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Complications of bone lengthening.

Bone lengthening is a surgical method which requires meticulous technique, continuous attention, and satisfactory cooperation on the part of the patient. The absence of common criteria makes it difficult both to classify the complications which arise, and to compare them with those of other authors. We report the complications in a group of 61 patients who were studied prospectively. Disorders of the lengthening callus accounted for 45% of all complications, and a further 33% arose in the joints. The remainder occurred in the bone, the apparatus and the soft tissues, of which the most common were stiffness of the joints, axial deviations and loosening of the pins, while articular subluxation, fractures with angulation and delayed consolidation occurred less frequently. In our study, the overall number of complications per lengthening process was 2.1. In bilateral lengthening, the rate was 1 per segment, while in unilateral cases the mean was 2.7. Problems which we defined as severe, requiring that the lengthening had to be halted, occurred in 1.8% of the total complications. The aetiology of the length discrepancy has an important role in the complications which occur in each segment. Over twice as many problems occur in asymmetrical lengthening procedures as in patients where lengthening is symmetrical.

Bone Lengthening

Membranous bone lengthening: a serial histological study.

Bone lengthening using the process of corticotomy and gradual distraction of callus is applicable to the membranous bone of the canine mandible. In this study the precursors to bone formation, in the area between the distracted bone edges, are analyzed in an attempt to determine the mechanism of bone formation. Ten mongrel dogs 5 months of age were studied. A unilateral, periosteal-preserving angular corticotomy was performed, and an external bone-lengthening device was fixed to the mandible. After 10 days of external fixation, the mandible was lengthened 1 ml per day for 20 days and then held in external fixation for 8 weeks. The dogs were killed for histological and microradiographic study at 10 and 20 days of distraction, and at 14, 28, and 56 days after the completion of distraction. It was observed that the gap between the distracted bone edges is first occupied by fibrous tissue. As distraction proceeds, the fibrous tissue becomes longitudinally oriented in the direction of distraction. Early bone formation advances along the fibrous tissue, starting from the cut bone ends. Eventually the area is converted to mature cortical bone. Bone is formed predominantly by intramembranous ossification. This mechanism is similar to that of bone formation during long bone lengthening.

Animals

Biomechanical analysis of canine bone lengthened by the callotasis method.

The mechanical integrity of tibial bone treated by distraction osteogenesis (callotasis) using an Orthofix external fixator was evaluated in a group of 6 dogs. Diaphyseal corticotomies were performed on Day 0. Distraction was begun on Day 8, at a rate of 0.33 mm every 8 hours. On Day 34, the Orthofix frame was locked. On Day 56, the frames were removed and the dogs were euthanized. Radiographs were taken weekly to assess regenerate bone formation and extent of tibial bone lengthening, which averaged 12 mm (range, 5-20 mm). One dog showed incomplete bony union that was attributed to pin loosening. Torsional testing of lengthened and contralateral control tibiae resulted in spiral diaphyseal fractures. Five of 6 lengthened tibiae bones fractured within the diaphysis, but outside the regenerate area, suggesting that the strength of the lengthened segment exceeded that of the original diaphysis which was exposed to stress shielding by the external fixator. These observations have led to a method to test and evaluate lengthened bone at the time of frame removal and to monitor the effectiveness of this type of technique.

Animals

Biomechanical and physical properties of lengthened bone in a canine model.

Reports on the mechanical and physical properties of lengthened bone after completion of the lengthening process remain scarce. Varied results of torsional testing of lengthened bone have been reported. Furthermore, torsional testing provides information on the shear properties of the tissue but does not reflect the elastic properties obtained from tensile, compressive, or bending tests. The present study evaluated the mechanical properties of lengthened bone at various time points, using a uniaxial tension test. Physical properties (density and ash weight) were determined as well. Results indicate that the tensile properties of the lengthened bone increase with time after the completion of lengthening, but they remain significantly weaker than controls (50%) even after 12 weeks. Density and ash weight measurements also increased with time, correlating with the increase in the tensile mechanical properties.

Analysis of Variance

Bone lengthening in malformed upper limbs: a four year experience.

