Penile compression clamps: A model of the internal mechanical state of penile soft tissues

Experimental testing combined with inverse-FE for mechanical characterisation of penile tissues

Erectile dysfunction (ED) predominantly affects men in their 40-70s and can lead to a poor quality of life. One option for ED treatment is surgical implantation of an inflatable penile prosthesis (IPP). However, they can be associated with negative outcomes including infection, migration or fibrosis. To improve outcomes, the interaction between the IPP device and surrounding tissues needs further investigation and this could be achieved using pre-clinical testbeds, but they need to be informed by extensive tissue testing. In this study, an experimental approach is adopted to characterise the mechanics of horse penile tissue and establish a testing protocol for penile tissue. The whole penis segments were tested in plate compression tests to obtain whole penis behaviour which is necessary for validation of a pre-clinical testbed, whilst tensile and compression tests were performed on individual penile tissues, namely corpus cavernosa and tunica albuginea. The second part of the paper deals with the development of a computational model employing an inverse finite element approach to estimate the material parameters of each tissue layer. These material parameters are in a good agreement with the experimental results obtained from the individual tissue layers and whole organ tissue tests. This paper presents the first study proposing realistic nonlinear elastic material parameters for penile tissues and offers a validated testbed for IPPs. STATEMENT OF SIGNIFICANCE: Erectile Dysfunction (ED) affects over half the male population aged 40-70 potentially leading to a poor quality of life. Patients not responding to conventional treatments of ED, are advised to use penile prostheses which can create an erection using implanted inflatable cylinders. A significant drawback of such prostheses, however, is the substantial tissue damage they can induce during their usage. Preclinical testbeds, including computational and bench-top models, could offer an efficient means of improving device designs to mitigate this damage but such testbeds require extensive knowledge of penile tissue properties. In this study, the authors determine penile tissue mechanics and apply an inverse FE approach to characterise the penile material properties required to validate preclinical models of the penis.

Patients experience with the use of a penile clamp in post-prostatectomy incontinence - a prospective pilot study

OBJECTIVES

The aim of this study was to assess the efficacy of a penile clamp in managing urinary incontinence (UI) and its impact on perceived quality of life (QoL) amongst post-prostatectomy patients.

MATERIAL AND METHODS

A prospective pilot study was conducted including patients with post-prostatectomy UI treated with a penile clamp. Inclusion criteria consisted of UI after radical prostatectomy, good hand function, full cognitive function and a minimum penile length of 3 cm and a circumference of 5 cm. An appropriately sized penile clamp was selected during the first visit, and patients were given instructions on how to use it. The first follow-up was a scheduled phone call 1 week after the initial visit. Formal evaluations were performed prior to use of the penile clamp and again after 3 months of usage. These consisted of weighing pads during the daytime with evaluation of leakage, International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF), incontinence-QoL (I-QoL) and a questionnaire specific for the penile clamp.

RESULTS

There were 22 patients included, and two were excluded due to reduced hand function and surgery before the study endpoint. The results showed a significant median reduction of urinary leakage of 57% at rest and 58% during physical activity. One complication was observed, as one patient developed a pinching ulcer, after extensive usage. ICIQ-SF showed an increase of 6% for the included patients (n = 20). Ten patients were satisfied with the clamp, and 15 would recommend the clamp to others.

CONCLUSION

The penile clamp shows promising results in reducing leakage with minimal risks of complications. It can be used as a treatment for patients awaiting surgery. However, patient selection is important regarding hand function, cognitive function and the penile anatomy.

Development of in silico models to guide the experimental characterisation of penile tissue and inform surgical treatment of erectile dysfunction

This paper presents a computational study to investigate the mechanical properties of human penile tissues. Different experimental testing regimes, namely indentation and plate-compression tests, are compared to establish the most suitable testing regime for establishing the mechanical properties of the different penile tissues. An idealised MRI-based geometry of the penis, containing different tissue layers, is simulated using the finite element (FE) method to enable realistic predictions of the deformation of the penis. Unlike the linear elastic models used in the literature to-date, hyperelastic isotropic/anisotropic material models are used to capture material nonlinearity and anisotropy. The influence of material properties, morphological variations, material nonlinearity and anisotropy are investigated. Moreover, the implantation of an inflatable penile prosthesis (IPP) is simulated to assess the effects of the implantation procedure, material nonlinearity, and anisotropy on tissue stresses. The results indicate that the interior layers of the penis do not affect the overall stiffness of the penis in the indentation test, while the plate-compression test is able to capture the effects of these layers. Tunica Albuginea (TA) is found to have the most significant contribution to the total stiffness of the penis under load. It can also be observed that buckling occurs in the septum of the penis during the compression tests, and different morphologies dictate different compressive behaviours. There is a clear need for future experimental studies on penile tissues given the lack of relevant test data in the literature. Based on this study, plate-compression testing would offer the most insightful experimental data for such tissue characterisation.

