The role of the epiphyseal and metaphyseal circulations on longitudinal growth in the dog: an experimental study

Total hip reconstruction after sarcoma resection in children with a free vascularized fibula without osteotomy of the bone flap: Technique description and case series

BACKGROUND

Hip joint reconstruction following intra-articular resection of the femoral head in children is a highly demanding challenge. We aimed to describe the outcomes of hip reconstruction in paediatric patients with a free fibular epiphyso-diaphyseal flap based on both anterior tibial and peroneal vessels within a radius allograft.

PATIENTS AND METHODS

Four patients underwent hip reconstruction following this technique between 2013 and 2020 at La Paz University Hospital (Madrid, Spain). The postoperative follow-up period ranged between 12 months and seven years. Two of the patients were diagnosed with Ewing's sarcoma and two with osteosarcoma. The median age at the time of surgery was eight years (six to nine).

RESULTS

Three patients remained to be disease-free at the time of this study, and one died shortly after surgery, so he was excluded from the reconstruction analysis of results. No postoperative complications requiring reintervention were recorded. Imaging studies (X-ray and MRI) showed three-dimensional growth of the flap and integration of the allograft. Mean leg length discrepancy was 1.3 cm (0 to 2.3). At the last follow-up visit, all patients were able to ambulate.

CONCLUSION

For children following oncological resection of the femoral head, reconstruction with a vascularized epiphyso-diaphyseal fibula flap combined with radius allograft is a safe option. This procedure provides encouraging functional results and avoids the complications of previously published techniques or implants.

Polygenic risk for Alzheimer's disease shapes hippocampal scene-selectivity

Preclinical models of Alzheimer's disease (AD) suggest APOE modulates brain function in structures vulnerable to AD pathophysiology. However, genome-wide association studies now demonstrate that AD risk is shaped by a broader polygenic architecture, estimated via polygenic risk scoring (AD-PRS). Despite this breakthrough, the effect of AD-PRS on brain function in young individuals remains unknown. In a large sample (N = 608) of young, asymptomatic individuals, we measure the impact of both (i) APOE and (ii) AD-PRS on a vulnerable cortico-limbic scene-processing network heavily implicated in AD pathophysiology. Integrity of this network, which includes the hippocampus (HC), is fundamental for maintaining cognitive function during ageing. We show that AD-PRS, not APOE, selectively influences activity within the HC in response to scenes, while other perceptual nodes remained intact. This work highlights the impact of polygenic contributions to brain function beyond APOE, which could aid potential therapeutic/interventional strategies in the detection and prevention of AD.

Long-term results of vascularized proximal fibula epiphyseal transfer based on the anterior tibial artery in retrograde fashion

Injury of bone growth plates can result in severe disability in children. We report the long-term results of successful vascularized proximal fibula epiphyseal transfer based on the anterior tibial artery in retrograde fashion.

Double-barrel vascularized dual fibula transfer with epiphyseal growth plate for hip reconstruction: A case report

We present a case report of a 10-year-old girl diagnosed with Ewing sarcoma treated with intra-articular wide resection of the right femur and reconstruction with a series-connected double-barrel bilateral vascularized fibula graft (db-BVFG), including fibular head for articulation with the acetabulum of the pelvic bone and preservation of the epiphyseal growth plates for eventual limb growth. No postoperative complications were observed and bone union was achieved with fibular graft hypertrophy, allowing for full weight bearing. Neither local recurrence nor metastasis was observed at 17-year follow-up. Range of motion degrees at last follow up: hip flexion 90 degree, extension 12 degree, abduction 31 degree, rotation 25 degree. Right versus left limb discrepancy was 60 mm. Db-BVFG may be an option for reconstruction of long femoral defects and hip joint restoration following tumor resection and inclusion of epiphysis within the graft is a viable option in pediatric patients to restore longitudinal growth of the reconstructed long bone.

