Influence of size and stability of the osteotomy gap on the success of fracture healing

Flexible fixation of fractures with minimally invasive surgical techniques has become increasingly popular. Such techniques can lead to relatively large fracture gaps (larger than 5 mm) and considerable interfragmentary movements (0.2-5 mm). We investigated the influence of the size of the fracture gap, interfragmentary movement, and interfragmentary strain on the quality of fracture healing. A simple diaphyseal long-bone fracture was modeled by means of a transverse osteotomy of the right metatarsus in sheep. In 42 Sheep, the metatarsus was stabilized with a custom-made external ring fixator that was adjustable for gap size and axial interfragmentary movement. The sheep were randomly divided into six groups with three different gap sizes (1, 2, or 6 mm) and small or large interfragmentary strain (approximately 7 or 31%). The movement of the fracture gap was monitored telemetrically by a displacement transducer attached to the fixator. After 9 weeks of healing, the explanted metatarsus was evaluated mechanically in a three-point bending test to determine bending, stiffness and was radiographed to measure the amount of periosteal callus formation. Increased size of the gap (from 1 to 6 mm) resulted in a significant reduction in the bending stiffness of the healed bones. Larger interfragmentary movements and strains (31 compared with 7%) stimulated larger callus formation for small gaps (1-2 mm) but not for larger gaps (approximately 6 mm). The treatment of simple diaphyseal fractures with flexible fixation can be improved by careful reduction of the fracture; this prevents large interfragmentary gaps. The experimental fracture model for the metatarsus showed that the healing process was inferior when the gap was larger than 2 mm.     

The fracture gap size influences the local vascularization and tissue differentiation in callus healing

Background Revascularization of a fracture depends on fracture stability and fracture gap conditions. The aim of the study was to determine quantitatively the revascularization and tissue differentiation in an animal model with different fracture gaps and controlled biomechanical conditions.Materials and method The study was performed on ten sheep with an osteotomy on the right metatarsal. The fracture was stabilized by an external fixator that allowed adjustable axial interfragmentary movement. Two groups of five sheep each were adjusted to a medium sized gap (M, 2.1 mm) and a large gap (L, 5.7 mm) under comparable interfragmentary strain (30–32%). The animals were killed after 9 weeks, and the metatarsals were prepared for undecalcified histology and analysis of tissue differentiation and vessel distribution.Results Group M showed significantly more revascularization (M=1.62, L=0.85 vessels/mm²), more bone formation (M=37.2%, L=13.9%) and less fibrocartilage tissue (M=18.1%, L=39.1%) than group L. Larger vessels (>40 m) were found mainly in the medullary channel, and smaller vessels (<20 m) mainly in the peripheral callus. Histologically, group M showed partial bony bridging of the osteotomy gap, and the group L had delayed healing.Conclusion A good reduction of a fracture with small interfragmentary gaps is important for its revascularization and healing.     

The effect of laser osteotomy on bone healing

Osteotomy of the rat femur performed by the laser was compared to osteotomty made by a hand-saw cut. It was noted that, radiographically and histologically, there was a delay in healing in the laser group, but biomechanical testing failed to reveal any significant difference in bone strength.     

Optimal mechanical environment of the healing bone fracture/osteotomy

The aim of this paper is to review recent experimental and clinical publications on bone biology with respect to the optimal mechanical environment in the healing process of fractures and osteotomies. The basic postulates of bone fracture healing include static bone compression and immobilisation/fixation for three weeks and intermittent dynamic loading treatment afterwards. The optimal mechanical strain should be in the range of 100–2,000 microstrain, depending on the frequency of the strain application, type of bone and location in the bone, age and hormonal status. Higher frequency of mechanical strain application or larger number of repetition cycles result in increased bone mass at the healing fracture site, but only up to a certain limit, values beyond which no additional benefit is observed. Strain application and transition period from non-load-bearing to full load-bearing can be modified by implants allowing dynamisation of compression and generating strains at the fracture healing site in a controlled manner.     

