Limb equalization using the Ilizarov method has traditionally been accomplished with the use of external fixators. The process, termed “distraction osteogenesis,” is divided into 4 phases. Phase 1: performing a low-energy osteotomy. Phase 2: the latency phase, whereby the bones remain undistracted for a period of time before being pulled apart. The typical latency phase is 7 days. Phase 3: the distraction phase. Ilizarov determined that bone regeneration best occurs with a rate of 1 mm a day, divided into 4 segments of 0.25 mm each.1 Finally, phase 4: the consolidation phase. It is during this time that the immature regenerate bone forms into mature bone allowing for it to regain its structure and function to allow for full weight bearing. Complications associated with external devices2–4 (limb lengthening rails, circular external fixators) have motivated surgeons to evolve with various internal lengthening implants.5–8
PRECICE (Nuvasive Specialized Orthopaedics, Inc, Aliso Viejo, CA) is an implantable magnetic-controlled telescoping internal lengthening nail. Early results are encouraging.9–12 Many orthopaedic trauma surgeons' practice includes managing complex posttraumatic malunions and nonunions. Limb reconstruction implies that the surgeon will address all components of limb alignment. This includes malalignment in the coronal (varus/valgus angulation and medial/lateral translation), sagittal (procurvatum/recurvatum and anterior/posterior translation), and axial (internal/external rotation and limb length discrepancy) planes. The ability to correct the length discrepancy without the use of an external fixator but rather with an internal lengthening nail has allowed more trauma surgeons to adopt its use. Trauma surgeons are trained to be expert in managing diaphyseal femur and tibia fractures with intramedullary nails. In addition, intramedullary nails have been expanded in use for periarticular and metaphyseal fractures. Adjunct techniques to maintain alignment (blocking screws, femoral-distractors, unicortical plating) have been elucidated. However, regardless if one is using a limb-lengthening rail, circular external fixator, or an implantable magnetic lengthening nail, the science of the Ilizarov method must be understood and adhered to.1,13,14 This is analogous to trauma management of complex injuries (eg, calcaneus, Pilon, bicondylar tibial plateau fractures).
This manuscript will discuss some of the practical aspects of limb lengthening surgery using the PRECICE internal lengthening nail. It will discuss preoperative and intraoperative factors that allow for safe and effective execution of the Ilizarov method.
PREOPERATIVE PLANNING—HISTORY AND PHYSICAL EXAMINATION
Managing patients with posttraumatic deformity is complex. Performing a detailed history and physical examination (H & P) is imperative to elucidate all components of the deformity. To be done effectively, posttraumatic reconstruction patients should be viewed as different than most routine trauma clinic patients in the sense that one should be prepared to devote a significant amount of time during the initial clinic visit (45–90 minutes). Practically, one should discuss this with clinic staff, potentially renaming these visits (eg, limb deformity visit). In addition to the routine aspects of history and physical examination, date of injury, mechanism, perioperative complications, and number of surgeries should be sought. Cigarette use, work status, ambulatory status, and what kind of support system should be explored. Allowing patients to describe why they are seeking treatment is effective. Allowing them to discuss their postoperative course often alert you to some of the subtle components (rotation and length) of their deformity. For example, a patient may describe how they reported to their surgical team in the immediate postoperative period that their foot was pointing out and that the therapist thought their limb was short. This also helps determine what radiographs will be required to support the clinical impression.
The clinical examination begins when the patient is appropriately disrobed and placed into shorts so that the limbs may be examined visually. The patient is asked to walk down the hallway of clinic. The surgeon should pay attention to their gait (hip-hiking, Trendelenberg, antalgic), foot progression angle (the position of their foot as they walk) and the direction of their patellae. The other limb (assuming not injured) is examined for reference. Clinical assessment of a limb length discrepancy begins by examining the height of the patient's iliac crests and then trying to level their pelvis with various blocks of known height (Fig. 1). It is also accurate to ask the patient what amount of block height they feel most is comfortable. This is noted and compared with the radiographic analysis. Rotational assessment of the limb is performed by looking at the patient standing with the patellae facing straight forward (Fig. 2A). Femoral rotation is determined by a prone examination of the arc of internal and external rotation. Excessive external rotation in a patient with a femoral malunion would imply that the distal segment is externally rotated. This would also be termed femoral retroversion, femoral retro-torsion or decreased anteversion of the affected side. In the prone position, using a goniometer, the axis of the thigh with the foot is examined and the tight-foot-axis (TFA) is determined (Fig. 2B). A computerized-tomography-rotational profile (axial cuts through the femoral necks, femoral condyles, and ankles) is helpful to corroborate the clinical examination.
