Anchored index scores for EQ-5D-5L were calculated for each patient. The median score in the keystone flap group was 1.0 (IQR = 0.4) versus 0.8 (IQR = 0.3) in the SSG group. A lower score represents a worse level of health and thus there is a trend toward the SSG group having a lower overall quality of life. This difference was, however, not significant (Mann Whitney U test, z = -0.51; P = 0.641; r = 0.08).
To investigate if age plays a role in EQ-5D-5L scores, a one-way analysis of covariance was performed. After adjusting for age, no significant difference was demonstrated between the EQ-5D-5L scores in either procedural group (F = 0.47; P = 0.498). Partial eta squared for the covariant was 0.077, suggesting a small effect size and that only 7.7% of the variance in the EQ-5D-5L score is explained by age.
No significant difference in VAS was demonstrated between those who underwent a keystone flap (M = 81.8; SD = 15.3) and those who underwent an SSG (M = 77.7; SD = 17.4; P = 0.455, two-tailed). There is, however, a trend toward a higher VAS in the keystone group, suggesting a greater quality of life as seen in the index values.
Table 5 shows Patient Scar Assessment Scale (PSAS) results. A Bonferroni correction was applied to the alpha value for between-group analysis of the individual PSAS scores to reduce the risk of a type 1 error, giving an alpha of 0.008 for significance. The median total PSAS score for the keystone flap group was 11 (IQR, 10) and 13 (IQR, 14.5) for the SSG group. This was nonsignificant (Mann Whitney U test, z = 0.493; P = 0.622; r = 0.08). Questions relating to scar color (PSAS 3) and scar irregularity (PSAS 6) showed the highest median values, indicating worse results.
A significant difference between the observer POSAS scores for the keystone flap group (M = 10.9; SD = 2.4) and the SSG group (M= 17.3; SD = 3.1; P < 0.001, independent samples t test) was observed (Fig. 6).
Total POSAS scores were calculated (sum total of PSAS and OSAS scores). These were lower in the keystone group (M = 27.7; SD = 16.8) than the SSG group (M = 35.7; SD = 14.3), suggesting that keystones are more comparable to normal skin to both patients and clinical observers. This was, however, nonsignificantly different (P = 0.323; eta square = 0.08; independent samples t test).
Table 6 demonstrates the results of correlation testing between the total PSAS score, the average total OSAS score, and the EQ-5D-5L. It was hypothesized that both patients and clinicians would have similar views with regard to the outcome of surgery and that the EQ-5D-5L would have a negative correlation with POSAS scores (lower POSAS scores and higher EQ-5D-5L scores both indicate ‘better’ scar or general quality of life, respectively). A between-group analysis was also performed, investigating the relationship between PSAS and OSAS in the keystone flap and SSG groups. Both groups showed a large positive correlation between PSAS and OSAS, although this did not reach the level of significance (keystone; rho = 0.52; confidence interval = 0.08–0.79; P = 0.192 and SSG; rho = 0.52; confidence interval = 0.05–0.80; P = 0.188).
In assessing sensation between the nonoperated side and the operated side, the data were split into those people in each procedural group (keystone flap or SSG) that did or did not have a change in the categorical score on the Semmes Weinstein monofilament test between their normal and abnormal sides. This generated 4 categories (keystone – Yes, keystone – No, SSG – Yes, SSG – No), which were compared in a two-by-two table using the Pearson chi-square test (Table 7). Significantly fewer people in the keystone group experienced a reduction in sensation compared with their normal side, indicating a strong association between the type of procedure and the reduction in sensation compared with the normal side (chi-square = 7.61; P = 0.006; phi = -0.79).
Table 8 shows the results of the Courage and Khazaka data. No significant difference between keystone flaps and SSGs were demonstrated in any of the objective parameters measured. There was, however, a trend toward SSGs being firmer that keystone flaps (keystone Q0 = 17.8 versus SSG Q0 = 5.5). Furthermore, both demonstrated a reduction in their trans-epidermal water loss, but an increase in hydration in the stratum corneum.
There were 2 complications in the keystone group (10%) and 7 in the SSG group (39%). There was 1 infection in the keystone group, successfully treated with oral antibiotics and 1 hypertrophic scar. In the SSG group, 2 people developed infections, with 1 graft overgranulated and 4 grafts partially or completely failed.
