Is it safe to assist proximal humeral nailing to residents? An analysis of 1134 cases.

INTRODUCTION: Intramedullary nailing is a common procedure for the treatment of proximal humeral fractures. In practical resident training this standardized operation plays an important role in the introduction to osteosynthesis. Our aim was to investigate whether assisting this operation to residents influences the surgical complication rate both in-house and on re-admission. METHODS: All 1134 patients who received a proximal humeral Targon PH nail (Aesculap) for proximal humeral fractures were included between 2000 and 2013. Several age groups (≤60 years, 61-70 years, 71-80 years, 80-90 years, and over 90 years) were analyzed separately. Complications including screw/nail protrusion, displacement, infection, humeral head necrosis, nonunion, stiffness, hematoma, impingement, screw loosening, implant failure, dislocation were recorded. 803 (70.7%) of the patients were female. Mean patient age was 71.7 years (standard deviation: 14.0 years). For detection of significantly different complication frequencies between operations performed by residents or attending physicians, we used the χ2 test in cases with all expected values greater than five, otherwise we used the two-sided Fisher's exact test. RESULTS: Supervised residents performed 204 operations. Overall complication rate was 12.6% (95% CI: 10.7-14.5%). The complication rate of the attending operations was 13.2% while it was 9.8% for resident operations. The difference was not significant. No statistically significant relation between age group and complication rate was found. In all patients older than 80 years the complication rate was higher when operated by residents compared to those operated by consultants, whereas in younger patients it was lower. Whereas the difference was not significant in patients younger than 60 and older than 80, we found significantly less complications in the group of patients between 61 and 80 years of age. On the other hand patients between 81 and 90 years displayed a 1.46 fold higher risk after training operations. No significant differences in the frequency of the different complications were found. CONCLUSION: We conclude that proximal humeral nailing is an operation suitable for teaching purposes. However, patients between 81 and 90 years of age seem to be at an increased risk for complications if operated by a resident.

Negative pressure wound therapy for seroma prevention and surgical incision treatment in spinal fracture care.

To evaluate the clinical use and economic aspects of negative pressure wound therapy (NPWT) after dorsal stabilisation of spinal fractures. This study is a prospective randomised evaluation of NPWT in patients with large surgical wounds after surgical stabilisation of spinal fractures by internal fixation. Patients were randomised to either standard wound dressing treatment (group A) or NPWT (group B). The wound area was examined by ultrasound to measure seroma volumes in both groups on the 5th and 10th day after surgery. Furthermore, data on economic aspects such as nursing time for wound care and material used for wound dressing were evaluated. A total of 20 patients (10 in each group) were enrolled. Throughout the whole study, mean seroma volume was significantly higher in group A than that in group B (day 5: 1·9 ml versus 0 ml; P = 0·0007; day 10: 1·6 ml versus 0·5 ml; P <0·024). Furthermore, patients of group A required more wound care time (group A: 31 ± 10 minutes; group B 13·8 ± 6 minutes; P = 0·0005) and more number of compresses (total number; group A 35 ± 15; group B 11 ± 3; P = 0·0376). NPWT reduced the development of postoperative seroma, reduced nursing time and reduced material required for wound care.

Incisional negative pressure wound therapy after hemiarthroplasty for femoral neck fractures - reduction of wound complications.

