Residency · Residency · Chronic Pain Management

Intradiscal Procedures: Biacuplasty and Intradiscal PRP

Introduction

Intradiscal procedures are minimally invasive interventions that target the intervertebral disc itself as a pain generator. Unlike surgical options such as fusion or disc replacement, these techniques either modulate pain signaling within the disc or attempt to promote disc healing through biologic therapies. Biacuplasty uses bipolar radiofrequency energy to create controlled thermal lesions in the posterior annulus fibrosus, while intradiscal biologic therapies — platelet-rich plasma and stem cells — aim to modify the degenerative cascade at a cellular level.

Discogenic Pain: Pathophysiology

Discogenic pain originates from sensitized nociceptors within the damaged annulus fibrosus, particularly in the outer one-third and areas of annular disruption. Inflammatory mediators — TNF-alpha, IL-1, IL-6, and nerve growth factor — sensitize these nociceptors and stimulate the ingrowth of nociceptive nerve fibers into deeper annular layers that are normally not innervated. As a degenerative disc develops neovascularization and neoinnervation, a pain-generating substrate forms where innervation extends well beyond the normal outer annular boundary. Simultaneously, the nucleus pulposus becomes more acidic and proteoglycan degradation alters disc biomechanics, placing additional mechanical stress on the already compromised annulus.

Biacuplasty

Concept and Mechanism

Biacuplasty (developed by Baylis Medical/Stryker as the TransDiscal System) uses two internally cooled radiofrequency probes placed bilaterally in the posterior annulus fibrosus. Bipolar RF energy flows between the two probes, creating a controlled thermal lesion across the posterior annulus. The therapeutic goal is to denervate nociceptive fibers and coagulate inflammatory tissue without damaging the nucleus pulposus or adjacent structures. Internal cooling prevents excessive temperatures at the probe-tissue interface while allowing therapeutic temperatures of approximately 60-65 degrees Celsius to develop deeper in the annular tissue.

Technique

The patient is positioned prone under fluoroscopic guidance. Two 17-gauge introducer needles are placed bilaterally into the posterolateral annulus via an extrapedicular approach. The TransDiscal probes are then advanced through the introducers into the posterior annulus, positioned at approximately the 8 o'clock and 4 o'clock positions (or 7 and 5 o'clock). Probe position is confirmed on both AP and lateral fluoroscopy, with the tips ideally sitting at the junction of the inner and middle thirds of the posterior annulus. The bipolar RF treatment cycle runs for approximately 15 minutes, with continuous temperature and impedance monitoring throughout.

<image>Fluoroscopic illustration showing biacuplasty probe placement in the lumbar disc. The AP view demonstrates two radiofrequency probes positioned bilaterally in the posterior annulus fibrosus at the 4 o'clock and 8 o'clock positions. The lateral view confirms the probes seated in the posterior annulus. A superimposed thermal map shows the bipolar radiofrequency lesion zone (shaded red-orange) bridging the two probe tips across the posterior annulus, with cooled probe tips shown in blue.</image>

Evidence

The evidence base for biacuplasty includes a pilot study by Kapural et al. (2008) involving 15 patients, which showed significant improvement in VAS and ODI scores at 6 months. More importantly, the IDHE trial (Kapural et al., 2013) — a sham-controlled RCT with 63 patients — demonstrated significant improvement in pain (NRS), physical function (SF-36), and Oswestry Disability Index at 6 months in the biacuplasty group compared to sham. Desai et al. (2016) provided two-year follow-up data showing sustained benefit in treated patients. Selection criteria in these trials typically required concordant discogenic pain confirmed by provocation discography, single or two-level disease, disc height greater than 50% of normal, and failure of at least 6 months of conservative treatment.

Comparison to IDET

Intradiscal electrothermal therapy (IDET) was an earlier thermal intradiscal procedure that used a navigable catheter threaded circumferentially through the posterior annulus. Its results were mixed — Freeman (2005) showed no benefit versus sham, while Pauza (2004) demonstrated only modest benefit. IDET is now largely obsolete due to inconsistent evidence and the withdrawal of the SpineCATH device from the market. Biacuplasty offers a more uniform and predictable thermal lesion distribution compared to what IDET could achieve.

Intradiscal Platelet-Rich Plasma (PRP)

Rationale

PRP contains supraphysiologic concentrations of growth factors — PDGF, TGF-beta, VEGF, and IGF-1 — released from activated platelets. These growth factors may promote extracellular matrix synthesis, reduce inflammatory cytokine expression, and stimulate proliferation of resident disc cells. PRP represents a conceptual shift from the destructive (thermal) paradigm to a regenerative approach for discogenic pain.

