Study Guide

Limb Lengthening Techniques

Key Points:

Description:

   Indications for limb lengthening have changed considerably over time. While devices and technologies have experienced a slow progression over the past few decades, there may be a noticeable advance with the recent introduction of internal magnetically lengthened nails.

  The techniques for limb lengthening were originally developed for correction of limb length discrepancy (Sabharwal, 2015). Cosmetic lengthening has increasing interest and remains controversial.

Acute versus Gradual Limb Lengthening

    Limb lengthening can be performed acutely or gradually. It can be done with internal fixation, external fixation, or a combination of both.

Acute limb lengthening

     Early attempts of limb lengthening were through acute lengthening.  Codivilla performed a transverse osteotomy, through which an intra-operative distraction was performed. The gap was maintained by applying up to 75 Kg of traction against the skin with a plaster cast (Codivilla, 1905). In modern history, acute distraction techniques have been described by several authors. Cauchoix and Morel in 1978 described a method of acute lengthening of the femur with internal fixation using plate and screws (Cauchoix, 1978). 

    Major complications can be associated with acute limb lengthening, including acute nerve injury, acute vascular injury, delayed union or nonunion requiring bone grafting, and subsequent implant failure. These issues, in addition to limited lengthening amount, have led to limited use of acute lengthening in modern practice.

    Transiliac lengthening is a method of acute lengthening that have been described by many authors and still used to correct leg length discrepancy in patients with acetabular dysplasia or fixed pelvic obliquity.  Millis and Hall in 1979 described a modified innominate osteotomy and reported an average amount of lengthening of 2.3 cm using acute transiliac lengthening.  An iliopsoas tenotomy is mandatory with this technique (Millis, 1979).

Gradual Limb Lengthening

     Gradual lengthening involves the common principles of (1) a low energy periosteum sparing osteotomy and (2) subsequent slow progressive distraction of the bone ends. The type of osteotomy, timing, rate of distraction and the distraction device can vary widely (Yasui, 2000). Gradual lengthening is the standard option and is the focus of the remainder of the article.

Techniques of Gradual Limb Lengthening 

Physeal Distraction  

     Physeal distraction involves gradual distraction of the growth plate (physis) in skeletally immature patients. It is also referred to as epiphyseal distraction, distraction epiphysiolysis, epiphysiolysis or chondrodiatasis (Ring, 1958; Zaziyalov, 1967).   

    De Bastiani in 1986 introduced the term “chondrodiatasis”  that involves physeal distraction without physeal separation. De Bastiani and co-workers concluded that chondrodiastasis using slow and regular distraction of 0.5mm/ day may stimulate metaphyseal ossification without  causing fissuring or separation of the growth plate (Franke, 1990).  

    Physeal distraction and chondrodiastasis have limited roles in limb lengthening in children due to several considerations. Children can experience severe pain due to physeal separation. Segmental fixation into the proximal tibial and the distal femoral physis may be intra-articular and may carry the risk of pin tract infection and septic arthritis. Moreover, physeal closure frequently occurs after physeal distraction. Chondrodiastasis has been found to have worse results in comparison to metaphyseal corticotomy and callotasis (Franke, 1990; Reichel, 1996).

Distraction Osteogenesis       

     Most current techniques of bone lengthening are based on the common principles of osteotomy and subsequent slow progressive distraction using an external fixation device (Yasui, 2000).

    Ilizarov in 1951 began developing his methods of “distraction osteogenesis”. He developed the process of new bone (termed regenerate) and soft tissue regeneration under the effect of slow and gradual distraction. Gradual traction on living tissue creates stresses that can stimulate and maintain the regeneration and active growth of certain tissue structures, termed the “law of tension stress” (Ilizarov, 1989; Paterson, 1990). 

Osteotomy Techniques

     Ilizarov performed a percutaneous subperiosteal “corticotomy”, with the premise that preservation of the intramedullary blood supply was important to the quality of new bone formation (Paterson, 1990).