The aim of the study was to evaluate the use of incisional negative pressure wound therapy (iNPWT) in wound healing after femoral neck fracture (FNF) treated with hip hemiarthroplasty (HA) and its influence on postoperative seromas, wound secretion, as well as time and material consumption for dressing changes. The study is a prospective randomised evaluation of iNPWT in patients with large surgical wounds after FNF. Patients were randomised either to be treated by iNPWT (group A) or a standard wound dressing (group B). Follow-up included ultrasound measurements of seroma volumes on postoperative days 5 and 10, duration of wound secretion, and time and material spent for wound dressing changes. For comparison of the means, we used the t-test for independent samples, P > 0·05 was considered significant. There were 21 patients randomised in this study. Group A (11 patients, 81·6 ± 5·2 years of age) developed a seroma of 0·257 ± 0·75 cm(3) after 5 days and had a secretion of 0·9 ± 1·0 days, and the total time for dressing changes was 14·8 ± 3·9 minutes, whereas group B (ten patients, 82·6 ± 8·6 years of age) developed a seroma of 3·995 ± 5·01 cm(3) after 5 days and had a secretion of 4·3 ± 2·45 days, and the total time for dressing changes was 42·9 ± 11·0 minutes. All mentioned differences were significant. iNPWT has been used on many different types of traumatic and non-traumatic wounds. This prospective, randomised study has demonstrated decreased development of postoperative seromas, reduction of total wound secretion days and reduction of needed time for dressing changes.

Value of incisional negative pressure wound therapy in orthopaedic surgery.

Soft tissue and wound treatment after orthopaedic interventions (especially after trauma) is still an enormously challenging situation for every surgeon. Since development of negative pressure wound therapy (NPWT), new indications have been consistently added to the original field of application. Recently, NPWT has been applied directly over high-risk closed surgical incisions. Review of the literature indicates that this therapy has shown positive effects on incisions after total ankle replacement or calcaneal fractures, preventing haematoma and wound dehiscence. In those cases reduced swelling, decreased pain and healing time of the wound were seen. Additionally, NPWT applied on incisions after acetabular fractures showed a decreased rate of infection and wound healing problems compared with published infection rates. Even after total hip arthroplasty, incisional NPWT reduced incidence of postoperative seroma and improved wound healing. In patients with tibial plateau, pilon or calcaneus fractures requiring surgical stabilisation after blunt trauma, reduced risk of developing acute and chronic wound dehiscence and infection was observed when using incisional NPWT. To conclude, incisional NPWT can help to reduce risk of delayed wound healing and infection after severe trauma and orthopaedic interventions.

Ankle laxity: stress investigation under MRI control.

OBJECTIVE: The purpose of this study was to examine the advantages of MRI-guided ankle stress examinations in the detection of chronic ankle instability. SUBJECTS AND METHODS: An MRI-compatible stress device was developed and tested for MRI safety. Bilateral MRI stress examinations were performed on 50 volunteers with and without clinically evident subjective instability of the ankle joints (72 subjective stable ankle joints in 37 subjects, 28 ankles in 15 subjects with chronic ankle instability). Both the inversion test and the anterior drawer test were performed under axial, coronal, 45° paraxial, and sagittal T2-weighted fast spin-echo image control. MR images were assessed for talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, medial talocalcaneal translation, and the diameters of the lateral ankle ligaments (anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament). RESULTS: The MRI stress device was found suitable and safe for use in the MRI environment. The talocrural and subtalar joints could be assessed simultaneously. Significant differences between groups A and B (p≤0.05) were found in talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, medial talocalcaneal translation, and decrease in diameters of calcaneofibular and posterior talofibular ligaments. Also found were sex differences in talar tilt, subtalar tilt, anterior talus translation, and diameters of the anterior talofibular, calcaneofibular, and posterior talofibular ligaments. Significant relations were found between talar tilt and anterior talus translation, subtalar tilt and anterior calcaneus translation, subtalar tilt and medial talocalcaneal translation, and between anterior calcaneus translation and medial talocalcaneal translation in groups A and B. CONCLUSION: Stress examination under MRI control has advantages in the assessment of mechanical ankle instability. Additional diagnostic and clinically relevant information is obtained through direct imaging of the ligaments and assessment of additional parameters of ankle laxity (subtalar tilt, anterior calcaneus translation, medial talocalcaneal translation). The main advantages are objective imaging and measurement of abnormal looseness of the lower ankle joint and its direct simultaneous comparison with the upper ankle joint.

A signal-inducing bone cement for magnetic resonance imaging-guided spinal surgery based on hydroxyapatite and polymethylmethacrylate.

