Aims

Surgical limb sparing for knee-bearing paediatric bone sarcoma is considered to have a clinically significant influence on postoperative function due to complications and leg-length discrepancies. However, researchers have not fully evaluated the long-term postoperative functional outcomes. Therefore, in this study, we aimed to elucidate the risk factors and long-term functional prognosis associated with paediatric limb-sparing surgery.

Introduction. The practice of limb lengthening using intramedullary nails has surged in popularity in recent years. Our study explores the relationship between femur lengthening and overall height gain in adults undergoing cosmetic limb lengthening with telescoping magnetic intramedullary lengthening nails (MILNs). Materials & Methods. Demographic information, pre- and postoperative radiographic data, and secondary outcomes, such as mechanical angles and sagittal alignment, were analyzed for 42 adult femurs MILNs (PRECICE 2, NuVasive, Inc.). Height was assessed with a digital stadiometer. Limb lengthening was defined as the amount of nail distraction seen on a calibrated weight bearing X-ray at consolidation. mLDFA, mMPTA, MAD, AMA, and femoral sagittal bow were evaluated as secondary outcomes. Results. Mean starting height was 163.5 cm (SD 10.4, range 137–179) Post -lengthening mean height increased to 171.1 cm (SD 10.1, range 146.7–185.3). Average height gain was 7.5 cm (SD 1.3 cm, range 5.1–9.5). Average femoral lengthening was 7.3 cm (SD 1.14, range 4.1–10.1). There were no statistically significant difference between height gain and femur lengthening. Secondary outcomes showed reductions in femoral sagittal bow and AMA. Conclusions. We conclude that measuring femur lengthening is a reliable and accurate method of measuring gained height in deformity-free patients undergoing limb lengthening. We further reason that straightening of both femoral and spinal sagittal bow counteracts potential lengthening loss over the anatomical axis, versus mechanical axis lengthening

Introduction. At Sheffield Children's Hospital, treatment of leg length discrepancy is a common procedure. Historically, this has been done with external fixators. With the development in intramedullary technology, internal nails have become the preferred modality for long bone lengthening in the adolescent population. However, it is important to review whether this technology practically reduces the known challenges seen and if it brings any new issues. Therefore, the aim of this review is to retrospectively evaluate the therapeutic challenges of 16 fit-bone intramedullary femoral lengthening's at Sheffield Children's Hospital between 2021–2022. Materials & Methods. The international classification of function (ICF) framework was used to differentiate outcomes. The patient's therapy notes were retrospectively reviewed for themes around structural, activity and participation limitation. The findings were grouped for analysis and the main themes presented. Results. There were 8 males, mean age 17.4 years (range 17–18) and 8 females, mean age 15.9 years (range 14–18). 5 right and 11 left femurs were lengthened. Underlying pathology varied amongst the 16 patients. All patients went into a hinged knee brace post operatively. Structural limitations included: pain, fixed flexion deformity of the knee, loss of knee flexion, quadriceps muscle lag, muscle spasms and gluteal weakness. The primary activity limitation was reduced weight bearing with altered gait pattern. Participation limitations included reduced school attendance and involvement in activities with peers. Access to Physiotherapy from local services varied dramatically. Five of the cohort have completed treatment. Conclusions. Anecdotally, intramedullary femoral lengthening nails have perceived benefits for families compared to external fixators in the adolescent population. However, there remain musculoskeletal and psychosocial outcomes requiring therapeutic management throughout the lengthening process and beyond. Therefore, quantifying these outcomes is essential for measuring the impact on each patient for comparison. To interpret these themes, we need to evaluate the outcomes objectively, this was not done consistently in this review. Future research should look at outcome measures that are sensitive to all aspects of the ICF. With an aim of improving the therapeutic treatment provided and the overall outcome for the children treated

