Mohssen Hakimi

Combined use of platelet-rich plasma and autologous bone grafts in the treatment of long bone defects in mini-pigs

The use of platelet-rich plasma (PRP) for improving of bone defect healing is discussed controversially. The aim of this study was to assess the effect of PRP in combination with autologous cancellous graft on bone defect healing in a critical metaphyseal long bone defect. A critical size defect in the tibial metaphysis of 16 mini-pigs was filled either with autologous cancellous graft as control group or with autologous cancellous graft combined with autologous PRP. Compared to native blood platelets were enriched about 4.9-fold in the PRP. After 6 weeks, the specimens were assessed by X-ray and histological evaluation. Histomorphometrical analysis revealed that the area of new bone was significantly higher in the PRP group concerning the central area of the defect zone (p<0.02) as well as the cortical defect zone (p<0.01). All defects showed substantial new bone formation, but only defects of the PRP group regenerated entirely. The PRP group was superior to the control group even in the semi-quantitative assessment of the osseous bridging in both observed areas of the defect. Within the limits of the present study it could be demonstrated that PRP combined with autologous cancellous graft leads to a significantly better bone regeneration compared to isolated application of autologous cancellous graft in an in vivo critical size defect on load-bearing long bones of mini-pigs.

Platelet-Rich Plasma on Calcium Phosphate Granules Promotes Metaphyseal Bone Healing in Mini-Pigs

The role of platelet‐rich plasma (PRP) as a promoter of bone healing remains controversial. The aim of this study was to investigate the effect of PRP in combination with calcium phosphate granules (CPG) on bone defect healing in a metaphyseal long bone defect. A metaphyseal bone defect at the proximal tibia of 16 mini‐pigs was filled with CPG combined with autologous PRP or CPG solely (control group). The PRP showed 4.4‐fold more platelets compared to peripheral blood. Six weeks after surgery the radiological and histomorphometrical evaluations showed significantly more bone formation in the PRP group in the central area of the defect zone (p < 0.01) as well as the cortical defect zone (p < 0.04). Furthermore, the resorption rate of CPG was increased in animals who received PRP. Nevertheless there were only isolated instances of complete osseous bridging of the bone defects even in the PRP group. This study demonstrates that a PRP‐CPG composit promotes bone regeneration but does not lead to a solid fusion of a tibial defect in mini‐pigs.

Pitfalls and complications in the use of the proximal femoral nail

Background and aimsOsteosynthesis with the proximal femoral nail (PFN) features the advantages of high rotational stability of the head–neck fragment, an unreamed implantation technique and the possibility of static or dynamic distal locking. However, the use of the nail is technically ambitious and is accompanied by some risks of error, which can lead to failure of the osteosynthesis. In this paper we present the results of a critical analysis of mistakes that were made in our hospital during the introduction period of this implant.Patients and methodsWe carried out a prospective analysis of the data of 121 consecutive patients who were suffering from trochanteric or subtrochanteric fracture between December 1997 and December 2000 and who had been treated with a PFN.ResultsWe identified intraoperative technical difficulties in 23 patients (19.1%). Seven cases showed postoperative local complications that required operative revision on six patients (4.9%). The main reasons for the failure of the operations involved were poor reduction and wrong choice of screws. Following our critical analysis, we were able to avoid those problems.ConclusionsWhen 31A fractures are to be stabilised with a PFN, the precise technical performance of the implantation represents the basic surgical requirement. Already present minor deviations will subsequently cause loosening of the implants and failure of the operation.

Bone Marrow Aspiration Concentrate and Platelet Rich Plasma for Osteochondral Repair in a Porcine Osteochondral Defect Model