The aim of this study was to develop a signal-inducing bone cement for magnetic resonance imaging (MRI)-guided cementoplasty of the spine. This MRI cement would allow precise and controlled injection of cement into pathologic lesions of the bone. We mixed conventional polymethylmethacrylate bone cement (PMMA; 5 ml methylmethacrylate and 12 g polymethylmethacrylate) with hydroxyapatite (HA) bone substitute (2-4 ml) and a gadolinium-based contrast agent (CA; 0-60 µl). The contrast-to-noise ratio (CNR) of different CA doses was measured in an open 1.0-Tesla scanner for fast T1W Turbo-Spin-Echo (TSE) and T1W TSE pulse sequences to determine the highest signal. We simulated MRI-guided cementoplasty in cadaveric spines. Compressive strength of the cements was tested. The highest CNR was (1) 87.3 (SD 2.9) in fast T1W TSE for cements with 4 µl CA/ml HA (4 ml) and (2) 60.8 (SD 2.4) in T1W TSE for cements with 1 µl CA/ml HA (4 ml). MRI-guided cementoplasty in cadaveric spine was feasible. Compressive strength decreased with increasing amounts of HA from 46.7 MPa (2 ml HA) to 28.0 MPa (4 ml HA). An MRI-compatible cement based on PMMA, HA, and CA is feasible and clearly visible on MRI images. MRI-guided spinal cementoplasty using this cement would permit direct visualization of the cement, the pathologic process, and the anatomical surroundings.

A 5-mm femoral defect in female but not in male rats leads to a reproducible atrophic non-union.

INTRODUCTION: The objectives of this study were to (1) establish a reproducible atrophic non-union model in rats by creation of a segmental femoral bone defect that allows, (2) in-depth characterization of impaired healing, and (3) contrast its healing patterns to the normal course. Hypothesis was that a 5-mm bone defect in male rats would deviate from uneventful healing patterns and result in an atrophic non-union. MATERIALS AND METHODS: A femoral osteotomy was performed in two groups of 12-week-old male rats (1 vs. 5 mm gap) stabilized with an external fixator. Bone healing in these models was evaluated by radiology, biomechanics, and histology at 6 or 8 weeks. The evaluation of the 5-mm group revealed in some cases a delayed rather than a non-union, and therefore, a group of female counterparts was included. RESULTS: The creation of a 5-mm defect in female rats resulted in a reproducible atrophic non-union characterized by sealing of the medullary canal, lack of cartilage formation, and negligible mechanical properties of the callus. In both gap size models, the male subjects showed advanced healing compared to females. DISCUSSION AND CONCLUSION: This study showed that even under uneventful healing conditions in terms of age and bone defect size, there is a sex-specific advanced healing in male compared to female subjects. Contrary to our initial hypothesis, only the creation of a 5-mm segmental femoral defect in female rats led to a reproducible atrophic non-union. It has been shown that an atrophic non-union exhibits different healing patterns compared to uneventful healing. A total lack of endochondral bone formation, soft tissue prolapse into the defect, and bony closure of the medullary cavity have been shown to occur in the non-union model.

Standard bone healing stages occur during delayed bone healing, albeit with a different temporal onset and spatial distribution of callus tissues.

Bone healing is considered as a recapitulation of a developmental program initiated at the time of injury. This study tested the hypothesis that in delayed bone healing the regular cascade of healing events, including remodeling of woven to lamellar bone, would be similar compared to standard healing, although the temporal onset would be delayed. A tibial osteotomy was performed in sheep and stabilized with a rotationally unstable fixator leading to delayed healing. The sheep were sacrificed at 2, 3, 6, 9 weeks and 6 months postoperatively. The temporal and spatial tissue distributions in the calluses and the bone microstructure were examined by histology. Although histological analysis demonstrated temporal and spatial callus tissue distribution differences, delayed healing exhibited the same characteristic stages as those seen during uneventful standard healing. The delayed healing process was characterized by a prolonged presence of hematoma, a different spatial distribution of new bone and delayed and prolonged endochondral bone formation. A change in the spatial distribution of callus formation was seen by week 6 leading to bone formation and resorption of the cortical bone fragments, dependent on the degree to which the cortical bone fragments were dislocated. At 6 months, only 5 out of 8 animals showed complete bony bridging with a continuous periosteum, although lamellar bone and newly formed woven bone were present in the other 3 animals. This study demonstrates that during delayed bone healing all stages of the healing cascade likely take place, even if bony consolidation does not occur. Furthermore, the healing outcome might be related to the periosteum's regenerative capacity leading to bony union or absence of bony bridging.

