Intramedullary Skeletal Kinetic Distractor Research Articles

Intramedullary limb lengthening: Comparative mechanical testing of different devices

Background: Intramedullary limb lengthening has become more popular in the past two decades. This study aimed to investigate the mechanical properties of the various intramedullary lengthening devices currently available to orthopedic surgeons. Materials and Methods: A load cell connected to an electromechanical tensile testing machine was used to apply a bending force to nine intramedullary lengthening nails: Albizzia Ø 11 mm, intramedullary skeletal kinetic distractor Ø 10.7 mm, Precice Ø 10.7 mm, G-Nail Ø 13 mm, and Betzbone Ø 9 mm to Ø 13 mm. The force needed to deform each nail by 0.01 mm, 0.05 mm, 1 mm, and 3 mm was measured and compared. Results: The nail with the smallest diameter (Betzbone Ø 9 mm) needed the least force to deform. The nails with the biggest diameter (G-Nail Ø 13 mm and Betzbone Ø 13 mm) needed the most force to deform. Comparing similar-sized implants, nails manufactured from surgical steel or cobalt-chrome were more resistant to plastic deformation than titanium nails. Conclusion: Intramedullary lengthening device's ability to resist bending deformation depends on the diameter and material of the nail. Surgical steel and cobalt-chrome alloy nails showed higher resistant to plastic deformation when compared to titanium nails.

Relevant advances in bone lengthening research: a bibliometric analysis of the 100 most-cited articles published from 2001 to 2017.

This study aimed to assess the scientific production of bone lengthening research by identifying the most-cited papers. All articles including the term 'bone lengthening' published between 2001 and 2017 were retrieved through the Web of Science database. The 100 most-cited articles on bone lengthening included a total of 4244 citations, with 414 (9.7%) citations in 2017. There was an average of 249.6 citations per year. The articles predominantly addressed biomechanics and bone formation (38). Different surgical techniques, including intramedullary nail (14), Ilizarov (nine), intramedullary skeletal kinetic distractor (ISKD) (six), Taylor spatial frame (6), the PRECICE device (three), and lengthening and submuscular locking plate (three), were the second most-studied topic. Most studies were therapeutic (58), whereas 30 studies were experimental investigations using animal models. Among the clinical studies, case series were predominant (level of evidence IV) (57). This study presents the first bibliometric analysis of the most relevant articles on bone lengthening. The list is relatively comprehensive in terms of identifying the top issues in this field. However, the most influential clinical studies have a poor level of evidence, although a slight tendency toward a better level of evidence has been observed in more recent years.

Functional recovery of daily living and sports activities after cosmetic bilateral tibia lengthening.

The aims of this study were to evaluate the recovery of physical function and to investigate whether there are factors that adversely affect functional recovery after cosmetic bilateral lengthening of the tibia. One hundred twenty-five healthy individuals who had undergone bilateral cosmetic tibia lengthening by the lengthening and then nail (LATN) method, lengthening over intramedullary nail (LON) method or intramedullary skeletal kinetic distractor (ISKD) were included in the study. Functional outcomes were evaluated using the Sports Activity Rating Scale (SARS), International Knee Documentation Committee (IKDC) Subjective Knee Form and patient self-reported ability scores. SARS and IKDC scores decreased at post-operative oneyear and improved significantly at post-operative twoyears. SARS and IKDC scores recovered similarly to pre-operative levels. Average patient self-reported ability scores at post-operative twoyears were 94.6 and 89.9 for daily living and light sports, respectively. However, the average score for moderate-to-strenuous sports was 68.1 and 39 patients (31.2%) recorded below average score for the moderate-to-strenuous sports. Patients who had undergone bilateral cosmetic tibial lengthening may expect almost full recovery of daily and light sports activities at post-operativetwoyears. However, several patients may feel some limitation in moderate-to-strenuous sports activities.

Trochanteric Entry for Femoral Lengthening Nails in Children: Is It Safe?

