Intramedullary distraction for lower limb lengthening (interventional procedures consultation)


Interventional Procedure Consultation Document

Intramedullary distraction for lower limb lengthening

Some people have an abnormally short leg or legs because of disease or injury. Intramedullary distraction involves the surgical insertion of a special metal rod (distractor) inside either the shin (tibia) or the thigh bone (femur), which gradually forces the bone to lengthen.

The National Institute for Health and Clinical Excellence is examining intramedullary distraction and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute’s Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about intramedullary distraction.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

  • comments on the preliminary recommendations
  • the identification of factual inaccuracies
  • additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows.

  • The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
  • The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales and Scotland.

For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website (

Closing date for comments: 25 July 2006
Target date for publication of guidance: November 2006

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

1 Provisional recommendations

Current evidence on the safety and efficacy of intramedullary distraction for lower limb lengthening does not appear adequate for this procedure to be used without special arrangements for consent and for audit or research. Although there is evidence of its efficacy in lengthening the femur, evidence on its safety is inadequate. There is inadequate evidence on both efficacy and safety in its use for lengthening the tibia.


Clinicians wishing to undertake intramedullary distraction for lower limb lengthening should take the following actions.

  • Inform the clinical governance leads in their Trusts.
  • Ensure that patients understand the uncertainty about the procedure’s safety and efficacy in its use for the tibia and the uncertainty about its safety in its use for the femur and provide them with clear written information. In addition, use of the Institute’s Information for the public is recommended (available from
  • Audit and review clinical outcomes of all patients having intramedullary distraction techniques for lower limb lengthening.
1.3 A number of devices are available for the procedure which may have different safety and efficacy profiles. The technology is continuing to evolve and clinicians should consider the choice of device on the basis of the most current available evidence.
1.4 Publication of safety and efficacy outcomes will be useful. The Institute may review the procedure upon publication of further evidence.


2 The procedure
2.1 Indications
2.1.1 Length deficiency can occur in one or both legs and can be either acquired (for example, secondary to trauma or infection) or, more rarely, congenital (for example, due to hypoplasia or dysplasia). The femur or tibia, or both, can be involved. Deficiency or inequality in leg length can result in a limp and may limit functional ability.
2.1.2 Lengthening of the abnormally short leg can be attempted using external fixation devices. However, there is significant morbidity associated with external fixation, including infection of the pin tracts, pain, hip and knee sublaxation or dislocation, and angulation deformity of the bone. External fixation devices may also be impractical or aesthetically unacceptable to some patients.

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2.2 Outline of the procedure
2.2.1 Intramedullary distraction devices are similar to intramedullary nails used in the management of fractures of the femur and tibia. They have two interlocking sections so that controlled movement between the two pieces can be achieved. The device is implanted into the intramedullary space under general anaesthesia and an osteotomy is performed without damage to the periosteum and blood supply. The proximal and distal sections of the distraction system are then fixed to the relevant sections of the bone with locking screws. Once implanted, the device exerts a force along the long axis of the bone, which stimulates new bone formation and lengthening. This process occurs very slowly. Different devices achieve distraction in different ways: mechanically by releasing a pre-loaded spring or by using a motor drive.


2.3 Efficacy

The evidence reviewed was based on case series only. The reported mean values for lengthening achieved were 46 mm (n = 48 patients), 50 mm (n = 23) and 63 mm (n = 10) in the femur, and 49 mm (n = 18) in a mixed tibial and femoral case series. The rate of lengthening achieved ranged from 0.82 mm to 1.11 mm per day.

2.3.2 During femoral lengthening, knee flexion was reported to be restricted to a mean of 65° in one case series of 12 patients, although by 2 years this had improved to 115°. In another case series, the range of knee movement in 21 patients treated with unilateral lengthening was not significantly altered following the procedure. Average knee extension was 2.5° ? 5.9° at baseline and 2.5° ? 6.1° at follow-up. Knee flexion was 155° ? 19.2° at baseline and 145 ? 19° at follow-up.
2.3.3 In one series, results described as ‘excellent’ (evaluated using a composite outcome that included criteria of joint movement, gait, pain and functional ability) were achieved in 75% (18/24) of patients. In another series, full weight bearing was achieved at a mean of 67 days after the intervention among 48 patients; in a further series of 12 patients, full weight bearing was achieved at 3.2–8.8 months. For more details, refer to the sources of evidence (see appendix).
2.3.4 The Specialist Advisors considered the procedure to be novel and stated that it was still being refined. They also stated that, in comparison with external devices, there is a lack of control, which may lead to premature or delayed consolidation.


2.4 Safety
2.4.1 Few studies that reported safety outcomes relating to the procedure itself were identified. One case series (n = 52) reported femoral fissure and spontaneous bony section (not otherwise defined) during bone reaming in one patient. A second case series reported transient palsy of the peroneal nerve in 9% (2/23) of patients, which resolved within 3 months.
2.4.2 The most common postoperative adverse event reported was pain during limb lengthening. In one case series, all 31 patients experienced some degree of pain or discomfort during the lengthening process, and 39% (12/31) required re-admission and general anaesthesia to allow ratcheting (the motion that delivers extension of the nail). In two other series, analgesia was required for ratcheting in 4% (2/48) and 9% (2/23) of patients. In a case series that reported pain outcomes quantitatively, pain during ratcheting was rated as between 1.5 and 2.4 on a four-point scale among 48 patients undergoing lengthening of one or both femurs, and 1.5 points during bone consolidation periods. However, in two case series of 18 and 12 patients, no patient required pain control during lengthening.
2.4.3 Bone fractures (either during lengthening or after removal of the nail) were reported in three patients across the studies identified. The incidence of mechanical failure of the lengthening nail reported ranged between 4% (1 of 24 treated bones) and 16% (4 of 25 and 2 out of 12 patients). Mechanical failures included nail bending, failure or locking; broken wire or motor failure; and ratchet wear. For more details, refer to the sources of evidence (see appendix).
2.4.4 The Specialist Advisors stated that potential complications include poor bone formation, bone lengthening at an inappropriate rate (resulting in either bone weakness or premature consolidation), fat embolisation, deep vein thrombosis, respiratory distress syndrome and equinus ankle deformity.


3 Further information
3.1 This guidance requires that clinicians undertaking the procedure make special arrangements for audit. The Institute has identified relevant audit criteria and is developing an audit tool (which is for use at local discretion), which will be available when the guidance is published.

Bruce Campbell
Chairman, Interventional Procedures Advisory Committee
July 2006

Appendix: Sources of evidence

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

  • Interventional procedure overview of intramedullary distraction for lower limb lengthening, April 2006

Available from:

This page was last updated: 05 February 2011