was a "short timer" and due to rotate in a matter of weeks. On a pleasant day in December 1968, I was driven to a steel runway and "Air America" came down with a DC-10 and flew several of us down to DaNang for a date with a C-130 to Okinawa. I spent two weeks or so there for counsel and records collection and the re-issue of clothing, stores etc. Then, I was on a Western Airlines Jet to El Torro, California. There was no fanfare when we touched down. There were Marine Corps and Navy buses to pick up the passengers for distribution to the various discharge or duty stations in the immediate vicinity. I was to report to Long Beach Naval Hospital for discharge planning and a thorough physical. I obtained a 48-hour pass and took a bus to Riverside, California to visit my sister and brother in-law, who was a Major in the Air Force at March AFB. While waiting for the bus, a man, not much older than myself, came over to me and put his hand out and said, "Thank you," while shaking my hand. I was stunned because I heard some bad stuff about how servicemen were treated. When my brother in-law took me to the officers' club on base, he called attention to me from everyone within hearing: "This in my brother in- law, he has just returned from Vietnam serving with the Marine's ..." I was given a standing ovation from everyone in the room. I was embarrassed, somewhat, and then I got choked up. I was offered more drinks than I could consume. I departed California two weeks later to fly to Rochester, MN and visit with my parents and siblings. Then I flew in to a small burg called, Exeter, NH, where my bride of one year was waiting with our four-month old daughter. As Robert Frost once wrote: "I have miles to go, miles to go before I sleep ..."
The only study, to our knowledge, examining the outcome of the Repiphysis prosthesis was reported by Gitelis et al. The fourteen patients in this series were reported at greater than two years follow-up. There was a 100% limb-salvage rate in this series, although there were five necessary revision surgeries all related to failure or fracture of the implanted components. Patients had an average MSTS score of 83.5% at the time of most recent follow-up.
The Phenix (Phenix-medical, Paris, France) endoprosthesis was implanted in 15 patients as reported by Neel and colleagues. They noted patients had good early results with average Musculoskeletal Tumor Society (MSTS) scores of 90% at an average of 18 months. Of the three patients at skeletal maturity at the time of the report all had leg lengths within one centimeter. This is a custom manufactured device that utilizes stored energy in the form of a compressed spring for future lengthening. The energy is then selectively released in a closed fashion by subjecting the limb to an electromagnetic field which heats the polymer casing allowing for controlled expansion. The advantage of this technology is that lengthening is performed closed and, except for unusual circumstances, without general anesthesia. The Phenix is now manufactured as Repiphysis (Wright Medical Technology, Arlington, TN).
When considering implanting an expanding endoprosthesis it is important to calculate estimated remaining growth. A child at or near skeletal maturity does not need an expandable device. Depending on their remaining growth the surgeon can consider an acute lengthening with implantation of a conventional endoprosthesis with or without a contralateral epiphysiodesis. Calculaion of remaining growth is instructive when counseling the patient and family members on surgical options and approximate number of lengthening procedures required.
There are several manufacturers worldwide that produce expandable prostheses, they are mentioned in the following sections. In the United States, the only manufacturer that we are aware of is Wright Medical (Arlington, TN) who produces the Repiphysis system. We have had experience with this device at our institution.
Expandable components offer the advantage of either minimally invasive or non-invasive expansion procedures.,,,,,, The disadvantages of these devices, however, are the potential for failure of the expansion mechanism and failure of the prosthesis at maximal lengthening.,, The modular component may be more desirable in a patient where lengthening requirements will be minimal, whereas the expandable component may be desirable in a patient who will require multiple lengthening procedures.
With use of the expandable prosthesis, pre-operative planning is paramount. Magnetic resonance imaging (MRI) can best define the extent of the tumor (Figure I). These should be done both prior to, and following neoadjuvant chemotherapy sessions. Planned resection and imaging data must be communicated to the manufacturer as these devices are custom made for each patient. Further more, careful examination of imaging studies will advise as to the proximity of the tumor to neurovascular structures. A prerequisite for limb salvage is the ability to maintain the neurovascular bundle without compromising local control of the malignancy. In addition, careful study of the tumor can advise toward the surgical approach made.
Along with improved treatment regiments, in recent years there has been an increasing focus on improving quality of life and function for the larger number of patients surviving their disease. Results of comparative studies differ with regard to whether amputation, rotationplasty or reconstruction offers the superior outcome.,, However, with improved device manufacturing and biomaterials there is an ever-gaining interest in limb-salvage by endoprosthetic reconstruction. In addition, there is a belief that limb salvage by prosthetic may offer psychological advantage due to an essentially normal outward appearing limb. Although it has been noted that most patients who survive this life-threatening disease adjust well to any necessary surgical treatment.
The locking mechanism of the prosthesis is located under fluoroscopy and the skin is marked overlying this. The electromagnetic coil is then applied around the leg at the location of the skin marking. The device is activated in 20 second intervals to achieve the desired lengthening. Images are examined after each lengthening interval.