Intraoperative Radial Fiber Cap Loss, a Rare Complication of Endoluminal Therapy

Keywords

endoluminal therapy - laser therapy - laser probe complication - varicose vein surgery

Introduction

Endoluminal thermal ablation of truncal varicosis of the great saphenous vein and the small saphenous vein using laser or radiofrequency techniques is widely used worldwide and has been well documented in the literature since 1999 [1]. An advantage of the procedure is the low complication rates and the low postoperative discomfort of patients [1]. The errors reported in the USA for endoluminal therapy/stripping procedures (various laser systems, radiofrequency catheters, vein stripping) are listed in the freely accessible Maud database (Maude Adverse Event Report: Symmetry Surgical, Inc, Symmetry Vein Stripper (fda.gov). Here, problems are found numerically more frequently with radiofrequency techniques than with laser systems. Recently, Scholl and Leitz [2] described such a case in the journal Phlebologie.

Case report

We report below a rare complication of endoluminal thermal laser ablation that has not been previously described for this type of laser and fiber.

A 52-year-old man with a BMI of 28.4 underwent thermal ablative treatment of an insufficient left saphenous vein using a 1470 nm laser with single-ring radial fiber (1470 nm Laser Leonardo and ELVeS Radial fiber, Biolitec, Germany). The laser probe was inserted from the inside of the knee after careful inspection for integrity and advanced up to the saphenofemoral junction zone in a duplex-controlled fashion. The laser probe tip was placed at a distance of 1.1 mm ([Fig. 1]) from the femoral vein.

Fig. 1 Placement of the radial laser probe in the saphenofemoral junction zone; distance to the roof of the femoral vein is 1.1 mm.

The application of the TLA solution cooled down to 4 degrees Celsius was performed in a duplex-controlled manner using a 0.9 × 70 mm cannula (20 G). Ninety-five ml of tumescent local anesthetic (TLA) solution was injected at the saphenofemoral junction, and 382 ml of TLA was injected at the saphenous trunk of the thigh. In addition, another 280 ml of TLA was applied in preparation for a miniphlebectomy in the area of side branch varices (total amount 775 ml).

The set laser power was 10 watts. The proximal 3 cm of the great saphenous vein were treated with a total of 551 joules, i.e., 183 J/cm, following the recommendations of Spreafico et al [3] and Hartmann et al [4]. Hereafter, the probe was continuously withdrawn with an average energy of 84.4 J/cm. The total treatment distance was 33 cm, and the total energy delivered was 2919.9 joules. The treatment time was 55.4 sec at the saphenofemoral junction and 292.5 sec in the saphenous trunk.

Sticking of the laser probe tip in the segment of the great saphenous vein near the orifice, which we frequently observe and which we counteract from the second centimeter distal to the crosse by gently moving the laser probe tip back and forth while delivering energy, was not present in this case. After the proximal 3 cm of the great saphenous vein was treated with 3 complete cycles totaling 551 joules, continuous retraction of the radial laser probe was performed with the patient in the head-down position to the puncture site at the medial knee without intraoperative features. Postoperative inspection of the laser probe tip revealed that the proximal segment of the optical fiber was missing, over the length of 1 cm. Clinically, the patient offered no abnormalities. A subsequent repeat Doppler examination was technically difficult to assess due to the infiltrated amount of TLA.

However, a 4-mm-long echo-rich district was seen approximately 5 mm distal to the saphanofemoral junction and then an 8–10-mm-long echo-rich district was seen mid-thigh. To rule out embolization, although unlikely, we ordered a CT scan of the thorax, abdomen, left groin, and left thigh. The examination revealed no pathologic abnormalities. Since the endoluminal surgery was performed late in the afternoon, the CT diagnostics were not completed until about 10:00 p.m., and the patient offered no clinical abnormalities, we did nothing more that evening and waited for the TLA solution to resorb until the following morning and then repeated the duplex diagnostics. The groin showed the same findings as the previous evening. In the middle of the thigh, the double contour of the glass fiber could now be clearly detected ([Fig. 2]).

Fig. 2 Detached probe tip of the radial laser probe mid-thigh 1 day post-op.

Thereupon, in consultation with the patient, we excised the probe tip in the thigh, which was possible without any problems ([Fig. 3]).

Fig. 3 Detached laser probe tip mid-thigh intraoperatively.

