Spinal fusion surgery is a last resort for patients living with degenerative discs and painful spinal alignment issues. The procedure involves fusing loose vertebrae together by the insertion of a local bone graft and hardware. Ideally, the bone graft initiates biological processes which causes the vertebrae to grow together and stabilize the spine. Unfortunately, up to 43% of procedures result in nonunion which could require additional surgeries and decrease the patient’s quality of life.¹ This article discusses recent research (Japan, 2017) which shows how the addition of platelet rich plasma (PRP) improves bone union for patients undergoing spinal fusion surgery.
Positive Outcomes with the Addition of PRP in Spinal Fusion
The study design included 62 patients undergoing posterolateral lumbar fusion to treat lumbar degenerative spondylosis with instability. The patients were randomized into two groups; the treatment group received 20 ml of activated PRP at the bone graft site, while the control group underwent the same procedure without the addition of PRP. The PRP was prepared from 400 ml of peripheral venous blood which underwent dual-centrifugation to isolate and concentrate the platelets. Initial centrifugation at 1,660 rpm for 5 min isolated erythrocytes. The resulting supernatant was centrifuged again at 1,450 rpm for 15 min to concentrate the platelets. In total 22 ml of PRP was produced, of which 2 ml was analyzed for platelet and growth factor content. Analysis found that the PRP to contain 7.7 times the platelet count of whole blood and 50 times the growth factors.¹
Researchers added .5 ml of 1,000 U/mL liquid thrombin solution and 1 ml of 2% calcium chloride solution to activate the platelets. The activators initiated platelet degranulation, which lead to massive growth factor release and created a PRP gel. The PRP gel was mixed with the autogenous local bone for insertion at the graft site. The study measured fusion rate and fusion mass with radiography every 3 months and with computed tomography (CT) at 12 and 24 months. Bone fusion and scores for low back pain, leg pain, and leg numbness were measured at 3, 6, 12, and 24 months. Bone fusion was assessed using anteroposterior radiographic images and pain scores were assessed with a visual analogue scale (VAS).¹
Researchers found significantly improved outcomes with the in-operation addition of activated platelet rich plasma, including increased bone union rate, increased area of fusion mass and decreased average time to complete union. Bone union rate at the 24-month follow-up was 94% in the PRP group compared to 74% in the control group. The area of fusion mass was 572 mm² in PRP group and 367 mm² in the non-treatment group. Average time necessary for full union was 7.8 months in the treatment group and 9.8 months for patients in the control group. There were no adverse events reported in either group and no significant difference in pain or numbness between the groups.¹
How Does PRP Effect Bone Fusion?
Human blood is composed of plasma, red blood cells, white blood cells, and platelets. The primary function of platelets is to prevent blood loss by clotting together at the site of vascular rupture. Platelets also create the foundation for tissue regeneration throughout the body by releasing growth factors during degranulation. Growth factors are tiny bioactive proteins which bind to the receptors of target cells including mesenchymal stem cells (MSCs), osteoblasts, fibroblasts, endothelial cells, and epidermal cells. Once bound to the target cells, the growth factors increase cell signaling and the expression of genes which direct cellular proliferation, matrix formation, osteoid production, collagen synthesis, and angiogenesis.
In spinal fusion surgery, increased concentration of platelets initiates and biologically amplifies the healing cascade. Growth factors at the bone graft site increase local cell signalling, mitogenesis, and chemotaxis. Increased bone fusion rates could be attributed to matrix formation, osteoid production and increased MSC migration.
Conflicting Results in Orthobiologics
Previous studies looking at the potential for PRP to positively influence bone fusion rates have found conflicting results. One such study developed by Weiner and Walker was published as a retrospective case series in 2003. Their results seem to show decreased fusion rates in patients who received ”autologous growth factors” (AGF). Their work compared 27 patients (average age 56) who underwent single-level lumbar intertransverse fusions without the addition of “AGF” to 32 patients (average age 61) who underwent the same procedure with the addition of “AGF.” Regrettably, this study was not fully blinded or randomized which introduces great potential for bias. Additionally, the authors failed to describe the “AGF” preparation process or analyze platelet and growth factor content. Without providing essential information regarding the chief variable, it’s impossible to say what was really tested here.²
Does Insurance Cover PRP for Spinal Fusion?
The design of Weiner and Walker case series presents less substantial evidence when compared to the blinded, randomized, and controlled trial out of Japan. Though the study designs don’t compare, conflicting results make it easier for insurance companies to deny coverage for PRP and generalize the treatment as “experimental.”