Introduction. “Bioexpandable” prostheses after resection of malignant bone tumors in children to lengthen the bone using the method of callus distraction may offer new perspectives and better long-term results. Materials and Methods. The bioexpandable prosthesis is equipped with an encapsulated electromotor which enables the device to perform distraction in an osteotomy gap with about 1mm/day. The new bone is improving the ratio from bone to prosthesis and therewith the potential stability of the final stem. The device is indicated, when limb length discrepancy is getting more than 3 cm or at maturity and can be used in a minimal invasive way for femur lengthening. Results. 11 patients were treated with the bioexpandable prosthesis. The mean age of the patients was 13,5 years and the mean amount of lengthening was 74mm. In 2 cases lengthening was performed in 2 steps and in 1 case in 3 steps. All lengthening procedures could be finished without complications. There was no infection and no technical problem. The bone regenerate in one tibia case was poor so that bone grafting from the iliac crest was necessary. Conclusions. The “bioexpandable” prosthesis is a new concept for limb lengthening after tumor resection in children. The latest patented version of the prosthesis under development allows all lengthening manoeuvres and the placement of the final stem via small incisions not only for the femur but also for the tibia

Aims

The management of a significant bony defect following excision of a diaphyseal atrophic femoral nonunion remains a challenge. We present the outcomes using a combined technique of acute femoral shortening, stabilized with a long retrograde intramedullary nail, accompanied by bifocal osteotomy compression and distraction osteogenesis with a temporary monolateral fixator.

Many studies describe the use of the Ilizarov ring fixator for lower limb lengthening and for the management of the 3-dimensional lower limb deformities in achondroplasia, and most confirm the efficacy of this technique. However, long term follow up of these achondroplastic patients is lacking. Most studies have focused on magnitude of lengthening, treatment time required and complications, but no study has analyzed the long term postoperative condition of these patients using an objective, functional method such as gait analysis. Nineteen (19) achondroplastic patients, 12 males and 7 females, aged 19–38 years (mean 27.3 y) who have undergone tibia and femur lengthening, using the Ilizarov method, at the age of 9–19 years (mean 12.6 y), were evaluated 5–19 years (mean 10.1 y) after their last surgery, using 3-dimensional gait analysis. Nineteen (19) normal, height-matched subjects were used as controls. The VICON Nexus 8 Camera System was used to accurately measure spatiotemporal characteristics (walking velocity, stride length, step length, cadence) and kinematics (range of motion) of lower limb joints. Statistical comparison of deformity parameters between achondroplastic patients and normal population was done using the student t- test. A level of p<0.05 was considered statistically significant. Walking velocity, step length and stride length were statistically significantly decreased (p<0.05) in achondroplastic patients compared to normal population values. The achondroplastic group presented with excessive anterior pelvic tilt (mean 21.9. o. ± 7.3), excessive pelvic rotation (range 28.7. o. ±7.8), decreased hip extension (mean 1.8. o. ±10.1) and decreased plantar flexion (mean 17.1. o. ±5.1) when compared to normal controls. There was no statistically significant difference in the knee kinematics between the operated achondroplastic patients and normal controls. The achondroplastic patients present decreased values in their spatiotemporal characteristics compared to the normal subjects because, despite the height gain, their lower limbs remain shorter. Their excessive anterior pelvic tilt is attributed to their lordosis. Their excessive forward pelvic rotation is an attempt to increase stride and step length. The decreased hip extension is due to their anterior pelvic tilt. The correction of these patients genu varum restored knee kinematics to normal. In order to address the hip and pelvis deformities a proximal femoral osteotomy should be considered. The Ilizarov method provides functional height gain and substantially corrects the three-dimensional lower limb deformities of achondroplastic patients especially around the knee joint but more planning needs to be implemented when the system is applied to correct the disease specific deformities of the hip and pelvis. Gait analysis is an objective tool that can be used to address these design issues

Aims

Patients undergoing femoral lengthening by external fixation tolerate treatment less well when compared to tibial lengthening. Lengthening of the femur with an intramedullary device may have advantages.

