Hard-Flaccid Syndrome: A Systematic Review of Aetiopathophysiology, Clinical Presentation and Management
Only 8 studies exist on hard-flaccid syndrome — most are case reports, leaving diagnosis and treatment without any established guidelines.
Journal: International Journal of Impotence Research | Published: 2025-07-07 | Type: Systematic Review | PMID:40624184Authors: Pang KH (University College London), Feng J, Zhang Y (Sun Yat-sen University Third Affiliated Hospital)
Funding/COI: Funding not listed; authors declare no competing interests.
Summary
Hard-flaccid syndrome (HFS) — a persistent semi-rigid penis in the flaccid state, often with perineal pain, urinary symptoms, and psychological distress — has an almost nonexistent evidence base. A PROSPERO-registered systematic review following PRISMA 2020 guidelines found only 8 eligible studies across Medline, Embase, and Cochrane, covering roughly 119 patients in total. There are no agreed diagnostic criteria, no validated assessment tools, and no controlled treatment trials.
Claims
Only 8 studies met inclusion criteria: 2 retrospective studies, 1 case series (4 patients), and 5 case reports — 3 of the 8 were congress abstracts, not peer-reviewed publications
The largest cohort is Sullivan et al.'s congress abstract reporting 88 patients (mean age 28, SD 12), of whom 75% had depression or anxiety; neurology was reportedly normal in all
Patient ages across studies ranged from 16–42 years; symptom duration ranged from 2 days to 4 years
All patients for whom a cause was reported had a history of some form of physical trauma: aggressive masturbation, jelqing, intense sexual intercourse, lumbar disc prolapse, or penile skin injury
Goldstein et al.'s congress abstract (n=21) found 38% had low back pain and lower extremity sciatica, with 76% showing lumbosacral annular tears on imaging — suggesting a possible spinal mechanism in a subset
Reported treatments include PDE5 inhibitors, anxiolytics, low-intensity shockwave therapy, pelvic floor physical therapy, spinal surgery, and biopsychosocial therapy — none evaluated in controlled trials
No study performed a quantitative synthesis; heterogeneity was too high for meta-analysis
Study Quality
The PRISMA-compliant search covered 2018–April 2025 (HFS was first described around 2018). The initial 51 articles were screened down to 8 eligible studies by two independent reviewers using PICOS criteria, with disagreements resolved by the senior author. Risk of bias was assessed using the JBI Critical Appraisal Checklist. By the authors' own assessment, most included studies carry high risk of bias — not because of poor execution, but because case reports and conference abstracts are structurally incapable of supporting causal inference or generalizability.
The total patient count looks like ~119, but that figure is dominated by two congress abstracts (n=88 and n=21) that have not been through peer review. The remaining peer-reviewed studies cover approximately 10 patients combined.
Red Flags
Three of the eight included studies are congress abstracts — no peer review, no full methodology available, no way to verify claims
The largest single dataset (n=88) comes from one of those congress abstracts; stripping it out leaves the evidence base in single digits
No diagnostic criteria exist, meaning different studies may be capturing different conditions under the same label
Symptom reporting was unstandardized across all studies, making any comparison unreliable
The hypothesized mechanism — trauma triggering a neurovascular-inflammatory cascade, worsened by psychological feedback — is plausible but entirely speculative; no mechanistic or histological studies exist
Funding source not disclosed; institutional affiliations span three countries with no explanation of collaboration context
Strengths
PROSPERO registration and PRISMA 2020 adherence give the review procedural legitimacy
Dual independent screening and JBI bias assessment applied consistently
Authors are transparent about the field's limitations — they do not oversell the evidence
Comprehensive symptom comparison table (Table 4) against Gul et al.'s clinical features list provides a useful framework for future standardization
The review correctly identifies the absence of diagnostic criteria as the field's primary obstacle
Verdict
This paper is doing honest work in a field that barely exists. As a systematic review, it is methodologically sound — the PRISMA process was followed, bias was assessed, limitations were stated plainly. The problem is not the review; it's what the review found. Eight studies, most of them case reports or unreviewed abstracts, covering a condition that affects young men and has no agreed definition, no diagnostic test, and no controlled treatment data. The paper's primary value is mapping the void: it establishes what is not known, which is nearly everything. Anyone citing this review as evidence that a particular treatment works for HFS has misread it. The verdict on the paper is favorable; the verdict on the field is that it needs controlled trials, a validated case definition, and a patient registry before any clinical conclusions are possible.