Background Bone marrow aspiration concentrate (BMAC) may possess a high potency for cartilage and osseous defect healing because it contains stem cells and multiple growth factors. Alternatively, platelet rich plasma (PRP), which contains a cocktail of multiple growth factors released from enriched activated thrombocytes may potentially stimulate the mesenchymal stem cells (MSCs) in bone marrow to proliferate and differentiate. Methods A critical size osteochondral defect (10×6 mm) in both medial femoral condyles was created in 14 Goettinger mini-pigs. All animals were randomized into the following four groups: biphasic scaffold alone (TRUFIT BGS, Smith & Nephew, USA), scaffold with PRP, scaffold with BMAC and scaffold in combination with BMAC and PRP. After 26 weeks all animals were euthanized and histological slides were cut, stained and evaluated using a histological score and immunohistochemistry. Results The thrombocyte number was significantly increased (p = 0.049) in PRP compared to whole blood. In addition the concentration of the measured growth factors in PRP such as BMP-2, BMP-7, VEGF, TGF-β1 and PDGF were significantly increased when compared to whole blood (p<0.05). In the defects of the therapy groups areas of chondrogenic tissue were present, which stained blue with toluidine blue and positively for collagen type II. Adding BMAC or PRP in a biphasic scaffold led to a significant improvement of the histological score compared to the control group, but the combination of BMAC and PRP did not further enhance the histological score. Conclusions The clinical application of BMAC or PRP in osteochondral defect healing is attractive because of their autologous origin and cost-effectiveness. Adding either PRP or BMAC to a biphasic scaffold led to a significantly better healing of osteochondral defects compared with the control group. However, the combination of both therapies did not further enhance healing.

Functional results and complications following locking palmar plating on the distal radius: a retrospective study

This retrospective study investigates the radiological and the functional results as well as complications following locking palmar plating on the distal radius. Eighty-nine adult patients with a dorsally displaced distal radius fracture were treated using a locking palmar plate at our clinic over a period of 25 months. The radiological and functional results as well as the DASH score were recorded for 77 out of 89 patients in the routine final examinations conducted on average 12 months later. The radiological examinations showed a relevant shortening of the radius among five patients. A dorsal angulation of more than 20° as well as a radial inclination of less than 10° was observed in 11 patients. Most of the patients showed good to excellent functional and radiological results as well as good results on the DASH score. A3 fractures in elderly patients and the majority of C1 and C2 fractures can be safely treated with locking palmar plating.

Biomechanical cadaver testing of a fixed-angle plate in comparison to tension wiring and screw fixation in transverse patella fractures.

INTRODUCTION Operative treatment of patella fractures is frequently associated with implant failure and secondary dislocation which can be attributed to the employed hardware. Therefore, a 2.7 mm fixed-angle plate designed for the treatment of patella fractures was tested biomechanically against the currently preferred methods of fixation. It was hypothesized that under simulated cyclic loading fixed-angle plating would be superior to modified anterior tension wiring or cannulated lag screws with anterior tension wiring. MATERIALS AND METHODS Eighteen human cadaver knees, matched by bone mineral density and age, were divided into three groups of six. After setting a transverse patella fracture each group received one of the osteosyntheses mentioned above. Repetitive testing over 100 cycles was performed at non-destructive loads by simulating knee motion from 90° flexion to full extension. RESULTS Anterior tension wiring as well as lag screws with tension wiring showed significant fracture displacement after the initial cycle already. Both constructs, lag screws plus wiring (3.7 ± 2.7 mm) as well as tension wiring alone (7.1 ± 2.2 mm) displayed fracture displacement of >2 mm which is clinically regarded as failure. Those patellae stabilized with fixed-angle plates showed no significant fracture gap widening after completion of 100 cycles (0.7 ± 0.5 mm). The differences between the fixed-angle plate group and the other two groups were statistically significant (p<0.05). CONCLUSION In contrast to modified anterior tension wiring and cannulated lag screws with anterior tension wiring the bilateral fixed-angle plate was the only fixation device to stabilize transverse patella fractures securely and sustainably.

Isolated subtalar dislocation.

