Introduction. Detailed understandings regarding the outcomes and characteristics of healing in wounds of different etiologies are lacking. Objective. In the present study, data on 265 patients treated at an outpatient physical therapy wound care clinic were extracted. Methods. Using Kaplan-Meier analyses, wound healing outcomes for different wound etiologies were evaluated and compared. Results. The results revealed venous leg ulcers (VLUs) healed faster than non-VLUs, pressure ulcers (PUs), diabetic foot ulcers (DFUs), and arterial wounds but not faster than surgical and traumatic wounds (STWs). The estimated medians (mean for arterial wounds) of total treatment durations for complete wound closure were 87, 152, 100, 170, 525.44, 773 days in VLUs, non-VLUs, STWs, DFUs, arterial wounds, and PUs, respectively. Compared with patients with VLUs, patients with non-VLUs were younger (69.72 vs. 61.35, respectively), had a higher proportion of men (odds ratio [OR] = 2.26), were less likely to have more than 1 wound (OR = 0.25), reached complete wound closure upon discharge (OR = 0.41), or had a body mass index value greater than or equal to 25 (OR = 0.39). Conclusions. Venous leg ulcers and other wound etiologies (ie, STWs, PUs, DFUs, and arterial wounds) appear to differ in wound healing outcomes and certain characteristics. These results may be of interest to clinicians, patients, health care policy makers, and insurers. Future research is warranted to compare wound healing outcomes and patient characteristics among different settings.

Wounds, both chronic and acute, arise from a variety of etiologies and may present with a multitude of complications and dilemmas for patients and health care providers. Wounds become chronic when the normal wound healing process is disrupted by aging or by pathophysiologic or metabolic factors. Wounds can impair mobility, activities of daily living, and quality of life in patients, and wound care treatments, especially those that are chronic in nature, can be time consuming, arduous, and expensive.¹ 

Current methods being used to treat chronic wounds include negative pressure wound therapy, debridement, local antibiotic therapy, and moist dressing application.² Other widely used advanced therapies include bioengineered skin substitutes, electric stimulation, materials that repair tissue (platelet-derived and autologous growth factor), ultrasound, ultraviolet C, compression, and offloading strategies.² Wounds of different etiologies receive varied treatments to meet the complexities of each wound type, and, as a result, specific treatments usually differ in patients; often, patient comfort/tolerance and costs of care are significant factors in selecting wound treatments.³ In the United States, professions involved in chronic wound care, under the supervision of physicians, include physician assistants, nurses, and physical therapists.

Previous studies^4,5 have indicated that outpatient physical therapy for wound care could be cost effective and heal wounds in a timely fashion. However, due to the strict inclusion and exclusion criteria, the 2 research studies only included data on 159 of 261 (60.92%) patients.^4,5 Furthermore, wound healing outcomes and patient characteristics for wounds of different etiologies were not analyzed in the previous studies.^4,5 

Based on etiology, wounds are often categorized into venous leg ulcers (VLUs), pressure ulcers (PUs), diabetic ulcers, arterial wounds, burns, and others (eg, surgical wounds, wounds due to traumatic injuries). Venous leg ulcers constitute the most common type of chronic wounds in outpatient settings, accounting for 70% to 90% of ulcers found in the lower extremity.⁶ Pressure ulcers are caused by localized injury to the skin and/or underlying tissue (usually over a bony prominence) due to prolonged pressure and/or shear force and friction.⁷ Risk factors for PUs include age, stroke, diabetes, dementia, spinal cord injury, and impaired mobility or sensation.⁵ Diabetic foot ulcers (DFUs) usually are caused by neuropathy and repeated mechanical injury or trauma,⁸ and arterial wounds are caused by compromised arterial circulation.⁸ Surgical and traumatic wounds (STWs) usually heal in a timely fashion, but the chance of these wounds becoming chronic increases when patients have multiple medical comorbidities, poor wound care management, or infection.⁹

As wound characteristics, including pathophysiology, and corresponding treatments can vary in different types of wounds, the wound healing outcomes (probabilities of and time to reach complete wound closure [CWC]) likely differ among wounds of different etiologies. This information can be of value for patient education, prognostic planning, and judging the effectiveness of wound care. According to the US Food and Drug Administration and the Wound Healing Society,¹⁰ CWC has been suggested as the most stringent criterion to determine efficacy for a new wound healing agent. Time to reach CWC and total treatment duration (from initial evaluation to patient discharge) can significantly impact the patient’s quality of life, which speaks to the importance of these measures.

