Platelet-rich Plasma Improves Healing of Pressure Ulcers as Objectively Assessed by Digital Planimetry

Introduction. The effectiveness of autologous platelet-rich plasma (PRP) in chronic wounds remains controversial. Objective. The aim of this prospective study is to objectively assess the impact of PRP therapy on pressure ulcer (PU) healing utilizing digital planimetry. Materials and Methods. Eligible patients included those with PUs with a surface area > 1 cm² and > 3 months’ duration. Each ulcer initially was debrided surgically. The patient then was advised to continue conventional treatment for 4 weeks, after which time repeat debridement was performed as needed. Subsequently, PRP was applied and the patient was observed for an additional 4 weeks. During the 8-week study period, the treatment’s effectiveness was assessed weekly with digital planimetry. The Wilcoxon signed-rank test was used to compare continuous variables. Results. Thirty-six patients (22 men, 14 women) with a median age of 62 years (range, 38–88 years), who had 64 PUs with an initial median surface area of 20 cm² (range, 1 cm²–180 cm²), a median diameter of 6.3 cm (range, 1.3 cm–18.6 cm), and a median circumference of 16.8 cm (range, 4 cm–68 cm) were included. Reduction of median surface area (63% vs. 41%), median maximal diameter (33% vs. 20%), and median circumference (38% vs. 21%) were significantly (P < .001) greater after PRP treatment compared with after conventional treatment. Conclusions. It appears treatment with PRP accelerates healing of PUs as objectively measured by digital planimetry. Compared with conventional treatment, a significantly higher reduction in surface area, diameter, and circumference of PUs was observed following application of PRP.

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A chronic wound is defined as a wound that failed to reach anatomic and functional integrity through an orderly and timely reparative process within a reasonable time frame (ie, 3 months).¹ Chronic wounds, such as diabetic foot ulcers, venous leg ulcers, and pressure ulcers (PUs), occur in about 2% of the population in developed countries.² They are intractable and increasing in prevalence, representing a serious impact on patient quality of life and health care costs.

Hydrocolloids, alginates, foams, sulfadiazine silver patches, honey gauzes, and other ointments and dressings have been described to promote chronic wound healing.³ In a recent systematic review,⁴ it was unclear whether these local interventions significantly increase the probability of ulcer healing. Other interventions include hyperbaric oxygen (HBO) and negative pressure wound therapy (NPWT) systems. There is evidence that HBO and NPWT can induce and accelerate wound healing by acting on 1 or more of the wound healing steps; however, limited availability, patients’ intolerance, and high costs are among the disadvantages of these methods.³ 

The authors have developed an alternative approach based on direct exposure of autologous-concentrated plasma to the wound to enhance the wound environment. Due to its high content of platelets, this plasma is also known as platelet-rich plasma (PRP) and contains several growth factors (platelet-derived growth factor [PDGF]-AB, vascular endothelial growth factor-A, epidermal growth factor, transforming growth factor (TGF)-β1, insulin-like growth factor 1) in higher concentrations, compared with their levels in blood. These growth factors demonstrate various functions, such as inducing neovascularization, promoting fibroblast proliferation, stimulating keratinocytes, expressing regenerative epidermal phenotype, and enhancing phagocytosis and immunological response through local accumulation of polymorphonuclear leukocytes and macrophages.⁵ No significant PRP treatment-specific adverse effects have been reported, most probably because it consists of autologous products.^6,7

Despite this fact, the effectiveness of PRP in chronic wounds remains controversial, with several studies of high-evidence level reporting contradictory results. Carter et al⁶ showed in their meta-analysis that PRP therapy can have a positive impact on wound healing and associated factors, such as pain and infection, in both chronic and acute wounds. Kontopodis et al⁷ showed a significant benefit in the use of PRP in managing chronic foot ulcers in patients with diabetes with peripheral arterial disease. However, a Cochrane-based meta-analysis⁸ concluded the impact of PRP on healing of chronic wounds other than diabetic foot ulcers is unclear. This meta-analysis of 10 randomized studies,⁸ including a total of 442 patients with chronic wounds, did not show any improvement of healing when compared with standard care (risk ratio, 1.19; 95% confidence interval, 0.95–1.50). The authors found the overall quality of evidence for autologous PRP for treating chronic wounds is low due to the small number of randomized studies, which are, in addition, underpowered to detect treatment effects, if they exist, and generally at high or unclear risk of bias, including bias in outcome assessment and reporting.⁸ Inhomogeneity in assessment of chronic wounds among health care professionals is well documented.⁹ While computer-based diagnostics are established in other areas of medicine (eg, radiology, orthopedics, ophthalmology, and audiometry), accurate wound documentation is rarely conducted and often limited to size measurement with a ruler and rough photo documentation.⁹ This highlights the need of a standard technique of accurate objective evaluation of the effectiveness of PRP in chronic wounds. Digital planimetry, which is based on serial measurements of ulcer dimensions and calculation of wound margin advancement towards the center of the lesion, could be a potential method.¹⁰ The aim of this prospective study is to objectively assess the impact of PRP treatment on PU healing using digital planimetry.

