Abstract
Endovenous thermal ablation of the below-knee great saphenous vein (GSV) risks saphenous nerve injury because the vein and nerve lie in close apposition. We propose the segmental point obliteration technique, which delivers intermittent point-by-point laser pulses (6 W, ≈1 mm) instead of continuous pullback, with an interval of 1 to 2 seconds between pulses. In 13 patients (19 limbs) followed for 1 month, no paresthesia occurred, and complete occlusion was achieved in all limbs. Segmental point obliteration technique appears feasible for nerve-sparing below-knee GSV ablation, although more comparative longer-term studies are needed to determine its efficacy and overall role in below-knee GSV treatment.
Keywords: Endovenous laser ablation, Great saphenous vein, Saphenous nerve, Paresthesia, Varicose veins
Endovenous thermal ablation is the first-line treatment for great saphenous vein (GSV) insufficiency, and guidelines recommend treating the full length of the incompetent vein when reflux extends below the knee.1,2 Above-knee-only ablation produces markedly higher reintervention rates than extended ablation3, 4, 5 and leaves persistent below-knee reflux in 41% to 82% of limbs; midterm symptomatic recurrence is likewise lower when the entire refluxing GSV is ablated.4,6
The saphenous nerve runs in close and variable apposition to the GSV in the distal calf.7 Perivenous tumescence reduces the risk of nerve injury but does not eliminate it, and thermal ablation of this segment carries a reported risk of paresthesia of approximately 4% to 16%.8,9 Reducing power lowers this risk but couples it to occlusion efficacy, because lowering power also lowers the dose delivered to the vein wall, energy density must be interpreted together with the power used.10 We reasoned that changing how energy is delivered—rather than only how much—might separate these effects, and we propose the segmental point obliteration technique (SPOT).
Technique
Ethics
All patients gave written informed consent for the procedure and for publication of anonymized data and images. This report of a standard outpatient procedure was exempt from Institutional Review Board approval.
Setting and equipment
Procedures are performed under local tumescent anesthesia in an outpatient setting using a 1470-nm diode laser (Veincare; WONTECH) with a radial fiber selected by maximum treated vein diameter: a 400-μm fiber (BA400R; WONTECH) for veins smaller than 5 mm and a 600-μm fiber (BA600R; WONTECH) for 5 mm or larger.
Access and tumescence
Under ultrasound guidance, the GSV is accessed at the most distal point of reflux, and the fiber tip is advanced to 2 cm distal to the saphenofemoral junction. Tumescent solution (1000 mL of 0.9% saline, 20 mL of 2% lidocaine, 1 mL of 1:1000 epinephrine, and 20 mL of 7% sodium bicarbonate) is infiltrated circumferentially along the whole segment.
Two-zone protocol
The zone transition is the intraoperative level at which the vein lies within 5 mm of the skin and tumescent separation of the nerve becomes more difficult. Zone 1 (above-knee), where the nerve is anatomically distant, is treated with standard continuous pullback at 6 to 7 W (linear endovenous energy density, 60-70 J/cm); Zone 2 (below-knee) with SPOT (Fig 1).
Fig 1.
Schematic of the two-zone protocol for below-knee great saphenous vein ablation: continuous pullback in the above-knee segment (zone 1) and the segmental point obliteration technique (SPOT) in the nerve-adjacent below-knee segment (zone 2), with a magnified inset of SPOT delivery. Parameters and structures are labeled on the figure. LEED, Linear endovenous energy density; SFJ, saphenofemoral junction.
SPOT parameters
Instead of continuous pullback, SPOT delivers discrete 1-second pulses at 6 W (6 J/spot), applied eight to 10 times/cm (Table I). After each pulse, the fiber is withdrawn approximately 1 mm, and the tip is reconfirmed sonographically before the next pulse, giving an interpulse interval of approximately 1 to 2 seconds. The 1-mm spacing approximates the fiber’s effective heating diameter, producing contiguous treatment, whereas each pause allows partial heat dissipation absent from continuous pullback. This “stop-and-shoot” approach is demonstrated in Supplementary Video 1 (online only).
