Tibial Lengthening with a Motorized Intramedullary Lengthening Nail.
Academic Article
Overview
abstract
BACKGROUND: Tibial lengthening with use of a motorized intramedullary lengthening nail (MILN) provides precise deformity correction and distraction osteogenesis without requiring external fixation1. A MILN can be utilized for many etiologies requiring lengthening, such as congenital (e.g., short stature, limb deficiency) or acquired (e.g., post-infectious, traumatic)2. The present video article describes the surgical technique for MILN use in the tibia in a skeletally mature patient with use of the Precice System (Globus Medical). DESCRIPTION: The preoperative patient evaluation starts with a history to understand the primary reason(s) that the patient seeks lengthening, to identify potential care challenges (such as dormant infection for patients with a post-infectious etiology or joint instability for patients with limb deficiency). The physical examination should evaluate for joint contracture or instability, spasticity, prior surgery compromising the surgical approach, and patient psychological or physical capacity to comply with postoperative weight-bearing and lengthening instructions. Preoperative imaging includes calibrated orthogonal radiographs of the operative tibia to ensure suitable anatomy and bilateral hip-to-ankle radiographs, with blocks to level the pelvis as needed, to determine any limb-length discrepancy (LLD) or alignment deformity3,4. A gastrocnemius-soleus complex release may be considered; otherwise, the surgical procedure begins with exposure of the tibia and predrilling of the osteotomy site. The tibial canal is entered in either a suprapatellar or infrapatellar (as shown in this video) fashion and sequentially reamed over a centrally placed guidewire. Proximal and distal rotation marker pins are placed posterior to the expected path of the MILN5. Blocking screws can be placed to prevent or correct deformity6. Prophylactic fasciotomy may be appropriate when performing acute deformity correction7. Osteotomies of the fibula and tibia are performed with use of an osteotome. The nail is inserted and locked in position. Proximal and distal tibiofibular fixation minimizes undesired migration of the fibular segments8. Lengthening generally starts 7 days after surgery, using 4 lengthenings, totalling a maximum of 0.8 mm, per day. ALTERNATIVES: Some LLD cases are suitably treated without surgical intervention9. Alternative lengthening techniques10 include monolateral external fixators11 and circular fixators, with or without computer guidance12 and with or without subsequent internal fixation13,14, and other brands of MILN15. Hexapod fixators facilitate the most comprehensive deformity correction16, although indications are expanding for deformity correction via nailing17. Patients may feel that internal options are more convenient than external ones18-20. Few patients desire treatment of LLD by shortening the longer extremity21. RATIONALE: LLD and associated deformities can alter natural gait patterns and lead to abnormal joint forces, which may cause a painful and altered gait. Although there are broad opinions regarding the minimum LLD indicating surgery, distraction osteogenesis is a well-established and proven mechanism for bone lengthening. Once lengthening has been indicated, many factors influence the decision to use external or internal fixation, such as the magnitude of lengthening, need and ability to correct other deformity, implant access, and non-medical patient factors. Regardless of the implant, tibial osteotomy should be performed utilizing safe planning, techniques, and medical adjuncts7. EXPECTED OUTCOMES: When an MILN procedure is performed safely, patients can expect up to 8 cm of lengthening with a minimal risk of implant problems, fracture, infection, or other adverse events7,22. Patients must adhere to weight-bearing limitations and perform stretching exercises to avoid joint stiffness. Most patients report high satisfaction after lengthening23. IMPORTANT TIPS: Establish the LLD before surgery, then rely on the machine to determine the length achieved; do not second-guess the machine during lengthening.Correct or prevent rotational, coronal, and sagittal deformity at the time of the MILN insertion surgery.Prioritize safety (i.e., with a percutaneous technique, fasciotomy, and tranexamic acid) to optimize outcomes (i.e., avoidance of complications and achievement of the desired length).Ensure patient compliance with weight-bearing limitations and stretching exercises.Limit weight-bearing until at least 3 cortices have full bridging.MILN removal is recommended after full union is achieved, typically approximately 1 year postoperatively. ACRONYMS AND ABBREVIATIONS: LLD = limb-length discrepancyMILN = motorized internal lengthening nailPT = physical therapyIM = intramedullary.