After it then became apparent intraoperatively that parts of the glass sheath were missing from the detached probe tip ([Fig. 4]), which corresponded in size to the 4-mm, echo-dense finding in the crosse region described by duplex sonography, we decided to additionally explore the crosseregion.

Fig. 4 Tip of the laser probe with glass defect in the roof area.

The then possible intraoperative evidence of discontinuous carbonization reactions of the treated great saphenous vein with intervening rough vein segments we consider as additional evidence that the probe tip had broken in the crosseous area ([Fig. 5]).

Fig. 5 Intraoperative crosse findings with central ligation. Normal postoperative laser aspect in the central 1 cm saphenous segment. Then distally complete carbonization of the great saphenous vein.

The immediate crosseregion shows no signs of carbonization. These are seen only about 1 cm distal to the junction of the great saphenous vein with the femoral vein. Consequently, the probe tip has experienced partial damage at this level. The probe tip did not tear off until mid-thigh. We performed a correct, level crossectomy [5]. The surgical procedure corresponded to that of a recurrent crossectomy, i.e., the femoral vein was dissected proximally and then distally to the saphenous vein orifice. The saphenous vein was then double ligated with Ethibond at the same level as the femoral vein without touching the central saphenous vein segment, and the saphenous vein was resected distally over a length of 5–7 cm and preserved for histopathological examination. Palpatory findings were unremarkable in the proximal 8-mm-long saphenous vein segment that was double ligated. In particular, we could not palpate any glass particles in the great saphenous vein crosse. Histopathologically, no glass remnants were detectable either.

Histopathologically, the crosseregion showed necrobiosis of the vein wall as well as transection of the vein wall ([Fig. 6]).

Fig. 6 Rupture of the vein wall, as known from studies on barefiber-treated veins.

Discussion

To our knowledge, this is the first publication of an intraoperative detachment of the probe tip of a radial fiber for endovenous thermal laser ablation. According to Biolitec, there is no other reported case of such a complication with the ELVeS Radial 1ring fiber used.

In contrast, complications due to lodged sections of other types of lasers and fibers have already been described [6] [7].

What can be considered as the cause of such damage to a radial fiber? There are two scenarios to be discussed here:

According to the manufacturer, a “lack of mechanical integrity of the fiber before usage (perhaps due to transport damage or mishandling during unpacking and preparation of the fiber before use”) is to be considered. In our case, we can largely exclude this due to our routine, careful preoperative inspection of the laser fiber.

On the other hand, intraoperative damage to the fiber is possible.

The destruction of the probe tip observed here due to mechanical effects (pulling on the probe or damage to the probe by the injection needle) is extremely unlikely.

Intraoperatively, during the application of the tumescent local anesthetic solution by the injection needle described above in the crosse area, contact of the needle tip with the glass envelope of the laser probe occurs more frequently. Under the premise that the laser probe tip is almost completely in contact with the vein wall in the trendlenburg position, and the vein as such is embedded in a surrounding fluid bed of a large amount of TLA solution, intraoperative contact of the injection needle with the laser probe tip, which occurs in a dosed manner, is seen to yield to the needle contact. Destruction of the glass tip by such a maneuver is inconceivable. Also, the manufacturing company, to which we handed over the defective probe for the analysis of the damage process, comes after subtle diagnostics to the result, "that the blasting off of the dome roof mechanically by the tumenescence needle is to be doubted very much". Such a mechanism would have to lead to such complications much more frequently, given the presumed frequency of conscious or unintentional contact of the needle with the laser probe tip. However, this is defacto not the case. This is the first description of such a complication. The situation is completely different when the injection needle comes into contact with the vulnerable laser fiber. Contact of the injection needle with the laser fiber should be avoided at all costs. In this case, detachments of the optical fiber have been described intraoperatively [8] [9].

Also, in vitro experiments we performed after the laser probe detachment described above show that damage to the glass envelope of the laser tip cannot be achieved using the 20 G puncture needle. We repeatedly tried to damage the laser probe tip on a hard surface (metal instrument table, desk) using the 20 G needle. This did not succeed. The needle slips very easily on the glass envelope, so damage per se is not possible. Even if one presses the tip of the needle into the glass or tries to drill into the glass by turning the needle, a procedure that is never performed intraoperatively, it is not possible to damage the tip of the glass even with massive pressure against a hard surface, and here too there is ultimately a difference from soft tissue intraoperatively – here the laser probe tip floats in the vein or in the surrounding tumescent solution. In this respect, the purely mechanical idea that the laser tip is shattered by the injection needle is certainly very unlikely. This statement is also supported by the manufacturing company.