Influence of age and mechanical stability on bone defect healing: age reverses mechanical effects

Non-unions and delayed healing are still prevalent complications in fracture and bone defect healing. Both mechanical stability and age are known to influence this process. However, it remains unclear which factor dominates and how they interact. Within this study, we sought a link between both factors. In 36 female Sprague-Dawley rats, the left femur was osteotomized, distracted to an osteotomy gap of 1.5 mm and externally fixated. Variation of age (12 vs. 52 weeks - biologically challenging) and fixator stiffness (mechanically challenging) resulted in 4 groups (each 9 animals): YS: young semi-rigid, OS: old semi-rigid, YR: young rigid and OR: old rigid. Qualitative and quantitative radiographical analyses were performed at weeks 2, 4 and 6 after surgery. Six weeks post-op, rats were sacrificed and femora were harvested for biomechanical testing (torsional stiffness (TS) and maximum torque at failure (MTF)). Six weeks after surgery, TS showed a significant interaction between age and fixation stiffness (p<0.0001). TS in YR was significantly higher than that in the other groups (YS: p<0.001; OR: p<0.001; OS: p<0.001). Additionally, YS showed a significantly higher TS compared to the OS (p=0.006) and OR (p=0.046). Testing of MTF showed a significant interaction of both variables (p=0.0002) and led to significant differences between OR and YS (p<0.001), OS (p=0.046) and YR (p<0.001). The YR showed a higher MTF compared to YS (p=0.012) and OS (p=0.001), whereas OR's MTF was inferior compared to OS. At 2-week follow-up, YR (p=0.006), and at 6-week follow-up, YS and YR (p=0.032) showed significantly higher radiographic scores. At 2-week follow-up, YS's callus was larger than that of the old groups (OS: p=0.025; OR: p=0.003). In YR a significantly smaller callus was observed compared to YS at time points 4 and 6 weeks (p=0.002 for both) and compared to OS at 6-week follow-up (p=0.03). The effect of age seems to invert the effect of mechanical properties of the callus, which was not correlated to callus size. Optimization of mechanics alone seems to be not sufficient. The underlying mechanisms and causes of the age-related influences and their clinical counterparts need to be further investigated.     

Mid-infrared erbium:YAG laser ablation of bone: the effect of laser osteotomy on bone healing

A comparative study was undertaken in rabbit tibiae to assess the healing of bone in response to osteotomies by a mid-infrared erbium: YAG (2.94 microns) laser or a mechanical saw. Laser parameters necessary for osteotomy were shown to produce deep cuts with sharp edges and no gross charring or burning of adjacent bone. However, it was noted histologically that there was a delay in healing of the laser osteotomies as compared to saw osteotomies. This delay was caused by a microscopic zone of damage to bone adjacent to the laser cuts. It is concluded that, although the erbium: YAG laser may be a useful tool in orthopaedic surgery to ablate bone, under the conditions used in this study, there will be a delay in the healing process after laser osteotomy.     

Distal femoral valgus osteotomy: bone healing time in single plane and biplanar technique

Varus deformity can be localized in the tibia, in the femur or in both. If varus deformity is localized within the femur, it is mandatory to correct it in the femur. This report presents the technique and results of a consecutive case series of lateral uniplanar and biplanar closed-wedge valgus osteotomy of the distal femur for the treatment of varus deformity of the knee. Retrospectively, fifteen patients (sixteen knees) were identified. Indications for surgery varied from unloading an osteoarthritic medial compartment to reduction to symmetrical varus leg alignment. Pre- and post-operative X-rays, including a full leg radiograph, were assessed as well as bone healing time at follow-up intervals. Clinical outcome was assessed using different questionnaires. There were nine male and six female patients with a median age at surgery of 45 (±14) years. The mLDFA changed from 95.9° (±2.7°) preoperatively to 89.3° (±2.9°) post-operatively. Preoperative planning and the use of angle stable implants resulted in accurate corrections according to preoperative aims in all but one patient. At follow-up (mean, 40 months), the mean VAS score was 2.5 (±2.4) and the WOMAC score averaged 80 (±20). The mean bone healing time of biplanar osteotomies (4 ± 3 months) was shorter than in the uniplanar osteotomies (6 ± 3 months). Distal lateral closed-wedge valgus osteotomy of the femur for the treatment of femoral varus deformities resulted in clinical improvement and accurate corrections in patients with different aims for correction. A biplanar osteotomy technique shortens bone healing time.     