Antegrade intramedullary (IM) nailing for skeletally immature femur fractures can damage the capital femoral epiphysis blood supply, leading to avascular necrosis (AVN) of the femoral head. Reported AVN rates are 2% for piriformis entry and 1.4% for trochanteric entry. None of previous reports described IM lengthening nails for limb lengthening procedures. We have used self-lengthening telescopic nails with a proximal Herzog bend and standard trochanteric entry for femoral lengthening in children. The purpose of this study is to determine whether trochanteric entry IM lengthening nails can be used safely (no AVN or proximal femoral deformity) in the skeletally immature femur. A retrospective review was performed between 2004 and 2014 to determine all skeletally immature patients younger than 18 years of age who had a reamed IM lengthening nail inserted through the greater trochanter, with at least 1-year follow-up. Thirty-one femurs were lengthened in 28 patients (17 males and 11 females). The etiology was congenital femoral deficiency (10), achondroplasia (6), post-traumatic (5), hemihypertrophy (3), Ollier disease (2), and miscellaneous (5). An attending surgeon was present for all procedures. Mean age at time of surgery was 12.9 years (range, 7 to 17 y). Mean follow-up was 3.5 years (range, 1.4 to 9 y). The average amount of lengthening was 5.4 cm (range, 3 to 6.7 cm). Twenty-four nails were 10.7 mm in diameter. Seven nails were 12.5 mm in diameter. Intramedullary skeletal kinetic distractor was used in 18 femurs and PRECICE in 13 femurs. Ten segments (7 intramedullary skeletal kinetic distractor; 3 PRECICE) experienced 13 complications. None of the patients developed AVN or proximal femoral deformity. IM lengthening nails inserted through the greater trochanter may be utilized in skeletally immature patients without increased risk of AVN of the femoral head or proximal femoral deformity. Larger trials would be helpful to confirm our hypothesis. We recommend careful surgical technique with liberal use of the image intensifier to avoid trauma to the femoral head blood supply. Level IV-therapeutic.

Treatment of gunshot fractures of the lower extremity: Part 2: Procedures for secondary reconstruction and treatment results

Gunshot wounds of the lower extremities are always serious injuries, especially in cases in which bone is affected. Contamination and extensive tissue damage can be life-threatening for the patient and severely affect the function of the extremity. Contamination and local infections with multidrug resistant pathogens are regularly encountered particularly in casualties evacuated from crisis regions. Treatment of this special type of injury, which differs in the form and extent from conventional high-energy trauma of the lower extremities, usually requires lengthy and extensive therapy algorithms in order to preserve the affected extremity. Based on the results of 34 gunshot wounds of the lower extremities which were surgically treated in this department between 2005 and 2011, this article reports on procedures used for wound management, soft tissue reconstruction and restoration of bone continuity. This group included 18 patients with a total of 20 gunshot-related fractures, 40% of which affected the lower leg and 35% the thigh. The affected extremities could be salvaged in all cases. The therapeutic spectrum required for bone reconstruction after soft tissue coverage demonstrated in these case examples ranged from conventional osteosynthesis with or without local cancellous bone transplant with platelet-rich plasma, to healing in a fixator, bone resection and the Masquelet method, distraction osteogenesis using a fixator in order to restore continuity and definitive secondary extension using an intramedullary skeletal kinetic distractor (ISKD) nail. Out of 15 bullet fractures affecting large tubular bones 8 could be healed without any shortening, axis deviation or malrotation. In 7 cases definitive shortening by an average of 20 mm (minimum 10 mm and maximum 40 mm) was necessary. The average treatment time before full weight-bearing was achieved within tolerable pain limits was 66 weeks (minimum 4 weeks and maximum 267 weeks). Secondary osteitis and osteomyelitis following primary restoration was detected in only one case. These results show that the treatment of gunshot wounds of the lower extremities is time-consuming and extensive and requires the complete spectrum of modern trauma surgery. Despite the high risk of complications during treatment it is possible and feasible to apply procedures that preserve the extremities.

Complications of the Intramedullary Skeletal Kinetic Distractor (ISKD) in Distraction Osteogenesis

