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An Update on Minimal Incision Osteotomies and Bone Lengthening
Distraction osteogenesis describes de novo bone production between osteotomy surfaces during gradual bone distraction.1,2 In foot and ankle surgery, these principles can apply to pathology such as: brachymetatarsia, malunion, nonunion, limb length discrepancy, and revision surgery.3-5 In this column we present an updated review of the basics of osteotomy techniques and distraction osteogenesis, including terminology and complications, to improve readers’ understanding of bone lengthening.
Important Principles to Keep in Mind
Successful iatrogenic new bone formation requires a precise osteotomy technique. The surgeon must incorporate careful bone separation, create well-aligned bone surfaces, preserve the bone’s precious blood supply, and prevent thermal necrosis.1-5 Ilizarov’s technique includes a core concept in which the surgeon uses a percutaneous corticotomy (transection of bone cortices only, leaving the endosteum intact) instead of an osteotomy (complete division of both cortices and endosteum) to preserve the marrow and periosteum’s blood supply. Corticotomy honors the crucial impact of blood supply to osteogenesis, possibly preserving both periosteal and medullary blood supplies.9,10 The classic corticotomy technique involves transecting approximately two-thirds of the cortex with an osteotome, then inserting the osteotome into the remaining portion and rotating it ninety degrees until the remaining cortex fractures.8,9
Osteotomy site selection primarily relies on deformity location, but one should also consider key pathological and histological concepts. Metaphyseal bone is more vascular, has better stability due to its larger cross-section and easier-to-separate, thinner cortices. However, it typically does not allow as much room for fixation. Osteotomies in metaphyseal bone are typically best for juxta-articular deformities or straight lengthenings. Conversely, due to its differing characteristics, diaphyseal osteotomies best serve only diaphyseal deformities.11-13
Key Osseous Techniques for Bone Lengthening
Corticotomy. The classic Ilizarov corticotomy, as described above, preserves endosteal tissues and vasculature, and results in rapid and reliable bone formation. The surgeon makes a small periosteal incision and creates a tunnel with a periosteal elevator to insert an osteotome. One orients the osteotome vertical or parallel to the long axis of the bone to allow for easy passage under the periosteum, then rotates it 90 degrees to a horizontal position. Repetition of this periosteal elevation and osteotome insertion continues in the medial and lateral cortices until the posterior cortex breaks.
Multiple Drill Hole. In this next technique, a drill or K-wire, depending on the width of the cortex, creates multiple orthogonal holes in the bone at the level of the intended osteotomy. Next, one passes an osteotome horizontally across these tunnels and rotates 90 degrees to the vertical position to break the far cortex.
Gigli Saw. This technique allows for a clean, transverse cut with a thin, braided, serrated metal. First, the surgeon passes a suture subperiosteally across the intended bone(s) by creating a tunnel with a series of straight or curved hemostats under fluoroscopy. This suture then ties to one end of the Gigli saw before pulling it through the created tunnel subperiosteally. This ensures the Gigli saw is deep to any neurovascular structures and therefore avoids any soft tissue or neurovascular injury. The surgeon then places the handles on each end of the Gigli saw and advances it across the intended bone(s) uniformly and symmetrically. This technique is not ideal for diaphyseal bone, as it prolongs bone healing times due to dense cortical bone.8,9,13
Burring. Although a method of osteotomy, burring is not ideal for osteogenesis. The surgeon makes a percutaneous incision and uses live fluoroscopy to divide or remove bone. The burrs fall into either cutting (Shannon burr) or bone resection (wedge burr) types. Despite low speeds and high torque with saline cooling, thermal necrosis is still a concern, as is the amount of bone removed to create the osteotomy. Therefore, burring is not a favored technique in bone lengthening.
Oscillating Saw. In 1994, Frierson and team studied 15 hind limbs of adult dogs, comparing the healing efficacy of three osteotomy techniques in distraction osteogenesis. This study found corticotomy with osteoclasis and multiple drill hole osteotomy had superior regenerate bone formation compared to oscillating saw-based osteotomy. Although all the studied procedure types healed, the authors proposed that increased thermal necrosis produced by the power saw contributed to the slightly slower regenerate bone formation.8 However, thermal necrosis is a concern with any method of osteotomy.
Understanding the Phases of Distraction Osteogenesis
Distraction osteogenesis occurs when a controlled osteotomy, followed by gradual and controlled distraction of the two bone ends, utilizes mechanical stretch of the vascularized bone surfaces to stimulate new bone.9,14 Several temporal phases are responsible for executing this process.
