Posterolateral spinal fusion (PSLSF) in rabbits is a challenging model for bone substitutes because the transverse processes are extremely thin and the space to be filled with bone is greater than critical and meiopragic in terms of vascularity.

Several investigators have shown beneficial effects of PRP in bone and soft-tissue healing processes. However, controversial results have been reported in clinical setting analysing the effectiveness of PRP. Aim of the present study was to test the effectiveness of PRP in experimental model of PLSF in rabbits.

A particular pattern of complex instability of the elbow is “the terrible triad”, in which elbow dislocation is associated with fractures of the coronoid and radial head. Other frequent patterns are the variant of Monteggia lesions (Bado II) described by Jupiter which is characterized by ulnar fracture associated with fracture-dislocation of proximal radius, and the articular fracture of the distal humerus associated with elbow dislocation. The goal of treatment is to restore the primary stabilizers of the elbow such as the coronoid process, olecranon and both collateral ligaments by internal fixation and reconstruction of the ligaments. If elbow stability obtained at operation is unsatisfactory or internal fixation not enough stable, there an indication for applying a dynamic external fixator (DEF). The latter allows:

the articular congruence to be maintained and the ligaments to heal in adequate tension and position,

From 2005 to 2008, we treated surgically 31 patients with complex instability of the elbow. DEF was applied in 38% of cases, namely 3 terrible triads, 5 fracture-dislocations of Monteggia and 4 articular fractures of the humerus associated with elbow dislocation. The mean age of patients was 44 years (range 30–74). All patients underwent ORIF, reconstruction of ligaments and dynamic external fixation. The OptiROM elbow fixator was used In 2 patients, the Orthofix fixator in 1 and the DJD fixator in 9. In all cases, active elbow motion was allowed without restrictions from the second postoperative day. Indomethacin was consistently administered for 5 weeks to prevent heterotopic ossifications. The DEF was removed after 6 weeks. The mean follow-up was 25 months (range 5–44 months). At last follow-up, the clinical results, evaluated according to the MEPS, were excellent in 10 patients (83%), who had had a fast recovery of range of motion (ROM). The elbow was painless in all patients and stable in all but 1. Moderate osteoarthrosis was found in 60% of cases. Complications included: 1 elbow stiffness, 1 pseudarthrosis of capitulum humeri and trochlea, 1 transitory radial nerve palsy, and 1 superficial pin tract infection.

In conclusion, DEF is a helpful tool for treatment of complex elbow instability, particularly when stable internal fixation cannot be obtained or instability persists after ligaments reconstruction. However, DEF increases morbidity, and implies a longer operative time and prolonged exposure to radiation.

Purpose: Treatment of radial head fractures of Mason Type II and III involving the neck of the radius is still controversial, especially in the presence of comminution. ORIF often gives unsatisfactory results because of the difficulty in restoring the head-neck off-set and the radial head inclination relative to its neck. In these cases radial head replacement may be indicated ; however, there are no long-term studies on complications and survival of the implant. Recently precontoured plates for the proximal radius has been introduced but no trials have determined whether they are able to restore the normal anatomy of the radius. The latter is still partially unknown because no studies have analyzed the morphology of posterolateral aspect of radial head and neck (“safe zone”). Our study was aimed at:

determining the possible presence of anatomical variations of the safe-zone and

Material and Methods: Measurements, performed on 44 cadaver dry radii of adults, included: length of the radius, diameters and height of the radial head, and height and diameter of the neck of the radius. The radius of bending of the safe zone was also calculated.

Results: The morphological evaluation of the “safe zone” of the radius revealed 3 different morphological types of this zone:

(flat) (25 %),

Adherence of a precoundered plate (Acumed) to the bone surface of the safe zone was performed independently by three of us, and the gap between plate and bone was measured. Plate adaptability was good in Type B, scarce in Type C and absent in Type A.