Utility of a penile compression device for the quality of life in male patients with urinary incontinence after prostatectomy (the MORE study): a randomized prospective study

OBJECTIVES

To verify the effects of penile clamping on the degree of stress urinary incontinence and quality of life in post-radical prostatectomy patients.

RESULTS

Thirty-seven patients suffering from stress urinary incontinence after undergoing radical prostatectomy were enrolled. A total of 19 and 18 patients were analyzed in the non-clamp and clamp groups, respectively. The mean ages of the patients in non-clamp and clamp groups were 68.3 ± 7.1 years and 71.2 ± 4.8 years, respectively; the mean time after radical prostatectomy was 28.9 ± 44.0 months and 26.2 ± 39.0 months, respectively. The penile clamp used was the CLAMPMED® (URINE CONTROL CLAMP) size M (MURANAKA MEDICAL INSTRUMENTS Co., Ltd.). Specific urinary care pads (Sawayaka Pad for Men, Small Quantity®, Unicharm Corporation), were provided; the average daily usage was monitored for four weeks. The quality of life was evaluated using the King's Health Questionnaire. The average daily use of urinary care pads was significantly reduced in the clamp group than in the non-clamp group (-0.83 ± 1.51 vs. -0.16 ± 0.69, P = 0.0071). King's Health Questionnaire scores did not change significantly in either group. Wearing the CLAMPMED® reduced the amount of urinary incontinence but did not improve the quality of life.

TRIAL REGISTRATION

The Japan Registry of Clinical Trials (jRCT1052230083). Registered 2 August, 2023.

The mechanobiology theory of the development of medical device-related pressure ulcers revealed through a cell-scale computational modeling framework

Pressure ulcers are localized sites of tissue damage which form due to the continuous exposure of skin and underlying soft tissues to sustained mechanical loading, by bodyweight forces or because a body site is in prolonged contact with an interfacing object. The latter is the common cause for the specific sub-class of pressure ulcers termed ‘medical device-related pressure ulcers’, where the injury is known to have been caused by a medical device applied for a diagnostic or therapeutic purpose. Etiological research has established three key contributors to pressure ulcer formation, namely direct cell and tissue deformation, inflammatory edema and ischemic damage which are typically activated sequentially to fuel the injury spiral. Here, we visualize and analyze the above etiological mechanism using a new cell-scale modeling framework. Specifically, we consider here the deformation-inflicted and inflammatory contributors to the damage progression in a medical device-related pressure ulcer scenario, forming under a continuous positive airway pressure ventilation mask at the microarchitecture of the nasal bridge. We demonstrate the detrimental effects of exposure to high-level continuous external strains, which causes deformation-inflicted cell damage almost immediately. This in turn induces localized edema, which exacerbates the cell-scale mechanical loading state and thereby progresses cell damage further in a nonlinear, escalating pattern. The cell-scale quantitative description of the damage cascade provided here is important not only from a basic science perspective, but also for creating awareness among clinicians as well as industry and regulators with regards to the need for improving the design of skin-contacting medical devices.

Qualitative analysis of Amazon customer reviews of penile clamps for male urinary incontinence

AIMS

Penile clamps offer an alternative to manage male urinary incontinence in patients who are unfit for surgery. Patient experience with penile clamps is poorly understood. Our study elucidates patient opinions on commercially available penile clamps and the factors that associate with favorable and unfavorable opinions.

METHODS

We collected Amazon reviews of all penile clamps marketed for male urinary incontinence from November 2011 to January 2020 and qualitatively assessed the overall sentiment towards penile clamps, key praises and key complaints. Covariates such as designated Amazon star rating were further explored for association with coding patterns.

RESULTS

Amazon reviews of penile clamps were found to be more positive (n = 425) in overall sentiment than negative (n = 294). The most frequent praise was effective incontinence control (n = 334) and the most frequent complaint was bad design or material (n = 166). The majority of reviews were for lower priced penile clamps, had higher Amazon star ratings, were written for Wiesner-produced clamps, and were written more recently (i.e., 2015-2020). Penile clamps with higher Amazon star ratings were more often coded positive and with a praise compared to lower rated penile clamps.