Influence of soft tissue coverage on the healing of cortical defects in canine diaphyseal bone

The influence of soft tissue coverage on bone healing was investigated in dogs. A standard diaphyseal bone defect was left open, closed with skin, or closed with skin and muscle. Specimen radiography, callus morphometry, microscopy, and fluorescent microscopy were used to assess bone healing. The defects healed in all groups. Defects left open produced significantly more periosteal callus (p less than 0.01). Abscess formation was observed in the callus. The trabecular structure was abnormally oriented. Histomorphometric measurements of the rate of bone formation were the same regardless of the presence or type of soft tissue coverage. Failure to disturb the intramedullary blood supply may have minimized the differences in healing among the 3 groups. Nevertheless, soft tissue coverage was observed to prevent bone infection and to accelerate the restoration of normal cortical architecture.     

兔胫骨干骺端骨膜外截骨对延长区成骨作用的影响

[目的]研究兔胫骨干骺端骨膜外截骨对延长区骨膜成骨作用的影响。[方法]取健康成年中国家兔48只随机分为两组,对照组:左胫骨干骺端骨膜下截骨。实验组:左胫骨干骺端骨膜外截骨。术后第7 d开始延长外固定架,分别于术后7、17、27、37 d拍摄X线片观察延长区成骨情况;同时段随机在两组动物活体取延长区再生骨组织,制作HE染色切片,光镜下观察组织学变化;术后17、27 d常规电镜取材、制片后透射电镜下观察延长区细胞内变化。比较两组间的差异。[结果]观察两组术后第7 d X线片,均可见外固定架延长后遗留一清晰的牵张间隙,随着时间的延长,牵张间隙内逐渐出现越来越多的新生骨组织,骨密度影像也由低向高逐渐增加,但肉眼观察在影像学上两组无显著差异。HE染色示各时段实验组较对照组均有更为明显的成骨现象,两组差异性随时间推移逐渐减小。透射电镜示术后17、27 d,在超显微细胞器水平上,实验组较对照组有更多的粗面内质网扩张、高尔基复合体及线粒体增生。两组差异性随时间推移逐渐减小。[结论]兔胫骨干骺端骨膜外截骨有利于骨膜早期活跃性成骨作用。     

Bone allograft provides bone healing in the medial opening high tibial osteotomy

Various materials are used to fill osteotomy defects created in the medial opening wedge high tibial osteotomy (MOWHTO). Our hypothesis was that a bone allograft would provide the osteotomy site bone healing within the expected time. We performed the MOWHTO using a cancellous bone allograft in 310 knees in 284 patients between 2000 and 2005. Internal fixation was achieved with a T-profile AO plate. Preoperative and postoperative radiographic measurements were taken and statistically processed. All patients were followed up for a period ranging from three to eight years, or 5.9 years on average. Implanted cancellous bone allografts ≤9 mm healed within 12 weeks in 90% of cases. With the properly selected patient and surgical technique, use of a cancellous bone allograft in MOWHTO represents a satisfactory choice in providing bone healing.     

