Optimal aspiration volume of vertebral bone marrow for use in spinal fusion

Human bone marrow-derived mesenchymal stem cells from different bone sources: a panorama

Regenerative medicine is a promising field in orthopaedic surgery. Although surgical treatments can produce excellent outcomes and may be the best choice for some patients, regenerative medicine can provide with more minimally-invasive treatment options. Mesenchymal stem cells (MSCs) are multipotent cells and are highly capable to differentiate into osteocytes or chondrocytes, while they can be isolated from different bone sources. The bone marrow aspiration from the posterior iliac crest appears to be preferred, as it provided a modestly higher concentration of nucleated cells [(25.1-54.7)×10⁶ cells/mL]. MSCs are also easily obtained from other bone sources, such as humerus, femur, tibia, vertebral body or calcaneus and have their content ranges between 5.8×10⁶ and 38.7×10⁶ nucleated cells. Although, they present a wide range of documented nucleated cells, they can be cultivated and expanded in vitro in multiple cell types, avoiding a second surgical site while preventing post-operative pain and the possible risk for infection. Thus, they represent a promising and encouraging treatment option in orthopaedic surgery.

The effect of a single consecutive volume aspiration on concentrated bone marrow from the proximal humerus for clinical application

BACKGROUND

Low aspiration volumes have been recommended to allow for higher concentrations of progenitor cells during bone marrow harvesting. However, these guidelines then require multiple aspiration attempts in order to maximize cellular yield. The purpose of this study was to investigate the effect of a single, high-volume aspiration with four consecutive aliquots on the number of nucleated cells (NCs) and colony-forming units (CFUs) in concentrated bone marrow aspirate (cBMA) taken from the proximal humerus.

METHODS

cBMA was taken from the proximal humerus of patients undergoing arthroscopic rotator cuff surgery. Four 12-mL double syringes were used consecutively from a single trocar to obtain four 10 cc aliquots. Each then underwent centrifugation to create a fractionated layer rich in nucleated cells. Following cellular separation, NCs were counted and CFUs were evaluated after incubation of 7-10 days. Cellular comparisons between each aliquot were performed along with their interaction with patient age and sex.

RESULTS

Twenty-nine patients (55.9 ± 4.6 years) were included in this study. The number of NCs and CFUs showed significant differences between the four aliquots of aspirate, with the first 10 cc aliquot providing the highest amount (p < 0.001, respectively). No significant differences were found between the sum of the three sequential aliquots compared to the initial 10 cc sample. There were no significant differences between male and female patients (p > 0.05). Increasing age resulted in no significant decrease in the number of NCs and CFUs across the four consecutive aliquots (p > 0.05).

CONCLUSION

In conclusion, while the initial aliquot provided the greatest number of nucleated cells and cultured CFUs, the addition of each sequential volume aspirate yielded similar amounts in total. This demonstrates the potential effectiveness of obtaining of higher volume aspirates from the proximal humerus during rotator cuff repair.

Implant Design and the Anchoring Mechanism Influence the Incidence of Heterotopic Ossification in Cervical Total Disc Replacement at 2-year Follow-up

STUDY DESIGN

A nonrandomized, prospective, and single-center clinical trial.

OBJECTIVE

The aim of this study was to determine whether the prosthesis design, and especially changes in the primary anchoring mechanism between the keel-based ProDisc C and the spike-based ProDisc Vivo, affects the frequency of heterotopic ossification (HO) formation over time.

SUMMARY OF BACKGROUND DATA

The occurrence of motion-restricting HO as well as underlying risk factors has so far been a widely discussed, but not well understand phenomenon. The anchoring mechanism and the opening of the anterior cortex may be possible causes of this unwanted complication.

METHODS

Forty consecutive patients treated with the ProDisc C and 42 consecutive patients treated with the ProDisc Vivo were compared with respect to radiological and clinical outcome, with 2 years of follow-up. Clinical outcome scores included the Neck Disability Index (NDI), Visual Analogue Scale (VAS), and arm and neck pain self-assessment questionnaires. Radiological outcomes included the segmental lordosis and range of motion (ROM) of the index-segment as well as the occurrence of HO.

RESULTS

The clinical outcome parameters improved in both groups significantly. [ProDisc C: VAS arm and neck pain from 6.3 and 6.2 preoperatively to 0.7 and 1.3; NDI from 23.0 to 3.7; ProDisc Vivo: VAS arm and neck pain from 6.3 and 4.9 to 1.4 and 1.6, NDI from 34.1 to 8.7; 2-year follow-up (FU)]. The ProDisc Vivo cohort demonstrated a significantly lower incidence of HO than the ProDisc C group at 1-year FU (P = 0.0005) and 2-year FU (P = 0.005). Specifically, high-grade HO occurred in 9% versus 31%.

CONCLUSION

These findings demonstrate that prosthesis designs that allow primary anchoring without violation of the cortical surface help to reduce the incidence of severe ossification, possibly affecting the functionality and mobility of the artificial disc device over of time.

