Deletion of Tfam in Prx1-Cre expressing limb mesenchyme results in spontaneous bone fractures.

INTRODUCTION: Osteoblasts require substantial amounts of energy to synthesize the bone matrix and coordinate skeleton mineralization. This study analyzed the effects of mitochondrial dysfunction on bone formation, nano-organization of collagen and apatite, and the resultant mechanical function in mouse limbs. MATERIALS AND METHODS: Limb mesenchyme-specific Tfam knockout (Tfamf/f;Prx1-Cre: Tfam-cKO) mice were analyzed morphologically and histologically, and gene expressions in the limb bones were assessed by in situ hybridization, qPCR, and RNA sequencing (RNA-seq). Moreover, we analyzed the mitochondrial function of osteoblasts in Tfam-cKO mice using mitochondrial membrane potential assay and transmission electron microscopy (TEM). We investigated the pathogenesis of spontaneous bone fractures using immunohistochemical analysis, TEM, birefringence analyzer, microbeam X-ray diffractometer and nanoindentation. RESULTS: Forelimbs in Tfam-cKO mice were significantly shortened from birth, and spontaneous fractures occurred after birth, resulting in severe limb deformities. Histological and RNA-seq analyses showed that bone hypoplasia with a decrease in matrix mineralization was apparent, and the expression of type I collagen and osteocalcin was decreased in osteoblasts of Tfam-cKO mice, although Runx2 expression was unchanged. Decreased type I collagen deposition and mineralization in the matrix of limb bones in Tfam-cKO mice were associated with marked mitochondrial dysfunction. Tfam-cKO mice bone showed a significantly lower Young's modulus and hardness due to poor apatite orientation which is resulted from decreased osteocalcin expression. CONCLUSION: Mice with limb mesenchyme-specific Tfam deletions exhibited spontaneous limb bone fractures, resulting in severe limb deformities. Bone fragility was caused by poor apatite orientation owing to impaired osteoblast differentiation and maturation.

Spontaneous morphological remodelling of the O-C1 joint after posterior fusion for occipitocervical dislocation.

BACKGROUND: Traumatic occipitocervical dislocation (OCD) occurs due to fatal high-energy injury. Modern screw-based constructs enable successful reduction and stabilisation. In view of this, there are no previous reports on the spontaneous remodelling of the O-C1 joint after posterior fusion. We report the first case of postoperative spontaneous remodelling and stabilisation of the O-C1 joint after traumatic OCD.Case description: A 9-year-old girl suffered from traumatic OCD, accompanied by complete rupture of the O-C1-C2 ligamentous complex. Halo-vest fixation, and subsequently posterior fusion surgery from the occipital bone to C2, with autologous iliac crest bone graft and an allograft were performed. However, we could not achieve complete reduction of the O-C1 joint during surgery owing to extremely severe instability.Postoperative X-ray and computed tomography scan showed incomplete reduction of the O-C1 joint. Insufficient congruity of the O-C1 joint persisted. Afterwards, gradual spontaneous remodelling of the O-C1 joint occurred, both anteriorly and posteriorly 3 months postoperatively. Solid union was achieved 6 months postoperatively. Two years later, bilateral O-C1 joints in the patient were completely reformed and restabilised by incredible vigorous remodelling. Insufficient reduction and persisting poor joint congruence after surgery for OCD was probably restabilised by further spontaneous remodelling of articular morphology in such a young patient. CONCLUSIONS: Postoperative spontaneous remodelling of the O-C1 joint after posterior reconstruction for OCD may occur in young patients. Incomplete reduction of the O-C1 joint during surgery may be acceptable due to the possibility of postoperative bone remodelling and restabilisation.

The Incidence of Heterotopic Ossification in Surgically and Non-surgically Treated Elbow Fractures at a Municipal Hospital in Japan.

Background: Heterotopic ossification (HO) is a well-recognised complication of after elbow trauma. The prevalence and risk factors of HO have been previously reported. However, these reports were based on elbow trauma that had undergone surgical treatment and most of them were from Western countries. This study aimed to assess the incidence of HO in patients with elbow fractures who were treated surgically and non-surgically in Japan. Methods: We retrospectively identified consecutive patients who were treated of elbow fractures and fracture-dislocations at our institution in recent consecutive 3-year periods. We extracted patient demographics, injury mechanisms and treatment details from the medical records. Furthermore, we reviewed radiographs to classify the fracture pattern and identify the presence or absence of HO. Results: HO was identified in 6/97 (6%) patients. Fracture-dislocation was noted in 4/6 patients. The fracture types with HO included terrible triad injury (n = 2), isolated coronoid process fractures (n = 2), distal humerus A-type fractures (n = 1) and radial head fracture (n = 1). According to the Hastings and Graham classification, HO was classified as Class I in five patients and Class II B in one patient who underwent additional surgery for HO resection. Conclusions: The incidence of HO was relatively low in our patients. However, of the 20 conservatively treated elbows, one patient developed clinically relevant HO and required excision of HO. Even patients with elbow fractures treated conservatively should be informed of the potential risk of developing severe HO requiring surgical excision. In addition, surgeons in this region could use these data to inform patients about the risk of HO development after an elbow injury. Level of Evidence: Level IV (Therapeutic).

Is "Trigonum sacrale" a real equilateral triangle? Anatomic consideration of sacral hiatus in adult: A three-dimensional CT study for reliable caudal access.

This study is the first attempt to examine anatomical characteristics using three-dimensional computed tomography (3DCT) bone images with some parameters, in order to achieve correct and uncomplicated accesses. In addition, the study addresses a long-standing problem in the field and evaluates whether the trigonum sacrale forms an equilateral triangle or not. A detailed anatomic study of the sacral region was carried out on 91 patient 3DCT images. The CT data, in DICOM format, was read into VINCENT software from Fuji Film, with a slice thickness of 0.5 mm. The average length of sacral hiatus was 28.6 ±â€…8.4 (range 13.8-45.2 mm). The average width of sacral hiatus at the level of sacral cornua was 10.9 ±â€…2.7 (range 3.8-16.5 mm). The ratio between the length of the oblique and base line formed by the sacral triangle was 0.81 ±â€…0.12 (range 0.54-1.00). Using 3DCT images translated by the volume rendering technique, we can remove soft tissue from bones virtually. A slice thickness of 0.5 mm makes it a fine image, and permits meticulous measurement, which is different from previous cadaveric studies. Interestingly, our data showed that the ratio between oblique and base line on sacral triangle was <1.0, average 0.81. Findings demonstrated that the trigonum sacrale is not an equilateral triangle. This is useful information for the identification of the sacral hiatus when the landmark-based technique is employed.