Temporary distraction and compression of a diaphyseal osteotomy accelerates bone healing

Mechanical strain during callus distraction is known to stimulate osteogenesis. It is unclear whether this stimulus could be used to enhance the healing of a normal fracture without lengthening the bone. This study tested the hypothesis that a slow temporary distraction and compression of a diaphyseal osteotomy accelerates fracture healing. Fourteen sheep underwent a middiaphyseal osteotomy of the right tibia, stabilized by external fixation. An external fixator allowed either a temporary axial distraction (TD group; n = 6) or a constant fixation (C group; n = 8). Distraction began 7 days postoperatively at a rate of 0.5 mm twice per day for 2 days with subsequent shortening of 1.0 mm twice on the third day. The procedure was repeated four times. Fluorochrome labeling was performed postoperatively. After 8 weeks the sheep were sacrificed and healing was evaluated using densitometric, biomechanical, and histological methods. Bending stiffness of the tibiae after 8 weeks was 58% higher in the TD group than in the C group. The volume of the periosteal callus was significantly (p = 0.05) higher in the TD group (3.9 cm³) than in the C group (2.7 cm³). There was 20% more bone in the fracture gap of the TD group than the C group. There was a significantly higher bone formation rate in the TD group than in the C group. This study demonstrated the feasibility of fracture healing stimulation by the temporary application of distraction and compression. © 2008 Orthopaedic Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:772–777, 2008     

Systemic corticosteroids inhibit bone healing in a rabbit ulnar osteotomy model

Prolonged systemic administration of corticosteroids causes osteoporosis and increased risk of fracture. Despite this well documented side effect of systemic corticosteroids, the effect of these compounds on fracture healing is not well defined. The goal of this study was to test the hypothesis that systemic corticosteroid therapy adversely affects fracture healing in a rabbit ulnar osteotomy model. Non-critical sized (1 mm) defects were created bilaterally in 18 adult female New Zealand White rabbits. Starting 2 months before operative intervention and continuing for 6 weeks during healing of the osteotomies, a subcutaneous dose of either sterile saline or prednisone (0.15 mg/kg) was administered daily. Serial radiographs of the forelimb were taken immediately postoperatively and weekly beginning the second week postoperatively. After killing at 6 weeks, only 3 of 20 limbs from animals treated with prednisone achieved radiographic union while 13 of 16 control limbs achieved union. The radiographic density of bone in the defect as well as callus size were greater in the control limbs than in the limbs from prednisone-treated animals. DEXA confirmed that the bone mineral content was lower in the ulnae of prednisone-treated rabbits both within the defect and in adjacent ulnar bone. Mechanical data indicated that osteotomies from rabbits chronically treated with prednisone were weaker than in controls. In this rabbit ulnar osteotomy model, chronic prednisone treatment clearly inhibited bone healing.     

Effect of preservation of corticoperiosteal attachment on bone healing at osteotomy sites after ulna-shortening osteotomy

Background

Although precise ulna-shortening osteotomy is popular, the procedure sometimes results in delayed union or nonunion. The periosteum including the inner cambium layer plays an important role in fracture healing. We tested the hypothesis that preservation of the corticoperiosteal attachment may accelerate healing at osteotomy sites after ulna-shortening osteotomy.

Methods

We performed a chart review of 32 patients who underwent ulna-shortening osteotomy for ulnar impaction syndrome or triangular fibrocartilage complex tears in a retrospective single-surgeon series. Of the 32 cases, the periosteum was preserved in 21 osteotomies performed from April 2009 onwards (periosteum-preserved group) and not preserved in 11 osteotomies performed before April 2009 (control group). Following sugar tong immobilization, patients in both groups used a short wrist supporter during the first two postoperative weeks (POW) and up to at least four POW. Union of the osteotomy site was assessed at 2-week intervals using radiographs taken at three different projections until 12 POW and at 4-week intervals thereafter until 24 POW. Ulna shortening was performed using a transverse osteotomy cut with the aid of a commercially available compression device.

Results

All osteotomies achieved complete union except in one case in the control group. The mean interval to complete cortical union was 7.7 weeks in the periosteum-preserved group and 9.5 weeks in the control group. The corresponding mean times for endosteal union were 15.6 and 21.8 weeks. The periosteum-preserved group had reduced times for both types of union but only the endosteal union time was significantly different from the control group.

Conclusions

Preservation of the corticoperiosteal attachment significantly shortened the endosteal union time. Our results indicate that preservation of the periosteum may accelerate bone healing after ulna-shortening osteotomy.     