Mechanical stimulation of the pro-angiogenic capacity of human fracture haematoma: involvement of VEGF mechano-regulation.

Compromised angiogenesis appears to be a major limitation in various suboptimal bone healing situations. Appropriate mechanical stimuli support blood vessel formation in vivo and improve healing outcomes. However, the mechanisms responsible for this association are unclear. To address this question, the paracrine angiogenic potential of early human fracture haematoma and its responsiveness to mechanical loading, as well as angiogenic growth factors involved, were investigated in vitro. Human haematomas were collected from healthy patients undergoing surgery within 72 h after bone fracture. The haematomas were embedded in a fibrin matrix, and cultured in a bioreactor resembling the in vivo conditions of the early phase of bone healing (20% compression, 1 Hz) over 3 days. Conditioned medium (CM) from the bioreactor was then analyzed. The matrices were also incubated in fresh medium for a further 24 h to evaluate the persistence of the effects. Growth factor (GF) concentrations were measured in the CM by ELISAs. In vitro tube formation assays were conducted on Matrigel with the HMEC-1 cell line, with or without inhibition of vascular endothelial growth factor receptor 2 (VEGFR2). Cell numbers were quantified using an MTS test. In vitro endothelial tube formation was enhanced by CM from haematomas, compared to fibrin controls. The angiogenesis regulators, vascular endothelial growth factor (VEGF) and transforming growth factor beta1 (TGF-beta1), were released into the haematoma CM, but not angiopoietins 1 or 2 (Ang1, 2), basic fibroblast growth factor (bFGF) or platelet-derived growth factor (PDGF). Mechanical stimulation of haematomas, but not fibrin controls, further increased the induction of tube formation by their CM. The mechanically stimulated haematoma matrices retained their elevated pro-angiogenic capacity for 24 h. The pro-angiogenic effect was cancelled by inhibition of VEGFR2 signalling. VEGF concentrations in CM tended to be elevated by mechanical stimulation; this was significant in haematomas from younger, but not from older patients. Other GFs were not mechanically regulated. In conclusion, the paracrine pro-angiogenic capacity of early human haematomas is enhanced by mechanical stimulation. This effect lasts even after removing the mechanical stimulus and appears to be VEGFR2-dependent.

Advancements in orthopedic intervention: retrograde drilling and bone grafting of osteochondral lesions of the knee using magnetic resonance imaging guidance.

Computer-assisted surgery is currently a novel challenge for surgeons and interventional radiologists. Magnetic resonance imaging (MRI)-guided procedures are still evolving. In this experimental study, we describe and assess an innovative passive-navigation method for MRI-guided treatment of osteochondritis dissecans of the knee. A navigation principle using a passive-navigation device was evaluated in six cadaveric knee joint specimens for potential applicability in retrograde drilling and bone grafting of osteochondral lesions using MRI guidance. Feasibility and accuracy were evaluated in an open MRI scanner (1.0 T Philips Panorama HFO MRI System). Interactive MRI navigation allowed precise drilling and bone grafting of osteochondral lesions of the knee. All lesions were hit with an accuracy of 1.86 mm in the coronal plane and 1.4 mm the sagittal plane. Targeting of all lesions was possible with a single drilling. MRI allowed excellent assessment of correct positioning of the cancellous bone cylinder during bone grafting. The navigation device and anatomic structures could be clearly identified and distinguished throughout the entire drilling procedure. MRI-assisted navigation method using a passive navigation device is feasible for the treatment of osteochondral lesions of the knee under MRI guidance and allows precise and safe drilling without exposure to ionizing radiation. This method may be a viable alternative to other navigation principles, especially for pediatric and adolescent patients. This MRI-navigated method is also potentially applicable in many other MRI-guided interventions.