Table I.
Patient, vein, and procedural characteristics (13 patients, 19 limbs)
| Variables | Value |
|---|---|
| Age, years, means ± SD (range) | 58 ± 20 (31-87) |
| Female | 7 (53.8) |
| Bilateral treatment | 6 (46.2) |
| CEAP class, n limbs (C3/C4/C6) | 8/7/4 |
| Above-knee GSV diameter, mm, mean ± SD | 5.3 ± 0.9 |
| Below-knee GSV diameter, mm, mean ± SD | 3.1 ± 0.5 |
| Below-knee GSV depth from skin, mm, mean ± SD | 4.3 ± 1.3 |
| Total GSV treated length, cm, mean ± SD (range) | 59.5 ± 10.2 (30-75) |
| Below-knee (SPOT) segment length, cm, mean ± SD | 21.2 ± 3.2 |
| Radial fiber, 400-μm/600-μm, n limbs | 6/13 |
| Above-knee power, W | 6-7 |
| Below-knee (SPOT) power, W | 6 |
| Below-knee (SPOT) LEED, J/cm | 48-60 |
| Concomitant phlebectomy | 10 (76.9) |
CEAP, Clinical-Etiology-Anatomy-Pathophysiology; GSV, great saphenous vein; LEED, linear endovenous energy density; SD, standard deviation; SPOT, segmental point obliteration technique.
Categorical data are shown as number (%).
Adjunctive procedures
Residual superficial tributaries are treated in the same session by ambulatory phlebectomy when indicated.
Outcome assessment
The primary outcome, saphenous nerve paresthesia, was defined as patient-reported paresthesia, dysesthesia, or hypoesthesia in the saphenous nerve distribution, elicited by direct questioning at each visit; where reported, the affected area was mapped with a blunt point. Asymptomatic limbs underwent no routine sensory testing, and nerve conduction studies were not performed.
Results
Between January and June 2026, 13 consecutive patients (19 limbs) with symptomatic C3 to C6 below-knee GSV insufficiency underwent ablation with SPOT (Table I). Seven patients (53.8%) were women, 6 (46.2%) were treated bilaterally, and 10 (76.9%) underwent concomitant phlebectomy. No paresthesia occurred at 1 week (0/19). At 1 month, all 19 limbs showed complete duplex occlusion [100%; 95% confidence interval (CI), 82.4%-100%; Fig 2] with no paresthesia (0/19; 95% CI, 0%-17.6%). No deep vein thrombosis, endovenous heat-induced thrombosis, skin burn, or wound infection occurred (Table II).
Fig 2.
B-mode duplex ultrasound of the below-knee great saphenous vein (GSV) at the distal tibia/ankle level in a representative patient. A, Before treatment, the patent vein appears as a round anechoic lumen (arrow); B, at 1 month after segmental point obliteration technique (SPOT), the vein is occluded, with loss of the anechoic lumen (arrow).
Table II.
Outcomes and adverse events (19 limbs)
| Outcomes | Value |
|---|---|
| Paresthesia at 1 week, n/N (%) | 0/19 (0) |
| Paresthesia at 1 month, n/N (%) | 0/19 (0); 95% CI, 0-17.6 |
| Complete occlusion at 1 month, n/N (%) | 19/19 (100); 95% CI, 82.4-100 |
| Deep vein thrombosis | 0 (0) |
| Endovenous heat-induced thrombosis | 0 (0) |
| Skin burn | 0 (0) |
| Wound infection | 0 (0) |
CI, Confidence interval (Clopper-Pearson exact).
Categorical data are shown as number (%).
Discussion
In this initial series, no paresthesia occurred, and complete occlusion was achieved in all assessed limbs, suggesting that intermittent point-by-point delivery is feasible for below-knee GSV ablation.
