This research was funded by the Department of Anesthesiology, LSU Health Sciences Center—Shreveport.

Presented in part at the Joint International Laser Conference, September 21-23, 2003, Edinburgh, Scotland.

Background and Objective

Scar pain may persist chronically after surgery or accidental trauma. Entrapment of neurons by collagen has been considered the most probable cause.₁ Treatment has included infiltration with local anesthetic agents, steroids, electrical stimulation, and needles, all of which usually provide only short-term relief. An incidental finding in a study of cosmetic laser treatment of scars showed significant pain relief for four patients who also had pain.₂ The objective of this study was to examine the effect of a single treatment with an erbium:YAG laser on chronic scar pain.

Study Design/Materials and Methods

After approval by the IRB at LSUHSC-Shreveport and informed consent, 23 patients with a history of chronic (>3 months) scar pain were studied. Demographic data collected included age, weight, height, sex, Fitzpatrick Scale (skin color), type of injury (accidental vs surgical), and location of scar. The Fitzpatrick Scale assesses skin color: A score of 1 represents very light skin, and a score of 5 represents very dark skin. Baseline assessments included McGill Pain Score (Figure 1), including sensory and affective pain descriptors, VAS pain scale, VAS itching scale, and a 5-point numerical intensity scale (0=none, 1=mild, 2=discomforting, 3=distressing, 4=horrible, and 5=excruciating).

Figure 1

Figure 1: McGill Short Form.3 Yellow are sensory attributes; orange are affective attributes.

All patients were treated with an Er:YAG laser (NaturaLase™, Focus Medical, Bethel, CT)(Figure 2), wavelength 2.94 nm, fluence 1.29 J/cm², spot size 8 mm, with 2 pulses per second, and 50% overlap. Assessment was at one month and four months post-procedure. Data were analyzed with repeated-measures analysis of variance, and a priori level of significance was defined at p<0.05.

Figure 2

Figure 2a: NaturaLase™ Erbium:YAG Laser

Figure 3

Figure 2b: NaturaLase™ Erbium:YAG Laser Handpiece

Results

For the study population, age (mean±SEM) was 42±2, 14 females, 9 males, 16 with surgical scars, 57 with accidental scars. All scars were non-erythematous and flat. Duration of scar pain was 8.2±2.0 years. Other population variables are shown in Table I.

Figure 4

Table 1: Patient Population

At both one month and four months after treatment, McGill Scale decreased (p<0.001) (Figure 3), pain VAS decreased (p<0.001) (Figure 4), itching VAS decreased (p<0.05) (Figure 5), and intensity decreased (p<0.001) (Figure 6).

Figure 5

Figure 3: Effect of Erbium:YAG Laser on McGill Pain Scale

Figure 6

Figure 4: Effect of Erbium:YAG Laser on Visual Analog Pain Scale

Figure 7

Figure 5: Effect of Erbium:YAG Laser on Visual Analog Itch Scale

Figure 8

Figure 6: Effect of Erbium:YAG Laser on Intensity Scale

McGill affective scores did not change significantly during follow-up (1.0±0.4 to 0.6±0.3); McGill sensory scores decreased significantly (p<0.05)(Figure 7).

Figure 9

Figure 7: Effect of Erbium:YAG Laser on McGill Sensory Attributes

There was no effect of type of injury (accidental vs surgical) or scar location. Men were taller (p<0.05), darker (p<0.05), and perceived more baseline pain (p<0.05) than women (Table II).

Figure 10

Table 2: Sex Differences (All at p

Discussion

When Manuskiatti, et al, studied the cosmetic effects of lasers on scars, they noted in passing that four of the patients they studied had complained of scar pain prior to the cosmetic treatment, but that after the treatment, the scars not only looked better, but the pain had vanished.₂ They used a 585-nm pulsed-dye laser in their study. Kotani, et al₁ hypothesized that nerve ending were entrapped by the formation of scar, causing the scar pain. If this is true, the laser could be simply destroying the collagen and causing it to regrow in a manner such that it no longer constricts the nerve ending. Recently, Martin has proposed that the laser may reduce directly chronic inflammation at the cellular level.₄ Whatever the physics and physiology, cosmetic lasers are ubiquitous, and their potential application by anesthesiologists and pain medicine specialists to treat chronic scar pain represents a real breakthrough in this difficult area of pain medicine.

Conclusion

The Erb:YAG laser shows significant promise as a treatment modality for chronic scar pain.