Explanations for “bearing” noise in ceramic-on-ceramic hips (COC) included stripe-wear formation and loss of lubrication leading to higher friction. However clinical and retrieval studies have clearly documented stripe wear in patients that did not have squeaking. Seldom highlighted has been the risk of metal-on-metal or metal-on-ceramic impingement present in total hip arthroplasty (THA) with metal and ceramic cup designs. The limitation in THA positioning studies has been (i) reliance on 2-dimensional radiographic images and (ii) patients lying supine on the examination table, thus not imaged in squeaking positions. We collected eleven squeaking COC cases for an EOS 3D-imaging functional study. Hip positions were documented in each patient's functional ‘squeaking’ posture using standard and 3-D EOS images for sitting, rising from a chair, hip extension in striding, and single-legged stance. EOS imaging documented for the 1st time that postural dysfunctions with potential impingements were demonstrable for each squeaking case. The 1st major insight in this study came from a female patient who complained of squeaking while walking in flat-soled shoes (Figs. 1a, b). She found that when wearing high-heeled shoes her hip stopped squeaking (Figs. 1c, d). Her lateral EOS view in standing position with heeled shoes revealed that the femoral stem had approximately 3o less hyper-extension compared to flat shoes (Figs. 1b, d, arrows #1,3). The three-dimensional ‘sky-view’ EOS reconstruction of pelvis and femurs (Fig. 2) showed that her femur was also more internally rotated when she wore heels. These subtle shifts in position changed her COC hip from one of squeaking to non-squeaking. A squeaking male patient observed similar postural effects while walking up his boat ramp but not going down the ramp. In both cases, the squeaking was a consequence of cup impinging on a metal femoral neck. Thus the primary cause of squeaking appeared to be hip impingement, i.e. repetitive subluxations that patients generally were not aware of. Another case is representative of situations due to atypical and subtle cup/stem mal-adjustments (Fig. 3); frontal pelvic-tilt, thoracolumbar scoliosis, with 1cm of femur lengthening and a significant increase of offset are observed. Also evident was the femoral-neck retroversion in both standing and sitting. Squeaking occurred when modification of the functional neck orientation occured in one-legged stance (Fig. 3c) or when climbing a stair (Fig. 3d). It was apparent in our EOS studies that patient functionality controlled whether squeaking occurred or not. Thus the new data indicated COC squeaking was a three-fold consequence of component positioning, spine and pelvic adaptions, and variations in patient posture. One limitation here is that our conclusions are based on a small sample of patients and may not be applicable to all. A consequence of such repetitive impingement can be cup rim damage and neck-notching, with release of metal debris. It is well documented that retrieved ceramic bearings are frequently stained black. Thus hip squeaking may likely result from (i) impingement and secondarily (ii) due to ingress of metal particles, and then (iii) producing a failure of lubrication. To view tables/figures, please contact authors directly

Aims

The primary aim of this study was to analyse the position of the acetabular and femoral components in total hip arthroplasty undertaken using an anterior surgical approach.

We describe the technique and results of medial submuscular plating of the femur in paediatric patients and discuss its indications and limitations. Specifically, the technique is used as part of a plate-after-lengthening strategy, where the period of external fixation is reduced and the plate introduced by avoiding direct contact with the lateral entry wounds of the external fixator pins. The technique emphasises that vastus medialis is interposed between the plate and the vascular structures.

A total of 16 patients (11 male and five female, mean age 9.6 years (5 to 17)), had medial submuscular plating of the femur. All underwent distraction osteogenesis of the femur with a mean lengthening of 4.99 cm (3.2 to 12) prior to plating. All patients achieved consolidation of the regenerate without deformity. The mean follow-up was 10.5 months (7 to 15) after plating for those with plates still in situ, and 16.3 months (1 to 39) for those who subsequently had their plates removed. None developed a deep infection. In two patients a proximal screw fractured without loss of alignment; one patient sustained a traumatic fracture six months after removal of the plate.

Placing the plate on the medial side is advantageous when the external fixator is present on the lateral side, and is biomechanically optimal in the presence of a femoral defect. We conclude that medial femoral submuscular plating is a useful technique for specific indications and can be performed safely with a prior understanding of the regional anatomy.

Cite this article: Bone Joint J 2014;96-B:137–42.