The purposes of the study were to: (1) depict and compare wound healing outcomes (ie, probabilities and total treatment durations) for CWC in all wounds of different etiologies treated at an outpatient physical therapy wound care clinic; and (2) explore the characteristics of wounds of different etiologies as well as patient demographics and wound history.

This retrospective study was conducted at a physical therapy wound clinic in Amherst, New York. The study protocol was approved by the Human Subjects Research Review Committee at Daemen College, Amherst, New York. Deidentified patient data were extracted for patient demographics and wound history, including body mass index (BMI), sex, age, treatment results, living conditions, marital status, wound duration at initial evaluation, number of comorbidities, treatment duration, pain, wound status, and etiology.

Upon data extraction, wound status was coded as either CWC or open. Complete wound closure was defined as 100% closure of the wound and, if more than 1 wound was present, 100% closure of all wounds; otherwise, the wound healing status was coded as open. Because researchers tend to define hard-to-heal wounds as wounds that usually have a duration greater than 6 months, wound duration at initial evaluation was dichotomized into less than 180 days and greater than or equal to 180 days in the present study. If a patient had more than 1 wound, wound duration at initial evaluation was based on the wound with the longest time elapsed before treatment; the total treatment duration refers to the overall length of patient treatment from initial evaluation through the patient’s last visit. As a clinical routine, all patients were treated at the clinic for 1 or more visits after CWC to prevent wound relapse and to fit the compression sock(s) if the patient had VLUs; admittedly, wounds continue to heal after CWC. For convenience, the total treatment duration from initial evaluation to patient discharge after CWC, not the time to reach CWC, was used as events in the Kaplan-Meier analyses in this study. The authors then used patients with VLUs as reference and compared wound healing outcomes and characteristics of wounds of different etiologies (non-VLUs as a whole and then various individual wound etiologies).

Treatment of patients
With the exception of patients with superficial VLUs, all other patients in the present study received electric stimulation in the form of high-voltage pulsed current electric therapy (Winner EVO ST4; Richmar) with 120 pps, 100 mA, continuous wave for 45 minutes usually twice weekly. The intensity of electric stimulation strength was adjusted based on patient tolerance. Occasionally, whirlpool therapy, ultrasound therapy, and ultraviolet therapy were used based on the clinician’s evaluation. Collagen- and silver-based dressings were commonly applied. Additional treatments included topical antimicrobial dressings, such as iodine-based ointment, and debridement by physical therapists who were not independent of this study. Compression dressings, in conjunction with the Unna boot, were used to treat VLUs when appropriate (with an ABI ≥ 0.7). Patients usually visited the clinic 2 to 3 times per week.  

Statistical methods
Patient demographics and wound treatment history are summarized and described in the Table. Quantitative data were expressed as mean or median when appropriate. The non-VLU group included all patients with a wound etiology other than VLU. Patient ages were compared between the VLU and non-VLU groups using t tests. Age comparisons between VLUs and wounds of other specific etiologies and comparisons of treatment durations were performed using Mann-Whitney U tests. Categorical data were summarized and compared using Fisher’s exact tests with odds ratios (ORs). Kaplan-Meier analyses were utilized to depict the percentage of patients discharged with wounds completely closed against total treatment duration (days) and to compare the wound healing outcomes between VLUs and wounds of other etiologies. A two-tailed P value < .05 was considered statistically significant. Statistical analyses were performed using SPSS Statistics for Windows (Version 17.0; SPSS Inc).