CONCLUSIONS

Penile clamps are seen favorably by users as an effective treatment modality for male urinary incontinence. User reviews suggest opportunities for improvement in penile clamp design. The most frequently reviewed clamp seen positively is the Wiesner Incontinence Clamp Penile Clamp whereas the most frequently reviewed clamp seen negatively is the Pacey Cuff Male Incontinence Device.

Magnetic resonance imaging to estimate tissue deformations during penile clamp application: A case series

Background:

Penile clamps provide a means of preventing urinary incontinence in males following radical prostatectomy. In order for the devices to function, significant mechanical loads need to be applied to the penile tissues to close the urethra. However, such loads have the potential to cause damage to the vulnerable skin and underlying soft tissues. Accordingly, the study aimed to estimate the magnitudes of tissue deformations resulting from penile clamp application in three individual cases.

Methods:

Three individuals were recruited who currently use penile clamps to manage urinary incontinence following radical prostatectomy. Magnetic resonance images (MRI) of the penis were taken to produce a series of high contrast coronal and sagittal images both before and during the application of two commercially available clamps, modified for MRI compatibility. Tissue thickness measurements were estimated with the clamps in-situ and normalised to the unloaded baseline state.

Results:

The estimated magnitude of tissue deformations resulting from clamp application ranged between 68% and 84%. There were minimal differences in these deformations between the clamp designs, both of which appeared effective in closing the urethra. Local stress concentrations were observed in the tissues, which were deformed around the shape of the clamp.

Conclusions:

MRI enabled quantification of local tissue deformation during penile clamp application. The results revealed that clamps created large tissue deformations in all three cases, regardless of design. This information could inform the development of new clamp designs and materials to minimise the potential for tissue damage.

Level of evidence:

4

Tissue response to applied loading using different designs of penile compression clamps

Background: Penile compression devices (PCD) or clamps are applied to compress the urethra and prevent urinary incontinence (UI). PCDs are more secure and less likely to leak than pads, allowing men the opportunity to participate in short-term, vigorous activities. However, they are uncomfortable, can cause pressure ulcers (PU) and affect penile blood flow. No objective assessment of tissue health has been undertaken to assess and compare different PCD designs and to provide guidance on safe use.

Objective: This study was designed to evaluate existing PCDs in terms of their physiological response and potential for pressure-induced injury.

Design, setting and participants: Six men with post-prostatectomy UI tested four selected PCDs at effective pressures, in a random order, in a controlled laboratory setting.

Outcome measurements and statistical analysis: Using objective methods for assessing skin injury, PCDs were measured in situ for their effects on circulatory impedance, interface pressures and inflammatory response.

Results and limitations: There was evidence for PCD-induced circulatory impedance in most test conditions. Interface pressures varied considerably between both PCDs and participants, with a mean value of 137.4±69.7 mmHg. In some cases, penile skin was noted to be sensitive to loading with elevated concentration of the cytokine IL-1α after 10 mins wear, indicating an inflammatory response. IL-1α levels were restored to baseline 40 mins following PCD removal.

Conclusion: Skin health measures indicated tissue and blood flow compromise during the 50 mins of testing using all PCDs. Although there was an elevation in pro-inflammatory cytokines, PCDs did not cause sustained irritation and skin health measures recovered 40 mins after PCD removal. This research indicates that application of a clamp for one hour with an equal clamp free time before reapplication is likely to be safe. Longer periods are often recommended by manufacturers but have yet to be tested.

Bioengineering considerations in the prevention of medical device-related pressure ulcers

BACKGROUND

In recent years, it has become increasingly apparent that medical device-related pressure ulcers represent a significant burden to both patients and healthcare providers. Medical devices can cause damage in a variety of patients from neonates to community based adults. To date, devices have typically incorporated generic designs with stiff polymer materials, which impinge on vulnerable soft tissues. As a result, medical devices that interact with the skin and underlying soft tissues can cause significant deformations due to high interface pressures caused by strapping or body weight.

METHODS

This review provides a detailed analysis of the latest bioengineering tools to assess device related skin and soft tissue damage and future perspectives on the prevention of these chronic wounds. This includes measurement at the device-skin interface, imaging deformed tissues, and the early detection of damage through biochemical and biophysical marker detection. In addition, we assess the potential of computational modelling to provide a means for device design optimisation and material selection.

INTERPRETATION

Future collaboration between academics, industrialists and clinicians should provide the basis to improve medical device design and prevent the formation of these potentially life altering wounds. Ensuring clinicians report devices that cause pressure ulcers to regulatory agencies will provide the opportunity to identify and improve devices, which are not fit for purpose.