Patient demographics
In the 2-year study, 43 patients with chronic PUs were prospectively recruited in the Medical School of Crete University Hospital of Heraklion (Crete, Greece). The study was approved by the local Ethics Commission and all patients provided written informed consent prior to participation. Eligible patients included those with stage 3 and 4 PUs of a surface area > 1 cm² and > 3 months’ duration. Exclusion criteria were poor general condition (ie, a Karnofsky Performance Status Scale < 60%) and significant comorbidity, such as severe or uncontrolled cardiac or pulmonary disease, malignant or premalignant marrow disorder disease (eg, myeloid leukemia or myelodysplastic syndrome), kidney or liver failure, cerebral vascular disorders, coma, intracranial hypertension, or accompanying autoimmune diseases. Patients with PUs ≤ 1 cm², very deep ulcers with cavities not feasible for assessment by digital planimetry, or facial ulcers as well as women who were pregnant or lactating also were excluded from the study. 

Wound treatment
Any associated patient comorbidities were treated as indicated to improve and optimize the patient’s general health condition. Routine laboratory tests during treatment ensured the stability of the patient’s nutritional status. Each PU was debrided surgically, and wound cultures were harvested to exclude local infection. Subsequently, the patient was advised to continue conventional treatment for 4 weeks after which repeat debridement was performed as needed. Then, PRP was injected into the margins and PU bed once weekly for 4 weeks. The PRP was prepared by centrifuging 30 mL to 60 mL of the patient’s blood with an autologous platelet separator (Magellan MAG100 Autologous Platelet Separator System; Medtronic, Dublin, Ireland) at 2000 rpm for 3 minutes and then at 5000 rpm for 5 minutes. Following the PRP application, the wound was covered with a transparent, nonadherent dressing (Tegaderm;3M Medical, St Paul, MN). During the period of PRP treatment, no local creams or dressings with potential healing action were allowed. 

Wound area measurements
During the 8-week study period, the treatment’s effectiveness was assessed weekly with digital planimetry. Digital photos were obtained with the same digital camera (Cyber-Shot DSC-W510; Sony, Tokyo, Japan) with standardized settings at a constant distance with a ruler next to the wound for scaling. Using noncommercial software “ARCHYTAS”,¹⁰ 2D digital planimetry provided objective wound area measurements from the digital images (Figure¹⁰). Several wound-related parameters, including surface area, maximal diameter, and circumference, were analyzed to calculate the wound healing rate. This process was performed independently by 2 of the authors and the average of their measurements was used. Since wound healing may begin a few days after being triggered,¹¹ reference values for the conservative treatment were the value gathered at the end of the first week. Similarly, “time zero” for PRP was considered the end of study week 5. 

Statistical analysis
The Wilcoxon signed-rank test was used to compare continuous variables. A P value < .05 was considered statistically significant. Data analyses were performed using SPSS version 17.0 (SPSS Inc, Chicago, IL).

Forty-three patients with a total of 74 chronic stage 3 and 4 PUs primarily were enrolled in the study. Of these, 2 ulcers healed during conventional treatment. During study weeks 3 and 5, there were 2 patients who died due to multiorgan failure and therefore excluded from the study. In addition, 2 ulcers < 1 cm² were excluded from any further evaluation. A total of 3 patients were lost during the study period. Consequently, the final sample consisted of 36 patients (22 men, 14 women) with a total of 64 chronic PUs and a median age of 62 years (range, 38–88).

Of the 64 PUs, 44 were located in sacrogluteal region, 10 at the heel, 3 on the tibial region, 3 on the ankle, 2 on the thigh, 1 on the abdominal wall, and 1 at the stump of a high tibial amputation. The median surface area was 20 cm² (range, 1 cm²–180 cm²), median diameter was 6.3 cm (range, 1.3 cm–18.6 cm), and median circumference was 16.8 cm (range, 4 cm–68 cm).