The latency phase lasts 5 to 7 days, starting immediately following the osteotomy. Hematoma formation, inflammatory response, and subsequent differentiation of mesenchymal stem cells (MSCs) into chondrocytes and osteoblasts makes this stage not unlike the acute stage of fracture repair.12 Pro-inflammatory cytokines IL-1 and IL-6 (typically involved in bone repair) upregulate in this phase to promote periosteal callus formation. Expression of tumor necrosis factor and recruitment of MSCs in the latency period supplements the organization and recruitment of inflammatory and mesenchymal cells as the bone segments prepare for distraction. Abbreviating this phase will risk a lack of bone formation and prolonging it can result in premature consolidation.19
Next, the distraction phase is when the periosteal callus resorbs and a fibrous interzone forms, comprised of types 1, 2, 4, and 10 collagen oriented parallel to the distraction force.15 Probably the most distinguishing feature of this phase involves angiogenesis and neoangiogenesis, regulated by expression of vascular endothelial growth factor (VEGF) and angiopoietin signaling pathways.19 New blood vessels grow in loops along and between the collagen fibers, and allow osteoblast recruitment. This fibrous interzone thus acts as a scaffold for new bone formed by intramembranous ossification, directly from osteoblasts.
Conversely, in fracture healing, bone forms primarily by endochondral ossification using a cartilage template. In various animal models, upregulation of expression of numerous factors related to osteogenesis and chondrogenesis drives intramembranous ossification. These include bone morphogenic proteins (BMP-2, BMP-4) and growth factors including TGF-B, FGF, IGF, and PDGF.19
Once achieving the desired length, distraction stops and the consolidation phase begins. During the consolidation phase, osteoid (unmineralized bone matrix) laid down by osteoblasts progressively mineralizes. An increase in the expression of TNF-alpha and the downregulation of BMP expression regulates consolidation.19 TNF-alpha controls the remodeling of the regenerated bone by coordinating the coupled action of osteoclasts and osteoblasts. This is the longest phase, approximately 1-3 months for each centimeter lengthened.9 Methods that disrupt any of the four essential bone blood supplies can decrease osteogenesis.16
Tricortical radiographic consolidation on two orthogonal radiographs mark achievement of bony consolidation. Computed tomography may be necessary to confirm complete osseous healing in foot and ankle cases. Obtaining this endpoint then allows for removal of the external fixation.
What Role Does Rate and Rhythm Play?
Rate and rhythm in distraction osteogenesis significantly impacts the expression of factors involved.18 Further, several experimental studies show improved bone regeneration with continuous versus intermittent distraction osteogenesis.21 One begins distraction at a specific rate and rhythm, typically 1.0 mm a day, divided into four increments. Although this is the classically cited rate, in clinical practice, the rate can vary (0.5 mm/day to 1 mm/day in the foot and ankle) based on multiple factors including: patient age, health, medications, location and type of osteotomy.
Numerous parameters can quantify bone formation quality and speed, with the healing index (HI) being the most widely used. This is the time needed for consolidation to occur per cm of the distracted osteotomy site. Consolidation time (CT) is the time between the end of distraction and complete consolidation or hardware removal. Consolidation time is about twice as long as the distraction time in children, but may be 3 to 4 times longer in adults.16 Thus, it usually amounts to 1 month/cm in children and 2 to 3 months/cm in adults.17
What Complications Should Surgeons Consider?
One should note that nerves and vessels can adapt in length and recover from temporary degenerative changes within 2 months after stopping distraction.9,10 If neurovascular compromise does occur, it most often results from surgical technique (ie pin placement, significant edema, and/or compartment syndrome), but also occurs due to tension during bone lengthening. In addition, bone distraction places increased tension on muscles as the muscle length becomes relatively short compared to that of the bone, ultimately leading to muscle tightness and contractures. Muscles that cross joints more frequently become involved, especially those that cross two joints like the gastrocnemius. Also, a resultant imbalance between muscle strength of antagonists can occur when performing bone lengthening.19 Transfixation of tendons or fascia via external hardware (pins, K-wires) can also inhibit the mechanism of action of certain muscle groups.
In addition to the previously mentioned neurovascular and musculoskeletal complications, one significant drawback of distraction osteogenesis is the prolonged time needed to reach consolidation. This extended period of external fixation may increase complication risks, such as that for pin site infections, pain, discomfort, and psychological concerns.10 Numerous described methods attempt to accelerate the consolidation time, including mechanical loading induced by early weight-bearing.10
Other reported complications include joint stiffness and subluxation, as well as osseous malalignment. During lengthening, there is a tendency for the bone segment in question to gradually veer off its intended course due to muscle forces or instability secondary to an inadequate external fixator construct.2,9,10 Other complications relate to the consolidation rate at the distraction site. Premature consolidation occurs as a direct result of an excessive latency period in which significant callus healing blocks the distraction. In contrast, prolonged or delayed consolidation can occur secondary to patient metabolic, environmental, or technical factors including: poor osteotomy technique, initial diastasis, or rapid distraction.9,10 Pin site tract infections, fracture after external fixator removal, and chronic regional pain syndrome have also been reported.19
Final Comments
Bone lengthening techniques continue to evolve, although Ilizarov’s principles remain the foundation. In the senior author’s experience, although many surgeons cite complications as a barrier to achieving bone lengthening, most complications are not insurmountable. He feels reports of complication rates are inaccurate and potentially inflated, since these studies include minor superficial pin site infection in their metrics. Accordingly, he finds complications that render dysfunction truly rare.