To our knowledge, SPOT is the first below-knee GSV technique to protect the nerve by delivering energy as discrete, spaced points with interspot cooling. Existing nerve-sparing approaches reduce the delivered power or use nonthermal energy.11,12 Utoh and Tsukamoto12 reported no saphenous nerve injury after reducing below-knee power to 5 W (20-25 J/cm) with continuous ablation in 370 limbs. Because lower power and energy density may leave vein-wall injury incomplete, SPOT maintains power at the above-knee level and an energy density of 48 to 60 J/cm, altering only the mode of delivery. We hypothesize that the pauses limit cumulative thermal spread to the nerve—a mechanism this series cannot confirm—consistent with data showing that delivery mode, not total energy alone, influences vein-wall injury.13
Compared with radiofrequency ablation, which heats a 7-cm segment continuously for 20 seconds/activation, SPOT applies 1 second to approximately 1 mm, shortening continuous heating at any point.14 We believe that this further limits thermal exposure of adjacent tissues, including the nerve, but the magnitude of this effect and whether a dispersed thermal effect reduces nerve injury itself, await experimental verification.
Factors other than SPOT could account for these results. Tumescent anesthesia itself reduces the risk of nerve injury7 and was applied identically in both zones; it does not, however, eliminate the excess risk of the below-knee segment, where published series report higher nerve injury after full-length than above-knee ablation despite routine tumescence (15.7% vs 4.5% at 1 month).9 SPOT is applied in addition to tumescence and is intended to reduce that residual risk further. A single-arm series nonetheless cannot isolate the contribution of any individual component. Most patients also underwent phlebectomy, which can itself place the nerve at risk; the absence of paresthesia despite this exposure is reassuring but equally cannot be attributed to SPOT.
SPOT requires continuous ultrasound visualization of the fiber tip and should not be attempted when the tip cannot be seen. Point-by-point delivery increases operator dependence and procedural time.
Limitations
This single-arm, single-operator series lacked a control group and blinded assessment. The sample is small, with no events in 19 limbs. The exact 95% CI extends to 17.6%; therefore, a clinically relevant rate cannot be excluded. The series argues against rates as high as 15.7%9 but cannot distinguish SPOT from published rates of approximately 4%8 or establish superiority over continuous pullback. No tissue thermometry was performed, the interpulse interval was not timed systematically, and the minimum interval required to prevent cumulative heating remains undefined, so the thermal rationale remains hypothetical. Paresthesia was ascertained from symptoms and bedside examination, not nerve conduction studies, so subclinical changes would not have been detected—although published data show poor concordance between conduction measures and symptoms.15 Follow-up was limited to 1 month. Long-term follow-up is needed to confirm these results.
Conclusions
The SPOT—intermittent, point-by-point delivery with interspot cooling—was associated with complete occlusion and no paresthesia in this initial experience with nerve-sparing below-knee GSV ablation. These preliminary results support comparison with continuous pullback in larger, controlled studies.
Funding
None.
Disclosures
None.
Footnotes
The editors and reviewers of this article have no relevant financial relationships to disclose per the Journal policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest.
Additional material for this article may be found online at www.jvscit.org.
Appendix
Additional material for this article may be found online at www.jvscit.org.
Appendix (online only)
Intraoperative demonstration of the segmental point obliteration technique in the below-knee great saphenous vein. Under real-time ultrasound guidance, discrete 1-second pulses at 6 W are applied eight to 10 times/cm, with fiber-tip position confirmed before each pulse and an interval of approximately 1 to 2 seconds between consecutive spots.
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Associated Data
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Supplementary Materials
Intraoperative demonstration of the segmental point obliteration technique in the below-knee great saphenous vein. Under real-time ultrasound guidance, discrete 1-second pulses at 6 W are applied eight to 10 times/cm, with fiber-tip position confirmed before each pulse and an interval of approximately 1 to 2 seconds between consecutive spots.