Hypotheses on the damage process of the laser tip:

1. In the case of optical waveguides, and especially in those probes that deflect and reshape the beam, great care must be taken to ensure that the optical structures that deflect and shape the beam absorb the beam only slightly. Because of the very high intensities, even small spots of absorption (impurities that cannot be seen by the human eye) in the glass can heat the material to a significant degree. This leads to melting and subsequent destruction of the glass material and detachment of the glass dome. Once the dome is detached, the concentric beam exits the probe, since it is no longer converted by the Axicon structure into a “harmless” beam with low intensity. After the roof of the laser probe, which is about 4 mm long and about 1 mm wide, flaked off, the laser has completely changed its laser properties. In connection with the then also occurring “contamination” of the exit surface with body fluids, the absorption of the laser radiation increases further and can lead to a complete destruction of the probe, which obviously is what happened. The laser has thus developed properties that are comparable to those of a barefiber in the broadest sense. This is evidenced by the carbonization phenomena of the saphenous segment near the cross ([Fig. 5]), as well as the histology with typical rupture of the vein wall ([Fig. 6]). The completely altered laser properties then caused the tip of the laser probe to melt off at the weld approx. 20 cm below the groin, i.e., after delivery of approx. 2000 joules of energy.

2. Alternatively, the following damage mechanism is also conceivable: If the probe tip was manufactured using a glass fusion process, it is also possible that stresses are introduced into the glass during this process (in very rare cases) and then these glass structures become very sensitive to heating, but also to slight mechanical stresses. Only the manufacturer can answer whether such a damage mechanism is possible or has occurred. He knows his manufacturing process very well.

A simple form of quality control of the probe could be to briefly apply a significantly higher power to the probe before use and then visually check whether the probe has been damaged. However, this is clearly the responsibility of the manufacturer and not the user. In addition, the user who acts in this way exposes himself to the accusation that any destruction of the probe that may occur was only caused by the power being too high and not in accordance with the specifications.

The above-mentioned hypotheses are based on an intensive discussion of the facts with a renowned laser physicist of a German university, who explicitly asked not to be named. His damage hypothesis is based on the Fig. 1–6 sent to him and the operational procedure described by us). Like the manufacturer, the laser physicist concludes that the observed destruction of the probe was probably not caused by mechanical influences (pulling on the probe or injury to the probe by an impinging injection needle).

After intensive testing, the manufacturing company to which the used probe was provided concludes that an unfortunate chain of effects, which can no longer be traced, led to the partial detachment of the distal quartz glass cap. The essential aspects of this multi-page test report are summarized below:

“we use pure quartz glass as the material for the fiber core, this glass is also used for high power laser with power of 4–8 KW, the commonly used power of 10W is very low for the material. The breaking point of the fiber cap has sharp edges, thus the melting of the glass can be excluded with certainty. The fiber was subjected to a tensile test of 100 kpsi during manufacture, so the contamination of the surface of the fiber can be excluded, otherwise the fiber would have broken during the test. The fiber itself has no welded seam. The cap and the fiber are made of the same high purity fused silica. Furthermore, the fracture site does not show any melted off areas. Softening/melting of fused quartz occurs at approximately 1600° at the earliest. The clear smooth edges indicate spalling. In our opinion, the break-off you assume occurred due to a very unfortunate break-off of the glass dome roof. In the course of the laser action, a light leakage occurred at the transition from the glass fiber to the rigid glass cap. We assume that initially there was a break in the cap and that this crack led to a detachment of a part of the roof and the formation of a micro-gap. Liquid penetrated through this gap. This was followed by laser power leakage in the transition area between the remaining fused silica cap and the fused silica fiber. In the course of the distal thigh, the cap came off or the cap was pulled off the fiber. The now naked glass fiber no longer has any light conducting property so that more and more energy was pulled out in the transition region of liquid. We dare to doubt very much whether the blowing off of the dome roof is mechanically possible by the tumescent needle and we agree with the authors here. The case was closely examined, and no anomalies were found in the manufacture and testing of the probe in question. The darkening of the adhesive at the junction between the cap and the optical fiber indicates that the adhesive was very hot during the process, but it is not possible to determine whether the overheating caused the probe to fail or whether the overheating occurred after the failure. Due to effects, we can no longer trace, partial loss of the fused silica cap occurred due to the dome roof blowing off. Micro-cracks then led to the formation of light absorption in the quartz glass composite, resulting in the failure of the joint.”