Environmental temperature impact on bone and cartilage growth

Environmental temperature can have a surprising impact on extremity growth in homeotherms, but the underlying mechanisms have remained elusive for over a century. Limbs of animals raised at warm ambient temperature are significantly and permanently longer than those of littermates housed at cooler temperature. These remarkably consistent lab results closely resemble the ecogeographical tenet described by Allen's "extremity size rule," that appendage length correlates with temperature and latitude. This phenotypic growth plasticity could have adaptive significance for thermal physiology. Shortened extremities help retain body heat in cold environments by decreasing surface area for potential heat loss. Homeotherms have evolved complex mechanisms to maintain tightly regulated internal temperatures in challenging environments, including "facultative extremity heterothermy" in which limb temperatures can parallel ambient. Environmental modulation of tissue temperature can have direct and immediate consequences on cell proliferation, metabolism, matrix production, and mineralization in cartilage. Temperature can also indirectly influence cartilage growth by modulating circulating levels and delivery routes of essential hormones and paracrine regulators. Using an integrated approach, this article synthesizes classic studies with new data that shed light on the basis and significance of this enigmatic growth phenomenon and its relevance for treating human bone elongation disorders. Discussion centers on the vasculature as a gateway to understanding the complex interconnection between direct (local) and indirect (systemic) mechanisms of temperature-enhanced bone lengthening. Recent advances in imaging modalities that enable the dynamic study of cartilage growth plates in vivo will be key to elucidating fundamental physiological mechanisms of long bone growth regulation.

Associations between arterial oxygen saturation, body size and limb measurements among high-altitude Andean children

Objectives

The relative influences of hypoxia and other environmental stressors on growth at altitude remain unclear. Previous work demonstrated an association between peripheral arterial oxygen saturation (S_pO₂) and anthropometry (especially tibia length) among Tibetan and Han children at altitude. We investigated whether similar associations exist among Andeans, and the patterning of associations between S_pO₂ and anthropometry.

Methods

Stature, head-trunk height, total upper and lower limb lengths, zeugopod (ulna and tibia) and autopod (hand and foot) lengths were measured in Peruvian children (0.5–14 years) living at >3000 m altitude. S_pO₂ was measured by pulse oximetry. Anthropometry was converted to internal z scores. Correlation and multiple regression were used to examine associations between anthropometry z scores and S_pO₂, altitude, or S_pO₂ adjusted for altitude since altitude is a major determinant of variation in S_pO₂.

Results

S_pO₂ and altitude show weak, significant correlations with zeugopod length z scores and still weaker significant correlations with total upper and lower limb length z scores. Correlations with z scores for stature, head-trunk height, or autopod lengths are not significant. Adjusted for altitude, there is no significant association between anthropometry and S_pO₂.

Conclusions

Associations between S_pO₂ or altitude and total limb and zeugopod length z scores exist among Andean children. However, the relationships are relatively weak, and while the relationship between anthropometry and altitude may be partly mediated by S_pO_2, other factors that covary with altitude (e.g., socioeconomic status, health) are likely to influence anthropometry. The results support suggestions that zeugopod lengths are particularly sensitive to environmental stressors. Am. J. Hum. Biol., 25:629–636, 2013. © 2013 Wiley Periodicals, Inc.

Exercise mitigates the stunting effect of cold temperature on limb elongation in mice by increasing solute delivery to the growth plate

Ambient temperature and physical activity modulate bone elongation in mammals, but mechanisms underlying this plasticity are a century-old enigma. Longitudinal bone growth occurs in cartilaginous plates, which receive nutritional support via delivery of solutes from the vasculature. We tested the hypothesis that chronic exercise and warm temperature promote bone lengthening by increasing solute delivery to the growth plate, measured in real time using in vivo multiphoton microscopy. We housed 68 weanling female mice at cold (16°C) or warm (25°C) temperatures and allowed some groups voluntary access to a running wheel. We show that exercise mitigates the stunting effect of cold temperature on limb elongation after 11 days of wheel running. All runners had significantly lengthened limbs, regardless of temperature, while nonrunning mice had shorter limbs that correlated with housing temperature. Tail length was impacted only by temperature, indicating that the exercise effect was localized to limb bones and was not a systemic endocrine reaction. In vivo multiphoton imaging of fluoresceinated tracers revealed enhanced solute delivery to tibial growth plates in wheel-running mice, measured under anesthesia at rest. There was a minimal effect of rearing temperature on solute delivery when measured at an intermediate room temperature (20°C), suggesting that a lasting increase in solute delivery is an important factor in exercise-mediated limb lengthening but may not play a role in temperature-mediated limb lengthening. These results are relevant to the study of skeletal evolution in mammals from varying environments and have the potential to fundamentally advance our understanding of bone elongation processes.

