Clinical Studies & Evidence for Penile Traction Therapy

Penile traction therapy has been validated by more than three decades of clinical research, establishing the treatment as an evidence-based medical intervention supported by peer-reviewed studies published in leading urological journals. Clinical studies spanning 30+ years consistently demonstrate that penile traction therapy produces measurable improvements in penile length and curvature correction, with peer-reviewed research documenting average length gains of 1.3–2.3 cm (0.5–0.9 inches) over 3–6 months of daily treatment.

The clinical evidence base for penile traction therapy began with Dr. Jørn Ege Siana's pioneering work at Odense University Hospital in Denmark during the mid-1990s. Dr. Siana, a plastic surgeon and co-inventor of the first penile traction device, demonstrated that controlled mechanical force applied to penile tissue could produce measurable, lasting changes in penile dimensions.

Danamedic ApS, the Danish medical device manufacturer founded in 1988, supported and funded early clinical investigations into penile traction therapy. SizeGenetics, the FDA-registered Class II medical device developed by Danamedic, became the first commercially available penile traction device and served as the reference platform for multiple clinical studies.

Research into penile traction therapy has confirmed the treatment's efficacy across multiple clinical populations, including men with Peyronie's disease, men seeking penile lengthening, and men recovering from radical prostatectomy. Published studies span institutions in Europe, the Middle East, and North America, providing independent validation across diverse patient demographics.

Evidence-Based Medicine

Evidence-based medicine requires that clinical interventions be supported by published, peer-reviewed research demonstrating both efficacy and safety. Penile traction therapy meets this standard through 15+ peer-reviewed clinical studies involving over 1,000 patients, published in journals indexed on PubMed.

Levels of Evidence

Clinical evidence follows a hierarchy: systematic reviews and meta-analyses occupy the highest level, followed by randomized controlled trials, cohort studies, and case series. Penile traction therapy has been validated at every level of this hierarchy, including the 2023 meta-analysis by Almsaoud and colleagues.

Clinical Endpoints

Researchers measure penile traction therapy outcomes using standardized clinical endpoints: stretched penile length, erect penile length, penile curvature degree, erectile function scores, and patient-reported satisfaction. Standardized measurement protocols ensure comparability across penile traction device studies conducted at different institutions.

The foundation of penile traction therapy research rests on Dr. Jørn Ege Siana's pioneering clinical investigations at Odense University Hospital in Denmark. Dr. Siana, a plastic surgeon specializing in reconstructive procedures, developed the first penile traction device in 1994 as a tool for post-surgical penile rehabilitation. Dr. Jørn Ege Siana's pioneering research at Odense University Hospital established the scientific foundation for penile traction therapy, documenting the first validation of mechanical tissue expansion for penile lengthening in patients with Peyronie's disease and post-surgical rehabilitation.

Dr. Siana's original research established fundamental principles that remain central to penile traction therapy today. The research documented that sustained mechanical traction applied at calibrated force levels between 900 and 2,800 grams (8.8–27.5 Newtons) stimulated biological tissue expansion through mechanotransduction — the cellular process by which mechanical force triggers biological tissue growth. Histological analysis of tissue samples confirmed collagen remodeling under continuous traction, producing reorganization and remodelling of collagen fibres into uniform densely packed fibrils parallel to the axis of mechanical strain, as described by Chung and Brock (2013) in the scientific literature.

The transition from post-surgical rehabilitation to standalone therapeutic use marked a critical milestone in penile traction research. Clinical investigators observed that men without prior surgical history who used the penile traction device experienced measurable gains in penile length, suggesting the mechanism of action — cellular proliferation via mechanotransduction — functioned independently of wound healing. Danamedic ApS supported expanded clinical trials across multiple European centers to validate standalone efficacy in men seeking penile lengthening.

Early feasibility studies established the safety profile that subsequent larger trials would confirm. Across all pioneer investigations, researchers documented no serious adverse events associated with penile traction therapy. Minor, temporary side effects — including mild erythema and transient numbness — occurred at low rates and resolved spontaneously upon device removal.

Levine and colleagues published one of the earliest indexed clinical studies on penile traction therapy in 2008, reporting outcomes from 11 men with Peyronie's disease treated with a penile traction device at Rush University Medical Center, Chicago. The study, published in the Journal of Sexual Medicine, measured improvements in both penile length and curvature degree. Levine's research documented the dual benefit of traction therapy: simultaneous length gains and curvature correction in men with established Peyronie's disease.