Histologically, there was rupture of the vein wall after crossectomy, as has been shown with the use of barefiber [10]. Whether the missing roof of the laser tip was melted away or blown off by the altered properties of the laser remains unanswered. We found no glass remnants either palpatorily or histologically. The fiber tip did not detach until midthigh. This indicates that the weld seam between the laser tip and the glass fiber only became detached due to the altered radiation of the laser.

Holdstock et al. [9] already demonstrated damage to the laser fiber in vitro experiments with an 810 nm laser system (Varilase) using a 21 G needle in 2008. Damage to the glass tip of a radial laser probe has not yet been described.

In summary, the following conclusions can be drawn from this case (see also [11]):

1. Pre- and especially postoperatively, the integrity of the laser fiber should be checked.

2. If postoperative defects of the laser fiber appear, sonographic detection of blown-off glass particles in the treated vein may be difficult due to the applied TLA. Therefore, repeat sonography is indicated after the TLA has been drained off.

3. Duplex diagnostics were superior to CT diagnostics in the case described here.
   The manufacturing company recommends the following procedure:
   What to do after localization of the position of the cap?
   If the cap is in junction area and the junction is open proximal to the cap, consider whether to perform a ligation cranial to the cap and possibly the surgical removal of the cap itself.
   Balance the difficulty of ligature and the risk of displacement of the cap in the venous system.
   If the cap is in the trunk, included between occluded vein segments, up and down, or in a perforator, there is no risk of embolization into the venous system.
   If the cap is in a favorable position, for example: superficial in a thin, skinny patient palpable through the skin, the cap can be easily removed, through a small incision, under local anesthesia and ultrasound guidance.
   Conversely, in a disadvantageous position, for example: deep, near to the junctions or nerves in an obese patient, the cap can be left, and the patient should be warned that he has a small inert foreign body, which will probably be asymptomatic, has a modest chance to move because it is embedded in a scar and removal can create more problems than benefits. If the cap is not removed, it is indicated to explain to the patient what the signs and symptoms of deep vein thrombosis, pulmonary embolism, and cap dislocation may be, so that in case of a suspect he can be quickly reassessed.
   What to do if the cap could not be identified?
   Patients should be warned that it was not possible to locate the cap fragment with the X-ray and ultrasound (also indicating the possibility that it is not within the limb as was assumed) and it is necessary to wait a few months in order to be able to detect the body's reaction (foreign body granuloma), which should help locate the fragment and eventually remove it. The fragment is small in size, of an inert material (quartz) and, in the formation of granuloma, is blocked within the inflammatory tissue. Therefore, there are no particular dangers in this waiting time. In addition, the inflammatory reaction around the foreign body could cause a nuisance that could help to better focus on the search for the foreign body in the limb.
   Our therapeutic procedure can certainly be discussed diversely. It is by no means mandatory to follow the manufacturer's recommendations listed above in English.
   It would certainly have been wrong to do nothing and not inform the patient about the complication that occurred during the procedure.
   Whether the torn probe tip could not have been left in situ must be clarified with the patient in each individual case. We had informed the patient that the probe tip was superficial and could be easily removed surgically with little risk. Our advice to the patient was to remove the foreign body and to accept an approximately 1.5 cm long scar.
   Waiting and leaving the foreign body in situ, according to the manufacturer's recommendations, combined with the need for repeated sonographic controls, may be possible in principle. We have decided against this.
   In our view, the decision to re-explore the inguinal region is completely uncontroversial. The intraoperative aspect of broken glass particles from the roof of the probe tip in the immediate vicinity of the saphenofemoral junctional zone and the risk of possible carryover of foreign body material to the central region made open surgical intervention with performance of a level crossectomy imperative.
   The authors suggest that this rare complication be included in the appropriate surgical education protocols.

Conclusion

The authors describe for the first time the intraoperative detachment of a laser probe tip during endoluminal therapy of truncal varicosis. This complication was not caused by faulty medical action. A causal relationship between the clinically not so rare contact of the tumenescent needle with the laser probe tip and the very rare complication described here, is as described above, extremely unlikely. The different treatment options resulting from this are discussed. The authors have decided on an open surgical approach.

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