LEVEL OF EVIDENCE

3.

Substantial Overview on Mesenchymal Stem Cell Biological and Physical Properties as an Opportunity in Translational Medicine

Mesenchymal stem cells (MSC) have piqued worldwide interest for their extensive potential to treat a large array of clinical indications, their unique and controversial immunogenic and immune modulatory properties allowing ample discussions and debates for their possible applications. Emerging data demonstrating that the interaction of biomaterials and physical cues with MSC can guide their differentiation into specific cell lineages also provide new interesting insights for further MSC manipulation in different clinical applications. Moreover, recent discoveries of some regulatory molecules and signaling pathways in MSC niche that may regulate cell fate to distinct lineage herald breakthroughs in regenerative medicine. Although the advancement and success in the MSC field had led to an enormous increase in the amount of ongoing clinical trials, we still lack defined clinical therapeutic protocols. This review will explore the exciting opportunities offered by human and animal MSC, describing relevant biological properties of these cells in the light of the novel emerging evidence mentioned above while addressing the limitations and challenges MSC are still facing.

Stem Cells in Spinal Fusion

STUDY DESIGN

Review of literature.

OBJECTIVES

This review of literature investigates the application of mesenchymal stem cells (MSCs) in spinal fusion, highlights potential uses in the development of bone grafts, and discusses limitations based on both preclinical and clinical models.

METHODS

A review of literature was conducted looking at current studies using stem cells for augmentation of spinal fusion in both animal and human models.

RESULTS

Eleven preclinical studies were found that used various animal models. Average fusion rates across studies were 59.8% for autograft and 73.7% for stem cell-based grafts. Outcomes included manual palpation and stressing of the fusion, radiography, micro-computed tomography (μCT), and histological analysis. Fifteen clinical studies, 7 prospective and 8 retrospective, were found. Fusion rates ranged from 60% to 100%, averaging 87.1% in experimental groups and 87.2% in autograft control groups.

CONCLUSIONS

It appears that there is minimal clinical difference between commercially available stem cells and bone marrow aspirates indicating that MSCs may be a good choice in a patient with poor marrow quality. Overcoming morbidity and limitations of autograft for spinal fusion, remains a significant problem for spinal surgeons and further studies are needed to determine the efficacy of stem cells in augmenting spinal fusion.

Only prolonged time from abstraction found to affect viable nucleated cell concentrations in vertebral body bone marrow aspirate

BACKGROUND CONTEXT

Vertebral body-derived bone marrow aspirate (BMA, with an appropriate carrier) is a potential alternative to traditional iliac crest bone graft for use in spinal fusion surgery. No studies have looked at the effect of different temporary handling/storage conditions on the osteoprogenitor potential of BMA. This is especially important because aspirate, as with cancellous and/or cortical grafts, may be extracted some time before actual implementation in regular clinical use.

PURPOSE

To characterize factors that affect BMA cell concentration during routine spinal instrumentation, this study examined whether cell counts change significantly between the second pedicle aspirated and the first pedicle harvested at the same vertebral level. This study also aims to examine the optimal perioperative storage conditions for BMA obtained from the vertebral body.

STUDY DESIGN

In vitro concentrations of viable cells were determined in BMA harvested from the first and second pedicles on every vertebral level, and after 1 hour of storage in different perioperative conditions.

PATIENT SAMPLE

BMA was harvested from 28 pedicles from seven patients undergoing lumbar instrumented fusion surgeries.

OUTCOME MEASURES

The outcome measure included viable nucleated cell concentrations in BMA.

METHODS

After obtaining HIC approval from our institution, 28 vertebral marrow aspirates (obtained from seven patients) were evaluated. Based on prior work, 4-mL aspirates from each pedicle were evaluated. BMA was aspirated from both pedicles of two vertebral levels per patient. Samples were divided and placed in different storage conditions to examine the effect of laterality (first versus second pedicle aspirated per level), temperature, media, and time, on nucleated cell counts. No funding was received for this study, and the authors disclose no study specific conflicts of interest.

RESULTS

Cell count was not significantly different between the first or second side aspirated for each vertebral level. Similarly, no significant differences were found for samples after 1 hour of storage at different temperatures (0 °C, room temperature, or 37 °C) or media (none, saline, essential media). Of the conditions examined, time from aspiration was the only variable found to have an impact on nucleated cell counts (p=.003). The viable cell count decreased to less than half by 4 hours.

CONCLUSION

As vertebral BMA is increasingly considered as a bone grafting option, the field would be remiss not to consider factors that could affect cell viability after abstraction and before implementation. We expected a greater effect of perioperative storage conditions than was observed. Although the variables evaluated might show small effects on cell viability in a larger study, this would not be expected to be significant. In the current study, only prolonged time from abstraction could be shown to have a significant effect on cell viability.