Hydroxyapatite-coated Schanz pins in external fixators used for distraction osteogenesis : a randomized,controlled trial

BACKGROUND: Complications of external fixation include loosening of the fixation pins and pin-track infection. Laboratory studies and clinical trials have suggested that hydroxyapatite coating improves the osteointegration of various orthopaedic implants. The purpose of this study was to determine whether the prevalence of pin-related complications can be reduced by the use of hydroxyapatite-coated pins in fixators applied for distraction osteogenesis. METHODS: Forty-six consecutive patients undergoing segmental transport or lengthening of the tibia were randomized to the use of either standard titanium Schanz pins or hydroxyapatite-coated stainless-steel Schanz pins. The fixators were used for an average of thirty-eight weeks (range, fourteen to seventy-two weeks). All patients were closely monitored for pin loosening and infection, and digitized radiographs were assessed for bone resorption around all pins. When the external fixator was removed, the torque required to extract the pins was determined with use of an electronic torque wrench. RESULTS: In the control group (titanium pins), twenty-two pins (13%) loosened and an infection occurred at the site of twenty pins. An extensive infection of the canal developed in one patient. Twenty-two pins were removed or replaced because of these complications. In the hydroxyapatite group, no clinical or radiographic signs of pin loosening or infection were observed and no pins required early removal or exchange. The mean torque (and standard deviation) required to remove the hydroxyapatite-coated pins was 0.43 0.18 N-m compared with 0.10 0.09 N-m for the uncoated pins (p < 0.001). CONCLUSION: Coating pins with hydroxyapatite increases their fixation to bone and reduces the rate of infection and loosening during external fixation for distraction osteogenesis. Use of hydroxyapatite-coated pins should be considered in clinical situations requiring prolonged external fixation.     

The Effects of botulinum toxin A on muscle histology during distraction osteogenesis

Distraction osteogenesis is a highly successful method of bone formation, yet muscle fibrosis and contractures can result in significant morbidity. In the current study, we investigate the efficacy of botulinum toxin A in preventing fibrosis and potentially increasing muscle development in distracted muscles. Fifteen New Zealand White rabbits underwent tibial distraction at 1.5 mm/day until a 20% gain was achieved. Treatment groups were divided by drug (saline or botulinum toxin) and target muscle (gastrocnemius or tibialis anterior). Two additional control animals received no treatment. Bromeodeoxyuridine was delivered continuously throughout the 8‐week experiment, and following muscle harvest. Tissues were stained for BrdU, Pax‐7, vimentin, and haematoxylin and eosin staining. Mitotic activity increased in all distracted animals; however, in the animals receiving botulinum toxin A injections into the gastrocnemius, the antagonist tibialis anterior suffered up to 9% less fibrosis than distraction alone (p = 0.024). Use of botulinum A toxin did not appear to promote or improve neogenesis of muscle fibers, nor did it decrease fibrosis in the injected muscles. It appears from this study, and a previously published study on the effects of this toxin on muscle function, that botulinum A toxin maybe of some benefit in decreasing morbidity in the antagonist muscle but not the muscle injected with the toxin. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:310–317, 2009     

Limb salvage using distraction osteogenesis

Distraction osteogenesis is a novel technique for the biological restoration of segmental bone defects. Definitive treatment of musculoskeletal tumors often requires large bony resections that can leave patients with significant osseous defects. Limb salvage using distraction osteogenesis is an attractive reconstructive alternative that may, in fact, offer advantages over other conventional techniques. We present our initial experience with the use of distraction osteogenesis in limb salvage.     

Distraction osteogenesis by Ilizarov and unilateral external fixators in a canine model

We studied distraction osteogenesis in canine experimental model using two types of external fixators, Ilizarov (n=6) or AO unilateral (n=9) external fixator. Distraction started 1 week after surgery (2 x 0.5 mm/day) and lasted for 3 weeks. Specimens were harvested from weeks 7 through 12. The outcome was assessed by X-ray, histology, histomorphometry and microradiography. Bone regeneration as observed by X-rays was satisfactory and similar in both groups. Both endochondral ossification and intramembranous ossification were found simultaneously in both groups. In both groups, bone formation parameters were significantly higher in the area of consolidating bone. No differences in histomorphometric parameters existed between the groups. In the study period, the bone formation was enhanced and prevailed in the distraction area. This study demonstrated the utility of the canine experimental model for the study of distraction osteogenesis.     

The effect of mandibular distraction osteogenesis on the histology and immunohistology of keratinized gingiva.