The Intramedullary Skeletal Kinetic Distractor (ISKD) (Orthofix Inc, Lewisville, TX, USA) is an intramedullary device designed for more comfortable limb lengthening than that with external fixators; lengthening is achieved with this nail using rotational oscillation between two telescoping sections. However, the degree to which this device achieves this goal and its complication rate have not been fully documented. We determined (1) the frequency with which distraction was not achieved at the desired rate, (2) whether pain differed between patients with normally and abnormally distracting nails, (3) risk factors for abnormal nails, and (4) other complications. We analyzed 35 lengthening segments (26 femurs, nine tibias) in 19 patients. Mean length achieved was 47mm. Femoral nails were categorized into four groups according to distraction rate: normal, runaway (unintentionally faster rate [>1.5mm/day]), difficult-to-distract (slower rate [<0.8mm/day] requiring manual manipulation but not requiring general anesthesia), and nondistracting (slower rate [<0.8mm/day] requiring manual manipulation under general anesthesia or reosteotomy). Possible risk factors, including age, BMI, preoperative thigh circumferences, degree of intramedullary overreaming, and length of the thicker portion of the nail within the distal fragment, were compared among groups. VAS pain scores were compared among groups under three conditions: rest, physiotherapy, and distraction motion. Complications were also analyzed. Minimum followup was 15months (mean, 26months; range, 15-38months) after first-stage surgery. Abnormal distraction rate was observed in 21 of 35 segments (60%; 17 femurs, four tibias). VAS pain scores showed no differences among groups during rest or physiotherapy but were higher (p=0.02) in the problematic nails (7-8 points) versus normal nails (3 points) during distraction. Only mean length of the thicker portion of the nail within the distal fragment differed between normally and abnormally distracting nails (95mm versus 100mm; p=0.03), although this was unlikely to be clinically important. Complications occurred in 10 patients (53%), including five with decreased ankle ROM during distraction, four with delayed bone healing, and one with mechanical device failure during distraction. Rate control was difficult to achieve with the ISKD nail for femoral and tibial lengthenings, complications were relatively common, and among patients in whom rate control was not achieved, pain levels were high. Based on our findings, we believe that surgeons should avoid use of this nail. Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Limb-length Discrepancy After Total Hip Arthroplasty: Novel Treatment and Proposed Algorithm for Care

Limb-length discrepancy after total hip arthroplasty (THA) leads to patient dissatisfaction and can be a cause of orthopedic surgery malpractice cases. Nonsurgical and surgical techniques exist to correct limb-length discrepancies. Two limb-lengthening methods were used to correct greater than 2-cm limb-length discrepancies after THA: lengthening over a femoral nail with an external fixator and lengthening with an intramedullary kinetic skeletal distractor. These techniques achieved equal length in less than 4 weeks, with both resulting in a healed distraction gap within 4 months. No patient had loss of proximal or distal joint motion, and mean Harris Hip Score was 90 points at final follow-up. No surgical complications were reported with the intramedullary skeletal kinetic distractor. Limb lengthening using an intramedullary skeletal kinetic distractor is a viable treatment option resulting in reliable lengthening, healing of the distraction gap, and progression to full weight bearing.

Intramedullary skeletal kinetic distractor in lower extremity lengthening.

The aim of this study was to report the clinical and radiological results of patients with Intramedullary Skeletal Kinetic Distractor (ISKD) lengthening. Ten femoral and 2 tibial lengthening were performed in 12 patients (7 male, 5 female; mean age: 27 years (13-40)) by using ISKD nail. The mean limb length discrepancy of the patients was 4.41 cm (2-7). On the postoperative 7th day the patients were trained about lengthening and the lengthening started. Follow-up X rays were taken weekly during the distraction period and every second weeks during the consolidation period. One patient with tibia lengthening was lost to follow-up after completing the distraction period. The planned lengthening amounts were achieved in all of the cases. The mean lengthening was 4.41 cm (2-7). The mean bone healing index was 37.8 day/cm (28.5-78.0). There were uncontrolled distractions in 4 cases. Autogenous bone grafting was necessary in a case with incompetent bone formation. The kinetic nail was locked and failed to distract in a patient, in which the problem was solved with closed manipulation under anesthesia. No patient had a joint stiffness. Intramedullary extensible nails decrease the risk of joint contractures and infection. This procedure can be well tolerated by the patients and they can return to their daily activities earlier.

Sa2.7 Complications of limb lengthening with intramedullary Skeletal Kinetic Distractor (ISKD)

Sa2.7 Complications of limb lengthening with intramedullary Skeletal Kinetic Distractor (ISKD)

PF12 Limb lenghthening with intramedullary Skeletal Kinetic Distractor (iSKD)