In 1993, Velazquez and colleagues demonstrated a 69 percent complication rate following bone lengthening when performed in the first 6-month period of the surgeon’s experience, but only 35 percent when that experience extended to 18-months.19 Therefore, based on the evidence and the experience of the senior author, distraction osteogenesis is a viable treatment option in foot and ankle surgery when performed by a surgeon with an appropriate level of training and expertise.
Dr. Lamm is the Chief of Foot and Ankle Surgery at St. Mary’s Medical Center and The Palm Beach Children’s Hospital, as well as the Director of the Foot and Ankle Deformity Correction Center and Fellowship at the Paley Orthopedic and Spine Institute in West Palm Beach, FL. He is the Rotation Director for the Podiatric Residency at Harvard Medical School. Dr. Lamm is a Fellow of the American College of Foot and Ankle Surgeons and serves as a Section Editor for the Journal of Foot and Ankle Surgery.
Mr. Lamm is a student at Oxbridge Academy in West Palm Beach, FL.
References
1. Ilizarov GA, Shevtsov VI, Shestakov VA, Kuzmin NV. [Treatment of foot deformities in adults using transosseous osteosynthesis with the Ilizarov frame]. Kurgan: KNIIEKOT Institute; 1987. Russian.
2. Aronson J, Harrison BH, Stewart CL, Harp JH, Jr. The histology of distraction osteogenesis using different external fixators. Clin Orthop Relat Res. 1989;(241):106-116.
3. Lamm BM. Percutaneous distraction osteogenesis for treatment of brachymetatarsia. J Foot Ankle Surg. 2010;49:197-204.
4. Paley D. The correction of complex foot deformities using Ilizarov’s distraction osteotomies. Clin Orthop Relat Res. 1993;293:97-111.
5. Lamm BM, Standard SC, Galley IJ, Herzenberg JE, Paley D. External fixation for the foot and ankle in children. Clin Podiatr Med Surg. 2006;23:137-66
6. Murray JH, Fitch RD. Distraction histiogenesis: principles and indications. J Am Acad Orthop Surg. 1996 Nov;4(6):317-27.
7. Jazrawi LM, Majeska RJ, Klein ML, et al. Bone and cartilage formation in an experimental model of distraction osteogenesis. J Orthop Trauma.1998;12(2):111-6.
8. Frierson M, Ibrahim K, Boles M, et al. Distraction osteogenesis. A comparison of corticotomy techniques. Clin Orthop Rel Res. 1994;(301):19-24.
9. Goldstein RY, Jordan CJ, McLaurin TM, et al. The evolution of the Ilizarov technique; Part 2: The principles of distraction osteosynthesis. Bull Hosp Jt Dis. 2013;71(1):96-103.
10. Paley D. Problems, obstacles, and complications of limb lengthening by the Ilizarov technique. Clin Orthop Relat Res. 1990;250:81-104.
11. Aronson J, Harp JH. Mechanical forces as predictors of healing during tibial lengthening by distraction osteogenesis. Clin Orthop Relat Res. 1994;301:73-79.
12. Aronson J, Good B, Stewart C et al. Preliminary studies of mineralization during distraction osteogenesis. Clin Orthop Relat Res. 1990;250:43-49.
13. Hasler C, Krieg, A. Current concepts of leg lengthening. J Child Orthop.2012;6:89-104.
14. Fischgrund J, Paley D, Suter C. Variables affecting time to bone healing during limb lengthening. Clin Orthop Relat Res. 1994;301:31-37.
15. Vauhkonen M, Peltonen J, Karaharju E, et al. Collagen synthesis and mineralization in the early phase of distraction bone healing. Bone Miner. 1990(10):171-81.
16. Herzenberg JE, Waanders NA. Calculating rate and duration of distraction for deformity correction with the Ilizarov technique. Orthop Clin North Am. 1991;22:601-611.
17. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues. Part 1. The influence of stability of fixation and soft tissuepreservation. Clin Orthop Rel Res. 1989;238:249-281.
18. Schiller JR, Moore DC, Ehrlich MG. Increased lengthening rate decreases expression of fibroblast growth factor 2, platelet-derived growth factor, vascular endothelial growth factor, and CD3 in a rat model of distraction osteogenesis. J Pediatr Orthop. 2007;27:961-968
19. Velazquez RJ, Bell DF, Armstrong PF, et al. Complications of use of the Ilizarov technique in the correction of limb deformities in children. J Bone Joint Surg Am. 1993;75:1148-1156.
20. Alzahrani MM, Anam, EA, et al. The effect of altering the mechanical loading environment on the expression of bone regenerating molecules in cases of distraction osteogenesis. Front Endr. 2014;(5):1-11.
21. Handy RC, Rendon JS, Tabrizian M. Distraction osteogenesis and its challenges in bone regeneration. Bone Regeneration. InTech Open. 2012:185-212. doi:10.5772/32229.