Conclusion: In conclusion, we identified 3 different morphologies of the safe zone, not previously described, and we found that the precountered plates now available can ensure a good restoration of anatomy only in the half of the human radii.

Aims: Aims of this study was to perform a quantitatively evaluation of newly formed bone, vascular density (VD) and their correlation in animal model of posterolateral spinal fusion based on skeletal stem cells (SSCs) combined with a coral.

Methods: 15 rabbits received cell-material constructs, 15 rabbits were sham-operated (decortication of transverse apophyses), 15 rabbits received material alone. After 6 months the animals were sacrified. We performed a semi-quantitative and quantitative histologycal analysis of the fusion mass. To assess the VD, sections of the fusion mass were immunolabelled for alpha-smooth muscle actin as a vascular marker.

Results: No complete fusion was observed in all groups and no bone was formed in the interapophyseal region. Aboundant newly formed bone was observed in the peri-apophyseal regions in 60% of cases. The quantitative analysis showed a significantly higher amount of bone and VD in animals treated with cells and/or biomaterial alone compared to sham (p< 0.05). Periapophyseal VD and new bone formation was significantly higher compared to interapophyseal region in all groups (p< 0.05). Positive correlation exist between newly formed bone and vascolar density (p = 0,0009).

Conclusions: Interapophyseal region is scarcely vascolarized. The study shows a positive correlation between VD and osteogenesis. The inadequacy of staminal cells could be related with the poor survival after the implant. For the use of stam cells in the APL are necessary more studies in order to clarify the survival and in situ differentiation of the grafted cells in short and mid term.

Posterolateral spinal fusion is considered one of the most challenging condition for bone graft substitutes since using autogenous bone graft pseudarthrosis have been reported in 30% of cases.

MATERIALS AND METHODS.We develop a model of posterolateral spinal fusion in the rabbit based on skeletal stem cells (SSCs) loaded into a coral-hydroxyapatite material (Pro-Osteon 500RTM). 15 rabbits received cell-material constructs, 15 rabbits were sham-operated (decortication of transverse apophyses), 15 rabbits received material alone. The animals were housed for 6 months and radiographically monitored. At sacrifice, the explanted spine was analyzed by conventional and high resolution (Faxitron) radiography, and the outcome judged, blind of histology results, by two orthopedic surgeons.

RESULTS: radiographic evaluation showed a fusion rate rate of 90% in animals treated with cell constructs or biomaterial alone, and no fusion in the sham controls. Histology revealed abundant new bone formation directly on the scaffold in the cell construct and biomaterial alone groups, but no evidence of bone formation in the midregion of the interapophyseal space, where poorly vascular, dense fibrous tissue was observed.

CONCLUSIONS: The study shows that:

1) the cell-biomaterial constructs which per se were highly efficient in previous animal studies, used in different absolute quantities but identical ratios were not efficient in the direct preclinical model.

Since several spinal conditions are currently treated with spinal fusion, alternatives to autogenous bone graft in spinal surgery have been under study for many years. Results have shown that, compared to other non.-spinal conditions, such as filling bone cavities, spinal fusion, in particular posterolateral fusion, is much more challenging due to the reduced area of the graft bed. As a result, most of the bone substitutes are still under investigation and their effectiveness in the clinical setting has yet to be demonstrated.

In recent years the authors analysed several bone graft substitutes using an animal model which has been widely used in experimental spinal fusion. In particular, porous ceramics have been used alone or with osteoin-ductive material such as fresh bone marrow or cultured mesenchymal stem cells. The results of these studies have shown that with ceramic alone a percentage of solid fusion similar to that with autogenous bone graft cannot be achieved. However, compared to the latter, more favorable results have been obtained when ceramics are loaded with mesenchymal stem cells. The addition of fresh bone marrow to ceramics also increases the fusion rates; however, in this case new bone formation was mainly found in the peripheral portions of the graft and to a lesser extent than when cultured mesenchymal stem cells were used.