From September 10, 2012, to April 6, 2015 (data extraction), 267 patients were treated at the outpatient physical therapy wound care clinic; 2 of the 267 patients were treated for non-wound-related disorders and were not included in the analysis. In total, 265 patients (131 females, 134 males; mean age, 65.17 ± 16.13 years) were included in the present study. Among these patients, 22 continued to visit the clinic regularly upon data extraction; all of their wounds were coded as open.

Among the 265 patients, 121 (45.66%) had VLUs and 144 (54.34%) had wounds of other etiologies (non-VLUs), including 63 (23.77%) patients with STWs, 31 (11.70%) with DFUs, 24 (9.06%) with PUs, 17 (6.42%) with arterial wounds, 6 (2.26%) with pilonidal cysts, 2 (0.75%) with skin cancer, and 1 (0.38%) with burns (Figure 1). Due to the small sample sizes for pilonidal cysts, skin cancer, and burns, wound healing outcomes and wound characteristics were not analyzed in these individual wound categories but rather included in the overall non-VLU group. 

Wound healing outcomes
The Kaplan-Meier analyses depicted the wound healing outcomes for wounds of different etiologies (non-VLU group). As indicated by rough estimates shown in Figure 2 and Figure 3, the probabilities of patient discharge after CWC plateaued at 18% at 100 days for arterial wounds, 32% at 280 days for PUs, 42% at 190 days for DFUs, 82% at 280 days for STWs, and 84% at 300 days for VLUs, as well as 66% at 270 days for non-VLUs when wounds were categorized into VLUs and non-VLUs only. Based on the total treatment duration depicted by the Kaplan-Meier analyses (Figure 2, Figure 3), VLUs healed faster than non-VLUs, PUs, DFUs, and arterial wounds (P values per log-rank, P < .01, P < .01, P = .05, and P = .01, respectively). However, VLUs did not heal faster than STWs (P value per log-rank, P = .29). As the data did not follow a normal distribution, the medians for each group were presented. The estimated median total treatment duration in patient discharge with CWC was 87, 152, 100, 773, and 170 days in VLUs, non-VLUs, STWs, PUs, and DFUs, respectively. Due to the small sample size (n = 17), a median value for the total treatment duration in patients with CWC in arterial wounds was not calculated, but the estimated mean was 525.44 days.

Wound characteristics
Compared with the VLU group, the non-VLU group was younger (69.72 vs. 61.35 years; P < .01), had a higher proportion of males (OR = 2.26; P < .01), and had a lower proportion of patients with a BMI value greater than or equal to 25 (OR = 0.39; P < .01). The non-VLU group was also less likely to have more than 1 wound (45/144 vs. 78/121; OR = 0.25; P < .01) and reached CWC upon discharge (OR = 0.41; P < .01) (Table). 

Using the group with VLUs as a comparison reference: (1) patients with PUs or DFUs were less likely to be female (P < .05 for both); (2) patients with other wound etiologies were younger (P < .01 for all) and less likely to have more than 1 wound (P < .05 for all); (3) PUs, DFUs, and arterial wounds, but not STWs (P = .16), were less likely to be discharged with CWC (P = .03, P < .01, and P < .01, respectively); (4) STWs were less likely (P = .03; OR = 0.50), while PUs and DFUs were more likely (P = .02 and P = .01; OR = 3.52 and 3.66, respectively), to have a wound duration at initial examination longer than 180 days; (5) patients with STWs, PUs, and arterial wounds, but not DFUs, were less likely to have a BMI greater than or equal to 25 (P = .01, P = .02, P = .01, and P = .54; OR = 0.41, OR = 0.33, OR = 0.23, and  OR = 0.76, respectively); (6) patients with DFUs were more likely to live with others (P < .01; OR = 13.21); (7) pain was more common in STWs (P = .06, not significant) but less common in PUs and arterial wounds (P = .02 and P = .07 [not significant]; OR = 0.32 and OR = 0.45, respectively). No difference was found between the VLU group and any other wound etiologies (non-VLU group as a whole and wounds of different etiologies other than VLUs) with respect to the patients’ marital statuses, number of comorbidities, or treatment durations (P > .05 for all; Table). 