    De Bastiani described a subperiosteal osteotomy performed in a low energy fashion with multiple drill holes and osteotome. He also recommended preservation of the periosteum and repairing it after the osteotomy is complete (De Bastiani, 1987; Aldegheri, 1993, 1997).

    Paley et al. described the percutaneous Gigli saw technique where a Gigli saw is passed subperiosteally to complete the osteotomy (Paley, 1991).

    Frierson et al. demonstrated in an animal study that bone lengthening can be successfully achieved after complete transection of the medullary canal and that there is no histologic or radiographic difference between the corticotomy described by Ilizarov and the transverse osteotomy described by De Bastiani (Aldegheri, 1994). 

Rate of Distraction

     The rate of callus distraction in both the Ilizarov method and the callotasis method is 1 mm/ day divided into 4 increments (0.25 mm every 6 hours) (Ilizarov, 1989; Aldegheri, 1989).  Smaller diameter bones may be lengthened at slower rates. 

Devices Used for Gradual Lengthening

    Devices used for gradual limb lengthening can be external, internal or a combination of both.

External Fixation

     Wagner first introduced his monolateral external fixator in 1978 (Wagner, 1978). Monolateral fixators are used on one side of the bone, formed of a rail or a telescoping body and clamps with a distractor device for lengthening. These devices are secured to the bone using conical or tapered half-pins.

    The Ilizarov circular fixator is composed of rings of varying diameter and uses cross K-wires for fixation (Paley, 2002).  Although the ring fixators used by Ilizarov are versatile, allowing the gradual correction of complex deformities during lengthening, the monolateral fixators may be better tolerated by patients particularly in the femur.

    In 1994, J. Charles and Harold S. Taylor modified the Ilizarov external fixator system by connecting six telescopic struts, thus controlling all six axes of movement and allowing for precise control of the two rings.  This hexapod frame uses computer software to program the precise adjustments to each strut (Paley, 2002).  The device simplifies complex bony corrections, with the primary downsides of cost and ability to work in short segments of bone.  

Combined Internal and External Fixation

     More recently, Paley et al. described gradual lengthening with monolateral external fixation performed over a lockable intramedullary rod. The technique consists of simultaneous insertion of the intramedullary rod, external fixation, and osteotomy. After the desired length is achieved, the patient undergoes a second stage of surgery when the external apparatus is removed and the rod is locked with screws. The “lengthening over nails” technique was shown to reduce the time in external fixation by half and resulted in earlier consolidation of the distraction gap, and led to a more rapid return of knee motion. However, the average blood loss and the cost of treatment is increased (Paley, 1998; Herring, 2002). Lengthening over a plate has also been described.

All Internal Lengthening using Intramedullary Nails 

     The first commonly used internal lengthening nail in the United States was the Intramedullary Skeletal Kinetic Distractor (ISKD) nail, which works on a ratcheting mechanism that relies on small rotational movements through the osteotomy. Several studies showed that ISKD nail lengthening was associated with high abnormal distraction rates (Sabharwal, 2015), termed a “run-away nail.”

    The recent developed remote-controlled magnetically driven lengthening nail is a new and promising advancement in the field of limb lengthening. Studies have shown that patients undergoing femoral lengthening using this nail demonstrated better consolidation indices, better knee mobility and decreased complication rates compared with conventional external fixation (Rozburch, 2014). Longer follow up is necessary to understand efficacy and safety profile of magnetic lengthening nails.

Epidemiology:

Clinical Findings:

Imaging Studies:

Treatment:

Complications:

The incidence of complications with limb lengthening ranges from 14 to 134%. (De Bastiani, 1987; Noonan, 1998) Potential complications include neurovascular injury, incomplete osteotomy, premature consolidation of the osteotomy, poor regenerate bone formation, joint subluxation, joint contracture, muscle weakness, regenerate bone fracture, superficial or deep infection, and psychologic stress to the patient and family.

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References:

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