Introduction. Perthes' disease is associated with coxa breva, plana and magna, and a high riding prominent greater trochanter causing abductor shortening and weakness, leg shortening and extra-articular impingement. A trochanteric advancement with an infero-lateralising oblique sliding osteotomy of the proximal femur would lengthen femoral neck, improve abductor length and strength, relieve impingement and improve leg length. We assessed the mid-term outcomes for this procedure. Method. We included patients who underwent the operation by the senior author (JNOH) with more than 2 years follow-up. The osteotomies were performed minimally invasively under image intensifier guidance and fixed with blade plate or locking plates. We assessed functional scores, radiological changes in neck length, Tonnis grading for arthritis and evidence of femoral head avascular necrosis, time interval for conversion to hip arthroplasty and associated complications. Results. Twenty four patients (25 hips) underwent the procedure at mean age of 18.7 years (range:9.3–38.8) with a mean follow-up of 5 years (range:2–13.8). At the last assessment, the mean Oxford Hip Score was 41.6 (range:58–27), Non-Arthritic Hip Score was 53.4 (range:25–77) and UCLA activity score was 4.2 (range:2–6). For changes in neck length, the mean “Head-centre-to-Greater-trochanteric-tip-distance” was 60 mm (range:43–78) compared to 39 mm (range:30–48) pre-operatively and the mean “Head-centre-to-Lesser-trochanteric-tip-distance” was 54 mm (range:47–64) compared to 37 mm (range:31–41) pre-operatively. The mean Tonnis grade was 1.5 (range:1–3) compared to 1.3 (range:1–2) pre-operatively. Two patients underwent arthroplasty conversion at 2 and 13.8 years later. One patient needed head-neck debridement for impingement and 2 patients underwent trochanteric refixation for non-union. There were no cases of avascular necrosis. Discussion. Symptomatic Perthes' hip deformity in adolescents and young adults is difficult to treat with joint preserving surgery. The mid-term clinical, functional and radiological results for double proximal femur osteotomy are encouraging

Introduction. Perthes disease is associated with coxa breva, plana and magna, and a high riding prominent greater trochanter causing abductor shortening and weakness, leg shortening and extra-articular impingement. A trochanteric advancement with an infero-lateralizing sliding osteotomy of the proximal femur would lengthen femoral neck, improve abductor length and strength, relieve impingement and improve leg length. We assessed the mid-term outcomes for this procedure. Method. We included patients who underwent the operation by the senior author (JNOH) with more than 2 years follow-up. The osteotomies were performed under image intensifier guidance and fixed with blade plate or locking plates. We assessed functional scores, radiological changes in neck length, Tonnis grading for arthritis and evidence of progression in femoral head avascular necrosis, time interval for conversion to hip arthroplasty and associated complications. Results. Twenty four patients (25 hips) underwent the procedure at mean age of 18.7 years (range:9.3–38.8) with a mean follow-up of 5 years (range:2–13.8). At the last assessment, the mean Oxford Hip Score was 41.6 (range:58–27), Non-Arthritic Hip Score was 53.4 (range:25–77) and UCLA activity score was 4.2 (range:2–6). For changes in neck length, the mean “Head-centre-to-Greater-trochanteric-tip-distance” was 60 mm (range:43–78) compared to 39 mm (range:30–48) pre-operatively and the mean “Head-center-to-Lesser-trochanteric-tip-distance” was 54 mm (range:47–64) compared to 37 mm (range:31–41) pre-operatively. The mean Tonnis grade was 1.5 (range:1–3) compared to 1.3 (range:1–2) pre-operatively. Two patients underwent arthroplasty conversion at 2 and 13.8 years later. One patient needed head-neck debridement for impingement and 2 patients underwent trochanteric refixation for non-union. There was no progression in avascular necrosis of femoral head. Discussion. Symptomatic Perthes hip deformity in adolescents and young adults is difficult to treat with joint preserving surgery. The mid-term clinical, functional and radiological results for double proximal femur osteotomy are encouraging