Development of a signal-inducing bone cement for magnetic resonance imaging.

PURPOSE: To develop a signal-inducing bone cement for musculoskeletal procedures in magnetic resonance imaging (MRI). MATERIALS AND METHODS: Acrylic resins were mixed with contrast agents (CAs) and water. We determined the ideal concentration of the components and assessed feasibility in cadaveric bones in an open high-field MR scanner. The contrast-to-noise ratio (CNR) in air and bone was evaluated and mechanical tests were achieved. We determined the amount of water that was not incorporated and measured the amount of CA released with photometric analysis. The cement was analyzed microscopically. RESULTS: Preparation and application of the CA-water-cement compound was feasible and its differentiation in MRI was clear. The maximal CNR(air) had a value of 157.5 (SD 18.3) in an interventional fast T1W turbo-spin echo (TSE) sequence. The compressive strength decreased with the amount of water added. Although nearly 50% of the water added was not incorporated in the cement, the CNR was sufficient for cement detection. The threshold for systemic toxicity of delivered CA was not reached and the microscopic analysis showed water bubbles in the cement. CONCLUSION: A signal-inducing bone cement is feasible for the use in MRI.

A comparison of three scores to screen for delirium on the surgical ward.

BACKGROUND: Postoperative delirium is associated with adverse outcome. The aim of this study was to find a valid and easy-to-use tool to screen for postoperative delirium on the surgical ward. METHODS: Data were collected from 88 patients who underwent elective surgery. Delirium screening was performed daily until the sixth postoperative day using the Confusion Assessment Method (CAM), the Nursing Delirium Screening Scale (Nu-DESC), and the Delirium Detection Score (DDS), and the DSM-IV criteria as the gold standard. RESULTS: Seventeen of 88 patients (19%) developed delirium on at least one of the postoperative days according to the gold standard. The DDS scored positive for 40 (45%) patients, the CAM for 15 (17%), and the Nu-DESC for 28 (32%) patients. Sensitivity and specificity were 0.71 and 0.87 for the DDS, 0.75 and 1.00 for the CAM, and 0.98 and 0.92 for the Nu-DESC. The interrater reliability was 0.83 for the Nu-DESC, 0.77 for the DDS, and 1.00 for the CAM. CONCLUSIONS: All scores showed high specificity but differed in their sensitivity. The Nu-DESC proved to be the most sensitive test for screening for a postoperative delirium on the surgical ward followed by the CAM and DDS when compared to the gold standard.

Passive navigation principle for orthopedic interventions with MR fluoroscopy.

INTRODUCTION: Of late, computer-assisted surgery has become a novel challenge for orthopedic surgeons. However, for orthopedic interventions magnetic resonance (MR) fluoroscopy is in its early stages of development. The authors have developed an innovative passive navigation concept, which is potentially applicable for many magnetic resonance image (MRI)-guided musculoskeletal interventions. With this method, no switching between different planes is required, since the cross-sectional modality of the MRI is used as a new navigation approach. MATERIALS AND METHODS: This method was mainly evaluated in retrograde drilling of artificial osteochondral lesions of the talus as an example of difficult navigation in drill placement due to poor visualization with X-ray and complex anatomy. To accomplish this objective, a passive navigation device was constructed and evaluated in nine cadaveric ankle joint specimens. Feasibility and accuracy of navigated drillings were evaluated. RESULTS: The interactive high-field MR fluoroscopy and the passive aiming device allow precise drilling of osteochondral lesions of the talus, despite the complex anatomy of the ankle. Drillings could be performed with an accuracy of 1.6 mm. The drilling guide was safe and easy to handle. CONCLUSION: The MR-assisted retrograde drilling of osteochondral lesions may enable precise and safe treatment without radiation exposure. This passive navigation technique for MR fluoroscopy is potentially applicable for many orthopedic interventions and may present an alternative to other navigation methods. Especially, the treatment of pediatric and adolescent patients may benefit from the typical MRI properties.