In the present study, the probabilities for patient discharge with CWC before healing plateaus were relatively good (> 80%) for VLUs and STWs. The non-VLU group healed significantly slower than the VLU group (estimated median, 152 vs. 87 days for total treatment duration) and less likely to be discharged with CWC (P < .01; OR = 0.41). Venous leg ulcers are caused by dysfunctional venous valves that normally facilitate blood return from the leg, thus decreasing swelling and risk for wound occurrence. Compression therapy is widely recognized as the standardized intervention for patients with VLUs as it normalizes venous circulation, which is abnormal in patients with VLUs.¹¹ Interestingly, treatment duration and the percentage of patients discharged with CWC did not differ in patients with VLUs and STWs in the present study. This finding indicates physical therapy outpatient wound care resulted in similar probabilities of wound closure and total treatment duration of these 2 etiologies. As for the chronic non-VLU wounds of other etiologies, with the exception of STWs, the results indicate that treatments at the present clinic remain unsatisfactory. One possible explanation may be that patients with VLUs or STWs responded better to electric stimulation than wounds of other etiologies, and electric stimulation facilitates angiogenesis and thus better circulation.¹² 

The probabilities for patient discharge with CWC before healing plateaus were dismally low for PUs and arterial wounds, and mediocre (~52%; Figure 3) for DFUs. The pathophysiology of PUs includes prolonged pressure and/or friction over bony prominences,⁷ but treatment options have been limited to pressure relief and skin protection in traditional wound care practices, which could be difficult, especially for patients with paralysis. Arterial wounds are caused by poor arterial circulation. As a result of the advent of angiography, physicians are able to recanalize middle-sized to large-sized arteries to improve blood circulation. However, microvascular diseases, which are common in patients with arterial wounds, remain a dilemma for clinicians. The chronicity of DFUs is usually due to poor glycemic control.⁸ Diabetic foot ulcers can be difficult to treat as the process of diabetic complications, such as neuropathy, takes years—if not decades—to occur.⁸ Consistent with these aforementioned theories,^7,8 this study demonstrated that longer total treatment durations were required for PUs, DFUs, and arterial wounds, with a relatively low probability to be discharged with CWC. The protocol of care, which currently involves wound care dressings and therapeutic modalities in the outpatient physical therapy wound care clinic, remains unsatisfactory, and more research studies are needed to develop new treatment strategies for these wounds. 

In the present study, the estimated median total treatment duration in patient discharge with CWC was 87, 152, 100, 773, 170 days for VLUs, non-VLUs, STWs, PUs, and DFUs, respectively. Complete wound closure rates with different treatments have been widely reported in the available literature.^13-16 In patients with VLUs treated with multilayer compression bandage, CWC rates were 57% at 2 months¹³ and 83.8% with low molecular weight heparin therapy at 12 months in 1 study.¹³ To the authors’ knowledge, little information regarding wound healing outcomes in outpatients with chronic surgical or traumatic wounds is available in the literature. For PUs, Brewer et al¹⁵ reported the mean treatment durations required for CWC as 21.1 ± 3.7 (n = 26) weeks with conventional care and 10.5 ± 1.3 (n = 30) weeks with an additional arginine-containing supplement. For DFUs, Omar et al¹⁶ found that CWC rates at weeks 8 and 20 were 33.3% and 54%, respectively, with extracorporeal shock wave therapy plus standard wound care and 14.28% and 28.5%, respectively, with standard wound care.¹⁶ Although these numbers in the literature appear to be more positive than the present study, these studies were prospective clinical trials with strict inclusion and exclusion criteria, together with smaller sample sizes^13-16; the present retrospective study reported the results of all-inclusive analyses from an outpatient physical therapy wound care clinic, including patients treated with different dressings and/or modalities. In addition, the total treatment duration in patients with CWC in the present study was usually 1 to 2 weeks longer than the time required for CWC, the actual outcome measure in the aforementioned studies.^13-16