Background. Lengthening over nail (LON) and the use of internal lengthening nails have been developed to minimize patients' time in a frame during femur lengthening. This study compares the outcomes of two techniques of femur lengthening, LON and Intramedullary Skeletal Kinetic Distraction (ISKD). Methods. In this retrospective study, 12 consecutive ISKD procedures were performed for femoral lengthening and followed for an average of 76 months. After the ISKD group, 20 consecutive femoral lengthening procedures were performed as an LON technique and followed for an average of 27 months. Results. There was no significant difference in achieving the lengthening goals between the two procedures. The healing index for the LON group averaged 1.4 months/cm, while the ISKD group was 3.2 months/cm (p=0.242). The distraction rates for the ISKD had a fast group (>1mm/day) with an average distraction rate of 1.7 mm/day and a slow group (<1mm/day) with a distraction rate of 0.84 mm/day. The LON group had an average distraction rate of 0.88 mm/day (p<0.001). The incidence of complications that required further unanticipated surgeries for the LON group was 1/20 (5%), while the ISKD group had complications in 6/12 femurs (50%, p=0.004). Conclusions. We concluded that the LON technique is a more predictable and reliable method for femoral lengthening than the ISKD

Lengthening of the humerus is now an established technique. We compared the complications of humeral lengthening with those of femoral lengthening and investigated whether or not the callus formation in the humerus proceeds at a higher rate than that in the femur. A total of 24 humeral and 24 femoral lengthenings were performed on 12 patients with achondroplasia. We measured the pixel value ratio (PVR) of the lengthened area on radiographs and each radiograph was analysed for the shape, type and density of the callus. The quality of life (QOL) of the patients after humeral lengthening was compared with that prior to surgery. The complication rate per segment of humerus and femur was 0.87% and 1.37%, respectively. In the humerus the PVR was significantly higher than that of the femur. Lower limbs were associated with an increased incidence of concave, lateral and central callus shapes. Humeral lengthening had a lower complication rate than lower-limb lengthening, and QOL increased significantly after humeral lengthening. Callus formation in the humerus during the distraction period proceeded at a significantly higher rate than that in the femur.

These findings indicate that humeral lengthening has an important role in the management of patients with achondroplasia.

Objective: The purpose of the present study was to assess whether clinicians are actually able to evaluate the mechanical status of lengthening callus from plain radiographs. Materials and Methods: 36 rats were employed in this study. Their left femurs were lengthened by 6 mm as a bone lengthening model. Rats were euthanized at 4 8 12 and 16 weeks after lengthening. Both femora were X-rayed and then bone density parameters (bone mineral content, bone mineral density and bone area) of lengthening callus were measured using pQCT. Three-point bending test was performed to determine the mechanical strength of the both bones. We defined the ratio of the strength of lengthening side to control side as estimated strength recovery rate (%). Then 20 orthopaedic surgeons evaluated only the X-ray photographs and tried to estimate the relative mechanical strength (%) of the affected side compared to the control side. Results: Between the recovery percentage of mechanical strength and bone mineral content, a positive simple correlation (R2=0.11, p< 0.05) was seen. No significant correlation was seen between the recovery percentage of mechanical strength estimated by orthopaedists and the mechanical strength measured by three-point bending test (qualified doctors: R2=0.0793 p=0.291 unqualified doctors: R2=0.0523 p=0.394). Discussion and conclusion: It became obvious that to estimate the strength of lengthening callus from plain radiographs alone is quite difficult as compared with the studies of the simple fracture model that have been reported until now

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.

We present a retrospective review of a single-surgeon series of 30 consecutive lengthenings in 27 patients with congenital short femur using the Ilizarov technique performed between 1994 and 2005.

The mean increase in length was 5.8 cm/18.65% (3.3 to 10.4, 9.7% to 48.8%), with a mean time in the frame of 223 days (75 to 363). By changing from a distal to a proximal osteotomy for lengthening, the mean range of knee movement was significantly increased from 98.1° to 124.2° (p = 0.041) and there was a trend towards a reduced requirement for quadricepsplasty, although this was not statistically significant (p = 0.07). The overall incidence of regenerate deformation or fracture requiring open reduction and internal fixation was similar in the distal and proximal osteotomy groups (56.7% and 53.8%, respectively). However, in the proximal osteotomy group, pre-placement of a Rush nail reduced this rate from 100% without a nail to 0% with a nail (p < 0.001). When comparing a distal osteotomy with a proximal one over a Rush nail for lengthening, there was a significant decrease in fracture rate from 58.8% to 0% (p = 0.043).

