Tuesday, October 16, 2012

Bony Bridge and Growth Arrest

Bony Bridges are a model of LSJL driven bone growth.  It's unrealistic to assume that LSJL can cause the spontaneous regeneration of the growth plate at once.  A more reliastic model is to assume that LSJL forms mini-growth plates and these growth plates results in angular growth but also longitudinal growth that eventually stabilizes as the growth plates acquire a more normal distribution.

I have included many fragments here that I was not able to get full studies on but I've included this stub as it is important to the mechanism of LSJL action.  Please help if you can.  Studies with exclamation points definitely need full studies for. There are two studies that show that bone growth can occur despite partial closure via osseous bridge and that the bone can spontaneously correct itself.

This leads weight to the view that LSJL will induce mini growth plates that individually induce angular growth but over time the growth plates will lead to uniform longitudinal growth.

[Osseous bridge after physeal-injury to the distal tibia with spontaneous resolution].!

"The risk of osseous bridge development after certain types of physeal injury is well established. Once formed, the bridge continues to grow and results in a progressive deformity. The authors present an unusual case of a five-year-old girl who had a Salter-Harris Type-IV fracture of the distal tibial epiphyseal plate, with subsequent osseous bridge formation and deformity development. The bridge resolved spontaneously in 16 months, and joint mechanical axis alignment was gradually restored with normal growth of the distal tibia."

"If the bridge is large and centrally located in the physis, growth is slowed or stopped and limb shortening results."<-In the center of the physis and not at the ends of the physis where we're worried about being able to induce growth with LSJL.

"If the bridge is small but peripheral, growth is tethered and angular deformity develops."

"Peripheral bone bridges in the distal tibia frequently caused angular deformity and, not surprisingly, were strongly associated with tethered growth recovery lines. Growth recovery lines, also called Park or Harris lines, represent disks of transversely oriented, rather than the normal longitudinally oriented, bony trabecula. These disks form at the physis during slowed growth because of injury, immobilization, or illness. As growth resumes, the physis migrates away from the line that remains in the metaphysis. A growth recovery line angled relative to the physis indicates tethering of physeal migration by a bony bridge "

"Cartilage persists in the metaphysis when enchondral ossification is disrupted as the result of metaphyseal vascular disruption"

"If the growth plate is affected eccentrically, tethering will cause angular deformity. If the growth plate is affected centrally, growth at the periphery causes cupping of the metaphysis with shortening of the bone"

"portions of cartilage from the growth plate become fixed in the metaphysis [after growth plate trauma] while growth of bone continues. This results in several patterns: deep intrusions of the growth plate into the metaphysis, persistence of a band of cartilage in the metaphysis, or widening and irregularity of the growth plate. Small islands of cartilage may also be trapped in the epiphysis"

Growth arrest of the distal radius following a metaphyseal fracture: case report and review of the literature.

"five reported case of distal radial metaphyseal fractures not invloving the physis leading to growth arrest."

Fracture through a Harris growth arrest line: a case report.

Spontaneous correction of partial physeal arrest: report of a case and review of the literature.!

"This study describes the rare phenomenon of partial physeal arrest spontaneous correction. It concerns a case of a 3.5-year-old girl who suffered from a Salter-Harris IV fracture of the distal tibial epiphysis, which was managed conservatively. After fracture healing an osseous bridge was formed at the medial part of the physis, leading to a varus deformity. The parents refused the operation, but 6 years later, both the ankle's deformity and the shortening of the extremity had been spontaneously corrected. It seems that the growth potential of the physis healthy portion is able to break the already transformed osseous bridge."

18F-FDG uptake in metaphyseal growth arrest lines: a case study.

"Growth arrest lines (also referred to as Harris lines) refer to dense metaphyseal trabecular lines, perpendicular to the long axis of the bone. The phenomenon is seen only in patients with immature skeletal structure after periods of nutritional insufficiency, illness, and prolonged immobilization or bisphosphonates administration during which bone growth is inhibited. With resumption of bone growth, a dense trabecular line becomes visible, typically at the metaphyses of rapidly growing long bone."

18F-FDG is a supstance used for imaging.

"Over time, the growth arrest lines migrate toward the diaphysis as bone growth continues at the physes."

"Bone scan 2 years after treatment with chemotherapy and bisphosphonate demonstrating symmetrical band of increased MDP uptake immediately proximal to the femoral physes representing the initial migration of growth arrest lines proximally"

Continued Growth After Limited Physeal Bridging.

"After any physeal injury, the primary concern is the possibility of some pattern of growth alteration, particularly transphyseal bridging that may cause lasting deformities and impact subsequent patient care. Small areas of physeal bridging, however, may be associated with continued growth, rather than impairment.{this may give us an idea of how much a growth plate has to be open in order to grow}
Seven patients with small central physeal bridges of the distal femur were identified. 
Radiography identified small, relatively centrally located transphyseal osseous bridging that was associated with a linear (longitudinal) region of osseous density extending from the physeal bridge proximally into the metaphysis. This linear striation disappeared at the metaphyseal/diaphyseal gradation, an area of progression proximally from metaphysis to diaphysis. Only 1 patient had a significant leg length inequality. Magnetic resonance imaging confirmed the intrametaphyseal linear sclerotic bone and its disappearance with diaphyseal remodeling.
Small, central transphyseal osseous bridges may form after radiologically confirmed acute physeal injury. Normal physiological (hydrostatic) growth forces can be sufficient to overcome such limited central bridging and allow continued, essentially normal, longitudinal growth."

The scientists state that an unobstructed region of the Zone of Ranvier is essential for normal longitudinal growth.  The Zone of Ranvier is the groove that provides resting zone cells into the growth plate.

The growth plate
"The zone of Ranvier consists of cells lying laterally and circumferential around the upper zones of the physis whose responsibility it is to provide latitudinal growth of the physis and thereby provide for a wider bone at the level of the growth plate."

Towards a better understanding of bone bridge formation in the growth plate - an immunohistochemical approach.

"From the clinical experience it is known that in some patients this bone bridge eventually disappears during the growth process.  The aim of this study was to investigate the spatial and temporal protein level of molecules potentially involved in these processes, i.e. RANKL, OPG, DKK-1, Coll 10, BMP-2 and IL-6, in an experimental rat model using an immunohistochemical approach. The results from our study suggest that bone bridge formation might be an early event starting immediately after growth plate injury and involving several pro-osteoblastic molecules, i.e. IL-6, BMP-2 as well as OPG and Coll X. In the late studied time points 3 and 9 month post injury expression of anti-osteoblastic proteins, i.e. DKK1 and RANKL, was increased. This indicates that bone bridge dissolution might be late event and potentially linked to WNT signaling inhibition and RANK/RANKL signaling activation."

Couldn't get full study yet.

1 comment:

  1. wheres the easy to understand summaries gone...