OBJECTIVES: We investigated distracted keratinized epithelium to elucidate any proliferative and degenerated changes and to estimate the stability of the gingival tissues in mandibular distraction osteogenesis in a rabbit model. STUDY DESIGN: Twenty-two rabbits were subjected to unilateral vertical osteotomy. After a latency period of 4 days, devices were activated 3, 6, and 10 days at a rate of 1 mm/day. We additionally investigated the recovery of the distracted gingiva in consolidation periods for 3 weeks. The animals were examined by histologic and immunohistologic methods using proliferating cell nuclear antigen (PCNA), single-stranded DNA (ssDNA), and keratin. RESULTS: Atrophy of distracted gingiva was observed characterized by loss of rete ridges, acanthosis, vacuolation in the prickle cell layer, and cleavage of the keratin layer. Proliferating cell nuclear antigen-positive cells and ssDNA-positive cells were observed in the basal and prickle layers, respectively. During consolidation periods, slight recovery of rete ridges, thinning of the keratin layer, and immature epithelial layer was observed. CONCLUSIONS: Proliferative and degenerated changes occurred to compensate for cell death and distracted space. Thickness of gingival tissues was maintained by high mitotic activity and delay in the rate of cell maturation. Immature epithelial layer was related to sensitive and weak resistance against various stimulating factors, such as cleavage of the keratin layer among distracted gingival tissues.     

颧骨三维牵张器的初步研制

目的：探讨颧骨外固定三维牵张器的设计和制作。方法：根据机械移动原理，设计两块可相对移动的支撑板，一定范围内在两个垂直方向任意移动，带动牵张杆改变牵张方向，进行三维牵张成骨，在离体羊颅骨模型上进行模拟牵张成骨。结果：研制的三维缝牵张器重量30g，牵张杆前后向移动2cm左右、上下方向移动3．5cm左右，向外移动3cm左右，牵张控制准确，三维变向简便易行。结论：设计的外固定三维牵张器可以三维牵张，操作简便易行，控制准确。     

延长成骨术修复颅骨缺损的实验研究

目的探讨以延长成骨修复颅骨缺损的可行性。方法随机挑选1岁龄山羊17只,分为A、B、C三组,A组7只,于顶骨处左右各形成一大小相等面积为3.0 cm×2.2 cm矩形骨缺损;B组5只,于顶骨处右侧形成一2.2 cm×2.2 cm的正方形骨缺损;C组5只,于顶骨处左右各形成一大小为3 cm×1 cm矩形骨缺损。各组于右侧骨缺损形成相应的转移骨瓣并安放延长器,A组三维CT对修复颅骨面积进行测量;B组行成骨后生物力学测量;C组行组织学染色、扫描电镜、透射电镜检查观察成骨过程。结果A组可见实验侧骨缺损大部分逐渐被延长成骨所修复,剩余少量骨缺损与自身对照有统计学意义(P<0.01),B组实验侧与正常对照侧无统计学意义,C组观察成骨过程,为典型的膜内成骨。结论延长成骨术是一种可行的修复颅骨缺损的方法。     

Assessment of cell proliferation in regenerating bone during distraction osteogenesis at different distraction rates

An experimental model of lengthening of the lower limb was used to study the morphology and cellular proliferation of regenerating bone tissue after 20% lengthening at four rates of distraction. Groups of rabbits were killed at different times 1-8 weeks after surgery. The regenerated area was divided into three zones: fibrous, primary mineralization front, and new bone. As the rate of distraction increased, the size of the fibrous zone increased and that of Ihe new bone. one decreased. Necrosis, formation of cysts, and cartilage were found in the regenerated area at the higher distraction rates. Cell proliferation was assessed by in vivo labelling with' bromodeoxyuridine and the positive staining index for anti-bromodeoxyuridine antibody was calculated in the zones of the regenerated tissue, The index values for the fibrous zones and the new bone zones did not differ significantly in any of Ihe groups, The value increased significantly (p < 0,05) in the primary mineralization front as the rate of distraction increased from 0.3 to 0.7 mm/day, but there was no further significant increase at higher distraction rates. In conclusion, cell proliferation was increased at all of the higher rates (more than 0.3 mm/day) of distraction studied. Higher rates of distraction caused tissue damage. A distraction rate of 0.7 mm/day appeared optimal for cell proliferation and histological characteristics.     