Insight into the molecular pathophysiology of delayed bone healing in a sheep model.

Delayed and nonunions are still challenging problems. In this study, we examined the endogenous mRNA expression of genes regulating cartilage formation, bone formation, endochondral ossification, and bone remodeling during mechanically induced delayed bone healing in a large animal model. A tibial osteotomy was performed in two groups of sheep and stabilized with either a rigid external fixator leading to standard healing or with a rotationally unstable fixator leading to delayed healing. At days 4, 7, 9, 11, 14, 21, and 42 after surgery, total RNA was extracted from the callus. Gene expressions of several molecules functionally important for bone healing were studied by quantitative reverse transcriptase-polymerase chain reaction. The expression profiles were related to callus tissue composition, analyzed by histomorphometry. Histomorphometry demonstrated a delayed, prolonged chondral phase and a reduction in bone formation in the experimental group. There was no differential expression of Runx2 between both groups until day 42, but mRNA expression levels of BMP2, BMP4, BMP7, noggin, Col1a1, IGF1, TGFbeta1, OPN, MMP9, MMP13, TIMP3, TNFalpha, MCSF, RANKL, and OPG were lower in the delayed healing group at several time points. This study provides insight into the temporal periods during which various factors may be deficient during a compromised bone-healing situation.

Osteochondral lesions of the talus: retrograde drilling with high-field-strength MR guidance.

The institutional review board approved the use of cadaveric specimens, and informed consent was obtained from all volunteers. The authors performed and assessed a magnetic resonance (MR)-assisted navigation method for minimally invasive retrograde drilling of talar osteochondral lesions. For this method, a single imaging plane is sufficient for navigation during intervention. To accomplish this objective, a passive MR navigation device was used to evaluate 16 cadaveric ankle joints. Use of this interactive MR-assisted navigation method in combination with a passive aiming device allowed precise and rapid retrograde drilling of talar osteochondral lesions.

Distraction osteogenesis enhances remodeling of remote bones of the skeleton: a pilot study.

Bone injuries have a systemic influence on the remodeling of bone. This effect has not been examined concerning its extent and duration. We measured the systemic effect of distraction osteogenesis on the remodeling of bones of the axial skeleton by means of the mineral apposition rate and bone formation rate in an animal experiment. Distraction osteogenesis was performed on the tibiae of 24 mature Yucatan minipigs. After a 4-day latency period, the tibiae were distracted 2 mm/day for 10 days. The ensuing consolidation phase lasted 10 days. Three fluorescent labeling substances were applied intravenously: calcein green at the second postoperative day, tetracycline 1 day after the end of the distraction phase, and xylene orange 2 days before sacrifice. We prepared ground sections from the ninth right ribs. The mineral apposition rate and bone formation rate were measured histomorphometrically on labeled osteons. The median mineral apposition rate during distraction was 2.39 microm/day (2.12-2.62 microm/day), which was higher than the rate during consolidation (median, 1.62 microm/day; 1.54-1.84 microm/day). The median bone formation rate confirmed this result and was 840.51 microm(2)/day (744.20-1148.26 microm(2)/day) during distraction and 384.25 microm(2)/day (330.84-467.71 microm(2)/day) during consolidation. Thus, a short period of distraction osteogenesis appears to have an anabolic effect on the mineral apposition rate of remote cortical bone.

Differential regulation of blood vessel formation between standard and delayed bone healing.