Soluble VEGF isoforms are essential for establishing epiphyseal vascularization and regulating chondrocyte development and survival

VEGF is crucial for metaphyseal bone vascularization. In contrast, the angiogenic factors required for vascularization of epiphyseal cartilage are unknown, although this represents a developmentally and clinically important aspect of bone growth. The VEGF gene is alternatively transcribed into VEGF(120), VEGF(164), and VEGF(188) isoforms that differ in matrix association and receptor binding. Their role in bone development was studied in mice expressing single isoforms. Here we report that expression of only VEGF(164) or only VEGF(188) (in VEGF(188/188) mice) was sufficient for metaphyseal development. VEGF(188/188) mice, however, showed dwarfism, disrupted development of growth plates and secondary ossification centers, and knee joint dysplasia. This phenotype was at least partly due to impaired vascularization surrounding the epiphysis, resulting in ectopically increased hypoxia and massive chondrocyte apoptosis in the interior of the epiphyseal cartilage. In addition to the vascular defect, we provide in vitro evidence that the VEGF(188) isoform alone is also insufficient to regulate chondrocyte proliferation and survival responses to hypoxia. Consistent herewith, chondrocytes in or close to the hypoxic zone in VEGF(188/188) mice showed increased proliferation and decreased differentiation. These findings indicate that the insoluble VEGF(188) isoform is insufficient for establishing epiphyseal vascularization and regulating cartilage development during endochondral bone formation.

Reconstruction of the lateral malleolus using a reverse-flow vascularized fibular head: a case report

We report a case of a 7-year-old girl in whom a vascularized fibular head with preserved epiphyseal and metaphyseal blood supply was used to reconstruct the missing lateral malleolus. Two-year follow-up showed good bony stability and growth potential of the transplanted epiphyseal plate.

Use of free scapular crest flap in pediatric epiphyseal reconstructive procedures

Studies have been underway since 1981 on the scapular anatomic unit as a new donor site for reconstructive surgery. Anatomic studies have proven that this diaphyseal bone has a large osteocartilaginous growth epiphysis at its inferior pole, which is responsible for development of 80% of the surface of the scapula. Experimental investigations and clinical studies have revealed minimal functional limitation because of loss of the scapular crest and that its growth plate can be used beneficially for vascularized bone transfer. Four cases are reported with good results based on 2 to 14 years followup without significant impairment of the donor site.

Vascularized Fibular Epiphyseal Transplantation for Limb Salvage Following Bone Tumour Excision

Vascularized fibular transplantation has found wide application for long bone reconstruction in both congenital and acquired defects. However, in children the growth of these transplants is limited and requires the epiphysis if it is to be substantial. Also, the reconstruction of a joint is best achieved with autologus hyaline cartilage. Vascularized fibular epiphyseal transplantation, thus, may play a role in limb salvage procedures in children to both preserve joint function and facilitate long bone growth. The present paper discusses the history of vascularized epiphyseal transplantation both in the laboratory and clinical realm. In discussing its advantages and associated problems, special emphasis is directed at the vascular factors, the endocrine environment, the innervation, mechanical stressors, the recipient site and the donor site. Two case examples are presented to demonstrate the technique, the results and the long term outcome.

Effect of ischemia and three different perfusion solutions on the rabbit epiphyseal growth plate

An isolated vascularized knee joint model was used (1) to determine the minimum ischemia time that produced growth retarding damage to the epiphyseal plate and (2) to evaluate whether intra-arterial perfusion could reduce the ischemia damage. Experiment 1 consisted of 31 rabbits in 5 groups: 0, 2,4,6, and 8 hr of warm ischemia produced by clamping the pedicle. Experiment 2 consisted of 18 rabbits in which 10 ml of one of (1) Euro-Collins, (2) University of Wisconsin solution, or (3) heparinized blood were perfused through the joint without ischemia. Experiment 3 consisted of 21 rabbits in which one of the three solutions was perfused for a short period during 6 hr of ischemia. Growth of the tibia was followed radiographically every month over 3 months, and the growth plates were evaluated histologically after sacrifice. Results showed that at least 6 hr of ischemia was needed before longitudinal growth was reduced; less ischemia time caused overgrowth. Histologic damage was found in all animals to some degree. Perfusion alone without ischemia had no detrimental effect on growth or histology. The growth reduction at 6 hr of ischemia was minimized by perfusion with every solution. Heparinized blood was the most effective and Euro-collins was the least effective.

Epiphyseal plate transplantation: an historical review

Non-vascularized and vascularized transplantation of epiphyseal plate autografts have been performed both clinically and experimentally for over 100 years. However, the ultimate clinical goal of vascularized transplantation of epiphyseal plate allografts for paediatric extremity reconstruction remains elusive, due primarily to the lack of suitably nontoxic techniques to prevent graft rejection. We have summarized the published clinical and experimental investigations of vascularized epiphyseal plate transplantation, and organized the experiments and clinical operations into four main groups: (1) local vascular studies on unmanipulated epiphyseal plates, (2) studies of epiphyseal plate behaviour after orthotopic replantation, (3) studies of epiphyseal plate behaviour after heterotopic transplantation, and (4) studies of epiphyseal plate behaviour after allograft transplantation. Prior investigations into the non-vascularized transplantation of epiphyseal plate autografts and allografts are presented as background. These groups of studies serve as the building blocks for the more clinically applicable experimental investigations outlined in the final section of this review.