The effects of conventional treatment and PRP treatment on the wound surface, as well as the maximal diameter and circumference of the ulcers, are summarized in the Table. The measurements of the wound parameters performed by both investigators were similar. Reduction of all parameters was increased significantly by PRP treatment when compared with conventional treatment. Analysis with the Wilcoxon signed-rank test demonstrated a statistically significant difference (P < .001) in favor of PRP treatment. No significant adverse effects of PRP treatment were observed.

Autologous-concentrated plasma was introduced in clinical practice for applications in oral and maxillofacial surgery by Whitman et al in 1997.¹² Due to its higher than normal number of platelets, it is also referred to as platelet-rich plasma and contains mainly growth factors PDGF-AB, PDGF-BB, and TGF-β in concentrations 5 to 10 times higher than those in normal plasma.¹³ The use of calcium chloride and thrombin in gel preparation to stimulate PRP activity also has been reported, but it did not result in higher concentrations of growth factors.¹³ Derived from the patient’s own blood serum, PRP poses no concern about toxicity, cross-reactions, or immunoreactions. For these reasons, PRP may be utilized in many surgical fields, including management of chronic wounds.

Many recent studies have evaluated the effectiveness of PRP in patients with chronic wounds but with controversial results. In a meta-analysis by Carter et al,⁶ complete wound closure was more likely in wounds treated with PRP therapy, independent of the specific wound type. Moreover, in patients with chronic ulcers, PRP was proven superior to saline gauze, saline gel, and no specific topical treatment; however, a more recent Cochrane meta-analysis of 442 patients from 10 randomized controlled trials⁸ failed to prove the effectiveness of PRP in chronic wounds. The authors⁸ stated PRP may improve the healing of foot ulcers associated with diabetes, but this conclusion was based on low-quality evidence from 2 small randomized controlled trials. For the other kinds of chronic wounds (eg, PUs), there was no clear evidence for its efficacy. A major problem in assessment of the efficacy of PRP is the small number of patients included in these studies. In addition, they⁸ found a considerable risk of bias in these studies, among which bias in outcome assessment and reporting.

In the above-mentioned Cochrane meta-analysis,⁸ the total number of chronic wounds treated with PRP was 217, with a median number of only 18 wounds in the experimental PRP arm of the randomized studies included (mean wounds, 22 [range, 11–59]). Hence, it was difficult to demonstrate any statistically significant benefit of PRP treatment in each single study and even in the meta-analysis of all studies. With a higher number of wounds treated, it would be more likely to demonstrate any potential benefit of PRP treatment. To increase the number of PUs treated with PRP for assessment of wound healing parameters, the authors chose to treat each PU first conventionally then subsequently with PRP. Wound healing was assessed after each of the treatment modalities. 

Another challenge is the accurate assessment of outcomes. The conventional method of measuring the ulcers with a ruler and multiplying to calculate the total ulcer surface area is shown to lead to an overestimation of the calculated surface by 25% to 40%.^14,15 For this reason, a digital method to obtain objective user-independent measurements based on image analysis algorithms derived from 2D digital planimetry using noncommercial software “ARCHYTAS” was used.¹⁰ Digital planimetry is based on serial measurements of ulcer dimensions and calculation of wound margin advancement towards the center of the lesion.¹⁰ Computational planimetry and image processing are reliable objective measuring tools for chronic wounds as they are not dependent upon the subjective opinion of health care professionals. The only user-dependent step in this study’s methodology was the calibration scaling, determined from 2 points of known distance in the Figure.¹⁰ Since both investigators obtained similar measurements for each ulcer using the described methods, digital planimetry appears to be a reliable method to assess wound healing accurately. 

According to Fette et al,¹⁶ every tool for ulcer measurement should have 5 characteristics: (1) accuracy, ie, the ability to accurately measure the size of the ulcer; (2) validity, ie, the ability to measure what it is intended to measure accurately; (3) reproducibility, ie, the ability to reproduce the same result repeatedly; (4) interobserver reliability, ie, no evident influence from the operator; and (5) usability. Computer-assisted planimetry from 2D images is a wound measurement method that fulfills these criteria and is widely accepted. It is a low-cost procedure that does not require contact with the ulcer, unlike planimetry transparencies or the calibration liquid method.^10,16 Other effective contactless methods also have been reported, such as magnetic resonance imaging, animation imaging, and laser application.^16-19 The gold standard for ulcer measurement is the 3D digital stereophotogrammetry, which applies 3D geometry to provide stereoscopic ulcer reconstruction and determine volume. However, this is a high-cost, time-consuming method and is reported to underestimate ulcers < 25 mm² in size.¹⁷