Bone lengthening by corticotomy, gradual distraction and stabilization with an external frame has proved to be effective in the repair of osseous defects in lower extremities. More recently this technique has been introduced also in the treatment of post-traumatic deformities and malformations of the upper limbs. From 1989 to 1992 we treated 38 patients (46 upper limbs) with bone lengthening of which 12 (16 upper limbs) affected by post-traumatic deformities and 26 (30 upper limbs) by malformations. We present herein our four year experience with malformed cases only. The results suggest that bone lengthening is a simple and reliable procedure to obtain good function, to correct angular deviations and, also, to give a better esthetic appearance. Satisfying results, low complication rates and simple execution recommend its use in the treatment of many congenital malformations of the upper limbs, usually in association with traditional techniques. However, we are now strongly selecting the indications in order to improve our future results. We stress in particular that the treatment of some malformations, as ulnar or radial club hands, could be radically modified by introduction of bone lengthening.

Arm

Bone lengthening in the craniofacial skeleton.

The process of bone lengthening by cortical fracture and gradual distraction of callus has become well established in the enchondral bones of the extremities. In this study the principles of bone lengthening were applied to the membranous bone of the craniofacial skeleton using the growing dog mandible as a model. Six mongrel dogs five months of age were studied. A unilateral, periosteal-preserving angular corticotomy was performed, and an external minilengthening device was fixed to the mandible perpendicular to the corticotomy. After 10 days of external fixation, the mandible was lengthened 1 mm/day for 20 days and then held in external fixation for 56 days (8 weeks) after which all dogs were killed. Anthropometric measurements and histological analysis of the specimens confirmed that bone lengthening had occurred and that new cortical bone was formed in the expanded areas.

Animals

Facial bone lengthening apparatus with expander and miniplates.

Since 1869, bone lengthening has been pursued; when Langenbeck tried growing a shortened bone extremity utilizing for this an arteriovenous fistula in the thigh. At the beginning of this century, codovilla (1905) introduced bone lengthening methods for lower limbs.

Bone Lengthening

Correlation between ultrasound imaging and mechanical and physical properties of lengthened bone: an experimental study in a canine model.

The right tibias of 16 adult mongrel dogs were lengthened 2.5 cm using a uniplanar lengthening device (Orthofix). After the animals were killed in groups of 4 at 3, 6, 9, and 12 weeks postlengthening, ultrasound imaging and mechanical and physical testing was performed. There was a direct relationship between the percentage of intact cortices on ultrasound imaging and the mechanical and physical properties of lengthened bone. However, once 80-90% of all the cortices regained their continuity, the strength of the lengthened bone was only 50-60% that of the control. Ultrasound imaging, therefore, may be useful in predicting the mechanical and physical properties of lengthened bone in the early phases of limb lengthening. Once all the cortices become continuous, however, another method for assessment of the mechanical properties of lengthened bone should be used.

Animals

[Distraction epiphyseolysis. An experimental study for bone lengthening. Part I (author's transl)].

Distraction epiphyseolysis is an operation for bone lengthening in children and adolescent which is often performed in Russia. Our experimental examination in rabbits has shown a lot of problems with this method. With distraction epiphyseolysis it is possible to get a primary lengthening of bone and a soon consolidation of the distraction-cleft. During further growth this primary lengthening is going lost. After the end of growth there was no significant difference between operated and non operated bone. The cause of the growth-disturbance is discussed in a further publication guided by histological findings.

Age Factors

A model for evaluating the strength of bones lengthened by distraction osteogenesis.

In an effort to evaluate the strength of bones lengthened by distraction osteogenesis, a modified Ilizarov-type external fixator was applied to the right tibiae of five adult mongrel dogs. Diaphyseal corticotomies were performed, and distraction (lengthening) was carried out at a rate of approximately 1 mm per day for 20 days. After completion of the lengthening, the animals were killed, the fixators were removed, and the right and left tibiae were harvested and stripped of soft tissue. The ends of all harvested bones were fixated in polymethylmethacrylate to allow testing on a materials testing system (MTS) machine. Testing under torsional loads was performed on the MTS machine (50 degrees maximum angle of rotation at ten seconds) until failure. The right tibiae were lengthened an average of 12 mm (range, 7-15 mm). The slopes of the linear portion of the torque versus rotation curves were determined. A comparison of slopes revealed a mean change in stiffness between test and control bones of 20.32% (range, 0.64%-40.5%). All tibiae exhibiting mature regenerate bone demonstrated stiffness greater than the matched controls (range, 0.64-24.09% stiffer). Four of five dogs had problems with proximal and distal ring impingement. This study presents a reproducible model for evaluating the strength of bones lengthened by distraction osteogenesis. The lengthened bones that exhibited bony or mature regeneration were as strong as the control bones.