Introduction: Fractures of the shaft of the femur are among the most common fractures encountered in orthopaedic practice. These fractures are often the result of high-energy trauma and may be associatedwithmultiple system injuries. Intramedullary interlocking nailing is a common used method for the treatment of femoral shaft fractures. Bending of an intramedullary nail due to secondary high-energy trauma is a rare condition. Nevertheless, bending intramedullary nail without a major trauma is a very rare condition in the literature. Materials andMethods:We report bending of an intramedullary nail which had been used in the treatment of a prior femoral diaphyseal fracture in a 19-year-old male patient who was admitted on foot to our outpatient clinic for a deformity in his right thigh. There was not any major trauma history. Results: The patient was operated 9 months ago because of femoral shaft fracture and he has not come to the last follow-up. In the plain radiographies bent femoral intramedullary nail and nonunion with refracture was detected. The bent nail was corrected partially by applying external force under anesthesia and then removed by standard extraction technique and osteosynthesis was performed with a thicker intramedullary locking nail. Conclusion: Bending of an intramedullary nail withoutmajor trauma like in this patient is very rare. Most of the cases in the literature occur due to high-energy trauma, and different extraction methods are described in the literature. Applying external force carefully may help to correct bent nail and this may facilitate the removal of nail.

Intramedullary Skeletal Kinetic Distractor in the Treatment of Leg Length Discrepancy—A Review of 16 Cases and Analysis of Complications

The intramedullary skeletal kinetic distractor (ISKD; Orthofix) is a relatively new device available for limb lengthening. This fully implantable mechanical nail promises reduced morbidity over traditional methods where external fixation is used. We report on our experience using this device in treating 16 patients with leg length discrepancy. Retrospective review of 16 consecutive patients treated with ISKD. Tertiary trauma hospital. Thirteen males and 3 females were treated with the ISKD between 2004 and 2009. There were 11 femora and 5 tibiae. The indication for lengthening was posttraumatic shortening in 15 patients and congenital hypoplasia in the remaining patient. Limb length gained, rate of lengthening, time to consolidation, complications, and factors that may be associated with complications. All patients in the series successfully completed treatment and reached the desired limb length with radiographic evidence of consolidation. The average leg length increase was 35 mm (21-75 mm). No infection, malunion, or joint contracture was observed. A length of less than 100 mm of the thick portion of the nail in the distal fragment is associated with the likelihood of a "runaway nail" (distraction index > 1.5 mm/d). Six patients had poor regenerate requiring bone grafting. Likelihood of poor regenerate was associated with number of previous operations on the lengthened bone. Three patients had nails that were difficult to distract and required closed manipulation under anesthesia. The ISKD is an effective method for correcting leg length discrepancies. Complications are frequent but are manageable with standard techniques. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The effect on mechanical axis deviation of femoral lengthening with an intramedullary telescopic nail

Internal lengthening devices in the femur lengthen along the anatomical axis, potentially creating lateral shift of the mechanical axis. We aimed to determine whether femoral lengthening along the anatomical axis has an inadvertent effect on lower limb alignment. Isolated femoral lengthening using the Intramedullary Skeletal Kinetic Distractor was performed in 27 femora in 24 patients (mean age 32 years (16 to 57)). Patients who underwent simultaneous realignment procedures or concurrent tibial lengthening, or who developed mal- or nonunion, were excluded. Pre-operative and six-month post-operative radiographs were used to measure lower limb alignment. The mean lengthening achieved was 4.4 cm (1.5 to 8.0). In 26 of 27 limbs, the mechanical axis shifted laterally by a mean of 1.0 mm/cm of lengthening (0 to 3.5). In one femur that was initially in varus, a 3 mm medial shift occurred during a lengthening of 2.2 cm. In a normally aligned limb, intramedullary lengthening along the anatomical axis of the femur results in a lateral shift of the mechanical axis by approximately 1 mm for each 1cm of lengthening.

Femoral Lengthening with Lengthening over a Nail has Fewer Complications than Intramedullary Skeletal Kinetic Distraction

