A retrospective study investigating decrease in the nucleus pulposus signal intensity or disc height on magnetic resonance imaging (MRI) and disc degeneration.
Although a degenerated disc cannot self-regenerate, distraction or stabilization may provide suitable conditions for rehydration and possible regeneration. This study aimed to evaluate clinical outcomes and disc regeneration via MRI in a series of patients with degenerative disc disease (DDD) who underwent lumbar stabilization with a dynamic stabilization system (DSS).
A dynamic system provides rehydration during early DDD.
Fifty-nine patients (mean age, 46.5 years) who undedwent stabilization with DSS for segmental instability (painful black disc) between 2004 and 2014 were retrospectively evaluated. All patients underwent MRI preoperatively and 12 months postoperatively. Intervertebral disc (IVD) degeneration grades at the implanted segment were categorized using the Pfirrmann classification system. Patients were followed for a mean of 6.4 years, and clinical outcomes were based on visual analog scale (VAS) and Oswestry disability index (ODI) scores.
Significant improvements in back pain VAS and ODI scores from before surgery (7 and 68%, respectively) were reported at 6 (2.85 and 27.4%, respectively) and 12 months postoperatively (1.8 and 16.3%, respectively). Postoperative IVD changes were observed in 28 patients. Improvement was observed in 20 patients (34%), whereas progressive degeneration was observed in eight patients (13.5%). Thirty-one patients (52.5%) exhibited neither improvement nor progression. Single Pfirrmann grade improvements were observed in 29% of the patients and two-grade improvements were observed in 5%.
Our observations support the theory that physiological movement and a balanced load distribution are necessary for disc regeneration. We conclude that DSS may decelerate the degeneration process and appears to facilitate regeneration.
The intervertebral disc (IVD) is the most important stabilizing and load-bearing structure in the spinal column and is also among the main causes of back pain [
Disc degeneration is associated with a loss of proteoglycans [
A degenerated disc cannot self-regenerate. In addition, long-term elevated or impaired intradiscal pressure prevents regeneration [
Fifty-nine patients (33 females and 26 males) with segmental instability and DDD (painful black disc) who underwent a DSS procedure between 2004 and 2014 and participated in follow-up MRI scans were included in the study. All patients were stabilized after annulus reconstruction, which involved the removal of dead nuclear tissue fragments from among the annulus layers, followed by bipolar cauterization and shrinkage of the remaining slack annulus layers and strengthening of the posterior wall. Patients had a mean age of 46.5 years (range, 27–67 years) and were followed up for a mean of 6.4 years (range, 1–11 years). Patients' demographic data are shown in
The main indications for surgical decisions included a black disc on MRI, axial low back pain (DDD) with or without disc herniation, modic types I and II degeneration, and large annulus defects. The last group included patients with painful discs and severe fatty degeneration or paravertebral muscle atrophy. Although no useful measurement of muscle strength is currently available, MRI can provide valuable information about fatty degeneration and volumes of back muscles [
MRI was performed on a 1-T scanner (Siemens Magnetom Espree; Siemens AG, Erlangen, Germany), using the following parameters for sagittal plain T2-weighted imaging: repetition time, 3,820 millieconds; echo time, 112 milliseconds; and slice thickness, 4 mm. For all studies, the imaging protocol comprised T1- and T2-weighted sagittal and T2-weighted axial fast spin-echo sequences. All patients underwent MRI preoperatively and 12 months postoperatively. MRI scans were evaluated by three independent radiologists, and IVD degeneration grades were assigned at the implanted segment according to the Pfirrmann classification of lumbar IVD degeneration at the implanted segment [
The patients' quality of life and back pain scores were evaluated using the Oswestry disability index (ODI) and visual analog pain scale (VAS; 0, no pain; 10, worst pain), respectively, preoperatively and at 6 and 12 months postoperatively.
For patients with a loose annulus without rupture, we only performed a dynamic stabilization procedure via the Wiltse approach. For patients in whom disc fragments were present among the ruptured annulus layers, we removed the fragments under microscopic guidance before performing stabilization. All operations were performed under general anesthesia and with the patient in a knee-to-chest position to maintain physiological lordosis of the lumbar vertebrae. A prophylactic antibiotic was preoperatively administered to all patients. The pathological level was localized using intraoperative fluoroscopy. An approximately 3-cm medial incision was made if annulus reconstruction was required. After paravertebral musculature dissection, a small laminectomy was performed using a high-speed drill. Subsequently, the ligamentum flavum was incised near the degenerated disc. After identifying the dura and nerve root and determining the annulus, a small incision was immediately made over the ruptured annulus, and small fragments were removed using a micro-nerve hook. The annulus was then cauterized and made to shrink with a bipolar cautery.