Gradual reduction of distal radial malunion using distraction osteogenesis

PURPOSE: To evaluate gradual distraction lengthening or distraction osteogenesis as a technique for treating malunions of the distal radius. METHODS: Twenty patients with clinical and radiographic evidence of distal radius malunion were treated with osteotomy of the distal radius using distraction osteogenesis. At the follow-up evaluation each patient was evaluated for healing rates, complications, resolution of pain, and radiographic alignment. Surgical treatment consisted of an application of a nonbridging external fixator that could be distracted to correct the deformity. A loosely set screw that connected the distal pins to the fixator served as a hinge and allowed the distal radius to rotate into a corrected position. Gradual distraction via distraction osteogenesis was initiated 1 week after surgery. RESULTS: Seventeen osteotomies healed uneventfully in an average of 9 weeks. Complications included 9 pin track infections. Two nonunions required bone grafting. One patient inadvertently compressed rather than distracted the fixator, leading to premature healing of the osteotomy. One patient ruptured the extensor pollicis longus. All complications resolved with additional intervention. Overall the patients showed radiographic and symptomatic improvement. CONCLUSIONS: An external fixator and distraction lengthening through distraction osteogenesis is a viable alternative to plate fixation and bone grafting. In 18 of 20 of our patients, the technique eliminated the need for bone grafting and the need for a second surgical procedure to remove a dorsal plate.     

Fixation of trochanteric or subtrochanteric fractures using dynamic external fixators

We present a fixation system for trochanteric or subtrochjanteric fractures using a dynamic external fixator. The Citieffe/CH-N fixator was proposed for elderly patients with a significant operative risk (ASA III or IV). A long dynamic screw measuring 9 mm in diameter is inserted into the neck and the head of the femur on a guide wire through a tube protecting skin and muscles. This long screw is connected to the body of the fixator to enable impaction at the fracture level if compression is needed. The dynamic screw can be released to allow free gliding to achieve a dynamic fixation of the fracture. Distraction with the fixator can also be used for subtrochanteric unstable fractures to correct a varus deformity. This technique is a simple rapid solution with minimal operative risk. Complications are minimal and generally temporary, e.g. pin tract infections.     

Comparative clinical study on deformity correction accuracy of different external fixators

Purpose

In this study, the correction accuracy of Smart Correction spatial fixators and of Ilizarov-type external fixators are compared in terms of deformity complexity.

Methods

Seventy-seven (40 male, 37 female) bone segments of 57 patients treated with a Smart Correction device were compared with 94 (51 male, 43 female) segments of 68 patients treated with an Ilizarov fixator. Mean age of the Smart Correction group was 20.69?±?12.94 years, and or the Ilizarov group 22.45?±?12.18 years. Patients were categorised according to limb lengthening and the number of deformity planes.

Results

A longer correction period was found with Ilizarov (66.53?±?47.7 days) compared with Smart Correction (49.05?±?35.6 days) devices. The bone healing index of the Ilizarov group was significantly better compared with the spatial group. Residual deformity after treatment was significantly lower with the Smart Correction device; however, this relationship could not be shown between subgroups. Although there was no significant difference between subgroups, mean residual deformity was higher with the increasing number of planes of the deformity.

Conclusions

The Smart Correction fixator is an accurate device that allows ease of application and planning. It demonstrates higher accuracy for correcting deformities compared with an Ilizarov external fixator. With an increasing number of planes, the difference between the two devices becomes even more pronounced. The relationship between the complexity of the deformity and residual deformity may possibly be significantly greater in favour of the Smart Correction fixator in a study with a larger sample size.     

Fracture after distraction osteogenesis

We reviewed 173 patients undergoing distraction osteogenesis to determine the incidence, location and timing of fractures occurring as a complication of the procedure. There were 17 fractures in 180 lengthened segments giving an overall rate of fracture of 9.4%. Unexpectedly, the pattern and location of the fractures were very variable; six were within the regenerate itself, six at the junction between the regenerate and the original bone and five at distant sites in the limb. Of those occurring in the regenerate, five were noted to be associated with compression and partial collapse of the regenerate. In three patients collapse and deformity developed gradually in the distracted segment over the six months after removal of the frame. The method of treatment of these fractures should be chosen to take into account multiple factors, which are additional and often different from those to be considered during management of acute traumatic injuries. Internal fixation appears to be most appropriate for displaced fractures, although in small children, or in those in whom there has been, or is, infection of the screw tracks, a new period of treatment using external fixation may be needed. Fixation by intramedullary nailing was associated with a risk of infection, even if screw tracks were assessed as healthy at the time of insertion of the nail. Internal fixation with the use of plates is safe for displaced, unstable fractures in children.     