Lengthening over a nail and internal lengthening nails have been developed to minimize or eliminate patients' time wearing a frame during femur lengthening. However it is unclear whether either of these two approaches results in faster times to union or fewer complications over the other. We asked which technique better achieved: (1) the lengthening goals, (2) the distraction rate control, (3) quality of the regenerate bone, (4) fewer complications, and (5) if SF-36 scores and American Academy of Orthopaedic Surgeons Lower Limb Module (AAOS LLM) scores differ in each treatment modality? We retrospectively reviewed the records and radiographs of 11 patients who had 12 Intramedullary Skeletal Kinetic Distractor (ISKD) procedures between 2002 and 2005, and 21 patients with 22 femoral lengthenings performed as lengthening over nail procedures between 2005 and 2009. Details such as leg length discrepancies, operative time, time of removal of the external fixator or ISKD, and any complications encountered were recorded. SF-36 and AAOS LLM scores also were compiled. The minimum followups for the ISKD and the lengthening over nail cohorts were 62 months (average, 76 months; range, 62-93 months) and 13 months (average, 27 months; range, 13-38 months), respectively. We observed no difference in achieving the lengthening goals between the two procedures. Distraction was not well controlled in the ISKD group; the distraction rates were 1.7 mm per day for the fast group (distraction rate greater than 1 mm/day) and 0.84 mm per day for the slow group (less than 1 mm/day). The lengthening over nail group had an average distraction rate of 0.88 mm per day. One of 20 of the patients who had lengthening over a nail had complications requiring additional unanticipated surgeries whereas six of 12 patients who had femoral lengthening in the ISKD group had such complications. Based on our observations, we believe the lengthening over nail technique for femoral lengthening is associated with fewer complications than the ISKD. Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Intramedullary limb lengthening with the Intramedullary Skeletal Kinetic Distractor in the lower limb

We report the results of intramedullary leg lengthening conducted between 2002 and 2009 using the Intramedullary Skeletal Kinetic Distractor in 69 unilateral lengthenings involving 58 femora and 11 tibiae. We identified difficulties that occurred during the treatment and assessed whether they were specifically due to the implant or independent of it. Paley's classification for evaluating problems, obstacles and complications with external fixators was adopted, and implant-specific difficulties were continuously noted. There were seven failures requiring premature removal of the device, in four due to nail breakage and three for other reasons, and five unsuccessful outcomes after completion of the lengthening. In all, 116 difficulties were noted in 45 patients, with only 24 having problem-free courses. In addition to the difficulties arising from the use of external fixators, there were almost the same number again of implant-specific difficulties. Nevertheless, successful femoral lengthening was achieved in 52 of the 58 patients (90%). However, successful tibial lengthening was only achieved in five of 11 patients (45%).

Mechanical failure of the Intramedullary Skeletal Kinetic Distractor in limb lengthening

Between October 2001 and September 2009 we lengthened 242 lower-limb segments in 180 patients using the Intramedullary Skeletal Kinetic Distractor (ISKD). Mechanical failure was defined either as breakage of the ISKD or failure of the internal mechanism to activate. Retrieved nails which failed mechanically were examined by the manufacturer for defects. In all, 15 ISKDs in 12 patients (13 limbs) failed mechanically representing an overall failure rate of 6.2%, with fracture of the device occurring in ten of the 15 failures. Two nails in one patient failed to lengthen and had to be replaced. The manufacturer detected an error in the assembly of the nail, which prompted a wide recall. One nail jammed after being forcefully inserted, and two nails failed to lengthen fully. Lengthening was achieved in all 12 patients, although three required a second operation to exchange a defective nail for a new, functioning device. The ISKD is a complex mechanical device which lengthens by the oscillation of two telescopic sections connected by a threaded rod. The junction between these sections is surrounded by a keyring collar. This keyring collar is the weakest part of the device.

Leg lengthening using intramedullay skeletal kinetic distractor: Results of 57 consecutive applications

Background Mechanically activated intramedullary lengthening nails are advantageous over external fixator. However, difficulties with the control of the distraction rate are the main drawbacks, which may in turn cause insufficient bone regenerate. Patients and methods A total of 57 lengthening procedures were performed using intramedullary skeletal kinetic distractor (ISKD) nail in 53 patients (femoral = 45 and tibial = 12). Average length gain was 4.3 ± 1.6 cm. The cause of shortening was post-traumatic ( n = 33), congenital ( n = 20), post-tumour resection ( n = 1), cosmetic femoral lengthening ( n = 2) and post-correction of distal femoral varus deformity ( n = 1). Results The desired lengthening was achieved in all patients. The mean follow-up period was 23 ± 12 months. The healing index for patients with normal bone healing was 1.2 ± 0.32 months/cm. Complications in femoral lengthening were superficial wound infection ( n = 1), premature consolidation ( n = 4) and insufficient bone regenerate ( n = 11), while in the tibial lengthening, two developed equinus contractures, one had compartment syndrome following implantation of the nail and one insufficient bone regenerate. Furthermore, nine runaway nails and three non-distracting nails were present in the femoral lengthening. One non-distracting nail responded to manipulation under anaesthesia, one required exchange nailing and accidental acute lengthening of 3 cm took place while manipulating the third nail. Patients with femoral lengthening and those with insufficient regenerate had significantly higher distraction rates ( P = 0.006 and 0.003, respectively). Six out of the nine runaway nails developed insufficient bone regenerate. In addition, 10.7-mm tibial ISKD nails were found to have lower rates of runaway nails compared with other used diameters. Conclusion We emphasise the rule of distraction rates above 1.5 mm/day in the development of insufficient bone regenerate. Distraction problems with these nails are mostly due to dysfunction within the ratcheting mechanism, which may be related to the diameter of the nail. New designs for mechanically activated nails with a better control mechanism for the distraction rate are required.