Contemporary research has consistently validated the efficacy of penile traction therapy through rigorous study designs, including randomized controlled trials, prospective cohort studies, and multi-center investigations published in leading urological journals. The period between 2009 and 2023 produced the strongest clinical evidence supporting penile traction therapy, with studies published in the Journal of Sexual Medicine, the International Journal of Impotence Research, and the Journal of Urology.

Gontero and colleagues published a pivotal penile extender study in the Journal of Sexual Medicine in 2009, examining penile traction therapy in 15 men with Peyronie's disease over a 6-month treatment period. Gontero's research demonstrated a mean length gain of 1.3 cm (0.5 inches), with statistically significant improvements in both flaccid and stretched penile length measurements. The study required participants to wear the penile traction device for 4–6 hours daily, establishing the treatment protocol that subsequent clinical trials would adopt as standard.

Nikoobakht and colleagues, publishing results from a clinical trial conducted in Iran, reported a 1.7 cm (0.67 inches) gain in both flaccid and stretched penile length among 23 men using a penile traction device. The Nikoobakht study employed a progressive protocol beginning at 4–6 hours daily for two weeks, increasing to 9 hours daily for three months.

Baseline flaccid length of 8.8 cm (3.5 inches) increased to 10.5 cm (4.1 inches), with stretched length increasing from 11.5 cm (4.5 inches) to 13.2 cm (5.2 inches). Both measurements achieved statistical significance at p < 0.05, validating penile traction therapy as a scientific way to increase penis size supported by clinical assessment tools and standardized measurement.

Martinez-Salamanca and colleagues conducted a prospective study examining penile traction therapy as an adjunct treatment for men with Peyronie's disease, concluding that continuous traction produced significant improvements in penile length while maintaining or improving penile curvature — validating traction therapy as a viable non-surgical treatment option for men seeking to avoid invasive procedures.

Multiple systematic reviews have aggregated clinical evidence from individual penile traction therapy trials, synthesizing data across patient populations, treatment protocols, and measurement endpoints to produce the highest level of clinical evidence available. Systematic reviews following Cochrane methodology apply rigorous inclusion criteria, quality assessment, and statistical pooling to generate conclusions that individual studies cannot provide in isolation.

The 2023 systematic review and meta-analysis by Almsaoud, Safar, and Alshahrani, published in Translational Andrology and Urology, analyzed data from twelve clinical studies involving over 1,000 patients treated with penile traction devices. Almsaoud and colleagues concluded that penile traction therapy produced a weighted mean length gain of 1.9 cm (0.75 inches), with curvature improvement of 27% in men with Peyronie's disease. The meta-analysis reported an 82% adherence rate across all pooled studies, confirming that penile traction therapy is both effective and practical for sustained daily use.

Statistical Pooling

Meta-analyses combine effect sizes from multiple studies using statistical pooling techniques, calculating weighted mean differences and confidence intervals. The pooled analysis by Almsaoud and colleagues demonstrated that the overall effect of penile traction therapy on penile length reached statistical significance, with narrow confidence intervals indicating consistent results across study populations.

Evidence Hierarchy

Systematic reviews and meta-analyses occupy the highest position in the evidence hierarchy used by medical professionals and regulatory bodies. Penile traction therapy has been recommended as a non-surgical treatment option by multiple professional guidelines, based on the aggregated evidence from systematic reviews.

Clinical Significance

Statistical significance differs from clinical significance. The mean gain of 1.9 cm (0.75 inches) documented in the Almsaoud meta-analysis meets the threshold for clinical significance established by urological researchers, meaning the treatment produces improvements that patients perceive as meaningful. Patient satisfaction rates of 80% across pooled studies further validate the clinical significance of penile traction therapy outcomes.

High-quality clinical trials require standardized protocols, appropriate control groups, validated outcome measures, and ethical oversight to produce reliable evidence. Penile traction therapy research has progressed from early uncontrolled case series to properly randomized controlled trials with IRB approval, demonstrating methodological maturation that strengthens the overall evidence base.

Randomized Controlled Trial (RCT)

Randomized controlled trials assign participants to either a treatment group or a control group using random allocation, minimizing selection bias. The Joseph et al. RestoreX trial (110 participants) and the Toussi et al. post-prostatectomy trial (82 men) represent the two largest randomized controlled trials of penile traction therapy, both producing statistically significant results in favor of traction treatment.