The previously discussed 2017 study indicates that the addition of PRP gel increases bone union rate in spinal fusion surgery which translates to better outcomes for patients and decreased financial burden for the healthcare system. Though stand alone PRP procedures are generally not covered by insurance, the potential for reimbursement is greatest when PRP is used in conjunction with a surgical procedure such as spinal fusion.
Treating Chronic Back Pain
The prevalence of spinal fusion surgery has increased dramatically over the past 20 years. For example, hospital expenses associated with spinal fusion procedures increased 690% from 1998 to 2008.³ The procedure is elected to treat patients with a variety of conditions including degenerative disc disease, spondylolisthesis (when one vertebra slips forward over another) and spinal stenosis (a narrowing of the spaces within the spine, which leads to nerve pressure.) Unfortunately, no high level evidence exists to support the massive increase in spinal fusions.⁴ Contrarily, recent research indicates spinal fusion surgery is not an adequate long term fix because of resulting adjacent segment degeneration (ASD).⁵
The Perils of Spinal Fusion
According to a 2016 retrospective study, radiological ASD was identified at the 10-year follow-up in over 50% of patients with a history of circumferential lumbar fusion. Symptomatic ASD resulted in additional surgeries for 37.5% of patients at the 15-year follow up.⁵ Though the exact etiology of ASD is still up for debate, the disease is clearly related to spinal fusion surgery in that it only occurs in the vertebrae above or below spinal fusion. Vertebrae of the spinal column are meant give and flex for optimal mobility. When two or more vertebrae are fused together the joints above and below become overloaded resulting symptomatic ASD.
Spinal Stability with Prolotherapy
Generally, patients opting for spinal fusion surgery have a long history of back pain and failed to respond to conservative treatments. Many cases of low back pain include some degree of instability. Though spinal fusion may be the only option in cases of severe instability, may patients could benefit from conservative therapies such as prolotherapy injections at the site of instability. A 2005 case series studied the effects of prolotherapy injections on cervical instability in 6 patients with 2.7 mm of absolute cervical translation. Patients underwent 3 prolotherapy injections (12.5% dextrose diluted with saline plus 1-2cc of lidocaine per 10 cc) at all sites with demonstrated translation. The study found decreases in translation for all patients and a statistically significant reduction in VAS pain scores.⁶ If increased spinal stability is possible with minimally invasive dextrose prolotherapy, what could be possible with PRP prolotherapy?
Spinal fusion surgery comes with many risks including adjacent segment degeneration, non-union, and opioid addiction. The potential for PRP injections to increase spinal stability and prevent fusion has yet to be explored, but could be a fruitful avenue given the positive effects of prolotherapy injections. In cases where fusion is necessary, the addition of activated PRP gel has been shown to increased bone union rate, increased area of fusion mass and decreased average time to complete union.
References
- Kubota G, Kamoda H, Orita S, Yamauchi K, Sakuma Y, Oikawa Y, Inage K, Sainoh T, Sato J, Ito M, Yamashita M, Nakamura J, Suzuki T, Takahashi K, Ohtori S. Platelet-rich plasma enhances bone union in posterolateral lumbar fusion: a prospective randomized controlled trial. The Spine Journal. 2017. http://dx.doi.org/doi:10.1016/j.spinee.2017.07.167.[ncbi]
- Weiner BK, Walker M. Efficacy of autologous growth factors in lumbar intertransverse fusions. Spine. 2003 Sep 1;28(17):1968-70. DOI: 10.1097/01.BRS.0000083141.02027.48.[ncbi]
- Rajaee S, Kanim L, Delamarter R B, Bae H W. A Careful Analysis of Trends in Spinal Fusion in the United States from 1998 to 2008. Poster No. 642. Orthopaedic Research Society, 2011 Annual Meeting.[pdf]
- Deyo R, MD, Nachemson A, MD, PhD, Mirza S, MD. Spinal-fusion surgery – the case for restraint. N Engl J Med 2004; 350:722-726. DOI: 10.1056/NEJMsb031771.[ncbi]
- Maruenda JI, Barrios C, Garibo F, Maruenda B. Adjacent segment degeneration and revision surgery after circumferential lumbar fusion: outcomes throughout 15 years of follow-up. Eur Spine J. 2016 May;25(5):1550-1557. doi: 10.1007/s00586-016-4469-5.[ncbi]
- Centeno C, MD, Elliott J, MSPT, PhDc, Elkins W, MPH, Freeman M, PhD, MPH, DC. Fluoroscopically guided cervical prolotherapy for instability with blinded pre and post radiographic reading. Pain Physician. 2005;8:67-72, ISSN 1533-3159.[pdf]
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