Evolution of Limb Lengthening

Fortune at top of the Pyramid

Innovation and Fortitude at the base

A pyramid can represent the evolution of limb lengthening hardware. External fixation lengthening uses circular, monolateral, or hexapod fixators at the pyramid's base. It has the broadest indication base with the widest applicability. External fixators have the capacity to lengthen and correct deformities in any plane, perform an arthrodesis, or heal a nonunion. Previous or distant infection is not a deterrent. The hardware is readily available and affordable for most populations.

Surgery does not necessarily need highly controlled environments, is primarily percutaneous, has negligible blood loss, takes less time, and gives a little radiation dose to the surgeon. Rehabilitation is quicker, and fewer antibiotics are needed. All of these reduce costs for the patient or the health-care system. These benefits have been seen in multiple cultures and economies over many decades.

At Prof. Ilizarov's institute in Kurgan, patients stayed the entire duration of treatment. They had the benefit of immediate and continuous attention, the company of similar patients, prolonged in-house access to physiotherapy, all which ensured fewer complications and excellent results. This model was attempted in various centers, but the economics of prolonged hospital stay played spoilsport. It was gradually given up in favor of early discharge and repeated follow-ups, frequently over long distances. Joint stiffness, pin infection, and reduced activities were the banes of these simple devices. The need for vigilance in detecting axial deviation and the time and labor needed to make changes to the apparatus made it less attractive to the occasional limb reconstruction surgeon. Difficulties in follow-up and the prolonged duration of wearing the external devices discouraged many a patient from venturing on this journey. Those who undergo this treatment successfully may have the stoicism dividend and fortitude to aid them in coping with prolonged external fixation.

Paley et al.'s paper, in 1997,[²] marked the step up to the next level in the pyramid: hybrid lengthening hardware, combining either intramedullary nails or plates with external hardware. This would occupy the middle rung of the pyramid, with narrower indications. Internal hardware choice dramatically reduces external fixation duration and facilitates early joint knee range of motion. The additional advantage of this method is reduced axial deviation, especially with the corticotomy done in the diaphyseal bone. Initial hardware was restricted to standard curved trauma nails, and the limb reconstruction system or Ilizarov fixator and initial indications were simple lengthenings without deformity correction, performed at one level. With time, the indications expanded to perform deformity correction with lengthening at the same level. Over time, indications included performing a second task at a second level, like an arthrodesis or deformity correction. This prompted the use of the straight nail, usually a precursor in manufacturing the cured trauma nail. Customization included additional holes[³] for locking bolts in the center and using Poller screws, which helped narrow the nail's track in a wide metaphysis during acute deformity correction. Straight, rigid cannulated reamers helped convert a curved canal into a straight one, allowing easy nail sliding and aiding in deformity correction, especially in bowed femora.

Broader indications included using a humerus nail for femur lengthening in adolescents,[⁴] bone transport over a nail,[⁵] and double-level fixator-assisted nailing. Difficulties like deep intramedullary infection soon became apparent, as well as inadequate correction of deformities. The increased operative time, radiation exposure to the surgeon, blood loss caused by reaming, the need for higher antibiotics, and the need for a second surgery to lock the nail all increased costs. Limitations included the inability to use the technique with open growth plates, with sclerosed or badly deformed marrow canals, and to use proximal or distal entry portals due to bony deformity and contractures. Hence, indications narrowed, as did applicability to the spectrum across the populations.

Lengthening and then nailing[⁶] saw use for a while and chiefly helped convert deformed segments to straight ones, which could then be nailed easily. Lengthening and then plating[⁷] similarly reduced external fixation using the second minimally invasive submuscular plating surgery. Lengthening over plates[⁸] could achieve lesser lengthening due to the length of the plates. Kulkarni[⁹] recently introduced a slotted plate that guides alignment and prevents plate separation from bone. These innovations use simple and cost-effective technology and enable surgeons globally to offer lengthening with reduced external fixation duration.

Motorized internal lengthening nails[¹⁰] occupy the top rung of the pyramid. It now accounts for most of the lengthening literature and practice from affluent nations or where insurance and national health policies enable it. Surgeons and patients with these systems reap the rewards and fortunes of ease and convenience. While many internal lengthening nails have been withdrawn from the market due to failures and minor to significant glitches, the inevitable march of technology will ensure progress. The economics of scale will prevent these devices from being affordable to many worldwide.

Complications arising from hybrid or motorized lengthening devices need solutions involving the base of the pyramid: External fixation devices: either temporarily or for the remaining treatment.

The younger surgeon in many health-care environments would be better armed if he continued to study and master the techniques at the pyramid's base, just as younger surgeons have been advised to remain well-versed with the Ilizarov method when faced with difficulties of dealing with software-controlled external fixators.