|Year : 2016 | Volume
| Issue : 1 | Page : 3-5
What happened to the regenerate? What would Ilizarov say?
Stuart A Green
Department of Orthopaedic Surgery, University of California, Irvine, California, USA
|Date of Web Publication||17-May-2016|
Stuart A Green
Department of Orthopaedic Surgery, University of California, Irvine, California
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Green SA. What happened to the regenerate? What would Ilizarov say?. J Limb Lengthen Reconstr 2016;2:3-5
In 1951, Prof. G. A. Ilizarov unlocked from within bone a previously hidden capacity to form new osseous tissue with the appropriate conditions of osteotomy, delay to allow preliminary healing, and distraction with an appropriate rate and rhythm in the mechanically stable environment. With the help of colleagues in Kurgan, the USSR, Prof. Ilizarov developed an entire system of orthopedics and traumatology based on the use of his tensioned wire circular external skeletal fixator.
For two and a half decades, the method of Ilizarov was unknown to non-Soviet and non-Eastern Bloc surgeons. When Western surgeons did finally learn about this technology in the 1980s, it was a mature system of therapeutics, supported by extensive basic science research on what Ilizarov called "the tension-stress effect of distraction osteogenesis." With this methodology, surgeons could cure a remarkable variety of congenital, developmental, and acquired musculoskeletal conditions that had been previously considered untreatable.
Prof. Ilizarov taught that his apparatus, which employed tensioned transosseous wires secured at multiple levels to each bone fragment, was essential for the successful application of his method. He explained that the exterior frame was rigid in all planes, including rotation, side bending, axial compression, and distraction. The tension wires, however, acted like a trampoline, permitting axial dynamization with weight-bearing and other functional activities. This movement stimulated the formation of regenerate new bone in the particular configuration characteristic of the Ilizarov method.
The newly-formed bone in a widening distraction has a distinctive appearance: The regenerate bone as the same width of the bone from which it is created. The regenerate bone has longitudinal striations, with a distinct zigzag interzone, as it is called, in the middle of the regenerate bone where new osseous tissue is forming, sort of like a growth plate. There are zones of both radiolucency and increased density at the ends of the regenerate region, adjacent to the normal bone.
This regenerate starts out within a month of distraction as hazy calcifications that coalesce into the structure described above.
Visitors to Kurgan were amazed by the consistency and predictability of regenerate bone formation.
As non-Soviet surgeons began to use the methods of Ilizarov, they started to make certain modifications in both the clinical and technical aspects of treatment. In some cases, these modifications were allegedly to improve patient comfort, whereas in other situations, the changes were designed to ease fixator application or simplify the admittedly complicated steps necessary to correct multiplanar deformities.
It is no surprise, therefore, that surgeons using the method of Ilizarov with its modifications began to experience degradation in the quality of regenerate new bone formed in the widening distraction [Figure 1].
Here are some of the modifications that have degraded the regenerate.
First of all, the osteotomy, which Ilizarov calls a corticotomy, is properly performed, not with an osteotome, but with a thin-bladed chisel. In this way, the bone is not pried apart during osteoclasis, but instead breaks in the transverse manner without a large spike on the opposite cortex.
More importantly, in Kurgan, surgeons are careful to keep the blade of the chisel entirely within the cortex of the bone to avoid damage to the endosteal blood supply and particularly to the nutrient artery and its branches inside the marrow canal. They feel that this blood supply is essential to forming a proper regenerate.
Western surgeons, unable to prevent the spiky cortex on the opposite side of the bone, developed a number of strategies to prevent this from happening. Among these was the use of a Gigli saw to perform a purely transverse osteotomy using a minimally invasive surgical technique. Obviously, such a saw cuts directly across the endosteal blood supply.
Another similar strategy employs the use of multiple drill holes in the cortex prior to osteotomy. A spinning drillbit crossing the marrow wraps up blood vessels and other marrow elements, thereby degrading the medullary blood supply. The situation is exacerbated when an osteotome connects the drilled holes directly across the medullary canal.
The final insult to endosteal circulation involves the use of medullary implants, specifically, intramedullary (IM) nails inserted after reaming out the endosteal tissue. Fortunately, IM implants stabilize the bone, allowing early removal of external fixation, or, in the case of self-lengthening devices, the complete elimination of external fixation altogether. This step allows virtually unlimited time for new bone to form in the distraction gap, clearly the saving feature of such modifications.
Once the osteotomy is complete, numerous other modifications in the Ilizarov method have come to dominate non-Soviet applications of the professor's strategies. First of all, stiff half-pins have replaced tension wires in many locations, particularly when securing the apparatus to cortical bone. This alters the mechanical environment by turning the trampoline effect into a cantilever effect, transferring cyclic axial loads into bending and shearing loads.
Another important change in the technical arena involves the introduction of new components and entire frame configurations that are different, indeed, from those designed by Prof. Ilizarov et al. For instance, monolateral external fixators offer a completely different mechanical environment from that within circular rings.
The so-called Italian clickers (ratcheted distraction rods) have a little jiggle in the clicking mechanism. Likewise, the Taylor Spatial Frame is known to have some play as a consequence of its design features that causes as much as a millimeter of nonaxial movement in the distraction gap with each step a patient takes.
Perhaps, the most significant modification in what was Ilizarov's method has become the hallmark of Western care, driven by economic considerations that did not impact treatment in the communist era within the Soviet Union.
Specifically, physical therapy in Kurgan was an all-day, every-day ordeal for the patients. They would spend the 6-8 h a day in supervised physical activity, play therapy, and ambulation, but with a single cane. This, more than anything else, appears to have stimulated proper maturation of the regenerate. Moreover, to achieve such intensive therapy, a relatively painless application of the device was essential. Skin tension, the principal source of pain during the application of an external fixator, was never permitted to exist by the time of the frame configuration was finalized in the operating room.
Likewise, pin-site inflammation is another source of great discomfort for patients. Attention to infection control (with proper wrappings) was therefore another hallmark of Soviet-era Ilizarov skincare.
It is obvious from the foregoing discourse that many modifications have been introduced into what should properly be called "The Original Method of Ilizarov." In some cases, the obvious value of certain modifications suggests that they will never go away. For example, the Taylor Spatial Frame and other forthcoming hexapod constructs ease deformity correction and simplify the day-to-day treatment program.
More significantly, entirely internal self-lengthening implants will revolutionize limb lengthening and deformity correction. Patients who have had one limb treated with external fixation and the other with a fully implantable device say that they would never again permit an external fixator to be used on their body when an internal device could be used instead.
With these observations in mind, we should at least try to retain those elements of the Ilizarov method that stimulate a proper regenerate in the widening distraction gap. Since the use of internal lengthening devices destroys endosteal blood supply, preservation of the nutrient artery and its branches becomes impossible. Therefore, the actual technique of the osteotomy is not particularly important with IM lengthening.
Hence, we should focus attention on postoperative measures, particularly physical therapy, exercises, and management of the regenerate zone through close follow-up and adjustments in the rate and rhythm of distraction on a weekly or biweekly basis. We should not allow insurance companies to limit physical therapy or other measures needed to promote a healthy, radiographically impressive regenerate.
Unless we do these things, we will not be true disciples of Prof. Gavriil Ilizarov.