In the present study, patients with VLUs accounted for 45.66% of the total patient population (N = 265), and it was the most common wound diagnosis seen in the study. It has been previously reported that VLUs account for 70% to 90% of all leg ulcers.⁶ As the present study included wounds located in areas other than the leg, the proportion of patients with VLUs in all leg ulcers is expected to be much higher than 45.66% of patients with wounds in general, which included wounds at other body locations. Thus, this study further suggests the high prevalence of VLUs in patients with wounds. Wounds of traumatic or surgical etiology usually heal by primary intention; however, delayed wound healing is not uncommon, especially given the fact that the prevalence of infection ranges from 10% to 30% in secondary intention surgical wound healing.¹⁷ In the present study, STWs were the second most common diagnosis (23.77%) of all patients. Fife et al¹⁸ reported that nonhealing surgical wounds represented the largest category of wounds (20.8%) among hospital-based outpatient wound centers. The present study’s finding of 23.77% supports that STWs are common in outpatient physical therapy wound care clinics, with higher prevalence than that of PUs or DFUs.¹⁸ 

The results of the present study indicate that patients with VLUs tend to be older, female, overweight or obese, and have more than 1 wound. Age typically plays a role in the development of VLUs, as the venous valve function declines as people age.¹⁹ In addition to age, being overweight (BMI ≥ 25) or obese (BMI ≥ 30) appeared to be a risk factor for the development of VLUs in the present study; this is supported by the finding that obesity was related to lower venous peak velocity, mean velocity, velocities amplitude (peak velocity-minimum velocity), and shear stress.²⁰ Sex also may be a confounding factor for the development of VLUs as there are typically more females in the general senior population.²¹

No difference was found between VLUs and wounds of other common etiologies in marital status, education level, and number of comorbidities, indicating that these factors may not be involved in the development of wounds of specific etiologies. Interestingly, in the present study, although etiologies varied, as compared with VLUs, PUs and DFUs are both more likely to be seen in those who are younger, male, and have a wound duration of no less than 180 days but are less likely to reach CWC. While the pathophysiology of PUs and DFUs is understood, current treatments remain limited in both preventing the occurrence and expediting the healing of PUs and DFUs.²² 

In general, understanding the differences between VLUs and wounds of other etiologies in terms of wound healing outcomes and wound characteristics provide valuable information for clinicians with respect to plan of care, helping patients better understand the wound healing process, assisting health care policy makers regarding the extensive treatment duration required for CWC and thus an appropriate structure and allocation of medical resources, and educating insurance companies in creating tailored reimbursement structures for different wound etiologies. 

The present study was based on data captured at 1 outpatient physical therapy wound care clinic. Sample sizes for some specific wound etiologies are small. As conciliation among statistical bias, applicability, and clinical significance, the simplification of wound diagnoses to the predominant wound etiology and treatment duration to the overall length of treatment of the individual patient in the study may create bias. On top of physical therapy wound care, patients in the present study may have received other treatments, including antibiotics and surgical debridement, by the referring physicians. Thus, these results should be interpreted with caution.

This study provided a detailed understanding of wound healing outcomes and of wounds with different etiologies at an outpatient physical therapy wound care clinic. These results may be of significance to clinicians, patients, health care policy makers, and insurance companies. Future research to compare wound healing outcomes and patient characteristics among different settings is warranted. 

Note: The authors would like to thank Drs. Michael Brogan and Corstiaan Brass for their leadership and administrative efforts in the outpatient physical therapy wound care clinic. This outpatient physical therapy wound care clinic was officially closed in early 2017. With much appreciation, the authors would like to thank the clinic staff and patients.

Authors: Kehua Zhou, MD, DPT¹; Leslie Frankish, BS²; and Michael Ross, PT, DHSc, OCS, FAAOMPT³

Affiliations: ¹Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY; ²College of Medicine, Kaohsiung Medical University, Sanmin District, Kaohsiung City, Taiwan; and ³Department of Physical Therapy, Daemen College, Amherst, NY

Correspondence: Kehua Zhou, MD, DPT, 2157 Main Street, Buffalo, NY 14214; kehuazho@buffalo.edu

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