Systemic corticosteroids inhibit bone healing in a rabbit ulnar osteotomy model

Prolonged systemic administration of corticosteroids causes osteoporosis and increased risk of fracture. Despite this well documented side effect of systemic corticosteroids, the effect of these compounds on fracture healing is not well defined. The goal of this study was to test the hypothesis that systemic corticosteroid therapy adversely affects fracture healing in a rabbit ulnar osteotomy model. Non-critical sized (1 mm) defects were created bilaterally in 18 adult female New Zealand White rabbits. Starting 2 months before operative intervention and continuing for 6 weeks during healing of the osteotomies, a subcutaneous dose of either sterile saline or prednisone (0.15 mg/kg) was administered daily. Serial radiographs of the forelimb were taken immediately postoperatively and weekly beginning the second week postoperatively. After killing at 6 weeks, only 3 of 20 limbs from animals treated with prednisone achieved radiographic union while 13 of 16 control limbs achieved union. The radiographic density of bone in the defect as well as callus size were greater in the control limbs than in the limbs from prednisone-treated animals. DEXA confirmed that the bone mineral content was lower in the ulnae of prednisone-treated rabbits both within the defect and in adjacent ulnar bone. Mechanical data indicated that osteotomies from rabbits chronically treated with prednisone were weaker than in controls. In this rabbit ulnar osteotomy model, chronic prednisone treatment clearly inhibited bone healing.     

Systemic corticosteroids inhibit bone healing in a rabbit ulnar osteotomy model

Prolonged systemic administration of corticosteroids causes osteoporosis and increased risk of fracture. Despite this well documented side effect of systemic corticosteroids, the effect of these compounds on fracture healing is not well defined. The goal of this study was to test the hypothesis that systemic corticosteroid therapy adversely affects fracture healing in a rabbit ulnar osteotomy model. Non-critical sized (1 mm) defects were created bilaterally in 18 adult female New Zealand White rabbits. Starting 2 months before operative intervention and continuing for 6 weeks during healing of the osteotomies, a subcutaneous dose of either sterile saline or prednisone (0.15 mg/kg) was administered daily. Serial radiographs of the forelimb were taken immediately postoperatively and weekly beginning the second week postoperatively. After killing at 6 weeks, only 3 of 20 limbs from animals treated with prednisone achieved radiographic union while 13 of 16 control limbs achieved union. The radiographic density of bone in the defect as well as callus size were greater in the control limbs than in the limbs from prednisone-treated animals. DEXA confirmed that the bone mineral content was lower in the ulnae of prednisone-treated rabbits both within the defect and in adjacent ulnar bone. Mechanical data indicated that osteotomies from rabbits chronically treated with prednisone were weaker than in controls. In this rabbit ulnar osteotomy model, chronic prednisone treatment clearly inhibited bone healing.     

Influence of pelvic osteotomy on birth canal size

Summary Six pelvic osteotomies (Salter, Sutherland, Steel, Tönnis, Chiari, and periacetabular) were performed on the right hemipelvis of adult female pelvic plastic models. Each pelvis underwent conventional X-ray and computed tomographic digital pelvimetry before and after osteotomy. The change in the anteroposterior and transverse dimensions at the inlet, midpelvis, and outlet were calculated. None of the osteotomies significantly decreased the inlet. The Salter and Sutherland osteotomies decreased the midpelvis to borderline low. The Salter, Sutherland, and Steel osteotomies significantly decreased the pelvic outlet. These changes correlated closely with those in living patients. Much of this decrease is nullified when the osteotomy is performed prior to the pubertal growth spurt.     

Histomorphometric evaluation of bone healing in rabbit fibular osteotomy model without fixation

Background  

Animal models of fracture consolidation are fundamental for the understanding of the biological process of bone repair in humans, but histological studies are rare and provide only qualitative results. The objective of this article is to present the histomorphometric study of the bone healing process using an experimental model of osteotomy in rabbit fibula without interference of synthesis material.