Following microscopic decompression, posterior dynamic transpedicular stabilization was performed via the Wiltse approach [
Two different stabilization systems were used. The Cosmic DSS (Ulrich GmbH & Co. KG, Ulm, Germany) was used in 30 patients, and the Safinaz DSS (Medikon AS, Istanbul, Turkey) was used in 29 patients. The Cosmic system used a 6.25-mm threaded rigid rod, with a hinged screw head to limit movement. The Safinaz system used a 6-mm non-threaded rigid rod, with a hinged screw head to limit movement. Stabilization was performed at the following levels: L2–L3 in one patient, L3–L4 in four, L4–L5 in 40, and L5–S1 in 14. All surgeries were performed by the same two experienced surgical teams, and optimal neural decompression and physiological motion preservation were the goals for all patients.
No adhesion, fibrosis, infection, or chronic inflammation was observed during the long-term follow-up period. Similarly, no disc herniation was observed.
The back pain VAS scores significantly improved from 7 (range, 6–9) before DSS procedures to 2.85 (range, 1–5) at 6 months and 1.8 (range, 0–3) at 12 months postoperatively. Similarly, the ODI scores significantly improved from 68% (range, 48%–92%) preoperatively to 27.4% (range, 12%–56%) at 6 months and 16.3% (range, 4%–32%) at 12 months postoperatively (
We compared disc degeneration at the implantation segments on preoperative and 1-year postoperative T2-weighted sagittal MRI scans according to the Pfirrmann lumbar IVD degeneration classification. In the preoperative images, we observed grades 3, 4, and 5 degeneration in 7, 45, and 7 patients, respectively. After 12 months of follow-up, we observed grades 2, 3, 4, and 5 degeneration in 7, 19, 19, and 14 patients, respectively (
Postoperative IVD changes were observed in 28 patients. Improvement (disc rehydration) was observed in 20 patients (34%) (
Progressive degeneration was observed only in patients with grade 4 degeneration, and recurrent disc herniation was not observed in any patients. There were no clinical findings associated with adjacent segment disease. On the other hand, several patients exhibited adjacent segment alterations after undergoing stabilization procedures. Among patients without disc changes (n=31), only one developed degeneration at an adjacent segment. Among those with progressive degeneration (n=8), two patients developed adjacent segment degeneration. None of the patients with improved conditions (n=20) developed alterations at adjacent segments.
A decreases in the fluid content of NP leads to a decrease in hydrostatic pressure [
Multiple studies have shown that axial IVD distraction can induce extracellular matrix gene expression [
Lumbar fusion surgery is widely used to treat degenerative lumbar diseases, such as instability or stenosis [
DSS is a relatively new form of stabilization for disc degeneration or instability [
Mulholland and Sengupta [
Lotz and Chin [
Through animal studies, Guehring et al. [
Putzier et al. [
Cho et al. [
The application of DSS to a functional segment does not guarantee that rehydration of the disc will occur as the degeneration level is a very important factor in healing. During early degeneration, this process may be reversible, as observed in some of our patients. However, fusion is inevitable in patients with advanced degeneration, just as spontaneous fusion occurs with end-stage degeneration in nonoperative patients. A limited discectomy should be performed in patients with Pfirrmann grade 1–2 degeneration because of the high risk of recurrence. It is likely that aggressive subtotal discectomy led to fusion in the patient shown in
Our study was mainly limited by the short follow-up period. A longer follow-up period may provide more consistent conclusions. In addition, further randomized clinical trials are needed to prove that DSSs can facilitate disc regeneration.
Our results suggest that DSSs do not harm IVD and appear to facilitate regeneration, with benefits to the patient. We conclude that there are three possible results after DSS application: (1) disc rehydration, (2) no change, and (3) fusion. We observed no relationship between radiological and clinical results.
VAS, visual analog scale; ODI, Oswestry disability index.