Purpose of the study: A population of 154 patients was studied to determine the advantages of continuous lengthening for congenital lower limb length discrepancy (LLLD).

Material and methods: In a first series, we analyzed 80 progressive lengthenings using the standard rhythm (1 mm daily, 4 lenghtenings per day). In a second series (74 lengthenings) a high-frequency rhythm was used (1 mm daily, 60 lengthenings per day). Mean patient age was 10.3 years. Bone regeneration was not stimulated (either by extemporaneous compression or stable elastic centromedullary nailing) in this population. The automatic lengthening fixator was composed of the two standard pieces of the Ilizarov system and complementary blocks with self-propelled traction rods. Besides simplifying the lengthening procedure, these rods allowed high-frequency correction of associated deformities.

Results: Femoral gain was 52 mm on average. For the tibia, the gain was 48 mm on average. For ordinary monosegmentary lengthenings, the healing index was 27.6 d/cm for the femur and 36.0 d/cm for the tibia. For multisegmentary lengthenings with the standard rhythm, the overall healing index was 20.3 d/cm. For patients with high-frequency lengthening, time to healing was shorter. The radiological findings showed the presence of significant bone regeneration which was never inhibited. For monosegmentary lengthenings, the healing index was 22.9 d/cm for the femur and 27.1 d/cm for the tibia. For the multisegmentary high-frequency lengthenings, the overall healing index was 14.7 d/cm. The difference between standard and high-frequency lengthening was significant. In the first series, motion of the adjacent joints was recovered within 12 to 18 months after removal of the fixator. The patients remained in the reclining position during the high-frequency lengthenings and very satisfactory results (complete recovery of joint motion) were obtained 12 months after removing the fixator. In addition, in the second series, there was no impact on the spontaneous growth of the lengthened segments.

Discussion and conclusion: Congenital LLLD is generally more difficult to treat than acquired conditions (Damsin et al., Grill et al., Glorion Ch.). The rate of complications remains significant, particularly concerning healing complications and stiffness in the adjacent joints. Our clinical results prove that high-frequency lengthening provides optimal conditions for tissue regeneration. For children with congenital LLLD, continuous lengthening shortens the delay to healing and avoids stiffness in the adjacent joints.

We report a prospective study of 106 consecutive patients younger than 60 years old who suffered an intertrochanteric fracture of the proximal femur and were treated with an “Ilizarov” external fixator. All surviving patients were assessed with the assistance of the “CITO” evaluation system for fracture outcomes at three months post-injury and 73 patients were either clinically reviewed or contacted by a letter to establish the long-term results.

Complications included one intraoperative death, one case of post-traumatic ankylosis of the hip, two cases that were discharged in varus and one case in valgus of the femoral neck. Other complications included pin-track infections and stiffness at the level of the knee that required a year to resolve. Overall long-term satisfaction was high (76% in reviewed patients and 91% in patients contacted by letter).

The advantages of the “Ilizarov” external fixator include minimal disruption of the tissues and blood loss, capability of closed reduction of the fractures as well as post-operative manipulation of the fracture by gradual adjustments of the frame. This method, however, is time consuming, requires expertise and intense follow-up during the immediate post-operative period.

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.

Purpose: The purpose of this study was to evaluate centromedullary pinning for bone lengthening. We studied an animal model to discover the details of bone regeneration and assess the advantages of the technique. We present our early clinical results.

Material and methods: Progressive lengthenings of the tibia by centromedullary pinning were performed in eleven dogs. Distraction began on day 5 and lasted 28 days. Arteriograms were obtained after sacrifice.We also analysed 17 cases of limb lengthening in patients: one arm, two forearms, nine femurs, five tibias. Mean patient age was 14 years. Mean gain in bone length was 6.2 cm.

Results: The experimental work demonstrated that intensive bone regeneration requires faster distraction. Early bone union was observed in four dogs. Bone healing was complete at about 15 days in all dogs. The centromedullary pins were left in place in three dogs after removing the external fixator. There was no secondary deformation. The arteriogram showed that the nourishing artery was not ruptured. In our patients, delay to healing was shorter. The radiograms demonstrated intensive bone regeneration. Endosteal regeneration was significant and was never inhibited. Significant periosteal reaction was observed. The planned gain in length was achieved in all patients. We did not have any complications.

Discussion: Bone lengthening methods using a centromedullary nail provide absolute stability while avoiding external fixation but at the cost of complete destruction of the centromedullary vascular supply. Our animal experiments and clinical experience prove that elastic centromedullary pins do not inhibit endosteal regeneration but, on the contrary, partial destruction of the marrow with intact vascularisation stimulates bone regeneration. For bone lengthenings, centromedullary pinning is the only method of internal fixation allowing optimal conditions for bone regneration.

Conclusion: The progressive distraction of the elastic centromedullary pin during the lengthening period stimulates the regenerative processes. The biological effect of the vascular “displacement” from the centre to the periphery of the bone fragments leads to significant periosteal reaction. Elastic centromedullary pinning adds stability to the bone fragments. Associating the two methods allows removal of the external fixator leaving the centromedullary pins in place. By strengthening the regenerated bone, the pins provide a certain degree of additional stability.

Material: This work presents the treatment of 114 patients (125 feet), aged 9 – 53 years for:

- 82 short feet due to congenital metatarsal hypoplasia,

The cosmetic defect was the principal complaint in most patients (95 women), as well as complications related to wearing shoes. Pain in the forefoot resulted from biomechanical conflicts between the toes and the metatarals.

Methods: An oblique or transverse osteotomy for lengthening was performed on the base of the metatarsals and the phalanges. An external fixator, with modifications, was used. Pins were driven through the joints during the osteosynthesis to prevent dislocations. Traction was started three to five days after surgery at the rate of 0.5–1 mm/24 hr. Partial weight bearing on the operated limb was recommended. The external fixator was dismounted progressively with ablation of the pins allowing complete rehabilitation of the toes and walking exercises. These measured favour formation of regenerated bone and remodelling into hard bone, shortening treatment which was 45 ± 6 days in the study group.

Results: Outcome was followed for 1 – 3.5 years. The desired lengthening of the forefoot (1.5 – 5 cm was achieved in all feet. All feet were pain free and the cosmetic result and foot bearing on the floor was improved. The patients were satisfied, with no complaints, and walked with full weight bearing without complementary prostheses and wearing ordinary shoes.

Discussion: This experience in lengthening short tubular bones of the feet confirms the efficacy of the techniques used which provided good cosmetic and anatomo-functional results with one treatment.