Technique

Autologous blood (30-60 mL) is drawn and centrifuged to produce PRP. Leukocyte-poor PRP (LP-PRP) is generally preferred for intradiscal injection because white blood cells can exacerbate inflammation in the avascular disc environment. Under fluoroscopic guidance, a 22-gauge needle is placed into the center of the nucleus pulposus, and approximately 1-2 mL of PRP is injected into the disc.

Evidence

Tuakli-Wosornu et al. (2016) conducted a double-blind RCT of 47 patients that demonstrated significant improvement in pain (NRS) and function (FDI) at 8 weeks, with results sustained at 1 year in the PRP group compared to contrast injection controls. Akeda et al. (2022) published a prospective study showing improvement in pain and disability scores at 12 months following intradiscal PRP with releasate. Limitations of the current evidence include small sample sizes, variable PRP preparation protocols, and a lack of standardization across studies.

<image>Illustration comparing the two intradiscal approaches side by side. Left panel shows biacuplasty with bipolar RF probes in the posterior annulus creating a thermal lesion zone. Right panel shows intradiscal PRP injection with a single needle in the nucleus pulposus delivering platelet-rich plasma. Molecular insets show: (left) thermal denaturation of nociceptive nerve fibers in the annulus; (right) platelet degranulation releasing growth factors (PDGF, TGF-beta, IGF-1) stimulating disc cell matrix synthesis and reducing inflammatory cytokines.</image>

Intradiscal Stem Cell Therapy

Mesenchymal stem cells (MSCs) derived from bone marrow concentrate or adipose tissue have been investigated for disc regeneration. Pettine et al. (2015) published a prospective study of bone marrow concentrate injection into lumbar discs showing pain improvement at 1 and 2 years, with MRI evidence of disc rehydration in some patients. Noriega et al. (2017) conducted an RCT comparing allogeneic MSCs to sham that showed improvement in pain and disc height at 12 months. However, regulatory and safety considerations remain significant. These therapies are largely considered investigational in most jurisdictions, the FDA has not approved stem cell products for intradiscal use, and practitioners must navigate complex regulatory frameworks.

Patient Selection for Intradiscal Procedures

Appropriate patient selection is critical for all intradiscal procedures. Candidates should have confirmed discogenic pain via provocation discography with concordant pain reproduction, disc height preservation of at least 50% compared to adjacent normal levels, and single or two-level disease (multilevel disease has poorer outcomes). Patients should have failed at least 6 months of comprehensive conservative management and should not have significant disc extrusion, sequestration, or spinal stenosis that would require surgical decompression. Psychological screening to exclude patients with significant somatization or secondary gain is also recommended.

Clinical Pearls

Biacuplasty is the only thermal intradiscal procedure with sham-controlled RCT evidence supporting its efficacy; IDET is no longer considered evidence-based. Leukocyte-poor PRP is preferred for intradiscal injection because leukocyte-rich formulations may worsen inflammation in the avascular disc environment. Intradiscal biologic therapies are most promising for early degenerative disc disease (Pfirrmann grades 2-4), where viable disc cells remain that can respond to growth factor stimulation. All intradiscal procedures carry a risk of discitis (0.1-0.3%), making strict aseptic technique and antibiotic prophylaxis mandatory. The evidence base for intradiscal biologics is evolving rapidly, and patients should be counseled that these therapies remain in the early evidence phase with limited long-term outcomes data.

References

1. Kapural L, Vrooman B, Sarwar S, et al. A randomized, placebo-controlled trial of transdiscal radiofrequency, biacuplasty, for treatment of discogenic lower back pain. Pain Med. 2013;14(3):362-373.
2. Tuakli-Wosornu YA, Terry A, Boachie-Adjei K, et al. Lumbar intradiscal platelet-rich plasma (PRP) injections: a prospective, double-blind, randomized controlled study. PM R. 2016;8(1):1-10.
3. Pettine KA, Murphy MB, Suzuki RK, Sand TT. Percutaneous injection of autologous bone marrow concentrate cells significantly reduces lumbar discogenic pain through 12 months. Stem Cells. 2015;33(1):146-156.
4. Desai MJ, Kapural L, Petersohn JD, et al. A prospective, randomized, multi-center, open-label clinical trial comparing intradiscal biacuplasty to conventional medical management for discogenic lumbar back pain. Spine. 2016;41(13):1065-1074.

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