Animals

Thumb reconstruction through metacarpal bone lengthening.

The experience with thumb reconstruction through metacarpal bone lengthening in 35 patients treated over a period of 12 years is presented. In 25 cases a spontaneous consolidation of the gap between the distracted fragments occurred, whereas in the remaining 10 the gap was bridged by a bone graft. The elongation of the metacarpal achieved varied from 2 to 4 cm. Examination of patients followed from 4 to 8 years after the treatment shows a good appearance of the reconstructed thumb without osteolysis or other trophic changes in the distal end. The quality of the skin sensibility in the amputation stump is preserved after the lengthening.

Adolescent

[Bone lengthening of the extremities using the Ilizarov method].

We describe the indications and the results in 18 bone lengthenings carried out on 14 patients in our department during the period January 1991 to September 1993. Seven patients had limb length inequality, five patients had dysplasia or aplasia, one patient had Turner's syndrome and one patient had suffered traumatic amputation of all the fingers of one hand. The mean lengthenings achieved were: femur 4.9 cm; tibia 5.6 cm; fibula 1.5 cm; humerus 7.5 cm; ulna 3.5 cm; radius 1.9 cm; and metacarpals 1.6 cm. There were 14 cases of pin-problems which needed surgery. Nine cases of infection around the pin holes were treated with antibiotics only. We had five cases with severe pain due to distraction. We had two cases of fracture after removal of the external fixation. Both fractures healed without further problems, but in one case there was three cm loss of the achieved lengthening. Our conclusion is that the Ilizarov method for bone lengthening is a demanding procedure. Because of the many--often minor--complications the patients must be seen frequently, as one must be prepared for "aggressive" treatment of the problems.

Arm

Bone lengthening in rabbits by callus distraction. The role of periosteum and endosteum.

The histology and mechanics of leg lengthening by callus distraction were studied in 27 growing rabbits. Tibial diaphyses were subjected to subperiosteal osteotomy, held in a neutral position for 10 days and then slowly distracted at 0.25 mm/12 hours, using a dynamic external fixator. Radiographs showed that the gap became filled with callus having three distinct zones. Elongation appeared to occur in a central radiolucent zone; this was bounded by two sclerotic zones. Histologically, the radiolucent zone consisted of longitudinally arranged cartilage and fibrous tissue while the sclerotic zones were formed by fine cancellous bone. New bone occasionally contained islands of cartilage, suggesting it had been formed by endochondral ossification. After completion of distraction, the two sclerotic zones fused, shrank and were eventually absorbed, leaving tubular bone with a new cortex. When the periosteum had been removed at the operation, callus formation was markedly disturbed and there was failure of bone lengthening. Scraping of endosteum, in contrast, did not have a pronounced effect. These results suggest that the preservation of periosteum is essential if bone lengthening by callus distraction is to succeed, and that preservation of the periosteum is more important than careful corticotomy.

Animals

Delayed distraction in bone lengthening. Improved healing in lambs.

We compared delayed distraction (DD) with immediate distraction (ID) in bone-lengthening. Open femoral diaphyseal osteotomy was performed on 24 three-month-old lambs, and external distractor fixators were applied. In the ID group (n 12), distraction commenced on the first postoperative day; in the DD group (n 12), distraction was delayed until the tenth day after surgery. In all the animals, the femur was lengthened by 2 cm at the rate of 1 mm/day. The animals were killed 1, 2, and 3 months postoperatively. Radiography and densitometry of the lengthened callus showed that DD, compared with ID, improved the quality of the callus with quicker, denser, and more homogeneous bone formation.

Animals