Excision Rate and Detection of Recurrence
One lesion was incompletely excised in the SSG group, with no incompletely excised lesions in the keystone group. There was 1 recurrence in the SSG group and none in the keystone group. A Fisher’s exact test was used to examine this relationship between these results and the type of reconstruction, with no evidence of a relationship (P = 0.474, respectively).
Cost Analysis of Keystone Flaps and Split-thickness Skin Grafts
Costs were calculated to include time in theater, type and amount of anesthetic, equipment used, sutures, dressings, and follow-up appointments in the dressing clinic until the wound was healed (defined as the point where the wound could be managed without dressings at home by the patient which equated to a mean of 1.5 weeks for a keystone flap and 5.6 weeks for an SSG; Table 9). There was an average cost saving of £208/$268 (19.7%) in the keystone flap group versus the split-thickness skin graft (keystone flap = £850.94; SSG = £1059.45; P = 0.389, independent samples t test).
The benefits of the keystone flap have been well documented for the reconstruction of defects in range of topographical areas,5–7 , 9 , 11–13 although there is little objective or patient-reported outcome data comparing them to SSGs. This study aimed to generate pilot data to address this. Key outcomes are documented in Table 10.
There was a trend toward an inferior quality of life in the SSG group versus the keystone flap group, with lower median scores in both the EQ-5D-5L and EQ-5D-5L VAS in the SSG group. It is of note that only 7.7% of the variance in EQ-5D-5L score was ascribed to age.
It was hypothesized that the POSAS would provide a greater ability to differentiate between reconstruction type, given its focus on scarring. Again there was a trend toward “worse” scarring in the SSG group, reflected by a higher median total patient component of the POSAS. Scar color and irregularity showed the greatest difference between the operated side and the normal skin from a patient perspective. Although the EQ-5D-5L and POSAS scores all showed a trend toward worse results for the SSGs versus the keystone flaps, statistical significance was not achieved.
For the clinical observer, our results show that statistically, the keystone flap is aesthetically and functionally preferable, with the observer component of the POSAS demonstrating a significantly lower score in the keystone group.
Significantly, fewer people in the keystone group experienced a reduction in sensation compared with the normal side and there was a trend toward keystone flaps being firmer than SSGs. These findings are important as a lack of protective sensation and thinner, less robust soft-tissue coverage, may result in acute injury or wound breakdown from frictional forces or direct trauma.
Cost analysis demonstrated that the average keystone flap costs £158 ($207) less than an SSG (a 15% saving). In an era of prudent healthcare, a reliance on rationing of healthcare resources and the growing incidence of skin cancer, there is a large health economic benefit to consider.
Although subjective and quantitative data suggest a trend toward better overall outcomes with a keystone flap versus SSGs, the lack of statistical significance is likely due to a number of factors. The low power, due to a modest cohort size and the need for nonparametric statistical analysis, makes it difficult for the results to reach significance. It is also likely that our patient population, generally elderly, with a significant number living in a semirural setting, suffering from cancer, is not overly concerned by the aesthetic or functional outcome of their reconstruction. This is suggested by the majority of patients scoring the lowest category possible (1 out of 10) for a large number of the PSAS questions. It is likely that this age group is less concerned with the factors asked in the POSAS questionnaire than younger patients might be. It is our belief that in a younger population, living in major cities, with higher expectations, that these results would be different. We also note a significant difference in the average age between both groups. This is likely to represent unconscious bias on the part of the clinical team when recommending different treatment options and is something to address in a future, prospective study.
Despite being a small cohort it is important to note that no keystone flaps failed, whereas 4 SSGs experienced either partial or complete loss. This lower complication rate is an important finding and one that should be discussed with patients.
Trends identified suggest that a fully powered, prospectively collected data set is warranted. Both EQ-5D-5L and POSAS questionnaires functioned well and were easy to administer. Similarly, sensation was easy to measure and provided useful information. We, however, feel that the collection of objective data using the Courage and Khazaka adds considerably to the cost and complexity of the study without significant benefits and as such would suggest this is not included in future protocols.
The limited cohort size available in this retrospective study limited its statistically power and the conclusions that can be drawn. However, a trend toward greater patient satisfaction, better appearance, and cost savings to the health provider of keystone flaps over SSGs was seen. The development of a larger, prospectively designed trial is now required to fully evaluate the difference and provide evidence-based treatment that is preferential to our patient population.
The authors would like to acknowledge the support of Enviroderm, (the UK supplier of Courage and Khazaka equipment) and Steve Atherton for Figure 1.
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Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Society of Plastic Surgeons. All rights reserved.
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