The relationship between distraction length and treatment indices during distraction osteogenesis

 To evaluate the indices used to compare the results of limb lengthening with distraction osteogenesis, we analyzed the relationship between the lengthening and external fixation period in a series of 28 patients (30 limbs). The average lengthening was 4.6  cm (range, 2.0–8.9). The average age at operation was 16.6 years (range, 4–47). Limbs treated included 15 femurs and 15 tibias of 19 male and 9 female patients. The external fixation period and the maturation period had a direct linear relationship with length gain. There was a negative hyperbolic relationship between the external fixation index, maturation index, and length gain. Segments that were lengthened 0–3.0  cm had a maturation index of 38.3 days/cm and external fixation index of 57.6 days/cm, both of which were significantly higher than for those lengthened more than 3.0  cm. When comparing the maturation and external fixation indices between different patients or studies, the length of the distraction must be taken into consideration. Received: June 14, 2001 / Accepted: January 7, 2002     

Role of external fixators for treatment of humeral fractures: report of 23 cases using Orthofix fixators

From 1991 to 1998, 23 humeral fractures has been treated using the Orthofix external fixator. Average age of the patient was 42 y and average follow-up 55.5 m. Initial trauma was: 13 traffic accidents, four falls at home, two devastating farming accidents, two sports accidents, one aggression and one gun accident. AO classification was used and location of the fracture was classified using Hackethal classification modified by de la Caffinière. Majority of fractures were located at the one-third distal humerus and the majority was also comminuted. At follow-up, elbow range of motion was 130 degrees, shoulder range of motion 161 degrees, external rotation 69.5 degrees and internal rotation 92.5 degrees. Using the classification of Stewart and Hundley, eight excellent, seven good, three fair and two bad results were obtained. There were no postoperative radial nerve palsy. Two external fixators had to be removed because of pin mobility. Failures were: non union and pin mobility in one patient which has to be reoperated on; two non unions have been grafted on and plated. There were no malunion in the postoperative X-rays. This device is our favourite for this type of injury because of its rigidity and the possibility of secondary dynamization. The external fixator was removed after union: this explains the long delay of union in our series.     

牙槽骨牵张成骨术在犬牙齿快速移动过程中的实验研究

目的：观察牙槽骨牵张成骨术在正畸牙齿快速移动过程当中,移动牙与支抗牙的牙周及牙髓组织改变。方法：杂种犬6只,拔除下颌第二前磨牙后,随机选取一侧为实验侧,进行外科减阻游离手术后,粘结自制牵引装置;另一侧为对照侧则以传统方法牵引下颌第一前磨牙向远中。结果：实验侧移动牙与支抗牙牙周及牙髓组织未发生可逆性改变,移动牙与下颌尖牙间离断处牙槽骨有大量新生成骨细胞。结论：牙槽骨牵张成骨术也是一种使正畸牙齿快速移动的有效方法。     

Rat model of distraction osteogenesis

Prior studies of distraction osteogenesis in dog and rabbit models have shown predominantly intramembranous bone formation. Other models of fracture healing normally display mixtures of both endochondral and intramembranous bone formation. We have established a rat model of tibial lengthening that reliably reproduces the pattern of zonal osteogenesis previously observed in dog and rabbit models. A distraction rate of 0.25 mm twice a day with a 0-day latency period produced intramembranous bone with zones of progressive mineralization from collagen. With this protocol, rats bridged the distraction gap with a 25% increase in the tibial bone length. After 20 days of distraction and 50 days of consolidation, the three-point bending stiffness, as a percentage of the contralateral control, reached a level equivalent to that measured in the canine model for a 15% lengthening (28-day distraction and 84-day consolidation). Radiodensitometric analysis of the regenerate bones measured 97% of the unaffected contralateral tibial densities, and mineral analyses demonstrated that calcium and phosphorus levels in the regenerate bone reached 78% of contralateral tibial levels by day 70. We concluded that a rat model of distraction ostegenesis will be useful for a wide range of studies involving rapid intramembranous bone formation.     

Management of comminuted closed tibial plafond fractures using circular external fixators

Various types of external fixators have been used to treat Ruedi and Allg?wer Type III pilon fractures, as serious complications can occur using conventional treatment principles. However, insufficient reduction and loss of reduction are two of the main disadvantages of external fixator treatments. We conducted a retrospective review of 14 patients with severe highly comminuted closed fractures of the distal tibia (Ruedi type III) treated using cross-ankle external fixators. Five patients underwent closed reduction, while the others required open reduction using minimal incision techniques. The reduction score, reduction loss, early and late complications, and ankle symptoms and functions were evaluated. The patients were followed for an average of 48 months (range: 31 to 84); superficial wound infection developed in one case and minimal angular deformity in another. In ten cases, the reduction of the articular surface was anatomical; in the other four cases, it was non-anatomical. Except for one case which developed an angular deformity, no loss of reduction was observed. On radiological control, only one case did not display osteoarthrosis; in the other 13 cases, osteoarthrosis was diagnosed at different levels. The most important disadvantage of this technique is retarded joint movement. Nevertheless, for such fractures, we consider cross-ankle circular external fixators as an alternative treatment method because it combines the advantage of a minimal risk of deep infections with better stabilisation of the limb, while providing early mobilisation.