Korrektur einer posttraumatischen femoralen Beinverkürzung mit einem intramedullären Distraktionsmarknagel

For the operative adjustment of a leg length shortening and for correcting an angular deformity, an external fixator is the most frequently used technique today. This method may, however, be complicated by painful soft tissue and muscle fixations, pin infections and psychic strain as well as by long treatment duration with the external fixator. The intramedullary skeletal kinetic distractor (ISKD) is an internal lengthening nail, which promises a postoperative course without further complications. We used the ISKD nail in a 28-year-old traumatised motorcyclist, in whom, after removal of a comminuted femur bone fragment, a leg length shortening of 8 cm resulted. After uneventful healing of all fractures and having performed implant removal, we implanted an ISKD nail for femoral lengthening. The following distraction resulted, without considerable complications, in a complete compensation of the leg difference. The ISKD nail is a suitable procedure to compensate for post-traumatic leg length differences, which exhibits, in contrast to the frequently used external fixator, a largely uncomplicated course. It cannot be used to correct a gross transverse or rotational deformity.

Insufficient Bone Regenerate after Intramedullary Femoral Lengthening: Risk Factors and Classification System

Control of distraction rate with an intramedullary skeletal kinetic distractor (ISKD) may be problematic and a high distraction rate may result in insufficient bone regenerate. Are distraction problems preventable when using the ISKD, and what are the risk factors for and radiologic types of insufficient bone regenerate during ISKD lengthening? We analyzed 37 consecutive ISKD femoral lengthening procedures in 35 patients with a mean age 33 ± 11 years and minimum followup of 12 months (average, 27 ± 9 months; range, 12-55 months). The average length gain was 42.8 ± 12.9 mm. Eight patients had problems during distraction: seven had "runaway nails" and one had a nondistracting nail. Insufficient bone regenerate developed in eight patients. Important risk factors were a distraction rate greater than 1.5 mm/day (9.1 times higher risk), age 30 years or older, smoking, and lengthening greater than 4 cm. Less important risk factors identified were creation of the osteotomy at the site of previous trauma or surgery and acute correction of associated deformities. We proposed a radiologic classification for failure of bone regeneration: partial regenerate failure (Type I) or complete failure resulting in a segmental defect subdivided according to a length of 3 cm or less (Type IIa) or greater than 3 cm (Type IIb). Distraction problems with the ISKD were related mostly to internal malfunction of the lengthening mechanism. A distraction rate greater than 1.5 mm/day should be avoided in femoral intramedullary lengthening. Smoking should be a contraindication for femoral lengthening. Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Tibial Lengthening Over an Intramedullary Nail

Tibial Lengthening Over an Intramedullary Nail

Femoral lengthening with the Intramedullary Skeletal Kinetic Distractor

Femoral lengthening using the Intramedullary Skeletal Kinetic Distractor is a new technique. However, with intramedullary distraction the surgeon has less control over the lengthening process. Therefore, 33 femora lengthened with this device were assessed to evaluate the effect of operative variables under the surgeon's control on the course of lengthening. The desired lengthening was achieved in 32 of 33 limbs. Problems encountered included difficulty in achieving length in eight femora (24%) and uncontrolled lengthening in seven (21%). Uncontrolled lengthening was more likely if the osteotomy was placed with less than 80 mm of the thick portion of the nail in the distal fragment (p = 0.052), and a failure to lengthen was more likely if there was over 125 mm in the distal fragment (p = 0.008). The latter problem was reduced with over-reaming by 2.5 mm to 3 mm. Previous intramedullary nailing also predisposed to uncontrolled lengthening (p = 0.042), and these patients required less reaming. Using the Intramedullary Skeletal Kinetic Distractor, good outcomes were obtained; problems were minimised by optimising the position of the osteotomy and the amount of over-reaming performed.