Bernard O'Brien: the microsurgical transfer of immature bone

Bernard O'Brien was one of the pioneers of vascularized epiphyseal plate transfer. His clear understanding of the wide array of potential applications for reconstructive microsurgery stimulated his interest in the transfer of growing long bones. Investigations have been carried out in his laboratory since the earliest days of skeletal free tissue transfers. This paper describes the work done with epiphyseal plate transfers in O'Brien's laboratory. Research from other centers is then reviewed. Finally, the experience with clinical application is described.

Free and island vascularized joint transfer for proximal interphalangeal reconstruction: a series of 27 cases

Twenty-seven vascularized joints were transferred in 26 patients for proximal interphalangeal joint reconstruction: 7 heterodigital island, 7 homodigital island (distal to proximal interphalangeal), 2 free heterodigital, and 11 free second toe proximal interphalangeal. With a mean follow-up period of 37 months, mean active range of motion of heterodigital island joint was 56 degrees (mean extensor lag, 21 degrees), excepting one failure ending with an arthrodesis. Four complications occurred in the homodigital island joint series: one sepsis, one nail dystrophy, one failed distal arthrodesis, and one bone abutment in flexion. Excluding the sepsis, mean active final range of motion was 52 degrees after a mean follow-up period of 18 months. The two free heterodigital joints had 80 degrees and 65 degrees of motion. The worst results occurred in the free second toe proximal interphalangeal joints transferred, with a mean active range of motion of 33 degrees (mean extension lag 39 degrees). The main advantages of these techniques are a compound tissue transfer, rapid bone healing, good lateral stability, growth potential, and long-term cartilage preservation.

Heterotopic vascularized growth plate transfer in juvenile dogs

Prior animal studies of vascularized epiphyseal transfers placed growth plates in 2 bone systems where the independent growth of epiphyses and their response to altered stresses has been difficult to assess. This study assessed growth of vascularized ulnar epiphyses transferred to the ipsilateral humerus of 12-week-old puppies. Growth was permitted by a specially designed extensible plate. Control groups showed that humeral dissection, osteotomy and ostectomy alone do not stimulate growth. In 4 puppies initial growth of the transferred epiphysis was seen but late collapse and formation of bridging callus occurred so that overall humeral length at maturity was not significantly different from control humeri. Physical forces inherent in heterotopic transfer may preclude long term growth of transferred epiphyses particularly in sites of higher relative load. The extensible plate used here may be a useful device in the fixation of transferred epiphyses with growth potential.

Free vascularized whole joint transfer in children

Reconstruction of the traumatized finger joint with epiphyseal destruction has long been problematic. Since free vascularized whole joint transfer was introduced as a treatment for joint and epiphyseal destruction, this procedure has been selected as an alternative treatment because it may provide a growing epiphysis. We have reviewed our series of 19 joint transfers. Mean age at operation was 6.2 years (range 3 to 12). Average active range of motion was 31 degrees/61 degrees for the group with posttraumatic reconstruction (n = 12) and 21 degrees/43 degrees for the group with reconstruction of a congenital deformity (n = 7), with an overall average of 27 degrees/54 degrees. Average range of motion following transfer of an metatarsophalangeal (MTP) or metacarpophalangeal (MCP) joint to an MCP joint position was 39 degrees/75 degrees (n = 4); proximal interphalangeal (PIP) to PIP transfer was 22 degrees/39 degrees (n = 13); and PIP to MCP transfer was 38 degrees/51 degrees (n = 2). The proximal phalanges in MCP joints transferred to the MCP position grew an average of 7.0 mm, and the middle phalanges of joints transferred to the PIP position grew 4.3 mm. Almost normal growth was observed in all transferred joints except two that showed premature epiphyseal closure. Indications for this procedure and techniques to improve range of motion are described.

Free Vascularised Epiphyseal Transplantation in Upper Extremity Reconstruction

We describe preliminary observations on the use of free vascularised transfer of proximal fibular epiphysis in replacement of proximal humeral epiphysis or distal radial epiphysis in three patients. An analysis of the early results shows evidence of longitudinal growth, graft hypertrophy and epiphyseal adaptation in transplanted epiphysis. A review of the problems in this type of surgery is included.