Since 2D ulcer measurement does not consider depth, it contains a potential bias factor. Ulcers with identical surface area but varying depth have different healing rates. Deep ulcers (ie, PUs of the sacrococcygeal region) are usually round and not rectangular or oval-shaped.¹⁴ For this reason, indirect volume estimation by multiplying the surface area by depth is not reliable^14,16,18,19; therefore, deep ulcers were excluded from this study.

The authors evaluated the efficacy of PRP in 64 PUs using digital planimetry as an objective tool. The use of PRP accelerated wound healing significantly when compared with the first 4-week period of conventional ulcer treatment. Previous research showed ulcers that presented minor improvement the first 4 weeks of treatment are less likely to heal even after 12 weeks with conventional treatment.²⁰ The median surface area reduction significantly increased from 41% in the conventional treatment group in the first 4 weeks to 63% after 4 weeks of PRP, while the reduction in median diameter and median circumference significantly increased from 20% to 33% and from 21% to 38%, respectively.

In a small prospective case series,²¹ the application of PRP gel on PUs resulted in a significant decrease of wound surface area in 25 patients with spinal cord injury when compared with treatment of other PUs with standard saline dressings in the same patients; however, the wound area was not as accurately and objectively assessed — simply measuring length and width with a ruler — as in this study using digital planimetry. Histological examination of wound biopsies demonstrated increased well-formed granulation tissue and epithelialization in the majority of ulcers during PRP treatment. Clinical improvement was seen in 96% of the PUs with PRP treatment and in 68% of wounds treated with standard saline dressings. 

The costs of the PRP preparation using commercial devices may be a disadvantage of this method. However, a recent study²² demonstrated it is possible to produce PRP economically in the clinical practice setting with quality comparable to that of commercially available kits using components readily available in hospitals. Moreover, the treatment with PRP is far from standardized. The most effective way of application (eg, injection of a solution into the wound, a topical gel, or other substance) has yet to be defined. Further, commercial PRP separation systems vary widely regarding the harvest and concentration of various PRP substances.²³ An ongoing clinical study is testing a combination therapy with a gelatin sheet capable of providing sustained release of PRP in patients with various types of chronic skin ulcers.²⁴

The application of conventional local therapies (eg, patches, ointments) for 4 weeks in the study participants could have altered PRP action by stimulating or inhibiting its activity and falsifying the results; however, these agents (1) act beneficially in chronic ulcers, ie, they do not worsen the wound status prior to PRP application; and (2) they have a short half-life and, thus, short duration of action. 

Another limitation might be of the heterogeneity of location of the PUs, although most (44/64) were located in the sacrogluteal area. 

In the present study, it appears treatment with autologous PRP accelerates PU healing as measured objectively using digital planimetry. Compared with conventional treatment, a significantly higher reduction in surface area, diameter, and circumference of the wound was observed by PRP application. Further studies, preferably larger, multicenter, and randomized studies, are necessary to confirm the efficacy of PRP treatment in the healing of PUs, as well as to define the optimal PRP application method.

Authors: Evangelos Volakakis, MD^1,2,3; Marios Papadakis, MD, PhD⁴; Andreas Manios, MD¹; Christos V. Ioannou, MD, PhD⁵; Odysseas Zoras, MD, PhD¹; and Eelco de Bree, MD, PhD¹

Affiliations: ¹Department of Surgical Oncology, Medical School of Crete University Hospital, Heraklion, Greece; ²Intensive Care Unit, Venizeleio Hospital, Heraklion, Greece; ³Medical School, University of Crete, Heraklion, Greece; ⁴Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, Helios University Hospital Wuppertal-University of Witten/Herdecke, Wuppertal, Germany; and ⁵Department of Vascular Surgery, Medical School of Crete University Hospital

Contributions: Dr. Volakakis and Dr. Papadakis contributed equally.

Correspondence: Eelco de Bree, MD, PhD, Associate Professor of General Surgery and Surgical Oncology, Department of Sugrical Oncology, Medical School of Crete University Hospital, P.O. Box 1352, Heraklion, Crete 70014 Greece; debree@edu.uoc.gr 

Disclosure: The authors disclose no financial or other conflicts of interest.