We recommend that in this group of patients lengthening of the femur with an Ilizarov construct be carried out through a proximal osteotomy over a Rush nail. Lengthening should also be limited to a maximum of 6 cm during one treatment, or 20% of the original length of the femur, in order to reduce the risk of complications.

Introduction: One of the four pillars of successful total knee arthroplasty (TKA) is restoration of the joint line. In conventional TKA the surgeon does not have a tool to control the accuracy of joint line restoration intraoperatively. The present study investigates if the preoperative joint line can be restored using an optical navigation system for TKA. Materials and methods: Patients from two Orthopedic Centers (Istituto Orthopedico Rizzoli Bologna, 51 patients; Orthopädie Samedan, 42 patients) received computer assisted TKA (Stryker Scorpio) using the Stryker Knee navigation system. Using the software delivered with the navigation system depth of femoral and tibial medial and lateral osteotomies were recorded. After definite prosthesis implantation medial and lateral femoral condyle height as well as tibial length including polyethylene inlay were also recorded. Varus/valgus alignment was additionally recorded before and after prosthesis implantation. Results: After femoral osteotomie varus/valgus alignment was 0 degrees (Stdv. 0.6 degrees). Lateral and medial osteotomies were performed with a depth of 8.2 and 8.8 mm respectively. Tibial osteotomie was performed with 0 degrees of varus/valgus (stdv. 0.7 degrees). Lateral and medial tibial osteotomies were performed with a depth of 7.5 and 4.8 mm respectively. After definite prosthesis implantation femoral and tibial varus/valgus alignment was 0.2 degrees of varus (stdv. 0.8 degrees) and 0.1 degrees of varus (stdv. 0.8 degrees) respectively. The femur was lengthened by 0.2 mm (stdy. 3 mm) medially and 1.1 mm (stdy. 3.1 mm) laterally. The tibia was shortened after component implantation by 1.5 mm (stdy. 3.4 mm) medially and 1.1 mm (stdv 3.1 mm) laterally. Discussion: With the use of the Stryker Knee Navigation System, we can reconstruct the preoperative joint line with reproducible accuracy after a TKA. When prosthesis component and polyethylene inlay thickness are known, osteotomies may be performed and corrected intraoperatively to restore the joint line

Since the time of Charles Darwin, it is known that three principles of regeneration explain the similarity of neo-formed tissues, the dependence of regeneration rhythm on age and the position of the animal in the evolutionary chain. The latter principle is know as the Weisman-Pschibram principle. Regeneration depends on several factors: level of tissue specialisation and differentiation, tissue resistance to hypoxia, and other manifestations of generally recognised biological regulation. According to a fourth principle, the regenerative potential of different parts of the body depend on a cranio-caudal gradient which rhythms their postnatal growth and development. Distinction of this principle is of importance because of its practical applications. Experience with increasing the height of persons with achrondroplasty by lengthening different limb segments reveals that the femur has less regeneration potential despite its long length. Leg lengthening is preferred; saving muscle function, there is a 20% potential for lengthening. Male subjects are generally considered to be short in height when there is a 10% growth retardation of the longitudinal dimension of the body. In female subjects, generative function is considered deficient if the length of the trunk is less than 73 cm. Using these criteria, experience has shown that leg malformations are not observed in subjects with a 10% growth retardation of the limb. The rate of growth retardation has to reach 40% before growth ceases. The relative moment of posterior leg muscle force increases with increasing leg length (F = 0.063 x L – 0.7; r=0.965, n=123). With a 10% growth deficit, the leg lengthening operation limits the amplitude of ankle movement 15% on average. With the same 10% growth deficit, lengthening the femur with the same technique decreases the amplitude of knee movement 22%. It has been noted that a 40% decrease in leg muscle force after leg lengthening does not affect locomotor function. The same decrease in thigh muscles after femur lengthening alters function. Like the first three principles, the fourth has its exceptions. It is important however to distinguish the influence of biological factors from other, for example technical, factors. Thus orthopaedic surgeons prefer the humerus for lengthening the upper limb, but this results from the difficulty in preserving rotation movements when lengthening the forearm. The important advances obtained in recent years in patients with bony defects of the hand and foot are further arguments clearly in favour of the existence of a cranio-caudal gradient in regenerative potential of the limbs