PREOPERATIVE PLANNING—RADIOGRAPHIC ANALYSIS
High-quality radiographs are required for accurate assessment of malalignment in the coronal and sagittal planes. In addition, calibrated images that include the entire bone provide preoperative assessment of the intramedullary canal diameter and help choose the osteotomy location (Fig. 3). The smallest nail length (SNL) is calculated according to a formula based the following: The PRECICE implant has a smaller diameter-telescoping segment on the distal aspect that measures 30 mm. Additionally, at least 50 mm of the rod should be stabilizing the bone on the distal end. The smallest nail length = osteotomy location + amount of lengthening +30 mm (small part of rod at distal end) + 50 mm (thick part of rod to stabilize distal segment) (Fig. 3B).
Length assessment is measured off a standing antero-posterior 51″ hip-to-ankle radiograph. The patient should be sent to the x-ray suite with the block that equalizes their limb. The x-ray technicians should be instructed to annotate the film indicating the block height used (Fig. 4A). Joint orientation angles, bone lengths, and limb lengths are measured using the direct and indirect methods (Fig. 4C).15 The indirect measurement records the length difference from the top of the iliac crests, accounting for the foot and pelvic heights (Fig. 4B). Fig. 5 represents x-rays of the tibia that correlate to the same patient in the previous figures. From his standing x-ray, Fig. 4, his medial proximal tibial angle (MPTA) of 86 degrees with an associated mechanical axis deviation (MAD) of 11 mm medial indicated varus alignment. This coronal alignment is taken into consideration when planning for his lengthening. The patient had had an ankle fusion and noted ambulating on the lateral aspect of his foot. Therefore, preoperative planning aimed to move his alignment into relative valgus, by increasing his MPTA to 89 degrees (Figs. 5 and 6).
A detailed step-by-step plan should be outlined in the operating room. The sequences of steps are important. The osteotomy location should be marked according to the preoperative plan (Figs. 3 and 5). A percutaneous incision is made, and the osteotomy site is vented with a large caliber drill-bit (eg, 4.8 mm). This helps reduce the likelihood of fat embolism and deposits bone graft at the osteotomy site to augment regenerate maturation (Figs. 6C, D and 7A). In addition, it is the first step of the low-energy osteotomy for lengthening. The other type of osteotomy used for lengthening is performed with a Gigli saw.16
Large caliber (2.4 mm) Steinman pins are used to mark the rotation of the limb before completing the osteotomy. This helps maintain alignment or can be used to correct it as part of the procedure. The intramedullary canal is prepared to accommodate the appropriate-sized PRECICE nail. We typically ream 2 mm over the planned PRECICE nail diameter (eg, ream to 10.5 mm for 8.5 mm nail; 12.5 mm for 10.7 mm nail; 14.5 mm for 12.5 mm nail). Because it is a noncannulated (solid) nail, the guide-wire must be removed before nail insertion. Typically, the nail is advanced into the proximal segment, the low-energy osteotomy is completed, and the nail advanced gently into the distal segment (Fig. 7B).
The location of the magnet is marked on the patient's skin using fluoroscopy (Fig. 6F). It is important that this is marked either with a nonabsorbable stitch or permanent marker, so that the patient has access to this to place the external remote controller (ERC) for activating the lengthening magnet. Range of motion exercises are started immediately with supervision of a physical therapist. Weight bearing is restricted to 50 lbs (8.5 mm and 10.7 mm PRECICE second-generation nails) and 75 lbs (12.5 mm PRECICE second-generation nails). Calibrated x-rays are obtained every 2 weeks to confirm the amount of distraction. The patient is advanced to full weight bearing once 3 out of 4 cortices are fully formed. The nail is removed typically at 1-year postoperatively.
Distraction osteogenesis using the Ilizarov method is an effective strategy to correct complex posttraumatic deformities. The ability to manage these conditions with an internal lengthening nail has lead to an improved patient's episode of care because most of the problems associated with the Ilizarov method are attributable to the external fixator (pin site infection, soft-tissue irritation, contractures). However, despite the relative ease of use and familiarity of an intramedullary nail, surgeons practicing the Ilizarov method must understand principles of deformity correction (joint orientation angles, limb alignment). Surgeons must be able to accurately quantify all components of limb malalignment and be prepared to manage the complications associated with distraction osteogenesis (poor regenerate, premature consolidation, joint contracture, joint subluxation).
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