BACKGROUND Little attention has been devoted to subtalar dislocations without an associated bone injury in the literature to date. The aim of this study was to assess the functional and subjective results of a cohort of patients with this injury. METHODS A total of ninety-seven patients with a subtalar dislocation were treated at two major university trauma centers from January 1994 to March 2007. Computed tomographic scans indicated a subtalar dislocation without associated bone injury in twenty-three of these patients. Clinical and radiographic examinations were performed on all twenty-three patients at an average of 58.3 months after the completion of treatment. The postoperative clinical examination was supplemented by the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale, and the degree of arthritis was assessed radiographically. RESULTS The average score on the AOFAS ankle-hindfoot scale score was 82.3 points. Twenty-one patients achieved a good result, and two patients had a satisfactory result. The range of motion of the subtalar joint was an average of 41.3 degrees. No difference between the results of the medial and lateral subtalar dislocations was observed. Only six patients had minor radiographic changes. CONCLUSIONS The intermediate-term results for a subtalar dislocation without an associated osseous injury are good, and the direction of the dislocation does not appear to make a difference with regard to clinical or radiographic outcome.

Fixed-angle plate osteosynthesis of the patella - an alternative to tension wiring?

BACKGROUND The goal of this study is carry out a biomechanical evaluation of the stability of a bilateral, polyaxial, fixed-angle 2.7 mm plate system specifically designed for use on the patella. The results of this approach are then compared to the two currently most commonly used surgical techniques for patella fractures: modified anterior tension wiring with K-wires and cannulated lag screws with anterior tension wiring. METHODS A transient biomechanical analysis determining material failure points of all osteosyntheses were conducted on 21 identical left polyurethane foam patellae, which were osteotomized horizontally. Evaluated were load (N), displacement (mm) and run-time (s) as well as elastic modulus (MPa), tensile strength (MPa) and strain at failure (%). FINDINGS With a maximum load capacity of 2396 (SD 492) N, the fixed-angle plate proved to be significantly stronger than the cannulated lag screws with anterior tension wiring (1015 (SD 246) N) and the modified anterior tension wiring (625 (SD 84.9) N). The fixed-angle plate displayed significantly greater stiffness and lower fracture gap dehiscence than the other osteosyntheses. Additionally, osteosynthesis deformation was found to be lower for the fixed-angle plate. INTERPRETATION A bilateral fixed-angle plate was the most rigid and stable osteosynthesis for horizontal patella fractures with the least amount of fracture gap dehiscence. Further biomechanical trials performed under cycling loading with fresh cadaver specimen should be done to figure out if a fixed-angle plate may be an alternative in the surgical treatment of patella fractures.

Influence of foot positions on the spine and pelvis.

The management of knee osteoarthritis includes the use of wedged shoe insoles to unload the affected knee compartment. Although the biomechanical effects of shoe insoles on the knee joint are known and described, only little is known about their influence on the pelvis and spine. Therefore, the purpose of this study was to evaluate the effects of different foot positions, such as how they could be achieved by shoe insoles, on pelvic position and spinal posture.

Cone Beam CT in Assessment of Tibial Bone Defect Healing: An Animal Study

RATIONALE AND OBJECTIVES To evaluate cone beam computed tomography (CBCT) for monitoring of tibial bone defect healing in comparison to histopathological findings. MATERIALS AND METHODS Circumscribed tibial bone defects were created in 16 mini-pigs and imaging of the tibia was performed on day 42 using a modern CBCT scanner with flat panel detector (PaX-Duo3D, Vatech, Korea). The extent of osseous consolidation including remaining calcium phosphate granules was measured quantitatively by a CBCT volumetry tool using commercially available software (Osirix Imaging software, Pixmeo, Geneva, Switzerland). Volumes of the entire defect (including all pixels), areas of osseous consolidation (density values >2350) and nonmineralized areas (density values <2350) of the defect were determined. The extent of bone regeneration was determined and correlated with the histomorphometrical reference standard. Independently, a visual semiquantitative CBCT-score was applied (4-point scale) to assess bone defect healing. RESULTS The extent of osseous consolidation in CBCT volumetry ranged from 14% to 92% (mean, 63.4 ± 17.6%). There was a significant positive correlation between histologically visible newly formed bone and the extent of bone regeneration on CBCT volumetry (r = 0.74-0.79, P < .001). The visual score matched with the volumetric results in 75% of the cases. CONCLUSION CBCT volumetry allows for reliable, noninvasive quantitative monitoring of bone defect healing and correlates significantly with histological findings. CBCT is a promising technique for imaging of peripheral bones suggesting further evaluation in clinical trials.