Blood vessel formation is a prerequisite for bone healing. In this study, we tested the hypothesis that a delay in bone healing is associated with an altered regulation of blood vessel formation. A tibial osteotomy was performed in two groups of sheep and stabilized with either a rigid external fixator leading to standard healing or with a highly rotationally unstable one leading to delayed healing. At days 4, 7, 9, 11, 14, 21, and 42 after surgery, total RNA was extracted from the callus. Gene expressions of vWF, an endothelial cell marker, and of several molecules related to blood vessel formation were studied by qPCR. Furthermore, histology was performed on fracture hematoma and callus sections. Histologically, the first blood vessels were detected at day 7 in both groups. mRNA expression levels of vWF, Ang1, Ang2, VEGF, CYR61, FGF2, MMP2, and TIMP1 were distinctly lower in the delayed compared to the standard healing group at several time points. Based on differential expression patterns, days 7 and 21 postoperatively were revealed to be essential time points for vascularization of the ovine fracture callus. This work demonstrates for the first time a differential regulation of blood vessel formation between standard and mechanically induced delayed healing in a sheep osteotomy model.

Locally applied osteogenic predifferentiated progenitor cells are more effective than undifferentiated mesenchymal stem cells in the treatment of delayed bone healing.

Mesenchymal stem cells (MSCs) and osteogenic predifferentiated cells (OPCs) have been shown to promote healing of critical-sized bone defects. This study investigated the regenerative capacity of autologous MSCs versus OPCs after local injection into a compromised bone healing situation. We hypothesized that treatment with MSCs and OPCs would enhance the healing and that the MSCs would be more effective due to their lower differentiation and higher proliferative competence. The femur of rats was osteotomized and stabilized with an external fixator. Except for the control group (C group), in all animals a delayed healing was induced by cautering the periosteum and removing the bone marrow. Two days postsurgery, autologous MSCs (MSC group), OPCs (OPC group), or cell-free medium (Sham group) was percutaneously injected into the osteotomy gap. The C group received no treatment. Bone healing was evaluated radiologically, biomechanically, and histologically. After 8 weeks, the C group showed complete bony bridging, while a delayed healing was detected in the Sham group. All outcome measures showed better healing of the OPC group compared to the Sham group. Contrary to our expectations, there were no significant differences in outcome measures between the MSC group and the Sham group. The percutaneous injection of OPCs could become a minimally invasive treatment option for delayed or nonunions.

Tibia fracture following removal of the ETN (Expert Tibia Nail): a case report.

We report on a patient who sustained a fracture of the tibial shaft during the removal of the newest type of an intramedullary nail (Expert Tibia Nail, Synthes. In this case report, we discuss the causes of this complication and possible ways to prevent this.

Mechanical induction of critically delayed bone healing in sheep: radiological and biomechanical results.

This study aimed to mechanically produce a standardized ovine model for a critically delayed bone union. A tibial osteotomy was stabilized with either a rigid (group I) or mechanically critical (group II) external fixator in sheep. Interfragmentary movements and ground reaction forces were monitored throughout the healing period of 9 weeks. After sacrifice at 6 weeks, 9 weeks and 6 months, radiographs were taken and the tibiae were examined mechanically. Interfragmentary movements were considerably larger in group II throughout the healing period. Unlike group I, the operated limb in group II did not return to full weight bearing during the treatment period. Radiographic and mechanical observations showed significantly inferior bone healing in group II at 6 and 9 weeks compared to group I. After 6 months, five sheep treated with the critical fixator showed radiological bridging of the osteotomy, but the biomechanical strength of the repair was still inferior to group I at 9 weeks. The remaining three animals had even developed a hypertrophic non-union. In this study, mechanical instability was employed to induce a critically delayed healing model in sheep. In some cases, this approach even led to the development of a hypertrophic non-union. The mechanical induction of critical bone healing using an external fixation device is a reasonable attempt to investigate the patho-physiological healing cascade without suffering from any biological intervention. Therefore, the presented ovine model provides the basis for a comparative evaluation of mechanisms controlling delayed and standard bone healing.