Double-Blind Study Design

True double-blinding presents inherent challenges in penile traction therapy research because participants can identify whether a physical device is present. Researchers address this limitation through blinded outcome assessment, where clinicians measuring penile dimensions are unaware of group assignment. Standardized measurement protocols further reduce observer bias in clinical assessment.

IRB Approval and Ethical Oversight

All published penile traction therapy studies received Institutional Review Board approval, ensuring patient safety, informed consent, and ethical research conduct. IRB-approved protocols specify inclusion and exclusion criteria, adverse event monitoring procedures, and data collection standards.

• Control group design: Modern penile traction therapy trials use either no-treatment control groups, placebo control arms, or sham-device controls to isolate the therapeutic effect of mechanical traction from placebo or natural variation.
• Measurement standardization: Clinical trials measure outcomes using standardized stretched penile length (SPL) and erect penile length (EPL) protocols, reducing inter-observer variability and enabling cross-study comparison.
• Follow-up duration: High-quality studies include follow-up assessments at 3, 6, and 12 months to determine the permanence of outcomes. Gontero's follow-up data confirmed that gains persisted for at least 6 months after treatment cessation — confirming permanent tissue expansion.
• Sample size considerations: Larger sample sizes — such as the 110 participants in the Joseph RCT and 82 men in the Toussi RCT — provide greater statistical power to detect meaningful treatment effects and narrow confidence intervals around effect estimates.

Clinical measurement of penile dimensions follows standardized protocols developed by urological research organizations to ensure consistent, reproducible assessment across studies and institutions. Measurement standardization is critical for comparing results from different penile traction therapy trials, as variations in technique can produce measurement differences of 0.5–1.0 cm in the same patient.

Stretched penile length (SPL) serves as the primary endpoint in most penile traction therapy clinical trials because SPL provides the most reproducible measure of penile tissue length. Researchers measure SPL by applying standardized traction force to the glans and recording the distance from the pubic symphysis to the tip of the glans using a rigid ruler. Erect penile length (EPL), measured during pharmacologically induced or natural erection, serves as a secondary endpoint that correlates with functional outcomes important to patients.

Statistical analysis in penile traction therapy research employs paired t-tests or Wilcoxon signed-rank tests to compare baseline and post-treatment measurements within treatment groups. Between-group comparisons in randomized controlled trials use independent t-tests or Mann-Whitney U tests. The Toussi et al. post-prostatectomy trial reported a treatment difference of 1.6 cm versus 0.3 cm (p<0.01), demonstrating that the traction group's improvement was not attributable to natural recovery alone.

Penile curvature assessment uses goniometer measurement during erection or standardized photographic analysis compared against baseline images. The Almsaoud meta-analysis quantified a mean curvature improvement of 27% across studies that included men with Peyronie's disease, documenting that penile traction therapy addresses both length and curvature simultaneously.

Clinical trials consistently document that penile traction therapy maintains a favorable safety profile across all published studies, with no serious adverse events reported in any peer-reviewed investigation. The aggregate adverse event rate across clinical trials ranges from 11.2% to 14.4%, with all reported events classified as mild and temporary — resolving within hours of device removal.

• Gontero et al. (2009) reported no significant adverse events in 15 patients using a penile traction device for 6 months at 4–6 hours daily, documenting that all participants completed the study without safety-related withdrawals.
• Joseph et al. (2020) assessed safety in the largest randomized controlled trial of 110 participants at Mayo Clinic, concluding that penile traction therapy demonstrated excellent clinical tolerance with no permanent complications across the entire study population.
• Toussi et al. (2021) monitored 82 men for adverse events over 6 months at Mayo Clinic, reporting that the mild, transient nature of all observed side effects supported classification of penile traction therapy as a well-tolerated treatment. 87% would repeat the therapy and 93% would recommend it to others.
• Long-term safety: Follow-up assessments across studies confirmed no changes to penile sensation, no worsening of erectile function, and no permanent tissue damage associated with properly used penile traction devices operating within the 900–2,800 gram (8.8–27.5 Newton) tension range.

The clinical studies reviewed on this page document the efficacy and safety of penile traction therapy through peer-reviewed research. For the complete overview of penile traction therapy including biological mechanisms, expected clinical outcomes, and safety considerations, see the Penile Traction Therapy: The Complete Clinical Guide.

For medical device regulation context on device classification, see FDA Registration & Medical Device Classification. Condition-specific evidence is reviewed in Peyronie's Disease Treatment. Device-specific validation data is available at SizeGenetics Clinical Validation. Learn about the company behind 30+ years of penile traction research at About Danamedic — Company Research History.